The Weald is the eroded remains of a geological structure, an
anticline, a dome of layered
Lower Cretaceous rocks cut through by
erosion 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,
Wadhurst Clay,
Tunbridge Wells Sand (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 Clay 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 these form the gentler rolling landscape of
Low Weald, of which the Vale of Kent is a part. The
Weald-Artois Anticline continues some further south-eastwards under the
Straits of Dover, and includes the
Boulonnais of
France. ==References==