The BGS Lexicon of Named Rock Units — Result Details

Petrockstow Valley Formation

Computer Code: PETRO Preferred Map Code: notEntered
Status Code: Full
Age range: Early Pleistocene Epoch (QPE) — Holocene Epoch (QH)
Lithological Description: The formation includes the deposits of five river terraces. The deposits of the first terrace are largely gravel of Carboniferous sandstone with scattered flints, with thin seams of clayey sand and sandy clay, 1.5 - 7m thick. The pebbles are up to 20mm in diameter, increasing to 130mm at the base. Deposits of the higher terraces are less gravelly, and dominantly comprise clay with gravel seams.
Definition of Lower Boundary: Unconformable on bedrock of Paleogene and Late Carboniferous age.
Definition of Upper Boundary: Surface.
Thickness: Up to c.8m
Geographical Limits: The Petrockstow Basin, Devonshire.
Parent Unit: Cornubian Catchments Subgroup (CCAT)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The valley of the Petrockstow Basin. Freshney et al., 1979. 
Reference(s):
Freshney, E C, Beer, K E and Wright, J E. 1979. Geology of the country around Chumleigh. Memoir of the Geological Survey of Great Britain, Sheet 309 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E308 E309