The A38 road on its way to Plymouth passes the edge of the Dartmoor granite, the intrusion of which had interesting effects on the local Devonian rocks, - a patchwork of volcanic tuffs, limestones and shales. At Ashburton, the almost black limestone has been recrystallised, and the material in the joints and fissures fused together and produced a network of pink and red coloured veining. This hard limestone has long been quarried for ornamental polished ‘Ashburton’ marble. The rock is cut out by wires (no blasting is allowed) into large blocks and then finished at Jenkins Marble Works in Torquay.
Another material worked in the past, in this area was umber, a brown hematite, a fine grained residual deposit found in pockets in the limestone.
Two miles further south is Buckfastleigh Hill, a prominent landmark as the parish church stands on the top. This hill is an isolated block of limestone surrounded by shales which have produced the lowlands. Both are underlain by volcanic tuffs. All formations have been affected by faulting and thrusting during the Hercynian orogeny, and later cut by dykes and mineral veins from the Dartmoor granite intrusion. The limestone of this hill has been used for building and lime burning since earliest times. The monks used stone from Bulleycleaves quarry for the first Buckfast Abbey in 1018, a quarry which ceased working only a few years ago. The other quarries, Bakers Pit, Higher Kiln, and Fairies Hall have long since been abandoned. However in all these quarries caves have been found, in fact a large system with over 7000 feet of passages has been discovered in Buckfastleigh Hill.
In 1961 the whole system was taken over by the Society for the Promotion of Nature Conservation, and management of it handed the Devon Trust for Nature Conservation. Higher Kiln quarry was purchased and a Cave Science Museum and Study Centre built. The centre has been named after William Pengelly 1812-1894, a Devon geologist who spent much of his life scientifically excavating caves in this part of Devon, especially Kent’s Cavern at Torquay, and Windmill Hill cave at Brixham. This latter cave was newly discovered in 1858 undisturbed, a rare thing to happen, so it gave an accurate picture of the fauna and geology inside.
The extensive cave system in the limestone seems to be related to the beds of volcanic tuffs which act as cave floors. All too, are of Pleistocene age, and between 200’ and 270’ O.D., so it is assumed that during a time when the sea level was higher than at present, and about 1/2 million years ago the river Dart crossed the top of Buckfastleigh Hill, leaving behind derived pebbles from Dartmoor. The water penetrated the joints and fissures of the limestone creating an underground river system. As the sea level fell the Dart deepened its valley and when the water table began to fall the caves were gradually drained until today they are dry.
From Higher Kiln quarry the cave system can be entered through five openings in the quarry face. Of these the Joint Mintor cave, noticed only in 1939, contains in a talus scree of earth and stones remains of hippos, rhinos, elephant, pig, deer, bison, hare, wolf, wild cat, cave lion, hyaena, badger and bear. All are remains of animals living in warm conditions, i.e. interglacial times. This is the largest mammalian deposit yet found in Britain. Reeds cave contains the best stalagmite formations, and Rift cave is a bat roosting site.
It is possible to visit the Centre at Higher Kiln quarry with prior notice. The address is: William Pengelly Cave Studies Centre, Higher Kiln Quarry, Russets Lane, Buckfastleigh, Devon. From Exeter leave the A38 at exit for Buckfastleigh, turn right over the river Dart, then left to village. Go slow to find Russets Lane on the right. It is a sharp back turn up the lane to the Centre. Grid Ref. 744/665.