The BGS Lexicon of Named Rock Units — Result Details

Gwern Gof Tuff Formation

Computer Code: GGTU Preferred Map Code: GGT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Non- to weakly-welded acidic ash-flow tuffs with cross-laminated, well-bedded tuffaceous sandstone derived from the tuffs.
Definition of Lower Boundary: Rests on sandstones and mudstones intercalated in the Llewelyn Volcanic Group above the Foel Fras Volcanic Complex.
Definition of Upper Boundary: Underlies sandstone and siltstone in the Llewelyn Volcanic Group that underlies the Capel Curig Volcanic Formation..
Thickness: About 30m
Geographical Limits: East of Carnedd Dafydd to east of Tryfan.
Parent Unit: Llewelyn Volcanic Group (LLV)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  East of Tryfan. 
Reference(s):
Howells, M F, Reedman, A J and Campbell, S D G, 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). (London: HMSO for the British Geological Survey). 
Howells M F, Reedman A J and Leveridge B E. 1985. Geology of the country around Bangor: Explanation for 1:50 000 geological sheet 106 (England and Wales). British Geological Survey Sheet Explanation. [London: HMSO.] 34pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E106