The BGS Lexicon of Named Rock Units — Result Details

Alphington Breccia Formation

Computer Code: ALBR Preferred Map Code: AlBr
Status Code: Full
Age range: Permian Period (P) — Permian Period (P)
Lithological Description: Breccia, reddish brown, clayey, silty, fine-grained. Clasts predominantly culm shale and sandstone, together with hornfels, chert, quartz-porphyry, and lava. Most clasts less than 4cm; some range up to 0.1m and large boulders of porphyry are locally present.
Definition of Lower Boundary: Rests on Whipton Formation or on basalt. Junction with the Whipton Formation is gradational over a vertical interval of about 10m, the boundary being drawn where breccia becomes the dominant lithology. Where the formation overlies basalt, a large hiatus is present between c.290 Ma basalts and c.260 Ma or younger Alphington Breccia.
Definition of Upper Boundary: Overlain by Heavitree Breccia, which forms a scarp above the Alphington Breccia owing to the difference in cementation between the two formations.
Thickness: 160-240m
Geographical Limits: Extends from Exeter City southwestwards through Alphington to Shillingford St George and Clapham (SX 895 870) areas.
Parent Unit: Exeter Group (EXE)
Alternative Name(s): TEIGNMOUTH BRECCIA
Type Area  Alphington [SX 918 900] area of Exeter, Devon. Formation generally poorly exposed, so no good type section. 
Reference Section  Marshall Farm [SX 8861 8953], Dunchideock. 4 to 5m section behind barn; some boulders of porphyry, and clasts of lava. 
Selwood, E B, Edwards, R A, Simpson, S, Chesher, J A, Hamblin, R J O, Hanson, 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. 
Bridtow, C R, 1984. Geological notes and local details for 1:10 000 Sheet SX98NW, Exminster, Devon. British Geological Survey. 
Laming, D J C, 1982. The New Red Sandstone. "In" Durrance, E M, and Laming, D J C. (Editors). The Geology of Devon, p.152-162. 
Smith, D B, and others, 1974. A correlation of Permian rocks in the British Isles. Special Report of the Geological Society of London, No. 5. 
Bristow, C R, Scrivener, R C, 1984. The stratigraphy and structure of the Lower New Red Sandstone of the Exeter district. Proceedings of the Ussher Society, Vol. 6, p. 68-74. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: