Harrow and Hillingdon Geological Society

Kent Coast

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Kent Coast Field – Trip
Saturday 22nd May 2010

We left home in warm sunshine at 8.30 am with expectations of a sweltering day on the coast. We arrived at Herne Bay at 10.15 am to a rather chilly and misty car park well ahead of our start time, good job I’d thrown my fleece in the car, at the last moment.
Soon the rest of the party arrived, plus a family of ‘Rockwatchers,’ Jean, Max and Harry.
This was to be a ‘self led’ day, so we decided to spend the morning here, have lunch in the car park, then move on to the second location, Pegwell Bay, in the afternoon. The itinerary said that we should be able to find sharks’ teeth on the foreshore, washed out of a pebble band in the Thanet Sand Formation, and bivalves in the London Clay, plus pyritised wood, seeds and bivalves.
We made our way down to the beach and looked back at the cliff exposures from the water’s edge; we could see the black pebble band from which the shark’s teeth are derived high in the cliff face. After a short walk along the beach we discovered the wave-cut exposure of the London Clay (Upnor Formation) and the bivalves that it contained, the ‘Rockwatchers’ at this point, were busy with capturing invertebrates and crabs (alive and dead, but mainly dead).
A few minutes later I spotted a striated black object amongst a lens of black smooth pebbles, it turned out to be a large shark’s tooth with side cusps, the first of the day. Soon everyone was picking them up, and a small vertebra for good measure, much to the delight of the Rockwatch boys and the relief of the crabs, (dead and alive). At 1.30 pm we headed back to the car park for lunch and to show off our finds to Jean (the Rockwatchers’ Gran) who was unable to get to the beach.
In the afternoon we said goodbye to the Rockwatchers and made the short drive to Pegwell Bay where we had an ice cream, as the temperature had rocketed, then on to the beach to check out the cliff section.
The base of the cliff was Upper Chalk, which looked like balls of white chalk (100 – 200mm dia) packed together with more crushed chalk. This was formed by periglacial freeze-thaw action during the Pleistocene. Laying unconformably on top of this was the Thanet Sand Formation of channel deposits – silts, sands and gravels – the international type section for the Thanetian stage of the Palaeocene. And over this was a blanket 1-2 metres thick, of pale brown loess, capped with soil. At the unconformity there were structures very similar to those described by Professor Philip Collins of Brunel University at one of our recent evening lectures. Liquefied chalk appeared to have been injected up into the loess by approx 300-400mm. As we progressed further eastwards the “ball chalk” gave way to the more usual blocky jointed structure. The similarity between the photos shown in Philip Collins’ lecture and what we saw today led us to believe that similar processes were at work here also.
Unfortunately the café in the car park was closed by the time we returned so after a look at the replica Viking longboat we made our way home.

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