The Charmouth Dinosaur

The cliffs around Charmouth hold a mystery. A local fossil collector, David Sole, has found the remains of a dinosaur, Scelidosaurus, but just how did a land dwelling reptile end up at the bottom of this deep Jurassic sea?

The Jurassic Sea and Fossils

The Jurassic clays around this area formed in a deep tropical sea, the soft muddy bottom of which was often stagnant, creating a sulphurous and anoxic environment, the best conditions for preserving the shells, bones and even soft tissue of dead prehistoric creatures.

The Cretaceous Blanket and Cliff Erosion

From the air, the instability of the cliffs along this stretch of the Jurassic Coastline is clearly visibly and they are eroded in several different ways. From above, and where the cliff is capped by Upper Greensand, rainwater seeps through to the underlying impermeable clays. As the water builds up during prolonged periods of rainfall the cliffs below fail to support the extra weight and pressure from above, creating a landslide. From below, the sea erodes away the cliff base. As more and more sediment is removed, the deposits of clay and shale above become less stable, resulting in cliff falls onto the beach, where the process then starts all over again. This is why the cliffs here are so unstable and why it is a good idea to keep away. Mary Anning’s faithful dog was killed when a section of cliff fell on him.

The Great Unconformity and The Cretaceous Blanket

The sediments which make up the Jurassic Coastline were deposited in the following order, Triassic, Jurassic and Cretaceous, with the oldest rock, the Triassic sitting at the at the bottom of the pile.