The BGS Lexicon of Named Rock Units — Result Details

Cwm Barn Formation

Computer Code: CWN Preferred Map Code: Cwn
Status Code: Full
Age range: Telychian Age (ST) — Telychian Age (ST)
Lithological Description: Interbedded conglomerates, sandstones and turbidite mudstones with some thick units of pebbly mudstone. Subordinate thin laminated or burrowed hemipelagites.
Definition of Lower Boundary: Taken at base of first pebbly mudstone or conglomerate above the mudstone dominated sequence of the Rhayader Pale Shales.
Definition of Upper Boundary: Gradational but taken at base of mudstone dominated sequence with sparse thin turbidite sandstones of the Caeran Mudstones.
Thickness: Up to 150m.
Geographical Limits: Central Wales, northwest flank of Tywi Anticline.
Parent Unit: Not Available (!)
Previous Name(s): Cwmbarn Member (-3341)
Alternative Name(s): none recorded or not applicable
Type Section  Old Quarry at Cwmbarn, 120m southwest of Brynscolfa, Rhayader. 
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used: