The BGS Lexicon of Named Rock Units — Result Details

Eidda Formation [Obsolete Name And Code: Use CEI]

Computer Code: EI Preferred Map Code: EI
Status Code: Index Level
Age range: Longvillian Substage (OL) — Longvillian Substage (OL)
Lithological Description: Yellow-grey to grey and greenish-grey sandy-siltstones, fine-grained sandstones and subordinate siltstones. Includes Blaen Eidda Member at its base and a laharic debris flow towards its top. It is highly fossiliferous.
Definition of Lower Boundary: Volcaniclastic green fossiliferous sandstone (Blaen Eidda Member) overlies grey siltstones and fine-grained sandstones of the Carn-y-Parc Formation.
Definition of Upper Boundary: Overlain by ash-flow tuff of the Lower Crafnant Volcanic Formation.
Thickness: 50 metres. Lateral variations 0-50 metres.
Geographical Limits: Not defined.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Corwen, Sheet 120. 
Reference(s):
Campbell, S D G. 1983. The geology of an area between Bala and Betws-y-Coed, North Wales. Unpublished PhD Thesis, University of Cambridge. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E120