The BGS Lexicon of Named Rock Units — Result Details

Pen-Plaenau Siltstone Formation

Computer Code: PEPL Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Soudleyan Substage (OY) — Soudleyan Substage (OY)
Lithological Description: Mudstones and interbedded thinly laminated, ripple-marked siltstones and sandstones.
Definition of Lower Boundary: Conformable passage from underlying Cwm Clwyd Tuff Formation, the boundary being taken at the base of the epiclastic sandstones and mudstones that overlie the highest tuff of the latter formation.
Definition of Upper Boundary: Conformable upward passage from mudstones and siltstones into flaggy volcaniclastic sandstones of the Swch Gorge Tuff Formation.
Thickness: 150 to 350m
Geographical Limits: none recorded or not applicable
Parent Unit: Not Available (!)
Previous Name(s): Teirw Beds [Obsolete Name And Code: Use TSI] (TWB)
Alternative Name(s): none recorded or not applicable
none recorded or not applicable
Brenchley, P J, 1978. The Caradocian rocks of the North and West Berwyn Hills. Geological Journal, Vol.13, 137-164. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E136 E120