The BGS Lexicon of Named Rock Units — Result Details

Red Wharf Limestone Formation

Computer Code: REL Preferred Map Code: REL
Status Code: Full
Age range: Brigantian Substage (CX) — Brigantian Substage (CX)
Lithological Description: Massive or irregularly bedded skeletal limestones (packstones and grainstones), commonly sandy, with abundant chert nodules. The formation comprises a series of shoaling upwards cycles capped by palaeokarstic surfaces commonly overlain by beds of sandstone infilling karstic pipes, or by channel-filling sequences of conglomerate, sandstone and silty mudstone. The Red Wharf Limestone Formation records late Brigantian, mixed carbonate-siliciclastic shallow marine deposition at a time of increased supply of siliciclastic detritus to the North Wales Dinantian platform. Each cycle represents a shoaling upwards sequence formed in response to transgressive and regressive movements in sea level. Many regressions culminated in emergence of the platform surface and the formation of karstic dissolution feartures and of channels that were filled by fluvial conglomerates and sandstone and estuarine mudstones.
Definition of Lower Boundary: Not exposed, but assumed to be a contact between massive sandy limestones with abundant chert nodules and lithologically more varied limestone sequence of the underlying Cefn Mawr Limestone Formation. The contact is likely to be taken at a palaeokarstic surface developed at the top of the uppermost Cefn Mawr Limestone cycle.
Definition of Upper Boundary: In its type section, the Red Wharf Limestone Formation is overlain by a 6m-thick unit of bedded cherts, which was previously included in the Formation as the Castell Mawr Chert Member, but which may now be viewed as a local representive of the Pentre Chert Formation.
Thickness: c.55m
Geographical Limits: Western side of Red Wharf Bay on Angelsey [SH5381], and Great Orme at Llandudno [SH7483], North Wales.
Parent Unit: Clwyd Limestone Group (CLWYD)
Previous Name(s): Red Wharf Cherty Limestone (-1787)
Red Wharf Limestone (-2392)
Summit Limestone Formation [Obsolete Name And Code: Use REL] (SUL)
Dinorwic Formation [Obsolete Name And Code: Use REL] (DWIC)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Cliffs north of Red Wharf, Anglesey, which expose the upper 55m of the Formation, above a faulted base. Davies, 1983 
Type Area  Red Wharf Bay, Sheet 94. 
Reference(s):
Walkden, G M and Davies, J R, 1983. Polyphase erosion of subarerial omission surfaces in the late Dinantion of Anglesey, North Wales. Sedimentology, 30, 861-878. 
Waters, C N, Waters, R A, Barclay, W J, and Davies, J R. 2009. Lithostratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/09/01. 184pp. 
Davies, J A, 1983. The stratigraphy, sedimentology and palaeontology of the Lower Carboniferous of Anglesey. 1983. Unpublished PhD thesis, University of Keele. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E094