Purbeck stone refers to building stone taken from a series of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

beds found in the

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...

Purbeck Group 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 ...

, found on the

Isle of Purbeck The Isle of Purbeck is a peninsula in Dorset, England. It is bordered by water on three sides: the English Channel to the south and east, where steep cliffs fall to the sea; and by the marshy lands of the River Frome and Poole Harbour to the n ...

Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...

in southern England. The best known variety of this stone is

Purbeck Marble Purbeck Marble is a fossiliferous limestone found in the Isle of Purbeck, a peninsula in south-east Dorset, England. It is a variety of Purbeck stone that has been quarried since at least Roman times as a decorative building stone. Geology Strat ...

. The stone has been quarried since at least

Roman times In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC ...

up to the present day.

Geology

The Purbeck Group is a sequence of

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s that were deposited in a shallow freshwater to brackish lagoonal setting. It ranges in age from

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

Berriasian In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago) ...

. Limestone beds are developed at various levels throughout the sequence, each with a different character, which led to them being quarried for specific uses. Towards the top of the Lulworth Formation is the 'New Vein'. In the lower part of the Durlston Formation are the 'Downs vein, 'Freestone Vein' and the 'Laning Vein'. Towards the top of the Durlston are the 'Burr' (or Broken Shell Limestone) with up to three beds of the 'Purbeck Marble' above that.

Occurrence

The Purbeck Group rocks are found beneath superficial deposits from

Worbarrow Tout Worbarrow Tout is a promontory at the eastern end of Worbarrow Bay on Isle of Purbeck in Dorset on the south coast of England, about south of Wareham and about west of Swanage. Immediately to its east is Pondfield Cove. Worbarrow Tout ("tou ...

in the west, to

Peveril Point Peveril Point is a promontory on the east-facing coast of the Isle of Purbeck in Dorset, England, and is part of the town of Swanage. It forms the southern end of Swanage Bay. It is located at OS Grid Ref: SZ 041 787. The rocks that make up ...

in the east. The sequence is affected by the

Purbeck Monocline The Purbeck Monocline is a geological fold in southern England. The term 'fold' is used in geology when one or more originally flat sedimentary strata surfaces are bent or curved as a result of plastic (i.e. permanent) deformation. A monocline is ...

and dips moderately steeply to the north along its whole outcrop.

Extraction

Initially the stone was taken from shallow opencast workings but, as these became worked out, the quarrymen began to access the stone using shafts, up to 125 ft below the surface. These underground workings, the oldest of which dates from about 1650, were known as ''Quarrs''.

Use

Purbeck stone has been widely used as a building stone particularly in the Purbeck area. The 'Burr' and the 'Freestone Vein' were used as

ashlar Ashlar () is finely dressed (cut, worked) stone, either an individual stone that has been worked until squared, or a structure built from such stones. Ashlar is the finest stone masonry unit, generally rectangular cuboid, mentioned by Vitruv ...

. The dark colour of the Purbeck Marble meant that it was used for its decorative quality in churches and cathedrals across England, particularly for items such as fonts, tombs, flooring and shafts.

References

{{Reflist Building stone Geology of Dorset Isle of Purbeck Limestone