The BGS Lexicon of Named Rock Units — Result Details

Trambley Cove Formation

Computer Code: TCF Preferred Map Code: notEntered
Status Code: Full
Age range: Visean Stage (CV) — Visean Stage (CV)
Lithological Description: Pale to dark grey and black, finely colour-banded mudstone with thin beds of commonly cross-bedded siltstone. The siltstone and locally the mudstone are silicified, giving the succession a cherty appearance. Greenish brown tuffaceous mudstones are locally present, especially towards the base.
Definition of Lower Boundary: The lower boundary is taken at the sharp contact of the finely banded dark to pale grey mudstones with thin siltstones of the Trambley Cove Formation with the underlying tuffs, lavas and agglomerates of the Tintagel Volcanic Formation.
Definition of Upper Boundary: The upper boundary is faulted. However, it is thought that as the formation is locally silicified, it may orignally have passed up into the Teign Chert Formation. (Freshney et al. 1972).
Thickness: 15m+
Geographical Limits: Tintagel area (SX 06 89) to the south of Launceston (SX 32 77), Cornwall. The outcrop in the Launceston area (BGS 1993) needs further investigation.
Parent Unit: Teign Valley Group (TEVY)
Previous Name(s): Upper Blue-Black Slates (-4919)
Trambley Cove Beds (-4362)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Coastal cliff at Trebarwith Strand, 2km south of Tintagel, north Cornwall. The section exposes 15m of mudstones with thin siltstones overlying the Tintagel Volcanic Formation. Tuffaceous mudstones are common in the lowermost part. Basal contact seen; upper contact is a thrust, seen in the section and overlain by Late Devonian Slates. 
Reference(s):
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). 
Parkinson, J, 1903. On the geology of the Tintagel and Davidstow district, Quarterly Journal of the Geological Society,Vol.59,408-421. 
Freshney, E C, McKeown, M C and Williams, M. 1972. Geology of the coast between Tintagel and Bude. Memoir of the Geological Survey of Great Britain, part of sheet 322 (England and Wales). 
McKeown, M C, Edmonds, E A, Williams, M, Freshney, E C and Masson Smith, D J. 1973. Geology of the country around Boscastle and Holsworthy. Memoir of the British Geological Survey, sheets 322 and 323 (England and Wales). 
Dewey, H, 1909. On Overthrusts at Tintagel (North Cornwall). Quarterly Journal of the Geological Society, Vol.65, 265-280. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E322 E336 E337