Five Yard Limestone Member

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Five Yard Limestone Member (FYL), Carboniferous, Northern England Province[edit]

Five Yard Limestone Member is part of the Alston Formation

Name[edit]

No longer bed status, now a member of the Alston Formation. See Arthurton and Wadge (1981)[1]; Dunham (1990)[2]; Burgess and Holliday (1979)[3]; Trotter and Hollingworth (1932)[4]; Eastwood et al. (1968)[5]; Johnson and Nudds (1996)[6]; Johnson et al. (1980)[7].

Lithology[edit]

Limestone, dark grey, argillaceous, becoming grey compact towards base. In the south, fine-grained with thin evenly bedded mudstone partings with many fossils; in the north becoming increasingly crinoidal and locally characterised by coarse crinoidal debris. Intercalated thin unit (up to 2.1 m thick) of black fossiliferous calcareous mudstone which divides the member into two parts. Stylolitic particularly near the base (Johnson and Nudds, 1996[6]).

Stratotype[edit]

The type section is at Lunchy Beck (NY 6036 4822), a northern tributary of Croglin Water, Cumbria, where the Five Yard Limestone is a dark blue-grey, thick-bedded limestone with muddy partings, 4.9 m thick (Arthurton and Wadge, 1981, pp. 43–44[1]). A reference section is provided by the Rookhope Borehole (BGS Registration Number NY94SW/1) (NY 9375 4278) from 109.7 to 114.3 m depth including a 0.53 m-thick interbed of black fossiliferous calcareous shale (see Johnson and Nudds, 1996, p. 190[6]).

Lower and upper boundaries[edit]

The lower boundary is taken at the sharp base of the limestone overlying measures within the Alston Formation. It is directly underlain by burrowed, current and ripple-bedded, medium-grained sandstone; a thin coal is present in places.

The upper boundary of the member is taken at the base of the overlying mudstone within measures of the Alston Formation.

Thickness[edit]

Between 3 and 8.5 m.

Distribution and regional correlation:[edit]

A member within the Alston Formation of the Alston and Lake District blocks in Cumbria, Northumberland and Durham, lying stratigraphically between the Scar (below) and the Three Yard (above) limestone members (Figure 11, Column 1; Figure 14, Columns 2, 3; Figure 15, Column 1). Possibly correlated with the Eelwell Limestone Member of the Northumberland Trough. The limestone is well exposed along the Pennine escarpment in Teesdale and Weardale. It is well known from subsurface workings, boreholes and shafts within the Alston Block. It is present in deep boreholes including the Longcleugh No 1 Borehole in the West Allen Valley (Johnson et al., 1980[7]), and the Rookhope and Allenheads No. 1 boreholes (see above).

Age[edit]

Brigantian. On Dun Fell the limestone has yielded goniatites indicating the Neoglyphioceras subcirculare P2b Subzone (Johnson and Dunham, 1963[8]; Dunham, 1990[2]). In the Rookhope Borehole (see above) the first appearance of the foraminifers Janischewskina typica and Endothyranopsis sphaerica, and the alga Calcifolium okense indicate the late Brigantian upper Cf6ð¨ Subzone (see Cozar and Somerville, 2004[9]).

References[edit]

  1. 1.0 1.1 Arthurton, R S, and Wadge, A J.1981.Geology of the country around Penrith.Memoir of the Geological Survey of Great Britain, Sheet 24 (England and Wales)
  2. 2.0 2.1 Dunham, K C.1990.Geology of The Northern Pennine Orefield: Volume 1, Tyne to Stainmore (2nd edition).Economic Memoir of the British Geological Survey, Sheets 19 and 25, parts 13, 24, 26, 31 and 32 (England and Wales)
  3. Burgess, I C, and Holliday, D W.1979.Geology of the country around Brough-under-Stainmore.Memoir of the Geological Survey of Great Britain, Sheet 31, parts 25 and 30 (England and Wales)
  4. Trotter, F M, and Hollingworth, S E.1932.The geology of the Brampton district.Memoir of the Geological Survey of Great Britain, Sheet 18 (England and Wales)
  5. Eastwood, T, Hollingworth, S E, Rose, W C C, and Trotter, F M.1968.Geology of the country around Cockermouth and Caldbeck.Memoir of the Geological Survey of Great Britain, Sheet 23 (England and Wales)
  6. 6.0 6.1 6.2 Johnson, G A L, and Nudds, J R. 1996.Carboniferous biostratigraphy of the Rookhope Borehole, County Durham.Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 86, 181–226
  7. 7.0 7.1 Johnson, G A L, Nudds, J R, and Robinson, D.1980.Carboniferous stratigratigraphy and mineralisation at Ninebanks, West Allendale, Northumberland.Proceedings of the Yorkshire Geological Society, Vol. 43, 1–16.
  8. Johnson, G A L, and Dunham, K C.1963.The geology of Moor House.Monographs of the Nature Conservancy, No 2.
  9. Cozar, P, and Somerville, I D.2004.New algal–foraminiferal evidence for the recognition of the Asbian–Brigantian boundary in northern England.Proceedings of the Yorkshire Geological Society, Vol. 55, 43–65