The BGS Lexicon of Named Rock Units — Result Details

Trwyn Cam Member

Computer Code: TNC Preferred Map Code: TnC
Status Code: Pending Upgrade
Age range: Fennian Stage (OF) — Fennian Stage (OF)
Lithological Description: Grey, bioturbated, fine-grained laminated sandstones and subordinate siltstones, with large calcareous nodules that weather out. A structureless grey siliceous siltstone, possible representing a tuff, occurs in the upper part of the sequence.
Definition of Lower Boundary: Conformable and gradational with dark grey siltstones that form the main part of the Wig Bach Formation.
Definition of Upper Boundary: Conformably overlain by dark grey siltstones of the Wig Bach Formation.
Thickness: 35m
Geographical Limits: Not yet recorded.
Parent Unit: Wig Bach Formation (WGB)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Coastal cliff section along 200m of the west side of Aberdaron Bay, south of the headland of Trwyn Cam. Gibbons, W and McCarroll, D. 1993. 
Reference(s):
Rushton, A W A and Howells, M F. 1998. Stratigraphical framework for the Ordovician of Snowdonia and the Lleyn Peninsula. British Geological Survey Research Report, RR/99/08. 
Gibbons W and McCarroll D. 1993. Geology of the country around Aberdaron, including Bardsey Island. Memoir of the British Geological Survey, Sheet 133 (England and Wales). (London: H.M.S.O.). 88pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable