Another week another hunt! Great stuff! This week we were visiting the late Cretaceous deposits of the Gault Clay and Lower Greensands at Folkestone, Kent. The geology at Folkestone is Albian age, between 90 and 112 million years old. Although there are chalk exposures east of Folkestone, our focus today was west from the beach entrance at the Warren heading towards Copt Point.
We assembled in a quiet residential street (I think the locals have got used to our occasional assemblies of yellow jacketed, hard had wearing groups!) and Sam gave a superb talk with some great show and tell fossils. The rocks at Folkestone we’re formed in a shallow marine environment so the fossils include molluscs such as ammonites, belemnites snd bivalves as well as corals, sharks and other fish, urchins, turtle and occasional marine reptile remains. However the seasonal dryness in the locality is evidenced by scarce dinosaur footprints. Many fossils are exceptionally preserved, retaining original shell preservation, due to the soft and highly anaerobic clay which preserves aragonite and calcite shells in beautiful, iridescent colour. Chris, our leader on the day, briefed the group on the locality and a couple of health and safety messages and we headed down to the beach carefully, then heading West from the chalk to what we hoped would be much exposed clay.
We totally beat the weather forecast, with many of us stripping off the full waterproofs for much of the excursion, and got away with only a couple of showers. Unfortunately we could not contend with the abundance of sand covering a lot of the clay so a chunk of the areas we are used to hunting were covered. This did not mean it was an unproductive hunt though and more than I was expecting was found! Yay!
The first fossils encountered were from the freshly slipped clay. The colourful shells of the bivalves within were evident but were too fragile to collect and we also found an unusual number of equally fragile heart-shaped urchins.
A very large and exceptionally well preserved shark tooth was found by Jo and Isabel and Peter Bines continued his hot streak, finding a little tooth that would have gone unfound without his persistent sieving efforts as well as part of a chimaeroid fish tooth palate which has a distinctive spotted texture and can be found in both the Gault clay and Greensand.
Suzanne, a first time guest was pleased to find some iridescent ammonite sections and see the beautiful but fragile bivalves which look gorgeous on the beach but have a short shelf life once exposed. Meanwhile Louie Fleckley found some beautiful complete ammonites!
Other finds on the day included crinoid stems, a fish vertebra, a solitary coral, many ammonites and ammonite fragments including sections of heteromorph (irregular/uncoiled) ammonites which are unusual but quite common at Folkestone and yet another great find from hawk-eyed Peter who found a beautiful small crab carapace.
Everyone had a fun time and it was absolutely lovely to wander up to Sam and hear that our youngest guest of the day Louie wanted to tell her before he went home that he had a great time and thought we were all lovely! Thanks for the great feedback and that is exactly why we do this. We love to encourage and inspire and share our love for fossils!
Roll on the next hunt!
On Saturday 14th October UKAFH took a group out to the Warren, Folkestone for day one of the Kent weekender. We were blessed with unseasonably warm weather as our group of 30 descended the (pleasantly dry) mud footpath down to the beach to begin our hunt through the Cretaceous period! Once on the beach, UKAFH leader Chris Tait briefed the group on the geology of the location and what we might expect to find.
The rocks at Folkestone represent the Albian stage of the lower Cretaceous, 110-105 mya. Lower Greensand is found at the base of the cliff with Lower and Upper Gault clay resting conformably atop, however the clay slumps over the Lower Greensand and is eroded at sea level to release large volumes of fossils onto the beach in this highly productive locality for fossil hunting. During the time these sediments were laid down the UK was at a more southerly latitude in the area of the modern day Mediterranean and a warm sea teeming with life covered the UK. During this time sea levels were transgressing, with the Lower Greensand being deposited as and continued to erode, to be replaced with fine clay sediments once nearby land was completely submerged.
