Discovering the Fossils of Lyme Regis along the Jurassic Coast of Dorset.
- Wayne Munday
- Jun 13, 2022
- 5 min read
Updated: Jun 16, 2022
Fossil Coast in collaboration with Matt Pinner one of Dorset's leading professional landscape photographers explores Lyme Regis the home of Mary Anning the Jurassic Coast's 19th century pioneering palaeontologist and fossil collector who helped shape our scientific understanding of prehistoric life.
(Image by Matthew Pinner)
Lyme Regis is a picturesque coastal town on the Devon – Dorset County border known as the "Pearl of Dorset". The cliffs, beaches and foreshore not only act as an enigmatic back drop to the town but are also the source of a spectacular diversity of fossils including marine reptiles, fish, ammonites and even dinosaurs over the last 200 years.
Before going on a fossil hunt Fossil Coast would recommend visiting the Lyme Regis Museum or the Charmouth Heritage Coast Centre and ask the experts on where best to explore.
The fossiliferous rock of Lyme Regis extends both east and west of the town. These exposed cliffs date back to the Early Jurassic epoch some 176 to 200 million years ago. This was a time when the climate was warm and moister than during the previous Triassic Period.
Mary Anning Memorial - Lyme Regis, Dorset
Transitioning from the Triassic to Early Jurassic
Before Lyme Regis would become one of the most famous fossil locations in the world there would be a tremendous amount of geological upheaval in transitioning from the Triassic to the Jurassic.
The area around Lyme Regis represents where the first normal marine sediments from the transgression of the sea over parts of the former Triassic desert and lagoons took place on the great supercontinent of Pangea. Hence, why the Lyme Regis fossil record is marine in origin.
During the Triassic Period over 200 million years ago Lyme Regis was located within a dry and arid desert of northern Pangea.
It was also at this time that life on Earth endured another major blow and experienced an extinction event 15 million years in the making.
By the end of the Triassic Period widespread volcanism across Pangea had warmed the Earth and carbon dioxide levels made the atmosphere and oceans increasingly difficult for marine creatures to survive in low oxygen environments.
Pangea in the early Jurassic epoch was still mostly intact though rifting or the natural process of splitting apart the supercontinents tectonic plates into comparatively smaller tectonic plates was well underway.
Rifting was not only responsible for creating mountain ranges across Pangea it also led to widespread volcanism and earthquakes. The newly formed tectonic plates would become separated by divergent plate boundaries where the plates moved away from each other allowing magma or molten rock to rise from the Earth's mantle to the surface solidifying and create new oceanic crust affecting relative sea level.
As Pangea transformed and subsided the relative sea level was higher and the sea encroached on land. The continental land around Lyme Regis became initially flooded with brackish lagoons until eventually becoming marine and submerged by the sea.
The characteristic sedimentary black rock or Blue Lias Formation both East and West of Lyme Regis is known for its abundance of fossils and its extensive and active landslide areas of of ‘Black Ven’ and ‘Stonebarrow Hill’.
Exploring Black Venn to the East of Lyme Regis
The best fossil hunting beach of Lyme Regis is to the East of the town in an area known as Black Venn and The Spittles. This area is renowned for a number of globally important fossil finds including Mary Anning's first complete Ichthyosaur ("fish lizard") and James Harrison's find in 1858 of a 193 million year old “Scelidosaurus", an early member of the evolutionary lineage that led to the dinosaur group called ankylosaurs.
This area is now watched over by the Mary Anning statue placed by Church Cliff beach close to her birthplace and where she hunted for fossils.
This statue was inspired by Evie Swire aged 15 who campaigned for four years to raise over £100,000 for the memorial.
The statue of Mary Anning created by Artist Denise Dutton and was unveiled by Prof Alice Roberts on the 21st May 2022 on what would have been Mary's 223rd birthday.
The main feature of The Spittles and Black Ven is its landslides one of largest active landslip systems on the south coast of England. The geology of this area prone to landslips because of the porous nature of the rock that can become easily waterlogged. However, the underlying clay layers beneath are not porous creating a ‘slip-layer’ when wet, allowing the sedimentary layers above to easily slide over.
More recently on the evening of 6th May 2008 a landslide occurred after a particularly wet period during winter and early spring when the “Shales with Beef” (fantastic name!) and part of the Charmouth Mudstone failed above the Blue Lias and slid over the cliff onto the foreshore. Over the years the waves have eroded the loose rock in this area and continues to release fossils along with a few other surprises.
Exploring Monmouth Beach to the West of Lyme Regis
The predominant marine geology of both East and West Lyme Regis is it onshore Blue Lias Formation. The exposed cliffs and foreshore of Monmouth Beach beneath Ware Cliffs is great place to explore the Blue Lias Formation. This formation is overlayed on the foreshore by the Shales-with-Beef, Birchi Tabular and Black Ven Marl Members.
The term “Lias” signifies the earliest of the three sub-divisions of the Jurassic Period and is understood to take its name from the Old French word ‘liais’ referring to a hard layered mudstones interlayered with limestones.
This distinctive formation is made up of laminated layers of black organic-rich oil shale followed by rhythms of dark then pale marls sometimes cemented into hard pale argillaceous (“clay rich”) limestones beds, nodules and boulders.
The Blue Lias of Lyme Regis in Dorset is part of the Wessex Basin and is one of Britain’s most significant outcrops of the Lias Group. This group can also be discovered in the sea-cliffs on the coasts South Wales, and Yorkshire between Robin Hood’s Bay and Redcar.
The alternating black oil shale and marls reflects the circulation of the sea during the time that Pangea was breaking up. The black oil shales were laid down when the sea had a restricted circulation and subsequent oxygen reduction on the coastal margins and marine shelves creating low oxygen conditions. The black oil shale is a good sedimentary biomarker for environmental change during the Early Jurassic.
Laying on top of the Blue Lias is the superbly named dark mudstone called Shales-with-beef a member of the Lower Jurassic Charmouth Mudstone Formation.
This is a complex organic-rich mudstones and calcareous ("calcium rich") mudstones with numerous thin beds of fibrous calcite called “beef”.
The key characteristic of the shales-with-beef is their diagenetic origin or sediments that have been influenced by the process of physical and chemical changes by water-rock interactions, microbial activity, and compaction after their deposition.
Fossil Hunting in Lyme Regis
Fossils are mostly found on the foreshore and in among the rocks and boulders at Lyme Regis, but can also be found at the bottom of scree slopes, slippages and occasionally the cliff. When exploring for fossils make safety a priority and follow the fossil hunting safety guidelines.
If the tide and sea conditions are not favourable there will be an increased risk of rock falls, landslide or mudslides. Fossil hunting in Lyme Regis is best undertaken in the foreshore and between the rocks. As per the guidelines it is not permitted to hammer into the cliff or bedrock.
The fossils of Blue Lias of Lyme Regis have included the dinosaur Scelidosaurus, marine reptiles including ichthyosaurs, plesiosaurs, pterosaurs known as Dimorphodon ("two-form tooth") and many species of ammonites including Crucilobiceras, Eoderoceras, Echioceras, Oxynoticeras and pavements of large ammonites.
Other fossils found with in the Blue Lias include Psiloceras planorbis, Alsatities liasicus, Schlotheimia angulate and Arietites bucklandi, and Arnioceras semicostatum The Black Ven Marl is well known for pyritised or “fools gold” ammonites (Eoderoceras) and the Shales-with-Beef are known for calcified ammonites (Promicroceras).
As ever enjoy fossil hunting and always expect the unexpected and be safe.
