The BGS Lexicon of Named Rock Units — Result Details

Llanrian Volcanic Formation

Computer Code: LVG Preferred Map Code: LV
Status Code: Full
Age range: Abereiddian Stage (O2) — Abereiddian Stage (O2)
Lithological Description: Rhyolitic tuffs with interbedded mudstone.
Definition of Lower Boundary: Drawn at the base of the Llanrian Volcanic Group where it rests conformably upon the Tetragraptus Shales.
Definition of Upper Boundary: Drawn at the conformable upward passage of the Llanrian Volcanic Group where it cross-cuts the Didymograptus Bifidus Beds.
Thickness: 250m.
Geographical Limits: 1:50 000 Sheet 209 (St Davids). Llanrian, Pembrokeshire, south-west Wales.
Parent Unit: Fishguard Volcanic Group (FIV)
Previous Name(s): Llanrian Volcanic Group (-382)
Llanrian Volcanic Series (-4775)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The Llanrian Syncline, Llanrian, between St David's Head and Strumble Head. 
Reference(s):
Williams, A and others, 1972. A correlation of Ordivician rocks in the British Isles. Geological Society of London Special Report No.3. 
Cox, A H. 1915. The geology of the district between Abereiddy and Abercastle (Pembrokeshire). Quarterly Journal of the Geological Society, vol.71, p.273-342. 
Hughes C P, and others. 1982. Abereiddi Bay and the adjacent coast. "In" Bassett, M G. (Editor). Geological excursions in Dyfed, south-west Wales. p.51-63. 
Cox, A H, and Jones, O T. 1913. The geology of the district between Abereiddy and Pencaer, Pembrokeshire. British Academy for the Advancement of Science Report, Birmingham 484. 
Elsden, J V. 1905. On the igneous rocks occcurring between St David's Head and Strumble Head. (Pembrokeshire). Quarterly Journal of the Geological Society. Vol 91, p.580. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E209