All glacigenic deposits mapped in NO76NW are assigned to the Mearns Glacigenic Subgroup of the Caledonia Glacigenic Group.
"This subgroup, which is equivalent to the Mearns Drift Group of Merritt et al.,, comprises Mill of Forest Till, Ury Silts, and Drumlithie Sand And Gravel formations."
The highly irregular middle zone is underlain by Permian and Triassic rocks: the Permian strata include Upper Permian Zechstein sedimentary rocks that locally crop out in the study area.
"Abbreviations: FHA, St. Andrew 's Bay Member: SBB, St. Abbs Formation: WBA, Wee Bankie Formation."
Sedimentary rocks of Silurian age occur in a series of inliers along the southern margin of the Midland Valley.
"The inliers afford some insight into the development of early Phanerozoic basins in northern Britain but the geological setting of the inliers, in terms of the relative positions of lithospheric plates in Silurian times, remains conjectural."
"The inliers lie on opposite sides of the NE-trending Kerse Loch Fault which clearly was active in late - Silurian times, with an effective downthrow towards the north."
It has been suggested that in Lower Palaeozoic times the Midland Valley and Southern Uplands depositional basins lay some distance apart and were juxtaposed by sinistral strike-slip fault movements associated with the oblique collision in late - Silurian times of the East Avalonian and Laurentian plates.
"The stratigraphy was greatly elaborated by Jennings who named many new formations which he placed in three groups, in ascending order: Priesthill, Waterhead and Dungavel groups."
"The lower part of the sequence of greywackes and siltstones formerly assigned to the Patrick Burn Formation is referred instead to the newly recognised Ponesk Burn Formation, on the grounds that derived faunas found in greywacke beds in the latter include brachiopods, trilobites and crinoids, indicative of an open sea marine environment, whereas in the former the derived faunas in the greywacke beds are mainly molluscan and of low diversity -- typical of a restricted marine basin."
"The boundaries of the Castle, Kip Burn and Blaeberry formations have also been redefined to take account of the new fossil evidence and a reassessment of the faulting that affects the rocks around the Logan Reservoir."
"At the top of the group, the Passage Formation has been eliminated and the predominantly argillaceous strata in its lower part assigned to the Dunside Formation."
"The fauna differs significantly from the mainly molluscan, low-diversity fauna found in the overlying Patrick Burn Formation."
"The strata in this formation are generally similar to those in the Ponesk Burn Formation, consisting of series of turbiditic flow units with intercalations, up to 20m thick, of grey siltstone and silty mudstone with laminae of carbonaceous siltstone."
Siltstone beds with the characteristic fauna including Ceratiocaris occur throughout the Patrick Burn Formation.
"As a result of the large fault which forms the southern margin of its outcrop, little more than 100m of strata in the upper part of the formation are present at Priesthill."
"The distinctive massive siltstone beds, which are interbedded with bedded grey siltstones, occur through a thickness of only about 25 to 30m, but the formation is widespread and maintains its stratigraphical position in relation to the succeeding Kip Burn Formation."
"Siltstones in the Eaglin Burn -LSB- NS 760 349 -RSB-, placed in the Castle Formation by Jennings, are now considered part of the Blaeberry Formation on faunal evidence obtained during the resurvey."
The base of the formation is seen at Shank 's Castle where carbonaceous siltstones pass up by rapid transition from the massive siltstones and mudstones of the Castle Formation.
"It follows that, according to the definition of its boundaries proposed by Jennings and adopted here, the Kip Burn Formation includes only the uppermost part of the ` Ceratiocaris Beds ' of Peach and Horne, the remainder lying within the upper part of the Patrick Burn Formation."
"The strata in its upper part are well seen in the Blaeberry Burn section -LSB- NS 736 356 -RSB-, which is terminated to the east by a fault which throws down strata of the Blaeberry Formation."
"The outcrop of the formation, displaced by numerous faults, can be traced eastwards to the Logan Water, and south-westwards by Kip Burn, Leaze Burn, Patrick Burn and the streams above Waterhead to those on the lower slopes of Middlefield Law, including Lamon Burn."
"The strata in the lower part of the succession are bioturbated and fossiliferous, the fauna resembling that in the underlying Blaeberry Formation."
This assemblage is comparable to that in the Parishholm Conglomerate of the Hagshaw Hills Inlier.
"However, the contact of the formation with the underlying Birkenhead Sandstone is nowhere exposed."
"The Monument Formation is also exposed in ditches on the eastern slopes of Middlefield Law and, together with the Dippal Burn Formation, is involved in a complicated fault structure in the headwaters of the Kip Burn."
These beds are similar in lithology and fauna to the Dippal Burn Formation and prior to the work of Jennings the two sequences were regarded as the same.
Near the base of the sequence are grey and red variegated mudstones which are transitional from the red Monument Formation beneath.
This formation shows a return of the conditions which existed while the Monument Formation was laid down.
Jennings considered the formation to be only 8m thick where exposed in the Birkenhead Burn -LSB- NS 767 360 -RSB- but its contact with the Middlefield Conglomerate to the east is faulted.
"The Plewland Sandstone is overlain with apparent conformity by the Greywacke Conglomerate, which is arbitrarily taken as the base of the Lower Devonian."
A stratigraphy for the Silurian rocks was first proposed by Peach and Horne.
"The greatest thickness is seen in the Ree Burn, where about 125m of strata crop out between the fault and the base of the Ree Burn Formation."
The Smithy Burn Siltstone is poorly fossiliferous.
The greywacke member has also been recognised also in the Monks Water and in the Smithy Burn.
"The best exposures of the formation are at the type section in Ree Burn -LSB- NS 763 281 to NS 761 276 -RSB-, south of Parish Holm, where a transitional boundary with the underlying Smithy Burn Siltstone is seen."
"As defined by Rolfe, this group consisted of four formations -- in upwards sequence, the Douglas Water Arenite, the Dovestone Redbeds, the Fish Bed Formation and the Gully Redbeds -- all of terrestrial origin."
It is proposed here that the definition of the group be altered so as to include the Parishholm Conglomerate at its base.
The Glenbuck Group then becomes the approximate equivalent of the Waterhead Group of the Lesmahagow Inlier.
"The Parishholm Conglomerate succeeds the Ree Burn Formation without apparent angular unconformity, although there is a sharp lithological contrast between the two formations and comparison with the succession in the Lesmahagow Inlier suggests that the boundary marks a major non-sequence."
The Douglas Water Arenite succeeds the Parishholm Conglomerate with apparent conformity.
The Dovestone Red Beds follow the Douglas Water Arenite without a noticeable break.
The formation is exposed at the east end of Glenbuck Loch -LSB- NS 762 284 -RSB- and in the Shiel Burn tributary of the Monks Water and there are small exposures of the formation in the Douglas Water north-west of Urit Hill.
"However, an assemblage of miospores recently collected from exposures at Glenbuck Loch is said to indicate an earliest Wenlock age for the strata."
The fish bed probably correlates with the Dippal Burn Fish Bed of Lesmahagow.
The Gully Red Beds is the topmost subdivision of the Glenbuck Group and indicates a return to conditions similar to those which existed during deposition of the Dovestone Red Beds.
"The exposures in the Monks Water consist of fine-grained red sandstone and dark red-brown silty mudstone which is finely micaceous, its colour being altered by reduction to pale grey-green in places."
"In order to achieve a consistent approach to the stratigraphy of the Silurian inliers, it is proposed that the youngest formations, the Hareshaw Conglomerate and Quarry Arenite, be assigned to a new group, namely the Monks Water Group."
The Hareshaw Conglomerate is considered to be generally equivalent to the Middlefield Conglomerate of the Lesmahagow Inlier.
"The contact with the underlying Gully Red Beds is nowhere exposed but, as only a short distance separates exposures of the two formations, an abrupt lithological change is indicated."
"On the northern limb of the Hagshaw Hills Anticline, where the formation is estimated to be 65m to 70m thick, there are exposures in the Douglas Water, north-west of Dovestone Rig -LSB- NS 753 273 -RSB-, at the east end of Glenbuck Loch -LSB- NS 762 286 -RSB-, in an unnamed right-hand tributary -LSB- NS 771 291 -RSB- of the Monks Water, and in the Podowrin and Smithy burns."
The Quarry Arenite overlies the Hareshaw Conglomerate.
and is considered to be generally equivalent to the Plewland Sandstone of the Lesmahagow Inlier.
Fossil assemblages recovered from the two Silurian inliers in the Hamilton district differ somewhat and they are therefore described separately.
It would appear that the faunas in the lower part of the succession in the Hagshaw Hills Inlier are more closely allied to those of the Girvan and the Pentland Hills areas than are those of the Ponesk and Patrick Burn Formations of the Lesmahagow Inlier.
This is similar to the assemblage described from the Knockgardner Formation of the Girvan area age for the formation and considered the fauna to be characteristic of deposition under fairly shallow marine conditions.
Recent work on the graptolite faunas of the Blair Shale Formation which underlies the Knockgardner Formation at Girvan suggests that this too may be of earliest Wenlock rather than late Llandovery age.
"It thus remains unclear whether the oldest known fossiliferous rocks in the Lesmahagow Inlier are of late Telychian or early Sheinwoodian age, no graptolites having, as yet, been found."
"The fauna is distinguished from that previously described by a greater presence of benthonic elements, although the brachiopods still suggest a source in which fairly shallow-water marine conditions prevailed as compared to the constricted marine environment indicated by the mainly molluscan fauna found in the greywacke beds of the succeeding Patrick Burn Formation."
The fauna contains elements in common with the fauna described by Liljedahl from rocks of Homerian age in Gotland.
Turner considered that the thelodont fish from the upper part of the formation were of lower Wenlock age.
"Fish-bearing finely laminated siltstones and mudstones, similar to those in the Dippal Burn Formation, are associated with greenish mudstones containing indeterminate plant debris, possibly algal."
"Richardson and Ford, quoted by Selden and White, suggest that miospores from the overlying Logan Formation are no older than late Ludlow in age."
Turner suggested that the thelodont fishes from the Dippal Burn and Slot Burn formations were of late Wenlock to early Ludlow age.
No biostratigraphically useful material has been recovered from Dungavel Group strata.
If correctly determined M. spiralis would suggest a late Telychian age.
The trilobite fauna bears a closer resemblance to that from the Pentland Hills and from the Knockgardner Formation of Girvan than does the fauna of the Ponesk Formation.
"The species occurs in rocks ranging in age from the crenulata Biozone to the centrifugus Biozone, thus spanning the Llandovery to early Wenlock interval, similar to that suggested by the non-graptolitic faunas."
"The middle part of the formation is characterised by beds of thinly laminated siltstone with calcareous nodules containing Ceratiocaris papilio, similar to the beds in the upper part of the Patrick Burn Formation."
"However, the general aspect of the flora and fauna more closely resembles that of the Slot Burn horizon."
"Wellman and Richardson also examined material from this and nearby localities and concluded that the plant assemblages obtained were of earliest Sheinwoodian to latest Sheinwoodian or Homerian age, similar to those from the Dippal Burn and Slot Burn formations of the Lesmahagow Inlier."
The successions in all the Midland Valley Silurian inliers reflect a passage from a wholly marine to a terrestrial environment.
"In the Hagshaw Hills the transition appears abrupt because there is a large hiatus in the sequence, there being no representatives of the strata of the Patrick Burn to Leaze formations inclusive."
"The oldest sedimentary rocks of Silurian age in the district are the massive or poorly laminated, somewhat carbonaceous or pyritous, argillaceous rocks of the Smithy Burn Siltstone of the Hagshaw Hills Inlier."
Conditions were significantly different while the succeeding Ree Burn Formation of the Hagshaw Hills Inlier was laid down.
There is a gap in the succession above the Ree Burn Formation in the Hagshaw Hills Inlier.
"In the Lesmahagow Inlier, however, the rocks of the Ponesk Burn Formation, which bear a close similarity to those of the Ree Burn Formation, are succeeded by the Patrick Burn Formation the greywacke component of which contains a low diversity, mainly molluscan fauna."
"During deposition of the Kip Burn Formation, greywacke deposition no longer reached the Lesmahagow area, perhaps because of a failure of the sediment supply, and only carbonaceous mudstones and siltstones were laid down in quiet-water conditions in a greatly constricted basin."
"Subsequently, water depths decreased and, during Blaeberry Formation times, mud and silt were laid down, possibly in the distal parts of deltas."
"The salinity was less than fully marine as is indicated by a fauna of Lingula, ostracods and molluscs analogous to that found in the Ballagan Formation of the Lower Carboniferous."
"As the deltas advanced into the basin, fluviatile deposits appear in the sequence for the first time, represented by the cross-bedded sandstones with rip-up clasts of mudstone in the upper part of the Dunside Formation."
"By the close of the Dunside Formation, silting up of the basin in the Lesmahagow area was complete and the red-brown sandstones and siltstones of the Leaze Formation were laid down in the channels and floodplains of rivers, which were probably sustained by a low to moderate, strongly seasonal rainfall."
"The abrupt lithological change that occurs at the base of the Birkenhead Sandstone in the Lesmahagow area probably reflects a non-sequence which is not, however, as marked as that which preceded deposition of its supposed equivalent in the Hagshaw Hills Inlier, that is, the Parishholm Conglomerate."
"The two inliers occur on opposite sides of the NE-trending Kerse Loch Fault and it seems likely that this structure, which had a major effect on sedimentation during the Carboniferous period, was active during the Lower Palaeozoic."
The beds of laminated grey-green and dark grey mudstone and siltstone in the lower parts of the Dippal Burn and Slot Burn formations of the Lesmahagow Inlier and the Fish Bed Formation of the Hagshaw Hills Inlier were laid down while water depths were at their greatest.
The deposition of conglomerates and pebbly sandstones in the basal parts of the Dungavel Group of the Lesmahagow Inlier and the Monks Water Group of the Hagshaw Hills Inlier marks a significant change in environmental conditions.
"The stratigraphical classification adopted, comprising in ascending sequence the Greywacke Conglomerate, the Swanshaw Formation and the Duneaton Volcanic Formation, is that proposed by Smith to the south."
"Tectonic activity accompanied by uplift during the Middle Devonian period meant that either no deposits of this age were laid down within the Midland Valley or any such deposits, as well as most or locally all of the Lower Devonian rocks, were removed by erosion."
"As a result of regional subsidence, sedimentation resumed within this valley during Upper Devonian times but did not extend into the Hamilton district."
The conglomerate rests upon an eroded surface which can be seen cutting across beds of the underlying Quarry Arenite.
This subdivision includes the strata overlying the Greywacke Conglomerate and below the thin development of lavas and volcaniclastic rocks seen in tributaries of the Wood Burn -LSB- NS 615 293 -RSB-.
"A fault following the course of the burn, throws down lavas of the Clyde Plateau Volcanic Formation to the west."
"The district includes parts of three coal basins, namely the Central, Douglas and Muirkirk coalfields, each with its own stratigraphy and local coal seam names."
"As a result of late - Devonian uplift and erosion no rocks of Upper Devonian age exist in the district and the oldest Carboniferous strata, which are placed in the Inverclyde Group, rest unconformably on Lower Devonian or older rocks."
"The most widespread of these constitute marker horizons and have been used in the subdivision of the sequence with the bases of the Hurlet Limestone and the Lowstone Marine Band marking the bases of the Clackmannan Group and Coal Measures Group, respectively."
"In the western Midland Valley, the group contains three formations: in upwards succession, the Kinnesswood Formation, the Ballagan Formation and the Clyde Sandstone Formation."
"The known occurrences of Inverclyde Group strata are entirely in the south, where there are outcrops around Middlefield, along the northern margin of the Carboniferous outcrop at Glenbuck, and along the western edge of the Douglas Coalfield between Wedder Hill and North Bankend where the thickest and most complete sequence lies in the area around Burnside."
"North of the fault, in the area around Strathaven and Kirkmuirhill, strata of the group are entirely absent and rocks of the Strathclyde Group rest directly on the Lower Devonian."
"The present distribution of the Inverclyde Group in the district Figure 4is attributed to mid - Dinantian earth movements, involving northerly upthrow on elements in the Kerse Loch Fault zone, followed by erosion which, at least in the Strathaven-Kirkmuirhill area, eliminated the entire group."
"The Kinnesswood Formation, which was previously regarded as part of the Upper Old Red Sandstone and may be partly of Upper Devonian age, is present throughout the Inverclyde Group outcrop."
The Ballagan Formation is developed in the Middlefield area but the sequence here does not extend up to the Clyde Sandstone Formation.
"In Dalfram No. 2 Borehole, sited about 2km to the south of the district, grey shales and cementstones of the Ballagan Formation appeared to be directly overlain by a sequence of ash and agglomerate which is presumed to belong to the Strathclyde Group."
There are exposures of the Ballagan Formation but the presence of the Clyde Sandstone Formation can not be confirmed at outcrop.
"In the area east of North Bankend, where there are good exposures of the Kinnesswood Formation, there is no evidence which confirms or denies the presence of the Ballagan or Clyde Sandstone formations."
Its base is nowhere exposed but is taken at the unconformable junction with rocks of Lower Devonian or Silurian age.
"The thickest exposed sequence of the Kinnesswood Formation is in the Back Burn -LSB- NS 667 294 -RSB-, about 1200m west of Middlefield."
"Throughout this distance, the calcrete-bearing sandstones are overlain by strata of the Ballagan Formation."
"The Burnside Borehole, a little distance to the north-east, was terminated in strata of the Ballagan Formation but, as there is no known locality in Scotland where this formation is not underlain by the Kinnesswood Formation, the presence here of calcrete-bearing sandstones can be assumed."
The base of the formation is transitional from the underlying Kinnesswood Formation and is taken at the base of the lowest bed of grey mudstone.
"The Strathclyde Group comprises, in upwards succession, the Clyde Plateau Volcanic Formation, the Kirkwood Formation and the Lawmuir Formation Figure 5."
"Conversely, the Lawmuir Formation tends to be thicker where volcanic rocks are not present, as around the western margin of the Douglas Coalfield."
"The base of the formation is seen, however, in the smaller outcrop east of Sandford, where the lavas rest unconformably on Lower Devonian rocks."
"The Clyde Plateau Volcanic Formation is thinner east of the fault zone, and continues to thin eastwards until it is eventually overlapped by strata of the Lawmuir Formation, which accordingly rest upon the Lower Devonian."
Variations in thickness of the Namurian sedimentary formations across the line of the Inchgotrick Fault in Ayrshire have been attributed to contemporaneous movements on the fault.
The rapid south-eastwards thinning of the Clyde Plateau Volcanic Formation around Sandford suggests that movements on the fault-line in Dinantian times may have generated a topographical high which restricted the spread of the lavas.
The names given to the lava types refer to localities in central and southern Scotland and the classification is applied only to basic igneous rocks of Carboniferous and Permian age in the Midland Valley of Scotland.
"The formation contains material derived by erosion from rocks of the Clyde Plateau Volcanic Formation and usually consists of red or purplish brown, poorly bedded, blocky-weathering mudstone and silty mudstone."
"However, north-east of Strathaven the Kirkwood Formation appears to be absent and coal-bearing strata of the Lawmuir Formation rest directly on lavas."
"In the Coldwakning Burn section, only a metre or so of strata intervene between the top of the Kirkwood Formation and the base of the Hurlet Limestone."
"Marine shells obtained from mudstone of the formation at a now-degraded exposure, south of East Kilbride, suggest correlation with the Stonehouse Under Limestone which lies at a high stratigraphical position in the Lawmuir Formation."
"The formation crops out along the northern flank of the area of Lower Carboniferous rocks around Glenbuck, where it is estimated to be about 120m thick."
"The Muirkirk Under Limestone, the local equivalent of the Blackbyre Limestone, is almost 2m thick and lies about 15m below the top of the formation."
There are few exposures in the area which flanks the Douglas Coalfield on the west.
"The sandstones in the lowest 10m are conglomeratic in places, with pebbles and boulders up to 10cm across of ` felsite ', ` porphyrite ', greywacke and chert, presumably derived by erosion from Silurian and Devonian rocks."
"The Douglas Under Limestone, as the Blackbyre Limestone is known locally, is 2.51m thick at a depth of 34.90m."
"The Craigburn Limestone, is represented by a bed of shelly calcareous mudstone, 0.85m thick, at a depth of 51.72m."
"In the faulted outlier at Drumclog, the Lawmuir Formation is represented by an attenuated sequence, little more than 15m thick at maximum, which rests on reddish brown tuffaceous mudstones of the Kirkwood Formation."
"A bed of limestone, 0.5m thick with gigantid productids, seen 550m west of Snabe -LSB- NS 6370 3912 -RSB- in an unnamed tributary of the Avon Water, was taken by Richey to be either the correlative of the Blackhall Limestone or of the combined Mid and Main Hosie limestones."
"However, the limestone and associated shelly calcareous mudstones, with a total thickness of 1.35m, were penetrated at a depth of 34.91m by the Fore Hareshaw Borehole and the fauna shows it to be the equivalent of the Blackbyre Limestone."
"At an intervening locality -LSB- NS 6475 4002 -RSB-, the limestone is absent and only a thin coal and its seat lie between the top of the Kirkwood Formation and the base of the Lower Limestone Formation."
"The formation is thin or possibly absent to the west and south of East Kilbride, where the Kirkwood Formation is well developed -LRB- Figure 4."
"It is present in an isolated outcrop north-east of the town and in the valley of the Rotten Calder, where the Basket Shell Bed and the Netherfield Limestone are still visible."
"The formation thins again farther east where it rests unconformably on Lower Devonian rocks, all older Carboniferous strata having been overlapped."
"The horizon known as the Netherfield Limestone, a little above the coal, consists of a series of shelly mud-stones with thin lenticular beds of bioclastic limestone, which have been correlated with the Dykebar Limestone of the Central Coalfield sequence."
"The Cot Castle Blackband Ironstone, about 0.3m thick, near the base of the section, is not now visible."
"However, the overlying Basket Shell Bed, the probable local representative of the Hollybush Limestone, is still exposed and consists of about 1.7m of mudstone containing a diverse marine fauna."
"Above the shell bed are mudstones, 3 to 4m thick, containing ironstone bands -- the Cot Castle Clayband ironstones."
"The limestone, which is taken to be equivalent to the Blackbyre Limestone, rests upon about 1m of fossiliferous mudstone, which in turn overlies a similar thickness of seatrock."
The strata between the Tree Coal and the Stonehouse Under Limestone are predominantly arenaceous.
"Approximately 15m of mainly arenaceous strata, tuffaceous in places, lie between the top of the limestone and the top of the Lawmuir Formation."
"A fine-grained grey rubbly sparsely shelly limestone, exposed at a point about 30m downstream, is thought to be at the horizon of the Basket Shell Bed."
"The Netherfield Coal was worked in the lands of Netherfield and Floors, east of Strathaven."
"In the Birkwood Burn -LSB- NS 798 420 -RSB-, the formation is only about 15m thick and rests unconformably upon Lower Devonian sandstones."
"The White Coral Limestone, which is taken as the equivalent of the Blackbyre Limestone, is well exposed and contains a rich fauna including colonial corals."
"The Clackmannan Group comprises, in upwards succession, the Lower Limestone, Limestone Coal, Upper Limestone and Passage formations."
"The group straddles the Dinantian - Silesian boundary, which is taken at a position a little below the top of the Lower Limestone Formation."
"Where the formation is fully developed, its base is taken at the base of the Hurlet Limestone of the Central Coalfield sequence or its correlatives, the Muirkirk Main Limestone in the Muirkirk area, the Douglas Main Limestone in the Douglas Coalfield, the Main Limestone of Drumclog in the Drumclog area and the Stonehouse Main Limestone in the Strathaven area."
"The top of the formation is defined at the top of the Top Hosie Limestone or its equivalents, the Calderwood Cement in the East Kilbride area and the uppermost of the series of limestones known in the Muirkirk and Douglas areas as the McDonald Limestones -LRB- Table 3."
"Apart from the topmost metre or two, which are of Pendleian Stage."
"The Lower Limestone Formation is at surface or present at shallow depth in a wide area around East Kilbride, and occurs also in a discontinuous series of outcrops which extends from Glassford to Kirkmuirhill."
"The Hurlet Limestone, at the base, is usually 2 to 3m thick, consisting of posts of dark grey, hard, crinoidal limestone interbedded with calcareous mudstone, and has been quarried extensively."
"The Wilsontown Smithy Coal, which is up to 0.6m thick, lies approximately 5m higher in the succession."
"A further 5m higher in the sequence, the Blackhall Limestone, which is known locally as the Foul Hosie Limestone, and the overlying fossiliferous calcareous mudstones of the Neilson Shell Bed are well exposed in the unnamed tributary of the Avon Water -LSB- NS 740 456 -RSB-, near Cot Castle, and also in the Avon Water -LSB- NS 721 447 -RSB- south of Waulkmill."
"The upper part of the formation contains four beds of limestone, the Main Hosie limestones, the local names being given in parentheses."
"Known collectively as the Hosie Limestones, all four beds are exposed in the Avon Water between Braehead -LSB- NS 738 462 -RSB- and St Ninian 's Church, Stonehouse -LSB- NS 747 471 -RSB-, and in Calderwood Glen -LSB- NS 659 544 -RSB- at East Kilbride."
"To the west of East Kilbride, the Main and Mid Hosie Limestone coalesce to form the Hairmyres Limestone."
"The Hawthorn Limestone, at the base, is considered with some reservations to be equivalent to the Hurlet Limestone of the Central Coalfield sequence."
"The Muirkirk Wee Limestone, regarded as the local equivalent of the Blackhall Limestone of the Central Coalfield sequence, is up to 1.3m thick and lies approximately 10m higher in the succession."
"A series of up to four limestones, the base of the lowest of which is from 7 to 9m stratigraphically above the Muirkirk Wee Limestone, is known collectively as the McDonald Limestones."
The uppermost of the limestones is correlated with the Top Hosie Limestone of the Central Coalfield.
"Grey bioclastic limestone interbedded with fossiliferous mudstone, exposed along the east bank of the River Nethan -LSB- NS 791 360 -RSB-, north of Over Stockbriggs, is considered to be the Douglas Main Limestone."
"At a section farther downstream -LSB- NS 793 360 -RSB-, two beds of grey limestone separated by about 2.5m of shelly mudstone probably lie in the lower part of the McDonald Limestones."
The thickness of the Lower Limestone Formation in the area is not known.
Only the lower part of the Lower Limestone Formation is present in the fault-bounded outlier at Drumclog.
"The Hurlet Limestone, which is up to 5.5m thick, has been extensively worked, notably in quarries around Meadowfoot -LSB- NS 632 394 -RSB- and WNW of Snabe."
The stratigraphical position of these seams was uncertain though a Limestone Coal Formation age was suggested by Richey.
The coal seams are presumed to correspond to the Wilsontown Smithy Coal.
"Sedimentary strata between the top of the Top Hosie Limestone and the base of the Index Limestone are assigned to the Limestone Coal Formation, which is of lowest Namurian, Pendleian age."
"Deltaic sedimentation was interrupted on two occasions by marine incursions, in the course of which widespread marine deposits -- the Black Metals and the Johnstone Shell Bed -- were laid down."
"At East Kilbride the Johnstone Shell Bed lies approximately 40m above the Top Hosie Limestone, the intervening strata consisting mainly of mudstone in the lower part and predominantly of sandstone above."
"A persistent but variable series of coals, approximately midway between the Johnstone Shell Bed and the Black Metals, is named the Lesmahagow Main Gas Coal in the area south of Stonehouse where there are two leaves, each about 0.25m thick."
"In the area between East Kilbride and Stonehouse, three seams are present in this position, in upwards succession the Smithy, Jaunt and House coals, which are collectively known as the Crutherland Coals."
"The Black Metals lie around 75 to 80m above the Top Hosie Limestone, with the Black Metals Marine Band in the lower part."
"Like the Johnstone Shell Bed, the unit is composed predominantly of mudstones but there are several lenticular beds of clayband ironstone, known as the Maggie Bands."
"In the Lanark district around Braidwood -LSB- NS 842 477 -RSB-, the Auchenheath Dross Coal, the Wee Gas Coal, and the Auchenheath Smithy Coal have been worked."
"There is little information on the upper part of the formation in the East Kilbride area but it is now apparent that some of the workings formerly considered to be in the House Coal are actually in a seam higher in the sequence, at a level approximately 97m above the Top Hosie Limestone."
"It is proposed to name the seam the East Kilbride Common Coal as an imprecisely located plan shows workings in the neighbourhood of the former common, near Mount Cameron -LSB- NS 644 539 -RSB-."
The Limestone Coal Formation is approximately 95m thick near Glenbuck but thickens to around 120m at Muirkirk in the New Cumnock district.
Two of these involved major incursions of the sea during which the fossiliferous mudstones of the Johnstone Shell Bed and the Black Metals Marine Band were laid down.
"The Johnstone Shell Bed, approximately 10m above the base of the formation, consists of dark grey mudstones with ironstone ribs."
"It overlies the McDonald Coal, from 0.25 to 1.82m thick, which was formerly worked, as also was the Low Band Ironstone within the Johnstone Shell Bed."
"Two important coal seams, the Six Foot Coal and the Thirty Inch Coal, lie between the Johnstone Shell Bed and the Black Metals."
"The formation in the western part of the Douglas Coalfield is about 90m thick and, as at Glenbuck, is composed of relatively thick fluviodeltaic cycles."
Deltaic sedimentation was interrupted on two occasions by incursions of the sea in the course of which the fossiliferous mudstones of the Johnstone Shell Bed and the Black Metals Marine Band were laid down.
The McDonald Coal which lies beneath the Johnstone Shell Bed was little worked underground but recently has been exploited by opencast methods.
"Strata in this area shown as Limestone Coal Group on earlier editions of the Geological Sheet 23, are now considered to belong to the Lower Limestone Formation."
This formation comprises the strata that lie above the base of the Index Limestone.
"These consist, in upwards succession, of the Index Limestone, the Lyoncross and the Plean Nos. 1 and 2 limestones."
"The entire formation is of Namurian age, the lower part being Pendleian."
The full thickness of the formation is present also in the Glenbuck area but only the basal few metres of the Douglas Coalfield development of the formation lie within the district.
This variation is largely attributable to erosion associated with uplift in the period prior to deposition of the Passage Formation.
"Thus, at Motherwell where the sequence is most complete, the base of the Passage Formation is at a level approximately 5m above Plean No. 2 Limestone, whereas near Kirkmuirhill it lies about 13m above the Orchard Limestone."
"However, in the Darngaber Burn, the Plean No. 1 Limestone is cut out by erosion in places, and in the Larkhall-Stonehouse area the erosion surface lies not far above the Calmy Limestone, at a level some 25 to 30m higher than at Kirkmuirhill."
"Although the information is scant, it is possible that not all of the variation in thickness can be accounted for by pre - Passage Formation erosion."
"Thus the strata between the Index Limestone and the Orchard Limestone are about 45m thick at Motherwell and are even thicker south-west of Hamilton, but at Kirkmuirhill they appear to be less than 35m thick."
"As in the other parts of the Central Coalfield, the Index Limestone is a hard compact bioclastic limestone, 1.5 to 2m thick."
"The Lyoncross Limestone, up to 38m above the Index Limestone, is underlain by a persistent seatrock above which the Lyoncross Coal is developed in places."
The Orchard Limestone consists of hard bioclastic limestone from 0.4 to 0.8m thick at the base of a 5 to 6m thick sequence of shelly mudstone.
"A thick development of cross-bedded sandstone lying between the Orchard and Calmy limestones was formerly worked for freestone in a quarry -LSB- NS 717 514 -RSB-, north-west of Kilnhill."
The Calmy Limestone is everywhere present except in the neighbourhood of Kirkmuirhill where it is believed to have been eroded prior to deposition of the Passage Formation.
The limestone seen in this section was shown on the previous edition of the geological map as the Castlecary Limestone but is now considered to be the Plean No. 1 Limestone.
"In the bore, the Plean No. 1 Limestone lies approximately 27m above the Calmy Limestone and is represented by a thin band of ` earthy ' limestone and fossiliferous calcareous mudstone."
"A bed of crinoidal limestone, 0.5m thick, seen in a stream section -LSB- NS 7223 5007 -RSB- north of Crookedstone, may be the Plean No. 2 Limestone."
"Strata in the uppermost part of the Upper Limestone Formation, consisting mainly of ripple-laminated and cross-bedded, yellow-weathering sandstone, are exposed in a tributary of the River Clyde -LSB- NS 796 502 -RSB-, near Auldton."
The Index Limestone is 1.5 to 3m thick and is overlain by up to 9m of silty mudstone with limestone ribs.
"The Birchlaw Limestone, which lies on average 18m above the Index Limestone, does not appear to have an equivalent in the Central Coalfield area."
"The Cokeyard Coal, which lies about 37m above the Index Limestone and varies from 0.7 to 1.5m in thickness, was worked locally but is commonly split into several leaves none of which reaches workable thickness."
Tibbie Pagan 's Limestone lies approximately 60m stratigraphically higher than the Index Limestone and is correlated with the Lyoncross Limestone of the Central Coalfield area.
"The base of the Orchard Beds, a series of mudstones with limestone ribs, up to 12m thick, lies 80 to 90m above the Index Limestone."
"The Blue Tour Limestone, taken as equivalent to the Calmy Limestone, lies approximately 30m above the Orchard Beds, with the Blue Tour Coal some 2m below its base."
"A limestone which lies approximately 60m above the Blue Tour Limestone in borehole NS72NW/28 -LSB- NS 7442 2842 -RSB- is possibly the Plean No. 1 Limestone, although there is limited information about this part of the sequence."
"The older of the two occurs at the base of the sequence, which rests on strata of the Upper Limestone Formation ranging in stratigraphical position from a little above the Calmy Limestone to above the Plean No. 2 Limestone."
The younger of the two unconformities was identified by Ross to lie at a stratigraphical level above No. 6 Marine Band Group of the Stirling succession.
"If the Namurian - Westphalian boundary lies near the top of No. 6 Marine Band Group, as Neves et al. have suggested, then it follows that all the Passage Formation strata in the Hamilton district may be of Westphalian age."
"The basal beds of the formation are seen in the Darngaber Burn -LSB- NS 724 502 -RSB-, east of Burnbrae, where they rest unconformably on seatrocks at a level below the Plean No. 2 Limestone in the Upper Limestone Formation."
"Sandstones of the formation are also exposed farther downstream -LSB- NS 7275 5055 -RSB-, where they are faulted against strata of the Lower Coal Measures, and in the Crookedstone Burn at Wellbog Plantation -LSB- NS 7295 5015 -RSB-."
"The thickest known development of the formation in the district was cut by NS75SE/333, which penetrated a sequence, about 33m thick, of grey sandstones with thin beds of rooty siltstone and a 0.6m thick seam of soft coal, possibly the Bowhousebog Coal, near the base."
"The group contains three formations, the Lower Coal Measures, the Middle Coal Measures and the Upper Coal Measures Figure 7."
"There is evidence that, as in earlier periods of the Carboniferous, deposition was influenced by the differential rates of subsidence of fault-bounded blocks."
"The deposits laid down in the course of these trangressions, the Vanderbeckei Marine Band and the Aegiranum Marine Band have been regarded as marker horizons and used to delimit the formations."
"Conventionally, the base of the group is taken at the base of the Lowstone Marine Band."
The strata are entirely of Westphalian age.
"The Lower and Upper Slatyband ironstones, associated with the Lowstone Marine Band and Mill Coal respectively, have been worked in the area around Crookedstone, otherwise this part of the sequence contains no mineral seams of workable thickness and has been penetrated in full by relatively few boreholes."
"The position of the Lowstone Marine Band can be recognised but a fauna, including Lingula sp., has been recovered only in the Dykehead Borehole -LSB- NS 7564 5267 -RSB- and at an exposure in the Dalserf Burn -LSB- NS 7955 4990 -RSB-, east of Ashgill."
"The Colinburn Coal is generally thin, its mudstone roof yielding nonmarine bivalves in boreholes at Dykehead and Garriongill."
"The horizons of the Auldshiels Mussel Band and the Armadale Main and Ball coals can usually be identified, the roof of the last containing Carbonicola pseudorobusta at Dykehead."
"The Mill Coal, with Carbonicola in its roof at Ferniegair -LSB- NS 7525 5441 -RSB-, reaches a maximum thickness of 0.4 m. Similar faunas come from the mudstone above the thin Shott 's Gas Coal."
"The strata between the Mill and Lower Drumgray coals are seen in exposures along the Crookedstone Burn, where they consist of sandstones and siltstones with seatrocks, the total thickness being about 19m."
The Lower Drumgray Coal is not seen in the section.
"Still farther upstream -LSB- NS 7584 5000 -RSB-, the Wellbog Musselband at the horizon of the Mill Coal, contains a fauna of nonmarine bivalves."
"Elsewhere it is thin or absent but, in the Larkhall-Stonehouse area, it is associated with the Watstone Musselband Ironstone which was worked locally."
The Mid and Upper Drumgray coals were worked from adits on the valley sides of the Avon Water in the vicinity of the Larkhall Viaduct.
"The strata between the top of the Kiltongue Coal and the top of the Lower Coal Measures, taken at the base of the Queenslie Marine Band, vary from about 37m to more than 50m thick."
"The Airdrie Virtuewell Coal, near the top of sequence, has been extensively worked."
"The Bellside Ironstone, which was widely worked in the area east of Wishaw, does not reach workable thickness in the district."
"The Kiltongue Mussel Band, a conspicuous horizon recognisable in almost every borehole, lies at a distance above the Kiltongue Coal that varies from less than 10m to about 18m."
"In the sequence above the Kiltongue Mussel Band, the Ladygrange Coal, with a fauna of Naiadites and ostracods in its roof, and the Bellside Ironstone can be recognised in places, neither being present in workable thickness."
"Bivalves were found at a horizon between the Kiltongue Mussel Band and the Airdrie Virtuewell Coal in the Dalserf Burn -LSB- NS 7987 5044 -RSB-, 120m upstream from the road bridge."
Some 3 to 5m of mainly argillaceous strata lie between the Airdrie Virtuewell Coal and the Queenslie Marine Band.
The base of the formation is taken at the base of the Queenslie Marine Band.
"More commonly, the horizon is taken to lie within a thin development of argillaceous strata some 3 to 5m above the Airdrie Virtuewell Coal."
"The Airdrie Blackband Coal is up to 0.75 thick and has been extensively worked in the north-west, around Hamilton."
The associated Airdrie Blackband Ironstone has been worked only around Quarter.
"The Coatbridge Mussel Band, consisting of up to 4m of mudstone with pale brown ironstone bands, lies about halfway between the Airdrie Blackband position and the base of the Glasgow Splint Coal."
"There is no workable coal at this position: nor is there at the horizon of the Virgin Coal, 2 to 4m below the Glasgow Splint Coal, except in a small area -LSB- NS 783 483 -RSB-, near Millburn."
"The thickness of the sequence from the base of the Glasgow Splint to the base of the Glasgow Main Coal exceeds 25m in the area south of Wishaw but decreases in all directions to less than 20m, except in Whistleberry No. 1 Pit -LSB- NS 7025 5725 -RSB- where the sequence is 27m thick."
"The strata between the Glasgow Splint Coal and the Humph Coal are mainly arenaceous and vary in thickness from about 6 to 14m, being thickest and having the greatest ratio of sandstone in a belt extending WSW through South Quarter."
"The Pyotshaw Coal is everywhere workable, locally reaching a thickness of more than 1m."
"It is separated from the Glasgow Main Coal by mainly argillaceous strata which range in thickness from little more than a parting in the area south of Wishaw, where the seam was worked jointly with the Main Coal, to more than 13m."
Up to five fossiliferous horizons have been recognised in the beds above the Glasgow Upper Coal.
"Fossils were also found in the Ashgillhead Borehole at three higher levels in the sequence: the lowest was probably the horizon of the Palacecraig Coal and the middle one possibly at the horizon of the Carnbroe Marine Band, although only nonmarine bivalves and Euestheria were found."
"A recently drilled series of boreholes near Quarter, recovered fossils from beds above and below a possible correlative of the Glasgow Upper Coal."
"A musselband, 180m upstream from Blackbog -LSB- NS 7181 5181 -RSB-, yielded a fauna of nonmarine bivalves which suggests a position above the Glasgow Upper Coal."
"In the lower half of the sequence, the thick Chatelherault Sandstone below and the Hamilton Sandstone above are separated by a variable sequence of seatearths, mudstones and thin coals, termed the Barncluith Coal Group by Carruthers and Dinham but here referred to as the Barncluith Coals."
"Downstream in the Meikle Burn, the argillaceous sequence passes beneath soft yellow sandstone, which is probably at the lowest part of the Chatelherault Sandstone."
"At a hitherto unrecorded occurrence -LSB- NS 7938 5075 -RSB-, about 80m upstream from the Lanark Road, Skipsey 's Marine Band consists of dark grey carbonaceous mudstone with a fauna which includes Posidonia."
It is probable that a fault throwing down to the north separates this argillaceous sequence from the exposures of the Chatelherault Sandstone to the south.
"In the Meikle Burn below its confluence with the Eddlewood Burn, and probably on the downthrown side of another east-west fault, the contact of the argillaceous sequence with the overlying Hamilton Sandstone is seen for a distance of some 900m."
"Following a hiatus, sedimentation resumed in the district with the deposition of the calcrete-bearing rocks of the Kinnesswood Formation."
"As a result, the Ballagan Formation was deposited in a shallow-water environment with restricted access to the open sea and subject to marked changes of salinity and periodic desiccation."
The Midland Valley basin at this time was presumably more extensive than during deposition of the Kinnesswood Formation but there is no known locality where rocks of this age are overlapped by the cementstone-bearing sequences of the Ballagan Formation.
"Just as the onset of marine conditions was gradual, so also was the resumption of fluvial sedimentation towards the end of Ballagan Formation times, with deposition of the calcrete-bearing sequences of the Clyde Sandstone Formation."
"Uplift accompanied by movement on faults, almost certainly in some cases involving the reactivation of more-ancient fractures, induced the removal by erosion of part, and locally all, of the Inverclyde Group strata previously laid down."
It is possible that the uplift may be partly attributable to the development beneath the western part of the Midland Valley of the large magma chamber which eventually gave rise to the lavas and associated volcanodetrital rocks of the Clyde Plateau Volcanic Formation.
The mid - Dinantian erosion surface marks an important stage in the structural development of the Midland Valley.
The lavas of the Clyde Plateau Volcanic Formation were extruded subaerially and generated a relief which probably amounted to several hundred metres in places.
"During later Strathclyde Group times, the volcaniclastic detritus of the Kirkwood Formation accumulated on the low ground within and adjacent to this lava pile, encroaching farther on to the lavas as subsidence continued."
"The lavas continued to contribute material to the basin almost until the end of Strathclyde Group times, as shown by the occurrence within the detritus of a possible correlative of the Blackbyre Limestone, and in adjacent districts the lava pile was not completely buried until well into Clackmannan Group times."
"The relationship of the two formations with one another is strongly diachronous and in the west, for example at Fore Hareshaw, the oldest strata of the Lawmuir Formation are at a level only a little below the horizon of the Blackbyre Limestone."
"During the final stages of the cycle, soils developed on the interdistributary floodplains under the hot, wet to humid climatic conditions which were initiated in late Inverclyde Group times, and layers of vegetable material were laid down."
"Visean rocks of various ages rest on either the volcanic detritus overlying the Clyde Plateau Volcanic Formation, for example south-west and west of East Kilbride and in the Strathaven and Drumclog areas, or on an unfossiliferous sequence of siltstones and sandstones of uncertain age, as in the Coalburn and Muirkirk areas."
"In the area east of Strathaven this limestone is represented by the Basket or Cot Castle Shell Bed, still visible in the River Avon at Cot Castle -LSB- NS 7398 4575: NS 7380 4576 -RSB-."
At the north end of the Muirkirk area the Muirkirk Under Limestone rests on unfossiliferous strata considered to belong to the Inverclyde Group.
"In the western outlier at Drumclog the Hurlet Limestone, known locally as the Main Limestone, was extensively quarried."
"The fauna is more varied than that occurring in the Blackbyre Limestone and includes, amongst other species, Dibunophyllum muirheadi, Angiospirifer cf. trigonalis, Antiquatonia hindi, Beecheria sp., Eomarginifera spp., Gigantoproductus giganteus, Latiproductus latissimus, Pleuropugnoides pleurodon, Productus cf. concinnus, Pugilis pugilis, Rugosochonetes celticus, Aviculopecten spp., Leiopteria cf. hendersoni, Limipecten sp., Myalina cf. flemingi, Pernopecten sowerbii and Streblochondria sp."
has been recorded in workings from the mudstone above the Wilsontown Smithy Coal but elsewhere the bed appears barren.
"However, at Drumclog, in the BGS Fore Hareshaw Borehole, the roof of the seam above the local ` Main Limestone ' carries a small marine fauna consisting principally of poorly preserved productoids, and may represent the position of the Craigenhill Limestone of the Lanark district."
"The Blackhall Limestone is thin and may lie close to the Hurlet Limestone in the area to the west of East Kilbride around Thorntonhall, in the Kilmarnock district."
"The overlying mudstones, which have been termed the Neilson Shell Bed, contain a typical fauna with Crurithyris urii, Tornquistia youngi, Glabrocingulum atomarium, Retispira spp., Nuculopsis gibbosa, Anthraconeilo spp., Pernopecten fragilis, Posidonia corrugata, Catastroboceras sp."
"Around Strathaven the limestone may be recognised by the accompanying Neilson Shell Bed which has a characteristic fauna including Fenestella sp., Crurithyris urii, Eomarginifera spp., Rugosochonetes speciosus, Tornquistia polita, T. youngi, Euphemites sp., Glabrocingulum atomarium, Straparollus carbonarius, Strobeus spp., Euchondria sp., Nuculopsis gibbosa, Phestia attenuata, Reticycloceras sp."
"Farther south, in the Coalburn area, the Blackhall Limestone is known as the Douglas Wee Limestone, and in the Lanark district is associated with a Neilson Shell Bed fauna."
"In the Muirkirk area the corresponding Muirkirk Wee Limestone also contains Gigantoproductus sp., together with Composita sp., Rugosochonetes sp."
"The Second Hosie Limestone contains a variety of brachiopod species including Eomarginifera lobata, Pugilis sp., Spirifer sp."
"and Spiriferellina sp., together with Euphemites urii, Pernopecten sowerbii and Streblochondria sp.: the Top Hosie Limestone is associated with overlying mudstones which contain an abundance of Posidonia corrugata."
She drew attention to the similarity of this species to Cravenoceras leion the first appearance of which has been taken to mark the base of the Namurian in the British Isles.
"On the western margin of the Coalburn area, in the discontinuous section -LSB- NS 7928 3604 -RSB- in the River Nethan near Over Stockbriggs, beds probably within the lower portion of the McDonald Limestones contain Angiospirifer cf. trigonalis, Buxtonia sp., Composita ambigua, Eomarginifera lobata, Krotovia sp., Rugosochonetes celticus, Euphemites urii and Pernopecten sowerbii."
The fauna as a whole is characteristic of calcareous strata throughout the Dinantian of the Midland Valley.
The uppermost bed of the McDonald Limestones has been correlated with the Top Hosie Limestone of the Central Coalfield.
Wilson has already noted that it was not until the Hurlet Limestone transgression that the region was wholly covered by sea.
"The faunas of earlier incursions depend, at least in part, on the relationship of the present outcrop to the Carboniferous shorelines at the time of the incursion."
At most locations the Top Hosie Limestone is overlain by a considerable thickness of mudstone.
In both the Coalburn and Muirkirk areas the mudstones overlying the McDonald Limestones are thin with Lingula sp.
In the Muirkirk Basin the same marine band overlies the Thirty Inch Coal and contains Lingula sp.
"Minor cycles such as the Huntershill Limestone and the Plean Limestones are poorly developed, particularly in the south."
The faunas of all these beds have been discussed by Wilson who drew attention to the geographical variations apparently related to the thickness of sediment in the interval between the Index and Calmy limestones.
Goniatites of zonal significance are rare in the Scottish Carboniferous but sufficient have been discovered to demonstrate that the boundary between the Pendleian and Arnsbergian stages must lie between the Lyoncross and Orchard limestones.
"In the Coalburn area the Index Limestone is the only horizon in the formation which has been examined: around Auchenbeg -LSB- NS 798 361 -RSB- the limestone and its associated mudstones contain Gigantoproductus cf. irregularis, Latiproductus cf. latissimus, Pleuropugnoides sp., Schellwienella sp., Myalina sp."
"Above the Calmy Limestone, mudstones with Leptagonia smithi, Pugnax cf. pugnus, Rugosochonetes caledonicus, Euphemites ardenensis, Glabrocingulum sp., Nuculopsis gibbosa, Anthroconeilo cf. laevirostrum and Tylonautilus ? The overlying Plean limestones are variably present."
The Castlecary Limestone at the top of the formation appears to be absent throughout the district.
"In the area flanking the gorge of the River Avon -LSB- NS 759 495 -RSB- much of the formation is absent and the Lowstone Marine Band, the local base of the Coal Measures, lies stratigraphically close to the Calmy Limestone."
"The musselband above the Upper Drumgray Coal, commonly highly fossiliferous in the area around Shotts in the adjacent Lanark district, is here poorly fossiliferous, but the characteristic Carbonicola cf. pseudorobusta is present in the fauna from this horizon in Stonehouse No. 77 Borehole and around Canderside -LSB- NS 777 463 -RSB-."
"The Kiltongue Musselband, containing Anthraconaia sp., Anthracosia spp., Carbonicola oslancis and Geisina arcuata, is widespread and has been taken as the base of the modiolaris Biozone."
The Vanderbeckei Marine Band is poorly developed in the Hamilton district and only foraminifera and Lingula mytilloides have been recovered from boreholes and field exposures.
"The roof of the Airdrie Blackband Coal contains a limited fauna including Anthracosia aquilina, A. beaniana, A. ovum and A. phrygiana."
Surface exposures of the various beds up to the Aegiranum Marine Band are uncommon and only the Dalserf Musselband fauna is well represented.
"The Aegiranum Marine Band at the base is found at a number of locations, notably in Stewart Gill -LSB- NS 7938 5075 -RSB-, the River Avon at Hamilton High Parks -LSB- NS 7349 5297: NS 7360 5355 -RSB-, the River Clyde -LSB- NS 7976 5075 -RSB- and the railway cutting near Parkhead, Motherwell -LSB- NS 7510 5640 -RSB-."
"The Bothwell Bridge Marine Band, so named from an exposure in the River Clyde -LSB- NS 7085 5766 -RSB- on the adjacent Airdrie district, is present in the Craighead Borehole at a depth of 72 m. The position has been correlated with the Shafton Marine Band of the Pennine succession."
"The oldest and most numerous were probably emplaced during the Lower Devonian, around 400 million years ago, into the Silurian and Lower Devonian rocks of the Lesmahagow Inlier."
"A number of bodies of mainly basic, in some cases heavily altered, material, cutting Carboniferous rocks, are considered to have been intruded at various periods during the Carboniferous."
"This is especially TRUE of the numerous bodies of mainly acid composition, ranging in thickness from less than a metre to more than 100m, which are intruded into the Silurian and Devonian rocks in the south."
"An Rb-Sr isochron of age 412.8 _ 5.6 Ma, determined for the body from fresh biotite and plagioclase separates and a whole rock granodiorite by Thirlwall, suggests that it was emplaced during the earliest Devonian."
"The most prominent intrusions are the suite of lenticular, sheet-like bodies of mainly acid intermediate composition which cut Silurian and Lower Devonian rocks in the south of the district."
Where thin sill-like bodies are intruded into grey Silurian turbidites they may be difficult to distinguish in the field from beds of greywacke.
"Sills of olivine-dolerite crop out extensively in the area between Nethershields -LSB- NS 700 488 -RSB- and Craigthorn -LSB- NS 735 484 -RSB-, intruding strata of the Lawmuir and Limestone Coal formations."
"To the southeast of Stonehouse, in the neighbourhood of Draffen -LSB- NS 794 453 -RSB-, doleritic sills have been encountered in underground workings in the Lesmahagow Main Gas Coal."
"An east-west-trending dyke composed of heavily altered dolerite, exposed -LSB- NS 7472 4930 -RSB- south of Corslet, in an unnamed tributary of the Darngaber Burn, probably belongs to the extensive suite of dykes of this trend which was emplaced during the late Carboniferous or early Permian."
"A sub-cylindrical body of trachyte, which forms the conspicuous skyline feature of Loudoun Hill, is considered to be a plug infilling the feeder pipe of a vent active during eruption of the Clyde Plateau Volcanic Formation."
"In the south-west, four bodies consisting mainly of basaltic breccia, cutting strata ranging in age from Silurian to early Namurian are regarded as vents associated with late Carboniferous to Permian volcanicity."
The Distinkhorn Plutonic Complex is made up bodies of granodioritic and dioritic composition.
"Information relating to the earliest development of this ancient feature, and in particular of the fault system which forms its southern boundary, is provided by the Silurian rocks of the Lesmahagow and Hagshaw Hills inliers."
Re-activation of these faults at various times had an especially marked effect on the distribution of the Lower Carboniferous.
"During the Silurian period, closure of the Iapetus Ocean by subduction processes brought the Eastern Avalonian plate into oblique collision with the Laurentian plate."
"In the Lesmahagow and Hagshaw Hills inliers, it is probable that a stratigraphical break occurs between the Silurian rocks and those assigned to the Devonian, although there is no marked angular unconformity corresponding with that in the Pentland Hills."
The onset of sedimentation was delayed until early Carboniferous times when the cornstone-bearing sandstones of the Kinnesswood Formation were laid down under quiet tectonic conditions by NE-flowing rivers in a subsiding basin at least as broad as the present Midland Valley.
Continuing subsidence for a time allowed deposition of the Ballagan Formation in a coastal sabkha or restricted marine environment subject to fluctuating salinities and periodic desiccation before uplift of the upland source areas restored fluvial conditions towards the end of the Inverclyde Group period.
"The evidence is sparse but in places removal of the Inverclyde Group was mainly or entirely complete before extrusion of the Clyde Plateau Volcanic Formation lavas, especially over a tract in the west-central part of the Midland Valley which appears to have been bounded in the south by the Inchgotrick Fault, and in the west by the Largs Ruck Figure 8."
It has been suggested that the uplift was due to magmatic updoming prior to extrusion of the lavas of the Clyde Plateau Volcanic Formation.
"One such is the NW-trending fracture zone, represented by the post - Westphalian Dechmont Fault which forms the eastern boundary of the North Ayrshire Block."
"This block, which contains the thick lava pile of the Clyde Plateau Volcanic Formation, remained relatively buoyant through much of the later Carboniferous, possibly as a result of isostatic response to crustal thickening caused by emplacement of a high-level magma chamber."
"During deposition of the Lawmuir Formation, movements on the Inchgotrick and Strathaven faults, at the southern margin of the North Ayrshire Block, may account for the unusually thick sequence contained in a narrow basin at Strathaven."
"In the Douglas Basin especially, thicker sequences of the Lawmuir, Upper Limestone and Passage formations were laid down than occur elsewhere in the Hamilton district."
"Basin subsidence in the district was halted by uplift, presumably as a result of transpressional movements, late in Upper Limestone Formation times and during deposition of the Passage Formation."
"It is probable that most of the extensive system of faults of east-west and NW-SE trend Figure 9, which cut the youngest Carboniferous rocks in the district, date from the latest Carboniferous or early Permian."
In the Hamilton district almost all evidence of earlier glaciations and interglacials was removed by erosion during the last main late Devensian.
"Late Quaternary drift deposits blanket much of the area of the Hamilton district, particularly on the low ground, masking a land surface which had evolved during the Tertiary and the early Quaternary."
Extensive drift deposits cover the less resistent Devonian and Carboniferous sedimentary rocks in the northern half of the Hamilton district except where these deposits have been cut through by later erosion in the incised valleys draining into the River Clyde or by the recent activities of man.
"The Flandrian Stage commenced at 10000 BP, with a rapid rise in temperature."
"Finally, man has left his imprint on the landscape during the last two centuries of industrial activity, particularly in the areas underlain by coal-bearing Carboniferous rocks in the northern half and the extreme south-east of the district."
"The deposit is a continuation of the Wilderness Till Formation, named after the Wilderness Plantation north of Bishopbriggs in the Glasgow district."
In areas of Carboniferous sedimentary rocks the till is a dark grey silty clay with pebbles and boulders mainly of Carboniferous sandstones and limestones.
"Over Devonian outcrops, the till consists of reddish sandy clay with predominantly red sandstone clasts."
There are few exposures of till in the mainly peat-covered ground over the outcrop of the Clyde Plateau Volcanic Formation but here the deposit tends to be variegated with mainly igneous pebbles and boulders.
"In areas of Silurian rocks, where the till is commonly confined to the lower valley-sides and valley-bottoms, there is a predominance of tabular greywacke and siltstone clasts in an assemblage which also includes clasts of quartzite, chert, jasper and the various Lower Devonian intrusive rocks."
Till is normally the deposit lying immediately on the bedrock and underlies most of the other Quaternary deposits.
"North-east of a line connecting the Renfrewshire Hills to the high ground over the Clyde Plateau Volcanic Formation west of Strathaven, glacial striae and drumlins are aligned NW-SE whereas to the south-west they have a SW-NE trend."
"The lower part of the deposit consists of laminated clay and silt assigned to the Bellshill Formation, the upper part, composed mainly of sand with gravel in places, is referred to the Ross Formation."
"At a late stage in the lifetime of Lake Clydesdale, perhaps while the ice dam lay at the suggested terminal moraine of Blantyreferme ridge -LSB- NS 673 595 -RSB- a short distance north of the district boundary, a thick body of sand and gravel of the Ross Formation was contributed to the lake infill in the neighbourhood of Ferniegair by the northward flowing Avon Water."
"Screes, such as the one on Loudoun Hill, may have been initiated by during periglacial conditions but continued to form throughout the Flandrian."
"Most of the geological processes that shaped the landforms throughout the Flandrian probably had started in the Late Devensian: screes, incised gorges, landslips, lacustrine deposits and fluvial deposits."
"Despite these depredations, hill peat still covers much of the Silurian hills in the south and Clyde Plateau lavas hills in the west of the district, notably at Mossmulloch -LSB- NS 635 415 -RSB-."
"These form spectacular rock gorges, such as those in the Avon Water and in the Rotten Calder near East Kilbride, cut mainly in lower Carboniferous sedimentary rocks with normally only a thin cover of superficial deposits -LRB- Figures 10and 11."
In age the lacustrine deposits probably range from the earliest Flandrian almost to Recent and may even date back to the latest Devensian.
McMillan assigned such deposits formed during the Flandrian to the Kelvin Formation.
Throughout the Flandrian extensive alluvial deposits built up as the post - Devensian drainage system developed.
Coarse-grained Flandrian sediments to the Law Formation.
"Beds of mudstone within the bedrock offer more uniform material, possible horizons being the Black Metals and the mudstones that overlie the Top Hosie, Index, Orchard and Calmy limestones."
Thick mudstones also occur above the Glasgow Ell Coal.
"Within the Upper Coal Measures mudstones associated with the Chatelherault and Hamilton sandstones have been worked at Carscallan -LSB- NS 723 523 -RSB-, near Hamilton."
The Chatelherault and Hamilton sandstones of the Upper Coal Measures in the Hamilton area were formerly an important source of building stone.
"A sandstone lying a little above the Kiltongue Musselband was quarried and mined for building stone at Overwood -LSB- NS 771 461 -RSB-, south-east of Stonehouse."
The thick sandstone which lies between the Orchard and Calmy limestones was worked west of Quarter -LSB- NS 717 514 -RSB-.
The highly siliceous sandstone beneath the Calmy Limestone was formerly mined for refractory use in the Avon Water gorge -LSB- NS 764 494 -RSB- at Larkhall.
Workings in the Hurlet and Calmy limestones were particularly common.
The thickest beds of cornstone in the Kinnesswood Formation were also exploited.
"The Top Hosie Limestone, although relatively thin, was mined on account of its properties as a natural cement, in the East Kilbride area -LSB- NS 660 545 -RSB- under its local name the Calderwood Cement."
"Ironstone developed at about the position of the Crutherland Coals was worked around Earnockmuir -LSB- NS 688 526 -RSB-, south-east of East Kilbride."
"The Maggie Bands, the collective name for the clayband ironstones at the position of the Black Metals in the Central Coalfield, have been worked sporadically in association with coal extraction."
"The Crossbasket Ironstones of the Lower Limestone Formation were mined around Auchentibber -LSB- NS 668 552 -RSB- and near Craigendhill -LSB- NS 692 513 -RSB-, east of East Kilbride."
Clayband and blackband ironstones in the Lawmuir Formation were worked beside the Avon Water at Cot Castle -LSB- NS 739 458 -RSB- near Stonehouse.
"Two ironstones seams, known as the Mid and High Band ironstones and lying at a similar stratigraphical position to the Maggie Bands of the Central Coalfield, were of the considerable economic importance in the Glenbuck-Muirkirk area, as was a lower ironstone, known as the Low Band, which lies just above the Johnstone Shell Bed."
"Ironstones at other positions, such as the Cleland Roughband Ironstone, Watstone Musselband Ironstone, Upper and Lower Slatyband Ironstones and the Airdrie Blackband Ironstone, have also been exploited to some extent."
The ` shale ' which commonly occurs at the Kiltongue Musselband position has been worked for oil beside the Avon Water at Stonehouse -LSB- NS 760 476 -RSB-.
"The Clyde Plateau Volcanic Formation is composed predominantly of basaltic lavas, with occurrences of trachytic lava in western parts of the district."
"Coal occurs at two main levels in the succession, the Limestone Coal Formation and in the Lower and Middle Coal Measures."
Many of the thinner coals in the lower half of the Lower Coal Measures have been exploited by underground working to a limited extent only.
"The Limestone Coal Formation contains few thick coals but the relatively close spacing of seams, such as the Crutherland Coals in East Kilbride area for instance, means that opencast extraction may be economic."
Deeper groundwater circulation is present only in the Carboniferous rocks.
"Modest supplies for domestic use have been obtained from the Lower Devonian rocks and from the Lower Carboniferous sequence, including the lavas."
"At Cleland, up to 770m3/d of alkaline fluid with a high biological oxygen demand was discharged into workings of the Glasgow Main Coal, the workings in the Glasgow Ell Coal, at a shallower depth, being dry."
Only two formations above the basement within the district have geothermal potential -- sandstones of the Kinnesswood Formation at the base of the Carboniferous and sandstones of the Namurian Passage Formation.
"However, the geological evidence suggests that the Lower Carboniferous is unlikely to reach this depth and overlies Lower Devonian rocks with little geothermal potential."
"One of the lines Figure 14, line QB-3 -RRB- traversed the line of the Distinkhorn Plutonic Complex which was interpreted as a steep-sided body intruded only in the Lower Palaeozoic rocks of the Lesmahagow Inlier."
"Where the line crossed the eastern margin of the outcrop of the Clyde Plateau Volcanic Formation, a 6.0kms-1 refractor was identified at a depth of about 4km."
The Ordovician and Silurian greywackes of the Southern Uplands have a mean saturated density close to 2.72Mgm-3 but this figure can be expected to increase slightly with depth.
"There is no evidence that Upper Devonian rocks are present in the district but, in the Midland Valley as a whole, rocks of this age have been given a mean saturated density of 2.41Mgm-3."
"The carbonate-bearing sandstones of the Kinnesswood Formation, which are mainly, if not entirely, of lower Carboniferous age, are assigned the significantly higher value of 2.58Mgm-3."
The Dinantian sedimentary sequence has a mean density of about 2.58Mgm-3: the Namurian and Westphalian sedimentary rocks have a density of about 2.55Mgm-3.
Many of the Carboniferous extrusive rocks in the Midland Valley have a low intensity of Natural Remanent Magnetism.
"Minor intrusions of gabbroic or dioritic composition into the Clyde Plateau Volcanic Formation have susceptibilities at outcrop up to 0.04 SI units, similar to that of the Distinkhorn Plutonic Complex."
The suggested values are 2.5 to 3.5 km s-1 for the Carboniferous and Upper Devonian sequence and 4 to 5.5 km s-1 for the Lower Devonian and Lower Palaeozoic sequences.
A large gravity high over the North Ayrshire Block and the associated magnetic magnetic anomalies over the Clyde Plateau Volcanic Formation.
Alomari suggested that the gravity low of the Hamilton-Wishaw area was related either to a granite which extended from depths of 4 to 12km or to an 8km thick Lower Devonian basin with its base at a depth of 12km.
Alternative interpretations attributing the anomaly to a thick sequence of low density post-Lower Devonian rocks appear to be supported by the close correspondence of the trend of the Bouguer anomaly contours with the boundaries of the Carboniferous outcrops and with mapped faults.
The large gravity high over the North Ayrshire Block is associated with outcrops of the Clyde Plateau Volcanic Formation and also with high amplitude magnetic anomalies Figure 15.
"However, interpretation of the magnetic anomalies suggests that they can not be caused by the inferred thickness of lavas alone but are probably also partly due to underlying penecontemporaneous basic, probably gabbroic, intrusions about 1.5 - 2.0km thick emplaced within high density Lower Palaeozoic rocks and/or to relatively dense, strongly magnetic rocks within the basement."
Evans et al. suggested that the source of the anomalies was a composite volcanic centre of Devonian - Carboniferous age with superimposed Dinantian extrusive activity.
"The outcrop and aureole of the intrusion lie within sedimentary rocks of Lower Devonian age and, to the south-east, Silurian age."
The existence of the gravity high probably indicates that the concealed part of the intrusion consists mainly of diorite but part of the anomaly could be due to the presence of relatively high density Lower Palaeozoic sedimentary rocks.
"The acoustic impedance of the Clyde Plateau Volcanic Formation is generally much higher than that of sedimentary rocks with the result that its boundaries have high reflection coefficients, preventing much energy from reaching greater depths."
"The deepest reflector, at about 2km, was interpreted as the top of the Lower Devonian."
The MAVIS and quarry blast surveys have been interpreted in terms of a four-layer upper crust: 0.5 - 3.0km thick Carboniferous and Upper Devonian strata 1 - 5.0km thick Lower Devonian and Lower Palaeozoic strata gneissose crystalline basement at depths of 3 - 6.0km high-grade metamorphic basement of pyroxene granulite facies at depths greater than 8.0km.
"Three formations have been recognised, the Dunoon Phyllite, the Beinn Bheula Schist and the Bullrock Greywacke, of which the Dunoon Phyllite appears to be the oldest."
"On the coast north of Cove, a change from blue-grey phyllites to greenish grey cleaved siltstones marks the contact of the Dunoon Phyllite with the Beinn Bheula Schist."
"The southern boundary of the formation is taken at a rapid transition from dark phyllites with limestone lenses to a sequence of coarse, pebbly greywackes, assigned to the Bullrock Greywacke."
"Greywackes in the Dunoon Phyllite are mainly confined to the southern part of the outcrop and usually occur as separate, graded beds."
"The pebbly greywackes contain only minor amounts of potash feldspar granules, a feature which distinguishes them from the pink-tinged, more feldspathic pebbly greywackes of the Bullrock Greywacke."
"The Bullrock Greywacke consists mainly of pink-weathering cleaved feldspathic pebbly greywacke, interbedded with green cleaved siltstone."
"Farther south-west in Cowal, black slates and limestones within the Bullrock Greywacke outcrop are placed in a separate lithostratigraphical unit, the Innellan Group."
The sedimentary character of most of the Dalradian rocks is consistent with deposition in submarine fans by turbidity currents and mass flow.
"In terms of the models proposed for submarine fans by Middleton and Hampton, it is inferred that the Bullrock Greywacke was laid down in an inner - or mid-fan environment."
The portion of the Beinn Bheula Schist which is present in the Greenock district may have been deposited on the outermost parts of a fan.
"The Dunoon Phyllite appears to have been laid down in a more distal situation, perhaps in an interfan environment."
"The Dalradian rocks lie within the Tay Nappe, a major recumbent Fl structure which dominates the Southern Highlands."
"An overall change in younging direction takes place close to the southeast margin of the Dunoon Phyllite, inverted beds predominating to the north-west and right-way-up strata being more usual to the south-east."
"Within and immediately NNW of the Dunoon Phyllite outcrop, Si and S2 may combine to form a composite fabric which is represented on the map as a single cleavage."
"All the Dalradian rocks in the district have been affected by a still later deformational event, which, by correlation with the structural sequence in the adjoining Ben Lomond district, is termed D4."
"They may, however, relate to movements on fractures in the Highland Boundary Fault-system, which continued to be active during Devonian and Carboniferous times."
"Over most of this distance the Complex occurs along the south-eastern margin of the Southern Highland Group but at Loch Lomond, Upper Devonian rocks are faulted down between it and the Dalradian."
Fossil evidence from sedimentary rocks of the Complex at Aberfoyle and elsewhere indicates an Ordovocian age.
"The unconformable base of the Lower Devonian is not seen in the district but to the north-east, at Aberfoyle and Comrie, and to the south-west on Arran, the oldest strata present almost certainly belong to the Arbuthnott Group."
They have been placed in the Arbuthnott Group.
"The Inchmurrin Conglomerate is well sorted and consists of well-rounded pebbles, cobbles and boulders up to 0.2m in diameter set in a coarse sandstone matrix."
"Near the Highland Boundary Fault-system, the quartzite clasts have been deformed by brittle fracture, probably in Middle Devonian times, and in places show the effects of pressure solution where one clast impinges upon another."
"In the present district, Garvock Group sediments are exposed 6nly along the coast south of Ardmore."
"Two formations of the Strathmore Group, the Cromlix Formation and the overlying Teith Formation, are represented in the present district."
"The Cromlix Formation consists predominantly of poorly bedded, poorly sorted, silty mudstone."
"However, Armstrong and Paterson considered that it was represented by the ` lower purple sandstone facies ', the oldest of three divisions recognised in the Teith Formation in this area by Francis et al.."
The Teith Formation occupies by far the greater part of the Lower Devonian outcrop in the district.
This suggests a lower Emsian age for these strata.
"East of the Leven valley the highest beds of the formation show considerable reddening, suggesting proximity to the unconformity with the Upper Devonian."
"The quantity and coarseness of the fan material, represented by the conglomerates in the Arbuthnott and Garvock groups, suggests that deposition of these formations took place in the vicinity of scarps controlled by major growth faults."
"Erosion in Lower Devonian times, following uplift to the north on faults now concealed beneath later Lower Devonian strata, may partly explain the absence of the Dunnottar and Crawton groups and part of the Arbuthnott Group."
"While the finer-grained parts of the Garvock and Strathmore groups were being laid down, it is clear that the basin margin had migrated some distance to the north-west, to a position within the south-east Highlands."
"During deposition of the Cromlix Formation, which has been interpreted as a playa lake deposit, the axial component of the drainage would appear to have greatly diminished, possibly as a result of more arid climatic conditions."
"Axial drainage was re-established during deposition of the Teith Formation, as a result either of renewed uplift of the Highland source areas or of increased rainfall: the environment was predominantly one of meandering streams on a broad floodplain."
"Strata consisting mainly of red-brown, commonly pebbly, cross-bedded sandstones and subordinate conglomerates formerly referred to the Upper Old Red Sandstone are now assigned to the Stratheden Group."
"The top of the group is taken at the base of the Kinnesswood Formation, a sequence of cornstone-bearing sandstones and silty mudstones previously placed in the Upper Old Red Sandstone."
"At Wemyss Bay the formation is overlain, with an erosive contact, by the coarse-grained Skelmorlie Conglomerate."
"In the upper part of the formation, the grain size diminishes, there are beds of coarse pebbly sandstone and the conglomerate passes gradationally into the overlying Kelly Burn Sandstone Formation."
The Skelmorlie Conglomerate is considered to have been laid down as an alluvial fan deposit by braided rivers.
"The clast composition indicates that, in all probability, the source rocks consisted of conglomerates and lavas or lava-conglomerates of Lower Devonian age, in addition to Dalradian metasediments."
The great bulk of the Stratheden Group south of the River Clyde is assigned to the Kelly Burn Sandstone Formation.
"The Kelly Burn Sandstone Formation as a whole is considered to have been laid down by a braided river system, which, as indicated by the cross-bedding directions, flowed generally towards the north-east."
"The source-terrain of the sandstones apparently was composed largely of Dalradian metasediments which, however, were still partly covered by Lower Devonian rocks or by strata deposited earlier in the Stratheden Group period."
"The formation is best exposed south of the present district, along the shore between Seamill and Fairlie, and in the glens of Fairlie and Kelburn, where it passes gradationally into the succeeding Fairlie Sandstone Formation."
"Here, beds of cross-laminated sandstone with scattered quartz pebbles and green siltstone clasts alternate with beds in which the sandstones display a close flat lamination similar to that which characterises the Knox Pulpit Formation of central Fife."
"In the Largs Borehole, white cross-bedded pebbly sandstones lying beneath cornstone-bearing strata of the Kinnesswood Formation, may belong to the Fairlie Sandstone Formation."
"In the Helensburgh -- Dumbarton area, the Rosneath Conglomerate is well exposed along the foreshore between Rosneath Point -LSB- NS 275 805 -RSB- and Kilcreggan."
"On earlier maps of the Greenock district, conglomerates at Cardross -LSB- NS 335 774 -RSB- and Overtoun Muir -LSB- NS 370 800 -RSB- and some of those on Ardmore peninsula -LSB- NS 315 785 -RSB- were placed in the Lower Old Red Sandstone."
In these respects they more closely resemble the Rosneath Conglomerate than any Lower Devonian rocks in the neighbourhood.
The quartzite clasts are considered to have been derived from Lower Devonian conglomerates and the fact that a number of them have been split and subsequently abraded is evidence that they have been recycled.
The lower part of the Stockiemuir Sandstone Formation consists of red-brown fine-grained cross-bedded quartzose relatively mature sandstones with a few pebbly beds and rare mudstone layers.
"As a result of regional uplift associated with Middle Devonian earth movements, a major east-north-east-trending intermontane basin was eroded across central Scotland."
"During the later part of the Upper Devonian, aeolian sediments were laid down in places, particularly along the axis of the main basin."
"The relatively mature Seamill Sandstone Formation, which was laid down by a generally northwards-directed drainage, and the water-laid parts of the Stockiemuir Sandstone, probably represent the deposit of the axial drainage of the main basin."
"By contrast, the coarse lithic arenites of the Kelly Burn Sandstone Formation, the Skelmorlie Conglomerate, and the bulk of the Rosneath Conglomerate, are considered to have been laid down in the more distal parts of a major alluvial fan which entered the Greenock district from the west, by way of Bute."
"However, the generally well-rounded boulders of quartzite, lava and granite are considered to have had their source in conglomerates of Lower Devonian age, as there are no other rocks of suitable composition in the area upstream of the fan."
"South-eastward palaeocurrents inferred for the Ardmore conglomerates and some beds in the lower part of the Rosneath sequence indicate deposition in another alluvial fan, which entered the main basin from the north."
"The persistence of conglomerate in the Stratheden Group in the north-western part of the Greenock district suggests that the relief of the Highland source areas which supplied the alluvial fans was maintained by contemporaneous movements on faults, probably fractures within or parallel to the Highland Boundary Fault-system."
"During deposition of the Stratheden Group, the rainfall was probably moderate and somewhat seasonal but the presence of presumed aeolian sediments in the Stockiemuir and Fairlie sandstones suggests that the rainfall and the relief may have diminished through the period."
"These formations were probably laid down throughout the entire Greenock district but prior to deposition of the succeeding Inverclyde Group were removed by erosion from the area west of a line passing through Largs and Greenock, as a result of uplift on the Largs Fault-zone."
"Rocks formerly included in the Calciferous Sandstone Measures, together with an underlying sequence of sandstones and siltstones with pedogenic carbonate at the top of the Upper Old Red Sandstone, are now assigned to two new units, the Inverclyde Group and the Strathclyde Group."
"For strata above the Hurlet Limestone the existing classification is retained, except in the Lochwinnoch area, where a local succession is employed."
"In much of the district, the Inverclyde Group comprises the Kinnesswood, Ballagan and Clyde Sandstone formations."
"The mainly arenaceous Kinnesswood Formation, at the base of the group, was formerly regarded as part of the Upper Old Red Sandstone."
"However, it is readily distinguished from the strata of the Stratheden Group by the presence of nodules and beds of concretionary carbonate of pedogenic origin, a feature which it shares with parts of the Clyde Sandstone Formation."
"Disarticulated scales of the fossil fish Bothriolepis and Holoptyckius, found in the basal conglomerate of the Kinnesswood Formation at Fairy Knowe Quarry -LSB- NS 369 789 -RSB-, near Dumbarton, are of Famennian age but they may have been reworked from older deposits."
"The grey mudstones of the Ballagan Formation commonly contain a moderately abundant fauna of ostracods, fish scraps and Modiolus, and Lingula was found at a single locality -LSB- NS 419 785 -RSB- near Renton."
"Miospore assemblages recovered from argillaceous beds in the Ballagan and Clyde Sandstone formations, penetrated by BGS boreholes at Barnhill and Loch Humphrey, sited a little to the east of the present district, are considered by Dr B Owens to indicate an upper Tournaisian age."
"Hence it is probable that at least part of the Kinnesswood Formation is of Lower Carboniferous age, although its basal part may be Upper Devonian."
"The strata of the Kinnesswood Formation consist of beds of red and white sandstone and red-brown, green-spotted silty mudstone arranged in upward-fining fluvial cycles."
"At Auchengarth -LSB- NS 190 645 -RSB-, where cross-bedding in the sandstones indicates deposition by southward-flowing rivers, a 20m sequence consisting mainly of red-brown and purple-grey silty mudstone occurs in the lower part of the Kinnesswood Formation."
The sharp basal contact of the formation with Stratheden Group sandstones and conglomerates is visible east of the bathing pool on the shore at Gourock -LSB- NS 2379 7768 -RSB-.
"North of the River Clyde, the Kinnesswood Formation is generally thicker and more arenaceous than to the south."
"On the hillslopes above Greenock, strata of the Ballagan Formation were formerly exposed in a number of stream sections now lost through expansion of the built-up area."
In ascending order they are the Knocknairshill Member.
"North of the River Clyde, the Clyde Sandstone Formation is represented by the Overtoun Sandstone Member."
The Gourock Sandstone Member is broadly similar but is distinguished by the presence of thick multistorey bodies of white pebbly sandstone.
"The Broadlee Glen Sandstone Member crops out mainly in the northern part of Leapmoor Plantation where it consists of white and cream-coloured, trough cross-stratified sandstone with thin lenticular beds of grey siltstone and abundant coalified wood fragments."
North of the River Clyde the formation is represented only by the Overtoun Sandstone Member.
The Strathclyde Group comprises the rocks lying between the base of the thick sequence of lavas and associated volcaniclastic sediments known as the Clyde Plateau Volcanic Formation and the base of the Hurlet Limestone.
"Three divisions are recognised, the Clyde Plateau Volcanic Formation, the Kirkwood Formation and the Lawmuir Formation."
"Because of earth movements and the erosion that took place towards the end of the Inverclyde Group period, the Clyde Plateau Volcanic Formation rests disconformably on strata ranging from the Clyde Sandstone Formation to the Stratheden Group."
"The lavas to the east of Lochwinnoch, which are separated from the main outcrop by the major structure known as the Paisley Ruck, may be only about 300m thick."
"Build-up of the lava pile was accompanied by regional subsidence, and after volcanic activity came to an end the volcanic formation was progressively buried beneath sedimentary rocks of late Dinantian age."
"In accordance with usual practice in the Scottish Dinantian volcanic sequences, these rocks have been classified as mugearites, although the available analyses show that they range from hawaiite through mugearite to benmoreite or trachyandesite in composition."
"Fine-grained, with accretionary lapill i, in basal 3m Mudstone, silty, purple-brown, mainly 11.16 162.38 massive Sandstone, tuffaceous, grey-purple and 7.07 169.45 purple-brown with clasts of lava and quartz In this area, east of the Largs Fault-zone, the deposit rests upon cornstone-bearing sandstones of the Kinnesswood Formation."
"Farther north, in the area west of the Largs Fault-zone between Outerwards Reservoir and Routen Bridge, the Noddsdale Volcaniclastic Beds are up to 200m thick and rest upon strata high in the Clyde Sandstone Formation."
"The lowest lavas in the Clyde Plateau Volcanic Formation form the major scarp on the east side of Noddsdale, south of the Muirshiel Fault, and can be traced northwards in the steep belt adjacent to the Largs Fault-zone on the east side of Knockencorsan Hill and in the Rotten Burn."
"From Cloch Point and Dunrod Hill to Port Glasgow, the Strathgryfe Lavas rest directly upon strata at various levels within the Clyde Sandstone Formation, with no intervening lower lava unit."
"Poorly exposed Dalmeny basalts, which appear to be overlain by volcaniclastic sediments of the Kirkwood Formation in downfaulted blocks, occupy low ground between West Gavin -LSB- NS 380 590 -RSB- and the Black Cart Water."
"Correlation with the lavas of the Renfrewshire Hills is difficult, as the two outcrops are separated from each other by the continuation of the Paisley Ruck."
"Some 6km to the east of the present district, the Glenburn Borehole showed that the basal lavas of the Beith - Barrhead sequence rest directly upon the Kinnesswood Formation."
"Hence it appears that the lower lava groups of the Renfrewshire Hills die out to the south-east, across the Paisley Ruck."
The Kirkwood Formation consists of a highly variable thickness of detrital material derived by erosion from the lavas of the Clyde Plateau Volcanic Formation.
"It rests on the uneven weathered surface of the latter and is notably diachronous, interdigitating with the Lawmuir and Lugton Limestone formations at levels ranging from below the Newton and Castlehead coals east of Howwood to below the Dockra Limestone west of Lochwinnoch."
The Lawmuir Formation includes the strata above the Clyde Plateau Volcanic and Kirkwood formations and below the Hurlet Limestone.
"The formation occurs in a belt up to 3km wide along the south-eastern margin of the district from north of Houston to Howwood and varies in thickness from less than 20m to 150m: it is absent farther to the south-west, around Lochwinnoch, where the timeequivalent strata are probably included in the Kirkwood Formation."
"The sequence in the lower part of the Lawmuir Formation shows marked lateral variation, but in the upper part the strata are organised in generally upward-coarsening cycles."
"The Newton Coal is the lowest of the seams which, at Johnstone, just east of the district, combine to form the Quarrelton Thick Coal, the others being the Castlehead Lower and Upper coals."
They are absent under the Howwood Syncline but form a diminished representative of the Quarrelton Thick Goal around Kilbarchan.
The strata above the Castlehead Upper Coal are mostly sandstones but include three variable coals.
A marine band that occurs in a thin mudstone about 10m below the Dykebar Limestone is the lowest fossiliferous horizon above the Clyde Plateau Volcanic Formation.
"The Dykebar Limestone is generally represented by a massive calcareous mudstone with a marine fauna of bivalves and brachiopods including, in particular, Spirifer cf. crassus."
It lies about 30m below the Hollybush Limestone.
"The intervening strata consist largely of the Dykebar Marls -- a sequence of poorly bedded, variegated mudstones locally containing clusters of sphaerosiderite grains and with roots in places."
The Sandholes Coal is only recognisable north of Kilbarchan.
"It is up to 1.15m thick in several leaves, lies 12m to 20m below the Hollybush Limestone and was mined to some extent at its type locality -LSB- NS 412 643 -RSB-."
The Hollybush Limestone consists of two or more beds of Limestone within several metres of calcareous mudstone that are visible in two old quarries -LSB- NS 412 666: NS 411 606 -RSB- and in the River Gryfe -LSB- NS 399 657: NS 415 664: NS 416 663 -RSB-.
They contain the lowest rich marine fauna in the Carboniferous of western Scotland.
"Between the marine beds and the variable Lady Ann Coal, which in places in 0.66m thick, are 10m of sandstone and 2m of seatrock."
The Blackbyre Limestone consists of 2 to 5m of limestone with bands of calcareous mudstone.
"It lies close below the Hurlet Coal, and locally has been leached and affected by the roots of the coal-forming plants."
The Blackbyre Limestone contains a rich marine fauna including corals such as Diphyphyllum and brachiopods such as Echinoconchus cf. punctatus and Pleuropugnoides.
Up to 5m of seatclay separate it from the Hurlet Coal.
"The Hurlet Coal is a low-quality, pyritous seam up to 1.5m thick, locally in leaves."
"The mudstone between it and the Hurlet Limestone is known as the Alum Shale because it was exploited for alum at Lennoxtown, north of Glasgow."
A layer of basaltic tuff and agglomerate which underlies the Hurlet Limestone in the Howwood area may replace the Hurlet Coal in places.
"The Lower Limestone Group occurs only in the south-east of the district, between Bridge of Weir and Kilbarchan, in the Howwood Syncline, and at Lochwinnoch."
"Information comes largely from boreholes, supplemented by stream sections in the River Gryfe and Locher Water and by quarries in the Hurlet Limestone in the Howwood Syncline."
The base of the unit was formerly taken at the base of the Hurlet Coal but is now drawn at the base of the Hurlet Limestone: the top is at the top of the Top Hosie Limestone.
"The limestones which give the group its name are marine and up to seven in number, excluding the limy ironstones just below the Blackhall Limestone, which contain only ostracods and fish debris."
"The Hurlet Limestone, which varies in thickness from 1.7 to 12.7m, consists of argillaceous shelly limestone with calcareous mudstone partings: to the east of the district, in the Paisley area, it is generally a crinoidal limestone less than 1m thick."
Most of the limestones are composed largely of crinoid columnals but the Top Hosie Limestone is very argillaceous with scattered shell and crinoid debris.
"Clayband ironstones are scattered throughout the sequence, occurring in abundance just below the Blackhall Limestone and midway between it and the Main Hosie Limestone."
"A more persistent seam, the Lillie 's Shale Coal, normally consists of 0.2m of coal on 0.2m of cannel or cannelly mudstone but reaches 0.2m of coal on 0.25m of ` shale ' in the Locher Water -LSB- NS 402 648 -RSB- and 0.4m of coal on 0.45m of ` shale ' in a nearby borehole -LSB- NS 421 658 -RSB-."
"The limestones and associated mudstones are marine and some, such as the Neilson Shell Bed above the Blackhall Limestone, yield rich faunas."
Such faunas occur particularly between the Hurlet Limestone and the Blackhall Limestone.
"The Hosie Sandstone, which most unusually for a Scottish Carboniferous sandstone contains a marine fauna, mainly of brachiopods, is represented by a bed of silty sandstone below the Main Hosie Limestone."
"Only the upper part of the Lower Limestone Group, referred to the Lugton Limestone Formation, is present."
"The Dockra Limestone, which lies near the base in the Lochwinnoch area, is equivalent to the Blackhall Limestone of the Kilbarchan -- Howwood area and there is no local representative of the Hurlet Limestone."
"In the Lora Burn Borehole, the Dockra Limestone is about 15m thick and consists of medium-grey calcareous mudstone which passes upward into dark grey argillaceous limestone."
"The strata overlying the Dockra Limestone, consisting mainly of interbedded mudstones and limestones, are equivalent to the Hosie limestones elsewhere in the Greenock district."
"A rooty bed of variable thickness, at the position of the Lillie 's Shale Coal, divides the sequence into two units."
The top of the Lugton Limestone Formation is taken at the top of the uppermost of the Hosie limestones.
The strata consist of dark grey bedded mudstones very similar to those in the underlying Lower Limestone Group.
"They include several clayband ironstones, the thickest of which is the Johnstone Clayband Ironstone."
"The immediately overlying mudstones contain alternating developments of Lingula squamiformis and Naiadites, in places in very close association, but the mudstones around and above the Johnstone Clayband Ironstones are usually barren."
"The strata overlying the Lugton Limestone Formation consist mainly of mudstones with a number of thin ironstone bands, most notably the Dalry Clayband Ironstone, which lies at the horizon of the Johnstone Clayband Ironstone."
"The Johnstone Shell Bed, a widespread marine horizon, is also present in the Lochwinnoch area and is useful in relating the sequences of the Greenock district with those developed to the south, in Ayrshire."
"The sediments of the Kilbirnie Mudstone Formation are succeeded by a sequence of mudstone, siltstone, sandstone, seatrock and coal, arranged in cycles."
These strata are assigned to the Dalry Sandstone Formation.
"Grey mudstone with Lingula exposed here is considered to be the local representative of the Black Metals Marine Band, a prominent marker horizon in the Paisley district."
"Clayband ironstone nodules and beds within the mudstone, referred to in Ayrshire as Logan 's Bands, locally reach workable thickness in the Lochwinnoch area."
"Towards the top of the Dalry Formation, coals, known locally as the ` Peel Coals ' and tentatively correlated with the Main and Smithy coals of north Ayrshire, attain workable thickness and have been mined in places."
"After a period at the end of Stratheden Group times during which local erosion took place, sedimentation in the districtresumed as a result of renewed regional subsidence."
"The early Carboniferous basin was more extensive than that in which the Upper Devonian was laid down, and in large parts of the southern Midland Valley the basal beds of the Inverclyde Group overlap the entire Stratheden Group to rest upon rocks of Lower Devonian age or older."
"The thick, relatively arenaceous Kinnesswood Formation of the Helensburgh -- Dumbarton area was probably laid down by braided rivers which flowed into the basin from the north-west."
"As a result, the Ballagan Formation was laid down in a shallow-water environment with restricted access to the open sea, subject to marked changes of salinity and periodic desiccation."
"Just as the onset of marine conditions was gradual, so also was the resumption of fiuvial sedimentation towards the end of Ballagan Formation times, probably as a result of rejuvenation of the upland source areas."
"Deposition of sandstones probably commenced first in the north-western part of the Greenock district but gradually extended southwards and eastwards over the Ballagan Formation mudflats, with the result that the base of the Clyde Sandstone Formation is strongly diachronous."
The abundance of calcrete in the Kinnesswood Formation and lower part of the Clyde Sandstone Formation is consistent with a climate having a mean annual temperature of about 160C and a moderately seasonal rainfall.
"As a result of the reducing conditions thereby introduced, the strata of the Overtoun Sandstone Member and Broadilee Glen Sandstone Member are generally grey in colour and contain much finely disseminated carbon as well as plant debris."
Deposition of the Clyde Sandstone Formation in the Greenock district was brought to an end by uplift caused by east -- west compressional stresses.
"In the core of one of these folds, the Leap Moor Syncline, the thickest Inverclyde Group sequence is preserved."
"As a consequence, the volcanic rocks of the Strathclyde Group locally rest upon the Kinnesswood Formation."
"After eruption of the lavas and tuffs of the Clyde Plateau Volcanic Formation, the volcaniclastic Kirkwood Formation initially began to accumulate in late Dinantian times on low ground within and adjacent to the thick volcanic pile of the Renfrewshire Hills."
"The deposits of the lower part of the Lawmuir Formation consist largely of quartzose sand, but include some volcaniclastic material because the lavas remained uncovered in places till almost the whole of the formation had been laid down."
These attained their maximum extent towards the end of Dinantian times.
"The oldest were probably emplaced during the Lower Devonian, about 400 million years ago, into the Dalradian rocks of the south-west Highlands."
"The youngest were intruded about 52 million years ago, during the Tertiary period."
The most extensive and varied suite of intrusions relates to the early Carboniferous eruptive episode which gave rise to the Clyde Plateau Volcanic Formation.
Two north-east-trending dykes cutting Dalradian rocks have been classed as lamprophyre and are considered to be of Lower Devonian age.
"Large numbers of minor intrusions, both within the Clyde Plateau Volcanic Formation and in the underlying sediments have strong petrological affinities with the volcanic rocks and are assumed to be contemporaneous with them."
"Outwith the centre, plugs are difficult to identify within the mainly basaltic succession of the Clyde Plateau Volcanic Formation, owing to the close correspondence in rock type between lavas and intrusions."
"Four basaltic vents, cutting the Devonian and Carboniferous sediments beneath the volcanic rocks, have been recognised in the area south of the Clyde."
"North of the River Clyde at Dumbarton, a group of vents cutting Lower Carboniferous sediments lies at the southwestern end of the Dumbarton -- Fintry line of volcanic centres."
"North of the River Clyde, dykes are abundant close to the vents of the Dumbarton area, in the Murroch Burn and south-west of Renton, where they are intruded into rocks of the Kinnesswood and Ballagan formations."
"A persistent north-east-trending dyke, which crops out on both sides of the Gare Loch at Shandon, has textural similarities to the Lower Carboniferous dykes and has been classed tentatively as a dolerite of transitional Markie/Dunsapie type."
"An irregular sheet-like body of medium-grained dolerite crops out on Knockencorsan Hill -LSB- NS 240 666 -RSB-, where it is seen to cut Inverclyde Group sediments and the Noddsdale Volcaniclastic Beds on opposite sides of a NW -- SE fault."
"At Craigmuschat -LSB- NS 240 775 -RSB-, Gourock, a westward-dipping lenticular body, up to 100m thick, of heavily altered, haematite-stained feldsparphyric trachyte is intruded into sandstones of the Kinnesswood Formation."
"The most extensive sill is intruded slightly discordantly, close to the boundary between the Stratheden and Inverclyde groups."
A number of east -- west or ENE-trending quartz-dolerite dykes in the district are part of a major swarm of late Westphalian to early Stephanian age.
