The BGS Lexicon of Named Rock Units — Result Details
Darren Ddu Limestone Member
Computer Code: | DDLM | Preferred Map Code: | notEntered |
---|---|---|---|
Status Code: | Full | ||
Age range: | Courceyan Substage (CF) — Courceyan Substage (CF) | ||
Lithological Description: | Thinly bedded, pale grey micritic limestones (lime mudstones), locally peloidal, with grey-green mudstones and cream laminated dolomitic mudstones; algal laminite locally at the top. | ||
Definition of Lower Boundary: | The base is placed at the sharp, planar junction between pale grey lime mudstone at the base of the Member and the underlying fine-grained dolostone of the lower part of the Coed Ffyddlwn Formation. | ||
Definition of Upper Boundary: | The upper boundary is placed at an irregular, stylolitized surface cut in the topmost pale grey lime mudstones of the Member, which is overlain by a coarse bioclastic grainstone (the Craig-y-Gaer Coral Bed) at the base of the Gilwern Oolite Formation. | ||
Thickness: | 2 to 3m | ||
Geographical Limits: | Clydach valley, on the northeast crop of the South Wales Coalfield [SO 215 125]. | ||
Parent Unit: | Coed Ffyddlwn Formation (COFYD) | ||
Previous Name(s): | Bed 6 (part of Marker Beds) [Obsolete Name and Code: Use DDLM]
(-4600)
Clydach Beds [Obsolete Name and Code: Use DDLM, CLD] (-1440) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Section | A small disused quarry [SO 2194 1290] on Darren Ddu, Clydach Valley, 2km east of Brynmawr, Blaenau-Gwent, South Wales exposes 2.36m of thinly bedded lime mudstones, grey-green mudstones and dolomitic mudstones resting with sharp planar contact on fine-grained dolostones. Barclay, 1989. | ||
Reference(s): | |||
George, T N. 1954. Pre-Seminulan Main Limestone of the Avonian Series in Breconshire. Quarterly Journal of the Geological Society of London, Vol.110, 282-322. | |||
Barclay, W J, Jackson, D I, Mitchell, M, Owen, B, Riley, N J, White, D E, Strong, G E and Monkhouse, R A. 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny. Memoir of the British Geological Survey. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E232 |