The BGS Lexicon of Named Rock Units — Result Details
Brithdir Member
| Computer Code: | BD | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Asturian Substage (CAS) — Asturian Substage (CAS) | ||
| Lithological Description: | Green-grey, lithic arenites ('Pennant sandstones') with conglomerate lenses at bases of units; thin mudstone/siltstone and seatearth interbeds and mainly thin coals. Age Asturian. | ||
| Definition of Lower Boundary: | The base is placed at the base of the Brithdir Coal, above 'Pennant' sandstones and thin mudstones/siltstones of the Rhondda Member or above red/green mudstones of the Deri Formation on the east crop of the coalfield. | ||
| Definition of Upper Boundary: | The top is placed at the base of the Hughes (Cefn Glas) Coal, where the coal rests on either 'Pennant' sandstones or thin mudstones/siltstones at the top of the Brithdir Member. The coal is overlain by 'Pennant' sandstones or thin mudstones/siltstones of the Hughes Member. | ||
| Thickness: | From 45 m in the Pontypool area [ST 268 990] to 200 m in the Swansea area [SS 660 945]. | ||
| Geographical Limits: | Extensive throughout the South Wales Coalfield, from Pembrey [SN 42 02] east to Blaenavon [SO 230 085] and, on the south crop, from Gower, [SS 545 960] to Pontypool [ST 268 990]. | ||
| Parent Unit: | Pennant Sandstone Formation (PES) | ||
| Previous Name(s): | Brithdir Formation [Obsolete Name and Code: Use BD]
(-2589)
Brithdir Beds [Obsolete Name and Code: Use BD] (-1973) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | There is no originally designated type section or type area, the member being named after its basal coal. The member occurs extensively throughout the South Wales Coalfield [SS 545 960 to 268 990] (Woodland et al., 1957). | ||
| Reference Section | Craig-yr-Hesg Quarries, north of Pontypridd in the Taff Valley [ST 0790 9180]. Quarry facies 40 m high expose massive, lithic ('Pennant') sandstones, with individual units over 4 m thick (Woodland and Evans, 1964). | ||
| Reference(s): | |||
| 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. | |||
| Woodland, A W, Evans, W B and Stephens, J V. 1957. Classification of the Coal Measures of South Wales with Special reference to the Upper Coal Measures. Bulletin of the Geological Survey of Great Britain, No. 13, 39-60. | |||
| Woodland, A W and Evans, W B. 1964. The Geology of the South Wales Coalfield, part IV the Country around Pontypridd and Maesteg. Memoirs of the Geological Survey of Great Britain, One-Inch Geological Sheet 248 (England and Wales). | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E231 E230 E249 E246 E232 | |||