140 million years ago Dorset was covered by swamps and lagoons in which the dinosaurs roamed. This was towards the end of the Jurassic period and the start of the Cretaceous period. The footprints of these dinosaurs have been preserved as fossils in the rocks of the Swanage area, particularly in Purbeck Beds, a thick sequence of limestones and clays.
The rocks contain many other fossils and geologists can work out what life was like during these pre-historic times. Some rock layers have well preserved ripple marks, and they contain fossilised mud cracks and the casts of salt crystals that shows intense evaporation was taking place, just as is found in the Persian Gulf today.
Fossils include the remains of large reptiles like crocodiles and turtles,down to fish and insects and both fresh water and salt-water shells. Recent discoveries have included fragments of reptile eggshell, the first ever found in Britain.
100 sauropod footprints were discovered in 1997 at Keat's Quarry near Acton. The National Trust own the site and, are protecting the footprints.
The rocks at Durlston Bay, Worbarrow Tout and Bacon Hole contain many of the fossils discussed here. Worbarrow Bay and Bacon Hole lie within the Army Ranges which are usually only open at weekends and school holidays. Bacon Hole is less than a mile from the Fossil Forest near Lulworth Cove.
Swanage Museum, Langton Matravers Museum and Dorset County Museum contain examples of dinosaur footprints and other fossils from the Purbeck Beds.
Dr West's Geological Directory has lots of information and photographs of the coast, its geology and its fossils.
Devon & Dorset Jurassic Coast