"In the district they are only seen to cut the Clyde Plateau Volcanic Formation and older rocks, but elsewhere in central Scotland the swarm cuts Middle Coal Measures."
A sill-complex consisting of several leaves of ophitic olivine - dolerite is intruded into the Lawmuir Formation in the south-east corner of the district.
The stratigraphical level at which the sill is emplaced ranges from below the Castlehead Lower Coal to just above the Hollybush Limestone.
"Several leaves of the complex, cutting deformed strata within the Paisley Ruck, were proved in a borehole north-east of Howwood -LSB- NS 405 612 -RSB- and, in eastern Glasgow, sills of similar composition cut the Middle Coal Measures."
"The structural history of the Greenock district can be traced from the early part of the Caledonian Orogeny, in late Precambrian times, to the end of the Palaeozoic Era."
"During the early part of the Caledonian Orogeny, in what has been termed the Grampian event, the Dalradian rocks were deformed into a series of major folds."
The date of initiation of the important Highland Boundary Fault-system is unknown but it has been suggested that it already existed as a basement fault during deposition of the Dalradian.
"The varied assemblage of rocks known as the Highland Boundary Complex, which includes strata of Middle Ordovician age, was juxtaposed against the Dalradian in late Ordovician or earliest Silurian times."
There is no evidence in the district which relates to sedimentary or structural events during the Silurian period but late - Silurian sediments a little to the south at Farland Head -LSB- NS 178 484 -RSB- are generally fine grained and show no sign of having been deposited in the vicinity of a highland front.
"During the Lower Devonian, however, the Greenock district was part of a major north-east-trending subsiding basin centred on the Midland Valley and flanked to north and south by upland areas."
"Palaeomagnetic measurements indicate, however, that the Highlands and the Midland Valley have occupied similar positions in relation to each other since Ordovician times."
It is likely that the input of coarse detritus into the Midland Valley basin during the Lower Devonian was maintained by rejuvenation of the Highland source area by intermittent uplift on the Highland Boundary Fault-system.
"Although Lower Devonian strata almost certainly encroached upon the Highlands, it is probable that in the Greenock district they do not now extend beyond the line of the South Inchmurrin Fault and its inferred south-westwards extension."
"During the Middle Devonian, compressive earth movements brought about marked changes in the palaeogeography of central Scotland."
The Lower Devonian rocks were folded into north-east-trending structures and there were major thrust movements on elements of the Highland Boundary Fault-system.
"The Lower Devonian within the basin was deeply eroded, particularly along anticlinal axes, and continuing uplift prevented the deposition of any Middle Devonian sediments."
"During most of the Upper Devonian period, tectonic activity was subdued."
"Deposition of the Stratheden Group took place under conditions of gentle regional subsidence, with intermittent uplift of the Highlands on fractures within the Highland Boundary Fault-system."
"Uplift to the west, similar to that which affected the Corloch Fault on north Arran, caused the removal by erosion of any Upper Devonian strata."
"Within the basin, there was upthrow to the west on the Largs Fault-zone, an important north-north-east-trending belt of fractures which was to play a major role in Carboniferous times."
The upper-most portion of the Stratheden Group in the western part of the district was removed by erosion and the earliest Inverclyde Group strata locally succeed unconformably.
Deposition of the Inverclyde Group in the Midland Valley in early Carboniferous times took place under quiet tectonic conditions.
Slow regional subsidence continued and the floodplain deposits of the Kinnesswood Formation were progressively covered by coastal sabkha sediments of the Ballagan Formation.
"Towards the end of Inverclyde Group times, the sedimentary sequence within the Greenock district began to be affected by east -- west compressive movements."
"Within the district, the lavas and associated volcaniclastic sediments at the base of the Strathclyde Group rest upon an eroded surface of rocks which range from high in the Clyde Sandstone Formation to the Kinnesswood Formation."
This widespread early Carboniferous volcanicity may relate to a tensional phase initiated as a reaction to the preceding compression.
"To the east, in the Glasgow district, most of the Clyde Plateau Volcanic Formation can be related to north-east-trending lines such as the Dumbarton -- Fintry line."
"The differences between the lava sequences in the Renfrewshire Hills, the Beith -- Barrhead area and the Kilpatrick Hills may be due in part to differential movements of blocks bounded by major crustal fractures, such as the Clyde Fault and the Paisley Ruck."
"Earth movements during the late Carboniferous gave rise to faults, most of which fall within one of four principal trends: north -- south, east -- west, NE -- SW and NW -- SE."
"The North Inchmurrin and Rosneath faults were active, rocks of Upper Devonian and early Carboniferous age being let down between them in a graben - like structure."
"Among other important NE -- SW structures of later Carboniferous age are the Camis Eskan Graben, north of the Clyde, the faulted syncline centred on the Spango valley and the complex Paisley Ruck."
"It is probable that most of the east -- west faults, some of which are intruded by quartz-dolerite dykes, were in being by the end of the Carboniferous period."
At least some of the east -- west faults may have been active during Permian or later times as they apparently displace the olivine-dolerite sills of the Kilbarchan area which are considered to be of early Permian age.
"Members of the group, such as the Kilbarchan Fault, cause major displacements of the upper boundary of the Clyde Plateau Volcanic Formation and of the early Permian olivine-dolerite sill-complex."
The faults of this group belong to a major fracture system which was probably initiated in the late Carboniferous but which continued to be active during Permian and later times.
"They may have controlled some of the late Palaeozoic magmatism in the Midland Valley and undoubtedly controlled the siting of important mineral veins, as at Muirshiel, which are possibly of Mesozoic age."
"The Greenock district was last entirely occupied by ice in late Devensian times, when an ice-sheet, which reached its farthest limits at about 18 0 years Before Present, covered Scotland and northern England."
"At the start of the climatic amelioration, the margin of the late Devensian ice-sheet still lay south and west of the present district."
"During the Flandrian, alluvial deposits were laid down by streams and rivers, and were terraced as the drainage adjusted to changes of sea-level."
"The principle valleys in the district, many of which have a general north-south or NW-SE trend, were doubtless scoured and deepened by ice on more than one occasion during the Quaternary Era."
"In the Helensburgh -- Dumbarton area and along the coast south of the Firth of Clyde, the till is usually clayey, grey-brown in colour, and contains clasts mainly of Dalradian rock types."
"Farther east, the till is brown or red-brown in colour and contains angular blocks of Upper Devonian sandstones and conglomerates, and lavas and sandstones of Carboniferous age."
Examples include small ridges of sand and gravel containing pebbles mainly of Carboniferous lava a little south of Kilmacolm -LSB- NS 359 679 -RSB- and north of Bridge of Weir -LSB- NS 394 668 -RSB-.
"It has recently been proposed that the younger, colder part of the Clyde Beds should be assigned to the Balloch Formation and that the older, less frigid part be subdivided into a lower Paisley Formation, consisting of colour-laminated clays and silts, and an upper Linwood Formation, composed mainly of grey silts and clays."
A thin layer of shelly bouldery gravel intervening between the Linwood and Balloch formations has been termed the Inverleven Formation.
The lower part of the Paisley Formation tends to be coarser than the upper part and contains laminae with small angular rock fragments.
"Larger rock clasts, up to 0.1m long, scattered through the deposit, and occurring also in the overlying Linwood Formation, were probably dropped in from floating ice-masses."
"Currently, the Paisley Formation is exposed only in the Geilston Burn, Dumbarton -LSB- NS 341 777 -RSB-, where it is about 0.6 in thick."
"In the Linwood Borehole, samples of the Paisley Formation contained no macrofossils or ostracods."
"This deposit is immediately overlain, not necessarily conformably, by a freshwater deposit which, although considered to be Flandrian, contains in addition to the gastropods Gyraulus laevis and Lymnaea peregra the cold water bivalve Pisidium obtusale lapponicum."
"At Geilston Burn, a sequence up to 4m thick of fossiliferous grey silts and clays resting upon the Paisley Formation is here referred to the Linwood Formation."
"From the radiocarbon dates yielded by shells incorporated in morainic deposits of the Loch Lomond Stadial south of Loch Lomond and at Rhu -LSB- NS 265 840 -RSB-, it may be inferred that the Linwood Formation was also laid down in Loch Lomond and the Gare Loch."
"On the whole, the Linwood Formation is much better known in the areas immediately west and east of the present study area where there have been a number of rewarding excavations."
"The faunas tend to be significantly more diverse than in the Paisley Formation, with individual species occurring in greater abundance."
"When deposition of the Linwood Formation commenced, in the period after about 12 800 BP, the sea was still considerably higher than at present but was falling as a result of isostatic uplift."
"The latter are best developed in the Vale of Leven south of Loch Lomond, where they rest upon a thick series of marine silts and clays, the Balloch Formation, which is considered to represent the early, distal outwash from the Loch Lomond glacier."
"Evidence from boreholes at Balloch and Inverleven in the Leven valley indicates that the sea may have been at a level considerably below OD at the beginning of the period but rose during deposition of the Balloch Formation to a position above present sea-level, perhaps by about 10300 BP."
"South of Loch Lomond, the till locally contains shells derived from deposits of Linwood Formation traversed by the glacier during its passage down the loch."
"Thus, the discovery in till near Helensburgh on the Gare Loch, of blocks of Linwood Formation containing shells, including Arctica islandica, which have yielded radiocarbon dates of 11 700 BP and 11 0 BP, suggests that the maximum position reached by the Gare Loch glacier was some distance beyond the ice-limit marked by the moraine ridges at Rhu."
"As shown by the Balloch Borehole, the terraced outwash rests upon the marine silts and clays of the Balloch Formation."
"Outwash deposits related to a glacier of this period are present also in the Gare Loch at Rhu, where glacially deformed marine silts and clays are overlain by up to 4m of fluvioglacial sand and gravel which is capped by Flandrian beach deposits -LSB- NS 265 840 -RSB-."
The former penetrated 3g.
of brown clay and silt to which the name Balloch Formation has been given.
"This rested, at a depth of 39m below OD, upon a thin layer of shelly bouldery gravel termed the Inverleven Formation."
Shell material from the Inverleven Formation has yielded radiocarbon dates of 11 960 BP and 10 350 BP at Inverleven and 10920 BP at Balloch.
"The oldest of these suggests the possibility that the gravel layer is, in part, a lag deposit produced as tidal currents reworked the Linwood Formation which formerly occupied the buried channel of the Leven valley."
Advance of a glacier into the loch would have progressively reduced the tidal scour in the Leven valley and eventually allowed deposition of the overlying clay and silt of the Balloch Formation seaward of the glacier.
"Thus, in the western part of the Garvel Park Dock, grey silts and clays contain a boreal fauna of Windermere Interstadial type and are probably Linwood Formation."
"At the eastern end of the dock, grey silts and clays with a gravelly layer at the base reached a depth of about 11m below GD: the fauna, which includes P. arctica, indicates that the deposits are probably referable to the Balloch Formation."
"Erosion of a deep channel in response to a lowering of sea-level at, or just before, the start of the Stadial would explain the evidence from the Vale of Leven where the Inverleven Formation, with a radiocarbon date of 10920 BP, occurs to a depth of more than 50m below OD in the Inverleven Borehole, whereas the older Linwood Formation is apparently present at a much shallower depth in the nearby borehole at Dumbarton Distillery."
"The sea is considered to have risen during the Stadial, while the Balloch Formation was being laid down, to culminate at a position above OD before the end of the period."
This continued into early Flandrian times.
The rock platform is usually covered by a thin veneer of beach sand and shingle of Flandrian age and in the past has been dated to this period.
Several of a series of boreholes drilled recently during site investigations for a proposed outfall sewer east of Gourock Bay -LSB- NS 254 775 -RSB- also proved red-brown till resting upon a rock platform and overlain by Flandrian raised beach deposits.
The landscape of the Greenock district has been little modified during the 10000 years since the start of the Flandrian Stage.
"From evidence outwith the area, the sea is known to have fallen during the early part of the Flandrian."
In the Greenock Outfall Borehole No. 20 -LSB- NS 2624 7786 -RSB- the fauna appears to be predominantly Flandrian but the presence of the cold water bivalve Yoldiella fraterna confirms that at least some of the material is derived.
Within the Greenock district the Flandrian transgression is considered to have reached a height of 14m above OD at Rhu and about 15m above OD at Loch Lomond.
"During the period of marine regression in the early part of the Flandrian, peat developed on low ground around Linwood, a little east of the district."
"Outside the trachytic centre, in the overlying basaltic sequence, baryte veins and irregular pods are closely associated with major ESE-trending faults or with east -- west - or ENE-trending late Carboniferous quartz-dolerite dykes."
"Copper occurred as disseminations of malachite in the Clyde Sandstone Formation at two localities south of Gourock, Drumshantie -LSB- NS 240 766 -RSB- and Larkfield -LSB- NS 249 762 -RSB-."
"Hydrothermal activity was obviously prevalent during eruption of the Clyde Plateau Volcanic Formation and may even have occurred earlier, as indicated by the presence of copper in sediments near Gourock."
"However, many veins follow ENE - to ESE-trending faults and some permeate late Carboniferous quartz-dolerite dykes, as at Kaim."
These baryte and copper veins probably relate to an episode of late Carboniferous or early Permian hydrothermal activity which was responsible for the emplacement of many veins of similar type in central and southern Scotland.
"However, there is little evidence in north-west Europe of hydrothermal activity during this period, and it is possible that the mineral veins and the dykes were injected at different times into a system of fractures which may date from late Carboniferous times."
"Radiometric, suggest that the main phase of the mineralisation may have occurred during the Triassic period and was approximately contemporaneous with the emplacement of baryte at Strontian, in Glen Sannox and in northern England."
"The potential resources of crushed rock aggregate in the area are restricted to the metamorphic rocks in the Rosneath peninsula and north-west of Helensburgh, the lavas of the Clyde Plateau Volcanic Formation in the Renfrewshire Hills, and dolerite and trachyte intrusions."
"The lavas of the Clyde Plateau Volcanic Formation, in the area to the south of the Clyde, are mainly of basic composition and are included in the ` Basalt ' Group of the British Standard Group Classification for roadstone."
"some 15 -- 20m thick, intruded in Lower Carboniferous sediments, is currently being worked in a large quarry -LSB- NS 409 635 -RSB- near Kilbarchan."
"In the district, limestone occurs in the Lower Limestone Group and the Lawmuir Formation, in the Ballagan Formation, and in the Kinnesswood Formation."
There are also thin beds of limestone in the Dunoon Phyllite.
"The Hurlet Limestone, a shaly limestone up to 12.7m thick at the base of the Lower Limestone Group, was worked extensively near Bridge of Weir -LSB- NS 399 659 and NS 399 654 -RSB- and in the Howwood area."
"Although it is much thinner, the Hollybush Limestone in the Lawmuir Formation was worked in quarries -LSB- NS 412 666 -RSB- in the same area."
Limestone in the Ballagan Formation was worked for local agricultural purposes near Camis Eskan -LSB- NS 335 821 -RSB-.
"Limestone in the Kinnesswood Formation has been worked near Carman Reservoir -LSB- NS 381 787 -RSB-, at Inverkip -LSB- NS 205 718 -RSB- and in Shielhill Glen -LSB- NS 240 720 -RSB-."
There were also small workings in thin limestone bands within the Dunoon Phyllite in Glen Fruin.
The clays and silts of the Linwood Formation in the area to the east of the district have been extensively used in the manufacture of bricks and tiles.
"Within the district, the Linwood Formation and the lithologically similar Balloch Formation are mainly confined within the buried channels of the Clyde and Leven."
"Similar mudstones, but without the dolomitic limestone bands, occur in the Lower Limestone Group and in the Lawmuir Formation, near Bridge of Weir."
"Bright red or carmine sandstone from the Stratheden Group near Renton -LSB- NS 386 791 -RSB-, Bonhill -LSB- NS 398 787 -RSB- and Dumbarton -LSB- NS 388 760 -RSB- was used locally for houses and churches."
"The Kinnesswood Formation provided a pale red to grey freestone near Helensburgh -LSB- NS 311 840, NS 313 830 -RSB- and at Dumbarton -LSB- NS 391 753 -RSB-."
"White sandstone of the Clyde Sandstone Formation was worked for local housing in Gourock, Greenock and Port Glasgow."
"The Hurlet Coal at the top of the Lawmuir Formation was worked near Bridge of Weir and at Howwood, and the alum shale in the roof of the coal was probably worked at the same time."
The Sandholes Coal at Sandholes -LSB- NS 414 644 -RSB- and the Quarrelton Thick Coal near Kilbarchan were also exploited to a small extent.
"The Lillie 's Shale Coal of the Lower Limestone Group, which contains a seam of oil shale as well as coal, was probably mined more than 100 years ago in the area between Houston and Kilbarchan."
The Johnstone Clayband Ironstone was extensively mined over a century ago in the Saudholes basin -LSB- NS 40 60 -RSB- but the clayband ironstones of the Lower Limestone Group do not appear to have been exploited.
"The best prospects for groundwater are considered to be the sandstones of the Stratheden and Inverclyde groups, from which yields of up to 10 litres per second might be expected."
"The 36m of strata drilled below the base of the Kinnesswood Formation in the BGS ` Tak-ma-doon ' Borehole -LSB- NS 7291 8053 -RSB-, Figure 3, have been assigned to the Stratheden Group and are thought to be of Upper Devonian age."
"There is an abrupt change at the base of the Kinnesswood Formation from red, and grey-purple medium - and coarse-grained sandstones with scattered mudstone clasts and quartz pebbles to fine - and medium-grained whitish, pale green or pink sandstones without clasts or pebbles."
"These sandstones are very similar in lithology to those assigned to the Upper Old Red Sandstone which occurs at the same stratigraphic horizon along the northern side of the Gargunnock Hills, some 6km to the north of the present area."
Almost the entire area of the Airdrie District is underlain by strata of Carboniferous age.
"These strata, which are mainly red and white sandstones with thin beds of concretionary limestone, were deposited in an environment transitional between the arid or semi-arid conditions in which the red fluvial and aeolian sandstones of the Upper Devonian were laid down and the humid environment in which the mainly grey fluviodeltaic and marine Carboniferous rocks were deposited."
"Thus, the name Lower Limestone Formation, replaces the term Lower Limestone Group."
"This part of the succession includes all the strata up to base of the Hurlet Limestone, traditionally taken as the top of the Calciferous Sandstone Measures."
This has been renamed the Lower Limestone Formation and has been placed in the Clackmannan Group.
Two marine bands and several Lingula bands are present but marine limestones do not occur in these rocks which are referred to the Limestone Coal Formation.
"Stratigraphically above is a succession of dominantly arenaceous cyclotherms with mudstones, marine limestones and thin coals forming the Upper Limestone Formation."
"The Lower Limestone Formation, the Limestone Coal Formation, the Upper Limestone Formation and the Passage Formation have been assigned to the newly erected Clackmannan Group."
"The Lower, Middle and Upper Coal Measures are considered to be informal units and are placed in the Coal Measures."
"The Ballagan Formation is placed in the CM miospore zone, the earliest zone which can be recognised in Scotland."
At least two lower Carboniferous zones can be recognised elsewhere: in this area these lower zones are thought to be represented by at least the top part of the unfossiliferous Kinnesswood Formation.
This goniatite has not been found in Scotland and the base of Lower Coal Measures has been taken at a suitable arbitrary position which within the present district is the Lowstone Marine Band.
"The Lower Carboniferous strata are assigned to the Inverclyde Group comprising the Kinnesswood Formation, the Ballagan Formation and the Clyde Sandstone Formation: the Strathclyde Group consisting of the Clyde Plateau Volcanic Formation, the Kirkwood Formation, and the Lawmuir Formation: and the Lower Limestone Formation, the lowest of the Clackmannan Group."
"These are assigned to the Kinnesswood Formation, the lowest unit of the Inverclyde Group."
"The only good exposures of Kinnesswood Formation strata within the present district occur in the Garrel Burn, about 2km north of Kilsyth."
"The top 50m of the Kinnesswood Formation, seen further up stream, comprises medium-grained red-yellow and grey-purple sandstones interbedded with dark red or purplish fine-grained sandstones, siltstones and mudstones."
A complete sequence of the Kinnesswood Formation was drilled nearby in the BGS Tak-ma-doon Borehole -LSB- NS 7291 8053 -RSB- where the thickness was found to be 146m.
"The succeeding Ballagan Formation, consisting of grey mudstones with thin nodular beds of dolomitic limestone, was deposited in a coastal plain environment subject to fluctuating salinity and periodic dessication."
There are no good natural sections of Ballagan Formation strata in the present district.
"The BGS Tak-ma-doon Borehole -LSB- NS 7291 8053 -RSB- proved the Ballagan Formation to be only 20m thick in that area and 2km to the west, in the Balhille Burn -LSB- NS 707 793 -RSB-, the lowest flow of the Clyde Plateau Volcanic Formation appears to lie directly on sediments of the Kinnesswood Formation."
"The only fossils which have been found in Ballagan Formation strata in the present district are ostracods: an isolated fish scale in the Tak-ma-doon Borehole and one occurrence of an algal limestone with ? The sandstones are coarser than those of the Kinnesswood Formation and though commonly calcareous and concretionary, do not develop TRUE cornstones."
The Clyde Sandstone Formation is only present in small areas near Fintry and south of the Carron Valley Reservoir.
South of the Carron Valley Resevoir -LSB- NS 685 832 -RSB- poor exposures of sandstones with a concretionary limestone have been assigned to the Clyde Sandstone Formation but 4km to the west they appear to be absent in the Clachie Bridge Borehole.
A period of localised uplift and erosion at the beginning of Strathclyde Group times was followed by a major volcanic episode which produced the Clyde Plateau Volcanic Formation of the Kilsyth and Cathkin Hills.
"The lavas comprising the Clyde Plateau Volcanic Formation are predominantly olivine-basalt of Markle and Jedburgh types, with subordinate trachybasalt and mugearite, and were erupted from different centres at different times."
"Elsewhere, at this time, the largely fluvial sandstones, siltstones and mudstones of the Lawmuir Formation, were being deposited."
The Clyde Plateau Volcanic Formation marks the most extensive of a series of volcanic episodes which took place during the Lower Carboniferous in the Midland Valley of Scotland.
"In contrast, on the north scarp of the Touch - Gargunnock Hills some 5km to the north, the volcanic formation apparently overlies the Clyde Sandstone Formation without angular unconformity."
These necks are thought to have been active at about the same time as the North Campsie Linear Vent System and also to be major sources of the early Jedburgh type lavas.
These necks are thought to have produced trachybasalt and Jedburgh type lavas contemporary with the second phase of effusion from the North Campsie Linear Vent System.
This system lies parallel to and about 1km to the south of the Gonachen Glen Linear Vent System.
"The stratigraphic level of this tephra deposit indicates extrusive activity immediately prior to, or contemporaneous with, the earliest flows from the Waterhead Central Volcano."
The neck on the eastern slopes of Dungoil -LSB- NS 640 842 -RSB- is not included in the linear vent system but is thought to be related to the younger Waterhead Central Volcanic Complex.
"During later stages in the vulcanicity activity became focussed in one central area, the Waterhead Central Volcanic Complex."
The tephra deposits on Meikle Bin -LSB- NS 667 822 -RSB- are part of the Waterhead Complex.
"Most lie within the linear vent systems with which they share the same trend, or are related to the Waterhead Central Volcanic complex where they lack any preferred orientation."
"Some lava may have been extruded by fissures now filled by dykes such as the one in Fin Glen, but the evidence from the Waterhead Central Volcanic Complex suggests that most of this type of lava was erupted from there, with minor additions from small necks such as the one on the north shore of Loch Carron."
"In the Forking Burn section, the base of the group rests on a thin tephra horizon which lies on sediments of the Ballagan Formation."
The group is thought to be derived from the Waterhead Central Volcanic Complex.
The petrography of the basal trachyte is very similar to that of the plug of phonolitic trachyte near Fintry -LSB- NS 614 863 -RSB- which is part of the North Campsie Linear Vent System and which may be the source of the lava.
The proximal facies sequence exposed to the north-east of Lecket Hill -LSB- NS 647 813 -RSB- suggests derivation from the adjacent Waterhead Central Volcanic Complex.
They occur in geographically isolated areas but are all considered to represent parts of the large central volcano which developed around the Waterhead Central Volcanic Complex.
"The Lower Limestone Formation is present at outcrop intermittently in a WSW-ENE belt across the northern part of the sheet, from Lennoxtown to the northeast corner."
The Lower Limestone Formation is much more uniform than the underlying Lawmuir Formation.
"Non-marine limestones with ostracods occur below the Blackhall Limestone and were formerly regarded as part of it, but the name is now restricted to the marine limestone only."
"The lowest cycle starts with the Hurlet Limestone, a crinoidal bioclastic bed that is visible at Finniescroft -LSB- NS 6232 7685 -RSB- and is usually 0.75 - 1.5m thick, but is up to 3.7m thick at Sculliongour -LSB- NS 63 79 -RSB- and up to 6.5m at Corrieburn -LSB- NS 68 79 -RSB-."
"It was quarried and mined, together with the underlying Alum Shale and Hurlet Coal, at Sculliongour and more extensively north of Milton of Campsie and south of Lennoxtown on the South Brae of Campsie."
In the Lennoxtown area 10m of mudstones occupy the whole of the interval between the Hurlet Limestone and the Shields Bed at the base of the overlying cycle.
"Indeed, in this area the Shields Bed and some clayband ironstones are the only other beds to occur in 40m of mudstones between the Hurlet and Blackhall Limestones."
The upper one is a shelly bed 1.1m thick that weathers to rottenstone -LSB- NS 6855 7924 -RSB- and lies immediately below the Shields Bed.
The Shields Bed is a sandy crinoidal limestone up to 1.34m thick which thins westwards and dies out near the western margin of the sheet.
"This interval also contains the Campsie Clayband Ironstones and, locally, at the top several beds of non-marine limestone with abundant ostracods."
This cycle occupies the interval from the base of the Blackhall Limestone to the Milngavie Marine Band.
"The Blackhall Limestone is a persistent, bioclastic, crinoidal limestone, generally 0.45 - 0.65m thick."
The mudstone above the limestone contains the Neilson Shell Bed and a few solitary corals.
"Two other deep boreholes, Bedlay No. 2 -LSB- NS 7139 7064 -RSB- and Auchinbee No. 1 -LSB- NS 7323 7566 -RSB- also reached the Blackhall Limestone."
In this last area the sandstone may be continuous with the Hosie Sandstone in the absence of the Milngavie Marine Band.
The Milngavie Marine Band shows a very varied development.
The correlation suggested therein with the Mill Hill Marine Band of west Fife is now regarded as correct.
"A crinoidal limestone 0.3m thick in Cardowan No. 13 Borehole may be the Milngavie Marine Band, but it appears to be rather high in the succession."
"It passes up through siltstone and silty sandstone into the Hosie Sandstone, a mainly medium-grained bed up to 13m thick."
The latter also has a coal 2.5cm thick just below the Main Hosie Limestone.
The top three cycles in the Lower Limestone Formation are much thinner than the preceding four.
Each starts with one of the Hosie Limestones and the Top Hosie Limestone completes the group.
"The Main Hosie cycle is 6.7 to 10.6m thick, the Mid Hosie cycle 12 to 15m and the Second Hosie Cycle 2.4 to 7m."
Sandstone does not occur at all between the Second and Top Hosie Limestones.
"The Main, Mid and Second Hosie limestones are all bioclastic and crinoidal."
"The Top Hosie Limestone is of the cementstone type, that is, highly argillaceous, fine-grained and less conspicuously fossiliferous than the other limestones."
The Main Hosie cycle has the richest fauna and is the only one to include corals and bryozoa.
"The Main Hosie Limestone is exposed in one of the headwaters of both the Spouthead burn -LSB- NS 6549 7844 -RSB- and the Banton burn -LSB- NS 7399 8026 -RSB-, and in a decalcified state in the River Carron -LSB- NS 7918 8328 -RSB-."
"The Second Hosie Limestone is visible in the Burniebrae Burn -LSB- NS 6605 7816 -RSB-, the Banton Burn -LSB- NS 7403 8021 -RSB- and the River Carron -LSB- NS 7922 8325 -RSB-."
"The Top Hosie Limestone is the best displayed in Burniebrae Burn -LSB- NS 6605 7818 -RSB-, two unnamed streamlets -LSB- NS 6750 7778, NS 6821 7808 -RSB-, the eastern burn at Corrieburn -LSB- NS 6870 7874 -RSB-, Banton Burn -LSB- NS 7403 8017 -RSB- and the River Carron -LSB- NS 7925 8324 -RSB-."
"The section is as follows: metres Top Hosie Limestone, with brachiopods and gastropods 0.3 Calcareous mudstone with productoids 0.81 Dark mudstone with Posidonia corrugata 2.19 Second Hosie Limestone, crinoidal 0.51 Mudstone, shelly and crinoidal at top: rest carbonaceous rooty in places 1.19 Mudstone, shelly, with Lingula, productoids, and bivalves but the coal and three of the limestones are present, with the fourth represented by a marine band."
"Northward thinning of units plus changes in facies, for instance of the Hurlet Limestone, suggest that the northern part of the sheet may have escaped some of the marine invasions."
"The Upper Carboniferous strata are assigned to two groups, firstly the upper part of the Clackmannan Group comprising the Limestone Coal Formation, the Upper Limestone Formation and the Passage Formation, secondly the informal group, the Coal Measures which is made up of the Lower, Middle and Upper Coal Measures."
The boundary between the two lithostratigraphic divisions almost coincides with the Namurian and Westphalian boundary.
"The Silesian part of the Clackmannan Group, which consists of the Limestone Coal Formation, the Upper Limestone Formation, and the Passage Formation, is characterised by the continuation of the deposition of cyclothematic sediments which started in the upper Dinantian."
"The top of the Limestone Coal Formation is taken at the base of the Index Limestone, the top of the Upper Limestone Formation at the top of the Castlecary Limestone, and the top of the Passage Formation at the Lowstone Marine Band."
The Limestone Coal Formation is the lowest part of the Namurian sequence and belongs entirely to the Pendleian.
"Exposures are largely confined to streams flowing off the Kilsyth Hills such as Queenzie Burn, where the Black Metals are visible at -LSB- NS 694 786 -RSB-, the Garrel Burn, the Banton Burn, where much of the lower part of the group can be seen above Banton -LSB- NS 750 792 -RSB-, and locally along the Castlerankine Burn and the River Carron, both of which traverse the whole of the formation."
"Coals are largely, but not entirely, confined to that part of the sequence between the Johnstone Shell Bed and the Black Metals, and they are generally thicker than in the west."
"The Kilsyth Coking Coal in particular thickens markedly to 1.5m around Kilsyth, a thickness only exceeded in the upper part of the formation by the Bannockburn Main Coal around Dunipace."
"Clayband ironstones are less abundant than to the west of the district except in the Black Metals in the Banton area where nine occur, three of which were formerly worked."
"The Garibaldi Clayband Ironstone was mined at Banton as the Finestone, but the Johnstone Clayband Ironstone is thin or absent."
It is the equivalent of the Lower Garscadden Ironstone of Sheet 30E: there is no equivalent of the Upper Garscadden Ironstone in the present district.
The cycle that starts with the Kilsyth Cloven Coal is usually the thickest.
"The most extensively mined of the coals is the Meiklehill Main, which is rivalled in thickness only by the Bannockburn Main Coal of Dunipace and the Kilsyth Coking Coal in the lower part of the formation."
"Other extensively mined seams include the Kilsyth Cloven, Dumbreck Cloven and Meiklehill Wee coals."
"Nine of the coals pass laterally into blackband ironstones, six of which were mined, the Kilsyth No. 3 seam quite extensively."
The Banton Blackband Ironstone in the lower part of the formation is also of local occurrence.
"The Cowlairs Sandstone at the top of the formation, on the other hand, is generally absent along the northern margin of the outcrop and is best developed at its type locality in northern Glasgow."
The most persistent sandstone in the upper part of the formation is the Nitshill Sandstone which reaches 20m in thickness.
"It cuts out the underlying Ashfield Rider Coal and at its thickest, its incompactibility prevented the Fourteen-Inch Under Coal, together with its seatearth and overlying mudstone, from developing."
"Other thicker and coarser sandstones locally cut out the Possil Wee and Possil Rider coals and the Berryhills Limestone, mainly along the northern margin of the outcrop from Torrance -LSB- NS 620 742 -RSB- to Dunipace."
The depositional basin continued to subside during the deposition of the Limestone Coal Formation but marine influences were much weaker than in the underlying formation.
Increased subsidence brought about the major marine incursion represented by the Johnstone Shell Bed but only in the southeast corner of the Sheet was the sea clear enough to permit even impure limestone to form.
"The Upper Limestone Formation occurs in most of the central and southern parts of the Sheet, largely at the crop in the central parts, and buried below Coal Measures in the southern part."
The lower part of the group belongs to the Pendleian.
The Index Limestone is rather poorly exposed in the Castlerankine Burn -LSB- NS 7952 8228 -RSB- and is seen to be baked hard by an underlying sill at Craigroot Quarry -LSB- NS 691 776 -RSB- and beside the adjacent Queenzie Burn.
"Here, the overlying mudstones are 6 to 8m thick and the Bishopbriggs Sandstone has conspicuous laminated burrows."
"Strata between the Index and Lyoncross limestones, including the Huntershill Cement Limestone, are exposed in the headstreams of the Wood Burn -LSB- NS 6743 7756 - NS 6790 7712: NS 6818 7779 - NS 6804 7729 -RSB-."
"The mudstones above the Orchard Limestone, and the Glenboig Marine Band are exposed in the railway cutting -LSB- NS 619 707 -RSB-."
"The Calmy Limestone was formerly visible in several quarries in northeast Glasgow, around Cumbernauld and elsewhere."
The sandstone below Plean No. 1 Limestone and thelimestoneitself are displayed in Drumcavel Quarry -LSB- NS 705 694 -RSB-.
"The Red Glen at Cumbernauld provides several exposures of the strata associated with the Plean Limestone, including one of Plean No. 2 Limestone -LSB- NS 7753 7520 -RSB-, which can also be seen in a quarry -LSB- NS 7625 7415 -RSB- in Glencryan Wood."
The Castlecary Limestone is no longer visible around Castlecary or Cumbernauld.
The Upper Limestone Formation in the Sheet area is between 225m and 300m thick except in two areas.
These boreholes lie in a northeast-south-south-west trending positive area marked by reduced sedimentation in Namurian times.
The overlying Passage Formation rests disconformably on various strata ranging from the Castlecary Limestone in the north to just above Plean No. 1 Limestone in the southeast making comparison of differences in the thickness of the formation in different areas largely invalid.
The Upper Limestone Formation can be divided into two parts reflecting both lithology and chronostratigraphy.
"The lower part, up to the Orchard Limestone, consists mainly of coal-cyclic sequences similar to those in the upper part of the Limestone Coal Formation except that they are extensively replaced by erosive sandstones."
"The first started at the Index Limestone, a typical Upper Limestone Formation bioclastic crinoidal limestone, characteristically containing algal bodies."
"This is overlain by several metres of mudstone that pass, usually gradually, upwards through siltstone to the generally, fine-grained Bishopbriggs Sandstone."
The end of this marine phase is marked by the Huntershill Cement Limestone.
The Bishopbriggs Sandstone locally contains abundant trace-fossils and may be part of the marine episode.
The second major marine incursion resulted in the formation of the Lyoncross Limestone and a few metres of mudstone.
"The thickest coal is the Chapelgreen which was worked to a small extent -LSB- NS 6972 7750 -RSB- near Kilsyth and possibly also, as Gardner 's Coal, at Meiklehill -LSB- NS 6676 7401 -RSB-."
The Lyoncross Coal is not known to have been mined in the Sheet area.
The Bishopbriggs Sandstone is very variable in thickness and thins markedly eastwards from over 30m at its type locality to less than 2m over a distance of less than 5km.
By contrast the sandstones which lie between the Huntershill Cement Limestone and the Lyoncross Coal are generally much coarser and have erosive bases.
The lowest of these sandstones is the Upper Dumbreck Sandstone which reaches almost 40m in thickness and locally cuts out the Huntershill Cement Limestone.
"The next notable sandstone is the Cadgers Loan Sandstone, which is a very persistent bed up to 26m thick that locally replaces one or more of the coals lying both above or below it."
"Above the Lyoncross Limestone the most notable of the coarser, erosive sandstones is the Giffnock Sandstone, which is best developed in the present sheet along the northern part of the outcrop, for example in Torrance No. 1 Borehole -LSB- NS 6419 7359 -RSB- where it is 22m thick."
The upper part of the Upper Limestone Formation starts with two major Yoredale-type cycles.
The base of the final cycle is marked by the Orchard Limestone.
"Locally, the overlying sandstone, which reaches 37m in thickness in Torrance No. 1 Borehole, is divided by the Glenboig Marine Band, developed mainly in up to four beds of mudstone, but also as the Glenboig Limestone."
The Lower and Upper Hirst coals at the top of the cycle are both very variable.
"The Calmy Limestone marking the base of the second cycle is typically in two leaves of ` calmy ' type - hard, fine-grained, compact, pale-grey, fawn or almost white in colour: conchoidal in fracture and not conspicuously fossiliferous but sufficiently so to establish its fully marine character."
"It is usually 1.3 - 2m thick, but reaches 3m, the maximum for an Upper Limestone Formation limestone in the Sheet area."
The Calmy Limestone was formerly quarried at several widely scattered localities and is known to have been mined around Muirhead -LSB- NS 683 695 -RSB- and Cumbernauld.
The mudstone above the Calmy Limestone is also thick and grades up through siltstone into sandstone: the proportions of the three lithologies vary a great deal.
Plean No. 1 Limestone is shelly and crinoidal over much of the Sheet area but locally develops a coralline phase.
"It usually has little or no coal below it, except in the northeast, where a seam which was mined to a small extent as the Navigation Coal, may lie at this horizon."
"Above Plean No. 1 Limestone there is a sequence, known as the strata associated with the Plean Limestones, that is 25m to 40m thick and includes up to 6 cycles, three of which locally include a thin coal."
"Near the top of the sequence is Plean No. 2 Limestone which, although generally persistent, is locally cut out."
Plean No. 3 Limestone is not known in the Sheet area.
The highest part of the Upper Limestone Formation is known only in the north where it is up to 35m thick and consists mainly of a coarse-grained sandstone up to 18m thick with an erosive base.
"The Castlecary Limestone at the top of the group is also known only in the north, where it is 1.5 - 2.0m thick, dolomitic and locally affected by contemporaneous leaching that reduced it to nodules in a clay matrix as seen in the Coneypark Borehole -LSB- NS 7754 7888 -RSB-."
The Orchard Limestone has a thickness within its normal range.
The Calmy Limestone are actually thicker.
The Upper Limestone Formation shows marked contrasts in palaegeography.
"Their duration is uncertain because the absence of marine fossils in silty or sandy sediments does not preclude marine conditions: for example, in the interval between the formation of the Index and Huntershill Cement limestones."
"The Castlecary Limestone, produced in this event, was probably formed all over the district but was speedily removed from much of it by penecontemporaneous erosion."
Towards the end of Upper Limestone Formation times more widespread erosion resumed in the southern part of the district heralding the more powerful downcutting processes in Passage Formation times which removed variable amounts of the highest Upper Limestone Formation strata.
"The term ` Passage Group ' Millstone Grit, because the strata concerned are equivalent to only the top part of the English Millstone Grit, plus some of the English Lower Coal Measures."
In the Central Coalfield the Passage Group originally included the strata between the Castlecary Limestone and the Crofthead Slatyband Ironstone but Francis and others extended the group in the adjacent Stirling and Clackmannan Coalfield upwards to the base of the more persistent Lowstone Marine Band.
The presence of both Marsdenian and Westphalian A strata is indicated with some certainty by miospore evidence.
"It has not, however, proved possible to identify the Gastrioceras subcrenatum marine band at the Namurian-Westphalian boundary, although it is thought to be one of the bands in the No. 6 Marine Band group of the Passage Formation."
It follows that the Lowstone Marine Band together with the topmost beds of the Passage Formation is regarded as lying within Westphalian A.
"Numbers 0, 1 and 2 occur as single bands, usually with limestones: No. 0 is local, the other two are widespread except in the southeast part of the Sheet."
In the Alexandra Parade Borehole three bands occur close together and contain a fauna that suggests identification as No. 3 Marine Band group though the borehole is more than 25km southwest of the nearest known occurrences.
"A single marine band occurs in the Castlecary - Bonnybridge area, on both sides of the Sheet 31W - Sheet 31E boundary, between No. 3 Marine Band and No. 5 Marine Band group."
"It is suggested that the term No. 4 Marine Band be resurrected for this band, which is represented at Castlecary by a Lingula band but is not known elsewhere in the district."
"No. 5 Marine Band group includes four marine or Lingula bands at Castlecary, one more than Francis and others could confirm in the Kincardine Basin."
"No. 6 Marine Band group is represented in Sheet 31W by a single Lingula band, known only at Castlecary."
The Passage Formation crops out in an irregular northeast-trending belt across the middle of Sheet 31W extending below Coal Measures to the south.
"This erosive process was most notable in the upper part of the formation, although a widespread break prior to the deposition of No. 0 Marine Band occurs over most of the Sheet area."
This erosive event removed the Castlecary Limestone over the central and southern parts of the Sheet and locally cut down as far as Plean No. 2 Limestone.
The Bowhousebog Coal is absent but the Bonnybridge Upper Fireclay can be recognised.
The Goodockhill Slatyband Ironstone is represented by a coal but the last surviving band in No. 6 Marine Band group has disappeared.
"An assemblage of mudstones, fireclays and a thin coal includes a Lingula band as a representative of No. 5 Marine Band group, to which a marine band 9m below it may also belong."
"Below a coarse, pebbly sandstone, with a clearly erosive base, there is a thin crinoidal limestone that is tentatively identified as Plean No. 1 Limestone of the Upper Limestone Formation."
If this correlation is correct the Passage Formation is 80m thick and the lower part is entirely missing.
The Passage Formation consists mainly of sandstones with subordinate poorly-bedded mudstones that are commonly termed fireclays regardless of their refractory properties.
"Bedded mudstones, siltstones, coals and limestones all occur but are very thin except from the base to the top of No 2 Marine Band and within Nos 3 and 5 Marine Band groups where the succession is clearly coal-cyclic with all the lithologies forming significant parts."
"Most of the seams used lie in the Passage Formation, including the one which was most extensively exploited, now named the Glenboig Lower Fireclay but widely known as the Lower Fireclay."
It lies between the Roman Cement and the Netherwood Coal.
The Glenboig Lower Fireclay yields material with over 40% alumina and was quarried or mined almost throughtout its outcrop from Heathfield to Castlecary.
"It may therefore be largely the product of intense bauxitic weathering of basaltic lavas, possibly being derived from exhumed parts of the Clyde Plateau Volcanic Formation."
The latter must not be confused with the much higher Bonnybridge Upper Fireclay to the east.
"Some, such as the Captain 's Fireclay at Glenboig, are probably in the Lower Coal Measures."
"The very shaly or cannely mudstone immediately above the Castlecary Limestone at Castlecary and Cumbernauld contains Curvirimula, fish debris and ostracods."
There are up to three thin impersistent limestones near the base of the Passage Formation.
The lowest is No. 0 Marine Band Limestone.
"Nos 0 and 1 Marine Band Limestones are both argillaceous, bioclastic and crinoidal, in contrast to the Roman Cement or No. 2 Marine Band Limestone, which consists largely of a ` lumachelle ' of crushed orthotetoid and Schizophoria valves."
The Netherwood Coal takes its name from Netherwood Farm -LSB- NS 775 784 -RSB-.
The Skipperton Coal is 0.5m thick at Castlecary but elsewhere is not identifiable.
"The Bowhousebog Coal is known at Bonnybridge, just east of the sheet margin, but its presence has not been established within the sheet, even in the Banknock-Castlecary area."
"It is probably a correlative of the better known Crofthead Slatyband Ironstone of Sheet 31E, as is the Earlshill Upper Slatyband Ironstone, whose workings, at depths of over 150m, extend westwards onto Sheet 31W at Stepends -LSB- NS 804 671 -RSB- and Easter Moffat -LSB- NS 802 663 -RSB-."
The Goodockhill Slatyband Ironstone of Sheet 31E is represented by a coal in the Chapelhall area: its horizon is not recognisable elsewhere.
"Read indicated that with the onset of the Passage Formation the paralic, probably mainly deltaic conditions that had prevailed in the Central Coalfield tended to retreat before a great influx of coarse-grained clastic sediments."
"The depositional basin probably contracted, some of the Dinantian lavas to the north and west may have been exhumed and fluviatile conditions prevailed."
"The marine strata mostly die out to the west and south, the directions in which the Passage Formation thins markedly."
"Here, the lower part of the formation, plus the top of the Upper Limestone Formation, appears to be missing."
"The coal-bearing, cyclic, fluviodeltaic sediments which overlie the Passage Formation have long been known as `` coal measures ''."
He split the latter into the Middle Coal Measures and the Lower Coal Measures.
The top of the Middle Coal Measures was defined by Skipsey 's Marine Band.
The term Coal Measures reflects the different usage in Scotland and because the top and bottom are not formally defined it is considered to be an informal unit of group status.
"The Lower Coal Measures falls entirely within Westphalian A, ending at the top of the latter."
The base is now drawn at the Lowstone Marine Band which lies about 70m above the base of Westphalian A at Castlecary and less than that elsewhere in the district.
"The Lower Coal Measures occur, either at the surface or at depth, over most of the southern half of the Sheet and also in the Banknock Coalfield."
"The Lower Coal Measures are thickest, the thinning being most marked in the lower part of the sequence."
"The mudstones and siltstones between the Ladygrange and Airdrie Virtuewell coals are commonly unusually pale-grey in colour, in places with a greenish tinge."
The only carbonate rock calcareous enough to be locally called limestone is at the top of the sequence and is more usually known as the Roughband Ironstone.
"It occurs in the seatclay below the Vanderbeckei Marine Band and is best developed in the southeast part of the Sheet, where it was mined."
Two were mined as the Chapelhall Lower and Upper Fireclays.
The coals in the Lower Coal Measures are mostly less than 1m thick.
"However, the Lime Coal of Greengairs dies out completely north of Airdrie: the two leaves of the Mid Drumgray Coal coalesce in the east and south-east and the Bonnyhill Craw Coal is absent over wide areas."
"One is named after the Auldshields Musselband, which is only found in the Sheet area around the type locality -LSB- NS 770 715 -RSB-."
The other lies between the Kiltongue Musselband and the Ladygrange Coal.
The four most extensively mined were: 1 -RRB- the Lower Drumgray.
The seams are generally thinner than those in the overlying Middle Coal Measures and dewatering was a considerable problem.
Blackband ironstones are rare in the Lower Coal Measures of the Sheet area.
