Difference between revisions of "Tynebottom Limestone Member"
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Tynebottom Limestone Member is part of the Alston Formation
The member is so-called because it crops out in, or is closely underlying, the bed of the River South Tyne between Alston and Tynehead. It no longer has bed status (i.e. the Tyne Bottom Limestone of, for example, Trotter and Hollingworth, 1932), but is now a member of the Alston Formation. See Johnson and Dunham (1963); Dunham (1990); Burgess and Holliday (1979); Eastwood et al. (1968); Johnson and Nudds (1996); Arthurton and Wadge (1981).
Limestone, blue-grey, thick-bedded, planar to wavy-bedded, stylolitic, in part fissile with intercalated thin mudstone beds. Fossiliferous, particularly with abundant corals, brachiopods and crinoid debris. It commonly has a Saccamminopsis band 1.5 to 2 m from the top. A bed near the top is characteristically argillaceous and ‘slaggy’ (Johnson and Dunham 1963).
The type area is High Cup Gill, Dufton Fell, Cumbria (NY 730 250 to 752 274) where about 8 m of limestone are exposed (see Burgess and Holliday, 1979, fig. 26, col..6). A reference section is the Rookhope Borehole (BGS Registration Number NY94SW/1) (NY 9375 4278) from 175.62 to 184.94 m depth (Johnson and Nudds, 1996).
Lower and upper boundaries
The lower boundary is taken at the sharp base of limestone overlying measures within the Alston Formation, in places comprising sandstone, elsewhere mudstone.
The upper boundary of the member is taken at the base of overlying measures within the Alston Formation, here usually comprising up to about 10 m of compact, hard, dark grey mudstone colloquially referred to as the Tyne Bottom Plate.
Between 7.6 and 14.6 m.
Distribution and regional correlation
The member crops out in, or closely underlies, the bed of the River South Tyne between Alston and Tynehead. 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. The member occurs within the Alston Formation of the Alston and Lake District blocks in Cumbria, Northumberland and Durham, lying between the Jew (below) and the Scar (above) limestone members (Figure 11, Column.1; Figure.14, Column 2). It is present in the Rookhope Borehole (Figure.15, Column.1) (see above) and the Allenheads No..1 Borehole (BGS Registration Number NY84NE/4) (NY 8604 4539).
Age and biostratigraphical characterisation
Brigantian. Cozar and Somerville (2004) record a single specimen of the foraminifer Asteroarchaediscus from the Tynebottom Limestone Member in the Rookhope Borehole (see above). This genus is only present in the uppermost lower Brigantian and mostly occurs in the upper Brigantian (Cozar and Somerville, 2004 and references therein).
- 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).
- Johnson, G A L, and Dunham, K C.1963.The geology of Moor House.Monographs of the Nature Conservancy, No 2.
- 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).
- 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).
- 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).
- 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.
- 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).
- 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.