The BGS Lexicon of Named Rock Units — Result Details
Brithion Formation
Computer Code: | BRT | Preferred Map Code: | notEntered |
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Status Code: | Full | ||
Age range: | Llanvirn Series (OE) — Llanvirn Series (OE) | ||
Lithological Description: | Volcanic breccias and felsic, welded ash-flow tuffs. | ||
Definition of Lower Boundary: | Sharp but conformable contact with underlying mudstones of the Aran Volcanic Group. | ||
Definition of Upper Boundary: | Conformably overlain by undivided siltstones of the Aran Volcanic Group. | ||
Thickness: | To 75m, but the formation wedges out southwestwards and northwards. | ||
Geographical Limits: | Harlech district. | ||
Parent Unit: | Aran Volcanic Group (AVG) | ||
Previous Name(s): | Brithion Tuff [Obsolete Name and Code: Use BRT]
(-4502)
Creigiau Brithion Formation [Obsolete Name and Code: Use BRT] (-2641) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Partial Type Section | Crags to the northwest side of Craigiau Brithion. Dunkley, P N. 1978. | ||
Reference(s): | |||
Dunkley, P N. 1978. The geology of the southwestern part of the Aran Range, Merioneth, with particular reference to the igneous history. Unpublished Ph.D. Thesis. University of Wales, Aberystwyth. | |||
Allen, P M, and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 [England and Wales]. [London: HMSO.] 112pp. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E136 E149 E135 |