The BGS Lexicon of Named Rock Units — Result Details
Gwna Group
Computer Code: | NGW | Preferred Map Code: | notEntered |
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Status Code: | Full | ||
Age range: | Ediacaran Period (AD) — Comley Series (EC) | ||
Lithological Description: | Grit, phyllite, quartzite, limestone, jasper, graphitic phyllite, spilitic pillow lavas and tuffs. | ||
Definition of Lower Boundary: | Drawn at the base of the Gwna Group where it rests conformably on the Church Bay Tuffs. | ||
Definition of Upper Boundary: | Drawn at the conformable upward passage of the Gwna Group to the base of the Fydlyn Group: diabase passing into chlorite epidote schist. | ||
Thickness: | Probably several hundred metres. | ||
Geographical Limits: | Anglesey, North Wales. | ||
Parent Unit: | Monian Supergroup (N) | ||
Previous Name(s): | Fydlyn Group [Obsolete Name And Code: See NGW]
(NFD)
Fydlyn Felsitic Beds [Obsolete Name And Code: See NGW] (NFFF) Gwna Melange Formation (A) [Obsolete Name And Code: See NGW] (GWNM) Gwna Melange Formation (B) [Obsolete Name And Code: See NGW] (NGWM) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Area | Afon Gwna, near Bodorgan station, Anglesey. | ||
Reference(s): | |||
Gibbons, W and Harris, A L. 1994. A revised correlation of Precambrian rocks in the British Isles. Geological Society of London Special Report, No.22. | |||
Shackleton, R M. 1975. Precambrian rocks of Wales. 76-83 in A correlation of Precambrian rocks in the British Isles. Harris, A L, and others (editors). Geological Society of London Special Report No. 6. | |||
Greenly, E. 1919. Geology of Anglesey. Memoir of the Geological Survey, UK. | |||
Gibbons, W and Ball, M J. 1991. Discussion on Monian Supergroup srtatigraphy in north-west Wales. Journal of the Geological Society, London, Vol. 148, 5-8. | |||
Horak, J M and Gibbons, W. 2000. Anglesey and the Lleyn Peninsula (Llyn). 145-179 in Carney, J (editor), Precambrian rocks of England and Wales. Geological Consrvation Review Series, 20. [Peterborough: Joint Nature Conservation Committee.] | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
none recorded or not applicable |