The BGS Lexicon of Named Rock Units — Result Details

Argoed Limestone Member

Computer Code: ARL Preferred Map Code: ArL
Status Code: Full
Age range: Holkerian Substage (CQ) — Holkerian Substage (CQ)
Lithological Description: Thin- to medium-bedded, fine- to coarse-grained crinoidal skeletal packstones with a bed of grey calcareous mudstone at the base. Dolmitized along the southeast crop of the South Wales Coalfield. Deposited in an offshore platform setting and representing the basal Holkerian transgression.
Definition of Lower Boundary: Taken at the base of a bed of grey calcareous mudstone, overlain by thin- to medium-bedded, fine- to coarse-grained crinoidal skeletal packstones, that overlies the clay palaeosol capping the underlying Cefnyrhendy Oolite Member, or the top of the underlying palaeokarstic surface if the clay palaeosol is absent.
Definition of Upper Boundary: Gradational boundary in which the top is taken at the first bed of ooidal grainstone of the Cornelly Oolite Formation above the crinoidal skeletal packstones of the Member.
Thickness: 10m
Geographical Limits: Northern Vale of Glamorgan [ST 00 74]. Passes southwards into the High Tor Limestone Formation.
Parent Unit: Cornelly Oolite Formation (CNLL)
Previous Name(s): Bute Limestone (-2567)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Argoed Isha Quarry, 150m south of Argoed, Llanharry, Vale of Glamorgan. Entire Member exposed, comprising a basal mudstone overlain by thin to medium bedded skeletal packstones. Contacts with underlying Cefnyrhendy Oolite Member and overlying oolitic limestones of the Cornelly Oolite Formation exposed. 
Reference(s):
Wilson, D, Davies, J R, Fletcher, C J N, and Smith, M. 1990. The Geology of the South Wales Coalfield, part VI the Country around Bridgend. Memoir of the British Geological Survey, 1:50 000 Geological Sheets 261 and 262 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E262