The BGS Lexicon of Named Rock Units — Result Details

Tavy Formation

Computer Code: TVY Preferred Map Code: Tvy
Status Code: Full
Age range: Frasnian Age (DR) — Famennian Age (DA)
Lithological Description: Pale green and grey-green slaty silty mudstone with minor thin fine-grained sandstone beds and lenses. Medium- to fine-grained sandstone interbedded with mudstone and laminated siltstone constitute the Trehills Member.
Definition of Lower Boundary: A transition into the Torpoint Formation. Pale green slaty mudstone of the Tavy Formation passing into purplish red slaty mudstone of the Torpoint Formation.
Definition of Upper Boundary: A transition between the Tavy Formation and the Burraton Formation (grey slate) is observed in the vicinity of North Hooc Mine [4254 6608], and Holes Hole [425 655] in an inverted sequence.
Thickness: Not known.
Geographical Limits: Defined on Sheet 348 but similar lithologies occur on: 335/336 (Tredom Slate Formation), 337 (Kate Brook Slate Formation), 338 and 339 (Kate Brook Slate Formation), 349 (Upper Devonian Slate).
Parent Unit: Tamar Group (TAMA)
Previous Name(s): Delabole Slates (-3996)
Penpethy Beds (-2152)
Woolgarden Slates [Obsolete Name And Code: See TVY] (WSL)
Kate Brook Slate [Obsolete Name And Code: See TVY] (KBSL)
Tredorn Beds (-4939)
Tredorn Phyllites (-4940)
Kate Brook Succession (-4377)
Cann Wood Slate Formation (-3099)
Halwell Cottage Beds (-3100)
Woolgarden Phyllite (-2506)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  River cliff, inverted sequence and transitional top of Formation at Holes Hole. 
Reference Section  River cliff at Weir Point containing a transitional boundary between the greenish grey slatey mudstone of the Tavy Formation and the purplish red silty mudstone of the Torpoint Formation. 
Partial Type Section  River cliff. Tavy Bridge to Hole's Hole. 
Partial Type Section  River cliff. Warleigh Quay to Potters Bridge. 
Partial Type Section  River cliff. Tavy Bridge to Whittacliffe Wood. 
Reference(s):
Selwood, E B, Edwards, R A, Simpson, S, Chesher, J A, Hamblin, R J O, Henson, M R, Riddolls, B W and Waters, R A. 1984. Geology of the countryside around Newton Abbot. Memoir of the British Geological Survey, Sheet 339 (England and Wales). 
Dewey, H, 1909. On Overthrusts at Tintagel (North Cornwall). Quarterly Journal of the Geological Society, Vol.65, 265-280. 
Chandler, P and McCall, G J H, 1985. Stratigraphy and structure of the Plymouth-Plymstock area: a preliminary revision. Proceedings of the Ussher Society, Vol.6, 253-257. 
Parkinson, J, 1903. On the geology of the Tintagel and Davidstow district, Quarterly Journal of the Geological Society,Vol.59,408-421. 
Waters, R A, 1970. The Variscan structure of eastern Dartmoor. Proceedings of the Ussher Society, Vol.2, 191-197. 
Leveridge B E, Holder, M T, Goode, A J J, Scrivener R C, Jones N S and Merriman, R J. 2002. Geology of the Plymouth and south-east Cornwall area. Memoir of the British Geological Survey, Sheet 348 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E335 E336 E339 E337 E348 E338 E349