Portland Stone
This fine-grained limestone is extremely tough and erodes very slowly. Fossils include ammonites, bivalves and snails.
Purbeck Beds
These beds are made from clays, shales, mudstones and limestones. Fossils include dinosaur footprints, crocodiles and fish.
Wealden Clay
These beds contain sands, marls and clays and erode very quickly. Fossils include water fleas, snails and lignite, which is a type of woody coal.
Greensand
Formed entirely from layers of sandstone. Fossils include sea urchins and bivalves.