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The Sequence of Deposits

The deposits of Joint Mitnor Cave occur as a filling in a cavity in rocks laid down as sediment in the area, during the Devonian Period, more than 300 million years ago. The cave walls and ceiling are limestone and the floor is tuff (volcanic ash). The cave was formed by solution of the base of the limestone, probably during the last million years and susequent appears to have continued until less than 70 000 years ago.

The lowest layer of cave fill is a chemical sediment. This is derived from the limestone and tuff containing mineral veins associated with the Dartmoor granite only two miles away.

1. This deposit is overlain by unfossiliferous water laid sediments containing Dartmoor-derived river pebbles. Until this stage the River Dart apparently flowed across the top of Buckfastleigh Hill and the cave was entirely water-filled. Some pebbles from the river bed found their way into the flooded cave beneath.

2,3. Slight sludging of the surface of (1) was followed by the accumulation of a conical talus of earth and stones containing many mammalian bones. The high angle of rest of the layers of this deposit and lack of sorting of the particles in it indicate that it was not water-laid. By this time the water-table had apparently fallen below the level of the cave, as a result of valley downcutting by the River Dart. A water-level on the cave wall represents an intermediate stage in the downcutting.

The talus deposits piled up beneath a shaft in the roof of the, by now, dry cave into which animals, as well as earth and stones, sometimes fell. This shaft finally became blocked with no further infilling.

Species Present

Animal remains occur only in the lower part of the talus cone and all are apparently contemporaneous.

Herbivorous animals (such as bison and deer, some of them juvenile, others very old) which make up the greatest part of any natural surface fauna, are very numerous, whereas there are fewer remains of carnivores. This further supports the view that the cave was a pitfall. Remains of hyaenas, though numerous, are with one exception of adult animals. The cave does not appear to have been a breeding place of these animals or of bears, as were other local caves such as Tornewton Cave and Kent's Cavern.

Dating Remains

The kinds of animals present provide the most important clues to the age of the remains. All are either animals characteristic of warm climatic conditions (hippopotamus, straight-tusked elephant, narrow-nosed rhinocerous and fallow deer) or are of no climatic significance (hyaena, wolf). "Cold climate" species such as woolly mammoth, woolly rhinocerous and reindeer (abundantly represented in many other caves in this district) are absent.

All remains appear to date from one of the three warm or "interglacial" periods which ocurred between cold phases of the Ice Age, during the coldest part of which the Pleistocene ice sheet extended as far south as North Devon and the Scilly Islands. The Joint Mitnor faunal assemblage is characteristic of the last of these interglacials. The remains are probably about 100 000 years old.

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