The Fossils in the Naracoorte Caves - Movement of the Layers

Bones and sediments are mixed up over time by water and trampling

Rain falls through open roof entrances, washing sediments from one area to another

Water may collect in circular depressions (dolines) above cave entrances that have become blocked by the tops of sediment cones.

Eventually the upper portion of a cone may collapse under the weight of saturated sediment, thus unplugging a cave entrance.

Sediment then slumps down the sides of the cones to be redeposited further inside the caves.

Once open, subsequent rainfall causes more runoff into the cave, and the gradual slumping of sediment.

Bones within the sediment may be redistributed by this process which leads to mixing of layers and separation of skeletons. 

More often though, bones are moved about and disarticulated following trampling by trapped animals that stumble around in the dark looking for escape.

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