Harrow and Hillingdon Geological Society
WALTON-ON-THE NAZE, 27 July 2008 (by Allan Wheeler)
The Naze cliffs are an internationally important geological site with fine exposures of Red Crag (marine shelly sands; 2.5 million years old), and London Clay (Eocene, 50-55 million years old). The Red Crag and overlying sediments represent a remarkably complete sequence of late Pliocene/early Quaternary deposits which have yielded information on climatic deterioration at the beginning of the Quaternary Period, which began c. 1.8 million years ago (subject to international agreement).
Digging in the cliffs is not permitted but fossils can be numerous in the slipped masses. The Red Crag mainly yields molluscs such as bivalves and gastropods; the underlying London Clay is also fossiliferous and has produced some of the best preserved bird fossils of Tertiary age in the world. Sharks teeth also occur. Mammal bones (e.g. elephant, woolly rhinoceros and auroch – ancestor of today’s cattle) have been found in the Quaternary deposits - also whale bones. These deposits were laid down mainly during the Devensian glaciation (70,000-10,000 years ago) though in East Anglia the ice did not reach further than the north Norfolk coast. Fluvial sands and gravels from an ancestral River Thames, laid down before the river was diverted to its present course by ice during the earlier Anglian glaciation (350,000-250,000 years ago), also occur in the area.
After assembling in the cliff-top car park on what was to be one of the hottest days of the year inland, we descended to the Tower Beach and started slowly working our way north along it searching for fossils. On this occasion by far the most common material was pyritised wood from the London Clay. Also found were a couple of what could be bird bones, typically 2-3cm long; they are distinguished by a hole down the middle. In addition, a few shark teeth were found, also from the London Clay. The Red Crag yielded a variety of molluscs as already mentioned. Overall, however, we found fewer fossils than expected, probably either to do with the time of year or the fact that there had not been any recent storms to bring material down from the cliffs. This didn’t really matter, however, as everyone had a very enjoyable day, rounded off by very welcome tea and cakes in the car park café.