The BGS Lexicon of Named Rock Units — Result Details

Brownstones Formation

Computer Code: BRS Preferred Map Code: Brs
Status Code: Full
Age range: Lochkovian Age (DO) — Emsian Age (DE)
Lithological Description: Red, brown and purple fluvial sandstones with red mudstone interbeds.
Definition of Lower Boundary: (1) Where sandstones become dominant over mudstone in the underlying St Maughans Formation. (2) At colour change from predominantly green sandstone of the Senni Beds below, to red of the Brownstones.
Definition of Upper Boundary: Where Upper Devonian or Lower Carboniferous beds overlie the Brownstones unconformably.
Thickness: To 1200m
Geographical Limits: South Wales and Welsh Borderlands, as far north as the Clee Hills.
Parent Unit: Brecon Subgroup (BREC)
Previous Name(s): Brownstones (-2640)
Red Sandstone Group (-671)
Brownstone Group [Obsolete Name And Code: See BRS] (BRG)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Black Mountains and Brecon Beacons. 
Reference Section  Wilderness Quarry, Forest of Dean. 
Reference Section  North face of Pen-y-fan. 
Reference(s):
Waters, R A and Lawrence, D J D. 1987. Geology of the South Wales Coalfield - Part III: the country around Cardiff. Memoir of the British Geological Survey, Sheet 263. (England and Wales). 
Barclay, W J, Jackson, D I, Mitchell, M, Owen, B, Riley, N J, White, D E, Strong, G E and Monkhouse, R A. 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny. Memoir of the British Geological Survey. 
Allen, J R L, 1974a. The Devonian rocks of Wales and the Welsh Borderland. 47-84 in Owen, T R (Editor). The Upper Palaeozoic and post-Palaeozoic rocks of Wales. Cardiff. University of Wales Press. 
Allen, J R L, Halstead, L B and Turner, S, 1968. Dittonian ostracoderm fauna from the Brownstones of Wilderness Quarry, Mitcheldean, Gloucestershire. Proceedings of the Geological Society, No.1649, 141-153. 
Symonds, W S, 1872. Records of the Rocks. [London.] 
Welch, F B A and Trotter, F M. 1961. Geology of the country around Monmouth and Chepstow. Explanation of one-inch geological sheets 233 and 250. Memoir of the Geological Survey of Great Britain. 
Allen, J R L, 1974b. Source rocks of the Lower Old Red Sandstone; exotic pebbles from the Brownstones, Ross-on-Wye, Hereford and Worcester. Proceedings of the Geologists' Association, Vol.85, 493-510. 
Barclay, W J, Taylor, K and Thomas, L P, 1988. Geology of the South Wales Coalfield, Part V, the country around Merthyr Tydfil. Third Edition. Memoir of the British Geological Survey, Sheet 231 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E213 E246 E216 E263 E262 E234 E232 E230 E231 E233 E181 E182 E180 E197 E214 E215 E229 E212