The BGS Lexicon of Named Rock Units — Result Details

Bracklesham Group

Computer Code: BRB Preferred Map Code: BrB
Status Code: Full
Age range: Ypresian Age (GY) — Lutetian Age (GL)
Lithological Description: The Bracklesham Group comprises interbedded to interlaminated clays, silts and mostly fine- or medium-grained sands, locally shelly. Glauconite occurs in the mid part of the sequence. Minor coarse-grained sands, fine gravelly sand, gravel beds, sandstones or ironstone concretions occur in places. Marginal marine to inner shelf. Eocene (late Ypresian to late Lutetian).
Definition of Lower Boundary: In the Hampshire Basin, as for the Wittering Formation, in the east or the Poole Formation in the west. In the London Basin, the base of the Bracklesham Group is at the base of the Bagshot Formation, marked by an upwards change from clay, silt and fine-grained sand of the Claygate Member to thick-bedded, fine-grained sands, with a basal fine gravelly sand developed in places. Locally, erosion has removed the topmost parts of the Claygate Member.
Definition of Upper Boundary: In the Hampshire Basin, as for the Selsey Sand Formation. In the London Basin, the Camberley Sand Formation is the youngest Palaeogene unit.
Thickness: About 120 m in the Hampshire Basin. Up to about 140 m in the London Basin.
Geographical Limits: In the Hampshire Basin, the Bracklesham Group forms broad arcuate outcrops from Selsey in the east, to Romsey in the north, the Dorchester area in the west and the northern part of the Isle of Wight in the south. In the London Basin, the main outcrop of the Bracklesham Group occurs in the central portion of the Palaeogene outcrop west of London. Small outliers of the Bagshot Formation occur in the axial part of the London Basin in north London (Hampstead Heath and Highgate), in Essex and on the Isle of Sheppey, Kent.
Parent Unit: Not Applicable (-)
Previous Name(s): Bournemouth Group [Obsolete Name and Code: Use BRB] (-1383)
Bracklesham Beds [Obsolete Name and Code: Use WIDS, BRB] (-2010)
Bracklesham Sand [Obsolete Name and Code: Use BRB] (-3868)
Bracklesham Sand/Beds (-718)
Bagshot Beds [Obsolete Name And Code: Use BGS] (BGB)
Alternative Name(s): none recorded or not applicable
Type Section  Seacliffs at Whitecliff Bay, Isle of Wight. 
Reference Section  Bracklesham Bay foreshore, Sussex/Hampshire. 
Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. 
Aldiss, D T. 2014. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report OR/14/008. 95 pp. 
Prestwich, J, 1847. On the main points of structure and the probable age of the Bagshot Sands and on their presumed equivalents in Hampshire and France. Quarterly Journal of the Geological Society, Vol.3, p.378-409. 
King, C. 1981. The stratigraphy of the London Clay and associated deposits. Tertiary Research Special Paper No.6. (Backhuys: Rotterdam). 
Curry, D, King, A D, King, C, and Stinton, F C. 1977. The Bracklesham Beds (Eocene) of Bracklesham Bay and Selsey, Sussex. Proceedings of the Geologists’ Association, Vol. 88, 243-254. 
Edwards, R A and Freshney, E C. 1987. Lithostratigraphical classification of the Hampshire Basin Palaeogene Deposits (Reading Formation to Headon Formation) Tertiary Research, Vol.8, 43-73. 
Bristow, C R, and Freshney, E C. 1986. Geology of the Poole-Bournemouth area. Geological Report for DOE: Land use planning, WA/86/5 (Exeter: British Geological Survey.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E267 E268 E269 E283 E284 E299 E314 E315 E331 E341 E342 E343