The BGS Lexicon of Named Rock Units — Result Details

Bedded Pyroclastic Formation

Computer Code: BPY Preferred Map Code: BP
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Bedded basaltic tuff, tuffite, breccia deposits, intrusive and extrusive basalts.
Definition of Lower Boundary: Overlies the Lower Rhyolitic Tuff Formation.
Definition of Upper Boundary: Overlain by acid tuffs of Upper Rhyolitic Tuff Formation.
Thickness: 450m
Geographical Limits: Central Snowdonia.
Parent Unit: Snowdon Volcanic Group (SV)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Cwm Idwal. 
Type Section  Cwm Glas, Snowdon. 
Reference(s):
Howells, M F, Reedman, A J and Campbell, S D G, 1991. Ordovician (Caradoc) marginal basin volcanism in Snowdonia (north-west Wales). (London: HMSO for the British Geological Survey). 
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. 
Howells, M F and Smith, M. 1997. Geology of the country around Snowdon. Memoir of the British Geological Survey, Sheet 119 (England and Wales). (London: The Stationery Office). 104pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E119 E106