Volcanic rock facies Coal Measures facies Millstone Grit facies Yoredale facies Heterolithic clastic and nonmarine carbonate facies Continental and peritidal facies Non-sequences Equivalent to the BATHGATE GROUP in Falkirk, Fife and Lanarkshire Groups and main lith<strong>of</strong>acies Groups and <strong>for</strong>mations CENTRAL COALFIELD BASIN SCOTTISH COAL MEASURES GROUP CLACKMANNAN GROUP CLACKMANNAN GROUP STRATHCLYDE GROUP INVERCLYDE GROUP FIFE-LOTHIAN BASIN SCOTTISH COAL MEASURES GROUP CLACKMANNAN GROUP CLACKMANNAN GROUP STRATHCLYDE GROUP INVERCLYDE GROUP CENTRAL COALFIELD BASIN SCOTTISH COAL MEASURES Gp CLACKMANNAN GROUP STRATHCLYDE GROUP INVERCLYDE GROUP SCOTTISH UPPER COAL MEASURES FORMATION SCOTTISH MIDDLE COAL MEASURES FORMATION SCOTTISH LCM FORMATION PASSAGE FORMATION PASSAGE Fm UPPER LIMESTONE FORMATION LIMESTONE COAL FORMATION LOWER LIMESTONE FORMATION LAWMUIR Fm CLYDE PLATEAU VOLCANIC Fm CLYDE SANDSTONE FORMATION BALLAGAN FORMATION KINNESS- WOOD FORMATION KIRKWOOD Fm FIFE-LOTHIAN BASIN SCOTTISH COAL MEASURES Gp CLACKMANNAN GROUP STRATHCLYDE GROUP INVERCLYDE GROUP SCOTTISH UPPER COAL MEASURES FORMATION SCOTTISH MIDDLE COAL MEASURES FORMATION SCOTTISH LCM FORMATION PASSAGE FORMATION PASSAGE Fm UPPER LIMESTONE FORMATION LIMESTONE COAL FORMATION LOWER LIMESTONE FORMATION WEST LOTHIAN OIL- SHALE FORMATION GULLANE FORMATION ARTHUR’S SEAT VOLCANIC FORMATION CLYDE SAND- STONE BALLAGAN FORMATION KINNESS- WOOD FORMATION Chronostratigraphy WESTPHALIAN D BOLSOVIAN DUCKMANTIAN LANGSETTIAN YEADONIAN MARSDENIAN KINDERSCOU- TIAN ALPORTIAN CHOKIERIAN ARNSBERGIAN PENDLEIAN BRIGANTIAN ASBIAN HOLKERIAN - ARUNDIAN CHADIAN COURCEYAN FAMENNIAN Figure 5 <strong>Lithostratigraphical</strong> nomenclature <strong>for</strong> the midland valley <strong>of</strong> scotland. see Chapter 2 <strong>for</strong> description <strong>of</strong> lith<strong>of</strong>acies. a detailed lithostratigraphical classification <strong>for</strong> the midland valley <strong>of</strong> scotland is provided by Browne et al. (1999, table 1). Fm Formation; Gp Group; LCm Lower Coal measures 12 WESTPHALIAN NAMURIAN VISEAN TOURNAISIAN
from late arnsbergian to late alportian age, and the uppermost occurs between marine bands <strong>of</strong> Kinderscoutian to marsdenian age. The group is characterised by Yoredale and Millstone Grit facies. upward-coarsening Yoredale-type cycles <strong>of</strong> limestone, mudstone, siltstone and sandstone are capped by thin beds <strong>of</strong> seatearth and coal, the proportions differing in each <strong>of</strong> the <strong>for</strong>mations. The limestones are typically marine and laterally extensive, with standard names <strong>for</strong> the individual limestone beds used throughout the region. The passage Formation is characterised by upward-fining alternations <strong>of</strong> sandstone and structureless clayrock (including some economically important high-alumina seatclay, fireclay and bauxitic clay). marine faunas, diverse and closely spaced at the base <strong>of</strong> the <strong>for</strong>mation, become progressively impoverished upwards. depositional environments are related to the repeated advance and retreat <strong>of</strong> fluviodeltaic systems into an embayment <strong>of</strong> varying salinity. The Lower and upper Limestone <strong>for</strong>mations contain the highest proportion <strong>of</strong> marine deposits (Yoredale facies), whereas the passage Formation is dominated by alluvial deposits (Millstone Grit facies); the Limestone Coal Formation occupies an intermediate position. The Clackmannan Group is mostly Namurian in age, but ranges from late visean to early Langsettian. 4.4 SCOTTISH COAL MEASURES GROUP The Coal measures (Coal Measures facies) were regarded as a lithostratigraphical group by Forsyth et al. (1996). The epithet ‘scottish’ is proposed to distinguish the Coal measures <strong>of</strong> the midland valley <strong>of</strong> scotland from that <strong>of</strong> england and wales on account <strong>of</strong> the different definitions <strong>of</strong> the base <strong>of</strong> the upper Coal measures and the base <strong>of</strong> the groups. The Lower, middle and upper divisions, recognised in the older classification, are retained and regarded now as in<strong>for</strong>mal <strong>for</strong>mations. again, the epithet ‘scottish’ can be applied to the <strong>for</strong>mations where it is necessary to distinguish them from <strong>for</strong>mations in england and wales. The scottish Lower and middle Coal measures are 220 to 240 m and 350 m thick, respectively. The maximum thickness <strong>of</strong> the scottish upper Coal measures probably exceeds 1200 m. The base <strong>of</strong> the group is taken at the base <strong>of</strong> the Lowstone marine Band, its local correlative, or at a plane <strong>of</strong> discon<strong>for</strong>mity. This is at a slightly higher stratigraphical level than in the pennine Coal measures Group, where it lies at the base <strong>of</strong> the subcrenatum marine Band, which is not recognised in scotland. The base <strong>of</strong> scottish middle and upper Coal measures are also taken at the bases <strong>of</strong> marine bands, namely the vanderbeckei (Queenslie) and aegiranum (skipsey’s) marine bands, respectively. The base <strong>of</strong> the scottish upper Coal measures is taken, here, at a lower stratigraphical level than the equivalent pennine upper Coal measures. The top <strong>of</strong> the group is marked by an erosional uncon<strong>for</strong>mity <strong>of</strong> regional extent beneath permian strata. The group comprises repeated cycles <strong>of</strong> typically grey sandstone and mudstone with coal and seatearth, arranged in both upward-fining and upward-coarsening units. marine bands are rare but provide important stratigraphical markers. The scottish Lower and middle Coal measures are lithologically similar, with common, economically important coal seams, few <strong>of</strong> which can be correlated between coalfields. minor lithologies include cannel coal, and 13 blackband and clayband ironstone, the last is nodular as well as bedded. Bands composed mainly <strong>of</strong> nonmarine bivalves, the characteristic ‘musselbands’, usually occur in mudstone or ironstone. upward-fining units are widely developed, dominated by fine- to coarse-grained sandstone, and thick multistorey sandstones are a characteristic part <strong>of</strong> the succession. within the scottish upper Coal measures coal seams are thin and uncommon, and the succession is extensively reddened. environments <strong>of</strong> deposition include wetland <strong>for</strong>est (soils), floodplain, river and delta distributary channel, prograding deltas and shallow lakes. The group ranges from Langsettian to westphalian d age. The scottish Lower and middle Coal measures are equivalent to chronostratigraphical units <strong>of</strong> Langsettian and duckmantian age. within the scottish upper Coal measures, faunas representative <strong>of</strong> the A. phillipsii and A. tenuis zones have been recognised (mykura, 1967), and floras indicative <strong>of</strong> Bolsovian and westphalian d stages (scott, 1976). No stephanian rocks have been identified in the midland valley <strong>of</strong> scotland. 4.5 BATHGATE GROUP The Bathgate Group (Figure 5) is <strong>of</strong> limited geographical extent (Falkirk, Fife, Lanarkshire, west Lothian) but interdigitates with a large thickness <strong>of</strong> the upper part <strong>of</strong> the strathclyde Group and the larger part <strong>of</strong> the Clackmannan Group. The Bathgate Group comprises the salsburgh volcanic, Kinghorn volcanic and Bathgate Hills volcanic <strong>for</strong>mations. The volcanic <strong>for</strong>mations are separated from one another by sedimentary rocks, but their petrographical similarity and restricted geographical extent justify their treatment as a single group. The group is very variable in thickness, locally occurring in excess <strong>of</strong> 450 m. The base <strong>of</strong> the group is taken in most areas at an upward transition from sedimentary rocks <strong>of</strong> the strathclyde or Clackmannan groups. The Bathgate Group is characterised by olivine-rich microporphyritic basalts <strong>of</strong> dalmeny and Hillhouse type, with some macroporphyritic olivine-basalts <strong>of</strong> Craiglockhart and dunsapie types. Bedded tuffites and tuffaceous sedimentary rocks also occur. The group ranges from asbian to arnsbergian age. 4.6 CORRELATION WITH CENTRAL AND NORTHERN NORTH SEA The devonian and <strong>Carboniferous</strong> strata <strong>of</strong> the Central and Northern North sea occupy a depositional basin that is laterally contiguous with, and located to the east <strong>of</strong>, the midland valley <strong>of</strong> scotland (Figure 1). The succession, defined by Cameron (1993a), comprises a single group, the upper Old Red Group, and a stand-alone <strong>for</strong>mation, the Firth Coal Formation. 4.6.1 Upper Old Red Group The upper Old Red Group is the <strong>of</strong>fshore equivalent <strong>of</strong> the onshore upper Old Red sandstone Group and the overlying inverclyde Group (Continental and peritidal facies). in the Outer moray Firth, western plat<strong>for</strong>m and Central Graben the group consists <strong>of</strong> two <strong>for</strong>mations, the Buchan and Tayport <strong>for</strong>mations. The upper part <strong>of</strong> the Buchan Formation is the <strong>of</strong>fshore equivalent <strong>of</strong> the onshore Kinnesswood
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