The BGS Lexicon of Named Rock Units — Result Details

Llanbedrog Volcanic Group
Computer Code: LIG Preferred Map Code: LVG
Status Code: Full
Age range: Caradoc Epoch (O4) — Caradoc Epoch (O4)
Lithological Description: Basaltic trachyandesite-rhyodacite lavas and tuffs, with some ash flow tuffs and minor amounts of reworked sandstones, siltstones and conglomerates.
Definition of Lower Boundary: Underlain by sandstones and siltstones of the Dwyfach Formation.
Definition of Upper Boundary: Overlain by mudstones and slates of the Nod Glas Formation.
Thickness: From about 300 to about 1100m
Geographical Limits: Northwest Wales.
Parent Unit: Gwynedd Supergroup (GWYN)
Previous Name(s): Mynytho Volcanic Group (MYV)
Llanbedrog Igneous Group (-364)
Llanbedrog Volcanic Series (-1658)
Llanbedrog Ignimbrites (-4162)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Around village of Llanbedrog, Llyn Peninsula. 
Reference(s):
Williams, A and others, 1972. A correlation of Ordivician rocks in the British Isles. Geological Society of London Special Report No.3. 
Matley, C A, 1938. The geology of the country around Pwllheli, Llanbedrog and Madryn, south-west Caernarvonshire. Quarterly Journal of the Geological Society of London, Vol.94, 567. 
Young, T P, Gibbons, W and McCarroll, D. 2002. Geology of the country around Pwllheli. Memoir of the British Geological Survey, Sheet 134 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E134
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