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 [Obsolete Name and Code: Use ARL]
(-2567)
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Alternative Name(s): |
none recorded or not applicable
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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
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