The BGS Lexicon of Named Rock Units — Result Details

Serw Formation [Obsolete Name And Code: See Supplementary Information]

Computer Code: SER Preferred Map Code: SER
Status Code: Index Level
Age range: Abereiddian Stage (O2) — Abereiddian Stage (O2)
Lithological Description: Mudstone with thick irregular lenses of laharic breccias and volcanic conglomerates. Thin and very localised grits occur, and tuffaceous units.
Definition of Lower Boundary: Base of mudstones succeeding Henllan Ash - feldspathic sandstones.
Definition of Upper Boundary: Top marked by basal ash-flow tuff of the Llyn Conwy Formation.
Thickness: 380 metres. Lateral variation, 0-380 metres.
Geographical Limits: Not defined.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Type Area  Snowdon, Sheet 119. 
Zalasiewicz, J A. 1992. Graptolite dating of Ordovician vulcanicity in the Arenig area, North Wales. Geological Journal, Vol.27, 379-389. 
British Geological Survey. 1993. Corwen, provisional. England and Wales sheet 120. Solid and drift, 1:50 000 (Southampton: Ordnance Survey for British Geological Survey.) 
Lynas, B D T, 1973. The Cambrian and Ordovician rocks of the Migneint area, North Wales. Journal of the Geological Society, London, Vol.129, 481-503. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: