The BGS Lexicon of Named Rock Units — Result Details

Penderyn Oolite Member

Computer Code: PDO Preferred Map Code: notEntered
Status Code: Full
Age range: Asbian Substage (CR) — Asbian Substage (CR)
Lithological Description: Pale grey, massive ooidal limestone, lenticular sandstone, rubbly limestone and shelly mudstone, locally with coal streaks and seatearth, at top.
Definition of Lower Boundary: The base is placed at the junction of pale grey, massive ooidal limestone of the Penderyn Oolite Member with calcereous sandstone of the underlying Honeycombed Sandstone Member, or with the dark grey, bituminous skeletal/peloidal grainstones/packstones/wackestones of the Dowlais Limestone Formation.
Definition of Upper Boundary: The top is placed at the top of ooidal limestone or at the top of lenticular sandstone and mudstone of the Member, above which dark grey, cyclic shelly and crinoidal grainstones of the undivided part of the Oxwich Head Limestone Formation enter.
Thickness: 13m at type locality, 25 to 33m elsewhere.
Geographical Limits: North crop of South Wales Coalfield, extending eastwards from near Crwbin [SN 467 125] to near Ponsticill [SO 072 112].
Parent Unit: Oxwich Head Limestone Formation (OHL)
Previous Name(s): Llandyfan Limestone [Obsolete Name and Code: Use PDO] (-4247)
Light Oolite [Obsolete Name and Code: Use PDO] (-1756)
Alternative Name(s): none recorded or not applicable
Type Section  Penderyn Quarry, near the village of Penderyn, Powys. The member is 13m thick here, but attains 25 to 33m elsewhere along its outcrop. George et al., 1976; Barclay et al., 1988. 
George, T N, Johnson, G A L, Mitchell, M, Prentice, J E, Ramsbottam, W H C, Sevastopulo, G D and Wilson, R B. 1976. A correlation of the Dinantian rocks of the British Isles. Special Report of the Geological Society of London, No 7. 
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). 
Robertson, T. 1932. Geology of the South Wales Coalfield, Part V, the country around Merthyr Tydfil, 2nd edition. Memoir of the Geological Survey of Great Britain, Sheet 231. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: