Fossilised mud-cracks
Description:A photograph of fossilised mud-cracks. The caption at the back of the photograph reads "Mud deposits crack very readily when exposed to the air. These fossilised mud-cracks (some 450 million years old) are infilled with sandstone. They demonstrate that the original sediment which formed this rock was exposed to the atmosphere and therefore deposited in very shallow water.".
Subject headings: Geology -Fossils -Mud