The BGS Lexicon of Named Rock Units — Result Details

Thorverton Sandstone Formation

Computer Code: THSA Preferred Map Code: ThS
Status Code: Full
Age range: Permian Period (P) — Permian Period (P)
Lithological Description: Predominantly reddish brown fine- to very fine-grained sandstone, with local thin beds and partings of reddish brown clay. Lenticular breccia bed south of Raddon (c.SS 915 016); possibly other thin breccias present. Basaltic lavas at various levels. May correlate with Knowle Sandstone.
Definition of Lower Boundary: Rests on Cadbury Breccia, apparently fairly sharply, possibly unconformably; exact nature of contact uncertain.
Definition of Upper Boundary: Overlain, apparently fairly sharply and unconformably west of Thorverton by Crediton Breccia, and by Yellowford Formation elsewhere.
Thickness: To 120m
Geographical Limits: Main outcrop between West Raddon (SS 895 014), Thorverton, and Silverton. Fault-bounded outcrop around the Killerton area between Heazille (SS 947 005) in the west and Budlake (SS 985 001) in the east.
Parent Unit: Exeter Group (EXE)
Previous Name(s): Lower Sandstone (-1475)
Alternative Name(s): none recorded or not applicable
Type Area  Village of Thorverton, Devon. No suitable type section owing to poor exposure. 
Reference Section  Roadside exposures about 300m west of Chapel Farm, Raddon. Sandstone...1.7m, breccia channeled into sandstone...1.5m (Edwards, 1987). 
Edwards, R A, 1984. Geological Notes and Local Details for 1:10,000 Sheets. Parts of Sheets SS80SE and SS90SW (Thorverton, Devon). British Geological Survey, Exeter. 
Ussher, W A E, 1899. Exeter 1:63360 Geological Map. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable