The BGS Lexicon of Named Rock Units — Result Details
Crediton Breccia Formation
Computer Code: | CRBR | Preferred Map Code: | CrBr |
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Status Code: | Full | ||
Age range: | Permian Period (P) — Permian Period (P) | ||
Lithological Description: | Reddish brown, poorly to moderately cemented breccia with a silt, sand and clay matrix. Clasts mostly less than 4cm. Clasts of sandstone, siltstone, slate, shale, hornfells, chert, acid lava and tuff, quartz-porphyry, vein quartz, and a variety of tournalinised rocks. Poorly developed bedding in units mostly over 1m thick. Thin interbedded or lenses of red mudstone throughout. | ||
Definition of Lower Boundary: | Overlies unconformably early Permian formations - Knowle Sandstone, Bow Breccia, Cadbury Breccia, Thorverton Sandstone, except in Crediton area, where the Creedy Park Sandstone intervenes. | ||
Definition of Upper Boundary: | Overlain by Newton St Cyres Breccia fairly sharply, with feature locally developed at the junction. East of Shute [SS 890 001] overlain by the Shute Sandstone. | ||
Thickness: | Up to 240m | ||
Geographical Limits: | Extends from Nymet Tracey [SS 728 006] in Okehampton District (as part of the 'Crediton Conglomerates' of Edmonds, E A, et al, 1968), into the Exeter district at Knowle [SS 783 015], and thence to Crediton, eastwards through Shobrooke [SS 863 011] to south of Raddon [SS 910 010], east of there, passed into Yellowford Formation. | ||
Parent Unit: | Exeter Group (EXE) | ||
Previous Name(s): | Crediton Beds [Obsolete Name and Code: Use CRBR]
(-1456)
Crediton Conglomerates (-817) Yenpacott Breccia (-818) Crediton Breccias [Obsolete Code: Use CRBR] (CRCG) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Area | Town of Crediton, Devon. | ||
Reference(s): | |||
Hutchins, P F, 1963. The Lower New Red Sandstone of the Crediton Valley. Geological Magazine, Vol.100, 107-128. | |||
Edmonds, E A, Wright, J E, Beer, K E, Hawkes, J R, Fenning, P J, Freshney, E C, Lovelock, P E R, McKeown, M C, Ramsbottom, W H C and Williams, M. 1968. Geology of the country around Okehampton. Memoir of the Geological Survey of Great Britain, Sheet 324 (England and Wales). | |||
Scrivener, R C. 1988. Geology of the Newton St Cyres district (Devon). 1:10,000 Sheet SX89NE. British Geological Survey Technical Report, WA/88/5/ | |||
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. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
none recorded or not applicable |