The BGS Lexicon of Named Rock Units — Result Details

Harbour Cove Slate Formation

Computer Code: HCSL Preferred Map Code: HCSl
Status Code: Pending Upgrade
Age range: Frasnian Age (DR) — Famennian Age (DA)
Lithological Description: Homogeneous green and grey-green slaty mudstones with thin beds of black, commonly pyritous mudstone and yellowish brown sideritic mudstone. The higher parts of the formation contain beds of purple mudstone, commonly with small-scale colour banding. Coarse-grained tuffs up to 100m thick occur locally. Beds of ferruginous and calcareous nodules becoming increasingly common towards the top of the formation.
Definition of Lower Boundary: At lower Merope Island the Harbour Cove Slate Formation rests conformably on slate and lava of the Trevose Slate Formation.
Definition of Upper Boundary: Faulted in the area of the Camel Estuary but mapped as a conformable boundary with the Polzeath Slate Formation in the St Minver synclinorium.
Thickness: Estimated to be 260m near Padstow, and 600m east of the Allen Valley Fault..
Geographical Limits: Trevone - Wadebridge - St Mabyn - St Tudy - St Teath - St Isaac Bay, north Cornwall.
Parent Unit: Not Entered (?)
Previous Name(s): Upper Devonian Purple And Green Slate (-954)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Cliffs between St George's Cove and Harbour Cove. Beese, A P, 1984. 
Reference(s):
Beese, A P, 1984. Stratigraphy of the Upper Devonian argillite succession in north Cornwall. Geological Magazine, Vol.121, 61-69. 
Selwood, E B, Thomas, J M, Williams, B J, Clayton, R, Durning, B, Smith, O and Warr, L N, 1998. Geology of the country around Trevose Head and Camelford. Memoir of the British Geological Survey, sheets 335 and 336 (England and Wales). 
Gauss, G A and House, M R, 1972. The Devonian successions in the Padstow area, north Cornwall. Journal of the Geological Society of London, Vol.128, 151-172. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E336