The BGS Lexicon of Named Rock Units — Result Details

Craig y Ffynnon Formation

Computer Code: CFF Preferred Map Code: notEntered
Status Code: Full
Age range: Aurelucian Stage (OJ) — Burrellian Stage (OK)
Lithological Description: Acidic ash-flow tuff.
Definition of Lower Boundary: Overlies siltstone and basalt at the top of the Benglog Formation.
Definition of Upper Boundary: Overlain by the Pistyllion Formation and the Aran Fawddwy Formation.
Thickness: To 212 m.
Geographical Limits: none recorded or not applicable
Parent Unit: Aran Volcanic Group (AVG)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Craig y Ffynnon [SH 832 195]. 
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. 
Allen, P M, and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 [England and Wales]. [London: HMSO.] 112pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E136 E135