The BGS Lexicon of Named Rock Units — Result Details

Brownstone Group [Obsolete: use BRS]

Computer Code: BRG Preferred Map Code: notEntered
Status Code: Index Level
Age range: Pragian Age (DP) — Emsian Age (DE)
Lithological Description: [Obsolete: use BRS] Red brown and purple sandstones with interbedded red siltstones and mudstones.
Definition of Lower Boundary: Drawn at the base of Brownstones where sandstones conformably rest upon sandstones of the Sewni Beds, the boundary being transitional with a colour change from green to red.
Definition of Upper Boundary: Drawn at the conformable upward passage of the Brownstones where they are unconformably overlain with slight discordance by the Plateau Beds.
Thickness: 400 metres approx.
Geographical Limits: From Carmarthenshire and Pembroke across Wales to the Brecon Beacons and Welsh Borders.
Parent Unit: none recorded or not applicable
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  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). 
Strahan, A, Gibson, W, and Cantrill, T C. 1904. The geology of the South Wales Coalfield, Part V. The country around Merthyr Tydfil. First Edition. Memoir of the Geological Survey of Great Britain. Sheet 231 (England and Wales). 
Allen, J R L. 1977. Wales and the Welsh Borders. 40-54 in House, M R et al. A correlation of Devonian rocks in the British Isles. Geological Society, London, Special Report No. 7. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E249 E246 E234 E231 E250