The BGS Lexicon of Named Rock Units — Result Details
Broad Vein Mudstone Formation
Computer Code: | BRV | Preferred Map Code: | notEntered |
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Status Code: | Pending Upgrade | ||
Age range: | Rawtheyan Stage (OW) — Rawtheyan Stage (OW) | ||
Lithological Description: | Pale-medium blue, silty-mudstone, intensely bioturbated in parts. | ||
Definition of Lower Boundary: | No lower boundary is exposed but the pale-medium blue mudstones of the Formation rest with sharp contrast upon the black mudstones of the Nod Glas Formation. | ||
Definition of Upper Boundary: | The upper boundary can be examined at Aberllefenni Quarry, where the contact is transitional, over 0.5m, from the pale-blue of the Broad Vein Mudstone Formation to a medium-blue, laminated silty mudstone of the Narrow Vein Mudstone Formation, accompanied by the development of lamination. | ||
Thickness: | 400 to 560m | ||
Geographical Limits: | Passes west into Cardigan Bay. The outcrop of the Broad Vein Formation crosses sheet 149 diagonally from southwest - northeast (Tywyn - Aberllefenni). | ||
Parent Unit: | Abercorris Group (ARO) | ||
Previous Name(s): | Broad Vein [Obsolete Name and Code: Use BRV]
(-3245)
Broad Vein Formation [Obsolete Name and Code: Use BRV] (-2025) Red Vein [Obsolete Name and Code: Use BRV] (-1393) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Section | The southwest facing slope of Foel Crochan, northeast of Aberllefenni Quarry. No reference sections need be cited as the type section is fully representative of the Formation. | ||
Reference(s): | |||
Pratt, W T, Woodhall, D G and Howells, M F. 1995. Geology of the country around Cadair Idris. Memoir of the British Geological Survey, Sheet 149. (England and Wales). (London: HMSO), 111pp | |||
Pratt, W T, Scott, M M, Leng, M J. 1990. Geological notes and local details for sheets SH71SE and SH71NE, Cadair Idris. British Geological Survey Technical Report WA/90/41. | |||
Pugh, W J. 1923. The geology of the district around Corris and Aberllefenni, (Merionethshire). Quarterly Journal of the Geological Society, London, Vol.79, 508-541. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E149 |