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 Horak, J. 1990. Contrasting metamorphic terranes in northwest Wales. 315-327 in The Cadomian Orogeny. D'Lemos, R S, Strachan, R A, and Topley, C G (editors). Geological Society of London Special Publication No. 51. 
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. 
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.) 
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: HMSO.) 88pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E133