Geology

Jacob's Ladder

Sidmouth lies within a wedge of the Otter Sandstone (245 - 235 million years old) exposed due to faulting to the west of the town that interrupts the general eastward dip of the rock layers. Westward the Otter Sandstones disappear from the cliffs under Peak Hill replaced at beach level by the Mercia Mudstone group (235 - 204 million years old). Approaching Sidmouth from the west there is a fault that exposes the Otter Sandstones again and results with them suddenly appearing in the cliff face adjacent to the younger Mercia Mudstones. East of the town the eastward dip causes the Otter Sandstones to disappear again below beach level, replaced y the Mercia Mudstones. Both sequences are red indicating they formed in an arid environment.

The Otter Sandstone at Sidmouth is particularly well known a source of Rhynchosaur fossils. These strange creatures grew to about 2m, walked on four legs and fed on plants that grew in the sandy river plains. They are described as mammal-like reptiles and have no close relative today. Although the fossils of Rhynchosaurs are very rare important specimens have been collected form the Otter Sandstone at Sidmouth and Ladram Bay. The Otter Sandstone is regarded as a globally important site for Triassic fossils.

The ancient environment

The Otter Sandstones formed after a brief very dry period and were deposited by large braided rivers. The red colour of the rock indicates the landscape must have been arid but, with the rivers offering a source of water, plants and animals could colonise the area. There were also a variety of animals inhabiting this environment including Rhyncosaurs and other early reptiles. The harsh arid conditions and fast flowing rivers at this time meant that remains of these creatures were rarely fossilised.

source: http://www.jurassiccoast.com/