The BGS Lexicon of Named Rock Units — Result Details

Ty-Nant Limestone Formation

Computer Code: TNL Preferred Map Code: TnL
Status Code: Full
Age range: Asbian Substage (CR) — Asbian Substage (CR)
Lithological Description: Regular cyclic alternations of dark grey bioclastic limestone and porcellaneous limestone (birdseye micrite).
Definition of Lower Boundary: At junction with underlying Basement Beds.
Definition of Upper Boundary: At junction with overlying Eglwyseg Limestone Formation, which comprises sedimentary cycles of calcareous shale, cross bedded biosparite and massive pale grey biosparite.
Thickness: c.115m
Geographical Limits: Llangollen-Minera district, east Wales.
Parent Unit: Not Entered (?)
Previous Name(s): Lower Brown Limestone [Obsolete Name And Code: See FOF, LEEL, LNML, TNL] (LBRL)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Due north of Ty-nant Farmhouse. 
Reference(s):
Somerville, I D, 1979. Minor sedimentary cyclicity in Late Asbian (Upper D1) Limestones in the Llangollen district of North Wales. Proceedings of the Yorkshire Geological Society, Vol.42, p.317-341. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E121