Purbeck marble
Purbeck marble is a fossiliferous limestone found in the Isle of Purbeck, a peninsula in south-east Dorset, England. It has been quarried since at least Roman times as a decorative building stone. This industry is no longer active.
Geology change
These limestone beds were deposited during Lower Cretaceous epoch. Purbeck Marble is not a metamorphic rock, like a true marble, but is so-called because it can take a fine polish. Its characteristic appearance comes from densely-packed shells of the freshwater snail Viviparus.[1][2] Sussex Marble is similar in type. The 'marble' large clasts (the snail shells) in a fine-grained limestone mud matrix.[3]
The individual marble beds (also known as 'seams'), lie between layers of softer marine clays and mudstone, laid down during repeated marine ingressions.[4] Some of the beds contain iron oxide/hydroxide minerals, such as haematite or limonite, giving red or brown varieties, while other beds contain glauconite giving a green (or occasionally blue) colour.[3]
Occurrence change
Purbeck marble is found at outcrop, or beneath superficial cover, all the way across the Isle of Purbeck. The marble beds are never more than 1.2 m thick and are often much thinner. The outcrops lie within the Purbeck Monocline, with the beds dipping moderately steeply to the north.[5]
References change
- ↑ Arkell W.J. 1947. Geology of the country round Weymouth, Swanage, Corfe Castle and Lulworth. London: HMSO for British Geological Survey.
- ↑ Clements R.G. 1993. Type-section of the Purbeck Limestone Group, Durlston Bay, Swanage, Dorset. Proceedings of the Dorset Natural History and Archaeological Society, 114, 181–206.
- ↑ 3.0 3.1 West, I. "Durlston Bay - Peveril Point, Durlston Formation, including Upper Purbeck Group". Geology of the Wessex Coast (Jurassic Coast, UNESCO World Heritage Site). Retrieved 10 November 2012.
- ↑ When the seal level rose, and the sea moved inland.
- ↑ Phillips, J. (1996). "Quarr Houses on the Isle of Purbeck, Dorset" (PDF). Mining History. 13 (2): 155–162. Archived from the original (PDF) on 28 March 2012. Retrieved 10 November 2012.