Geology
See also, Geology of East Sussex, Weald basin and Weald–Artois anticline
The Weald is the eroded remains of a geological structure, an anticline, a dome of layered Lower Cretaceous rocks cut through by weathering to expose the layers as sandstone ridges and clay valleys. The oldest rocks exposed at the centre of the anticline are correlated with the Purbeck Beds of the Upper Jurassic. Above these, the Cretaceous rocks, include the Wealden Group of alternating sands and clays - the Ashdown Sand Formation, Wadhurst Clay Formation, Tunbridge Wells Sand Formation (collectively known as the Hastings Beds) and the Weald Clay. The Wealden Group is overlain by the Lower Greensand and the Gault Formation, consisting of the Gault and the Upper Greensand.
The rocks of the central part of the anticline include hard sandstones, and these form hills now called the High Weald. The peripheral areas are mostly of softer sandstones and clays and form a gentler rolling landscape, the Low Weald. The Weald-Artois Anticline continues some 65 km (40 mi) further south-eastwards under the Straits of Dover, and includes the Boulonnais of France.
Many important fossils have been found in the sandstones and clays of the Weald, including, for example, Baryonyx. The famous scientific hoax of Piltdown Man was claimed to have come from a gravel pit at Piltdown near Uckfield. The first Iguanodon was identified by Gideon Mantell, from a fossil discovered in a pit near Cuckfield in 1819.
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