The BGS Lexicon of Named Rock Units — Result Details

Allt Ddu Mudstones Formation [Obsolete Name And Code: Upper Part Of CSW]

Computer Code: ADM Preferred Map Code: ADM
Status Code: Index Level
Age range: Soudleyan Substage (OY) — Soudleyan Substage (OY)
Lithological Description: Silty mudstones and fine-grained siltstones.
Definition of Lower Boundary: Overlies Glyn Gower Siltstones, or Frondderw Tuff where this is developed.
Definition of Upper Boundary: Overlain by Pont-y-ceunant Ash at base of Gelli-Grin Calcareous Ashes.
Thickness: c.400m.
Geographical Limits: none recorded or not applicable
Parent Unit: Not Entered (?)
Previous Name(s): Allt Ddu Mudstones (-3155)
Alternative Name(s): Ceiswyn Formation
Stratotypes:
none recorded or not applicable
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 Unpublished PhD Thesis, University of Cambridge. 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 E136