The BGS Lexicon of Named Rock Units — Result Details
Rhondda Member
| Computer Code: | RA | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Bolsovian Substage (CC) — Asturian Substage (CAS) | ||
| Lithological Description: | Green-grey, lithic arenites ('Pennant sandstones') with thin mudstone/siltstone and seatearth interbeds and mainly thin coals. Bolsovian to Asturian. | ||
| Definition of Lower Boundary: | The base of the Member is placed at the base of the No.2 Rhondda Coal in the type area of the Rhondda valleys; the seam is named the Llwydcoed Seam in the Ammanford district and the Wernddu in the Swansea district. The coal rests conformably on lithic ('Pennant') sandstones and thin mudstones/siltstones of the underlying Llynfi Member. | ||
| Definition of Upper Boundary: | The top is placed at the base of the Brithdir Coal, where the coal overlies thin mudstone/seatearth at the top of the Member and is overlain by lithic ('Pennant') sandstone and thin siltstone/mudstone of the Brithdir Member. | ||
| Thickness: | Up to 320 m in the Swansea - Port Talbot district [c. SS 775 940]. | ||
| Geographical Limits: | South Wales Coalfield; on north crop from Burry Port [SN 42 02] to the Bargoed Taff Valley [SO 115 054] and on the south crop from the Loughor estuary [SS 535 957] to Risca [ST 24 92]. | ||
| Parent Unit: | Pennant Sandstone Formation (PES) | ||
| Previous Name(s): | Rhondda Beds [Obsolete Name and Code: Use RA]
(-2387)
Rhondda Formation [Obsolete Name and Code: Use RA] (-4282) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | The Type Area is the area of the Rhondda valleys, South Wales [SS 98 95] (Woodland et al., 1957). | ||
| Reference Section | Ty'n-y-bedw Quarry [SS 9690 9700], Treorchy, Rhondda valley, South Wales provides a reference section. It exposes 44 m of massive and cross-bedded sandstones with several beds of siltstone and silty mudstone up to 3 m thick. The base of the section lies 3-6 m above the No.2 Rhondda Coal (Woodland and Evans, 1964). | ||
| Reference(s): | |||
| 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). | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E231 E230 E246 E247 E232 | |||