The Colinburn Coal in its Duntilland Parrot phase around Chapelhall includes blackband ironstone.
"The Auldshields Musselband Ironstone is sufficiently carbonaceous at Auldshields -LSB- NS 7710 715 -RSB- to be included but the only seam known to have been mined for blackband ironstone alone is the Bellside Ironstone, a local development up to 0.2m thick of the Bellside Coal in the Newarthill - Cleland area."
"The upper part of the Kiltongue Coal passes locally into cannel, oil-shale and ironstone in the Chapelhall area and was worked as the Calderbraes or Kennelburn Ironstone."
"The Kiltongue Musselband Ironstone is part of a complex seam which locally includes a coal up to 0.6m thick, that was mined at Banknock as the Shale Coal."
Oil-shale up to 0.35m thick also occurs in places above the Airdrie Virtuewell Coal and was formerly exploited in northern Airdrie.
The dominantly fluviatile conditions of the Passage Formation gradually gave way to a broad flat deltaic plain.
The Middle Coal Measures coincide exactly with the Westphalian B stage.
"They are covered by Upper Coal Measures in the Lanarkshire Basin, at Rutherglen, in a west-east belt from Glasgow almost to Holytown and in a small area in Coatbridge."
"The Middle Coal Measures are almost 200m thick in the east, decreasing westwards to 160m."
"Coarser and usually thicker sandstones are largely confined to the strata above the Glasgow Upper Coal, where they locally cut out parts of the cyclic sequence."
Examples include the Shettleston Sandstone.
Examples include the effect of the Auchinlea Sandstone on the Airdrie Blackband Coal southeast of Newarthill and the thinness of the Humph Coal in eastern Glasgow.
The very variable sandstone between the Glasgow Main and Pyotshaw coals has little effect on either seam.
"The Airdrie Blackband Coal was mined extensively except in Glasgow, where it is thin, and in Coatbridge and Airdrie, where the lower leaf is thin or absent and the upper leaf passes laterally into the Airdrie Blackband Ironstone."
"The Coatbridge Musselband Coal was mined to a small extent in the Airdrie area, where it reaches its maximum thickness."
The Virgin Coal is one of the most variable seams in the Middle Coal Measures thinning eastwards and more markedly southwards.
"The Glasgow Splint Coal was very much in demand, especially for furnaces, because the hard splinty character of bands in the seam although locally in southeast Glasgow the coal was ` burnt ', that is, oxidised by fluids percolating down from thick, locally red-stained sandstones."
"The Humph Coal is also variable being thin or absent in eastern Glasgow and generally in two-leaves in the Coatbridge-Airdrie area, where mining was largely confined to the southern part of the district."
The Humph Rider and Glasgow Main Under both pass locally into blackband ironstone in Glasgow.
"It forms a single seam, up to 3m thick, with the Pyotshaw Coal in Glasgow and locally elsewhere, for instance around Newarthill."
"The Glasgow Ell Coal is thickest in the south, where it locally exceeds 3m and was much sought after."
The Maggie Coal is a local development in the Holytown - Newarthill area.
"The Glasgow Upper Coal, which has been mined between Glasgow and Bothwell, is the highest of the important seams."
"Like the Virgin Coal it is thickest in the west, where it locally exceeds 2m, but thins markedly south-eastwards and less so eastwards."
The variable Palacecraig Coal is up to 0.9m thick and passes into the 0.3m Palacecraig Blackband Ironstone south of Airdrie.
"Seams in the Middle Coal Measures in the Banknock Coalfield have been mined using Central Coalfield names such as Virgin, Splint, Humph, Main and Pyotshaw."
"Sedimentation on the delta plain which prevailed during most of Westphalian A was interrupted by the major marine incursion that formed the Vanderbeckei Marine Band, but thereafter became reestablished during Westphalian B."
These incursions allowed marine or quasi-marine rather than non-marine faunas to become established at regular intervals towards the end of Westphalian B.
The Upper Coal Measures are the youngest Carboniferous strata preserved in the district and belong mainly to the Westphalian C stage but may include some Westphalian D strata at the top.
"The Aegiranum Marine Band at the base is known in Scotland as Skipsey 's Marine Band, although it is now believed."
The Upper Coal Measures are up to 270m thick and are confined to the southern part of the Sheet where the main outcrop is in the middle of the Lanarkshire Basin.
Skipsey 's Marine Band is visible in the North Calder Water -LSB- NS 7519 6324 -RSB-.
The Bothwell Bridge Marine Band is exposed in the Clyde at its type locality -LSB- NS 7069 5773 -RSB-.
No coal in the Upper Coal Measures is known to have been mined but a terra-cotta clay 2.6m thick which occurs almost 50m above the base was mined from 1955-65 at Blantyreferme Nos. 4 and 5 mines -LSB- NS 682 610 -RSB-.
The Upper Coal Measures were deposited as coal-cyclic sequences but subsequent oxidation has reddened all but the lowest strata and the coals have mostly been destroyed or replaced by limestone.
Deposition of the Upper Coal Measures was intially controlled by a marine incursion which formed the Aegiranum Marine Band.
"Thereafter conditions returned to these characteristic of Late Westphalian B times, with delta plain sedimentation locally interrupted by sand-filled distributary channels."
"General discussions of the nature and palaeoecological significance of the marine faunas of the Dinantian and Namurian have been published by Wilson, and some details from these accounts have been included here."
Selected Dinantian and Namurian fossils are illustrated in Plate 5.
Lawmuir Formation.
On this sheet the formation includes strata which are mainly of Brigantian age.
"As already noted Latiproductus cf. latissimus is common at the horizon of the Hollybush Limestone over most of the area, but otherwise is rarely present."
"Miospores from this formation in the Lawmuir Borehole, drilled in the adjacent 30E sheet are characteristic of the VF Miospore Zone and may thus be regarded as of Brigantian age."
Lower Limestone Formation.
The marine fauna from this formation is more varied than that from the Lawmuir Formation and the individual marine episodes also show greater differences between each other.
"In general the Hurlet Limestone is not very fossiliferous, although in the Corrieburn area the mud fraction is reduced, with the result that the fauna changes and a wider variety of corals and brachiopods, together with Limipecten dissimilis, is present."
"The Blackhall Limestone, with the Neilson Shell Bed in the mudstones above it, carries one of the most varied faunas in the Lower Limestone Formation."
"In localities along the southern margin of the Campsie Fells the lower two of the Hosie Limestones contain isolated specimens of Caneyella membranacea, a bivalve common in the higher beds of P2 Zone in the Pennine region of England."
There are marked differences between the faunas which occur in the Lower Limestone Formation in the north of the Airdrie Sheet and those from the adjacent Hamilton Sheet to the south.
"However, little is known of the faunas of the formation in the intervening area below the wide outcrop of Coal Measures strata."
Miospore evidence from various sources suggests that rocks of the Lower Limestone Formation contain assemblages typical of the VF Miospore Zone and that this zone is represented in the Hosie Limestones.
"Conodonts described by Clarke from just below the Top Hosie Limestone indicate the presence of the upper part of P2 Zone, that is, a late Brigantian age."
The discovery of Cravenoceras scoticum in shales below the Top Hosie Limestone at East Kilbride to take the base of the Pendleian stage below the Top Hosie Limestone.
Thus the Visean - Namurian boundary has been taken for convenience at the base of the Top Hosie Limestone.
"There have been no records of the goniatites which characterise the principal Lower Coal Measures marine bands in Lancashire and the base of the Westphalian is thought to occur within No. 6 Marine Band group, where miospores indicative of a basal Westphalian A age have been found in adjacent areas."
Above this level only the Lowstone Marine Band is well represented on this sheet and that only in the east.
"The faunas in the Duntilland Parrot phase of the Colinburn Coal include Carbonicola crispa, and in the Auldshields Musselband Carbonicola extenuata is present, thus enabling the recognition of the Lenisulcata Biozone in the eastern part of the sheet."
The non-marine bivalves become more abundant above the Coatbridge Balmoral Coal and scarcer again above the Kiltongue Musselband.
"Westwards the faunas deteriorate and even the normally persistent bands such as those above the Shiels, Shotts Gas and Upper Drumgray coals become, at best, intermittent in occurrence."
In the Glasgow area Curvirimula is found in association with Euestheria and Leaia in strata between the Shotts Gas and Upper Drumgray coals.
"Near the base of the zone, above the Mill Coal, the trace fossil Planolites aff."
"The Kiltongue Musselband contains Anthraconaia modiolaris, Anthracosia regularis and Carbonicola oslancis and has been taken to mark the base of the Modiolaris Biozone."
The Middle Coal Measures may be divided into three sections on the basis of the contained faunas.
"The lower part, up to the Pyotshaw Coal at the top of the Modiolaris Biozone, is dominated by several rich non-marine bivalve bands."
"The only marine band is the Vanderbeckei Marine Band, originally described as the Queenslie Marine Band."
"Non-marine faunas deteriorate southwards to some extent, and at the horizon of the Coatbridge Musselband they also deteriorate westwards."
The middle part extends to just above the Palacecraig Coal and is entirely within the Lower Similis-Pulchra Biozone.
Euestheria is widespread in horizons above the Glasgow Upper Coal and the lowest of the Lower Similis-Pulchra Biozone marine bands also occurs in this part of the sequence.
"In general the non-marine bivalve faunas below the Glasgow Upper Coal are best developed in eastern Glasgow, those above it, in Coatbridge and Airdrie."
The highest part starts with the Carnbroe Marine Band and includes the Drumpark Marine Band and the recently discovered Dalziel Works Lingula Band near the top.
The Drumpark Marine Band is now thought to be the marine band originally described by Skipsey.
The Aegiranum Marine Band exhibits three different facies within the area of this sheet.
"In the east it occurs in shale with a black limestone near the base, reminiscent of the development of the band in much of the Pennine area of England, but with a less varied fauna."
"The only other marine horizon recognised in the Upper Coal Measures is the Bothwell Bridge Marine Band, now known to extend from the type locality westwards to the Prospecthill borehole on sheet 30E."
The association has led to this band being correlated with the Shafton Marine Band of the Pennine coalfields of northern England.
The horizon of intrusion rises eastwards from low in the Coal Measures to above the Glasgow Main Coal in the Middle Coal Measures.
Three members of the sill-complex in the adjacent Sheet 30E have been radiometrically dated at 270-273 Ma suggesting that the complex is early to mid - Permian in age.
They cut strata up to Westphalian A in age.
"Their age is assumed to be the same as that of the sills, namely 290-295 Ma, that is late - Westphalian or early Stephanian."
East of there a continuation cuts Namurian strata and extends on to Sheet 31E.
"The Midland Valley quartz-dolerite sill-complex is regarded as late - Westphalian or early Stephenian, with a radiometric age of 290-295 Ma."
In the north the main part of the sill-complex is intruded into Lower Carboniferous strata.
"Southwards it rises stratigraphically through the Limestone Coal Group at Kilsyth, the Upper Limestone Group at Cumbernauld, the Passage Group at Glenboig reaching the Middle Coal Measures at Airdrie."
"The more northerly one is within the Clyde Plateau Volcanic Formation and the other, separated from it by the Campsie Fault, straddles a NE-SW fault between the Clyde Plateau Volcanic Formation and the Lower Limestone Formation."
"Biotite crystals from the Lennoxtown essexite have been dated radiometrically at 270 Ma suggesting an early or mid - Permian age, the same as the alkali-dolerite sills."
The inclusions are notably similar to those found in Lower Devonian conglomerates along the Highland Boundary Fault.
"Olivine-dolerite dykes with WNW-ESE trend occur in late - Dinantian and Namurian strata at the surface in the Lennoxtown area, underground near Torrance -LSB- NS 620 742 -RSB- and both above and below ground between Glasgow and Coatbridge."
The graben structure was developed in the early Devonian in a zone of crustal weakness inherited from the Lower Palaeozoic.
"Analyses of plate movements, structural patterns, facies distribution of the sediments, and the presence of volcanism, have led to the proposal of a wide variety of stress systems and their origins, which are thought to have affected the Devonian and Carboniferous of the Midland Valley."
"However several authors, such as Kennedy, have pointed out that different stress systems appear to have been operative at different times during the late Devonian and Carboniferous."
"The oldest sediments seen at the surface in the Airdrie district, the Inverclyde Group of late Devonian - early Carboniferous age, were deposited under quiet tectonic conditions on an alluvial plain which became marginally marine and subject to fluctuating salinity and periodic dessication."
"Shortly after, during the mid - Dinantian, a major unconformity occurred along the south margin of the Kilsyth Hills, just to the south of the South Campsie Linear Vent System."
This implies that the break may be due to magmatic updoming prior to eruption of the Clyde Plateau Volcanic Formation lavas.
The absence of volcanics in a very attenuated Lower Carboniferous sequence in this area does not preclude magmatic updoming as a controlling mechanism.
In the western part of the Midland Valley the unconformity was followed by the eruption of several hundred metres of lavas belonging to the Clyde Plateau Volcanic Formation.
Cyclic sedimentation became established and continued throughout the late Dinantian and Silesian.
During the late Dinantian the cyclic sediments of the Lower Limestone Formation indicate repeated subsidence of a fluvio-deltaic environment below a shallow sea.
During the Namurian the Limestone Coal Formation sediments of the present district were deposited in a similar pattern in river-dominated deltas with occasional marine influxes.
On the bases of facies and thickness distribution of the Limestone Coal Formation sediments Stedman suggests that the stress regime was one of E-W tension which in the SW of the Midland Valley reactivated a Caledonoid grain.
In the present district the succeeding fluviodeltaic and marine sediments of the Upper Limestone Formation are thickest in an ENE-WSW basin which developed under what is thought to be transtensional conditions near the centre of the area.
The dominantly fluvial conditions with short-lived marine incursions which followed during the deposition of the Passage Formation show a marked change in facies and sediment thickness.
The overlying fluviodeltaic Lower and Middle Coal Measures of Westphalian age are thickest in the east of the present district and thin gradually westwards reflecting a continuing N-S control.
The E-W trending quartz-dolerite dykes are now generally accepted to be of late Westphalian - early Stephanian in age.
This is thought to indicate an apparent N-S tensional or transtensional phase during the late Carboniferous.
He concluded that all these Silesian structural features are compatable with right-lateral strike slip superimposed on thermal subsidence.
"Though the amount of lateral movement may be relatively small up to the end of the Namurian, it may have been greater at the end of the Carboniferous."
"In this context, transtension appears to have dominated with brief intervals of transpression during deposition of the early part of the Limestone Coal Formation, Passage Formation and towards the end of the Silesian."
The Clyde Plateau Volcanic Formation north of the Campsie Fault is very gently tilted to the east but shows no sign of folding.
"Towards the north, where it becomes a very shallow, open fold, an ill-defined anticline separates it from a NNE-SSW syncline that runs from Balmalloch -LSB- NS 704 782 -RSB- to Shirva -LSB- NS 691 755 -RSB-, where it ends in the basin with Passage Formation strata on the north side of the Hilton-St Flanans Fault."
"From the half-dome with Limestone Coal Group strata south of the fault, a diffuse, ill-defined NNE-SSW anticline can be traced as far south as Gartcosh -LSB- NS 699 681 -RSB-."
"The Coal Measures in the Banknock Coalfield are bounded by two large faults and quite steeply folded into a W-E syncline with a small deep basin at each end, in which are found the youngest strata preserved."
"The southern part of the sheet is dominated by the northern part of the Lanarkshire Basin, a broad, open structure largely free of faults, and occupied by Upper Coal Measures."
"To the southwest the northerly dipping southern limb of the basin is cut off to the south by the major lineament, the Dechmont Fault, south of which the Clyde Plateau Volcanic Formation lies almost flat."
In general it separates the Clyde Plateau Volcanic Formation to the north from younger rocks to the south.
"North of the Campsie Fault, fractures are numerous in the Clyde Plateau Volcanic Formation and can mostly be divided into three types."
"Secondly, there are several that radiate out from the Waterhead Central Volcanic Complex and thirdly there is the Waterhead Ring Fault that bounds the complex itself."
"Associated marine clays of the Paisley and Linwood Formation, are preserved in parts of the Clyde valley."
By 11 0 years BP local sea-level in the Clyde valley had probably fallen from the late - Devensian maximum to present OD or lower.
"The following account of the Quaternary sediments and associated landforms is structured to reflect their relative ages and utilises the stratigraphical framework established by Browne and McMillan for the Clyde valley area with the addition of one newly defined unit, the Kelvin Formation."
"Whatever the sequence of events, it seems likely that erosive processes at work beneath ice sheets during the Quaternary have overdeepened these drainage systems."
During late - Devensian and Flandrian times the bedrock depressions have been filled principally with water-laid sediments.
"Pre - Dimlington Stade sand and gravel of the Cadder Formation is also present locally, underlying the Dimlington till of the Wilderness Formation."
"In the Airdrie Sheet, borehole records indicate thicknesses of the infilling sediments to range from about 30m west of Kilsyth -LSB- NS 700 770 -RSB- to 87m at Torrance -LSB- NS 620 735 -RSB-."
Between Bothwell -LSB- NS 700 580 -RSB- and Cambuslang -LSB- NS 640 600 -RSB- the river bed is cut mainly in rock and is therefore likely to be mainly of Flandrian age.
"On the high ground of the Airdrie district, the Devensian topography was probably similar to that of today."
"On high ground north of Airdrie -LSB- NS 760 650 -RSB- and around Cumbernauld -LSB- NS 770 745 -RSB-, where drift thicknesses generally do not exceed a few metres, easterly aligned crag and tail landforms are developed on resistant bedrock including Upper Carboniferous sandstones and Permo - Carboniferous dolerite sills and dykes."
"These deposits, which are preserved only in a limited area around Baillieston -LSB- NS 670 640 -RSB- in eastern Glasgow, are overlain by the Baillieston Till Formation."
"The till lies stratigraphically below the Wilderness Till Formation and, despite the absence of definitive age data, is considered to be the product of a glacial event earlier than the late - Devensian."
In general the colour of the clay matrix is greyish brown reflecting that of the local Coal Measures bedrock.
"Possible ancient surface weathering, in the form of oxidation, results in a reddish brown hue to the upper surface of the Baillieston Till as seen in the M8 sections."
Here sand and gravel of the Cadder Formation rests on the Baillieston Till Formation and is in turn overlain by the Wilderness Till Formation.
Between Torrance -LSB- NS 620 740 -RSB- and Kirkintilloch -LSB- NS 655 740 -RSB- most available borehole logs record only the top part of the Quaternary sequence through the Flandrian and late - Devensian sediments.
However records of boreholes south of Redbog Farm at Torrance -LSB- NS 6153 7361 -RSB- and Crofthead -LSB- NS 6228 7264 -RSB- penetrated the top few metres of sand and silt lying below the Wilderness Till.
"Broomhill Formation, see below -RRB- lies between the sand and gravel and the Baillieston Till."
Observed faulting of the sediments may be due in part to glacial overriding by the ice-sheet that deposited the overlying Wilderness Till Formation.
The outwash deposits were subsequently overridden by the ice which deposited the overlying Wilderness Till Formation.
Subsurface data and temporary sections reveal laminated muds resting discontinuously upon the Baillieston Till.
The clay was observed to be in thrust contact with the underlying Baillieston Till and overlying Wilderness Till.
The principal deposit of the Dimlington ice sheet is the Wilderness Till Formation.
"The Wilderness Till Formation was proved, amongst others, in the BGS Bellshill -LSB- NS 7304 6161 -RSB- and Bothwell Park -LSB- NS 7159 5956 -RSB- boreholes."
"The colour of the matrix varies, depending upon that of the local bedrock and can be reddish brown from Devonian and Upper Coal Measures sources, brownish grey or black from Lower and Middle Coal Measures and Namurian strata and greenish grey from Highland metamorphic rocks."
Minor features noted in the Wilderness Till include pockets and bands of medium-grained sand and thin bands of laminated clay.
"In the Cadder area, temporary sections in the Wilderness Till revealed that locally the diamicton is graded, displaying both upward and downward coarsening of the dispersed pebble to boulder sized clasts."
In the easternmost of the sections the clays and silts are sheared out so that the Wilderness Till Formation rests directly upon the Baillieston Till.
"The overlying till, which is considered to be the Wilderness Till, is a red-brown, sandy, clayey diamicton."
The observed faulted blocks may represent a disturbed floor of the Baillieston Till Formation or may alternatively be isolated slices of the Wilderness Till broken off and incorporated into the bedded sediments by glacitectonic processes.
"At Cadder, glacitectonic disturbance in the Cadder Formation, which underlies the Wilderness Till Formation, is restricted to minor faulting and small-scale folding."
Early references to organic remains either caught up within or underlying the Wilderness Till Formation provide indications of boreal and sub-arctic climatic conditions before and during the build-up of the ice sheet.
"Although all of the species recorded from Airdrie occur in Devensian interstadial faunas, no specific interstadial has been found to contain all five of the Airdrie taxa."
"Sand and gravel transported and deposited by meltwaters in both valleys are referred to the Broomhouse Formation, named after the Broomhouse area of eastern Glasgow, where the deposits directly overlie the Wilderness Till Formation."
The landforms associated with deposits of the Broomhouse Formation indicate an ice contact environment.
The sedimentological features of the Broomhouse Formation point to the operation of fluvial and deltaic processes.
The Bellshill Formation is named from the Bellshill area where the unit is widely distributed at surface and is usually underlain by the Wilderness Till.
The presence of deltas building out laterally into the lake from tributary valleys of the Clyde is indicated by the occurrence of the sand and gravel bodies which have been assigned to the Ross Formation.
"Sediments deposited in a proximal position to the ice dam at the the northwest end of the proglacial lake are interpreted as a complex of ice-contact and deltaic sands and gravels, assigned respectively to the Broomhouse Formation and Ross Formations."
"Although the transport direction of the Ross Formation is ambivalent in temporary sections exposed at Bothwell -LSB- NS 708 589 -RSB-, there are clear indications of easterly current directions in the Broomhouse Formation at Greenoakhill Gravel Pit -LSB- NS 675 625 -RSB-."
Similar structures also affect the overlying marine Paisley Formation clays.
"Moundy deposits of sand and gravel, assigned to the Broomhouse Formation, occupy mainly the northern slopes of the Kelvin and Bonny Water valley, between Kilsyth -LSB- NS 720 780 -RSB- and Bonnybridge -LSB- NS 824 800 -RSB-."
Boreholes put down on the northern valley side show deposits to range from 2 to 4m in thickness and to rest on Wilderness Till.
On the south side of the valley at Easter Dullatur -LSB- NS 747 772 -RSB- boreholes sited on the moundy terrain proved between 1 and 6m of sand and gravel assigned to the Broomhouse Formation.
On the north side boreholes prove between 3 and 26m of sand and gravel usually resting on Wilderness Till.
"Boreholes sited on the floodplain at Birdston Farm -LSB- NS 6572 7563 -RSB-, Springfield -LSB- NS 6490 7443 -RSB- and Sandy Knowes -LSB- NS 6318 7357 -RSB- all prove deposits of sand and gravel, assigned to the Ross Formation, beneath alluvial silt of the Kelvin Formation."
"The Bellshill deposits rest on some 28m of sand and gravel, presumed to be the Broomhouse Formation, which in turn overlie about 10m of Wilderness Till."
In central and western Glasgow outwash deposits which formed in a sub-marine environment have been defined as the Bridgeton Formation.
They are interpreted as being material which was eroded from the sand and gravel of the Broomhouse and Ross formations and redeposited farther downstream.
Dead ice must also have remained to cap some of the remnant mounds of sand and gravel of the Broomhouse Formation.
Locally the mounds were situated at elevations low enough to allow burial by the marine clays and silts of the Paisley Formation.
"As at Shieldhall, the Greenoakhill sections reveal evidence for burial of ice which survived perhaps for many hundreds of years in or under deposits of sand and gravel sealed under a thick cap of marine clay and silt of the Paisley Formation."
"Initially, meltwater plumes dominated and the Paisley Formation clay and silt reflects this influence."
The stratigraphical relationships of the Paisley Formation to the late - Devensian glacial and glacilacustrine deposits at Bothwell are shown on Figure 22.
The presence in the Paisley Formation sediments of primary current lineation suggests relatively high energy depositional conditions.
"The maximum altitudes to which clays assigned to the Paisley Formation are known to occur are generally over 40m above OD in eastern Glasgow and 45m above OD at Ross House, Hamilton."
In the Glasgow and Paisley areas the Paisley Formation is commonly overlain by thickly bedded muds of the Linwood Formation which contain a rich mid - to high-boreal fauna.
"There is no definitive evidence for the existence of the Linwood Formation in the Airdrie district although an occurrence of shells was recorded in ` blue ' clays in the former Polmadie Brick Pit -LSB- NS 600 628 -RSB-, just to the west of the Airdrie sheet, at a depth of 8 m. Such evidence may indicate the presence locally of small outliers of marine clays of the Linwood Formation farther east."
"In the Fullarton -LSB- NS 640 630 -RSB-, Mount Vernon -LSB- NS 650 630 -RSB- and Carmyle -LSB- NS 640 620 -RSB- areas, deltaic sand and gravel deposits of the Killearn Formation occur."
"However, dating of the supposed incision is open to doubt because of the problem of correlating largely unfossiliferous superimposed successions of sands and gravels which could include the late - Devensian Broomhouse and Bridgeton formations."
Here the till is overlain by a thin Flandrian peat dated at 5994 ~ 50 years BP.
Other examples occur in the sheet area of late - Devensian peat and associated fine-grained lake sediments which formed immediately prior to the cold episode of the Loch Lomond Stade.
"The succeeding warm phase, the Flandrian Stage, is marked by marine and non-marine deposits and landforms in the Clyde area but, despite their wide geographical distribution, these are not well understood."
"Between about 8 400 and 5 0 years BP, the main Flandrian marine transgression led to the inundation of ground on either side of the River Clyde as far upstream as Cambuslang."
Evidence for changes in sea-level is seen in the presence of three series of Flandrian to Recent levels in the lower Clyde valley.
"In east Glasgow two of these series are recognised: early to mid - Flandrian levels of up to 12m above OD, and late - Flandrian to Recent surfaces of 3 to 6 m. Associated with these surfaces in the Clyde valley are estuarine sediments of the Erskine and Gourock formations."
Although some late - Devensian peat beds occur in the sheet area the principal deposits of peat found in the district are of Flandrian age.
"During the early Flandrian, as the Scottish climate became warmer and wetter Sphagnum peat began to develop in hollows on former lake floors and on poorly drained flat areas."
"Peat, which in the Glasgow area has been assigned to the Clippens Peat Formation, formed in low lying ground particularly to the north of Coatbridge."
The peat rests on earlier Flandrian alluvial sediments.
This record serves to indicate that peat accumulated intermittently on the valley floor during the Flandrian.
"Coarse-grained Flandrian sediments deposited in fluvial environments, including present-day river courses were assigned by Browne and McMillan to the Law Formation."
Older Flandrian sand and gravel which may have been partly associated with deltaic and lacustrine environments were referred to the Endrick Formation.
"The Law Formation is named from the Law Borehole, which contains the standard section."
Up to 6m of Law Formation sand and gravel is proved in records of boreholes on the alluvial plain of the River Clyde south-east of Bothwell -LSB- NS 700 580 -RSB-.
"In the northern part of the district, alluvial gravels of the Law Formation are present in the valleys of the River Kelvin, Bonny Water, Luggie Water, River Carron and Glazert Water."
"East of Kilsyth, at Craigmarloch Drawbridge, -LSB- NS 7332 7745 -RSB- some 2.5m of sand and gravel ascribed to the Law Formation rests on late - Devensian gravels."
"Between Kilsyth and Kirkintilloch up to 5m of sand and gravel, commonly overlain by fine-grained deposits of the Kelvin Formation."
The whole sequence has been ascribed to the Law Formation but the basal part could have been deposited by glacial meltwaters during either of the late - Devensian glaciations.
Deposits of the deltaic Endrick Formation may be present under ` alluvial ' terraces of the Kelvin lying above the general level of the floodplain at elevations of 35 to 50m OD.
"At Longcroft, about 4m of gravels of the Endrick Formation overlie late - Devensian glacifluvial gravels of the Broomhouse Formation, the latter probably having been transported along the Red Glen -LSB- NS 776 760 -RSB-."
The glacifluvial gravels overlie Wilderness Till.
"At Hirst 2.2m of sandy gravel, of possible deltaic origin, rests directly on Wilderness Till."
These sands may be early Flandrian fluvial deposits and as such are best referred to the Endrick Formation.
"The Kelvin Formation includes the recent fine-grained sediments of the valley floor of the River Kelvin, Bonny Water and other rivers and streams."
Lake alluvium of Flandrian age present north-east of Glasgow and east of Bisphopbriggs at elevations between about 60 and 90m above OD is also referred to this formation.
Clay and silt of the Kelvin Formation forms much of the valley floor of the River Kelvin.
In the Kelvin valley lacustrine clay and silt deposits concealed by younger Flandrian sediments are locally present.
These deposits probably belong to the Kilmaronock Formation defined by Browne and McMillan from the Mains of Kilmaronock Borehole by Loch Lomond.
At Strone -LSB- NS 7033 7665 -RSB- a borehole record proved 2.8m of dark grey clayey silt below sand of the Endrick Formation.
"Many former excavations are infilled or partially infilled with variably compacted materials and these deposits, classified as Fill or Disturbed Ground on the Airdrie Sheet, are generally thicker than other made ground and may be in the order of tens of metres."
The Limestone Coal Formation and the Coal Measures contain most of the economic coals.
"The Hurlet Coal in the Lawmuir Formation and the Chapelgreen and Upper Hirst coals in the Upper Limestone Formation have also been worked, plus one or two minor seams in the latter."
The Limestone Coal Formation was the main source of both blackband and clayband ironstones in Sheet 31W: at least 6 seams of the former and four of the latter were exploited.
"In the Middle Coal Measures the Airdrie Blackband Ironstone was mined extensively, and the Palacecraig Blackband Ironstone was worked to some extent."
"The Cambuslang Marble, a limy ironstone packed with non-marine shells, was worked at Cambuslang -LSB- NS 646 597 -RSB- as an ornamental stone."
"The Lower Coal Measures are deficient in ironstone, but four seams were locally extracted."
The Hurlet limestone was extracted together with the Alum Shale and the Hurlet Coal.
"Mining of fireclays, mostly from the Passage Formation, began in the Garnkirk and Glenboig areas over 100 years ago and later spread along the outcrop of the formation westwards to Glasgow and north-eastwards to Castlecary."
"At Chapelhall, two seams in the Lower Coal Measures were extracted."
The Glenboig Lower Fireclay provided the bulk of the material.
"The mudstones above the Calmy Limestone have been quarried quite extensively for brick manufacture, mainly around Cumbernauld, but operations have ceased for the present."
The National Coal Board used Blantyreferme Nos. 4 and 5 mines for about 10 years to obtain a terracotta clay from the Upper Coal Measures but this operation ceased 20 years ago.
"Lavas in the Clyde Plateau Volcanic Formation at Cathkin Quarry -LSB- NS 622 583 -RSB-, alkaki olivine-dolerite sills in eastern Glasgow, quartz-dolerite dykes in several places and quartz-dolerite sills almost wherever they occur, have all been used for concrete aggregate, roadstone, kerbstones etc.."
"In Strathkelvin, sandstone of the Limestone Coal Formation was worked at Queenzieburn -LSB- NS 691 775 -RSB- NE of Kirkintilloch."
"For example, Deer Park Quarry -LSB- NS 735 539 -RSB- in the Upper Coal Measures was re-opened to provide a source of stone for the renovation of Chatelheraut Hunting Lodge -LRB- Stone Industries, 9, 1987, p. 23."
The Carboniferous strata which appear at or near surface in this district offer a wide range of hydraulic properties.
"There are also mudrocks, particularly in the Limestone Coal Formation which are weakly permeable and act as barriers to vertical groundwater movement."
"Nevertheless, groundwater has been a valuable resource for industry in the past, with abstraction notably from the Coal Measures, Passage Formation and Upper Limestone Formation."
Mine drainage records in the Limestone Coal Formation and the Coal Measures bear this out.
"Borehole yields in the Coal Measures and the older strata are, for the most part, relatively modest."
"This contrasts with the situation in Lothian District where, for example, the Passage Formation would normally offer the highest groundwater potential."
"There are no local exposures of crystalline basement from which its properties can be determined, but it can be expected to have significant contrasts with the overlying Palaeozoic sequence."
Above the basement the first principal density contrast is between cleaved Lower Palaeozoic and Lower Devonian rocks.
The second is between Lower Devonian rocks and the overlying Upper Devonian and Lower Carboniferous sedimentary rocks taken together.
The Lower Carboniferous lavas of the Clyde Plateau Volcanic Formation also have a marked contrast with the underlying and overlying sedimentary sequences.
"However, average values for the Devonian and Carboniferous successions are variable, depending particularly upon the poorly known proportions of igneous material present in the sequences, and also on the sandstone to mudstone ratios."
"The magnetic properties and the palaeomagnetic significance of igneous rocks in the district and elsewhere in the Midland Valley have been the subject of many studies, which have concentrated on the Carboniferous and Permian igneous rocks."
These inclinations are consistent with movement of the Midland Valley Terrane during Carboniferous times from low southerly latitudes to the equator.
The Hamilton Low corresponds to an area of Westphalian and older Carboniferous sedimentary rocks.
"Although the Waterhead Farm anomaly occurs over the Clyde Plateau Volcanic Formation, the thickness of the lavas in this area is insufficient to explain its amplitude."
The latter interpret the Waterhead Farm feature as being due to about 600m of Clyde Plateau Volcanic Formation.
Cotton inferred from the gradient that it marks a fault downthrowing the top of the Clyde Plateau Volcanic Formation and overlying sedimentary rocks about 140m to the NW.
Rollin attribute this low to a 2.5km thick sequence of upper Palaeozoic rocks.
"An alternative interpretation by Alomari, ascribes the Hamilton Low to a concealed granite or a 8km thick Lower Devonian basin."
The exposed Carboniferous igneous rocks in the area can not account for the anomalies and therefore the source must underlie these rocks.
There are two main geophysical current interpretations: 1 -RRB- a shallow body with properties similar to those of the Clyde Plateau Volcanic Formation extending from their base.
"The bodies in these interpretations are generally regarded as intrusions of Carboniferous and, or Devonian age."
"The anomaly pattern comprises high frequency, high amplitude anomalies over the outcrop of the Clyde Plateau Volcanic Formation, and lower frequency, low amplitude anomalies over the areas of sedimentary rocks."
"The lavas of the Clyde Plateau Volcanic Formation are associated with a dipolar anomaly at their boundary with the sedimentary rocks, with a trough to the north and peak to the south."
This indicates that in bulk the lavas have a normal total magnetisation and suggest that the NRM directions are highly scattered and consequently are probably less reliable than Carboniferous intrusions for making palaeogeographical deductions.
This suggests that the sedimentary rocks may be underlain by the Clyde Plateau Volcanic Formation.
"The sonic velocity of the Clyde Plateau Volcanic Formation is generally so much higher than that of the sedimentary rocks that its boundaries have high reflection coefficients, which prevents much energy from penetrating to greater depths."
The 800m deep top of the underlying Dinantian lavas was also detected.
Hall suggested that a reflector occurring at 1.26km was due to the base of the Clyde Plateau Volcanic Formation and that the lavas thin to the east.
"Among the reflectors were the top and bottom of about 600m of the Clyde Plateau Volcanic Formation, showing an interval velocity of 4.2 km s-1 and horizons in the Inverclyde Group and the Upper Devonian."
"The deepest identifiable reflector, at 1s two-way time, was interpreted as the top of Lower Devonian and possibly older rocks."
"Andrew reported reflection lines, north of the district, made to test penetration of Devonian lavas."
"Four main refractors are generally recognised in the Midland Valley: 1 -RRB- 0.5 - 3.0km thick Carboniferous and Upper Devonian strata, LISPB layer a1, top 7-9km deep."
"South Quarry Breccia Member, about 30m thick."
The lowest unit is the Benscliffe Breccia Member 20 to 100m thick.
The overlying Beacon Tuff Member is about 875m thick.
"At the top of the formation are predominantly volcaniclastic units commencing with the Sandhills Lodge Member, exposed south of Home Farm -LSB- 5037 1617 -RSB-."
"The overlying Buck Hills Member is a fining-upwards sequence, consisting of alternations between blue-grey, parallel-laminated, graded volcaniclastic mudstones, siltstones and sandstones."
"The Swannymote Breccia Member, some 120m thick, forms isolated outcrops in close association with Sharpley Porphyritic Dacite of the Whitwick Volcanic Complex."
"The Cademan Volcanic Breccia, up to about 450m thick, is most typically developed around Calvary Rock."
"To the south, beds of the overlying Swithland Formation contain the trace fossil Teichichnus which is considered to be no older than Lower Cambrian."
"The North Charnwood Diorites is represented by near-vertical to inclined andesitic sheets, up to 60m wide."
"A second intrusive type, the Lubcloud Microgranite, is exposed south of Ives Head summit where it occurs as a 9 m-wide north-west-trending dyke."
Stockingford Shale Group.
"Small outliers of Lower Coal Measures were proved to the north-east of the Thringstone Fault, as shown on Sheet 141 Loughborough."
The overlying sequence includes the Wingfield Flags.
"In this district, these beds are proved only in the Caldwell No. 2 Borehole, where 44.7m of strata beneath the Trias is correlated with the Etruria Formation."
"Permian strata were proved only at depth, in the north-eastern corner of the district, where the Chilwell Borehole and Central Ordnance Borehole showed, respectively, 1.6m and 14.3m of red mudstone or marl which was assigned to the Edlington Formation."
"In the Chilwell Borehole, the mudstone is overlain by 37.9m of sandstone and pebbly sandstone, of which the lowermost 20.3m may be Lenton Sandstone Formation."
The Shepshed Sandstone Member is a distinctive mappable subdivision confined to the area within and around Charnwood Forest.
The Hollygate Sandstone Member.
"The principal massive gypsum bed, the Tutbury Gypsum, commonly ranges between 3 and 5m thick."
The stratigraphically higher Newark Gypsum.
Only the Cotham Member at mapping scale represents this formation.
"The overlying Langport Member, 0.25m thick, is represented by a hard, pale grey micrite, which has only been recognised in the Normanton Hills railway cutting."
"The Elvaston Palaeochannel is largely filled with the Findern Clay, a grey to brown, horizontally laminated glaciolacustrine clay with dropstones and flow tills of Oadby Till derivation."
The Hathern Gravel from the Peak District.
"The highest and most scattered terrace patches, named the Eagle Moor Sand And Gravel although deposits reworked during o.i. Stage 10 can not be excluded."
The Cheshire Basin was selected as being representative of the basins formed in the Permo - Triassic rift systems which cut north‚ $ `` south across the British Isles and the continental shelf and which host important resources onshore and offshore.
"It is hoped that this report will not only provide new methods for assessing the resources of red-bed sedimentary basins, but also stimulate fresh discussion on all aspects of the geology of Permo - Triassic rift system basins in Britain and elsewhere."
The Cheshire Basin is a major Permo - Triassic extensional basin within a complex north‚ $ `` south-trending rift system which stretches for about 400km from the English Channel Basin in the south to the East Irish Sea Basin and beyond in the north.
"Offshore, similar Permo - Triassic rift systems underlie the North Sea."
"In Permo - Triassic times the Cheshire Basin marked a particularly rapidly subsiding segment of the rift system, and has a preserved Permo - Triassic sediment thickness of almost 4000m."
"The Permo - Triassic rocks of the basin, particularly the Sherwood Sandstone Group, have been the focus of detailed investigation because of their importance as reservoirs for hydrocarbons, water and geothermal resources."
"The Cheshire Basin was selected for detailed study because it is one of the few onshore basins with some unexplored potential for hydrocarbons, it contains important water and halite resources, and, unlike many British Permo - Triassic basins, it contains Cu-Pb-Zn mineralisation."
Modelling the formation of the ore deposits can provide considerable information on palaeo - and present-day fluid flow of importance for resource analysis of British Permo - Triassic basins generally.
"The most important occurrence is at Alderley Edge, where Cu, Pb, and Zn, with minor amounts of Ag, Co, V, Ni and Mn, occur as disseminations or in fault breccias, mainly in three conglomerate and sandstone units near the top of the Lower Triassic Sherwood Sandstone Group."
"The Permo - Triassic red beds of the UK are host to commercially valuable evaporites, including sylvite."
"Brine extraction, presently by controlled pumping in the Holford and Warmingham Brinefields, is from the Northwich Halite Formation: salt is also mined from the ‚ $ òBottom Bed‚ $ ô of this formation."
Red beds are important hydrocarbon reservoirs in many parts of the world.
"In the UK, Permo - Triassic rocks are important hydrocarbon reservoirs in the North Sea and the Wessex and East Irish Sea basins."
"Producing fields from Triassic reservoirs in basins adjacent to Cheshire, at Formby and in the East Irish Sea, together with oil shows in the Needwood Basin in the Midlands, indicate that both oil and gas have been generated over a wide area."
"In the East Midlands oilfields the source and the reservoirs are of Carboniferous age, and in this study we consider not only the prospectivity of the Permo - Triassic but also that of the Upper Carboniferous rocks beneath the Cheshire Basin."
"Permo - Triassic red beds are major sources of potable water in Cheshire, Lancashire and Nottinghamshire, and are exploited as geothermal reservoirs in the Wessex Basin."
"The Permo - Triassic sandstones are prolific aquifers, exploited largely where they are not confined by the overlying Mercia Mudstone Group and younger formations."
"Chapter 2 of the volume gives an account of the stratigraphy of the Permian to Lower Jurassic basin fill, including sections on the regional setting, biostratigraphy and sedimentology."
"Because groundwater abstraction or monitoring boreholes are heavily represented, there is a bias towards the permeable Permo - Triassic sandstone aquifer rocks around the margins of the Cheshire Basin."
"Less borehole core was available from the Mercia Mudstone Group and other formations in the centre of the basin, but MMG strata were sampled from BGS boreholes, such as Wilkesley and Crewe, and from exploration for evaporites and site-investigation boreholes."
"In addition to borehole material, the MMG was sampled underground at the Meadowbank Rock Salt Mine, Winsford."
Due to the lack of available material only a limited study was made of pre - SSG strata.
"The Collyhurst Sandstone, Manchester Marl and earlier strata were sampled from a small number of boreholes."
"In total more than 850 samples were collected during the project, of which more than 450 were from the SSG and over 300 from the MMG."
"Overviews of the tectonic development of Britain and neighbouring regions before and during the deposition of the Permo - Triassic sediments of the Cheshire Basin are given by, among others, Anderton et al.."
"During Precambrian and Palaeozoic times, the tectonics of north-west Europe were dominated by the sequential accretion of magmatic arcs and older continental fragments against and onto the stable North American craton."
"In early to middle Devonian times, oblique collision between the Laurentian and Avalonian land masses produced regional compressional deformation over much of Britain, with widespread uplift, folding and basin inversion."
"Closure of this ocean, combined with the buffering effects of various small terranes, had, by end - Carboniferous times, created the Variscides as a collision orogenic belt."
The Devonian and Lower Carboniferous sedimentary sequence in south-west England reflects a marine transgression from the south.
During Namurian and Westphalian times the Variscan thrust front advanced from the south while the flysch-like sediments of the Culm were deposited in north Devon and Cornwall.
To the north of the developing Variscan fold belt in southern Britain lay a foreland on which extensional basins developed in Carboniferous times on the northern side of a persistent Wales-London-Brabant high.
"Extension in latest Devonian and early Carboniferous times produced a series of grabens and half-grabens in the Caledonian basement, which exerted the dominant control on early Carboniferous sedimentation to the north of the high."
"In Namurian times, crustal extension progressively gave way to regional post-extensional subsidence, the early Carboniferous deposition of carbonate and detrital sediments on a block-and-basin topography being followed by the accumulation of thick, more uniform sequences of deltaic strata."
"Later in the Carboniferous, subsidence was replaced by uplift, as Variscan compressive forces became progressively more dominant."
The main effects of this regional Variscan compression were the reversal of Caledonian lines of weakness and structural inversion of the Carboniferous basins.
"Minor inversion occurred sporadically in latest Dinantian and Namurian times, but the main period of basin inversion, roughly coeval with emplacement of the Variscan thrust front, took place in Westphalian and Stephanian times."
"During Devonian times, a hot semi-arid climate prevailed over much of the North Atlantic area, Britain lying close to the equator."
"Though Britain remained near the equator throughout the Carboniferous and early Permian, the climate changed from arid in the earliest Dinantian to semi-arid and then monsoonal in later Dinantian times."
"Later in the Carboniferous, an increasingly humid tropical climate prevailed over much of north-west Europe, which ended in latest Westphalian to Stephanian times when the evidence of red beds and oxidised coal seams indicates the onset of the lengthy Permo - Triassic arid period."
"During Permo - Triassic times, northern Europe lay within the arid hinterland of the Pangaean supercontinent, newly formed by the collision of Laurasia and Gondwana."
"Marine incursions entered from the north-west in Late Permian and Mid and Late Triassic times, and from the south and west at the end of the Triassic."
"The Permo - Triassic fill rests unconformably on, or is in faulted contact with, folded Carboniferous and older rocks and is contiguous with the fill of the East Irish Sea Basin to the north-west, and the Stafford, Needwood and Worcester basins to the south-east and south."
"The basin fill comprises formations assigned to the Appleby, Cumbrian Coast, Sherwood Sandstone, Mercia Mudstone, Penarth and Lias groups."
"Around the northern, western and southern margins of the basin the fill rests on folded and faulted pre - Permian rocks in age though Ordovician rocks occur at the south-western margin, south of Oswestry."
"Nearly 50km to the north-north-east, Carboniferous shales, sandstones and coals of Westphalian age were proved from c. 2820mKB to TD."
A small inlier of Carboniferous rocks has been proved near Chester.
A summary account of the distribution and structures of the pre - Permian rocks of the basin floor and in the surrounding area is given on pp.55-67.
"At the beginning of the Permian, Britain lay deep within the Pangaean supercontinent, in a belt of easterly winds and situated within a few degrees of the equator."
"The sands were deposited on an uneven erosional surface of mainly Carboniferous rocks, and this surface was further modified by syndepositional faulting."
"Early in the Late Permian, a marine incursion from the north-west into the northern part of the Cheshire Basin led to the deposition of the dolomitic and gypsiferous mudstones of the Manchester Marls Formation."
"In the southern part of the basin at this time, the Bold Formation represents a continuation of the conditions that obtained during the deposition of the Collyhurst Sandstone."
"Towards the end of the Permian, the sea retreated and the Bold and Manchester Marls formations were succeeded by the Kinnerton Sandstone."
"Marine conditions persisted for longer in the area of the East Irish Sea, with the deposition of the St Bees Shales and Evaporites."
