Two ancient environments in one coast
The cliffs and foreshore at East Mersea preserve evidence from rivers and climates very unlike today's estuary. Sands and gravels deposited by the Thames–Medway river system around 300,000 years ago form a conspicuous part of the cliffs. Below and beside them are sediment-filled channels with shells, plant remains and vertebrate fossils.
Changes in the layers from gravel to silt and organic mud record shifts in the strength of flowing water and the conditions in the channels. The same exposure cannot be described as one single fossil bed.
The Cudmore Grove river channel
An older channel has produced remains of beaver, macaque, bear and other mammals, alongside an exceptionally varied assemblage of smaller vertebrates: rodents, birds, amphibians and fish. Fossil wood and pollen help reconstruct the surrounding vegetation. A worked flint flake was recovered near the base of the deposit, adding archaeological interest to the geological record.
The later hippopotamus-bearing beds
Separate foreshore deposits belong to the warmer Ipswichian interglacial around 120,000 years ago. Finds include hippopotamus, straight-tusked elephant, bison and giant deer. A related exposure at Coopers Beach, known in geological literature as the “Restaurant Site”, has also yielded material from this period. It is a scientific locality name, not a recommended business or visitor venue.
The layers can be compared to reconstruct former rivers and estuary conditions, but they were deposited at different times. The Essex Field Club's Cudmore Grove account sets out the principal discoveries and scientific references.
Erosion: exposure and loss
Waves remove material from the low cliff and at times reveal layers that were previously buried. Erosion also destroys their original setting, and nearby archaeological structures are affected too. Cudmore Grove's foreshore is part of a Site of Special Scientific Interest. Cliff faces should not be dug into or climbed.
Seeing the geology
From safe public routes, look for the contrast between loose shingle, bedded sands and gravels and darker fine sediments. The important point is the relationship between layers, not whether a fossil can be taken home. See the fossil-observation guide for access and safety, or East Mersea's blockhouse for the adjoining archaeological landscape.