The BGS Lexicon of Named Rock Units — Result Details

Llyn Conwy Formation [Obsolete Name And Code: Use AFM]

Computer Code: LLNC Preferred Map Code: LlyC
Status Code: Index Level
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Acidic ash-flow tuff, mainly non-welded.
Definition of Lower Boundary: On mudstones of undivided Nant Ffrancon Group.
Definition of Upper Boundary: Below mudstones of undivided Nant Ffrancon Group.
Thickness: Up to about 500m
Geographical Limits: Northeast flanks of Harlech Dome.
Parent Unit: Nant Ffrancon Subgroup (NFR)
Previous Name(s): Aran Fawddwyf Formation (-4764)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Llyn Conwy, Snowdonia. 
Reference(s):
Lynas, B D T, 1973. The Cambrian and Ordovician rocks of the Migneint area, North Wales. Journal of the Geological Society, London, Vol.129, 481-503. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E120 E119