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) | ||
| Previous Name(s): | Alphington Breccia Member
(-638)
Heavitree And Alphington Breccias [Obsolete Code: Use AHBR] (HABR) Alphington Breccias [Obsolete Name and Code: Use ALBR] (-4424) |
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| Alternative Name(s): | Teignmouth Breccia |
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| Stratotypes: | |||
| 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. | ||
| Reference(s): | |||
| Bristow, C R, and 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, 68-74. | |||
| 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). | |||
| Laming, D J C, 1982. The New Red Sandstone. "In" Durrance, E M and Laming, D J C, (Editors). The Geology of Devon, p.148-177. | |||
| Smith, D B, Brunstrom, R G W, Manning, D I, Simpson, S and Shotton, F W. 1974. A correlation of Permian rocks in the British Isles. Geological Society of London Special Report No. 5. | |||
| Bridtow, C R. 1984. Geological notes and local details for 1:10 000 Sheet SX98NW, Exminster, Devon. British Geological Survey. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E325 | |||