The BGS Lexicon of Named Rock Units — Result Details
Snowdon Volcanic Group
| Computer Code: | SV | Preferred Map Code: | SVG |
|---|---|---|---|
| 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): | Crafnant Volcanic Group [Obsolete Name And Code: See SV]
(CV)
Snowdon Volcanic Series [Obsolete Name and Code: Use SV] (-4910) |
||
| 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): | |||
| 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. | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E119 E106 E107 | |||