Fossil Hunt at Ramsholt – 10th June 2018

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On Sunday June 10th UKAFH visited Ramsholt, located on the river Deben in Suffolk. We met near the Ramsholt Arms, a popular pub with tourists and boaters, then walked about 2 miles north through woodland and along the river bank before reaching a shingle beach where fossils are abundant.

UKAFH leader Sam Caethoven explained the geology and pre-history of the site and provided an example of likely finds.

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There are three distinct deposits exposed at Ramsholt. The base of the small exposed cliffs and the foreshore consist of London Clay, a roughly 50 million year old marine deposit commonly exposed on the south east coast from which many bivalves, gastropods, crabs, lobsters, shark and ray teeth, fish, reptile and mammal remains can be found. Above the London Clay sits the Coralline Crag formation, a much younger (~ 5 million year old) sandy sediment containing numerous bivalve and gastropod remains. As the name suggests, the formation does contain corals however more common here are bryozoans, which can often be found with corals seeded within their chambers. The 5 million year old Coralline Crag comes to lay directly on top of the 50 million year old London clay as the underlying sediment was eroded before the Crag formed, this has resulted in a diversity of derived fossils in what is called the Basement Bed, directly above the Coralline Crag and forming the base of the roughly 2.5 million year old Red Crag above it. Derived fossils are those which, having become fossilised in one deposit have since been eroded out, often transported by rivers or tides, and become part of a much younger sediment. This means that, within the basement bed, fossils from the Eocene and Miocene can be found and even Cretaceous belemnites and crinoids have been found within the basement bed. The effects of “refossilisation” of shark teeth here are striking; the teeth are often polished and the colours derived from exposure to different elements are diverse and vivid. Marine mammal bone fragments, often attributed to whales, are also common from this bed and have become silicaceous in their preservation. The iron rich Red Crag above is also noted for well preserved and often complete bivalves and gastropods.

Finding fossils here is relatively easy as they can be found in abundance among the shingle of the foreshore – the site is SSSI protected and so digging in the cliffs or the exposed clay on the foreshore is prohibited. With fine, dry and warm weather it was not long before the group began making discoveries. Gastropods and bivalves from the Red Crag and Bryozoans from the Coralline Crag were the first fossils we noticed as we progressed north along the foreshore.

But it was not long before shark and ray teeth were being found, some fantastically preserved and some with vivid red, orange and even blue colours. Daniel Austin found a particularly rare and large Isurus tooth while Eliott Mills found an uncommon large Otodus tooth.

Other notable finds included some large pieces of marine mammal bone and a delightful although heavily worn crab carapace found by Aidan Philpott.

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