1911 Encyclopædia Britannica/Woolwich-and-Reading Beds

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WOOLWICH-AND-READING BEDS, in geology, a series of argillaceous and sandy deposits of lower Eocene age found in the London and Hampshire basins. By the earlier geologists this formation was known as the “Plastic Clay” so called by T. Webster in 1816 after the Argile plastique of G. C. F. D. Cuvier and A. Brongniart. It was called the “Mottled Clay” by J. Prestwich in 1846, but in 1853 he proposed the name “Woolwich-and-Reading Beds” because the other terms were not applicable to the different local aspects of the series.

Three distinct types of this formation are recognized: (1) The Reading type, a series of lenticular mottled clays and sands, here and there with pebbly beds and masses of fine sand converted into quartzite. These beds are generally unfossiliferous. They are found in the N. and W. portions of the London Basin and in the Hampshire Basin. (2) The Woolwich type, 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 S.E. London there are pebble beds and lignitic layers. The Woolwich beds occur in W. Kent, the E. borders of Surrey, the borders of E. Kent, in S. Essex and at Newhaven in Sussex. (3) A third type consisting of light-coloured false-bedded sands with marine fossils occurs in E. 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. Except in the Hampshire basin the Woolwich-and-Reading beds usually rest on the Thanet beds, but they are found on the Chalk near Bromley, Charlton, Hungerford, Hertford, Reading, &c. In Dorsetshire the Reading beds appear on the coast at Studland Bay and at other points inland. The “Hertfordshire Pudding Stone” is a well-known rock from near the base of the formation; it is a flint pebble conglomerate in a siliceous matrix. The fossils, estuarine, freshwater and marine, include Corbicula cuneiformis, C. tellinella, Ostrea bellovacina, Vivaparus 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.

See Eocene, also J. Prestwich, Q.J.G.S. (1854), x.; W. Whitaker, “Geology of London”, Mem. Geol. Survey, i. and ii. (1889) and Sheet Memoir, No. 268.