"The Kinnerton Sandstone Formation consists dominantly of aeolian sands, though evidence of fluvial action suggests the presence of rivers in the interdune areas."
Similar conditions continued into the Triassic.
The Kinnerton Sandstone was succeeded by conglomerates and sandstones of the Chester Pebble Beds Formation.
"The abundance of pebbles decreases northwards: pebble beds extend into the south-eastern extremity of the EISB, beyond which lie fluvial sandstones similar to the Wilmslow Sandstones which, in the Cheshire Basin, overlie the Chester Pebble Beds."
"The Wilmslow Sandstone Formation consists of sandstones, with some siltstones and mudstones, deposited from the north-west-flowing river system, and also features dunes formed by easterly winds."
"The succeeding beds of the Bulkeley Hill Sandstone Formation are only locally present, and their deposition was followed by a period of faulting and erosion, now marked by the Hardegsen disconformity."
"The Helsby Sandstone Formation and its correlative in the EISB, the Ormskirk Sandstone Formation, were deposited on the Hardegsen erosion surface, under the influence of easterly winds and rivers from the south-east."
"The Tarporley Siltstone Formation, the lowest formation of the MMG, was laid down in intertidal and playa environments and marks a transition to less sandy deposits."
Subsidence accompanied by movement along contemporary faults continued until Carnian times.
The MMG in the EISB is broadly similar to that in the Cheshire Basin.
"The Blue Anchor Formation, at the top of the MMG, closely resembles the laminated facies of the Brooks Mill Mudstone, being composed of wind-blown detritus deposited in shallow water, except that it consists almost entirely of reduced facies: terrestrial and/or freshwater life may have been more prolific, perhaps because of a more reliable rainfall."
"The Penarth Group consists of mudstones, fine sandstones and limestones with marine fossils, and this fauna became more diverse in the overlying Lias Group."
"In its most complete form, in the northern part of the basin, the fill comprises the Appleby, Cumbrian Coast, Sherwood Sandstone and Mercia Mudstone groups: to the south, younger deposits of the Penarth Group and the lower part of the Lias Group are also present."
The Collyhurst Sandstone Formation where it rests unconformably upon Carboniferous rocks and is overlain conformably by the Manchester Marls Formation.
"Further south in the basin the formation becomes almost indistinguishable from the overlying Manchester Marls where the latter pass laterally into a more silty or arenaceous facies, as recognised in the Prees Borehole."
"Where these formations become indistinguishable, their correlatives are regarded as forming the lower part of the Kinnerton Sandstone Formation of the Sherwood Sandstone Group."
"The Collyhurst Sandstone is of continental, aeolian, origin."
"Further south, in the Stafford and Worcester basins, the lower part of the aeolian Bridgnorth Sandstone Formation is equivalent to the Collyhurst Sandstone."
"The Bridgnorth Sandstone is interpreted as having accumulated in a combination of transverse and barchanoid draas, with superimposed oblique crescentic and linear dunes, under the influence of fluctuating winds from a predominantly easterly direction."
"To the north-west, in the EISB, the Collyhurst Sandstone comprises mainly aeolian deposits."
"There is no direct evidence for the age of the Collyhurst Sandstone, but the youngest underlying beds are Late Carboniferous."
The Collyhurst Sandstone is thus constrained only within the post - Westphalian to pre - Kazanian interval.
The Manchester Marls rest on the Collyhurst Sandstone or locally overlap that formation and rest unconformably on Carboniferous rocks.
"The Manchester Marls comprise red, rarely green, dolomitic and gypsiferous mudstones."
"Upwards, the formation becomes more arenaceous and passes into the Kinnerton Sandstone Formation of the SSG."
A concealed development of the Manchester Marls extends south for at least 40km from the outcrops at the northern end of the basin.
Elsewhere the formation is indistinguishable from the underlying Collyhurst Sandstone and merges with the equivalent of that formation to form the lower part of an arenaceous sequence assigned to the Kinnerton Sandstone Formation.
An interbedded succession of aeolian sandsheet deposits and fluvial sheetflood facies in the Speke Reservoir Borehole is attributed to the Bold Formation.
"Regional studies show that the Manchester Marls accumulated marginally to a depocentre sited to the north-west, in the EISB."
"The age of the Manchester Marls is, on biostratigraphic evidence, Late Permian."
"The formations of this group have an extensive outcrop in the Cheshire Basin, almost surrounding that of the Mercia Mudstone Group and younger deposits."
The upward increase in sand content in the Manchester Marls and the transition into the sandstones of the SSG reflect palaeogeographical changes that resulted in the exclusion of marine influences from the northern part of the Cheshire Basin and the neighbouring EISB.
"The Chester Pebble Beds, Wilmslow Sandstone and Bulkeley Hill Sandstone were deposited under continental conditions as parts of a dominantly fluvial facies association that spread northwards from southern England, through the Worcester, Stafford and Cheshire basins, into the EISB in Early Triassic times."
The Bulkeley Hill Sandstone and Wilmslow Sandstone are progressively cut out at an unconformity at the base of the Helsby Sandstone.
"Evidence of the regional nature of this unconformity, and of its presence within the concealed SSG in the Cheshire Basin, has been compiled from geophysical studies."
"Above the unconformity, the Helsby Sandstone reflects the re-establishment, in the early Mid-Triassic, of a continental fluvial system which drained northwards into the EISB."
"Continental sedimentation in the EISB was superseded by the deposition of fine-grained sediments with evaporites, which form the lowest part of the MMG and were deposited partly in water of marine origin."
"During Mid-Triassic times this environment, and the area of MMG deposition, expanded southwards to occupy the Cheshire Basin and other areas further south in England where the SSG had accumulated previously."
"The Kinnerton Sandstone lacks fossils, but, because of its lateral equivalence to the aeolian Collyhurst Sandstone and the partly marine Manchester Marls, it is regarded as largely Permian in age."
The thickness of the Kinnerton Sandstone increases southwards from 73m in the Knutsford Borehole to 110m in the Prees Borehole: this trend parallels a thinning of the underlying Manchester Marls and may reflect the southward passage of the upper part of that formation into more arenaceous beds.
"Palaeowind vectors indicate that the Kinnerton Sandstone, like the Collyhurst Sandstone, was deposited under the influence of winds from an easterly direction."
In the Chester district from Permian aeolian deposits in the North Sea Basin.
"In the Chester district, 14m of very micaceous sandstones, described by Thompson as at the ` predicted horizon ' of the Manchester Marls, forms a transition upwards into the Chester Pebble Beds."
"These sandstones may correlate with the Bold Formation, a unit recognised by geologists of the North West Water Authority in the Runcorn district."
The Chester Pebble Beds Formation is recognised at depth in the Prees and Knutsford boreholes.
"Elsewhere, it locally rests unconformably on the Bold Formation, Manchester Marls, Collyhurst Sandstone and Carboniferous rocks and, in the south-eastern part of the basin, is overlain unconformably by the Helsby Sandstone."
"The Chester Pebble Beds comprise conglomerates, pebbly sandstones and sandstones and are of continental origin."
"North-westwards, into the EISB, the formation shows a decrease in pebble content and becomes indistinguishable from sandstones of the overlying Wilmslow Sandstone Formation."
"Beyond the limit of the occurrence of pebbles in the Chester Pebble Beds, the lateral equivalents of that formation and the Wilmslow Sandstone occur in the St Bees Sandstone Formation."
Thompson are equivalent to the Bold Formation.
"No stratigraphically useful fossils are known from the Chester Pebble Beds which, from their position above the Late Permian Manchester Marls are assessed as Early Triassic in age."
It rests on the Chester Pebble Beds: at outcrop in west Cheshire and within the basin it is succeeded by the Bulkeley Hill Sandstone Formation.
"Elsewhere the Bulkeley Hill Sandstone is overlapped by the Helsby Sandstone which comes to rest unconformably on, or completely cuts out, the Wilmslow Sandstone."
"The Wilmslow Sandstone comprises predominantly red, fine-grained, argillaceous, cross-bedded sandstones, with some interbedded siltstones and mudstones."
The Wilmslow Sandstone lacks stratigraphically useful fossils.
"From its position beneath an inferred representative of the Hardegsen disconformity, which affects beds high in the Middle Bunter of Germany Helsby Sandstone, the Wilmslow Sandstone is assessed, with the Chester Pebble Beds, as Early Triassic in age."
It succeeds the Wilmslow Sandstone conformably but is overlapped by the Helsby Sandstone above an unconformity that was correlated.
"Evidence of the presence of this unconformity within the concealed SSG in the Cheshire Basin, and of the concealed extent of the Bulkeley Hill Sandstone, has been compiled from geophysical studies which suggest a maximum thickness for the formation of about 220m towards the basin centre."
"It lacks fossils, but its stratigraphical position is analogous to that of the Wilmslow Sandstone and it is similarly assessed as Early Triassic in age."
"This formation has an almost continuous, though faulted, outcrop which fringes that of the MMG in the northern, western and southern parts of the basin."
The Helsby Sandstone was proved at depth in the Prees and Knutsford boreholes.
"It succeeds the Wilmslow Sandstone and Bulkeley Hill Sandstone unconformably and is overlain, conformably, by the Tarporley Siltstone Formation, the lowest formation of the MMG."
The stratigraphy and sedimentology of the Helsby Sandstone in the Cheshire Basin have been studied by Thompson.
"The Soft Sandstones, of fluvial, fluvio-lacustrine and aeolian origin, occur principally in the Wilmslow Sandstone but are also present in the Helsby Sandstone."
"The Red Pebbly Sandstones, representing fluvial - channel and associated overbank deposits of low - to moderate-sinuosity stream systems, occur in the Chester Pebble Beds and the Helsby Sandstone."
Thompson proposed division of the Helsby Sandstone into members distinguished by the predominance of fluvial or of aeolian sediments.
"The principal members are the Thurstaston Soft Sandstone Member, the Delamere Pebbly Sandstone Member, and the Frodsham Soft Sandstone Member which occur broadly in that stratigraphical order."
The Helsby Sandstone is 230m thick in the Prees Borehole and 205m at Knutsford.
"In the early stage of Helsby Sandstone sedimentation, braided river channels were the sites of deposition of pebbly transverse sand bars and dunes and some pebbly channel deposits during high-discharge phases."
Sediments of the Thurstaston Member facies accumulated between these distributaries and are more widely developed across the basin: they comprise low-energy fluvial sands and some possible aeolian dunes that formed on dry interdistributary tracts.
"The succeeding stage of Helsby Sandstone sedimentation witnessed the more widespread deposition of pebbly fluvial sands, of the Delamere Member facies, in distributaries of low to moderate sinuosity."
"Subsequently, fluvial deposition waned substantially and aeolian deposits of the Frodsham Member facies dominated the basin: localised fluvial deposits formed in discrete distributary channels, mainly in the eastern part of the basin."
In the EISB the equivalent beds are termed the Ormskirk Sandstone Formation recognised five major facies associations.
Palaeogeographical interpretations for similar associations in the Helsby Sandstone in the Cheshire Basin.
"The age of the Helsby Sandstone is, on biostratigraphic evidence, early Mid-Triassic."
"In the absence of stratigraphically significant fossils from formations lower in the SSG, the position of the Permian - Triassic boundary is poorly constrained."
"In the northern part of the basin it is within some 1200m of strata between the highest fossiliferous beds in the Manchester Marls and the base of the Helsby Sandstone: it may, therefore, occur within the topmost Manchester Marls or the lower part of the SSG."
Further south in the basin it is considered to occur within the Kinnerton Sandstone.
"This group has an extensive outcrop, enclosing the outliers of the Penarth and Lias groups in the southern part of the basin and almost surrounded by the outcrop of the SSG."
"The MMG comprises six predominantly fine-grained clastic formations, the Tarporley Siltstone, Bollin Mudstone, Byley Mudstone, Wych Mudstone, Brooks Mill Mudstone and Blue Anchor formations, and two halite - bearing units."
"The lower halite - bearing unit, the Northwich Halite Formation occurs between the Bollin and Byley mudstones, and the upper unit, the Wilkesley Halite Formation, between the Wych and Brooks Mill mudstones."
The MMG succession in the Cheshire Basin was first demonstrated in the Geological Survey Wilkesley Borehole.
The mudstone formations in the MMG include structureless and laminated units.
"The former constitute the bulk of the Wych and Brooks Mill mudstones and the lower part of the Bollin Mudstone, and also occur within the Byley Mudstone."
Laminated beds are dominant in the upper part of the Bollin Mudstone and also occur in the Byley Mudstone.
"The lowest formation in the MMG, it is at least 280m thick in the Ashley Borehole -LSB- 7738 8355 -RSB-, south of Altrincham and between 200 and 230m thick in several boreholes elsewhere in the Cheshire Basin."
The multiple seismic reflector associated with the Helsby Sandstone - Tarporley Siltstone succession is identifiable widely in the Cheshire Basin.
"Towards the basin edge, however, 100m is a more common thickness for the Tarporley Siltstone, with a likelihood that the unit thins out locally on the eastern fringe near Alsager."
"The Tarporley Siltstone comprises a distinctive facies that consists of alternating siltstones, reddish brown and greenish grey mudstones and thin fine - to medium-grained sandstones: desiccation surfaces and pseudomorphs after halite point to arid conditions."
"This unit, the Malpas Sandstone, contains abundant wind-blown grains but includes water-laid sandstone, with current-ripple lamination and clasts of mudstone."
"In the south-eastern part of the basin, near Norton in Hales -LSB- 720 380 -RSB-, beds of Tarporley Siltstone facies alternate with up to six sandstone units some 20 to 30m thick, of both aeolian and subaqueous origin, with rip-up clasts and cross-bedding."
These strata have been assigned to the Helsby Sandstone in recent BGS mapping.
"The formation is defined as the beds between the highest sandstone interbed at the top of the Tarporley Siltstone and the base of the first bed of halite over 2m in thickness, marking the base of the Northwich Halite."
"The type section is in the banks of the River Bollin -LSB- 7953 8453 to 8281 8350 -RSB-, close to Manchester Airport."
In the northern half of the basin there is commonly a repetition of the Tarporley Siltstone facies in the overlying Bollin Mudstone.
"The formation probably exceeds 500m in thickness at the depocentre, which extends from the Northwich area, south-westwards to Wych Brook."
"The upper part of the Bollin Mudstone is seen in a number of scattered sections along the river Bollin and in Wych Brook, near Malpas."
"An insect wing and the branchiopod Euestheria minuta from Giant 's Castle Rocks, the best exposure on the Bollin."
"The thickest known development, of 283.2m, is in Byley Borehole -LSB- 7207 6942 -RSB-."
"Similarly, to the south-west, in Wych Brook, the narrow width of the collapsed zone overlying the halite suggests attenuation of the formation."
Earp and Taylor estimated that some 25% of the Northwich Halite consists of mudstone.
Further evidence that deposition of the Northwich Halite was in shallow water comes from laboratory experiments and studies of core by Arthurton.
The bromine content of the Northwich Halite suggest a marine origin for the brines.
"The Byley Mudstone, the lower part of the former ` Middle Keuper Marl ' and the ` middle mudstone division of the MMG ' in the Cheshire Basin comprises a distinctive alternation of laminated and structureless mudstones and varies from 150 to 182m in thickness."
The contact with the overlying Wych Mudstone is taken at the top of the highest substantial laminated greenish grey unit.
"The type section is in the Byley Borehole -LSB- 7207 6942 -RSB-, which also shows the thickest development and appears to lie near the depocentre for a combination of the two formations."
"The strata are best known from boreholes, but the lowermost beds are seen in the River Dane -LSB- 8808 6536 -RSB- and the uppermost in Wych Brook."
"At surface, these beds weather to a sticky red clay and are seen in scattered cliffs in the valleys of Wych Brook -LSB- 4887 4469 to 4931 4530 -RSB- and on the River Dane west of Congleton -LSB- 7870 6766, 8469 6407 -RSB-."
The Wilkesley Halite is the thicker of the two saliferous formations in the Cheshire Basin.
"The only complete penetrations of the Wilkesley Halite are in the Prees Syncline, where the unit was 404.50m thick in the Wilkesley Borehole and about 350m in the Prees Borehole."
The upper half of the formation is somewhat purer than the average analysis for the Northwich Halite.
"The Wilkesley Halite contains four significant sandstone beds 0.3 to 1.65m in thickness, as well as a few thinner sandstone layers, all within the mudstone partings."
"In contrast, there are no sandstone beds in the Northwich Halite."
"Besides the main outcrop in the Prees Syncline, further occurrences of the Wilkesley Halite in and west of Nantwich were proved in the Burland Borehole -LSB- 6018 5333 -RSB- and probably in the area 5km south of Crewe, on the evidence of subsidence hollows and seismic reflection data."
"An outlier around Sandbach, restricted to the lower beds of the formation, marks the site of the only exploitation of brine from the Wilkesley Halite in the present century."
"Since the Wilkesley Halite is not seen in mines and there are no specimens of any of the clastic interbeds, less is known about the likely origin of this formation than that of the Northwich Halite."
"Much of the lower part of the Wilkesley Halite does, however, consist of haselgebirge, a lithology known to have been deposited in shallow water during the deposition of the Northwich Halite."
"This formation, the former ` Upper Keuper Marl ', is generally drift-mantled and is named from small exposures -LSB- 6296 4370, 6315 4384 -RSB- near Brooks Mill on the south bank of the River Weaver."
The base of the formation is at the top of the highest halite bed in the Wilkesley Halite and the top is placed at the incoming of the greenish grey mudstones of the Blue Anchor Formation.
The Brooks Mill Mudstone consists dominantly of structureless reddish brown mudstones with anhydrite or gypsum nodules.
"The structureless mudstones which dominate this formation are, like those in the Wych Mudstone, probably largely of aeolian origin."
"The Blue Anchor Formation comprises poorly laminated, greenish grey mudstones, with some chocolate-coloured mottling and a transitional colour change to reddish brown at the base."
The MMG successions in the Cheshire Basin and the adjacent EISB show an increasing degree of similarity at progressively higher levels in the sequence.
"The lowest formation, the Tarporley Siltstone of Cheshire and its approximate equivalent on palynological grounds, the Hambleton Mudstone Formation on the eastern margin of the EISB, show little similarity of facies."
"The lower half of the Bollin Mudstone of Cheshire, like the Singleton Mudstone Formation of Blackpool, contains much structureless reddish brown mudstone, but there may be rather more laminated strata in Cheshire."
"The upper half of the Bollin Mudstone, like the Thornton Mudstone Member of Blackpool in the EISB, consists very largely of interlaminated mudstones and dolomitic siltstones, with abundant desiccation cracks and pseudomorphs after halite."
"The Northwich and Preesall halites were, on palynological evidence, laid down at about the same time and it is possible that the two basins had become a single depositional area by then."
"The Northwich Halite does not persist eastwards into the Stafford Basin, however."
"The Byley Mudstone, which overlies the Northwich Halite, is closely similar to the Coat Walls Mudstone Member of Blackpool."
"However, palynological evidence suggests that, despite the close lithological similarities, the Anisian - Ladinian boundary lies closely above the base of the Coat Walls Mudstone Member in the Blackpool area."
The Wych Mudstone of Cheshire closely resembles the Breckells Mudstone Formation of the EISB in the abundance of gypsum and anhydrite nodules in structureless reddish brown mudstone.
"The Wilkesley Halite of Cheshire is the thicker of the two great salt deposits and is represented to the south-east, in the Stafford Basin, by the Stafford Halite."
"The equivalent of the Brooks Mill Mudstone of Cheshire is not preserved on land at the eastern margin of the EISB, but is almost certainly present in the same facies offshore."
"There is similar widespread similarity of facies at the level of the Blue Anchor Formation, though this has not yet been verified in the EISB."
"The presence of the Penarth Group, formerly the ` Rhaetic '."
The outliers of those beds and the succeeding Lias Group in the Prees and Frith Farm areas of the Nantwich and Wem districts.
The Penarth Group comprises the Westbury Formation and the succeeding Lilstock Formation.
"The Penarth Group rests on a minor unconformity, represented by an erosion surface at the top of the MMG, and is succeeded conformably by the Lias."
"The age of the group is, on biostratigraphical evidence, late Late Triassic."
Rocks of the Lias Group were first noted in the Cheshire Basin by Murchison.
The Prees Borehole proved 597m of beds here assigned to the Lower Lias.
"The Lias comprises dominantly grey fissile mudstones, shales and thin limestones, and was deposited in a marine environment."
"The succession in the Prees outlier is, on biostratigraphic evidence, latest Triassic in age."
The boundary between the Triassic and Jurassic systems is placed at the level of the appearance of ammonites of the genus Psiloceras.
"Biostratigraphical information is available for the Manchester Marls Formation, the Helsby Sandstone Formation, the MMG, and the Penarth and Lias groups."
The Manchester Marls Formation has yielded plant remains.
The fossil associations are comparable to those known from the Zechstein and are indicative of a Late Permian age.
The occurrence of the pollen Lueckisporites virkkiae in the Manchester Marls at Manchester.
The basal member of the Helsby Sandstone at Alderley Edge -LSB- 859 774 -RSB-.
Fossils are commoner in parts of the MMG than in the SSG in the Cheshire Basin.
Records of spores and pollen from independently dated Triassic successions elsewhere in Europe provide a basis for the dating of part of the MMG succession in the Cheshire Basin.
The base of the Anisian Stage is marked by the lowest occurrences of Stellapollenites thiergartii and Angustisulcites spp.
The highest occurrence of S. thiergartii and the lowest occurrence of Ovalipollis pseudoalatus are at or just above the Anisian - Ladinian boundary.
"Miospore assemblages from the MMG in the Cheshire Basin indicate, by reference to the above criteria, that the Anisian succession extends upwards from the Helsby Sandstone to a level above the Northwich Halite."
"In addition to occurring in the basal Helsby Sandstone at Alderley Edge, Angustisulcites spp."
"are recorded, together with Stellapollenites thiergartii and other taxa, such as Perotilites minor, that are indicative of an Anisian age, from the overlying Tarporley Siltstone at Liverpool."
Palynological evidence of an Anisian age has also been obtained from the Tarporley Siltstone in the Chester district.
"Assemblages containing Angustisulcites spp., P. minor and S. thiergartii have also been recovered from the Bollin Mudstone, and Angustisulcites spp."
"occurs with Tsugaepollenites oriens in the upper part of the Byley Mudstone, which is now assessed as late Anisian in age."
The palynological evidence suggests that the Anisian - Ladinian boundary lies at the top of the Byley Mudstone.
Few miospore assemblages have been recovered from higher levels in the MMG.
"The Wilkesley Halite may, on very sparse palynological evidence, span the Mid to Late Triassic in age."
There is no satisfactory biostratigraphical evidence for the age of the succeeding Brooks Mill Mudstone and Blue Anchor formations.
The succession between the Wilkesley Halite and the Penarth Group is therefore considered to be Late Triassic and to comprise beds of Norian and probably early Rhaetian age.
Anderson recorded ostracods from the Penarth Group of the Plattlane Borehole.
The base of the Jurassic is placed at the level of the appearance of ammonites of the genus Psiloceras this occurs 9.37m above the base of the Lias.
The youngest unit in the Lias succession preserved in the Prees outlier is of late Pliensbachian.
The preserved fill ranges in age from Early Permian.
"The poorly constrained lower part of the fill, comprising the Collyhurst Sandstone, Manchester Marls, Chester Pebble Beds and Wilmslow Sandstone formations, comprises nearly 1900m of mostly coarse clastic sediments that accumulated during a maximum time of 58¬ ± 5Ma."
The part of this sequence comprising the Late Permian Manchester Marls and the succeeding units below the Mid-Triassic Helsby Sandstone accumulated in about 18¬ ± 5Ma and is represented by some 1300m of sediments.
The succession comprising the Manchester Marls and beds up to and including those of Anisian age above the Northwich Halite spans approximately 25¬ ± 5Ma and is represented by more than 2300m of sediments.
"The Anisian succession comprises more than 1000m of sandstones, mudstones and evaporites that accumulated in as little as 7Ma."
"The remainder of the MMG, together with the Penarth Group and basal."
The 600m of Jurassic rocks preserved in the basin accumulated over a period of some 18Ma.
During this phase the SSG and part of the MMG accumulated under conditions of fault-controlled subsidence.
The boreholes contained strata ranging from the Collyhurst Sandstone to the Tarporley Siltstone.
"Detailed logs of boreholes through the MMG are summarised by Wilson and in Figures 12, 13, 14, 16, 18, 19, 20 and 21."
"The Manchester Marls Formation was not present in any of the boreholes studied, but a 10m sandstone unit underlying the Chester Pebble Beds in the Speke Reservoir Borehole is attributed to the Bold Formation."
"If this attribution is correct, the overlying Kinnerton Sandstone must have been eroded in this area."
The Thurstaston Soft Sandstone Member was examined in the Gallantry Bank boreholes.
"The Delamere Pebbly Sandstone Member was examined in the Gallantry Bank and Saughall Massie boreholes, where it consists of interbedded fine -, medium - and medium - to coarse-grained sandstones with subordinate claystones and siltstones, interpreted as deposits of low-sinuosity fluvial channels."
"The Frodsham Soft Sandstone Member in the Saughall Massie Borehole is an orange-brown, fine - to medium-grained, poorly cemented sandstone."
A 95m sequence of the Tarporley Siltstone was examined from the Saughall Massie Borehole.
"A colour-shaded gravity image of the basin illustrates its gross morphology, the Permo - Triassic basin fill corresponding closely to a large negative gravity anomaly."
"During early Palaeozoic times, present-day Precambrian inliers such as those of the Longmynd probably formed elevated areas around the margin of the Welsh Basin."
"Thin sequences were deposited here, Tremadocian and Caradocian strata being the only Ordovician rocks preserved."
"A thicker, more complete Cambrian ‚ $ `` Silurian sequence was deposited west of the Pontesford ‚ $ `` Linley Fault, which is interpreted as a down-west syn-sedimentary fault."
"Ordovician rocks in the Welsh Basin are associated with arc volcanics, whereas Silurian rocks are turbidites derived from the rising Caledonides in the west, and probably shed into a foreland basin."
"The Pontesford ‚ $ `` Linley Fault probably developed in Cambrian times, ceasing normal movement in the late Ordovician."
"From then to late Llandovery times, basin inversion occurred, with reversal of the Pontesford ‚ $ `` Linley Fault and development of the Shelve Anticline."
"Preservation of Caradoc rocks in a depression east of the Pontesford ‚ $ `` Linley Fault, unconformably overlying both Uriconian and Longmyndian rocks, suggests that basin inversion occurred soon after Caradoc times."
"Cambrian and Tremadoc rocks probably subcrop beneath the Carboniferous rocks west of the Pontesford and Hodnet faults as far as the Prees Borehole, consistent with late Ordovician basin inversion beneath the southern part of the Cheshire Basin."
"A borehole in the Hanwood Coalfield penetrated Coal Measures, which rest on a ? Cambrian sandstone."
"Upper Llandovery strata are unconformable on rocks of Longmyndian to Ordovician age, and thicken eastwards towards the Pontesford ‚ $ `` Linley Fault, indicating some reactivated downthrow to the west."
"It is likely that a Silurian basin lay to the north of the Shelve inlier, as well as to the south, where littoral deposits were described by Whittard."
Much of the Welsh Basin and the subsurface to the north-east are devoid of rocks of Devonian age.
The first was associated with the late Ordovician basin inversion.
"The second, Acadian, event, in early to mid - Devonian times, uplifted the whole Welsh Basin."
Reactivation of this structure appears to have strongly influenced both Carboniferous and Permo - Triassic structural development of the Cheshire Basin.
"The plate-tectonic process which most strongly influenced Carboniferous structural development of the Cheshire Basin region was the formation, several hundred km to the south, of a collision-type orogenic belt in the Iberian‚ $ `` Armorican‚ $ `` Massif Central region of the Hercynides."
"Broadly speaking, Carboniferous basin development in the Cheshire Basin region can be split into two main phases."
"In early Carboniferous times, rapidly subsiding fault-controlled extensional basins developed between structurally elevated, largely emergent blocks."
"This was followed, in late Carboniferous times, by more regional subsidence, which was characterised by a lack of major fault control and led to submergence and depositional onlap of the earlier structural highs."
Details of Carboniferous basin development are sketchy because the seismic reflection data do not image the Carboniferous sequence effectively.
Comparison with the better described early Carboniferous extensional basins of northern England suggests that an extensional Carboniferous basin underlies the Permo - Triassic Cheshire Basin.
"It is, moreover, likely to have a geometry markedly different to the overlying Permo - Triassic basin, given the roughly orthogonal extension directions."
Structural trends of the principal early Carboniferous faults were strongly influenced by the structural grain of the underlying basement.
"In latest Carboniferous times, final closure of the Rheic Ocean culminated in the Variscan Orogeny, with large-scale thrust and nappe emplacement and regional crustal shortening in northern France, Belgium, southern England, South Wales and southern Ireland."
"Variscan deformation was much less pervasive here, being largely restricted to the reversal of pre-existing Dinantian normal faults and associated basin inversion."
The main Variscan movements in the Cheshire Basin region probably postdated the preserved Westphalian rocks and predate deposition of the Permian strata which rest unconformably on the Carboniferous beds.
"Dating the precise onset of the main Variscan movements is difficult, but evidence from central England suggests that inversion may have commenced as early as Westphalian C times."
"The main effect of Variscan compression in the region appears to have been reversal of important Caledonian lines of weakness and associated early Carboniferous faults, which led to structural inversion of the Carboniferous basins."
"Evidence of this comes from the south-east margin of the Cheshire Basin, where seismic reflection data show west-dipping reflections between 0.1 and 0.65s two-way travel time, beneath the Permo - Triassic cover."
Seismic character and regional correlation suggest that these reflections correspond to concealed Westphalian Coal Measures.
"Their relationship to the Carboniferous succession imaged at the extreme eastern end of the line, where the Keele Formation outcrops, suggests that the formations are separated by a down-east reverse fault."
"Precise displacement of the Westphalian strata is difficult to assess, because of their complex structure and uncertain seismic character matches."
"In the footwall of this fault, other, smaller, down-east reverse faults displace the Coal Measures and Barren Measures."
"A few km to the south, seismic reflection and gravity data show the sub - Permian basement structure along Section 4 of Figure 38."
"Carboniferous strata pinch out eastwards beneath the Wem ‚ $ `` Audlem Sub-basin, with Lower Palaeozoic rocks forming the pre - Permian subcrop on the hangingwall block of the Wem Fault."
"In contrast, east of the Wem Fault, on its footwall block, the gravity interpretation, indicate that thick Carboniferous strata occur beneath the Permo - Triassic cover."
Variscan reversal of the Wem Fault led to uplift of its hangingwall block and inversion of the Carboniferous basin.
"The Edgerley Fault, in the western part of the basin may also be associated with reactivation of the Bala Fault, another important Caledonian, Carboniferous and Variscan basement structure."
"By earliest Permian times, Variscan continental collision had led to final suturing and consolidation of the Pangaean supercontinent."
"Variscan basin inversion and regional uplift had resulted in considerable elevation of the land surface, which, during Permian times, underwent progressive peneplanation."
"By late Permian, and, particularly, early Triassic times, the north-west European region formed an isthmus between the rapidly developing Arctic‚ $ `` North Atlantic rift system to the north and the Tethys‚ $ `` Central Atlantic‚ $ `` Gulf of Mexico rift-wrench system to the south."
The Cheshire Basin formed part of a Permo - Triassic rift system which extended from the English Channel Basin in the south to the East Irish Sea Basin in the north.
The post - Triassic evolution of the Cheshire Basin is poorly understood because of the paucity of preserved strata.
"It is likely, however, that regional crustal extension continued episodically, prior to the onset of North Atlantic sea-floor spreading in mid - Cretaceous times."
"Regional considerations, and, particularly, evidence from more fully preserved sedimentary sequences to the south, indicate that extensional basin subsidence continued into early Jurassic times."
Renewed extension in the late Jurassic and early Cretaceous was associated with sea-floor spreading in the southern part of the North Atlantic region as Iberia and America separated.
Erosion associated with development of the widespread late Cimmerian unconformity is likely to have affected much of the Cheshire Basin region in the early Cretaceous.
"Most of any lower Cretaceous deposits, together with a substantial thickness of Jurassic and possibly Triassic strata, are likely to have been removed at this time, particularly from the basin edges."
"Deposition recommenced in the late Cretaceous, as regional, post-extensional shelf subsidence became established, with deposition of the laterally uniform Chalk."
"Basin inversion, not necessarily contemporaneous with the regional uplift, corresponded to one or more of three inversion episodes in southern Britain: the late Cretaceous inversion in the southern North Sea."
"Well-documented cases of basin inversion reasonably close to the region include the Sole Pit Trough, where the main phase of inversion occurred in Oligo - Miocene times, corresponding to major Alpine nappe development."
"The detailed structure of the Cheshire Basin and aspects of the Permo - Triassic and subsequent phases of basin evolution, are examined in more detail below."
The MMG is imaged as a seismically banded sequence.
The Bollin Mudstone and Tarporley Siltstone formations and the Helsby Sandstone Formation of the underlying SSG can usually be identified as groups of moderate - to high-amplitude continuous reflections.
"The Permo - Triassic succession beneath the Helsby Sandstone Formation gives rise to a seismically layered interval, within which three poorly reflective zones are developed, corresponding to the Wilmslow Sandstone, Chester Pebble Beds and Collyhurst Sandstone formations."
"These three transparent zones are separated by two layers of high-amplitude, coherent reflections, corresponding to the top of the Silicified Zone within the Wilmslow Sandstone Formation and Kinnerton Sandstone formations."
"The base of the Permo - Triassic succession is in places marked by a high-amplitude, continuous event, commonly associated with truncation of underlying reflections from Westphalian strata."
"This characteristic seismic stratigraphy, together with data from many shallow boreholes and the surface geology, enables Permo - Triassic reflectors to be identified across much of the basin with a fair degree of precision."
"In the north-west of the basin however, seismic data are of generally poorer quality, with the base of the Permo - Triassic succession and, in particular, the base of the SSG being somewhat uncertain."
"Most of these smaller faults penetrate to the surface: throws are typically in the range 100‚ $ `` 500m and tend to decrease upwards, indicating both Permo - Triassic and probable post - Triassic syndepositional movement."
"Curved listric fault geometry is developed only locally, and evidence of faults detaching onto the salt units of the MMG is sparse."
"The deepest parts of the Cheshire Basin are presently within the Wem ‚ $ `` Audlem and Sandbach‚ $ `` Knutsford sub-basins, where the pre - Permian basement lies at depths greater than 4000m."
"Pre - Permian basement lies at depths greater than 4500m in the hangingwall block of the Wem Fault, west of the Prees Borehole, and greater than 4250m in the hangingwall block of the Bridgemere Fault, south-east of the Burford Borehole."
"The Permian, SSG and MMG all thicken south-east into the sub-basin, indicating that it developed as a structural feature throughout the extensional phase of basin evolution, by contemporaneous normal displacements on the Wem and Bridgemere faults."
The two areas in the Wem ‚ $ `` Audlem Sub-basin where the pre - Permian basement is at the greatest depth appear to have had significantly different structural histories.
"Whereas the base of the SSG and MMG and the base of the Jurassic succession also reach their greatest depth in the area west of Prees, the more northerly area of deep pre - Permian basement, south-east of Burford, is not well defined at higher stratigraphical levels."
"Indeed, at the base of the MMG it marks a local structural high."
"Depth-of-burial and backstripping studies indicate that the latter area marked the Permo - Triassic depocentre of the Cheshire Basin, but suffered significantly more uplift than surrounding areas during Cenozoic basin inversion."
Pre - Permian basement lies at depths in excess of 4000m in the hangingwall block of the King Street Fault.
"Permian strata, the SSG and the MMG all thicken across the bounding faults of the sub-basin, indicating that it developed as a structural feature throughout the extensional phase of basin evolution by contemporaneous normal displacement of these faults."
"West of these two important sub-basins, the Permo - Triassic basin fill is much thinner."
The western updip flank of the Wem ‚ $ `` Audlem Sub-basin‚ $ '' the Western Slope ‚ $ '' is characterised by a Permo - Triassic sequence which has a regional east-south-east dip and which thins gradually towards the more or less unfaulted western basin margin.
The westerly edge of this east-dipping tilt-block suffered sufficient relative uplift during the extensional phase of basin development for pre - Permian basement rocks to be exposed at surface at the present day.
"North of the Western Slope, an area of shallow pre - Permian basement, generally less than 1000m deep, has many small normal faults, throwing both down-east and down-west to create a complex system of tilt-blocks."
"In the north-west corner of the basin the Ellesmere Saddle has outcropping pre - Permian basement to the north-east and south-west, and connects the Cheshire Basin to the West Lancashire ‚ $ `` East Irish Sea Basin."
"East of the Ellesmere Saddle, the northern part of the Cheshire Basin is characterised by regional southerly dips, with Permo - Triassic strata dipping and thickening southwards into the Wem ‚ $ `` Audlem and Sandbach‚ $ `` Knutsford sub-basins."
"Stratigraphical thickening is particularly pronounced in the Permian succession, which is extremely condensed close to the northern edge of the basin."
The Permian succession is particularly condensed on the footwall block of the Brook House Fault the extensional phase of basin development.
"The Alderley High is characterised by relatively thin Permian and SSG sequences, the former thinning eastwards towards the basin margin."
"The MMG is absent or partially preserved, having been removed by later erosion."
"The Permian sequence is very thin or absent, suggesting that displacement on the WBRRFS was largely restricted to the Bridgemere Fault in Permian times, initiating the Wem ‚ $ `` Audlem Sub-basin in its hangingwall block, but leaving its footwall block largely subaerially exposed."
"By early Triassic times, displacement along the Wem Fault led to deposition of SSG on the Terrace, which nonetheless continued as a structural feature during subsequent extensional development, with SSG and MMG sequences markedly thinner than in the Wem ‚ $ `` Audlem Sub-basin to the west."
"It is similar to the Blakenhall Terrace, though somewhat larger, and is also characterised by a thin, locally absent, Permian sequence."
"It probably existed as an active structural feature throughout the extensional phase of basin development, with SSG and MMG sequences markedly thinner than in the Wem ‚ $ `` Audlem Sub-basin to the west."
The cumulative throw on the WBRRFS is greatest in its southern-central section where it locally exceeds 4000m at the base of the Permo - Triassic succession.
"However, because Carboniferous rocks outcrop on the footwall block of the Red Rock Fault, along much of its length, only minimum estimates of its TRUE throw can be made: the real throw may be much greater."
"Its throw, at the pre - Permian basement, is believed to be of the order of several hundred metres, decreasing markedly upwards."
"Thickening of the Permian sequence is particularly marked, indicating that the fault was an important structure early in basin evolution."
"Throws on the King Street Fault approach 1000m at pre - Permian basement level, but diminish north and south."
"Eastwards stratigraphical thickening occurs across the fault, particularly in the SSG, but in contrast to the Brook House Fault, thickening of the Permian sequence is minor."
"Easterly downthrows locally exceed 1000m, at the top of pre - Permian basement."
"There is only minor eastward thickening of preserved strata across the faults, suggesting that most of the displacement took place after deposition of the SSG."
"The fault downthrows to the west, locally almost 1000m where pre - Permian basement outcrops in the footwall block at the western edge of the Milton Green inlier."
"Seismic data suggest that the sub-cropping Carboniferous sequence is different on either side of the fault, and thus displacements pre-dated deposition of the Permian."
"Carboniferous rocks, comprising a Dinantian sequence overlain by Silesian."
"The Carboniferous succession is clearly imaged on seismic profiles beneath the northern and western parts of the basin, where it is locally more than 4000m thick."
"Elsewhere, the thickness of Carboniferous strata is constrained by the gravity interpretation."
Gravity stripping can not be wholly explained by the Permo - Triassic basin fill: considerable thicknesses of upper Carboniferous strata are also required.
2-D gravity modelling along basinwide traverses indicates upper Carboniferous.
Much of the lithostratigraphical information relating to the concealed Carboniferous sequence beneath the Cheshire Basin comes from boreholes and outcrops outside the basin.
"Dinantian rocks in the Cheshire Basin are proved only in the Milton Green, Blacon East, Ternhill, Stoke-on-Tern and Bowsey Wood boreholes, and the top Carboniferous Limestone reflector can not be traced very widely from Milton Green, so deductions about Dinantian rocks and structures are based largely on the surrounding outcrops."
In north-east Wales a north-north-west-striking outcrop of Dinantian rocks.
Both faults have thicker Dinantian successions on their northern blocks.
Subsequent dating of the sequence indicates that although late Asbian and Brigantian rocks thicken on the downthrown sides of the faults most of the displacement occurred early in the Dinantian.
Information from deep boreholes to the east indicates that the Milton Green Carboniferous inlier corresponds to a Dinantian structural high.
"On the outcrop to the west at Minera, Dinantian rocks are 260m thick."
"The borehole proved thick Pendleian to Brigantian rocks, with a thick Lower Bowland Shale equivalent."
"A seismic reflector, deeper than the borehole, dips towards the subsurface continuation of the Llanelidan Fault, suggesting thickening of the early Dinantian rocks in this sub-basin."
"Dinantian rocks in the Blacon East borehole total more than 400m, with the possibility of a further 600m beneath terminal depth."
In the south of the basin the WBRRFS throws Triassic strata against Westphalian rocks.
"Further north, near Astbury, Namurian and Dinantian rocks outcrop on the footwall block."
"A syn-sedimentary fault may form the eastern margin of the North Staffordshire Coalfield, between Astbury and Gun Hill, as envisaged for Namurian times."
"If, as seems likely, the Red Rock Fault acted as a Dinantian syn-sedimentary fault then Astbury stood on a structural high which was bounded by two differently trending Dinantian syn-sedimentary faults."
"Beneath the southern part of the Cheshire Basin, where Carboniferous reflectors are few, the Carboniferous structure can not be resolved directly."
Along the south-eastern margin of the basin large Permo - Triassic faults connect south-westwards to major Caledonian structures such as the Pontesford ‚ $ `` Linley structure.
"No Dinantian rocks were encountered in the Edgmond Borehole, whereas more than 200m are present at Stoke-on-Tern."
"Over 100m of Dinantian was proved in the Ternhill Borehole, close to the Hodnet Fault."
"The cross-section shows the Dinantian sequence thickening southwards to the limit of outcrop at Llanymynech, which may be related to syn-depositional movement on the Wem Fault."
"In the subsurface, seismic profiles show thickening of the Dinantian sequence southwards from Milton Green."
Dinantian rocks are overlapped by unconformable Westphalian D rocks beneath the south-western part of the basin.
"Deep seismic reflectors in this area, not proved by drilling, probably correspond to rocks in Dinantian basins, controlled by north-north-west-trending faults."
"The basin may link northwards to the Rainford Sub-Basin, where eastwards-thinning Dinantian may reach the Brook House Fault."
"Approximately 170m of Namurian rocks were intersected in the Milton Green Borehole on the Cyrn-y-Brain High, and more than 800m in the Blacon East Borehole in the Blacon Sub-basin: Namurian strata were also intersected in a few other boreholes."
The Aqueduct Grit is a distinctive low-gamma unit within the Namurian Series in the Milton Green Borehole.
"In the Talwrn Borehole, Namurian rocks may reach 230m in thickness: they probably thin northwards, in the Wrexham district, on to the Cyrn-y-Brain High."
"Namurian rocks have a narrower outcrop width south of the Aqueduct Fault, compared to its northern hangingwall block."
"In the Oswestry district, the outcrop width suggests that the Namurian rocks thin to the south."
"Towards the top of the Namurian succession the Aqueduct Grit has a feldspathic composition, consistent with the incursion of southward spreading Pennine deltas."
"In the extreme south-west of the basin, Namurian rocks are overlapped by unconformable Westphalian D strata, beneath Permian rocks."
East of the Red Rock Fault a basinal Namurian succession shows the relationship between the southern and northern clastic sources more clearly.
"Northward thinning of the southerly derived turbidites in the Macclesfield district may have caused starved sedimentation of Edale Shale type beneath this part of the Cheshire Basin, resulting in the deposition of potential hydrocarbon source rocks."
They are unconformable on Dinantian rocks across the feather edge of Namurian strata.
Namurian rocks are also absent from the Market Drayton High.
Westphalian strata are present beneath much of the Cheshire Basin.
Within the Westphalian succession the Symon Unconformity separates sequences thickening in opposite directions.
"Thus, beneath the unconformity, Productive Coal Measures, encompassing rocks of Westphalian A, B and part of C, thicken northwards to a depocentre near Manchester, with splitting of seams in a northerly direction."
"In contrast, red beds above the unconformity appear to thicken southwards, successively down-cutting Productive Coal Measures, Namurian and Dinantian strata to rest unconformably on Silurian and older rocks."
The Productive Coal Measures are about 450m thick in the boreholes and about 500m thick in the Denbighshire Coalfield.
"The Carboniferous outcrop terminates in the Oswestry district, west of Eardiston copper mine."
"The Symon Unconformity is represented here by overlap of the Productive Coal Measures, Namurian and Dinantian rocks by the Ruabon Marl and Coed-yr-Allt Formation."
"No Productive Coal Measures are known from the Shrewsbury Coalfield, where the red beds rest on Cambrian rocks."
The Leebotwood Coalfield also features red beds unconformable on late Precambrian Longmyndian rocks.
"In the Coalbrookdale Coalfield, Productive Coal Measures rest unconformably on Silurian rocks: the Dinantian rocks of the Little Wenlock area have been overlapped here."
"In the Madeley Coalfield, Productive Coal Measures are known in the north, but have been removed in the south by the Symon Unconformity."
The North Staffordshire Coalfield has thick Productive Coal Measures.
The northward thickening of the Productive Coal Measures reflects the Pennine depocentre near Manchester.
"The more complete sequence of Productive Coal Measures, compared with that of Madeley, suggests that the Symon Unconformity was formerly a south-dipping palaeoslope."
"The Knutsford Borehole reached the base of the Permo - Triassic sequence at 2821m, and penetrated a further 224m of coals and limestones of the Upper Coal Measures which are probably part of the Newcastle Formation, equivalent to the Coed-yr-Allt Formation to the west of the basin."
"If this correlation is correct, the Keele Formation, equivalent to the Erbistock Beds, must have been eroded prior to Permian deposition."
"Rocks of the Etruria Formation, equivalent to the Ruabon Marl, would be expected below terminal depth in the borehole, with Productive Coal Measures at greater depth."
"In the Lancashire Coalfield to the north and north-east of the Cheshire Basin, Productive Coal Measures are 1600m thick, thinning westwards."
"The basement rocks which underlie the Permo - Triassic and Carboniferous strata of the Cheshire Basin are thought to be principally of early Palaeozoic age: Lower Palaeozoic strata were intersected in the Milton Green Borehole and in the Prees Borehole, as well as beneath the Dinantian outcrop to the west in several shallow provings in the Halkyn‚ $ `` Minera mining district of north-east Wales."
