Report of the Essex Rock & Mineral
Society’s visit to:
Walton-on-the Naze Sunday 14 August 2005
by Gerald Lucy
The Society’s annual visit to Walton-on-the-Naze was on 14th August and was a joint visit with the Nationwide Geology Club. At least 15 people attended which included several from the Nationwide Geology Club who had travelled from places as far afield as Oxfordshire and Kent. A few of them had not been to Walton before.
We met at 10.30 am in the Naze car park and after a brief introduction (which included a comment on the outrageous cost of parking here during the Summer) we made our way down the steps and across the slumped cliffs to examine the sands of the Red Crag which is of Pliocene age and, as usual, crowded with fossils. Laid down as undersea dunes on a shallow sea bed the currently accepted age for the Red Crag at Walton is around 3 million years. The London Clay, which forms the lower part of the cliffs, was laid down on the floor of a muddy, sub-tropical sea during the Eocene period around 50 million years ago. After a look at the cliffs the party went down on the beach in search of shark teeth which proved to be elusive. Fortunately a local family, obviously skilled in the art of shark tooth collecting, were scouring the beach nearby and they were willing to show their finds which spurred the party on to find some. An hour or so later most of us had found not only shark teeth but also other fossils such as fish vertebra, fragments of crabs or lobsters or plant material from the Eocene rainforest such as seeds and twigs. Pieces of whale bone from the Red Crag / London Clay junction can normally be found on the beach but were very scarce on this occasion.
Later on some of the party moved north along the beach to see the layers in the London Clay cliffs that are rich in volcanic ash from Eocene volcanoes probably in Scotland. Also of interest were several conspicuous faults in the London Clay and a discussion took place on whether the faults would have been responsible for local earthquakes and when the faulting was likely to have occurred.
At the very end of the day, after most members had departed, I was walking back along the slumped cliffs when I came across what appeared to be a magnificent fossil ice wedge in the cliffs which could not be seen from the beach. Evidence of the most recent glacial stage some 20,000 years ago, ice wedges are formed when the frozen ground shrinks and cracks during times of extreme cold. Each summer the cracks filled with water and debris which then froze the following winter widening the cracks; a process that continued for thousands of years. At the end of the glacial stage the cracks completely filled with debris preserving them as ice wedge casts.
Apart from a couple of brief showers of rain the weather was fine and it was an enjoyable day.
All text and photographs © Gerald Lucy 2005