echinoid

UKAFH weekender at Folkestone and Samphire Hoe, Kent 14th and 15th October 2017

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The Folkestone foreshore

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!

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Leader Selfie

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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FOSSIL HUNTING EVENTS

 

 

Fossil Hunt at Seaford 1st October 2017

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On Sunday 1st October, UKAFH ventured along the coastline of Seaford in East Sussex – a small town about 10 miles east of Brighton with towering white cliffs.

After a very fortunate summer meteorologically speaking, we had spent the week with a close eye on the remanence of hurricane Marie which crossed the Atlantic and now threatened our fossil hunt.

Fortune persisted however, as although a bit windy and the sea choppy, we began the day dry and mild.

We began with an in depth talk about the geology by UKAFH leader Daniel Slidel. Exposed in the towering white cliffs of Seaford is the Upper Chalk, a Cretaceous deposit (Santonian-Campanian) about 86-83 million years old. Formed from the tiny platelets of coccolithophores – phytoplankton that was abundant in the deep, warm sea that existed here. This striking sediment helped preserve the creatures dwelling on the sea floor, which included bivalves, sponges, corals, bryozoan and the echinoids (sea urchins) this stretch of coastline is famous for. Within the cliffs are horizontal bands of flints which are visible as far as the horizon allows.

After a short walk from the car park we descended some concrete steps onto the beach. The abundance of fossil echinoids was immediately noted as within the exposed bedrock on the foreshore were the tell-tale circular marks of weathered echinoids in situ. We could not extract these as the bedrock here is protected, however this gave us ambition as we traveled west towards loose boulders from which we could extract specimens. It was not long before beautiful echinoids were being found loose or extracted from boulders. There were two genre found, Echinocorys and Micraster. These were found in chalk boulders preserved with delicately thin calcite test – however the flints on the foreshore should not be overlooked either as more robust and often sea rolled specimens for found here too. Other finds on the day included small bivalves, shapely sponges, coral and bryozoan.

As the afternoon drew late the atmosphere became heavy with the approaching storm and the first rain fell as we ascended the concrete steps back to the car park. Looks like we did it again and avoided the worst of the weather!

Thank you to everyone who attended this fossil hunt. It really was a great and friendly group of people, it was a pleasure to guide you through the Cretaceous geological history of Seaford.

Further Reading.

Hampton, M.J., H.W. Bailey, L.T. Gallagher, R.N. Mortimore and C.J. Wood 2007. The biostratigraphy of Seaford Head, Sussex, southern England; an international reference section for the basal boundaries for the Santonian and Campanian Stages in chalk facies. Cretaceous Research, v. 28, no. 1, p. 46-60.

UKAFH fossil hunt to Beltinge, Herne Bay, Sunday 21st May

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Under a blazing sun a band of 34 of us gathered to enjoy a day at the seaside fossil hunting.  Kitted out in hi-vis but otherwise lightly equipped, this family-friendly fossil hunt was ideal for beginners and old hands alike. Fossils are easy to find at Beltinge and require only a sharp pair of eyes and a little patience to find.

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Ready to fossil hunt at Herne Bay
Beltinge beach yields fossils from the Palaeocene and Eocene epochs of 56 – 54 million years ago which were laid down in a warm marine climate.

The Paleocene rocks of the Thanet Formation are exposed on the foreshore and in the cliffs towards Reculver. The younger Palaeocene and Eocene rocks overlay this and are exposed in the gently dipping strata.  At Beltinge, the Beltinge Fish Bed of the Upnor Formation (Palaeocene) is brought down to beach level. West of the car park, the Oldhaven Beds slope towards beach level, exposing the Oldhaven Fish Bed. The fossils at this location erode slowly from the cliffs and the beds which form the beach. Beltinge is renowned for a diversity of fossil shark teeth as well as marine vertebrate remains such as fish and shark vertebrae, eagle ray and chimaeroid fish dentition and bones and carapace of marine turtles.

On the date of our visit the tide wasn’t particularly low and the sea has been very calm, meaning that a lot of sand was deposited on the beach and the best search areas were covered by either sea or sand.  However fossil hunters should not be deterred as a location like this is so rich in fossils that even a “bad” day will yield finds with a little patience and effort.