"No Devonian rocks are known, but a borehole at Edgmond discovered Precambrian volcanic rocks beneath Coal Measures."
"These rocks, probably of Uriconian affinity, continue in the subsurface to Lilleshall, the Wrekin and south-east to Caer Caradoc."
"In the Wych and Byley mudstone formations and the upper part of the Bollin Mudstone Formation, evaporite beds can be identified on density logs and can thus be eliminated."
"Elsewhere in the MMG however, evaporites are mixed with mudstones as lamellae and nodules, and histograms of density values show bimodal distributions."
"At the Burford Borehole, where a porosity log is available for the SSG, the sandstones have porosities between 6 and 24%, which may produce an underestimate of the depth of burial."
"The cross-plots for the Lower Lias, Brooks Mill Mudstone, Bollin Mudstone, Malpas Sandstone, Helsby Sandstone, Wilmslow Sandstone and Kinnerton Sandstone formations at Prees and Burford showed clear linear trends, and best-fit lines were constructed to convert sonic-log values from other boreholes to density values, enabling the depth of burial to be estimated."
"The cross-plot for the Bollin Mudstone at Crewe did not show a linear trend, and density values estimated from it were much higher than those obtained from the Prees and Burford cross-plots."
"Cross-plots for the Wilkesley Halite, Northwich Halite, Wych and Byley Mudstone, Tarporley Siltstone and Collyhurst Sandstone formations showed too much scatter to enable reliable trend lines to be plotted."
The reliability of the estimated values for overburden thickness was tested by adding them to the observed depth to the base of the Bollin Mudstone Formation in each borehole and contouring the resulting data.
"The base of the SSG lay at depths locally greater than 5000m, the base of the MMG at depths locally greater than 3000m and the base of Jurassic strata at depths locally greater than 2000m."
"Regional tectonic considerations and apatite fission-track data suggest that the maximum depth of burial probably occurred about 60Ma ago in Palaeocene times, immediately prior to Cenozoic uplift, inversion and erosion."
"The ISM structure-contour grids for Base Jurassic, Base MMG, Base SSG and Base Permo - Triassic were thinned to a grid-node spacing of 1km to reduce the data volume to the limits required by the HotPot program."
"The total thickness of eroded overburden strata, and Permo - Triassic."
The Upper Cretaceous and Palaeocene component was assumed to have formed a uniform blanket 400m thick over the whole area.
The combined thickness of the Triassic and Jurassic components was thus calculated by subtracting 400m from the total-overburden grid.
"The fact that no Triassic strata were eroded where Jurassic rocks are still preserved and the assumption that preserved Jurassic strata would have been of negligible thickness towards the northern and western limits of the basin, were used to constrain the Permo - Triassic and Jurassic components of the eroded succession."
Preserved thicknesses of Permian strata are locally in excess of 1300m.
"Thicknesses decrease gradually north-west from this depocentre, so, at the end of Permian times, the Cheshire Basin had the overall form of a half graben."
"Preserved thicknesses of the SSG appear to define two depocentres in the southern and northern parts of the Wem ‚ $ `` Audlem Sub-basin, which locally have more than 2200m of strata."
At the end of SSG deposition the basin had a maximum depth in excess of 3500m.
The MMG is presently thickest in the Wem ‚ $ `` Audlem and Sandbach‚ $ `` Knutsford Sub-basins.
"In the latter, although the sequence is less complete, it is locally more than 1700m thick, suggesting that the area marked the original MMG depocentre."
"Separate depocentres, characteristic of the earlier basin evolution, were no longer so clearly defined, and it seems likely that there was a single depocentre for the MMG."
"End - Triassic depths can not be tightly constrained, because they incorporate a putative amount of eroded Permo - Triassic strata."
"Nevertheless, it is estimated that at the end of Triassic times the basin contained more than 5000m of strata."
"It is likely that Triassic strata spread considerably beyond the present-day boundaries of the basin, onto adjacent block areas."
Only small outliers of Jurassic strata are preserved.
"They lie in the central part of the Wem ‚ $ `` Audlem Sub-basin, to the south of the MMG depocentre, and it is thought unlikely that they correspond precisely to the Jurassic depocentre."
"Sedimentary thicknesses, but estimates are poorly constrained, incorporating a putative amount of Permo - Triassic, Jurassic and lower Cretaceous overburden."
"The tendency towards a single basin depocentre clearly continued in Jurassic times, as fault-controlled subsidence gradually diminished and post-extensional regional subsidence prevailed."
"Sedimentary thicknesses in early Palaeocene times, incorporating the total estimated thickness of eroded strata, locally approached 6500m, and marked the maximum development of the basin, immediately prior to uplift and erosion."
Very rapid early Triassic subsidence marked the main phase of basin development.
"This was followed by more gradual subsidence in Jurassic and Cretaceous times, followed in turn by Cenozoic uplift."
"The large down-west normal faults of the WBRRFS lie in the hangingwall blocks of Variscan reverse faults, the base of the Permo - Triassic succession being progressively faulted down to the west."
"This was a consequence of extensional reactivation of the basement reverse faults in Permo - Triassic times which led to collapse of their hangingwall blocks by upward propagation of steeper normal faults, to form the basin margin."
"On a more regional scale, the Permo - Triassic rift system of southern Britain can be divided structurally into three segments which reflect the structural grain of the underlying basement."
This is interpreted as indicative of a cumulative Permo - Triassic extension vector oriented roughly west-south-west.
"The dominant fault strike is not parallel to the main Caledonoid trend, and may reflect a reactivated Carboniferous structural trend: a strong north-north-westerly trend is evident in the Carboniferous rocks of the Rossendale area to the north, visible on the aeromagnetic data."
"Results are generally in good agreement with the regional Permo - Triassic extension direction in southern Britain, estimated by Chadwick and Evans using different structural criteria at 075‚ $ `` 255¬ ∞."
"Regional tectonic considerations indicate that roughly east‚ $ `` west extension was probably dominant throughout the Permo - Triassic and early Jurassic, the period which encompassed most of the extensional faulting."
"The cumulative heaves on transects AA to JJ are marked with an asterisk signifying that they are minimum values, because on these transects the eastern basin margin includes faults with pre - Permian basement rocks at outcrop in the footwall blocks."
The TRUE heaves of these faults at the base of the Permo - Triassic can not be seen: observed heaves are therefore minimum estimates.
Because of the progressively smaller outcrop areas of horizons above the base of the Permo - Triassic it is not possible to use all of the 15 extension-parallel transects.
"Heaves were measured for all the faults on DD * ‚ $ `` LL * at Base Permo - Triassic, Base SSG and Base MMG."
"On each transect, observed heaves for Base Permo - Triassic are greater than those for Base SSG, which in turn are greater than those for Base MMG."
The cumulative profile indicates that measured heaves at Base MMG and Base SSG are typically 56% and 80% of the total observed heaves.
"The large down-west normal faults of the WBRRFS lie in the hangingwall blocks of Variscan reverse faults, the base of the Permo - Triassic succession being progressively faulted down to the west."
"This was a consequence of extensional reactivation of the basement reverse faults in Permo - Triassic times which led to collapse of their hangingwall blocks by upward propagation of steeper normal faults, to form the basin margin."
"On a more regional scale, the Permo - Triassic rift system of southern Britain can be divided structurally into three segments which reflect the structural grain of the underlying basement."
This is interpreted as indicative of a cumulative Permo - Triassic extension vector oriented roughly west-south-west.
"The dominant fault strike is not parallel to the main Caledonoid trend, and may reflect a reactivated Carboniferous structural trend: a strong north-north-westerly trend is evident in the Carboniferous rocks of the Rossendale area to the north, visible on the aeromagnetic data."
"Results are generally in good agreement with the regional Permo - Triassic extension direction in southern Britain, estimated by Chadwick and Evans using different structural criteria at 075‚ $ `` 255¬ ∞."
"Regional tectonic considerations indicate that roughly east‚ $ `` west extension was probably dominant throughout the Permo - Triassic and early Jurassic, the period which encompassed most of the extensional faulting."
"The cumulative heaves on transects AA to JJ are marked with an asterisk signifying that they are minimum values, because on these transects the eastern basin margin includes faults with pre - Permian basement rocks at outcrop in the footwall blocks."
The TRUE heaves of these faults at the base of the Permo - Triassic can not be seen: observed heaves are therefore minimum estimates.
Because of the progressively smaller outcrop areas of horizons above the base of the Permo - Triassic it is not possible to use all of the 15 extension-parallel transects.
"Heaves were measured for all the faults on DD * ‚ $ `` LL * at Base Permo - Triassic, Base SSG and Base MMG."
"On each transect, observed heaves for Base Permo - Triassic are greater than those for Base SSG, which in turn are greater than those for Base MMG."
The cumulative profile indicates that measured heaves at Base MMG and Base SSG are typically 56% and 80% of the total observed heaves.
Because of the progressively smaller outcrop areas of horizons above the base of the Permo - Triassic it is not possible to use all of the 15 extension-parallel transects.
"Heaves were measured for all the faults on DD * ‚ $ `` LL * at Base Permo - Triassic, Base SSG and Base MMG."
"On each transect, observed heaves for Base Permo - Triassic are greater than those for Base SSG, which in turn are greater than those for Base MMG."
The cumulative profile indicates that measured heaves at Base MMG and Base SSG are typically 56% and 80% of the total observed heaves.
"Present-day temperature maps for the bases of the Jurassic, MMG, SSG and Permian, computed using the mean present-day heat flow of 52mWm‚ $ `` 2, indicate that the basin is quite cool, with mean temperatures ranging from 20¬ ∞ C at the base of the MMG to 37¬ ∞ C at the base of the Permo - Triassic."
The highest temperatures at the base of the Permo - Triassic in the deeper parts of the basin locally exceed 70¬ ∞ C in parts of the Wem ‚ $ `` Audlem Sub-basin and 65¬ ∞ C in the Sandbach‚ $ `` Knutsford Sub-basin.
Calculated temperatures near the Alderley Edge mineralisation range from 25¬ ∞ C at the base of the SSG to 33¬ ∞ C at the base of the Permo - Triassic.
"Decreasing the heat flow to 40mWm‚ $ `` 2 depressed mean basin subsurface temperatures by about 3¬ ∞ C at the base of the MMG, and 6¬ ∞ C at the base of the Permo - Triassic."
Increasing the heat flow to 64mWm‚ $ `` 2 raised the mean temperatures by about 2¬ ∞ C at the base of the MMG and 7¬ ∞ C at the base of the Permo - Triassic.
"The extension that led to this cumulative extension factor was distributed over a long period of time, from latest Permian times to the early Cretaceous."
"For the purposes of this study a single, instantaneous pulse of extension occurring at the beginning of the Triassic is assumed."
"Curry gives a value of 20¬ ∞ C for the early Palaeocene, corresponding to the maximum depth of burial in the region."
"In the Wem ‚ $ `` Audlem Sub-basin, peak temperatures reached c. 90¬ ∞ C locally at the base of the Jurassic sequence, c. 105¬ ∞ C at the base of the MMG, c. 130¬ ∞ C at the base of the SSG and c. 140¬ ∞ C at the base of the Permo - Triassic."
"Corresponding values in the Sandbach‚ $ `` Knutsford Sub-basin were Base MMG c. 95¬ ∞ C, Base SSG c. 120¬ ∞ C and Base Permo - Triassic c. 135¬ ∞ C. The Alderley Edge area was, at this time, assumed to be buried under nearly 1500m of Chalk, Jurassic and upper Triassic strata."
"The computed temperatures at the base of this overburden were c. 65¬ ∞ C, at the base of the SSG c. 80¬ ∞ C, and at the base of the Permo - Triassic 90¬ ∞ C. Mapped subsurface temperatures 97Ma ago, corresponding to the end of late Cimmerian erosion, immediately prior to the onset of post-extension subsidence in the late Cretaceous, are given in Chadwick et al.."
Mean temperatures ranged from c. 75¬ ∞ C at the base of the MMG to c. 90¬ ∞ C at the base of the Permo - Triassic.
"By this time the basin had a single depocentre, to the north-east of the present deepest part of the Wem ‚ $ `` Audlem Sub-basin, in which temperatures attained almost c. 100¬ ∞ C at the base of the MMG, c. 125¬ ∞ C at the base of the SSG and c. 140¬ ∞ C at the base of the Permo - Triassic."
The Alderley Edge area was at this time buried beneath about 1100m of upper Triassic and Jurassic strata.
"Temperatures at the top and base of the preserved SSG at were c. 55¬ ∞ C and c. 75¬ ∞ C, and 85¬ ∞ C at the base of the Permo - Triassic."
"Mapped subsurface temperatures 205Ma ago, at the end of the Triassic, are given in Chadwick et al.."
"The mean temperatures in the basin were c. 40¬ ∞ C at the base of the MMG, c. 60¬ ∞ C at the base of the SSG and c. 70¬ ∞ C at the base of the Permo - Triassic."
Peak temperatures of c. 60¬ ∞ C at the base of the MMG: c. 90¬ ∞ C at the base of the SSG and > 100¬ ∞ C at the base of the Permo - Triassic were reached locally in the Sandbach‚ $ `` Knutsford Sub-basin.
"In the Alderley Edge area, temperatures were c. 60¬ ∞ C at the base of the SSG and c. 70¬ ∞ C at the base of the Permo - Triassic."
Computed pseudo-maturity maps of the bases of selected Permo - Triassic layers from the end of the Triassic to the early Palaeogene are given in Chadwick et al..
"In summary, the deepest parts of the Permian sequence entered the oil window towards the end of the Triassic and left it during Cenozoic uplift."
A large proportion of the Permian deposits were in the oil window at the time of maximum burial and some parts were at temperatures almost high enough for gas generation.
The deepest parts of the SSG were in the oil window from early Jurassic to mid or late Palaeogene times.
The deepest parts of the MMG were perhaps only briefly in the oil window from late Cretaceous to early Palaeogene times.
"Upper Carboniferous strata underlying the basin would have entered the oil window earlier than the Permo - Triassic strata, probably in mid to late Triassic times, and remained in the oil generation zone for longer, probably until the early Neogene."
"They would also have attained higher levels of maturity, well into the gas-generation zone at the time of maximum burial in the early Palaeocene."
"The last major deformation episode, in early Devonian times, corresponded to the late Caledonian orogeny and resulted in major transpressive faulting, uplift and regional erosion."
Carboniferous strata were deposited unconformably on the Caledonian erosion surface.
"Initially, Dinantian rocks were deposited in fault-bounded extensional basins which, at least in part, were controlled by the reactivation of older, basement, structures."
Later Carboniferous deposition appears to have been of a more regional nature.
"Carboniferous rocks underlie most of the Cheshire Basin, being thickest in the north where more than 4000m of strata are preserved, with about 2000m of Upper Carboniferous beds."
"At the end of Carboniferous times Variscan compressive stresses led to major transpressional fault reactivation, basin inversion, and regional erosion."
"The Cheshire Basin is filled largely with Permo - Triassic strata, which rest unconformably on Carboniferous rocks and, locally, in the south, on Caledonian basement."
"It is markedly asymmetrical in cross-section, having, in general terms, the form of a faulted half graben, deepest in the south-east, where the base of the Permo - Triassic succession lies at depths locally in excess of 4500m."
The Permo - Triassic and subsequent evolution of the Cheshire Basin can be summarised as follows: The initial measurable phase of basin subsidence corresponded to deposition of the Permian sequence.
Early Triassic subsidence was associated with the deposition of much of the SSG.
"The upper SSG, the MMG and the Penarth Group were deposited during Middle and Upper Triassic subsidence."
"Rates of subsidence decreased gradually with time, and a single depocentre developed, where, by the end of the Triassic, sedimentary thicknesses probably exceeded 5000 m. Preserved Jurassic strata are restricted to outliers of limited extent, so the Jurassic phase of basin evolution is poorly constrained."
"Regional considerations suggest that east‚ $ `` west extension probably continued into early Jurassic times, with continued fault-controlled basin subsidence."
"It is likely that the preserved Jurassic strata lie somewhat to the south of the Jurassic depocentre, which probably overlay the late Triassic depocentre."
"Extension probably recommenced in late Jurassic times, possibly with a markedly different extension direction Total sedimentary thicknesses at the end of this period may have exceeded 6000m locally, with the deepest parts of the Permian succession probably entering the oil window."
"Regional considerations suggest that crustal extension continued into early Cretaceous times, but contemporaneous regional uplift caused severe erosion of the basin margins, with lesser erosion of the basin depocentre."
"It is likely that crustal extension ceased in early Cretaceous times, extension in the period from 242Ma to 97Ma constituting perhaps 48% of the total post-Variscan extension."
The deepest parts of the SSG and the Permian succession probably entered the oil window during this period.
"Maximum basin development was probably attained in early Palaeocene times, with the accumulation of nearly 6500m of strata in the basin depocentre."
"Peak subsurface temperatures were attained at this time, with the deepest parts of the MMG and all underlying strata within the oil window."
"Regional uplift commenced in Palaeocene times, perhaps associated with development of the Iceland Plume."
"Inversion probably culminated in the Oligo - Miocene, associated with Alpine compressional events to the south."
"Several approaches have been used here to shed light on the provenance of the Permo - Triassic fill of the Cheshire Basin, including studies of heavy-mineral assemblages, heavy-mineral chemistry, clay mineralogy, whole-rock petrography, whole-rock geochemistry and radiogenic isotopes."
"However, most of the boreholes sampled were relatively shallow and may, therefore, have been affected by Tertiary and modern weathering and shallow groundwater flow."
"In all, 92 samples were analysed by X-ray diffraction analysis to determine their clay mineralogy: 54 from the MMG, 35 from the SSG and 3 from the Manchester Marls Formation."
The Kinnerton Sandstone Formation was examined in boreholes from both the northern and southern parts of the Cheshire Basin.
"The SSG examined in the Perry Farm and Little Ness boreholes may include this formation, but the stratigraphy of these boreholes is very poorly constrained."
The Kinnerton Sandstone Formation is composed of pebble-free sandstones.
Sandstone rock fragments were found in the Kinnerton Sandstone Formation from the Rainhill Borehole.
"This type of monazite has been found in Palaeozoic rocks from the Welsh Massif, south-west England, Belgium and Brittany, as well as in rocks ranging from Precambrian to Permian in age further afield in Europe and other parts of the world."
"Observations on the Chester Pebble Beds Formation are biased towards the north-west and south-east of the basin, and there is little apparent difference between these areas."
"The mineralogy of the Chester Pebble Beds is very similar to that of the the underlying Kinnerton Sandstone, although the sandstones generally contain a greater proportion of lithic clasts, chert and K-feldspar."
"Lithic fragments are dominated by chert and quartzite, with subordinate silicified volcanic clasts and silicified bioclastic rock fragments, the latter probably derived from the Carboniferous."
"Samples from the north of the basin were found to contain an assemblage of illite, smectite and chlorite, similar to the underlying Kinnerton Sandstone Formation, although locally it appears that the Chester Pebble Beds are more chloritic."
"The Wilmslow Sandstone Formation was examined in a wide coverage of boreholes from the north and south of the basin, and also at outcrop at Grinshill."
"Albite appears, qualitatively, to be more abundant in the Wilmslow Sandstone Formation than in the other SSG formations."
"Fragments of volcanic rock, including silicified rhyolitic and highly altered ferruginous varieties, are probably less significant than in the Kinnerton Sandstone and Chester Pebble Beds."
The Helsby Sandstone Formation was studied largely in the north and north-west of the basin.
"The Bulkeley Hill Sandstone Formation, which lies between the Wilmslow Sandstone Formation and the Helsby Sandstone Formation, was not examined in this study."
"This sandstone was not, however, fully penetrated in the Wilkesley Borehole and may here represent the top of the Helsby Sandstone Formation."
The petrological and sedimentological characteristics of the Malpas Sandstone are so similar to those of the Helsby Sandstone Formation that they are considered together in this section.
"The Helsby Sandstone Formation is dominated by quartz arenites interbedded with subordinate quartz and cherty sublitharenites and subarkosic sandstones, and occasional quartz wackes, quartz-rich ferruginous siltstones and silty mudstones."
"Interlaminated siltstones and mudflake breccias are common in the upper parts of the sequence, for example in the Saughall Massie Borehole, as it passes into the Tarporley Siltstone Formation."
"In general, however, quartz arenites dominate the Helsby Sandstone Formation and the sandstones are more feldspathic."
"However, in the Malpas Sandstone of the Wilkesley Borehole, well-rounded, low-grade."
In the west the Helsby Sandstone Formation lacks chlorite.
"The Tarporley Siltstone Formation has a distinctive facies of alternating siltstone, reddish brown and greenish grey mudstone and thin, fine - to medium-grained sandstones."
The Tarporley Siltstone Formation in the Marston Salt Union Borehole locally contains occasional thin laminae of aphanitic lath-like synsedimentary anhydrite.
Coarser sandstones and siltstones in the Tarporley Siltstone Formation are similar to those of the underlying Helsby Sandstone Formation.
XRD studies of the Tarporley Siltstone Formation from the Wood Lane Borehole indicate that the < 2µm fraction clay minerals are dominated by illite with a variable proportion of smectite and chlorite.
"It is commonly found in many modern-day hypersaline evaporitic lacustrine and associated syndepositional diagenetic environments, and its occurrence is consistent with the inferred depositional environment of the Bollin Mudstone Formation."
The whole-rock petrography of the Northwich Halite Formation was examined only in samples from the Meadowbank Salt Mine.
Interbedded mudstones and siltstones are very similar to the laminated anhydritic - dolomicritic siltstones found in the underlying Bollin Mudstone Formation and the overlying Byley Mudstone Formation.
"The Byley Mudstone Formation comprises red and green interlaminated siltstones and mudstones, which are often very dolomitic and anhydritic, together with a structureless mudrock facies."
"As in the Bollin Mudstone Formation, the BSEM reveals very fine-scale cross-lamination in these anhydritic - dolomitic sediments, indicating deposition under a gentle current regime."
"In general, the Byley Mudstone Formation is similar to the Bollin Mudstone Formation and also represents deposition in a shallow hypersaline environment, periodically drying out with localised marginal sabkha development."
"The Wych Mudstone Formation, as typified by the sequence in the Crewe Heat Flow Borehole, is represented by dominantly structureless reddish brown siltstones, silty mudstones and mudstones, with occasional thin very fine quartz arenites."
"As in the underlying Byley Mudstone Formation, the clay mineralogy of the Wych Mudstone Formation consists of a uniform assemblage of illite, corrensite and minor chlorite."
No petrographic analysis was undertaken for the Wilkesley Halite Formation.
"XRD analysis of two samples from the Arclid Bridge 2 Borehole identify a clay-mineral assemblage of illite, corrensite and minor chlorite similar to that in the underlying MMG formations."
Petrographic analysis of the Brooks Mill Mudstone is limited to the British Gypsum Audlem AU17 Borehole.
"XRD analysis of 13 samples of Brooks Mill Mudstone Formation from the Audlem AU17 and Lotus Ltd, Stafford boreholes show either an assemblage of illite and chlorite, or illite, corrensite and chlorite."
"However, maximum temperatures and burial depths for the SSG can not be inferred directly from the experimental work of Hansley or the North Sea analogy, because dissolution rates also depend on pore-water chemistry, fluid flux and heat flow."
The relatively advanced garnet dissolution observed in the SSG of the Cheshire Basin therefore implies either a combination of the above.
Thirty sandstone samples from formations underlying the Chester Pebble Beds Formation were included in the study.
Most are from sandstones assigned to the Kinnerton Sandstone Formation.
"One sample of Bold Formation, two of Collyhurst Sandstone Formation and two of arenaceous units near the top of the Manchester Marls Formation were also included."
"As data from the Bold, Collyhurst Sandstone and Manchester Marls formations fall within the ranges shown by the Kinnerton Sandstone."
"The Kinnerton Sandstone in the Stanlow Borehole shows stratigraphical variations that may provide a basis for correlation, at least on a local level."
Tourmaline compositions were determined for eight samples from below the Chester Pebble Beds.
"Type 2 occurs in Kinnerton sandstones of the Newport UDC and Childs Ercall boreholes, whereas Type 1 occurs in Collyhurst, Bold and Kinnerton sandstones of the Stanlow, Speke Reservoir and Childs Ercall boreholes."
Thirty-two sandstone samples from the Chester Pebble Beds were analysed from eight boreholes in the Cheshire Basin and from the equivalent Cannock Chase Formation.
There is some doubt as to whether the succession in the Perry Farm Borehole is Chester Pebble Beds or Kinnerton Sandstone: the heavy-mineral ratios are more characteristic of the former.
"Excluding two samples from the base of the Chester Pebble Beds Formation in the Speke Reservoir Borehole, ATi values are high with relatively little scatter."
Tourmalines were analysed from six Chester Pebble Beds sandstones.
"The anomalous sample has lower FeO and higher MgO, and is more comparable to samples from the overlying Wilmslow Sandstone Formation."
"The boundary between the Wilmslow Sandstone Formation and the Chester Pebble Beds Formation has been placed at 135m in the borehole, some 8m above the anomalous sample."
This indicates either that the position of the boundary requires revision or that Wilmslow - type sources had become of major importance during late Chester Pebble Beds times.
Twenty-nine samples from the Wilmslow Sandstone Formation were studied from five boreholes.
"The geological map suggests that the borehole should start in Helsby Sandstone, but the geochemistry and the borehole log suggest that the Wilmslow Sandstone is represented, at least in the deeper parts of the hole."
The heavy-mineral characteristics are very clearly of Wilmslow Sandstone affinity.
The tourmaline compositions of apatite-poor and apatite-rich sandstones from the Wilmslow Sandstone Formation are very similar.
The tourmaline data show a close affinity with the overlying Helsby Sandstone.
"It is more likely that the apatite-poor assemblage was formed from the apatite-rich assemblage through apatite dissolution, as a result of an intra - Triassic, or a much more recent, event."
"On the other hand, the stratigraphical position of the apatite-poor assemblage, which appears to be in the upper part of the Wilmslow Sandstone beneath the Hardegsen disconformity, suggests that the action of acidic groundwater during an intra - Triassic event is the most likely cause."
The provenance of the Wilmslow Sandstone differs significantly from that of the Chester Pebble Beds.
"Monazite is less abundant, with a mean MZi close to 1 compared with 4 for the Chester Pebble Beds, and there are fewer FeO-rich and more MgO-rich tourmaline grains."
"Therefore, although the source of the Chester Pebble Beds is likely to have continued to contribute to the basin fill, generating the relatively high MZi values seen in some Wilmslow Sandstone samples, the source of much of the material appears to have greater affinities with that supplying the Kinnerton, Collyhurst and Bold sandstones."
Eleven samples from the Helsby Sandstone were examined.
"As noted in the previous section, the Helsby Sandstone may also be represented at the top of the Bootle Borehole."
"Apart from the greater abundance of garnet in Coton Fields, the Helsby Sandstone Formation has generally uniform characteristics."
"Overall, these parameters are very similar to those associated with the apatite-rich Wilmslow Sandstone."
"This suggests that the provenance of the fluvial sandstones has some affinity with that of the Chester Pebble Beds Formation, and that this influence is absent in the aeolian facies."
"Three tourmaline populations were studied from the Helsby Sandstone, two from the Thornton Borehole and one from the Wood Lane Borehole."
"Their characteristics are similar to those from the Wilmslow Sandstone Formation, although they tend towards higher FeO and MgO values."
"This supports the evidence from the conventional heavy-mineral data, that the provenance of the Helsby Sandstone Formation is similar to that of the Wilmslow, but with some influence from Chester Pebble Beds sources."
"The samples from the Helsby Sandstone Formation are characterised by a greater abundance of secondary minerals, notable carbonate and pyrite, than in the underlying sandstones."
"This may be because the Helsby Sandstone Formation underlies the impermeable MMG, which probably acted as a source and caprock to mineralising fluids."
The Nd-isotope signatures of whole rocks and pebbles from the basin fill were examined in order to obtain information about the rocks which were weathered and eroded to produce the detritus deposited in the Cheshire Basin during Permian and Triassic times.
"In contrast, the isotope signature of an individual clast from the Chester Pebble Beds Formation will reflect that of a specific source."
Samples from the SSG were selected on the basis of the results of the first stage of heavy-mineral investigations.
"A typical sample was selected from each of the four sandstone formations and, in addition, samples with unusual heavy-mineral contents from the Kinnerton Sandstone, Wilmslow Sandstone, and Helsby Sandstone formations were analysed, as these were considered more likely to have a secondary source component."
"Five samples were collected from the MMG, covering the range of colour and grain size: they included examples of both structureless and laminated facies, ranging from red-brown to grey-green to light grey in colour."
One sample of fine sandstone and siltstone was taken from the basal Tarporley Siltstone Formation and four comprising siltstones and mudstones from lithologies higher in the sequence.
"In addition, one sample of dark grey mudstone was collected from the Carboniferous basement beneath the basin to provide a comparison with the Permo - Triassic basin fill."
"Clasts from the Chester Pebble Beds Formation in the Cheshire Basin were analysed, and comparative data were obtained for similar conglomeratic units deposited in the more southerly."
"Pebbles were selected from the Chester Pebble Beds at two outcrop localities in the north-west of the basin, within the same area as the whole-rock samples."
The age chosen lies approximately at the SSG ‚ $ `` MMG boundary.
"There are many bordering and distal massifs which were available to contribute detritus into the basin during the Triassic, including: the Welsh Massif: the Lake District, the Southern Uplands and Highlands Massifs: the Anglo-Brabant Massif: the Cornubian Massif: and more distal sources under or beyond the English Channel, such as the Armorican Massif."
"The Cornubian Massif, another potential source, would have been shedding Permian mudstone as well as material from the Hercynian granites."
"Armorican faunas have been reported from the Budleigh Salterton Pebble Bed exposed on the south coast of England, which may occur at a similar stratigraphical level to the Chester Pebble Beds."
"More than 580 samples were collected for chemical analysis, including more than 300 from the SSG and over 200 from the MMG."
"Helsby, etc.."
"A few of the samples from the Wilkesley Halite, which consisted largely of halite with minor mudstone, were placed in water to remove the salt, and the residue was processed in the same way as the whole-rock samples."
Approximately 50 samples from the SSG and the Tarporley Siltstone Formation were analysed for REE by ICP-MS.
"The analysis was undertaken on the SSG and MMG as a whole, and on the individual component formations."
The Helsby Sandstone data were run once with all samples included and again with mineralised samples from West Mine and Clive Mine omitted.
"Factor analysis of the SSG as a whole reveals aluminosilicate, mineralisation and carbonate factors."
"This factor could also include secondary iron oxides, which are more abundant in the clay-rich rocks of the SSG."
"In addition, Ni and Cr correlate with Al2O3 in all formations except the Helsby Sandstone."
"Ba, Sr, Th, V and Zn also correlate with Al2O3 in the Chester Pebble Beds and Sr, Th, V and Zn in the Wilmslow Sandstone."
"MgO is present in this factor for the Helsby Sandstone, suggesting that in this formation dolomite is the most important MgO mineral."
"This is supported by petrographical observations, particularly of eodiagenetic nodular dolomite, in the Helsby sandstone."
"The second factor for the Kinnerton Sandstone includes Fe2O3, Co, Ni and V, suggesting an iron-oxide or sulphide association."
"The Chester Pebble Beds and Wilmslow Sandstone have a probable heavy-mineral factor, dominated by Zr, with a less significant score for Th in the Chester Pebble Beds and P2O5 in the Wilmslow Sandstone."
Baryte emerges as a probable minor factor in all but the Kinnerton Sandstone.
"Taken as a whole, the MMG does not show a very coherent result from factor analysis, probably because many elements are present in more than one mineral."
"When individual formations of the MMG are considered the dominant factor is, as in the SSG, an aluminosilicate one which includes Al2O3, TiO2, K2O, Ce, Cr, La, Nb and Rb in all formations."
"However, unlike the SSG, Fe2O3, P2O5 and Ni are always present, but Th and Y do not always appear."
"Minor factors include: Tarporley Siltstones: As, Co, Pb Bollin Mudstones: As, Co, Ni -LRB- ? sulphides -RRB- Northwich Halite: Zr Byley Mudstones: Ti, P, Ba, Ce, La, Nb, Y, Zr Wych Mudstones: La, Y, Zr."
"The Kinnerton and Wilmslow sandstones display less variability than the Chester Pebble Beds and the Helsby Sandstone, and the interquartile range for most elements is usually narrower."
"Samples taken from the Kinnerton and Wilmslow sandstones are dominantly of aeolian facies, whereas the Pebble Beds are mainly fluvial and the Helsby samples include a significant number from fluvial facies."
The Chester Pebble Beds and the Kinnerton Sandstone have higher Fe2O3/Al2O3 but lower Zr/Al2O3 than the other formations.
The Helsby and Kinnerton sandstones have lower K2O levels than the other SSG formations.
The Kinnerton Sandstone differs in many respects from most or all of the other units.
"Helsby and Grinshill sandstones, higher Fe2O3 than the Wilmslow Sandstone and later units and low Al2O3, TiO2, P2O5, Th, Y except compared to Helsby, ? Helsby and Grinshill sandstones."
"Concentrations of Na2O, Ba, Sr, Rb, As, Pb are low except compared to the Grinshill Sandstone, K2O levels low except compared to the Helsby and Grinshill sandstones and Zr low except compared to the Chester Pebble Beds and Helsby Sandstone."
"The Fe2O3/Al2O3 ratio is higher than in all the other units, Ce/Al2O3 is higher than in all formations except the Grinshill Sandstone, and Ni/Al2O3 is high except compared to the Helsby and Grinshill sandstones."
The Kinnerton Sandstone has low Rb/Al2O3 except in comparison to the Grinshill Sandstone.
"The Kinnerton Sandstone is predominantly an aeolian unit, deposited early in the basin‚ $ ô s history, prior to the first major influx of fluvial sediments represented by the Chester Pebble Beds."
"All units deposited subsequent to the Chester Pebble Beds, as well as that unit itself, have some geochemical signature related to the fluvial material from the south."
"It is interesting to compare the Kinnerton and Wilmslow sandstones, as both are predominantly aeolian, particularly in the boreholes sampled."
"Both sandstones generally have higher SiO2 than other units, but the Kinnerton Sandstone has higher values than the Wilmslow Sandstone."
"The Wilmslow Sandstone has higher Al2O3, Na2O, TiO2, K2O, MgO, P2O5, Sr, Ba, Rb, Th, Zr, Y, Ce, La, Cu, As, and Pb."
"As was noted on p. 90, the Kinnerton Sandstone is dominated by cherty sublitharenites, thus explaining the high SiO2 content, whilst the Wilmslow Sandstone is more argillaceous and, therefore, richer in Al2O3 and related elements."
"The Wilmslow Sandstone has higher Na2O/Al2O3, K2O/Al2O3, Rb/Al2O3, Ba/Al2O3, Sr/Al2O3, Zr/Al2O3, and Th/Al2O3."
"The Wilmslow Sandstone Formation includes arkosic and subarkosic rocks, which were not seen in the Kinnerton Sandstone."
"However, as was noted earlier, there are diagenetic monazites present in the SSG, as well as those from igneous sources: Cornubia or Armorica could be the source of these, but they could equally be supplied from other areas of Palaeozoic rocks in Wales or the Midlands."
"In contrast, the Kinnerton Sandstone has higher Fe2O3, CaO, LOI, Zn, Fe2O3/Al2O3, Ce/Al2O3, Ni/Al2O3 and V/Al2O3."
"The higher Ni/Al2O3 could indicate a more basic igneous input, possibly from Carboniferous volcanics, although volcanic clasts observed in the formation appear to be of acid or felsic composition."
"There is no significant difference in MnO content between the two sandstones, but the levels are low in both compared with those of the Chester Pebble Beds and the Helsby Sandstone."
"It is difficult to test geographical variations within formations rigorously because of the uneven distribution of samples, but some differences can be seen for the Kinnerton and Wilmslow sandstones."
"For example, K2O/Al2O3 values for the Kinnerton and Wilmslow sandstone are higher in the south of the basin than in the northern half."
"In the Kinnerton Sandstone this ratio is significantly higher in the south than the north, which may be related to the greater variety of lithic clasts seen in the south."
"The Wilmslow Sandstone, in contrast, has lower Ni/Al2O3 in the south."
"The Wilmslow Sandstone data may thus be interpreted in terms of a decline in coarser-grained fluvial detritus northward, as evidenced by the decrease in pebble content of the Chester Pebble Beds in this direction, with an associated decrease in feldspar and increase in clay-mineral contents."
The differences in the Kinnerton Sandstone suggest variations in source area.
REE analysis was carried out on selected samples from the SSG and the Tarporley Siltstone Formation to assess whether the patterns would provide any useful information on provenance.
"In conclusion, there appears to be a mineralogical control on the REE in the SSG and the Tarporley Siltstone."
"These show a marked difference between the Kinnerton Sandstone and other units, consistent with its rather different general geochemistry."
"This may be related to the fact that the Kinnerton Sandstone is mainly of aeolian facies, deposited before the first major fluvial influx of sediment into the basin represented by the Chester Pebble Beds."
"Later aeolian facies were probably, at least in part, reworking exotic material introduced from the south by rivers, while fluvial facies of the Wilmslow and Helsby sandstones are known to have this southerly derivation."
"Bollin Mudstones -RRB-, LOI, CaO, MgO and Sr.."
"This is borne out by petrographic study which shows a high siliciclastic component, very similar to that of the underlying SSG."
"The Byley Mudstones are generally distinct from the other units, but most similar to the Wych Mudstones and ? Bollin Mudstones."
"Bollin Mudstones -RRB-, TiO2 -LRB- except for the ? Bollin Mudstones and the Wilkesley Halite -RRB- and Zr."
"Anhydritic and dolomitic rocks are well developed in the Byley Mudstones and, to a lesser extent, in the upper Bollin and Wych mudstones."
"Bollin Mudstones, seem to be geochemically most similar to the Byley Mudstones of the Cheshire Basin."
For some elements the lower part of the MMG.
"The common pattern of these elements is for similar, and relatively high levels in the Tarporley Siltstones, Bollin Mudstones and Northwich Halite, a marked fall in the Byley Mudstones, and then a consistent rise in median concentrations up to the Brooks Mill Mudstones."
"The petrography of the Tarporley Siltstone and Brooks Mill Mudstone is similar, with both formations containing a significant arenaceous siliciclastic component."
Bollin Mudstones.
"Values are also generally high in the Bollin and Brooks Mill Mudstones, and in the Stafford Halite."
"The Bollin Mudstones, ? Bollin Mudstones and Northwich Halite have higher TiO2/Al2O3."
The Tarporley Siltstones and Bollin Mudstones have lower Sr/Al2O3.
Bollin Mudstones and the Stafford Halite have low Fe2O3/Al2O3 compared with all except the Tarporley Siltstones.
"The Wych and Byley mudstones have low Y/Al2O3, Ce/Al2O3, Zr/Al2O3, La/Al2O3 and Rb/Al2O3 and high Cr/Al2O3, Ni/Al2O3 compared with most other units."
The gross differences between formations were also examined by comparing geochemical profiles in the Wilkesley Borehole: samples show higher Cr/Al2O3 and Ni/Al2O3 and lower Zr/Al2O3 in the Wych and Byley mudstones than in any of the other formations.
"Geographical variation is also apparent within the Byley and Wych mudstones, as the Cr/Al2O3 and Ni/Al2O3 ratios are higher and the Zr/Al2O3 ratio lower, in the Crewe, Wilkesley and Lower Wych boreholes than in other boreholes."
"As a contrast to the above relationships, there is a positive correlation between Zr/Al2O3 and Cr/Al2O3 in the lower part of the Wilkesley Halite of Wilkesley Borehole."
Two broad facies types can be recognised in the MMG:.
Both facies are present in the Byley Mudstones of the Crewe Borehole.
The Saughall Massie Borehole shows a contrast between the Tarporley Siltstones and the underlying Helsby Sandstone.
"In the Helsby Sandstone and basal Tarporley Siltstone, in contrast, the Ni/Al2O3 and Zr/Al2O3 profiles run almost parallel, with Cr/Al2O3 showing a similar trend in the Delamere Member, suggesting that sedimentological factors were the dominant influence."
There are strong differences between the Manchester Marls and the MMG.
"Although SiO2, CaO and LOI in the former lie between the levels of the Tarporley Siltstones and other MMG units, Al2O3, TiO2, Fe2O3, K2O, Cr, Ce, Co, Pb, La, Rb, Nb, V and Y are higher than in the MMG and Na2O and MgO lower."
"This suggests generally that the Manchester Marls have higher quartz and aluminosilicate contents than the MMG and lower levels of carbonates, sulphates and, perhaps, Mg-rich clays."
Many elements are similar to certain groups of the MMG but differ from others.
"The Bollin Mudstones are most similar overall but differ for Nb and Th, as well as the major elements referred to above."
"The SSG was laid down within a long northward-draining fluvial basin system, originating in the Armorican Highlands to the south of Britain and developed along a series of linked Permo - Triassic extensional basins along the west side of the country."
"The lithic clasts and heavy minerals seen in whole-rock petrographic studies of the Kinnerton Sandstone Formation indicate derivation from a complex source terrain, which included high-grade metamorphic rocks, syenite, acid volcanics, quartzite, sandstones and siltstones."
The whole-rock petrography of the Chester Pebble Beds suggests a similarly mixed source terrain.
The greater importance of albite and reduction of volcanic fragments in the Wilmslow Sandstone Formation suggests a continued evolution of the source terrain.
"This trend continued into the Helsby Sandstone, which also, locally, shows clear evidence for inputs from the Lower Palaeozoic of the Midlands or Wales."
"The feldspar may reflect the increased importance of granitic inputs from Armorica or Cornubia, whilst the sedimentary clasts suggest more local sources in the Carboniferous of the Anglo-Brabant Massif, Pennines or Wales and perhaps the Devonian."
"Clasts in the Chester Pebble Beds in the Cheshire Basin, as in other basins, are dominated by quartzite and vein quartz."
"The quartzites rarely contain derived Lower Palaeozoic fossils, and chert and limestone pebbles rarely include Carboniferous fossils."
Previous studies of the Kidderminster Formation of the West Midlands and Budleigh Salterton Pebble Beds of south-west England‚ $ '' equivalent formations to the Chester Pebble Beds ‚ $ '' have identified components of Cornubian and Armorican affinity.
"With the exception of the Kinnerton Sandstone Formation, which displays an apparent decrease in the proportion of polycrystalline quartz to single-crystal quartz and a decline in the content and change in the composition of lithic fragments from south to north, the SSG shows no gross variations in detrital mineralogy across the Cheshire Basin."
"However, there are significant differences between the SSG of the Cheshire Basin and other UK Permo - Triassic basins."
"In the Cheshire Basin, sandstones are characterised by moderately low feldspar contents, and are represented by cherty litharenites and sublitharenites, with quartz arenites becoming more significant in the Helsby Sandstone Formation."
"The SSG of the Wessex Basin is significantly different in character and is represented by very feldspathic sandstones: lithic arkoses, arkoses and subarkoses with up to 55% K-feldspar."
"The SSG of the Lincolnshire‚ $ `` East Yorkshire Basin is similarly feldspathic, although the proportion of K-feldspar."
"Furthermore, the SSG of the Wessex Basin includes a high proportion of detrital Ba-rich K-feldspar."
This is not a characteristic of the SSG of the Cheshire Basin.
"However, whereas detrital chert is prominent in the SSG of the Cheshire Basin it appears to be less significant in adjacent Permo - Triassic basins."
"Since chert is not as important in other basins, the most likely source is from the common cherty horizons in Dinantian limestones of North Wales, the Welsh Borders, the south Pennines and the Midlands."
This suggests that Namurian and Westphalian strata had already been at least partly eroded from these areas.
"There is evidence for this in the South Pennines, where neptunian dykes in Dinantian limestones in the Ashbourne area are filled with probable Triassic sediment, and some pocket deposits in the limestones may be of Triassic age."
"Areas where Dinantian strata are known or inferred to subcrop beneath Permo - Triassic rocks are outlined south of the Pennines, in the Welsh Borders and in the area of the London‚ $ `` Brabant Massif."
"Variations in heavy-mineral assemblages and the chemistry of detrital tourmaline indicate that a number of distinct sources supplied sediment to the Cheshire Basin during the Permo - Triassic, and that these varied in relative importance with time."
"The former characterises the Chester Pebble Beds Formation, whereas the latter is typical of both the earlier."
"The maximum influence of the southerly source took place during deposition of the Chester Pebble Beds Formation, coinciding with the time of greatest runoff from this source and ensuing higher-energy depositional conditions."
"The available regional information on Triassic sandstones of the UK shows an overall decrease in the abundance of detrital monazite from south to north, indicating that the southerly source area was characterised by high amounts of detrital monazite: the progressive northward decrease in MZi values is interpreted as the result of dilution by more local material low in detrital monazite."
"More local sources were of greater importance in the preceding Collyhurst, Kinnerton and associated sandstones and the overlying Wilmslow and Helsby sandstones, in which detrital monazite is markedly less abundant and tourmaline suites are generally more Mg-rich."
Aeolian sandstones in formations below and above the Chester Pebble Beds were dominantly transported from the east.
"During the Triassic, the Pennine area was probably mostly blanketed by Late Carboniferous clastics, but the scarcity of modern heavy-mineral data on Late Carboniferous sandstones from the region prevents a more detailed assessment of their suitability as source material."
The only comparable data presently available are from Namurian sandstones of the Lancaster area.
"It is possible that younger Carboniferous sandstones lacked this component, and it is equally possible that there are regional variations in detrital monazite distribution."
The presence of appreciable amounts of detrital monazite in some samples from the Wilmslow and Helsby sandstones indicates that sediment supply from the south continued throughout the deposition of the later formations of the SSG but that its importance in the Cheshire Basin was markedly reduced.
"The evidence from the Helsby Sandstone of the Thornton Borehole, in which aeolian sandstones have very low MZi values and fluvial sandstones have significantly higher detrital monazite abundances, provides good evidence that the northward-flowing fluvial system was still supplying monazite-rich detritus."
"Thus the fluvial input continued to have a similar character to that of the Chester Pebble Beds, whereas the aeolian sediments appear to have a strong affinity with those of the earlier Collyhurst and Kinnerton sandstones."
"There are stratigraphical and regional variations in the nature of the low-monazite assemblages: for example, the Wilmslow and Helsby sandstones have higher ATi and RZi values and lower rutile/anatase ratios than the Kinnerton and associated sandstones."
"The Wilmslow Sandstone Formation is characterised by two distinct heavy-mineral assemblages, one being apatite-rich and the other apatite-poor."
