The BGS Lexicon of Named Rock Units — Result Details

Linney Head Formation

Computer Code: LHD Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Chadian Substage (CI) — Chadian Substage (CI)
Lithological Description: Thin- to thick-bedded dark grey crinoidal wackestones with abundant chert beds interbedded with mudstones and nodular limestones. Packstones present in uppermost part. Deposited in a distal ramp setting.
Definition of Lower Boundary: Taken at junction of massive dolomitised reef limestones of the Berry Slade Formation and the overlying dark limestones with thin mudstones and cherts of the Formation. Where the top of the Berry Slade Formation is in flank facies, the boundary is imprecise but taken at the increase in chert content at the base of the Linney Head Formation.
Definition of Upper Boundary: Taken at sharp junction between the dark limestones, cherts and mudstones of the Formation and the overlying thick-bedded coarsely crinoidal limestones of the Hobbyhorse Bay Limestone Formation.
Thickness: 30m at type section in southwest Pembrokeshire.
Geographical Limits: Castlemartin area [SR 95 98], southwest Pembrokeshire. Relationship to coeval Gully Oolite to north unknown.
Parent Unit: Pembroke Limestone Group (PEMB)
Previous Name(s): Linney Head Beds (-1026)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Sea cliffs at Linney Head, Castlemartin, southwest Pembrokeshire. Entire unit exposed and comprises crinoidal wackestones and mudstones with abundant cherts. Contacts with underlying Berry Slade Formation and overlying Hobbyhorse Bay Formation exposed. 
Reference(s):
Simpson, J and Kalvoda, J. 1987. Sedimentology and foraminiferal biostratigraphy of the Arundian [Dinantian] stratotype. 226-237 in Micropalaeontology of carbonate enviroments. Hart, M B [editor]. British Micropalaeontological Society series. [Chicester: Ellis Horward Ltd.] 
Dixon, E E L, 1921. The Geology of the South Wales Coalfield, Part XIII , the country around Pembroke and Tenby, being an account of the region comprised in sheets 244 and 245. Memoir of the Geological Survey of Great Britain (HMSO). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E244 E245