The BGS Lexicon of Named Rock Units — Result Details

Llewelyn Volcanic Group
Computer Code: LLV Preferred Map Code: LlV
Status Code: Full
Age range: Caradoc Epoch (O4) — Caradoc Epoch (O4)
Lithological Description: Acid ash-flow tuffs, with some basic and intermediate volcanic rocks. Note: see also the descriptions of the Capel Curig Volcanic, Conwy Rhyolite, Braich Tu Du, Gwern Gof, Foel Fras and Foel Grach formations.
Definition of Lower Boundary: Where one of the constituent formations rests on sediments of the undivided Nant Ffrancon Group; at base of the Capel Curig Volcanic Formation.
Definition of Upper Boundary: At top of Capel Curig Volcanic Formation. d tuffs of the Cwm Eigiau Formation.
Thickness: 1400m approx.
Geographical Limits: Northern and central Snowdonia.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Between Carnedd Dafydd and Conwy Mountain. Note: see also stratotypes for Capel Curig Volcanic, Conwy Rhyolite, Braich Tu Du, Gwern Gof, Foel Fras and Foel Grach formations. 
Reference(s):
Howells, M F and Smith, M. 1997. The geology of the country around Snowdon. Memoir of the British Geological Survey, Sheet 119 (England and Wales). 
Ball, T K and Merriman, R J, 1989. The petrology and geochemistry of Ordovician Llewelyn Volcanic Group, Snowdonia, North Wales. British Geological Survey Research Report, SG/89/1. 
Smith, B and George, T N, 1961. North Wales. British Regional Geology. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E106 E119 E094
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