The BGS Lexicon of Named Rock Units — Result Details

Tal Y Fan Volcanic Formation

Computer Code: TYFV Preferred Map Code: TF
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Basalt lavas and pillow breccias with hyaloclastite, basaltic tuff; mudstone intercalations.
Definition of Lower Boundary: Rests on mudstones associated with the Lower Crafnant Volcanic Formation.
Definition of Upper Boundary: Overlain by part of the Nod Glas (= Cadnant Shales).
Thickness: 500m
Geographical Limits: Restricted to the area of Tal y Fan, 5km north west of Dolgarrog.
Parent Unit: Snowdon Volcanic Group (SV)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Tal y Fan. 
Reference(s):
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. 
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E106 E094