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 (-2375)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Coastal section, West Cornwall, north-eastwards from Hells Mouth. 
Reference(s):
Hill. J B and MacCallister, D A, 1906. Memoir of the Geological Survey, 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. 
Leveridge, B E, Holder, M T and Goode, A J J, 1990. Memoir of the British Geological Survey, Sheet 352 (east and west). 
Hendriks, E M L, 1931. The stratigraphy of South Cornwall Report of the British Association for 1930, 332 et seq. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E352
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