The BGS Lexicon of Named Rock Units — Result Details

BROWNSTONES FORMATION
Computer Code: BRS  Status Code: FORMAL, NATIONAL 
Preferred Map Code: Brs 
Age or Age Range: [ DO ] LOCHKOVIAN  to [ DE ] EMSIAN 
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: Parent Unit Code:
LOWER OLD RED SANDSTONE  LORS
Previous Name(s): Previous Code(s):
RED SANDSTONE GROUP   
BROWNSTONE GROUP  BRG 
BROWNSTONES   
Alternative Name(s):
none recorded or not applicable
Stratotypes:
Reference Section  North face of Pen-y-fan. 
Reference Section  Wilderness Quarry, Forest of Dean. 
Type Area  Black Mountains and Brecon Beacons. 
Reference(s):
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). 
Waters, R A and Lawrence, D J D, 1987. Geology of the South Wales Coalfield, Part III, the country around Cardiff. 3rd edition. Memoir of the British Geological Survey, Sheet 263 [England and Wales]. 
Symonds, W S, 1872. Records of the Rocks. [London.] 
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, 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, 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny. Memoir of the British Geological Survey, Sheet 232, (England and Wales). 
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. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  263
E  262
E  180
E  232
E  216
E  234
E  230
E  214
E  181
E  231
E  197
E  212
E  246
E  233
E  215
E  182
E  213
E  229

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