The BGS Lexicon of Named Rock Units — Result Details
Portland Sand Member (Wiltshire, Oxfordshire and Buckinghamshire) [Obsolete: use POSA]
| Computer Code: | PSND | Preferred Map Code: | PIS |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Tithonian Age (JI) — Tithonian Age (JI) | ||
| Lithological Description: | [Obsolete: use POSA] Calcareous sandstones and sands, commonly glauconitic (Glauconitic Beds) and conglomeratic sandstones, sands, marls and limestones (Upper Lydite Bed). | ||
| Definition of Lower Boundary: | Conglomeratic and glauconitic coarse-grained sand, sandstone and limestone (Upper Lydite Bed) resting non-sequentially on mudstones, siltstones or fine-grained argillaceous sands and sandstones of the Upper Kimmeridge Clay. | ||
| Definition of Upper Boundary: | Either seen as a transition from calcareous sandstones and sands, commonly glauconitic (Glauconitic Beds), to limestone of Portland Stone Member, which is probably diachronous, or as a sharp, non-conformable junction with generally non-calcareous and commonly ferruginous sands and sandstones of the Lower Greensand, or Whitchurch Sand Formations, or by calcareous mudstones of the Gault Formation. | ||
| Thickness: | Up to 6 m thick. | ||
| Geographical Limits: | Outliers from Swindon to Aylesbury in north Wiltshire, Oxfordshire and Buckinghamshire, and possiblly an outlier in the Vale of Pewsey near Devizes, though this is currently rather poorly known (see Wimbledon, 1980). A separate description applies to the Portland of the Vale of Wardour in south Wiltshire or Dorset. | ||
| Parent Unit: | none recorded or not applicable | ||
| Previous Name(s): | Glauconitic Beds [Obsolete Name and Code: Use PSND]
(-4273)
Upper Lydite Bed [Obsolete Name and Code: Use PSND] (-4851) Portland Sand [Obsolete Name and Code: Use POSA, PLS, PSND, WAR] (-2373) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Section | BGS Hartwell Borehole, 12.19 - 17.95 m depth. Cox, Gallois and Sumbler, 1994; Horton et al., 1995. | ||
| Reference Section | Swindon Old Town Railway Cutting. Wimbledon, 1976. | ||
| Type Area | Thame to Aylesbury area. 1:50 000 Sheet 237. | ||
| Reference(s): | |||
| Wimbledon, W A. 1980. Portlandian correlation chart. 85-93 in Cope, J C W (Editor), A correlation of the Jurassic rocks of the British Isles. Part Two: Middle and Upper Jurassic. Geological Society of London Special Report, No.15. | |||
| Wimbledon, W A. 1976. The Portland Beds (Upper Jurassic) of Wiltshire. Wiltshire Archaeological and Natural History Magazine, Natural History, Vol.71, 3-11. | |||
| Wimbledon, W A and Cope, J C W. 1978. The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage. Journal of the Geological Society of London, Vol.135, 183-190. | |||
| Horton, A, Sumbler, M G, Cox, B M and Ambrose, K, 1995. Geology of the country around Thame. Memoir of the British Geological Survey, Sheet 237 (England and Wales). | |||
| Cox, B M, Gallois, R W, and Sumbler, M G. 1994. The stratigraphy of the BGS Hartwell Borehole, near Aylesbury, Buckinghamshire. Proceedings of the Geologists' Association, Vol. 105, 209-224. | |||
| Cox, B M. 1996. Portland and Purbeck Formations. In: British Regional Geology: London and the Thames Valley. Fourth Edition. Sumbler, M G (Editor), 58-60. (London HMSO.) | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E219 E220 E237 E252 E282 | |||