Thames Group

The Thames Group is an Eocene lithostratigraphic group (a sequence of rock strata) which is widespread in southeast England, especially in the Hampshire Basin from Dorset through Hampshire to West Sussex and in the Isle of Wight and in the London Basin from Berkshire east through northern Hampshire, Surrey and Greater London to Essex and north Kent. It is encountered in older literature as the London Clay Group.

Thames Group
Stratigraphic range: Eocene
London Clay Formation exposed at the base of the cliffs at Walton-on-the-Naze
Type	Group
Sub-units	Harwich Formation, London Clay Formation
Underlies	Bracklesham Group
Overlies	Oldhaven Formation or Lambeth Group
Thickness	c110 - 115m in Hampshire Basin
Lithology
Primary	mudstone
Other	silty clay, sandy silt, sandy clayey silt
Location
Country	England
Extent	Hampshire Basin, London Basin
Type section
Named for	River Thames

Stratigraphy

The London Clay Formation is the uppermost sub-unit of the Group. It is overlain by the lowermost units of the Bracklesham Group; these being the Bagshot Formation in the London Basin, and the Poole and Wittering formations in the Hampshire basin and English Channel. Beneath the London Clay is the Harwich Formation which itself overlies Lambeth Group strata, these being rocks of the Thanet Formation in the London Basin.