Calders Member

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Calders Member (CDE), Carboniferous, Midland Valley of Scotland[edit]

Calders Member is part of the West Lothian Oil-Shale Formation

Name[edit]

The name was proposed by Chisholm et al. (1989)[1], the main outcrop area and the thickest development of the member being around West Calder, Midcalder and East Calder.

Lithology[edit]

The Calders Member comprises a succession of black to grey mudstones, grey siltstones and white, grey and pink sandstones with thin beds of grey argillaceous, limestone and dolostone (‘cementstone’), and algal-rich black to grey oil shales with some lapilli-tuff beds. The strata are not disposed in readily recognisable sedimentary cycles. The member includes the Dalmahoy Oil-Shale, Hailes Sandstone (which was much worked in the past for dimension stone), Pumpherston Shell Bed (a bed of fossiliferous mudstone with a marine fauna), and the overlying Pumpherston Oil-Shale. A regionally persistent but thin (less than 1.m) algal dolostone has been recognised at Hopetoun and Queensferry.

Genetic interpretation[edit]

The strata are almost all of lacustrine and fluvial origins, with sporadic marine incursions.

Stratotype[edit]

The type section is the shore at Queensferry between Longcraig Pier (NT 144 786) and just east of the Forth Railway Bridge (NT 138 784) (Carruthers et al., 1927 p..80[2]; McAdam and Clarkson, 1986, map 24)[3]. Reference sections include the shore and coastal section at Hopetoun (NT 088 793 to 094 791) (Carruthers et al., 1927[2]), and the river section in the Water of Leith near Redhall in Edinburgh (NT 217 702 to 214 697) (Chisholm and Brand, 1994, p. 100[4]), which exposes the Redhall Marine Band and overlying mudstones with oil-shales, up to the base of the Hailes Sandstone.

Lower and upper boundaries[edit]

The lower boundary is defined by the Redhall (Humbie) Marine Band. This is the lowest of the Macgregor Marine Bands in the area, up to 0.3.m thick, and in Edinburgh is contained within at least 13.8.m of generally tough, black and dark grey mudstones. The lowest 9.m of these mudstones form the top of the underlying Gullane Formation (Chisholm and Brand, 1994, p..100[4]) which are assigned to the currently undefined Wardie Shales Member.

The top of the Calders Member is defined at the base of the Burdiehouse Limestone (BULS) (Mitchell and Mykura, 1962, p. 67[5]) (Figure 6, Column 4D).

Thickness[edit]

The member is on average about 290 m thick (Cameron and McAdam, 1978, fig. 2[6]) but estimated at 350 m in west Edinburgh. The Hailes Sandstone has a maximum thickness of about 57 m.

Distribution and regional correlation[edit]

West Lothian and part of Midlothian. The unit is no longer mapped as Calders Member in Fife, where it is now mapped as the Sandy Craig Formation (Figure 6, Column 4C).

Age and biostratigraphical characterisation[edit]

Asbian. Currie (1954)[7] listed ammonoids from the Pumpherston Shell Bed including Beyrichoceratoides aff. fournieri, B. cf. fournieri or B. cf. redesdalensis, B. cf. truncatus and ?Dimorphoceras sp. On the evidence available Currie (1954)[7] and George et al. (1976)[8] assigned the Pumpherston Shell Bed to the middle Visean (Asbian).

References[edit]

  1. Chisholm, J I, McAdam, A D, and Brand, P J.1989.Litho-stratigraphical classification of Upper Devonian and Lower Carboniferous rocks in the Lothians.British Geological Survey Technical Report, WA/89/26
  2. 2.0 2.1 Carruthers, R G, Caldwell, W, Bailey, E M, and Conacher, H R J.1927.The oil shales of the Lothians (3rd edition).Memoir of the Geological Survey of Great Britain
  3. McAdam, A D, and Clarkson, E N K.1986.Lothian Geology: an excursion guide. (Edinburgh: Edinburgh Geological Society.)
  4. 4.0 4.1 Chisholm, J I, and Brand, P J.1994.Revision of the late Dinantian sequence in Edinburgh and West Lothian.Scottish Journal of Geology, Vol. 30, 97–104
  5. Mitchell, G H, and Mykura, W.1962.The Geology of the neighbourhood of Edinburgh.Memoir of the Geological Survey of Great Britain, Sheet 32 (Scotland)
  6. Cameron, I B, and McAdam, A D.1978.The oil shales of the Lothians, Scotland: present resources and former workings.Report of the Geological Survey of Great Britain, No. 78/28
  7. 7.0 7.1 Currie, E D.1954.Scottish Carboniferous goniatites.Transactions of the Royal Society of Edinburgh, Vol. 62, Pt. 2, 527–602.
  8. George, T N, Johnson, G A L, Mitchell, M, Prentice, J E, Ramsbottom, W H C, Sevastopulo, G D, and Wilson, R B.1976.A correlation of Dinantian rocks in the British Isles.Geological Society of London Special Report, No.7