The Thanet Formation is known at outcrop and in the subsurface over central and eastern parts of the London Basin.

To the west it is missing, with the Lambeth Group lying directly on the Chalk, and to the north it is replaced by the Ormesby Clay Member.

At the base of the formation a bed of flint pebbles is often developed with clasts up to cobble size in a matrix of glauconitic clayey sand.

[2] At Herne Bay the beds are divided as follows (top to bottom):[4] The Thanet Formation was deposited in open marine conditions.

[1] The fauna give somewhat contradictory evidence of the climate, with molluscs of both cold and warm water type being found and tropical to sub-tropical fish recognised.