The BGS Lexicon of Named Rock Units — Result Details

Parwyd Gneiss

Computer Code: PWYD Preferred Map Code: notEntered
Status Code: Index Level
Age range: Ediacaran Period (AD) — Ediacaran Period (AD)
Lithological Description: Strongly sheared and retrogressed hornblende-garnet amphibolites and subordinate felsic gneisses.
Definition of Lower Boundary: Unknown.
Definition of Upper Boundary: Unknown, except unconformably overlain by lower Ordivician (Arenig) sediments.
Thickness: Unknown.
Geographical Limits: Sheet 133 (Aberdaron).
Parent Unit: Sarn Complex (SRN)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Eastern side of Parwyd Cove, Lleyn Peninsula. Gibbons W and McCarroll D, 1993. 
Reference(s):
Gibbons W and McCarroll D. 1993. Geology of the country around Aberdaron, including Bardsey Island. Memoir of the British Geological Survey, Sheet 133 (England and Wales). (London: H.M.S.O.). 88pp. 
Gibbons, W and Horak, J. 1990. Contrasting metamorphic terranes in northwest Wales. 315-327 in D'Lemos, R S, Strachan, R A and Topley, C G (editors),The Cadomian Orogeny. Geological Society of London Special Publication No.51. 
Matley C A. 1928. The Pre-Cambrian complex and assocciated rocks of south-western Lleyn (Carnarvonshire). Quarterly Journal of the Geological Society of London, Vol. 84, 440-501. 
Gibbons W. 2000. Braich-y-pwll to Parwyd. 174-179 in Precambrian Rocks of England and Wales. Carney J (Editor). Geological Conservation Review Series No 20. (Peterborough: Joint Nature Conservation Committee). 
Shackleton, R M. 1956. Notes on the structure and relations of the Precambrian and Ordovician rocks of southwestern Lleyn (Carnarvonshire). Geological Journal, Vol.1. 400-409. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E133