The BGS Lexicon of Named Rock Units — Result Details

Menai Straits Formation

Computer Code: MEST Preferred Map Code: notEntered
Status Code: Full
Age range: Asbian Substage (CR) — Asbian Substage (CR)
Lithological Description: Varied sequence of breccias, conglomerates, sandstones, siltstones and silty mudstones including veriegated yellow and purple "loam". Spherical ferruginous (goethite) ooids are abundant in both the mudstones and the mudstone matrix of the breccias. The formation records the accumulation of late Asbian terrestrial screes and alluvial deposits along the local margin of the Dinantian carbonate platform. The goethite ooids are the product of pedogenic processes.
Definition of Lower Boundary: Rests unconformably on Ordovician rocks (Nant Ffrancon Formation) and Precambrian rocks of the Monian Supergroup.
Definition of Upper Boundary: Conformably overlain by thick-bedded limestones of the Loggerheads Limestone Formation.
Thickness: To 43m
Geographical Limits: Menai Straits area (SH 5571), North Wales.
Parent Unit: Not Applicable (-)
Previous Name(s): Bridges Sandstone Formation (-1063)
Basement Beds Formation [Obsolete Name And Code: See Supplementary Information] (BED)
Fanogle Sandstone (-4790)
Menei Straits Formation (-1689)
Alternative Name(s): none recorded or not applicable
Type Section  Coastal cliffs between the Britannia Bridge (SH 5425 7090) and the Menai Suspension Bridge (SH 5575 7125). Greenly, 1928. 
Howells M F, Reedman A J and Leveridge B E. 1985. Geology of the country around Bangor: Explanation for 1:50 000 geological sheet 106 (England and Wales). British Geological Survey Sheet Explanation. [London: HMSO.] 34pp. 
Greenly, E. 1928. The Lower Carboniferous rocks of the Menaian region of Carnarvonshire: their petrology, succession and physiography. Quarterly Journal of the Geological Society of London, Vol.84, 382-439. 
Waters, C N, Waters, R A, Barclay, W J, and Davies, J R. 2009. Lithostratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/09/01. 184pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: