Lyme Regis - World famous fossil siteLocation: Lyme Regis
Rock type: Limestone and dark coloured mudrock
Age: Jurassic, 200 - 195 million years old
Look out for: fossils on the beaches.
Warning: Always follow the fossil collecting code
The geology in detail
The rocks in the cliffs at Lyme Regis represent layers from the oldest part of the Jurassic period and were layed down at the bottom of a deep sea between 200 and 195 million years ago. The shale layers that make up most of the cliffs East of Lyme are known as ‘black' shales because of their dark colour. The colour derives from the high amount of organic material included in the sediment. This tells us that the sea bed at the time must have been stagnant and had very little oxygen. Otherwise we would expect organic material of this kind to rot away and the shale to be a lighter grey colour.
The ancient environment
The nature of the rocks and the fossil contained within them points to a deep sea populated mostly by swimming creatures like ammonites, belemnites, fish, Ichthyosaurs and plesiosaurs. We know that this part of the world was much closer to the equator at the beginning of the Jurassic so it must have been a tropical sea. There were not very many creatures living on the sea bed because it was stagnant and they could not survive there.
The important thing about having a stagnant sea bed is that it is a perfect environment to preserve the remains of creatures as fossils. Sometimes fossils from these layers are so well preserved that traces of the skin can still be seen! The quality of fossils and their abundance in these rocks means that the cliffs around Lyme Regis are recognised as the richest source of lower Jurassic giant marine reptiles, fish and insects.
Small fossils are constantly being washed from the soft cliffs by the sea. After a storm it can be quite easy to collect a handful of fossils from the beach including ‘fools gold' ammonites, belemnites, crinoids and even fragments of bone. Regular guided fossil hunting walks run from Lyme Regis Museum.To the West of Lyme Regis there is a single layer of rock eroded into a wave cut platform that is covered in large ammonites. It is known as the ammonite graveyard or pavement and is a designated Special Site of Scientific Interest.