The Lower Greensand is less fossiliferous as the near-shore environment it represents was less suitable as a habitat but still contains excellent fossils such as ammonites; the Gault Clay, however, is packed with diverse fossils, some with exceptional preservation. Ammonites, belemnites and molluscs are common; nautilus, crabs, crinoids, fish remains, shark teeth and scaphopods can be found, along with rare finds of reptilia. Examples of all of these were found by members of our hunt group!
Phosphatised preservation is typical but quality is variable, with examples often fragmented or in nodules. However many examples are preserved in superb detail in pyrite and those which are newly emerged from the clay can retain some or all of their nacrous shell. Bivalves and molluscs which are newly exposed are often extremely fragile and are rarely collectable unless carefully removed along with the surrounding clay, but ammonites are more durable and make marvellous specimens to add to a collection.
Soon after we reached the beach heading towards Copt Point the finds were already plentiful. Partial regular and heteromorph (partially uncoiled) ammonites and bivalves were quite common and finds increased as people “got their eye in”. Some of the group progressed quite quickly along the beach to inspect the slips of clay for freshly washed out fossils and check out the shingle between the large rocks and boulders on the foreshore. Others remained nearer the start of the beach, working methodically through the shingle by hand, with a trowel, or dry sieving, in search of smaller finds like shark teeth.
Several members of the group found shark teeth, with Isabelle finding the largest example. At the other end of the scale, Sam found a small but scarce Acrodus shark tooth while sieving using a 3mm mesh. Sieving is a good technique to remove sand and search for small fossils which wash out higher up the beach because they are lighter. Sieving and shingle-searching up the beach yielded crabs, solitary corals, urchin spines, shark teeth and vertebrae as well as fish teeth, a turtle bone and the day’s star find, a swordfish tooth!
By the end of the day we had a really great selection of finds amongst the group!
The following day we were greeted with yet another gloriously sunny autumn day, enhanced by the towering white cliffs of Dover above our meeting point as Samphire Hoe Country Park. We had another full house of attendees and headed west along the beach to hunt for fossils amongst the chalk boulders on the foreshore. Aidan Philpott, UKAFH Leader, explained the geology and identified local fossils to look for to the group. The lower chalk (also known as the grey chalk) at Samphire Hoe is from the Cenomanian stage of the Upper Cretaceous so yields fossils aged 100.5 – 93.9 Mya.
Common finds are brachiopods, bivalves and echinoids. Sponges, shark teeth, worm tubes, gastropods and fish can also be found and, rarely, ammonites. As well as beautifully preserved fossils within the chalk, some echinoids and shells and many sponges form flint casts which can be washed out of the chalk and found in the shingle. Attractive pyrite crystals can also be found in the chalk.
Our first find of the lay was an eroded echinoid inside a flint block. UKAFH leader Chris Tait then found a large section of clam. These giant molluscs are mostly found broken into small pieces so this was a really nice find. As the day progressed a good variety of finds were made including echinoids, shark teeth and brachipods.
Samphire Hoe isn’t the easiest location for fossil hunting as you need to scrutinise the loose chalk boulders on the foreshore carefully for signs of fossils and then extract them very carefully with a chisel to ensure they are not damaged. You can also hammer the boulders to break the chalk up in search of fossils so work, tools and care are needed to have a good chance of finding fossils here. Once extracted, however, preservation is usually excellent, with fine details clearly visible.
Cleaning chalk fossils is easy, requiring little more than dry brushing the remaining chalk matrix with a soft brush (a children’s toothbrush is ideal) to remove any chalk remaining on the fossil surface. As chalk is very soft, you can easily remove larger amounts of remaining chalk with a blunt knife or craft knife until you approach the surface of the fossil and switch to brushing.
Finds were pleasing but not abundant, however everyone enjoyed the hunt and the sunshine day.
Chris, Aidan and Sam, your UKAFH leaders, would like to thank all of our members and attendees for joining us on our weekend fossil extravaganza and we look forward to seeing you all soon!
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