The BGS Lexicon of Named Rock Units — Result Details

Hughes Member

Computer Code: H Preferred Map Code: notEntered
Status Code: Full
Age range: Asturian Substage (CAS) — Asturian Substage (CAS)
Lithological Description: Green-grey, lithic arenites ("Pennant sandstones"), with thin mudstone/siltstone and seatearth interbeds, and mainly thin coals.
Definition of Lower Boundary: The base is placed at the base of the Hughes Coal or its equivalent (Cefn Glas, Wenallt, Bettws Four-Feet, Ty-du, etc) in a predominantly arenaceous sequence of the Pennant Sandstone Formation, where the coal rests on mudstone/siltstone seatearth at the top of the Brithdir Member.
Definition of Upper Boundary: The top is placed at the base of the Golden Seam or its equivalent (Swansea Three-Feet, Graigola) at the base of a predominantly arenaceous sequence of the Swansea Member, where the coal rests on mudstones/siltstone and seatearth at the top of the Hughes Member. In the east of the coalfield, the top is placed at the base of the Mynyddislwyn Coal.
Thickness: From 45m near Pontypool [SO 250 150] thickening westwards to 270m near Swansea [SS 570 960].
Geographical Limits: Widespread outcrop throughout the South Wales Coalfield, from Llanelli [SN 49 02] to near Pontypool [ST 268 980].
Parent Unit: Pennant Sandstone Formation (PES)
Previous Name(s): Hughes Formation (-2226)
Hughes Member [Obsolete Code: Use H] (HUGH)
Hughes Beds (-946)
Alternative Name(s): none recorded or not applicable
Reference Section  There is no designated type area, the Member being named after the basal coal, the Hughes Seam of the Swansea - Gower area of the South Wales Coalfield. A reference section is provided by exposures in a disused mineral railway cutting at Tir-Evan-Llwyd, southeast of Neath, in which 7.6m of "Pennant" sandstone contains lenticular mudstone beds. Barclay, in prep. 
Barclay, W J, in prep. Geology of the country around Swansea. Sheet Description of the British Geological Survey. 1:50 000 Sheet 247 Swansea (England and Wales). 
Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. 
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:
E247 E232 E231 E230 E229 E246