The BGS Lexicon of Named Rock Units — Result Details

Roch Volcanic Formation

Computer Code: RRH Preferred Map Code: RRh
Status Code: Pending Upgrade
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Fine-grained, highly silicified, pale greenish - blue rhyolites weathering white; thin bands of blue - green and pale mauve banded flinty tuffs with interbedded sediments.
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: Not seen, but generally faulted.
Thickness: At least 180m
Geographical Limits: Pembrokeshire.
Parent Unit: Not Available (!)
Previous Name(s): Roch Rhyolitic Series (-3624)
Roch Rhyolitic Group [Obsolete Name And Code: Use RRH] (PRR)
Trefgarn Rhyolitic Series (-1774)
Alternative Name(s): none recorded or not applicable
Type Area  The area near Treffgarne, Cleddau Valley, Pembrokeshire (Dyfed). 
Type Section  Cleddau Valley, Pembrokeshire, between Spittal Brook and Ford. Thomas, H H, and Cox, A H. 1924. 
Harris, A L and others, 1973. A correlation of the Pre-Cambrian rocks in the British Isles. Geological Society of London Special Report No 6. 
Thomas, H H, and Cox, A H. 1924. The Volcanic Series of Trefgarn, Roch and Ambleston (Pembrokeshire). Quarterly Journal of the Geological Society, Vol.80, p.520-548. 
Thomas, H H and Jones, O T, 1912. On the Pre-Cambrian and Cambrian rocks of Brawdy, Haycastle and Brimaston, (Pembrokeshire). Quarterly Journal of the Geological Society of London, Vol.68, 374-401. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: