Scottish Coal Measures Group

Scottish Coal Measures Group
Stratigraphic range: Langsettian (Westphalian A) –
Bolsovian (Westphalian C)
TypeGroup
Unit ofCoal Measures Group
Sub-unitsScottish Upper Coal Measures Formation, Scottish Middle Coal Measures Formation, Scottish Lower Coal Measures Formation
UnderliesMauchline Volcanic Formation
OverliesPassage Formation (Clackmannan Group)
Thicknessup to 940 m
Lithology
Primarymudstone, sandstone
Othersiltstone, coal, seatearth
Location
RegionScotland
ExtentMidland Valley

The Scottish Coal Measures Group is a lithostratigraphic unit referring to the coal-bearing succession of rock strata which occur in Scotland during the Westphalian regional stage of the Carboniferous Period. It is the Scottish portion of the informal Coal Measures Group, which also includes the South Wales and Pennine coal measures. The Scottish coal measures are well-exposed across the Midland Valley. The group is also found within small grabens in the vicinity of Sanquhar and Thornhill.[1]

Stratigraphy

From youngest to oldest, the Scottish Coal Measures Group comprises the:[1]

  • Scottish Upper Coal Measures Formation (Bolsovian / Westphalian C)
  • Scottish Middle Coal Measures Formation (Duckmantian / Westphalian B)
  • Scottish Lower Coal Measures Formation (Langsettian / Westphalian A)

Paleobiota

The Scottish coal measures represent a lush coal swamp ecosystem populated by large amphibious tetrapods (amphibians, in the broad sense). Amphibians known from the group include embolomeres (Anthracosaurus, Palaeoherpeton, Pholiderpeton [formerly Eogyrinus]) and baphetids (Baphetes, Loxomma, Megalocephalus).[2][3]

Typical Westphalian-age marine fossils and plant impressions are abundant in some coal beds. Insect fossils are rarer in Scottish coal relative to England or Wales. Only five insect genera are known from the Scottish coal measures: Truemania (a dragonfly-like meganisopteran), Lithomantis and Idoptilus (palaeodictyopterans), and Archimylacris and Lithomylacris (roachoids).[4]

References

  1. ^ a b Waters, C.N.; Browne, M.A.E.; Jones, N.S.; Somerville, I.D. (2011-07-13), Waters, C.N.; Somerville, I.D.; Jones, N.S.; Cleal, C.J. (eds.), "Midland Valley of Scotland", A Revised Correlation of Carboniferous Rocks in the British Isles (First ed.), The Geological Society of London, pp. 96–102, doi:10.1144/sr26.14, ISBN 978-1-86239-694-4
  2. ^ Panchen, A.L.; Walker, A.D. (1960). "British coal measure labyrinthodont localities". Annals and Magazine of Natural History. 3 (30): 321–332. doi:10.1080/00222936008655774. ISSN 0374-5481.
  3. ^ Smithson, T. R. (1985). "Scottish Carboniferous amphibian localities". Scottish Journal of Geology. 21 (2): 123–142. doi:10.1144/sjg21020123. ISSN 0036-9276.
  4. ^ Ross, A. J. (2010). "A review of the Carboniferous fossil insects from Scotland". Scottish Journal of Geology. 46 (2): 157–168. doi:10.1144/0036-9276/01-413. ISSN 0036-9276.