Beer quarry Devon

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http://youtube.com/watch?v=B4Kq8e_aUu0

Beer underground quarry in Devon. • Beer Stone • Beer Freestone is a Chalk Limestone laid down in the Cretaceous age (65 – 140 million years ago). 120 million years is the estimated time for lower layers. Early in the period climatic conditions were like the Gulf of Arabia is now, with lush warm swamps populated with dinosaurs. Then Earth movements deep under south west England tilted rocks to the east. As the Atlantic and Mediterranean expanded a vast sea developed over the area.There were high CO2 levels and no ice cap. • 98 percent of chalk is composed from microscopic planktonic plant remains – coccoliths, but at Beer there was a current flowing across the seafloor and this winnowed away the coccoliths leaving a fine shelly Limestone made from the well cemented calcite crystals derived from broken sea urchins, refined clay and sand. As water squeezed out increasing pressure led to the formation of pure white chalk by lithification. • Freshly quarried Beer Stone is saturated with water and with very few fossils was much prized by the masons as it is ideally suited to fine detail carving. It is found in a 13 – 20 foot (4 – 6m) seam running North to South below other chalk layers. On exposure to the air it dries creamy white and becomes up to 5 times harder, remaining durable for centuries provided it is laid in the same plane in which it was formed. • Chalk or Limestone? “Chalk” is a variety of “Limestone” which is composed primarily of the shells of single-celled, calcium carbonate secreting creatures. (As opposed to multi cells e.g. bones, teeth and shells). • Above the caves the chalk seam is topped with unconsolidated clay with flints dating from the Eocene Epoch (about 56 to 34 million years ago ) and later sediments from the Pleistocene age (the last Ice Age approx. 1.8 million to 10,000 years ago). Solution weathering of the chalk surface enlarged cracks in the chalk, which were later infilled with the clay to form “clay pipes”. • https://www.beerquarrycaves.co.uk/bee...

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