Geology Site Account

In the 1950s the cliffs Holland-on-Sea consisted of 3 to 5 metres of London Clay beneath an even thicker cover of Ice Age gravel (Holland Gravel). Good exposures of London Clay were also available on the foreshore with pieces of fossil wood, other plant remains such as fossil fruits, and small sharks teeth.

Much pyrite debris from the London Clay was present at the foot of the shingle which contained abundant pyritised stems of the characteristic crinoid or sea lily Balanocrinus subbasaltiformis and several internal moulds of gastropds. Two layers of septarian nodules occurred, above and below high tide mark, with their surfaces encrusted with trace fossils of worms and other animals that weather out in relief. Large burrows up to 15 centimetres long and 2 centimetres in diameter, packed with faecal pellets, were abundant and there were also spiral moulds made by unidentified marine creatures.

These remarkable trace fossils demonstrate that the mud on the London Clay sea floor some 50 million years ago was intensely burrowed (bioturbated) but the only evidence of this is found on the surfaces of the septarian concretions.