Isle of Purbeck - Geology

Geology

The geology of the Isle is complex. It has a discordant coastline along the east and concordant coastline along the south. The northern part is Eocene clay (Barton Beds), including significant deposits of Purbeck Ball Clay. Where the land rises to the sea there are several parallel strata of Jurassic rocks, including Portland limestone and the Purbeck beds. The latter include Purbeck Marble, a particularly hard limestone that can be polished (though mineralogically, it is not marble). A ridge of Cretaceous chalk runs along the peninsula creating the Purbeck Hills, part of the southern England Chalk Formation that includes Salisbury Plain, the Dorset Downs and the Isle of Wight. The cliffs here are some of the most spectacular in England, and of great geological interest, both for the rock types and variety of landforms, notably Lulworth Cove and Durdle Door, and the coast is part of the Jurassic Coast World Heritage Site because of the unique geology.

In the past quarrying of limestone was particularly concentrated around the western side of Swanage, the villages of Worth Matravers and Langton Matravers, and the cliffs along the coast between Swanage and St. Aldhelm's Head. The "caves" at Tilly Whim are former quarries, and Dancing Ledge, Seacombe and Winspit are other cliff-edge quarries. Stone was removed from the cliff quarries either by sea, or using horse carts to transport large blocks to Swanage. Many of England's most famous cathedrals are adorned with Purbeck marble, and much of London was rebuilt in Portland and Purbeck stone after the Great Fire of London.

By contrast, the principal ball clay workings were in the area between Corfe Castle and Wareham. Originally the clay was taken by pack horse to wharves on the River Frome and the south side of Poole Harbour. However in the first half of the 19th century the pack horses were replaced by horse drawn tramways. With the coming of the railway from Wareham to Swanage, most ball clay was dispatched by rail, often to the Potteries district of Staffordshire.

Quarrying still takes place in Purbeck, with both Purbeck Ball Clay and limestones being transported from the area by road. There are now no functioning quarries of Purbeck Marble.