micraster
UKAFH Visit Seaford, Sussex 28th April 2019
On Sunday 28th April, UKAFH ventured along the coastline of Seaford in East Sussex – a small town about 10 miles east of Brighton with towering white cliffs.
As we arrived in the carpark at Seaford Head we were grateful that storm Hannah had passed the night before, not least for the erosional effects of the storm but for the light winds, mild temperatures and intermittent sunshine that greeted us.
We began with an in depth talk about the local and surrounding geology by UKAFH leader Daniel Slidel. Exposed in the towering white cliffs of Seaford is the Upper Chalk, a Cretaceous deposit (Santonian-Campanian) about 89-83 million years old. Chalk is essentially a soft limestone formed from the tiny platelets of coccolithophores – phytoplankton that was abundant in the deep, warm sea that existed here. This striking white sediment helped preserve the creatures dwelling on the sea floor, which included bivalves, sponges, corals, bryozoan and the echinoids (sea urchins) this stretch of coastline is famous for. Within the cliffs are horizontal bands of flints which are visible as far as the horizon allows and atop, the undular pattern formed by dissolution pipes – where mildly acidic rain water has dissolved the chalk to form channels.
After a short walk from the car park we descended the concrete steps onto the beach. The abundance of fossil echinoids was immediately noted as within the exposed bedrock on the foreshore were the tell-tale circular marks of weathered echinoids in situ. Tara Scott made the first discovery with a lovely echinoid preserved in flint just meters from the steps, then Susan Harley found an exquisite Micraster echinoid in situ – we could not extract these as the bedrock here is protected as a site of special scientific interested, however we continued heading west where loose boulders gave us the opportunity to carefully extract some specimens. Leo Leclerc manged to extract a great Echinocorys and Xiang Yan extracted a fantastic Micraster, both of which with their delicately preserved calcite teste intact. It is important not to overlook the loose flint shingle either as these can contain robust but often sea word specimens such as a big Echinocorys found by Aidan Philpot and a lovely little on found by Susan Harley. Other finds on the day included small bivalves, shapely sponges, coral and bryozoan.
Thank you to everyone who attended this fossil hunt. It really was a great and friendly group of people, it was a pleasure to guide you through the Cretaceous geological history of Seaford.
Further Reading.
Hampton, M.J., H.W. Bailey, L.T. Gallagher, R.N. Mortimore and C.J. Wood 2007. The biostratigraphy of Seaford Head, Sussex, southern England; an international reference section for the basal boundaries for the Santonian and Campanian Stages in chalk facies. Cretaceous Research, v. 28, no. 1, p. 46-60.