The BGS Lexicon of Named Rock Units — Result Details
Snowdon Volcanic Group
Computer Code: | SV | Preferred Map Code: | SVG |
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Status Code: | Full | ||
Age range: | Caradoc Series (O4) — Caradoc Series (O4) | ||
Lithological Description: | Acidic ash-flow tuffs with a major basaltic division. | ||
Definition of Lower Boundary: | At base of volcanic formations resting on sedimentary rocks of Cwm Eigiau Formation. | ||
Definition of Upper Boundary: | At base of Cadnant Shales Formation. | ||
Thickness: | Not exceeding 1800 metres. | ||
Geographical Limits: | Snowdonia. | ||
Parent Unit: | Gwynedd Supergroup (GWYN) | ||
Previous Name(s): | Snowdon Volcanic Series [Obsolete Name and Code: Use SV]
(-4910)
Crafnant Volcanic Group [Obsolete Name And Code: See SV] (CV) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Area | Snowdon. Note: see also stratotypes of constituent (Upper Rhyolitic Tuff; Lower Rhyolitic Tuff; Bedded Pyroclastic; Pitts Head Tuff; Dolgarrog Volcanic; Upper, Middle and Upper Crafnant Volcanic; Tal y Fan; Yr Arddu Tuffs) volcanic formations. | ||
Reference(s): | |||
Howells, M F, Reedman, A J and Campbell, S D G, 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). (London: HMSO for the British Geological Survey). | |||
Shackleton, R M. 1959. The stratigraphy of the Moel Hebog district between Snowdon and Tremadoc. Liverpool and Manchester Geological Journal, Vol.2, 216-252. | |||
Williams, D, 1930. The geology of the country between Nant Peris and Nant Ffrancon (Snowdonia). Quarterly Journal of the Geological Society, Vol.86, p.193, 202-212, map. | |||
Williams, H and Bulman, O M B, 1931. The geology of the Dolwyddelan Syncline, North Wales. Quarterly Journal of the Geological Society of London, Vol.87, p.429, 434-443. | |||
Rast, N and others, 1958. Sub-Aerial volcanicity in Snowdonia. Nature. London, Vol.181, p.508. | |||
Oliver, R L, 1954. Welded tuffs in the Borrowdale Volcanic Series, English Lake District, with a note on similar rocks in Wales. Geological Magazine, Vol.91, p.478. | |||
Williams, H. 1927. The geology of Snowdon, North Wales. Quarterly Journal of the Geological Society, Vol.83, p.353, 363-389. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E119 E106 E107 |