Bracklesham Group

The Bracklesham Group (formerly Bracklesham Beds), in geology, is a series of clays and marls, with sandy and lignitic beds, in the middle Eocene of the Hampshire Basin and London Basin of England.

Bracklesham Group
Stratigraphic range: Eocene
Branksome Sand Formation at the top of the Bracklesham Group, made up of white, yellow, rose-coloured and crimson sands with laminated pipe clay. Alum Bay cliffs.
Type	Group
Sub-units	London Basin - Bagshot Formation, Windlesham Formation, Camberley Sand Formation Hampshire Basin - Wittering Formation, Earnley Sand Formation, Marsh Farm Formation, Selsey Sand Formation, Poole Formation, Branksome Sand Formation, Boscombe Sand Formation
Underlies	Barton Group
Overlies	Thames Group
Thickness	~120 m Hampshire Basin, ~140 m London Basin
Lithology
Primary	clay, silt & sand
Location
Region	Hampshire Basin, London Basin, England
Country	United Kingdom
Type section
Named for	Bracklesham

The type section of the Bracklesham Group is the sea cliffs at Whitecliff Bay on the Isle of Wight, and it is also well developed on the mainland. The Group gets its name from a section at Bracklesham in Sussex. The thickness of the deposit is around 120 m. Fossil mollusca are abundant, and fossil fish are to be found, as well as Palaeophis, a sea-snake, and Puppigerus, a sea turtle. Nummulites and other foraminifera also occur.

The Bracklesham Group lies between the Barton Clay above and the Bournemouth Beds, Lower Bagshot, below. In the London Basin, these beds are represented only by thin sandy clays in the Middle Bagshot group. In the Paris Basin the "Calcaire grossier" lies upon the same geological horizon.

References

Attribution

• This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Bracklesham Beds". Encyclopædia Britannica (11th ed.). Cambridge University Press. This cites:
  • F. Dixon, Geology of Sussex (new ed., 1878)
  • F. E. Edwards and SV Wood, Monograph of Eocene Mollusca, Palaeontographical Soc. vol. i. (1847–1877)
  • Geology of the Isle of Wight, Mem. Geol. Survey (2nd ed., 1889)
  • C. Reid, The Geology of the Country around Southampton, Mem. Geol. Survey (1902).
• New Forest Geology Guide