The BGS Lexicon of Named Rock Units — Result Details

Tyn-Y-Glyn Mudstone Formation [Obsolete Name And Code: See NOG]

Computer Code: TYG Preferred Map Code: TYG
Status Code: Index Level
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Black pyritous graptolitic mudstone.
Definition of Lower Boundary: Base succeeds green calcareous volcaniclastic sandstones of the Gelli Grin Calcareous Ash Formation and laterally the Upper Crafnant Volcanic Formation acid tuffs.
Definition of Upper Boundary: Unconformably overlain by bioclastic limestone - Rhiwlas Limestone.
Thickness: 2.5m thick in type section; lateral variations - 0-25m.
Geographical Limits: Not defined.
Parent Unit: Not Entered (?)
Previous Name(s): Tyn-Y-Glyn Mudstone Member (-3739)
Alternative Name(s): none recorded or not applicable
Type Area  Corwen, Sheet 120. 
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 Unpublished PhD Thesis, University of Cambridge. 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: