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WEALDEN

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Originally appearing in Volume V28, Page 437 of the 1911 Encyclopedia Britannica.
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WEALDEN , in See also:

geology, a thick See also:series of estuarine and fresh-See also:water deposits of See also:Lower Cretaceous See also:age, which derives its name from its development in the See also:Weald of See also:Kent and See also:Sussex. In the type See also:area it is exposed by the denudation of a broad anticlinal See also:fold from which the higher Cretaceous beds have been removed. The Wealden rocks See also:lie in the central See also:part of this anticline between the escarpments of the See also:North and See also:South See also:Downs; they extend eastwards from the neighbourhood of See also:Haslemere and See also:Elland See also:Chapel to the See also:west between See also:Pevensey and See also:Hythe. This formation is divisible into two portions, the Weald See also:Clay above and the See also:Hastings Sands below. The Weald Clay which occupies the central, upland part of the area from See also:Horsham to the See also:sea See also:coast consists of dark See also:brown and See also:blue See also:clays and shales, occasionally mottled in the neighbourhood of sandy lenticles, which together with calcareous sandstones, shelly limestones and nodular See also:iron-stones take a subordinate See also:place in the series. About Horsham the Weald Clay is moo ft. thick, but it decreases in an eastward direction; at Tunbridge it is cnly 600 ft. Certain subordinate beds within the Weald Clay have received distinctive names. " Horsham See also:stone " is a calcareous flaggy See also:sandstone, often ripple marked, usually less than 5 ft. thick, which occurs at about 120 ft. above the See also:base of the Clay. " Sussex See also:marble " is the name given to more than one of the high See also:limestone beds which are mainly composed of a large See also:form of Paludina (P. fluviorum); some of the lower limestone layers contain a small See also:species (P. sussexiensis). The Sussex marble (proper) occurs about too ft. below the See also:top of the clays; it is the most important of the limestone bands, and its thickness varies from 6 ft. to 2 in.; it is known also as Bethersden marble, Petworth marble, Laughton stone, &c. It has been widely used in the Weald See also:district in See also:church See also:architecture and for polished mantelpieces. The ironstones were formerly smelted in the western part of the area.

The Hastings Sands are divisible into three See also:

main subdivisions: the Tunbridge See also:Wells See also:Sand, the Wadhurst Clay and the Ashdown Sand. Like the overlying Weald Clay this series thickens as a whole towards the west. In the west, the Tunbridge Wells Sand is separated into an upper and lower See also:division by the thickening of a See also:bed of clay—the Grinstead Clay—which in the See also:east, about See also:Rye, &c., is quite thin; at Cuckfield a second clay bed 15 ft. thick divides the upper division. The upper beds of the lower Tunbridge Wells Sand cause See also:good landscapes around West Hoathly and near East Grinstead. The Wadhurst Clay is very See also:constant in See also:character; near the base it frequently contains clay-ironstone, which in former times was the main source of See also:supply for the Wealden iron See also:industry. Much of the higher portion of the Hastings Sand See also:country is made of the Ashdown Sands, consisting of sand, soft sandstones and subordinate clay mends; in the east, however, clay is strongly See also:developed at the base of this See also:group, and at Fairlight is more than 36o ft. thick, while the sandy portion is only 15o ft. These clays with sandy layers are known as the Fairlight Clays. Beds of ignite are found in these beds, and a calcareous sandstone, called Tlgate stone, occurs near the top of the Ashdown Sands and in the Wadhurst Clay. The old See also:town of Hastings is built on Ashdown Sand, but St Leonards is mainly on Tunbridge Wells Sand. Wealden beds occur on the See also:southern See also:side of the Isle of See also:Wight and in the Isle of Purbeck in See also:Dorsetshire. The Wealden anticline can he traced across the Channel into the Bas Boulonnais. A See also:separate Wealden area exists in north See also:Germany between See also:Brunswick and Bentheim, in the See also:Ostervald and Teutoberger Wald, where the See also:Deister Sandstone (15o ft.) corresponds to the Hastings Sands and the Walderthon (70–See also:loo ft.) to the Weald Clay.

The former contains valuable See also:

coal beds, worked in the neighbourhood of Obernkirchen, &c., and a good See also:building stone. The fossils of the Wealden beds comprise See also:freshwater shellfish, Unio, Paludina, Melanopsis, Cyrena; and estuarine and marine See also:WEALTH 437 forms such as Ostrea, Exogyra and Mytilus. An interesting series of dinosaurs and See also:pterodactyles has been obtained from the Wealden of See also:England and the See also:continent of See also:Europe, of which See also:Iguanodon is the best known—a large number of almost entire skeletons of this genus were discovered in some buried Cretaceous valleys at Bernissart in See also:Belgium; other forms are Heterosuchus, Ornithocheirus, Ornithopsis, Cimoliosaurus and Titanosaurus. Among the plant remains are Chara, Bennettites, Equisitiles, Fittonia, Sagenopteris and Thujites. The fishes, See also:plants and See also:reptiles of these formations possess a decidedly See also:Jurassic aspect, and for this See also:reason several authorities are in favour of retaining the Wealden rocks in that See also:system, and the See also:close relationship between this formation and the underlying See also:Purbeckian, both in England and in Germany, tends to support this view. See CRETACEOUS, NEOCOMIAN, PURBECKIAN; also W. Topley, " Geology of the Weald," Mem. Geol. Survey (See also:London, 1875). (J. A.

End of Article: WEALDEN

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