"There is little evidence that this difference resulted from changes in sediment provenance, and the most reasonable explanation for the variation is that it resulted from apatite dissolution during the interval represented by the Hardegsen disconformity, at the boundary between the Wilmslow Sandstone and the Helsby Sandstone formations."
"Ideally, the variation in apatite abundance should be examined by reference to a cored sequence unequivocally passing through the boundary between the Wilmslow Sandstone and Helsby Sandstone, but no such material was available for study."
The whole-rock geochemistry of the SSG indicates that the predominantly aeolian sediments differed in composition from later sediments.
"The whole-rock geochemistry suggests that the formations above the Chester Pebble Beds contained a certain amount of fluvially transported sediment derived from the south, and elements of this effect were observed in the heavy-mineral investigations."
"Comparison of mainly aeolian facies above and below the Chester Pebble Beds is consistent with the addition of granitic material, presumably from a Cornubian or Amorican source, in the later formation."
"The middle part of the MMG is geochemically distinctive, with a composition suggesting a greater input from a basic igneous source relative to acid igneous or sedimentary components."
The nearest source of basic material was probably the Carboniferous volcanics and intrusives of the South Pennines.
"As part of the present investigation, petrological studies were carried out to address the diagenesis of the Permo - Triassic rocks of the basin and its genetic relationship to the sandstone-hosted red-bed Cu-Pb-Ba mineralisation and hydrocarbons."
The main objectives were: to identify the principal effects of diagenesis on the Permo - Triassic rocks: to establish the relative chronology of diagenetic mineralisation of the fluids responsible for diagenesis and mineralisation.
"Due to the lack of available material, only a very limited study was made of pre - SSG strata."
"A total of 92 samples were analysed by X-ray diffraction analysis to determine their clay mineralogy: 54 samples from the MMG: 35 samples from the SSG, and 3 samples from the Manchester Marls."
A limited number of SSG samples were studied by fission-track registration analysis to examine the distribution and mobilisation of uranium during diagenesis.
Lexan polycarbonate plastic was used as a detector and placed in contact with polished thin sections of SSG.
"Whole-rock geochemical analyses were carried out on 580 samples, including more than 300 from the SSG and more than 200 from the MMG."
"Thermometric data were obtained for inclusions in baryte and calcite cements and fracture mineralisation in the SSG from Alderley Edge, Clive Mine, Bickerton and the Thornton Borehole."
"Much of the SSG was accessible only at the margins of the Cheshire Basin, where samples were obtained from surface exposures, shallow mine-workings borehole cores."
"Because these minerals are extremely soluble, multiple phases of precipitation, dissolution, recrystallisation and redistribution can be expected, and it is in this context that interpretation of the diagenesis of the Permo - Triassic rocks in the Cheshire Basin must be considered."
"Since the diagenetic history of the sandstone and siltstone facies of the Tarporley Siltstone Formation is broadly similar to that of the SSG, it is included in the following discussion."
"In general, eodiagenetic and early mesodiagenetic processes in the SSG sandstones tended to effect a reduction of the primary intergranular pore space through compaction, early pressure solution, grain overgrowth and cementation."
"The diagenetic history of the SSG in the Cheshire Basin can be further subdivided within a relative temporal framework of eight broad Diagenetic Episodes, referred to as DE1 to DE8, along similar lines to that described by Strong et al. for the Permo - Triassic rocks of west Cumbria."
"This summary scheme provides a useful framework within which the diagenetic evolution of the SSG of the Cheshire Basin can be described, interpreted and related to other features such as regional mineralisation and structural and geological events."
Early red-bed diagenetic and pedogenic modification can be recognised in nearly all sandstones from all SSG formations.
"Whole-rock geochemistry of the SSG shows a clear difference in Fe content between reddish brown oxidised facies and grey or grey-green reduced facies, with significantly higher levels in the oxidised rocks."
Similar carbonate spheroids have been described by Strong and Pearce from Permo - Triassic sandstones of Cumbria.
"While eodiagenetic DE1b dolomite occurs widely across the Cheshire Basin in all SSG formations, it appears to be most extensively developed in the Chester Pebble Beds and Helsby Sandstone formations in the north of the basin."
Nodular non-ferroan calcite cement with similar paragenetic and morphological characteristics is also found in the SSG.
"There is some evidence that eodiagenetic calcite is also present in the Chester Pebble Beds of the Newport UDC Borehole, but it is difficult to differentiate it unambiguously from abundant late mesodiagenetic calcite."
The dolomite and calcite cements are similar to eodiagenetic cements described from the SSG in other Permo - Triassic basins and are interpreted as pedogenic or caliche-type dolocretes and calcretes.
"Carboniferous Limestone -RRB-, and it is plausible that HCO3‚ $ `` derived from the dissolution of detrital marine -LRB- ? Carboniferous -RRB- limestone dominated the carbon isotopic signature of the eodiagenetic SSG porewaters."
"The d18O values are heavier than for calcrete calcites from the SSG of the Wessex Basin, although similar to dolocrete from East Yorkshire and Lincolnshire."
Palaeogeographical effects or a greater degree of evaporative enrichment of d18Oh2o in near-surface water recharging the SSG in the Cheshire Basin and the East Yorkshire‚ $ `` Lincolnshire Basin may also account for the difference.
Surface conditions in the Cheshire Basin during SSG times may have been similar to those observed in modern arid continental environments: dolomite precipitated in these environments has typically high d13C and d18O values.
"In this respect, the isotopic characteristics of the nodular eodiagenetic dolomite in the SSG are similar to those of the primary dolomicrite in the overlying MMG."
"MMG dolomicrites are closely associated with, and interlaminated with, primary anhydrite."
"In the Cheshire Basin, the diagenetic zonation parallels the drainage direction of the Lower Triassic fluvial system."
"However, in the Helsby Sandstone Formation in the Saughall Massie Borehole, SEM-EDXA indicates that these coatings are Mg-rich saponitic, smectitic or corrensitic clay."
Framboidal pyrite was seen very rarely in the SSG and Tarporley Siltstone Formation.
"It occurs in trace amounts in the Helsby Sandstone Formation of the Hondslough Farm Borehole but is more abundantly developed in the muddier sediments of the Tarporley Siltstone Formation, as in the Saughall Massie and Marston Salt Union boreholes."
DE3 dolomite and DE3-recrystallised early dolomite nodules are the dominant carbonate cement in much of the SSG around the northern rim of the Cheshire Basin.
In this respect DE3 dolomite is similar to early mesodiagenetic non-ferroan dolomite described by Burley from the SSG in Lancashire.
"Burley identified up to 12 cathodoluminescence colour zones in the quartz cements of the SSG of the Kirkham Borehole, near Preston."
These petrographic relationships suggest that the SSG was actively undergoing the early stages of burial during DE4 quartz‚ $ `` feldspar mesodiagenesis but had not yet achieved maximum burial compaction.
"For example, it is well developed in the Helsby Sandstone Formation but absent in the Wilmslow Sandstone Formation in the Marston Salt Union Borehole."
"Generally, however, authigenic DE4 quartz tends to form only minor or patchy cements in most of the SSG from around the north-western and western margins of the basin."
It is particularly well developed in certain sandstone beds in the Helsby Sandstone Formation.
"Much of the intergranular porosity in the SSG is secondary porosity, resulting from the dissolution of an earlier diagenetic pore-filling cement."
Burley suggested that much of the secondary porosity in the SSG resulted from late mesodiagenetic carbonate cement dissolution.
"Strong suggested that anhydrite, gypsum and possibly halite were precursor cements that were later removed to yield secondary porosity in SSG rocks of the Preston area of Lancashire."
Anhydrite is a very likely candidate cement: poikilotopic anhydrite is observed as a major cement in the Malpas Sandstone of the Wilkesley Borehole.
"Halite and anhydrite are both seen cementing siltstones and fine sandstones in parts of the overlying MMG, but halite was not directly observed in the SSG."
Anhydrite cements are a common feature of the SSG in many UK Permo - Triassic basins.
Its removal during late mesodiagenesis and/or during telodiagenesis appears to account for much of the secondary porosity in the SSG in these basins.
The early stages of this episode are evident in numerous small faults in the the SSG.
Similar features can be seen offshore in the underlying Collyhurst Sandstone.
Similar late fracture-mineralising dolomite enclosed in anhydrite occurs in the Byley Mudstone Formation of the Crewe Heat Flow borehole.
"In contrast, d13C is similar to that of the earlier carbonates, which suggests that the carbon isotopic signature of the pore fluids during early DE6b was still largely influenced by re-working or dissolution of detrital carbonate components within the SSG."
"Within the SSG and the Tarporley Siltstone Formation, DE6c is only recognised in the Malpas Sandstone and Tarporley Siltstone Formation of the Wilkesley Borehole."
Similar anhydrite veining is seen in the overlying Bollin Mudstone Formation.
"This suggests that DE6c was widespread in its influence, affecting the MMG in addition to the SSG."
Copper sulphides and pyrite ¬ ± a complex assemblage of Pb-Zn-As-Ni-Co-Ag-Hg-Bi-Mo-Se sulphides are found in the SSG to the south-east of the Mersey and in the Wirral Peninsula.
"Minor galena, sphalerite, and Ni-Co-As-Cd-sulphide mineralisation, associated with bituminous hydrocarbon residues containing concentrations of uraninite and uranium silicate, are found locally within the underlying Manchester Marls and appear to belong to the same episode of diagenesis."
"In most samples the sulphide paragenesis is unclear, but in siltstones and sandstones in the Tarporley Siltstone and Helsby Sandstone formations of the Saughall Massie, Hondslough Farm and Coton Fields boreholes, minor early DE1 framboidal pyrite is seen to be overgrown and included within coarser euhedral DE6d pyrite which, in turn, is partially replaced and overgrown by minor chalcopyrite."
Similar sulphide mineralisation relationships are observed in the SSG in the Stowell Park Borehole -LSB- SP084118 -RSB- in the Worcester Basin.
"The heavy DE6e calcite d13C signatures in the south of the basin closely resemble early DE1b-DE3 carbonate signatures, suggesting that DE6 carbonate was derived largely by re-working of early diagenetic and detrital carbonate components within the SSG."
"This implies that deeper-sourced fluids, probably from basement Carboniferous rocks undergoing thermal maturation of organic matter, significantly influenced DE6e carbonate diagenesis and mineralisation in the northern and north-western part of the basin."
Carboniferous -RRB- rocks undergoing thermal maturation.
"South of this area, there is little evidence of deeper-sourced fluids having influenced the SSG."
Fluids here were more oxidising and the carbon-isotope composition was influenced largely by fluid‚ $ `` rock interactions within the red-bed SSG.
"In this respect, the slightly heavier d18O found in DE6 carbonates in the south of the basin is also consistent with greater influence of water‚ $ `` rock interaction within the Permo - Triassic pile, in contrast to significant influence from deeper-sourced fluids at higher temperature."
"Many of the samples are enriched in Cu, Pb, Zn, MnO, Ba, Sr, Co, Ni, As and Cr, with concentrations significantly above the median values for the Helsby Sandstone."
"SiO2 values are generally greater than the Helsby Sandstone median of 84.30% on the lower and upper levels, but at or below the median for the middle level."
"Based on criteria discussed above, it is clear that much of the present porosity in the SSG and Tarporley Siltstone Formation is secondary."
Minor hydrocarbon shows are found within the SSG around the basin margin.
Late telodiagenetic effects are evident in much of the unconcealed SSG and Tarporley Siltstone Formation from around the basin margins.
"Caution is therefore required when interpreting the trace-element characteristics of the SSG rocks, especially with respect to the transition metals and other redox-sensitive elements, which have quite clearly been remobilised and redistributed in most of the samples examined."
"Whole-rock geochemistry of the SSG shows a good correlation between CaO, MgO and LOI."
The Kinnerton Sandstone shows strong calcite and dolomite trends.
The Chester Pebble Beds also show both calcite and dolomite trends.
"As in the Kinnerton Sandstone, higher dolomite values are restricted to the north-west of the basin, but high calcite contents occur in both the south-east and the north-west."
The Wilmslow Sandstone generally has low levels of carbonates.
"Dolomite also seems to be the more important carbonate in the Helsby Sandstone, with maximum levels up to about 25%, although most samples have less than 6%."
"There appears to be some facies control of the preserved carbonate content: greater quantities are found in the Chester Pebble Beds and Helsby Sandstone, which contain significant fluvial facies, than in the Wilmslow or Kinnerton sandstones which, in the samples collected, were dominantly of aeolian origin."
The MMG shares many sequences of diagenetic cements and vein-fills in common with those found in the underlying SSG.
The Tarporley Siltstone Formation shows very similar characteristics to the SSG and the description of its diagenesis has been largely included with that of the SSG strata.
"As in the SSG, diagenetic modification can be ascribed to eodiagenetic processes."
The most visually distinctive diagenetic feature is the green and red colouration commonly observed in the MMG.
"In the laminated facies, which occurs chiefly in the Bollin Mudstone Formation and Byley Mudstone Formation, there are alternations of oxidised and reduced laminae."
Previous geochemical studies in the MMG have shown that the reduced laminae generally contain less ferric iron than the interbedded oxidised laminae.
Examination of spidergrams of oxidised and reduced laminae in the MMG confirms that in most sets of neighbouring samples Fe2O3 contents are lower in the reduced laminae.
"In other examples, such as the Byley Mudstones of Crewe Borehole, the reduced samples contain more sand or silt than the neighbouring oxidised samples and hence have higher SiO2 and lower Al2O3."
As discussed in connection with the SSG.
"The pyrite in the MMG is clearly eodiagenetic and can be seen to predate compaction, as demonstrated by compactional deformation of sedimentary laminae, and less competent mica grains, around framboidal aggregates."
"This caused expansive disruption of sedimentary fabrics and is therefore considered to have formed near-surface, probably in evaporitic or sabkha-type environments in the MMG."
Patchy micritic non-ferroan calcite cement is also locally present as expansive nodules within pelloidal mudstones in the Brooks Mill Mudstone Formation and may represent calcrete development.
"Early diagenesis can be summarised as follows, using the scheme adopted for the SSG: DE1a: synsedimentary development of red-bed clay and iron-oxide grain coatings."
"DE2a: early pore-filling and pore-lining authigenic corrensite and smectite: these were recognised in the Tarporley Siltstone Formation directly as authigenic minerals, but corrensite identified by XRD in other formations is consistent with early synsedimentary evaporative lacustrine environments."
This broadly resembles DE1‚ $ `` 3 diagenesis in the SSG.
"However, since these features are synsedimentary in origin they are obviously not syngenetic with DE1 diagenesis in the SSG -RRB-."
Burial diagenesis in the MMG shows many similarities with the sequences of cement and vein paragenesis in the underlying SSG and is summarised in Table 23.
A parallel can be seen between this and the DE2 to DE3 stage of diagenesis defined in the SSG.
Quartz cements clearly developed after the formation of dewatering fabrics observed in the MMG.
"Within the main halite of the Northwich Halite Formation and in anhydrite beds in the Wych Mudstone Formation, authigenic euhedral porphyroblasts of quartz are developed, locally replacing the evaporites and also preserving, as corroded inclusions, early unrecrystallised and largely uncompacted primary aphanitic anhydrite fabrics."
The paragenetic relationship of silicate authigenesis in the MMG mirrors DE4 in the SSG.
Poikilotopic anhydrite cements appear later during the diagenesis of the MMG.
Halite has been clearly remobilised during mesodiagenesis and reprecipitated within veins and as poikilotopic cements in the MMG.
These fabrics again mirror the DE5 stage evaporitic cements postulated in the SSG.
Late-stage ferroan dolomite and ankerite occur as rhombic overgrowths on corroded mesodiagenetic dolomite in the Brooks Mill Mudstone Formation.
"However, in the Crewe Heat Flow Borehole veins of place ferroan dolomite - ankerite authigenesis in the MMG in a similar paragenetic position to DE6b features in the SSG."
"The framboidal pyrite in the MMG is commonly overgrown and replaced by later diagenetic sulphides of Cu, Fe¬ ± Zn, Pb, As, Co, Ni, Ag, Hg and, rarely, traces of Ag-Cu-Au."
In the Brooks Mill Mudstone Formation chalcopyrite and late relatively coarsely crystalline pyrite both replace and pseudomorph small clustered needles and swallow-tail crystals of eodiagenetic gypsum.
"This sequence: early framboidal pyrite, followed by coarser pyrite, overgrown and overprinted by chalcopyrite, corresponds very closely with the paragenetic relationships illustrated by DE6d in the SSG."
"Samples from oxidised and reduced laminae of the Byley Mudstone Formation in the Crewe Borehole are seen to be very similar in chemical composition, the only systematic differences being that Fe is lower and Cu higher in the reduced laminae than in neighbouring oxidised laminae."
"In a suite of samples from the Tarporley Siltstone Formation of the Saughall Massie borehole the reduced samples contain more Ca than the oxidised samples, accompanied by higher Mg and Mn."
"The differences between the oxidised and reduced samples observed in the Byley Mudstone are also apparent in the Tarporley Siltstone, and additionally the reduced laminae are here enriched in Co.."
"This can be attributed to later minor to trace chalcopyrite, chalcocite and covellite authigenesis in the green facies of the Tarporley Siltstone Formation."
"Similarly, rare late cross-cutting calcite veinlets carrying small amounts of baryte may be correlated with DE6e calcite veining in the SSG."
Apart from late fibrous pore-lining illite in the arenaceous facies of the Tarporley Siltstone Formation the higher stratigraphical units do not appear to demonstrate diagenetic features similar to DE7 in the SSG.
"The most significant telodiagenetic effect in the MMG is the development of collapse breccias and major subsidence associated with the large-scale dissolution of thick halites by contemporary groundwater, particularly around Nantwich in Cheshire."
"However, other telodiagenetic effects include the hydration of anhydrite cements and their replacement by gypsum in near-surface MMG rocks."
Sulphur-isotope data of sulphur-bearing mineral species may be used to place constraints on the source of sulphur in the red-bed mineralisation in the SSG.
"It has been proposed earlier, that the SSG may have had significant anhydrite cement prior to DE6 mineralisation and this could have provided an in situ source of sulphate."
Carboniferous basement -RRB- to the north of the Mersey and in the Chester area.
Naylor et al. noted that the baryte from Clive‚ $ `` Grinshill and Bickerton was isotopically similar in d34S values to the evaporites within the MMG.
They therefore concluded that much of the baryte sulphate was derived ultimately from Triassic evaporites.
"They invoked the involvement of a lighter sulphate component, derived by oxidation of reduced sulphide from the underlying Carboniferous, to account for the lighter baryte in the Alderley Edge area."
Their comparisons of baryte with evaporite sources were based on only three samples of anhydrite and gypsum for the Brooks Mill Mudstone Formation.
"A more systematic study of sulphur isotope variation within the MMG evaporites in the Cheshire Basin was undertaken in the present study, and the data are summarised in Figure 104."
d34S data for sulphates were obtained from all formations except the Byley Mudstone Formation and Northwich Halite Formation.
"Consequently, hydration and replacement of primary anhydrite by gypsum will not produce any significant isotopic fractionation, and secondary gypsum should be similar to the original anhydrite, which in turn should closely approximate to the d34S value of the lacustro-marine waters from which the MMG was deposited."
"The data show that below the Byley Mudstone Formation, d34S compositions of MMG evaporites closely follow the Triassic marine sulphate evolution, indicating a strong influence of Triassic marine-derived sulphate in the evaporitic and sabkha sediments of the Lower MMG."
"The S isotopic compositions are significantly depleted in 34S, with respect to the Triassic sea-water curve, in the Wych Mudstone Formation and again in the Brooks Mill Mudstone Formation."
"This indicates a strong continental-derived brine influence, and greater isolation from Triassic marine circulation, in the Wych and Brooks Mill Mudstone formations."
The lighter d34S sulphate in these continental brines could feasibly have been dominated by re-working of earlier Permian sulphates.
"Although only a single analysis was obtained from the Wilklesey Halite Formation, the d34S value of primary anhydrite indicates a return to an evaporative environment influenced by a Triassic marine sulphate source, and is consistent with the development of a large thickness of halite in this formation."
Figure 104 shows that the MMG sediments and DE1 evaporites generally became progressively depleted in 34S with time: from values between 14.8 ‚ $ ∞ and 20.8 ‚ $ ∞ in the Tarporley Siltstone and Bollin Mudstone formations to values between 10.3 ‚ $ ∞ and 14.3 ‚ $ ∞ in the Brooks Mill Mudstone Formation.
Comparison of these data with baryte from the SSG - hosted Cu-Pb-Ba mineralisation clearly shows that the d34S values for baryte are all within the range of values of primary evaporites in the MMG.
"Since little 34S fractionation occurs between solution and mineral on dissolution and re-precipitation of anhydrite or gypsum at low temperature, the baryte compositions in the SSG can all be accounted for by precipitation from sulphate ultimately derived from the MMG."
The differences in d34S between the Alderley Horst mineralisation and Cu-Pb-Ba mineralisation in the south of the basin may simply reflect tapping of brines or sulphate sources from different parts of the MMG.
The d34S data suggest that sulphur in the mineralised areas in the south and west of the basin was originally derived from sulphate brines dominantly tapped from sources within the lower part of the MMG.
"In contrast, the Alderley Horst mineralisation has d34S signatures that could reflect sulphate from brines derived throughout most of the MMG sequence but with a possible bias towards sediments between the Bollin Mudstone Formation and the Wilkesley Halite Formation."
The subtle differences in metalliferous mineralisation between the different areas may similarly be related to different parts of the MMG being brine-tapped.
"For the SSG, detailed examination of more than 30 sandstone samples failed to identify early diagenetic for microthermometric analysis in the quartz overgrowths or carbonate cements."
"To address the mineralising role of gravity - driven evaporite brines from the MMG into the underlying SSG, a laser ablation ICP-MS analysis was carried out of liquid inclusions in halite from the Wilkesley Halite Formation."
"In the Wilkesley Halite, the halite is commonly intergrown with reddish-brown mudstone and displays relic chevron or cornet textures suggesting primary crystallisation fabrics."
The preferred temperature regime is in good agreement with the estimated mean basin temperature of ~ 60¬ ∞ C at the base of the SSG for the end of the Triassic.
Fluids associated with fracture-controlled calcite‚ $ `` pyrite mineralisation in the SSG of the Thornton Borehole on the fringe of the East Irish Sea Basin.
"Data for the stratigraphically lowest samples in the Wilkesley Halite Formation are conspicuously depleted in K, Mn, Cu, Rb, Ba and Pb compared with data from all higher samples."
"Values for Mg and K are in good agreement with the fluid data for massive Miocene halite units in the Lorca basin, south-east Spain."
Thus the evaporite bitterns of the MMG constitute a newly discovered and potentially major source of metals for sandstone-hosted mineralisation in the Cheshire Basin.
"One sample, from a seep in Westphalian strata at Hem Heath Colliery just outside the south-east margin of the basin, is a mature, light crude oil, showing few signs of oxidation or biodegradation."
The data are consistent with migration of hydrocarbons from the Westphalian sequence beneath or adjacent to the basin.
This component was derived from organic matter subject to a higher degree of thermal maturation probably within Carboniferous strata.
Detailed petrographic and stable-isotopic investigation of the SSG and MMG in the Cheshire Basin have revealed a complex sequence of diagenetic modifications.
Early diagenesis of the SSG in the Cheshire Basin was similar to that observed in other UK Triassic basins.
There is some evidence of possible zonation in the distribution of calcrete and dolocrete within the lower part of the SSG.
Similar early diagenetic processes affected sandy facies in the MMG.
Sulphur-isotope data for the lower MMG and the later Wilkesley Halite Formation indicate that primary and eodiagenetic evaporites were derived largely from brines of Triassic marine origin.
"However, evaporites formed during the middle MMG."
"The effect was to produce characteristic reduced green beds and reduction spots, common in the MMG and seen locally in the finer-grained parts of fluvial cycles in the SSG."
"Authigenic smectitic and corrensitic pore-lining clays precipitated in some sandstones in the Helsby Sandstone and Tarporley Siltstone formations, and in part replaced detrital clays and micas."
Corrensite was identified in most MMG formations but its diagenetic fabrics were not observed.
"It seems likely, therefore, that the corrensite observed in the MMG is similarly of eodiagenetic origin, since the depositional environments of the MMG were likely to have been hypersaline."
Neoformation and overgrowth of idiomorphic dolomites and the formation of authigenic quartz and feldspar cements and overgrowths are common features in both the SSG and the MMG.
"In the MMG, evidence can be found for early diagenetic dissolution of halite."
Later mesodiagenetic fabrics show that anhydrite was remobilised and redistributed as a mesodiagenetic in siltstones and dolomicrites in the MMG.
"Many of the porous sandstones of the SSG have fabrics indicating that the porosity is largely secondary, resulting from the dissolution of an early mesodiagenetic cement."
Many of the diagenetic features are common to both MMG and SSG rocks.
"However, eodiagenesis and early mesodiagenesis within the MMG and SSG were obviously diachronous since they are contemporary with sedimentation and shallow burial."
"However, it seems very likely that later mesodiagenesis in both formations was linked and related to brine expulsion along permeable paths during burial dewatering of the MMG."
Copper is variably enriched in the reduced beds of the MMG.
It is suggested that diagenetic brines in the MMG mobilised these metals in solution and were thus a potential source of mineralising fluids‚ $ '' as is also seen from the geochemical compositions of fluid inclusions trapped within MMG halites.
"The quantities of metals involved are not great, possibly because of the limited supply of reduced sulphur, but the presence of metal sulphides in the reduced laminae of the MMG illustrates, in microcosm, the processes by which migrating Cu-bearing saline solutions deposit their load of Cu when they encounter reducing conditions."
Similar authigenic sulphide paragenetic assemblages are observed in the SSG.
No evidence could be found for the migration of liquid hydrocarbons into the SSG before or during base-metal mineralisation.
"Though the presence of gaseous hydrocarbons in the SSG prior to mineralisation can not be discounted, a model for sulphide deposition involving light hydrocarbon gases remains unproven."
"Chemical analysis of brine inclusions in halite from the Wilkesley Halite Formation demonstrates that the early diagenetic evaporite fluids were already significantly enriched in Cu, Pb and Ba prior to their migration into the SSG."
Subsequent leaching of metals from the SSG would further enhance their mineralising potential.
Sulphur isotope data provide strong evidence that the sulphur in DE6 sulphide mineralisation and associated baryte mineralisation was derived from the overlying MMG.
"However, petrographic evidence alluded to above indicates that this sulphur was already in place, probably as anhydrite cementing the SSG sandstones, and therefore was not brought into the SSG at the same time as the metals."
This implies that anhydrite-saturated brines must have penetrated from the MMG into the SSG during DE5.
"Later DE6 brines from the MMG may have been low-sulphate NaCl brines, in contrast to the earlier DE5 anhydrite-saturated fluids."
Petrographic observations in the MMG show that anhydrite is corroded by NaCl brines during halite remobilisation.
"The late DE6 NaCl-type brines would have dissolved the anhydrite cements on entering the SSG, and immediately any Ba in solution would have been deposited as baryte."
"This is consistent with the fracture-controlled distribution of baryte in the SSG, and with the evidence for several different fluids having been produced in the MMG at different times."
Differences in the sulphur isotopic signature of baryte between different deposits across the basin can be accounted for by differences in the stratigraphical level of the MMG from which the DE5 anhydrite-mineralising brines were originally sourced.
"In the south and west of the basin, DE5 fluids have affinities suggesting derivation largely from the lower part of the MMG."
"In contrast, isotopic signatures in the Alderley Horst area suggest that DE5 brines were derived from a slightly higher stratigraphical level in the MMG."
The mechanism for metal-sulphide precipitation in the SSG is more problematic since it requires reduction of the sulphate.
It is unlikely that this component was introduced in the late DE6 metalliferous brines derived from the MMG because the reducing nature of the fluid would have severely limited the transport of Cu.
"This dominance may be related to geographical differences in the nature of the basement underlying the basin, and/or to fluids interacting with different parts of the Carboniferous sequence due to variations in the nature of the subsurface plumbing system."
This comprehensive publication was used to follow the development of the Cheshire Basin from Permian times to the present day.
Early Permian deposition in the Cheshire Basin area was characterised by aeolian sands and sand dunes in a desert environment.
"During the late Permian, the Zechstein Sea encroached from the east and the Bakevellia Sea extended into Lancashire as far as Manchester but did not cover the Cheshire Basin."
"In the early Triassic sandy conglomeratic deposits continued to be laid down, the sediments being derived from the south."
"By the mid - Triassic, the system drained into a shallow hypersaline sea to the north of the Wirral."
"In late Triassic times, the Cheshire Basin area was again an area of alluvial deposition and a shallow fresh groundwater system was probably established, while saline water probably persisted at depth."
"During the latest Triassic, shallow seas covered the area and saline water would probably have displaced any fresh groundwater as the sea encroached over the land."
"Jurassic sediments were deposited and eroded sequentially in the Cheshire Basin throughout the period, though few are now preserved."
"During the early Jurassic the Cheshire Basin area was inundated, and the surrounding area contained several land masses."
In mid - Jurassic times which extended to the southern Irish Sea.
The sea varied in extent throughout the mid - Jurassic but did not inundate the Cheshire Basin until c. 158Ma.
During the remainder of the mid - Jurassic and into the late Jurassic the area remained submerged but the sediments deposited there have been subsequently eroded.
The Cheshire Basin was again emergent as part of the largely low-relief Anglo - Welsh land mass in late Jurassic times.
During the early Cretaceous the Cheshire Basin was an area of low relief: the Pennine land mass lay to the north-east and the Welsh land mass to the south-west.
Fresh groundwater in the Triassic sandstones would probably have been replaced by saline water.
"Most of the British Isles was land throughout the Tertiary, although the coastline moved considerably during the period."
In mid to late Oligocene times a south-west-flowing river in the southern Irish Sea is postulated.
Sea-level fluctuations during the Quaternary would have resulted in coastlines moving and base drainage levels changing.
The palaeo-hydrogeological reconstruction suggests that the Cheshire Basin would have been filled with highly saline brines during Permian and Triassic times except during the later Triassic when a shallow fresh groundwater system may have been established.
"With alternating inundation and emergence during the latest Triassic and in Jurassic and Cretaceous times, shallow fresh groundwater systems would be periodically established and then replaced by encroaching saline water."
"The density of this water would, however, be less than that of the Triassic brines, some of which could be present at depth to this day."
"Since the last major inundation of the Cheshire Basin in the Cretaceous, uplift and erosion has established shallow, fresh groundwater systems superimposed on deeper saline and brine groundwater systems, particularly where the arenaceous aquifers are unconfined."
"With removal of Cretaceous and Jurassic sediments, these systems would have evolved into the present system."
"On a local scale, the SSG consists of several aquifer units with varying rest water levels over short distances."
"Along the south-east margins of the SSG outcrop the potentiometric surface is up to 100m above OD, though 40 to 50m above OD is more common."
"The mudstones of the Manchester Marls, which separate the Collyhurst Sandstone from the Triassic aquifers, form a significant barrier to groundwater flow in the north of the basin as they dip southward beneath the Mersey."
These groundwater flow regimes are the present-day active systems where the SSG is not overlain by the MMG.
Most recharge reaches the SSG via the thick cover of drift.
"In the west of the basin, the SSG is in contact with Lower Carboniferous Limestone through a series of en-echelon faults with throws up to 300m locally."
"A long history of over-pumping from boreholes on both sides of the Mersey estuary, particularly at Liverpool and along the Manchester Ship Canal, has resulted in saline intrusion into the Permo - Triassic aquifer."
Geophysical logs from NCB boreholes indicate high-salinity groundwater in the Collyhurst Sandstone in the north of the basin.
This salinity is found to the base of the aquifer at 850m where it overlies the Carboniferous.
"Similar profiles are found in several boreholes: in some the salinity rapidly increases beneath the Manchester Marls, which restricts groundwater flow and has isolated the Collyhurst Sandstone aquifer from overlying sandstone units."
Further evidence of saline groundwater at depth was obtained from a sample collected near Chester from the Coal Measures underlying the Triassic at a depth of about 500m.
"The spring issues from Drift underlain by the Erbistock Beds of the Coal Measures, which form an inlier to the south of Chester."
The driving force required to cause the saline water to rise to the surface may originate in the outcrop of Coal Measures to the west or from the density-driven system beneath the MMG to the east.
"Where the SSG underlies the MMG, however, the aquifer has not been exploited and the only information available is from a few deep wells drilled for research or hydrocarbon exploration."
Temperature gradients in the MMG are around 23¬ ∞ C/km and in the SSG are about 14¬ ∞ C/km.
"The source of the brine was assumed to be the MMG, where extensive halite beds are found."
"The freshwater calculations were run as a steady-state simulation while the brine-driven flows were followed in transient mode from an initial condition in which all water was fresh, except in the source zone of the MMG, until an apparent steady state was achieved."
"In addition, the MMG forms a confining layer to the Triassic sandstone aquifers, which are under artesian conditions in this calculation."
"Flow rates in the sandstone layers are typically of the order of 5 e‚ $ `` 10 m/s from east to west, while those in the MMG are of the order of 3 e‚ $ `` 11 m/s."
The second calculation that was performed assumed that saturated brines with a density of 1200 kg/m3 form a continuous band in the lower part of the MMG.
"It is seen that the flow is now generally downwards in the central part of the basin under the influence of the dense brines originating in the MMG, reversing the artesian conditions suggested by the freshwater calculation."
"Flow rates in the sandstone layers are typically of the order of 7 e‚ $ `` 11 m/s, while those in the MMG are of the order of 5 e‚ $ `` 11 m/s."
Flow rates in the MMG are reduced to about 2 e‚ $ `` 11 m/s.
"The mixing vortex on the eastern margin has now expanded to cover about half the basin, and the upper part of it introduces lower-density fluid to much of the upper SSG."
The densest fluid is now restricted to a descending plume whose location may be determined by the shape of the lower boundary of the MMG.
"The groundwater flow in the MMG is no longer uniformly up or down but may vary from place to place, and the flow rates are reduced to the order of 5 e‚ $ `` 12 m/s."
"Second, the central basin, covered by the MMG, where flow is strongly influenced by the density variations arising from halite dissolution and mixing with fresh water near the margins."
"Red beds play a fundamental part in the genesis and spatial distribution of natural resources, being important hosts of hydrocarbon accumulations and deposits of metalliferous minerals worldwide."
Waters from Permo - Triassic red beds in the Wessex Basin reach temperatures of more than 75¬ ∞ C and can be considered diagenetic waters.
"Most deep waters in Permo - Triassic red beds of the UK are of Na-Cl type: salinities are highly variable, but may approach halite saturation."
"Most of the salinity appears to come from halite dissolution in the Permo - Triassic, and it seems likely that this process has been a major control of water salinity throughout diagenesis."
"Edmunds et al. found that invasion of meteoric waters into the SSG had flushed any pre-existing Na-Cl-dominated saline waters from the aquifer, and that the groundwater chemistry was dominated by reactions with carbonate cement, detrital dolomite and sulphate minerals."
"In the SSG of the east Midlands, pH increased from about 7 to about 8 at greater distances from the outcrop."
"Burial depths during ore deposition in many sedimentary basins such as the Permo - Triassic basins of the UK often suggest maximum formation-water temperatures between 100¬ ∞ C and 200¬ ∞ C, which are higher than temperatures estimated for Alderley Edge."
"Campbell described the permeability of the Permo - Triassic sandstones of the lower Mersey basin, using data from boreholes at High Croft Farm, Padgate, Halewood and Kenyon Junction."
"In addition, two recent studies describe the hydrochemistry of the Permo - Triassic aquifer in the northern part of the Cheshire Basin, near the Mersey."
"Accordingly, the observation wells are generally in areas underlain by sediments of the SSG, which form the major groundwater aquifers."
"There are very few wells located on areas underlain by the MMG, since this generally acts as an acquiclude."
SJ/56/61 -RRB- and a water analysis is available for a sample from the SSG at 305m depth in this borehole.
"Additionally, a groundwater sample from a borehole near Chester, from a depth of approximately 500m in the Coal Measures, was analysed for major, minor and trace elements, and for 18O/16O and 2H/1H isotopes."
"A similar decrease in heavy-isotope abundances with increasing depths has been described from the East Midlands Triassic aquifer and has been interpreted as a palaeoclimatic effect, with the most depleted samples reflecting recharge during Pleistocene glacial episodes."
He pointed out that the saline waters did not necessarily arise through evaporite dissolution during the Pleistocene.
"The water sample from the Coal Measures in the borehole near Chester gave d18O = ‚ $ `` 6.9 ‚ $ ∞ and d2H = ‚ $ `` 43‚ $ ∞, suggesting that the basement waters in this borehole are meteoric in origin, like the inland waters sampled by Lucey from the Permo - Triassic."
"Mean Br concentrations for a number of groundwater samples from the Cheshire Basin are plotted against corresponding Cl concentrations in Figure 132, together with similar data from other UK Permo - Triassic aquifers."
The Br/Cl ratio in the water from the Coal Measures in the borehole near to Chester requires some other explanation.
The fact that the salinity of the Coal Measures water is close to that of sea water precludes the possibility that the Coal Measures water acquired its salinity from sea water and its isotopic signature through mixing with dilute meteoric water.
"Instead, the most likely source of the salinity is halite dissolution in the Permo - Triassic basin fill."
"However, as explained above, a water which had acquired its salinity through evaporite dissolution would be expected to have a Br/Cl ratio significantly less than the sea-water ratio, whereas the Coal Measures water has Br/Clmolar = 2.0231 ‚ $ `` 3, some 30% higher than the sea-water value."
"A possible explanation is that the water, having acquired its Na-Cl-dominated salinity through halite dissolution in the Permo - Triassic sequence, subsequently gained Br by reaction with organic matter in the Coal Measures."
Reactions involving organic matter have been postulated as a possible cause of high Br/Clmolar ratios of up to 4.0831 ‚ $ `` 3 in the Coal Measures of north-east England.
The Cheshire Basin groundwaters are generally similar to those from other Permo - Triassic aquifers.
"Most of the groundwater samples from the Permo - Triassic sequence contain less than 1000mg/l TDS, with a maximum salinity of about 20000mg/l TDS."
"This sample set is biased towards fresh waters, since most samples were taken from wells designed to monitor water supplies for domestic consumption, located in areas where MMG is absent, but there is other evidence to suggest that the groundwaters throughout the basin generally have low salinities and never become brines the salinity of the single water sample from the Coal Measures in the borehole near Chester was only 0.85 3 sea-water concentration."
"A halite - equilibrated water at 25¬ ∞ C would have a salinity of c. 7.53 sea water, and other Permo - Triassic basins in the UK with halite - bearing evaporites do in fact contain brines."
"Indeed, in the Wessex Basin, formation waters in Permo - Triassic aquifers approach halite saturation."
A possible explanation is that the meteoric water has continued to flush the SSG via recharge in the south-east and discharge in the west and north.
"It is likely that the water from the Coal Measures in the borehole near Chester acquired its salinity through halite dissolution, suggesting that groundwater has passed into the basement from the basin fill: there are no known evaporites in the region except for those in the Permo - Triassic sediments of the Cheshire Basin."
"It can be seen from Table 34 that the modern groundwaters from the Permo - Triassic rocks of the Cheshire Basin are generally oxidising, and the measured Eh values are reasonably consistent with the waters having being influenced by the atmosphere."
"Although the redox-pH conditions of the modern formation waters from the Permo - Triassic sequence do seem consistent with some possible mobilisation of Cu, the actual measured levels of dissolved Cu are low and, as expected, these dilute waters are unlikely to give rise to Cu ore deposits."
"As in the case of Cu, the concentrations of Pb and Zn in the shallow groundwaters from the Permo - Triassic sequence are low and hence these waters would not be likely to form deposits of Pb or Zn."
"In contrast to the shallower waters from the Permo - Triassic basin fill, the groundwater from the Coal Measures in the borehole near Chester gave Eh = ‚ $ `` 38 mV, consistent with basement waters being more reducing than waters from the cover sequence."
"This result is to be expected because the Coal Measures have a much larger organic content than the Permo - Triassic strata, and the sample from the Coal Measures was taken from a relatively great depth so that it was more likely to be isolated from the atmosphere than shallower samples."
"These observations suggest that although the water in the Carboniferous basement probably originated in the Permo - Triassic cover, it has been resident in the Coal Measures for long enough to be reduced through water‚ $ `` rock interactions."
There are no analyses of heavy metals for the groundwater from the Coal Measures in the borehole near Chester.
The general characteristics of the Permo - Triassic sediments which fill the Cheshire Basin are typical of red beds.
"Also, these comparative and theoretical investigations suggest a likelihood that the metal-bearing fluids which gave rise to the ore deposits in the basin originated within the Permo - Triassic fill as saline formation waters with TDS up to c. 10 3 sea-water concentration."
"By analogy with other red-bed basins, peak temperatures in the Cheshire Basin probably lay within the range 60¬ ∞ ‚ $ `` 150¬ ∞ C. However, if a late Triassic age is accepted for the Alderley Edge mineralisation, temperatures are likely to have below 100¬ ∞ C over the greater part of the basin."
"In the Cheshire Basin, the mineralisation is generally related to structural traps where faulting juxtaposes red-bed aquifers against relatively impermeable mudrocks, particularly those in the MMG."
The possibility that ore formation might be due to migration of hydrocarbon fluids was first suggested by Warrington postulated that methane derived from the underlying Coal Measures was the reductant.
"In contrast, any reducing water from the Carboniferous is unlikely to have contained proportionately greater amounts of sulphate and may therefore have mobilised relatively large quantities of Ba."
"The presence of baryte widely distributed throughout the SSG is not accounted for by the theoretical model, and may in part be due to the release of Ba into formational fluids during feldspar diagenesis and the precipitation of baryte when these fluids mixed with waters having a high sulphate content derived from evaporite dissolution."
The waters from the Permo - Triassic aquifers are significantly more oxidising than the water from the underlying Coal Measures.
"If the measured Eh values are indeed representative of in situ redox conditions, and if the water in the Coal Measures did indeed originate in the Permo - Triassic fill of the basin, then the implication is that this latter water has acquired its redox state during water-rock interactions within the Coal Measures."
"Since the deep borehole near Chester was located near the margin of the basin, it is possible that the waters sampled from the Coal Measures there were recharged from the basin margin, and that in fact fluid flow was the reverse of that in the ore genetic mixing model."
"The main conclusions of the study of the current basinal groundwater flow system, the palaeohydrogeology and the role of fluids in the diagenesis and emplacement of minerals can be summarised as follows: Red beds play two important roles in the occurrence of sedimentary-basin resources: firstly, they act as a source of heavy metals, which are bound in the solid phases or dissolved in metalliferous formation waters: and, secondly, owing to their high mean porosities and permeabilities, they act as conduits for groundwater flow during basin evolution and may become reservoirs for mineralising fluids, hydrocarbons or groundwater."
Red beds may also act as chemical conditioning agents for groundwaters passing through them.
"Red beds thus play a fundamental part in the genesis and the spatial distribution of natural resources, and they are important hosts of hydrocarbon accumulations and deposits of metalliferous minerals worldwide."
The Permo - Triassic red beds of the UK host: major oil and gas reservoirs.
"Finally, the prospectivity of the Cheshire Basin and comparable settings elsewhere in the UK for red-bed Cu deposits and other types of mineralisation potentially associated with Permo - Triassic rifted basins are discussed."
"The mineralisation comprises disseminated cement and fracture-hosted baryte and more localised polymetallic mineralisation, hosted in formations of the SSG."
Baryte is particularly widespread near the base of the Helsby Sandstone Formation and in the upper part of the Wilmslow Sandstone Formation around the basin margins.
"The mineralisation occurs mainly in the upper part of the SSG where it is faulted against, or capped by, the now relatively impermeable argillaceous rocks of the overlying MMG."
"At Alderley Edge the mineralisation occurs in SSG rocks dipping south-west at 10 to 15¬ ∞, in faulted contact with younger formations of the MMG across the Kirkleyditch Fault in the east, and the Alderley Fault in the west."
"The MMG formerly capped the sandstone, constraining fluid movement and forming a potential trap for hydrocarbons and ore fluids."
"Widespread Cu mineralisation with Pb and Zn occurs adjacent to fault zones in both fluvial and aeolian sandstones of the uppermost Wilmslow Sandstone Formation and the Engine Vein Conglomerate, Wood Mine Conglomerate and West Mine Sandstone in the Helsby Sandstone Formation."
"The eastern group, comprising the Engine Vein Mine and Stormy Point workings, in the uppermost Wilmslow Sandstone Formation and basal Helsby Sandstone Formation."
The fault at the northern margin of Wood Mine is the western extension of the fault which cuts the lower Helsby Sandstone Formation and the Wilmslow Sandstone Formation in Engine Vein Mine.
The ore body is in the upper 10m of the Grinshill Sandstone Formation immediately below the Tarporley Siltstone Formation and extends about 250m along the fault and up to 8m downdip into the hanging wall.
The Mottram St Andrew site immediately east of the Alderley block is adjacent to the Kirkleyditch Fault where the Helsby Sandstone Formation is thrown down east against the older Wilmslow Sandstone Formation.
"At Bickerton in the west of the basin, mineralisation is associated with a north-east-trending normal fault which downthrows the MMG east against the SSG: the mineralisation is hosted by the Wilmslow Sandstone Formation in the footwall."
"At Eardiston in the south-west of the Cheshire Basin, a north-north-east-trending normal fault downthrows east-dipping MMG beds west against the upper SSG."
"MMG deposits overlying the SSG east of the main fault, and those in the hanging wall, created a trap for migrating fluids."
"The Pim Hill site is on a north‚ $ `` south fault to the west of a small graben, where the Tarporley Siltstone Formation and underlying Grinshill Sandstone Formation are downthrown east against the Wilmslow Sandstone Formation."
"The geology of the Yorton site, which is also on a north‚ $ `` south fault which downthrows MMG beds east against the SSG, is similar."
"At Wixhill, mineralisation is associated with a north-east-trending normal fault, which downthrows the Bollin Mudstone Formation north-west against the Wilmslow Sandstone Formation."
The mineralisation is likely to be in the fault and in the Wilmslow Sandstone Formation in the footwall.
"Common features of the polymetallic mineralisation in the Cheshire Basin are as follows: The deposits are hosted in formations of the SSG, usually the Helsby Sandstone Formation but sometimes the Wilmslow Sandstone Formation, in stratigraphical or structural proximity to the MMG in either the footwall or hangingwall of faults."
"The MMG appears to have formed the main aquiclude, but mudstone beds in the Helsby Sandstone Formation are also important locally."
"Early workers, including Hull, favoured a syngenetic origin, with detrital Pb and Cu sulphides deposited contemporaneously with the Helsby Sandstone Formation host rocks."
