The BGS Lexicon of Named Rock Units — Result Details
Bencliff Grit Member
| Computer Code: | BFG | Preferred Map Code: | BfG |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Oxfordian Age (JO) — Oxfordian Age (JO) | ||
| Lithological Description: | Sandstone, fine-grained, and sandy siltstone, argillaceous, yellow and pale grey, medium- to very thick-bedded, with well developed swaley cross-stratification, planar and ripple lamination, and conspicuous erosional bases. In places these beds are intercalated with thin, discontinuous beds of sandy mudstone. The sandstones and siltstones locally contain large calcareous concretions (up to 1-2m in diameter), and the sandy mudstones are bioturbated with Diplocraterion. The sandstones are notably oil-impregnated. | ||
| Definition of Lower Boundary: | Base is a conformable passage with the underlying Nothe Clay Member, and marked by the upward gradational change from mudstone, becoming increasingly sandy upwards of the upper Nothe Clay, to fine-grained sandstone of the basal Bencliff Grit (Coe, 1995). | ||
| Definition of Upper Boundary: | A sharp, planar, bored erosion surface at the top of the Bencliff Grit marks the upward change from fine-grained sandstone to thin allaceous limestones and mudstones of the basal Osmington Oolite Formation. | ||
| Thickness: | Up to 7.5m | ||
| Geographical Limits: | South Dorset. | ||
| Parent Unit: | Redcliff Formation (RECF) | ||
| Previous Name(s): | Bencliff Grit Series
(-52)
Bencliff Grit [Obsolete Name and Code: Use BFG] (-2598) |
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| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Coastal section east of Osmington Mills, Dorset. Fully exposed in cliffs, up to 6.7m thick. Wright, 1986, pp5-6. | ||
| Type Section | Coastal section at Rodwell, near Weymouth, former Type Section, now concealed. 3 to 4.5m of beds formally exposed. Arkell, 1936, p.75. | ||
| Reference(s): | |||
| Blake, J F, and Huddleston, W H. 1877. On the Corallian rocks of England. Quarterly Journal of the Geological Society of London, Vol. 33, 260-405. | |||
| Newall, A J. 2000. Fault activity and sedimentation in a marine rift basin (Upper Jurassic, Wessex basin, UK). Journal of the Geological Society, London, Vol.157, 83-92. | |||
| Wright, J K, and Cox, B M. 2001. British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series. No. 21. (Peterborough: Joint Nature Conservation Committee/Chapman and Hall.) | |||
| Coe, A L. 1995. A comparison of the Oxfordian successions of Dorset, Oxfordshire and Yorkshire. 151-172 in Taylor, P D (Ed.) Field Geology of the British Jurassic. [Bath: The Geological Society.] | |||
| Arkell, W J. 1947. Geology of the country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the British Geological Survey. Sheets 341, 342, 343 and small portions of sheets 327, 328 and 329 (England and Wales). | |||
| Wright, J K. 1986. A new look at the stratigraphy, sedimentology and ammonite fauna of the Corallian Group (Oxfordian) of south Dorset. Proceedings of the Geologists' Association, Vol. 97, 1-21. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E341 E342 E343 | |||