The BGS Lexicon of Named Rock Units — Result Details
Llynfi Member
| Computer Code: | LLFB | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Bolsovian Substage (CC) — Bolsovian Substage (CC) | ||
| Lithological Description: | Green-grey and blue-grey, feldspathic, micaceous lithic arenites ('Pennant sandstones') with thin mudstone/siltstone and seatearth interbeds and mainly thin coals. Bolsovian. | ||
| Definition of Lower Boundary: | The base is placed at the base of the lowermost thick (over about 3 m) bed of lithic arenite ('Pennant sandstone'), overlying the mudstone-dominated succession of the South Wales Coal Measures Group. The base lies immediately above the Cambriense (Upper Cwmgorse) Marine Band in south-west of the South Wales Coalfield basin. Northeastwards, the Pennant sandstone facies commences at a progessively higher level. | ||
| Definition of Upper Boundary: | The top is taken at the base of the No.2 Rhondda Coal (Woodland et al., 1957), overlain by lithic arenite and thin mudstones and siltstones which make up most of the Rhondda Member. The base of the coal rests on a mainly thin development of seatearth and mudstone at the top of the member, which overlie thick lithic arenites. | ||
| Thickness: | Up to 420 m in the Swansea district. | ||
| Geographical Limits: | South Wales Coalfield, extending on the south crop from the Swansea district [SS 533 955] east to the Ferndale area [SS 9995]. | ||
| Parent Unit: | Pennant Sandstone Formation (PES) | ||
| Previous Name(s): | Llynfi Formation [Obsolete Name and Code: Use LLFB]
(-2905)
Llynfi Beds [Obsolete Name and Code: Use SWUCM, LLFB] (-366) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Type area is in the Llynfi Valley, near Tondu, South Wales [SS 896 850] (Woodland et al., 1957). | ||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E262 E247 E232 E231 E230 E246 | |||