Subsequently Taylor et al. moving up the faults: Warrington suggesting that a concealed Jurassic granite was the source of ore fluids.
Holmes et al. proposed a diagenetic origin for the mineralising fluids and suggested that the ore solutions were oxidising basinal brines of moderate salinity with trace metals released during diagenesis of the Permo - Triassic sediments within the basin.
"A basin brine expulsion model was also favoured by Naylor et al., with precipitation as a result of interaction with methane from the underlying Coal Measures."
"In contrast, Thompson suggested that the metals may have originated in the black shales of the underlying Coal Measures."
"Prior to erosion, the Tarporley Siltstone Formation provided a regional seal, indicating that the predominant direction of ore-forming fluids was up basin-margin fault systems."
"At present, the evaporite-bearing MMG lies topographically below the mineralised horizons in the SSG."
"Naylor et al. used this evidence, together with sulphur-isotope data for the baryte mineralisation which is consistent with an evaporitic source in the MMG, to suggest that mineralisation occurred during and after Tertiary inversion of the basin when sulphate-bearing fluids rose through the fault systems."
"Most authors now propose ore deposition beneath the MMG, involving reductants such as hydrocarbon gases."
The possibility that ore deposition might be due to migration of hydrocarbons was first suggested by Warrington postulated that methane derived from the underlying Coal Measures was the reductant.
"Red beds are important as a source of heavy metals, and their high mean porosity and permeability enable them to act as conduits for fluid flow during basin evolution and to become reservoirs for mineralising fluids, hydrocarbons or groundwater."
"In the type localities in Poland and Germany, Kupferschiefer mineralisation is at the contact between Lower Permian volcanics and red beds and Upper Permian marine carbonates and evaporites."
"Petrographical studies of the SSG have shown that these sandstones contained ferromagnesian minerals at the time of deposition, and it is not unreasonable to suppose that the levels of OFEs in the sediments were in the normal ranges for sandstones."
"Most of the detrital matter that formed the MMG was already oxidised at the time of deposition, with OFEs associated with ferric oxides and oxyhydroxides, and OFE levels may also have been in the normal ranges for organic-free argillaceous rocks."
"The total volume of MMG and SSG strata preserved in the basin is estimated, from the interpreted seismic reflection data, as 1300km3 and 3100km3 respectively."
"Making an allowance for erosion, the original depositional volume of the SSG was probably of the order of 3300km3."
The ratio of preserved MMG / SSG thicknesses then gives an original depositional volume of about 2000km3 for the MMG.
"If the basin fill originally contained average upper-continental-crust levels of metals, then 173 Mt of Cu, 84 Mt of Pb and 481 Mt of Zn has been leached from the SSG and 60Mt of Cu, 63 Mt of Pb and 84 Mt of Zn from the MMG."
"However, if the original contents of OFEs in the SSG were at average sandstone levels, then only 30‚ $ `` 150 Mt of Cu, 8Mt of Pb and 132‚ $ `` 326Mt of Zn would have been available."
"The lower values of OFEs in the SSG at present might reflect preferential removal of Cu and Zn by fluids passing through the basin, with greater volumes flowing through the more porous and permeable SSG than moving through the finer-grained MMG."
"Early diagenesis in the SSG involved the breakdown of detrital ferromagnesian minerals and the reprecipitation of Fe in ferric oxyhydroxides, followed by infiltration of detrital clay into sandstones and the deposition of low-ferroan dolocretes and calcretes in conditions of high pH and Eh."
"Sulphur-isotope data suggest that sulphate was derived mainly from brines of Triassic marine origin, although higher in the sequence sulphate is isotopically lighter, possibly reflecting an increased continental component or derivation from Permian sources."
"During the late phases of eodiagenesis, reduction by bacteria of Fe3 + and SO42‚ $ `` led to the production of reduced green beds and reduction spots with authigenic pyrite in fine-grained fluvial - cycle sediments and with corrensite deposition in hypersaline sections of the MMG."
"During earlier phases of SSG mesodiagenesis, early carbonate cements together with silica were remobilised."
"Evidence in the MMG is consistent with early diagenetic dissolution of halite, prior to the development of early mesodiagenetic dolomite."
It is suggested that much of the SSG was cemented by anhydrite.
"All the evidence suggests that chloride and sulphate cements and vein mineralisation in the Cheshire Basin fill were derived by fluxes of fluid from the MMG into the SSG, initially as a result of compaction and gravity - driven brine circulation."
"Diagenetic evidence is consistent with early anhydrite-saturated fluids fluxing through the SSG, followed by later low-sulphate NaCl brines derived from the MMG."
The MMG thus appears to have generated different fluids at different times.
"The new evidence presented here indicates that mineralisation in the known sulphide ore deposits occurred when high-density metalliferous brines from the MMG fluxed through the basin under the influence of gravity and encountered a small volume of reducing fluid in fault systems around the margins of the basin, especially in the north."
"Some of the OFE contents of the fluids could have been picked up during their passage through the SSG, and some may have been introduced with the deeper, reducing fluids."
"The extent to which the reducing fluid was derived from the East Irish Sea Basin to the north-west or the Coal Measures sequences beneath the northern Cheshire Basin is unclear, but structural considerations favour the latter source."
"There is no direct evidence for the migration of hydrocarbons into the SSG before or during base-metal mineralisation, so models favouring the involvement of light hydrocarbon gases remain unproven."
"Complex interaction occurred between an ore fluid sourced in the MMG, transporting and mobilising OFEs as it flowed down and outwards towards the basin margin fault systems, and small components of a reducing phase, possibly derived by thermobaric dewatering and organic maturation in deep Carboniferous basins, migrating in relation to fault movement and seismic pumping."
"Regional considerations, particularly evidence from more fully preserved sedimentary sequences to the south of the basin, indicate that extensional basin subsidence continued to early Jurassic times with renewed extension in the late Jurassic and early Cretaceous associated with sea-floor spreading in the southern part of the North Atlantic region."
It seems most likely that the known mineralisation in the Cheshire Basin occurred at some time during the late Triassic to early Jurassic period of extension.
Such a model has considerable implications for Cu exploration in the Cheshire Basin and in other Permo - Triassic basins in the UK.
"Evidence for the extraction of large quantities of metals from the Cheshire Basin fill by the migration of pervasive high-density brines, variously enriched in sulphate and chloride as a result of interaction with evaporitic phases especially in the MMG, has considerable implications for exploration for SCDs in the Cheshire Basin and elsewhere."
This is particularly the case if mineralisation occurred during the late Triassic to early Jurassic period of crustal extension or subsequently.
"The MMG appears to have acted as a major source of ligands and metals for the known ore deposits, as well as being the dominant control on ore-fluid migration, and there is thought to be the potential for the discovery of further small-tonnage high-grade Cu deposits beneath the MMG."
"In the south-west of the basin, the lack of Westphalian rocks in the basement, which are thought to have been the source of the reducing phase involved in ore deposition, may also limit the potential for continental red-bed-type Cu deposits."
Some of the evidence presented here suggests that Cu mineralisation occurred in the Cheshire Basin during the late Triassic to early Jurassic phase of crustal extension.
"The Blue Anchor Formation, Penarth Group and Lias Group of the Prees outlier in the south-east of the basin, and rocks of similar age elsewhere in central and southern Britain, comprise dark mudstones and limestones which could have provided a reducing horizon capable of precipitating sulphide minerals from ore solutions originating in the red-beds beneath."
"Hence, if ore formation occurred following deposition of the Lower Jurassic, more extensive SCD deposits of Kupferschiefer, rather than continental-red-bed type, may have formed near the top of the red-bed sequence."
"In the Cheshire Basin the Blue Anchor Formation, Penarth Group and Lias Group rocks were largely eroded during the Tertiary."
"Elsewhere, however, they are present from north-east England to Devon in the south-west, overlying red beds of the MMG."
Numerous minor occurrences of epigenetic Cu occur in the Permo - Triassic areas of England.
"At Middleton Tyas, secondarily enriched Cu ores occur in Carboniferous host rocks."
The Lower Permian Marl Slate of north-east England is the lateral equivalent of the Kupferschiefer.
Mineralisation offers a possible explanation for a zone of anomalous values for Cu and other elements in stream sediments extending over Permo - Triassic rocks from Teesside to York is similar to that of the Cheshire Basin.
Hence it is considered that there may be the potential for the discovery of significant SCDs in the Permo - Triassic rocks on and offshore of the UK where they are overlain by reducing marine sequences.
"The greatest potential for such deposits would be at sites where oxidising hydrothermal brines circulating in the basin have encountered reducing conditions, for example near to the contact between the red beds and the Coal Measures in the north of the basin."
"BGS regional geochemical data show Cu anomalies close to the contact between the Permo - Triassic and the underlying Westphalian immediately to the south-east of the Cheshire Basin, in the adjoining Stafford Basin."
"Boulder clay is extracted for brickmaking near Warrington, and the SSG is worked for construction fill near Warrington and as a building stone at Grinshill."
A large group of shallow mines was sunk nearby in the ‚ $ òTop‚ $ ô and ‚ $ òBottom‚ $ ô beds of the Northwich Halite.
"The main centres of wild brine extraction were at Winsford and Northwich, sited on the Northwich Halite."
"Wild brine was also formerly extracted from the Northwich Halite in the Heatley‚ $ `` Agden Saltfield near Lymm, and at Lawton -LSB- 8050 5727 -RSB-."
"Extensive brining was formerly undertaken in the lower part of the Wilkesley Halite, near Sandbach, Elworth and Middlewich."
"The only wild brine currently produced is at New Cheshire salt works at Wincham, near Northwich, from the lower part of the Northwich Halite."
"All the brine comes from the Northwich Halite Formation and is from cavities some 100m across and up to 170m in height formed by a triple tube system involving water, compressed air and a brine outlet."
"Both sites are under a cover of Byley Mudstones, overlying the halite."
Mining is currently all in the ‚ $ òBottom Bed‚ $ ô of the Northwich Halite in galleries 7.5m in height.
"The future resources are vast, notably in the virtually untapped area of the Prees Syncline where both the Northwich and Wilkesley halites are present."
"This area includes a probable eastern extension of the Wilkesley Halite outcrop towards Betley, near Stoke-on-Trent, with the likelihood there of Northwich Halite at depth."
"Most of the analytical work on the project concentrated on the Permo - Triassic rocks, since the primary aim was to provide a metallogenic model for the Cu-Pb-Ba mineralisation."
The prospectivity of the Carboniferous rocks is based on work done over a number of years on the Pennine Basin.
"Because there is a dearth of organic matter within the Permo - Triassic red beds, samples had to be collected outside the Cheshire Basin, from Carboniferous rocks."
All share the fundamental property that hydrocarbons were generated from Carboniferous rocks.
"As described earlier in this volume, the Cheshire Basin contains Permo - Triassic red beds."
Red beds are important hydrocarbon reservoirs in many parts of the world.
"In the UK, Permo - Triassic rocks are important hydrocarbon reservoirs in the North Sea, Wessex and East Irish Sea basins."
"Carboniferous rocks provide important oil and gas-prone source rocks in the East Irish Sea, southern North Sea, East Midlands and Europe generally, and provide reservoirs in the East Midlands."
"Carboniferous reservoirs are not proven in the Cheshire Basin, however, and there are no mature Permo - Triassic or younger source rocks in that area or in the East Midlands."
"Producing fields from Triassic reservoirs in basins adjacent to Cheshire, at Formby and in the East Irish Sea, together with oil shows in the Needwood Basin prove that oil and gas have been generated and have migrated, even into Recent sedimentary deposits."
"In the East Irish Sea Basin the reservoir for all the hydrocarbons is the Ormskirk Sandstone Formation, sealed by MMG halites and mudstones."
"The older sandstones of the SSG and the Collyhurst Sandstone are not productive, despite the latter being sealed by the Manchester Marls."
"The key to the hydrocarbon prospectivity lies in resolving whether migration from the Carboniferous source rocks into Permo - Triassic rocks has occurred, or the extent to which hydrocarbons are trapped within Carboniferous rocks."
"There are only about a dozen recorded hydrocarbon shows in Permo - Triassic rocks of the Cheshire Basin sensu stricto, and none of these contains live oil."
"There are, however, limited developments of oil sands in the Triassic of the nearby Needwood Basin and commercial oil and gas production from Permo - Triassic rocks of the East Irish Sea Basin."
"In addition, the Formby Oilfield produced from a Pleistocene sand in one well and from Triassic rocks in the other wells."
"In contrast, hydrocarbon shows in Carboniferous rocks surrounding the Cheshire Basin and beneath the Permo - Triassic rocks are commonplace and include live oil."
"The Mere Brow Borehole encountered bitumen in the Collyhurst Sandstone, and minor hydrocarbon traces are reported in the Mickle Trafford Borehole, and at the Grinshill and Alderley Edge copper mines in the Cheshire Basin."
"Their presence may be related to nearby large faults, in the case of the Mickle Trafford and Little Ness boreholes, and the close proximity to the main area of Carboniferous subsurface shows in the north of the basin for most of the others."
"Ickes reported obtaining 2.50% petroleum by the use of solvents, with Carboniferous oil characteristics."
"A Carboniferous source and mother pool were suspected but not found, despite drilling five deep boreholes."
Interpretation of seismic reflection data shows that Dinantian rocks form the subcrop stretching north-east from the seeps.
"Several north‚ $ `` south Permo - Triassic faults have tapped the migrating oil and, with a very thin MMG seal, seepage to the surface has occurred."
"This oilfield should be considered as the first discovery in the East Irish Sea Basin and highlights how the interplay between Carboniferous source-rock maturity, Triassic reservoirs, seals and faulting may be the key to further successes."
"Carboniferous rocks in all the coalfields surrounding the Cheshire Basin have fair to good shows of hydrocarbons, with live oil, and are comparable in this respect to the Nottinghamshire‚ $ `` Yorkshire Coalfield."
The oil has migrated to the extremity of the Carboniferous basin.
"In Cheshire, weak hydrocarbon shows were recorded in the Blacon East Borehole, in Namurian sandstones."
"The Churton Borehole, in the Milton Green Inlier, had oil shows in the Erbistock and Coed-yr-Allt formations, suggesting that the Ruabon Marl seal is breached in the Inlier."
"Some of the shows are in the red beds, but most are in the Productive Coal Measures sandstones."
"Philips Bridge Borehole, south of Stockport, had an oil show in Westphalian A rocks."
"In Clwyd, Redwood reported oil in water wells at Rosehill and Erbistock Lodge, about a kilometre apart, and the borehole at Overton Bridge had oil shows in the Coed-yr-Allt and Ruabon Marl formations."
"These seeps may result from this area being a Westphalian palaeo-high, towards which migration could have occurred over a long period of time."
Cronton A3/5 Borehole penetrated a 3m oil sand in the Upper Coal Measures.
"Numerous other nearby localities also experienced seepages, indicating that migration into the Westphalian D Coalport Formation sandstones had occurred over a considerable distance."
"Selley, in a cross-section, showed the relationship of some of the seeps to the basal Westphalian unconformity."
"In Staffordshire, oil-stained Namurian rocks were found where the Red Rock Fault crosses the river Dane and at Dingle Brook near Bosley in Arnsbergian mudstones."
"Nearly all the early exploration wells drilled to appraise these shows were drilled north-east of the Coalfield, at Werrington, Gun Hill and Nooks Farm, on large surface anticlines, spudded into Namurian rocks."
Nooks Farm Borehole encountered sub-economic gas in the latest Dinantian Onecote Sandstone.
"Potential hydrocarbon source rocks include Dinantian, all of which outcrop on the periphery of the Cheshire Basin."
They are well-known source rocks in other oil provinces: early Namurian shales.
"The Formby Oilfield overlies Bowland Shales, which subcrop beneath Permian rocks."
"These Westphalian source rocks can reasonably be expected to underlie the Cheshire Basin between the North Staffordshire, Lancashire and North Wales coalfields."
The latter may have migrated south-west towards the margin of the Carboniferous basin.
"Precambrian samples were from the Shrewsbury area, where oil from the basal Westphalian has seeped into the underlying Longmyndian rocks."
The Coalport Tar Tunnel sample is from Westphalian rocks a short distance above Silurian rocks.
"The Snailbeach Pb mine yielded bitumen from veins, thought to be Triassic in age, in Ordovician rocks."
"Five of the Triassic samples are from within the Cheshire Basin, Burton Point being adjacent to the East Irish Sea Basin."
The sample from well 110/7 -2 is a show in the Permian Collyhurst Sandstone.
The Ecton sample is from Dinantian rocks at the Waterbank Mine dumps.
The River Dane sample is from Triassic rocks close to the show recorded by Evans et al..
"The five most biodegraded samples, without recognisable alkane patterns, are from the Westphalian and pre - Westphalian rocks in the Shrewsbury area."
"These data support the results of the carbon isotope composition of the late carbonate cement, indicating an influx of fluids from mature Carboniferous rocks."
"A different source, within the Coal Measures, is indicated by the high Pri/Phy ratios of the Hem Heath, Little Ness and River Dane samples."
"The present-day geothermal gradient in the basin is low, at about 20¬ ∞ C/km, and there is no evidence for significantly higher values in Permian to Tertiary times."
"Thermal modelling of the basin using the BGS HotPot software suggests that the basin is relatively cool, with mean temperatures ranging from 20¬ ∞ C at the base of the MMG to 37¬ ∞ C at the base of the Permo - Triassic."
"The highest temperatures at the base of the Permo - Triassic succession, in the deeper parts of the basin, locally exceed 70¬ ∞ C in parts of the Wem ‚ $ `` Audlem Sub-basin and 65¬ ∞ C in the Sandbach‚ $ `` Knutsford Sub-basin."
There is some evidence from the East Irish Sea Basin that geothermal gradients were significantly higher in Carboniferous times.
Roberts is lower than that in the Carboniferous rocks of well 112/30 -1.
"In addition, there is a downhole variation in maturity from low gradients in post - Carboniferous rocks to high gradients in Carboniferous rocks in well 110/11 -1."
This may result from a geothermal gradient which was significantly higher during the Carboniferous.
The total preserved thickness of the Carboniferous in the Quadrant 109 Syncline in the East Irish Sea was estimated at 6250m by Jackson et al..
"Coal rank data from the Keele 1 Borehole in the North Staffordshire Coalfield suggest that there may also have been variations in the geothermal gradient during the Carboniferous, with higher gradients in the early Westphalian than in late Westphalian times."
"A depth-maturity plot of Keele 1 reveals by calculation that the geothermal gradient may have been as high as 81¬ ∞ C/km in early Westphalian times, declining to 29‚ $ `` 45¬ ∞ C/km in late Westphalian times."
"The heat flow is therefore also thought to have been higher in early Westphalian times, as the thermal conductivities of the Westphalian rocks are relatively constant."
"Westphalian D rocks in Knutsford are significantly more mature than the highest Westphalian rocks in Keele 1, just leaving the oil window."
"If a similar amount of uplift has been experienced by both sites, this implies a geothermal gradient of approximately 34¬ ∞ C/km since Permian times, somewhat higher than at present."
"If, however, the geothermal gradient has been approximately constant at its present level since Permian times, differences in the amount of Variscan uplift would be suggested."
"Evidence for lateral variations in geothermal gradients comes from coal rank maturity data from North Staffordshire, which suggest that palaeogeothermal gradients during Westphalian times were higher in this area than in the Lancashire and East Midlands coalfields, perhaps due to its closer proximity to Westphalian volcanism."
"Carboniferous source rocks in this region have undergone two phases of burial, firstly during Carboniferous basin formation and secondly during Permo - Triassic and later burial."
Thermal modelling of the Permo - Triassic fill of the Cheshire Basin suggests that maximum temperatures were attained during the period of maximum burial in Palaeocene times.
"Severe reductions in average porosities of Permo - Triassic sandstones, resulting from this burial, are likely towards the basin centre."
"Average temperatures at the base of the Permo - Triassic were 95¬ ∞ C, with peak temperatures in the deepest part of the basin of 140¬ ∞ C."
The lower part of the Permian sequence entered the oil-maturation window towards the end of the Triassic and left it during late Palaeogene uplift.
"Peak maturity was reached in early Palaeogene times, corresponding to the maximum depth of burial."
"Much of the Permian sequence was in the oil-maturation zone at this time, with some parts being at temperatures almost high enough for gas maturation."
"The base of the SSG was in the oil-generating window from early Jurassic to mid or late Palaeogene times, and the base of the MMG from late Jurassic to mid Palaeogene times."
"Modelling of underlying Carboniferous rocks is more problematical, as their maturity at the end of Carboniferous basin development is difficult to estimate."
"Carboniferous strata generally possess a maturity, due to Carboniferous burial and Variscan tectonics, which is markedly higher than post - Carboniferous rocks."
"Even if this observation is disregarded, the Carboniferous rocks would have become mature earlier than Permo - Triassic strata because of their greater depth."
"They probably reached the oil window in mid to late Triassic times, and they remained in the oil-generation zone for longer than post - Carboniferous rocks, probably until early Neogene times."
"They would also have attained higher levels of maturity, well into the gas-generating window, at maximum depth of burial in early Palaeogene times."
"Hydrocarbon generation is therefore thought to have begun during Carboniferous times, from source rocks in the Pennine Basin depocentre which lay to the north of the area now occupied by the Cheshire Basin."
"It is likely that some of these hydrocarbons migrated south-westwards, away from the Pennine depocentre, towards the margins of the Carboniferous basin, into the area now underlying the Cheshire Basin."
"As subsidence of the Permo - Triassic Cheshire Basin proceeded it is likely that the underlying Carboniferous sediments, hitherto immature, also started to generate hydrocarbons."
"Deep saline fluids, in the Collyhurst Sandstone and in the Coal Measures, have been recorded from geophysical log interpretation, from samples from a deep borehole near Chester, and from a 11000mg/l saline spring at Aldersey."
"Fresh water was recovered by drill stem test from the Coed-yr-Allt Formation, in the Milton Green Borehole."
Saline water was recovered from Dinantian rocks in the same borehole.
"Springs with higher than average temperatures are geographically associated with hydrocarbon shows in the South Pennine Orefield, and the Ridgeway Borehole, near Sheffield, encountered hot salt water with hydrogen sulphide in Dinantian rocks."
"Downing and Howitt showed that saline concentrations in Namurian and Westphalian groundwaters, in the East Midlands oilfields, increased northwards towards the basin depocentre."
"During Carboniferous times, it is likely that hydrocarbons migrated south-westwards away from the Pennine Basin depocentre towards its margin, to the area now underlying the Cheshire Basin."
"Late Carboniferous structural inversion of the Pennine Basin would have caused some hydrocarbons to migrate north-eastwards, away from the Cheshire Basin area, but erosion of potential reservoirs, in the Pennines, has destroyed any such hydrocarbons."
"Migration of hydrocarbons since Carboniferous times may also have been largely within Carboniferous rocks, if the seals were not breached."
"Permo - Triassic syn-sedimentary faulting is, however, likely to have modified migration directions."
"The most prospective area for this oil is undoubtedly to the south-east of the inlier, because there is probably no seal to the Carboniferous at outcrop."
"Hydrocarbon shows were present in the Carboniferous red beds in the Churton Borehole, drilled in the Milton Green Inlier."
"Madeley 1 and 3, to the north, have a more complete Westphalian succession, which thickens northwards."
"The Symon Unconformity, in contrast, cuts down into the earlier Westphalian rocks, removing most of the Westphalian B from Madeley 6 and all the Productive Coal Measures from Madeley 4, where the red beds come to rest on Wenlock Shale."
"Oil generated from the coals of the North Staffordshire Coalfield and its subsurface extension could have migrated toward the basin margin, within the thinning Productive Coal Measures."
"Evidence of migration of hydrocarbons into Permo - Triassic rocks, in addition to the few, poor hydrocarbon traces, comes mainly from isotope studies."
This suggests fluid migration from Carboniferous to Permo - Triassic rocks at the southern margin of the Lancashire Coalfield and the West Lancashire Basin.
"The migration pathways for fluids derived from the Carboniferous were probably not the main north‚ $ `` south-trending, inclined normal faults, with large displacements, which are probably sealing."
"Subvertical, east‚ $ `` west transfer faults may, however, have formed pathways for upward migration of fluids from Carboniferous rocks."
"Hydraulic connectivity between the Carboniferous and Permo - Triassic rocks is suggested by the chemistry of a single groundwater sample from the Coal Measures, but there are no other data to substantiate this interpretation."
"Fluid-inclusion studies found no evidence of migration of hydrocarbons into the SSG of the Cheshire Basin, either before or during base-metal mineralisation."
"Low-temperature fluids were responsible for the mineralisation, and the model favoured requires a Carboniferous fluid component probably comprising no more than 5% of the total fluid budget."
The small number of hydrocarbon shows in post - Carboniferous rocks invites comparison with the East Midlands.
"Although generation of hydrocarbons here also continued during Permian and Mesozoic times, there was no significant hydrocarbon migration into post - Carboniferous rocks."
"It is possible that, at the margins of the Cheshire Basin, hydrocarbons could have migrated into Permo - Triassic rocks."
"The Needwood Basin, however, has a much thinner Permo - Triassic cover than Cheshire, and it would be easier for hydrocarbons to migrate vertically there."
"Potential reservoirs are, from the top downwards: the Helsby Sandstone, Wilmslow Sandstone and Kinnerton Sandstone formations of the SSG: the Collyhurst Sandstone Formation: and Westphalian and Namurian sandstones."
"Many of the Silesian sandstones encountered in the Milton Green and Blacon East boreholes are thin, but thicker equivalents were found in the Erbistock Borehole."
"Many of the Permo - Triassic sandstones have considerable secondary porosity due to dissolution of early diagenetic cements of non-ferroan dolomite, anhydrite and possibly halite and unstable framework grains."
This is a typical feature of other UK Permo - Triassic basins.
"In the upper part of the Collyhurst Sandstone porosities were 10‚ $ `` 15% and permeabilities up to 20mD, but in the lower part they reached above 25% and up to 1800 mD respectively."
"In the Chester Pebble Beds the porosity in cemented parts was 14%, combined with low permeability, in contrast to the coarse clean sands with porosities of 22% and permeabilities of up to 2500mD, which were probably not representative of subsurface properties."
In the Wilmslow Sandstone geophysical logs gave an average of 13% porosity.
"A decrease in porosity with depth is seen clearly in the sonic logs of the Knutsford and Prees boreholes, below the top Silicified Zone, reaching a minimum within the Chester Pebble Beds."
Below the Chester Pebble Beds and the base of the St Bees Sandstone.
"Changes in porosity in the upper part of the SSG, showing no systematic downhole increase, are attributed to facies control."
The fluvial Delamere Member has a higher sonic velocity than the Frodsham and Thurstaston members.
"Modelling of the burial history of this basin suggests that compaction-induced porosity reduction is likely to have occurred towards the centre of the basin, reducing average porosities at the base of the SSG to between 5 and 7%."
This is the result of Jurassic and Cretaceous burial.
Porosity reduction has not occurred in the Permian sandstones of the Prees and Knutsford boreholes.
"A downhole porosity reduction within the Permian sandstones is apparent in the Collyhurst Sandstone of the Prees Borehole, but the overlying Kinnerton Sandstone Formation has a lower porosity."
"The Collyhurst Sandstone, in the Knutsford Borehole, shows more variable and higher porosity."
"In the East Midlands oilfields, Coal Measures sandstones, which produce oil, have porosities of about 7‚ $ `` 20%, with an average value of 12%."
"Upper Coal Measures sandstones, which are not productive, have higher porosities, 12‚ $ `` 19%."
"Permeabilities range from 0.06 to 37mD, locally 400mD for the Productive Coal Measures and 2 to 160mD for the Upper Coal Measures sandstones."
In the Bothamsall Oilfield Hawkins found porosities of 3‚ $ `` 12% in coarser grained channel sandstones of Westphalian A age.
"Reddening of Coal Measures sandstones, in contrast to mudstones, has occurred during Permian and Triassic times in the Potteries Coalfield, indicating some porosity and permeability of the sandstones."
"A northerly decrease in porosity and permeability has been noted in the East Midlands oilfields, which is interpreted as a Carboniferous burial effect."
"The MMG halites and mudstones are excellent seals, where sufficiently thick."
"At Formby, however, there is no salt and the MMG is thin, resulting in a very leaky oilfield."
There are no other significant mudstone beds within the Triassic succession.
"The Manchester Marls can be considered a reasonable seal where there is mudstone and, to the north-west, halite, but this formation becomes sandy in the south and west of the Cheshire Basin."
"It may be deduced, therefore, that Carboniferous shales are adequate to seal the hydrocarbons beneath the Variscan Unconformity, particularly where Ruabon Marl is present."
The active tectonics of Permo - Triassic times in the Cheshire Basin contrast with the relatively steady accumulation of sediments on the gently shelving margin to the southern North Sea Basin in the East Midlands.
The East Midlands and the Cheshire Basin are alike in appearing to have few hydrocarbon accumulations in Permian and later rocks.
"However, there are numerous oilfields in Carboniferous rocks of the East Midlands whereas, to date, there have been no commercial discoveries in the Carboniferous rocks surrounding the Cheshire Basin."
"These oilfields have certain common characteristics: the reservoirs are mainly late Namurian and Westphalian A sandstones, and are sealed below post - Permian rocks."
"This spectacular lack of success, west of the Pennines, may be because by far the largest percentage of wells drilled in the west of the Pennine Basin have spudded into large structures at stratigraphic levels below the reservoirs producing in the East Midlands and only a few wells have seals below post - Permian rocks."
"Parnell has tabulated the metal enrichment of bitumens in Carboniferous - hosted ore deposits, indicating that there are a number of close associations between ores and hydrocarbons in Carboniferous rocks."
"St George‚ $ ô s Land formed the southern margin of the Carboniferous Pennine Basin: in the East Midlands, Westphalian rocks overlap regressive Namurian rocks along a north-east-trending line onto this former landmass."
The Welton Oilfield was discovered where the basal Westphalian sandstones rest unconformably on Dinantian rocks.
"Near the southern margin of the Potteries Coalfield and beneath the south-east Cheshire Basin a similar stratigraphical situation may exist, with thinning of the Namurian rocks beneath the Potteries Coalfield."
"The principal difference between the Cheshire and East Irish Sea basins is the presence of hydrocarbons in the Ormskirk Sandstone Formation of the East Irish Sea Basin and their apparent absence in its correlative, the Helsby Sandstone Formation, in the Cheshire Basin."
"The main Carboniferous rift is orientated east‚ $ `` west, through the southern North Sea, beneath the Cleveland, Craven and East Irish Sea basins towards Ireland."
The Cheshire Basin is more peripheral to the Carboniferous Pennine Basin than the East Irish Sea Basin and is therefore thought less likely to be underlain by good oil-prone source rocks at depth.
"There are a few positive indications, however, such as oil shale in the Heswall Borehole, and also the unproved possibility that Dinantian basins may have locally rich oil-prone source rocks."
Beneath the East Irish Sea Basin much of the subcrop consists of Namurian rocks.
"This long delay can be attributed to a lack of interest in the Carboniferous source rocks: even with the recent discoveries, there is a reluctance to extend the play, by exploration of Carboniferous rocks."
"Significant oil was generated during Jurassic times, but gas generation required burial deeper than 4000m according to Hardman et al.."
The amount of Tertiary uplift is estimated by various methods to be over 2000m.
The SSG has many similar reservoir characteristics in the Cheshire Basin.
"Porosities of up to 21% and permeabilities of up to 400mD are reported for the Morecambe Gasfield, in beds probably equivalent to the Frodsham Member of the Helsby Sandstone."
At the Douglas Oilfield the Frodsham Member has a porosity of 17% and the Delamere Member 12%.
Coal Measures are present beneath almost all of the Cheshire Basin.
"The main conclusion is that hydrocarbons generated from Carboniferous times to the present day are likely to be trapped beneath the base Permian unconformity, by Ruabon Marl seals, and that drilling to test late Namurian to early Westphalian reservoirs, although deeper than present exploration, can be justified."
Wells sited on the crop of early Namurian and older rocks are not recommended because these rocks have unfavourable reservoir characteristics.
"These conclusions are at variance with those of Fraser et al., who presented a pessimistic view of Carboniferous basins outside the East Midlands, which contributed partly to the evacuation of the area by the major oil companies."
"Two key questions, relevant to the hydrocarbon prospectivity of the Cheshire Basin, are: Why have no Carboniferous oilfields been discovered in north-west England comparable to those in the East Midlands ? Why is the Ormskirk Sandstone Formation of the East Irish Sea Basin productive of hydrocarbons whereas no discoveries have been made in its correlative Helsby Sandstone Formation in the Cheshire Basin ? Fraser et al. identified factors which are crucial to the prospectivity of Carboniferous basins in northern England."
"Carboniferous rocks in Knutsford lie near the oil floor at 3000m, but have probably been uplifted from below 4500m in Tertiary times."
"Coal-rank data indicate that present-day geothermal gradients, and possibly Carboniferous gradients, are lower in the Lancashire Coalfield than in the North Staffordshire and Nottingham‚ $ `` Yorkshire coalfields."
It is possible that Namurian pro-delta shales exist beneath the Cheshire Basin.
Connections between the Widmerpool ‚ $ `` Staffordshire Dinantian Basin and south Lancashire were suggested by Collinson et al. and are tentatively in agreement with seismic reflection interpretation of the Carboniferous succession in parts of the northern Cheshire Basin.
"Early Namurian sedimentation may, therefore, have led to the formation of rich source rocks."
"The Formby Oilfield is an example of the probable breaching of an accumulation in Carboniferous rocks, with migration of oil into Triassic and Recent sediments."
"Structures can be mapped in Carboniferous rocks beneath the Permo - Triassic in some places, but additional seismic reflection data would be required in some areas prior to drilling."
"Westphalian reservoirs, beneath the level drilled at Knutsford, lie just below the oil floor."
Oil-prone Namurian and Dinantian shales are probably present in the subsurface.
Gas-prone Westphalian coals are present within a southerly thinning succession into which migration of hydrocarbons is thought to have occurred.
Failure to find encouraging hydrocarbon shows in post - Carboniferous rocks and subsequent dry commercial wells within the basin are seen as evidence that the hydrocarbons may be securely trapped in the Carboniferous rocks.
"Modification of migration pathways by Permo - Triassic tectonism is obviously greater and more complex than in the East Midlands, but this should not be a deterrent to exploration."
"If hydrocarbons are securely trapped within the Carboniferous rocks, it is possible that overpressuring has occurred."
"Overpressuring is a characteristic of the deepest sedimentary basins such as the Anadarko Basin, USA, where the main overpressured zone, in several compartments, encompasses Devonian and Carboniferous rocks from 3 to 7km deep."
"Although it is not the primary target, testing of the Helsby Sandstone should not be ignored."
The mineralisation model requires a contribution from Carboniferous fluids.
Structural leads can be identified by combining the contour maps of the top SSG with the outcrop of the Helsby Sandstone Formation.
"These are the known occurrences of Cu, which, according to the mineralisation model, require a Carboniferous fluid component."
"A MMG seal is present, although it is not thick and does not contain halite."
A nearby outcrop contains Cu mineralisation in the Helsby Sandstone.
The top Helsby Sandstone is at very shallow depth hereabouts.
Between the Helsby Sandstone outcrop at Bickerton and the Wem ‚ $ `` Audlem Sub-basinHydrocarbon migration up the tilt-block towards Milton Green may have occurred and sealing by a MMG succession with halite is assured.
The seal by the MMG is good.
Alderley Edge Cu mines are situated on the Helsby Sandstone outcrop to the north-east.
A MMG seal is present and there are good shows to the north in Westphalian rocks in the subsurface and at outcrop.
This play depends on the presence of the Manchester Marls seal.
Halite is widely present in the Manchester Marls in the East Irish Sea Basin.
The main area of Carboniferous exploration targets is related to the south - and west-thinning Silesian rocks.
"The Westphalian rocks are thinner here than to the east, towards Manchester, and north, towards Burnley."
Migration of hydrocarbons south-westwards from the Pennine Basin occurred during Silesian times.
"Permo - Triassic tectonism will have caused re-migration, although the hydrocarbons may still be retained within Carboniferous rocks."
"Hydrocarbons within Carboniferous rocks, west of the King Street Fault, probably migrated west or north: those within Carboniferous rocks east of the King Street Fault are likely to have migrated north-east."
"Using an East Midlands analogue, there may also be a play where the basal Westphalian sandstone unconformably overlies Dinantian rocks."
"This thinning coincides with the Dinantian synsedimentary Bakewell Fault, which was postulated between the Eyam and Woo Dale boreholes to account for the thickness changes in the Dinantian rocks."
The attractiveness of this position is enhanced by the likelihood of Silesian reservoirs of better quality than farther east.
"It is likely, therefore, that the Derbyshire high continues north-west and becomes progressively concealed by Westphalian and Permo - Triassic rocks, on the north-east margin of the Cheshire Basin."
"Other possible plays occur down-dip of the Milton Green inlier and on the block between the Wem and Hodnet faults, in areas also considered propective at the Helsby Sandstone level The main aquifer units in the Cheshire Basin belong to the SSG and the underlying Permian sandstones, principally the Collyhurst Sandstone Formation."
"The eastern boundary of the basin is mainly fault controlled, which has resulted in a much smaller area of sandstone outcrop, the overlying MMG sediments being faulted against Carboniferous rocks between Macclesfield and Newcastle-under-Lyme."
The MMG overlies the Triassic and Permian aquifers and attains a considerable thickness over much of the eastern two-thirds of Shropshire and the Cheshire Plain.
The aquifers of the SSG represent a major groundwater resource in north-west England.
"The Wilmslow Sandstone Formation tends to produce the largest yields because of its higher density of fracturing and less-cemented matrix, though the more pebbly Helsby Sandstone and Chester Pebble Beds are also very productive aquifers."
The saline water results from the dissolution of halite in the MMG.
A large area of saline water of this origin is found to the east of the Carboniferous inlier at Milton Green.
Water quality can also be poor in Drift deposits and in the limited water resources that are exploited from the MMG.
Nitrate concentrations in groundwater in the SSG have increased over the last three decades due to increased use of nitrogenous fertilisers in areas where recent recharge is occurring.
"In the north of the basin, the two units are separated by the Manchester Marls Formation, which is thought to act as an aquiclude."
"Porosities are high, especially in sections beneath the Chester Pebble Beds and close to outcrop where they are in the range 20 to 24%."
"These conglomerates and pebbly sandstones, overlying the Collyhurst and Kinnerton Sandstone Formations, gradually thicken to the north-west to 225m in the Manchester area and between 316 and 375m in the Warrington area."
"Hydraulic conductivities are, in general, higher in the south of the basin, but Fletcher states that around the River Tern they are only half that of the Collyhurst Sandstone Formation."
"Of the three members of the formation, the central Delamere Member is the least porous."
"In mid-Cheshire, where the Delamere Member is absent, porosity and hydraulic conductivity values are highest, attaining values of 30% and 2.5m/d respectively."
"The Tarporley Siltstone Formation, at the base of the MMG, is transitional between the Helsby Sandstone Formation and the overlying mudstone sequence."
"It generally has low values of hydraulic conductivity, although faulting can create hydraulic continuity with the Helsby Sandstone."
The sand and gravel deposits act as an important source of recharge to the SSG and also as a means of discharge.
"In an earlier project concerned with the prospectivity of the Carboniferous basins of the Pennines for metalliferous minerals, Wadge et al. argued that not only were computers necessary for databasing and modelling but they were also needed to capture the knowledge, both operative and interpretive, of the project team."
"A system such as this should be able to address major integrative modelling tasks, such as identifying the volumes of basin fill that are most prospective for end - Triassic copper mineralisation."
Figure 151 shows one such system result for borehole samples from the Kinnerton Sandstone Formation in the northern part of the basin.
"This paragenesis, although abbreviated, is equivalent in overall form to that deduced for all the SSG sandstones."
"Using these three categories it is possible to map all seven possible combinations of diagenetic domains, and Figure 152 shows an example using Thiessen polygons to show all borehole data for the SSG."
In Figure 153 we see the distribution of all minerals thought to be associated with the end - Triassic mineralisation event.
The Cheshire Basin lay in low latitudes during the Triassic and was part of a north‚ $ `` south system of connecting rifts.
The SSG comprises aeolian - deposited arenites borne on easterly winds and fluvial sediments associated with rivers draining from the south or south-east.
The succeeding MMG comprises mainly the deposits of a continental playa.
The source rocks for the detritus of the SSG probably come from four main areas:.
"In the example of the hypothesis ‚ $ òThis sample had an Armorican source‚ $ ô, the rule is: If Monazite/Zircon is very high AND If Apatite/Rutile is high AND If Tourmaline is very FeO rich AND If Palaeoflow Direction is northerly AND If Nd/Sm is moderate THEN Hypothesis is TRUE The result of the application of this rule to all samples of the Chester Pebble Beds Formation is shown in Figure 154."
The Chester Pebble Beds represent one of the notable fluvial excursions into the dominantly aeolian sedimentation regime of SSG deposition.
"The results are couched in terms of four fuzzy classes, from low to very high possibility that the Chester Pebble Beds, in aggregate at a certain borehole, were derived from an Armorican source."
"At the end of the Triassic, when the thermal phase of crustal extension in the Cheshire Basin was ending."
The metal content of the mixture was precipitated in faulted sandstones near the top of the SSG.
"The basin is floored by Upper Carboniferous rocks except in the extreme south-west of the basin, and prospectivity may thus be lower in the south-west."
This pattern may have existed at the end of the Triassic.
Flow vectors perpendicular to the end - Triassic basin margins.
Increased prospectivity at the intersection of these with the top of the Helsby Sandstone Formation.
Increased prospectivity where the Helsby Sandstone Formation is cut by north‚ $ `` south faults.
Increased prospectivity where the Helsby Sandstone Formation and MMG mudstones are faulted together.
"Figure 155 shows the results of one such simple model: a binary map showing increased prospectivity where the top of the Helsby Sandstone Formation is cut by north-south faults, expressed as a minimum-width grid scale of 1km."
"A rock-ridge topography, usually pronounced, is developed on many of the widespread rock exposures in shallow water ( Type 5 )."
In deeper water the rock surfaces are glacially smoothed and the ridges less pronounced.
"A grooved glaciated pavement was observed at -29 m off Burnmouth ( Eden, Carter and McKeown, 1969, p.250 )."
"Indistinct, discontinuous indications of ridges in deep water probably denote low glaciated exposures among boulder clay and plastic clay deposits, but these ridges have yet to be sampled."
"It seems probable that most of the rocks eroded into well-defined strike ridges are of Carboniferous and Upper Old Red Sandstone age, but some of the less well-defined strike-ridge areas may be of older rocks."
Homogeneous or flat-lying rocks are indicated by areas of high signal return but no lineation ( Type 4 ): these may be mainly of Lower Old Red Sandstone and Lower Palaeozoic age.
"A characteristic area showing Carboniferous rock-ridge topography was examined near Burnmouth by Scuba diving ( p.t7: Eden, Carter and McKeown, 1969 )."
"Four of the cores obtained with the Hulltype corer were of solid rock: three ( Plate 2 ) were Carboniferous ( stations 23, 24, 25 ) and one was Upper Old Red Sandstone ( station 5 ) in age."
"The project area lies predominantly on coal-bearing bedrock of Carboniferous age, with areas of older strata in the north."
"2.3 The complex mechanisms involved in the formation of till are beyond the scope of this account but the most common material, lodgement till, is the product of basal release of debris below ice sheets and glaciers."
' Flow till ' or ` ablation till ' is produced as debris flow at ice margins when large volumes of water are released during melting of the ice.
These sediments are overlain by the Baillieston Till Formation which formed in pre - late Devensian times.
North of Glasgow this till is overlain by sand and gravel of the Cadder Formation.
The sands and gravels in which the remains were found were possibly deposited as outwash related to the advance of the late - Devensian ice sheet.
"In southern parts of the city, muds of the Broomhill Formation occur discontinuously above the Baillieston Till."
"These formations are succeeded by the Wilderness Till Formation, which was deposited during the late - Devensian by an ice sheet that was over 1 km thick and covered large parts of Britain between 27 0 to 13 0 years ago."
"To the east of the ice dam in eastern Glasgow evidence for these events is provided by sand and gravel of the Broomhouse Formation, in which there are indications of southeastward transport of sediment."
"To the west, by contrast, deposits of sand and gravel of the Bridgeton Formation were carried and deposited by downstream currents."
"The oldest muds of the Paisley Formation are typically finely laminated and brightly coloured, with many silt layers, and are thought to have formed at the same time as the ice was melting."
2.11 The muds of the succeeding Linwood Formation are relatively poorly laminated and the upper part is sulphide-rich.
"Deposits of sand and gravel more or less contemporaneous with the Linwood Formation and which formed in river channels, deltas and beaches, are assigned to the Killearn Formation."
The extent of the ice is marked by the distribution of the Gartocharn Till Formation and by moundy topography that marks the location of the glacier-front.
"Periglacial conditions prevailed, as evidenced by frost-wedge casts, while marine muds with arctic shells, the Balloch Formation, were laid down in the western Clyde and Leven valleys."
"A shelly gravel, the Inverleven Formation, commonly underlies the Balloch Formation."
"An extensive ice-dammed lake occupied the Endrick and Blane Water valleys, and here sediments of the sandy Drumbeg and clay-dominated Blane Water formations were deposited."
"2.13 Sea-level then rose to a maximum of about 11 m to 13 m OD and subsequently fell to its present level, giving rise to sequences of marine and non-marine deposits, as detailed below, and the Clippens Peat Formation."
"The valleys are floored by a gravel, forming the base of the Longhaugh Formation, which mainly consists of sand with shell fragments."
This passes up into further sand deposits of the Gourock Formation and also well-bedded muds of the Erskine Formation.
"In Loch Lomond, the post Loch Lomond Stade succession opens with marine clays and silts of the Buchanan Formation which are overlain by non-marine clays and silts of the Kilmaronock Formation."
"These, in turn, are overlain by fluvial or deltaic sands and gravels of the Endrick Formation."
These formations are of Flandrian age.
"2.14 The general picture gleaned from the available field and archival borehole information and from the fifteen fully cored boreholes shows that the Quaternary sequence around Glasgow is complex, consisting of dozens of unique vertical successions, or profiles."
"Till consists chiefly of glacial diamicton, but may locally include lenses of clay, silt, sand or gravel."
"However, because the bedrock is Middle Coal Measures with many workable coal seams the possibility of undermining should be considered."
The fact that the bedrock is Upper Coal Measures with few mineral seams of any note means that the site is likely to be free of shallow mining.
"The original settlement of Hunstanton, now known as Old Hunstanton, probably gained its name from the River Hun, with Deri and Derlwyn formations to the coast just to the east of Dinas revealing Plean Nos. 1 and 2 limestones, the base of the Passage Formation is at a level approximately 5m above Plean No. 2 Limestone."

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