The BGS Lexicon of Named Rock Units — Result Details

Boscombe Sand Formation

Computer Code: BOSS Preferred Map Code: notEntered
Status Code: Full
Age range: Lutetian Age (GL) — Lutetian Age (GL)
Lithological Description: Fine- to medium-grained sand, partly cross-bedded, with lenticular units of rounded flint pebble- and cobble-gravel. Clayey carbonaceous sands toward the top.
Definition of Lower Boundary: Formation overlies a marine transgressive surface developed on the Branksome Sand. The basal contact is a generally planar erosion surface at the change from interbedded sands and clays (Branksome Sand Formation) up into fine-grained sands of the formation.
Definition of Upper Boundary: Fine grained sands of the formation are overlain by marine glauconitic clays of the Barton Clay Formation as a combined erosion surface and transgressive surface which can be traced across the Hampshire Basin.
Thickness: 14m (Isle of Wight) up to 27m in its type area.
Geographical Limits: Restricted to the western part of the Hampshire Basin, documented mainly in the Bournemouth-Christchurch coastal area and the western end of the Isle of Wight (Alum Bay), overlying the Branksome Sand Formation.
Parent Unit: Bracklesham Group (BRB)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Reference Section  Christchurch Borehole SZ29SW12. Boscombe Sand divided into two units based on characteristic gamma-ray logs. A lower 9m thick coarsening upward unit overlain by an upper 10.3m thick clay-rich unit. 
Type Section  Cliffs between Boscombe Pier and Hengistbury Head, Bournemouth where between 20 and 27m of fine- to medium-grained well-sorted in planar, cross-bedded and bidirectional cross-bedded units. Bristow et al. (1991). 
Reference Section  Northern end of Alum Bay, Isle of Wight. 
Bristow, C R, Freshney, E C, and Penn, I E. 1991. Geology of the country around Bournemouth. Memoir for 1:50 000 geological sheet 329 (England and Wales). HMSO, London. 
Hooker, J J. 1986. Mammals from the Bartonian (middle/late Eocene) of the Hampshire Basin, southern England. Bulletin of the British Museum (Natural History), Vol. 39, 191-478. 
Todd, J. 1990. The stratigraphy and correlation of the Selsey Formation and Barton Clay Formation (Middle Eocene) of Studley Wood, Hampshire. Tertiary Research, Vol. 12, 37-50. 
Hopson, P M, and Farrant A R. 2014. Geology of the Isle of Wight - a brief explanation of the Isle of Wight Special Geological Map Sheet. Sheet Explanation of the British Geological Survey. Parts of 1:50 0000 Sheets 330 (Lymington), 331 (Portsmouth), 344 (Chale) and 345 (Ventnor) (England and Wales) 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: