The BGS Lexicon of Named Rock Units — Result Details

Penamnen Tuff Formation

Computer Code: PNT Preferred Map Code: PnT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Felsic tuffs with siltstone intercalations.
Definition of Lower Boundary: Conformable within the upper part of the Nant Ffrancon Subgroup.
Definition of Upper Boundary: Conformable within the upper part of the Nant Ffrancon Subgroup.
Thickness: To 10m
Geographical Limits: Eastern central Snowdonia.
Parent Unit: Nant Ffrancon Subgroup (NFR)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Gwern Gof Tuff
Stratotypes:
Type Section  Head of Cwm Penamnen. Howells, M F, Francis, E H, Leveridge, B E and Evans, C D R. 1978. 
Reference(s):
Howells, M F and Smith, M. 1997. Geology of the country around Snowdon. Memoir of the British Geological Survey, Sheet 119 (England and Wales). (London: The Stationery Office). 104pp. 
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. 
Howells, M F, Francis, E H, Leveridge, B E and Evans, C D R, 1978. Classical areas of British Geology. Capel Curig and Betws-y-Coed. Description of 1:25 000 Sheet SH75. London: HMSO for Institute of Geological Sciences. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E119