The BGS Lexicon of Named Rock Units — Result Details

Porthtowan Formation

Computer Code: POAN Preferred Map Code: Ptn
Status Code: Full
Age range: Eifelian Age (DI) — Frasnian Age (DR)
Lithological Description: Interbedded slaty mudstone, grey and grey-green, and sandstone. Subordinate sandstone beds are up to 2m thick, typical turbidites.
Definition of Lower Boundary: Transition above Grampound Formation of Meadfoot Group.
Definition of Upper Boundary: Transition with Mylor Slate Formation.
Thickness: 2.8km
Geographical Limits: West Cornwall.
Parent Unit: Gramscatho Group (GRO)
Previous Name(s): Gramscatho Beds [Obsolete Name and Code: Use POAN, GRO] (-2375)
Alternative Name(s): none recorded or not applicable
Type Section  Coastal section, West Cornwall, north-eastwards from Hells Mouth. 
Hendriks, E M L, 1931. The stratigraphy of South Cornwall Report of the British Association for 1930, 332 et seq. 
Leveridge, B E, Holder, M T and Goode, A J J, 1990. Geology of the country around Falmouth. Memoir of the British Geological Survey, Sheet 352 (England and Wales). 
Hill, J B and MacCallister, D A. 1906. The geology of Falmouth and Truro and of the mining district of Camborne and Redruth. Memoirs of the Geological Survey. Explanation of Sheet 352 (England and Wales). 
Hendriks, E M L, 1937. Rock Succession and structure in South Cornwall, a revision. With notes on the central European facies and Variscan folding there present. Quarterly Journal of the Geological Society, London, Vol.93, 322-360. 
Hendriks, E M L, 1949. The Gramscatho Series. Transactions of the Royal Geological Society of Cornwall, Vol.18, 50-61. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: