Lambeth Group - Subdivision

Subdivision

The Lambeth Group consists of three formations:

• The Reading Formation, a series of lenticular mottled clays and sands, here and there with pebbly beds and masses of fine sand converted into sandstone. These beds are generally unfossiliferous. They are found in the north and west portions of the London Basin and in the Hampshire Basin.
• The Woolwich Formation, grey clays and pale sands, often full of estuarine shells and in places with a well-marked oyster bed. At the base of the shell-bearing clays in southeast London there are pebble beds and lignitic layers. The Woolwich Formation occurs in west Kent, the east borders of Surrey, the borders of east Kent, in south Essex and at Newhaven in Sussex.
• The Upnor Formation, consisting of light-coloured false-bedded sands with marine fossils occurs in east Kent. Where it rests on the Thanet beds it is an argillaceous greensand with rounded flint pebbles; where it rests on the chalk it is more clayey and the flints are less rounded and are green-coated.

In Dorset the Reading Formation appears on the coast at Studland Bay and at other points inland. The Hertfordshire puddingstone is a well-known rock from near the base of the formation; it is a flint pebbly conglomerate in a siliceous matrix. The fossils, estuarine, freshwater and marine, include Corbicula cuneiformis, C. tellinella, Ostrea bellovacina, Viva parus lentus, Planorbis hemistoma, Melania (Melanatria) inquinata, Neritina globulus, and the remains of turtles, crocodiles, sharks, birds (Gastornis) and the mammal Coryphodon. Bricks, tiles and coarse pottery and occasionally firebricks have been made from the clay beds in this formation.