Purbeck Formation

Purbeck Group Stratigraphic range: Early Cretaceous
Type	Group
Sub-units	Lulworth, Durlston and Haddenham formations
Underlies	Wealden Group
Overlies	Portland Group
Lithology
Primary	mudstone
Other	limestone, evaporites
Location
Region	southern England
Country	England
Type section
Named for	Isle of Purbeck

The Purbeck Group is an Upper Jurassic to Lower Cretaceous lithostratigraphic group (a sequence of rock strata) in south-east England. The name is derived from the district known as the Isle of Purbeck in Dorset where the strata are exposed in the cliffs west of Swanage.

The Purbeck Group is famous for its fossils of reptiles and early mammals. This sequence of rocks has gone by various names in the past including amongst others the Purbeck Beds, Purbeck Formation, Purbeck Limestone Formation and Purbeck Stone.

Rocks of this age have in the past been called the Purbeckian stage by European geologists. The Purbeckian corresponds with the Tithonian to Berriasian stages of the internationally used geologic timescale.

The Purbeck Group outcrops follow the line of the Jurassic outcrop from Dorset, through the Vale of Wardour, Swindon, Garsington, Brill and Aylesbury. In East Sussex, the Purbeck Group outcrops at three locations north and northwest west of Battle, East Sussex and at Netherfield. They also occur at several other locations east of Heathfield, East Sussex and at Beak's Wood near Burwash. Deposits of evaporite minerals such as gypsum and anhydrite, within the Purbeck Group are mined and processed in Mountfield, East Sussex. In Lincolnshire they are represented in part by the Spilsby Sands and in Yorkshire by portions of the Speeton Clay.

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