We had only been on the beach for a few minutes when first-time UKAFH hunter Jo Applegate found a shark or ray vertebra, an uncommon find.

Continuing along the foreshore, we searched the gravel and shingle on the foreshore for fossils and soon the group was finding shark teeth and other small fossils. Below are finds by Nicky Parslow and Olivia Birch.

As we proceeded we followed the tide out and headed towards Reculver where the “islands” of sand and shingle form, trapping fossils amongst the small pebbles. There are teeth from about 24 species of shark, ray and other fish to be found here, as well as the remains of crocodile and turtle. Poppy Hewitt found a beautifully preserved section of turtle carapace and Sam Caethoven found a nice piece of eagle ray palate, pictured below. Amy Everitt also soon found her first shark tooth!

Fossilised wood is also common at Beltinge although it is very friable and not worth retaining.  Pyrite specimens are a little harder wearing but prone to pyrite disease (rust!). Members were able to find and enjoy numerous specimens.

Continuing onward and outward, as the low tide peaked we reached the Thanet Formation which we were fortunate to find exposed.  Here it was possible to observe many bivalves in situ, although on the whole they are too fragile to remove, being supported by silty sand and mud.  However, some of the bivalves have become pyritised inside so occasional examples of intact shell over solid centres or the beautiful metallicised casts of the bivalves can be safely collected.

Close attention to the areas between the pebbles and the clay on the foreshore began to reveal a greater number of shark teeth.  These were larger and better preserved than those found in the shingle, being more newly eroded from the clay, and were predominantly Striatolamia macrota.  This is the most commonly found shark tooth at this location and is black in colour and distinguished by striated faces. The best example was found by Aidan Philpott.

Aside from the shark vertebra found, the most unusual find of the day was identified after the fact as a partial snake vertebra found by Nicky Parslow. Nicky also found the partial echinoid pictured below, alongside a left mandibular plate from the chimaeroid fish Elasmodus hunteri found by Sam Caethoven.

We have received several emails with thanks and positive feedback from members who attended the event.  We very much enjoyed hosting the hunt and are delighted that members had a great time too! As always, we look forward to meeting you again on future hunts.

Finally, could a sunny day at the seaside be complete without an ice cream?

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Sam Caethoven

Fossil Hunt at Overstrand – April 9th 2017

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On Sunday 9th April, UKAFH met in Norfolk for a fossil hunt along the coastline of Overstrand, a village a few miles south-east of the popular holiday destination of Cromer.

We began with a show and tell presented by UKAFH leaders Sam Caethoven and Aidan Philpott, discussing the local geology and providing an example of what could be found.

Overstrand and the surrounding coastline is somewhat unique in its geology, providing a glimpse into three very distinct periods of time. Firstly, there is the chalk. Maastrichtian in age, this chalk is some of the youngest exposed in the UK at around 70 million years old. The chalk sediment formed in a relatively deep, warm sea which would have been close to the Mediterranean in latitude at the time. Life was abundant in the sea, not least in the profusion of coccolithophores – who’s calcareous plates formed the striking white sediment – but also in echinoids, belemnites, corals and sponges whose fossils we came to find today. Also present at Overstrand is the Wroxham Crag formation and Cromer forest bed. These deposits are a lot younger than the chalk; in fact they formed 600-500 thousand years ago during an interglacial stage when Norfolk was a vast river basin and flood plain frequented by giant mammals such as the famous Runton elephant (steppe mammoth), rhinoceros, bison and deer as well as small mammals, amphibians, fish and a plethora of freshwater bivalves – remains of which can all be found, washed out from these sandy sediments. The third geological feature here is from the last glacial stage, about 100 thousand years ago. The glacial stage has deposited thick areas of till and glacial clays but the most apparent action of the glaciation is how the underlying sediments of cretaceous chalk and interglacial crag have been affected. A process called glacial thrusting has lifted the chalk horizontally, so much so that at times the chalk appears above the younger sediments in the cliff, some strata appear unexpectedly horizontal and glacial lakes and channels cut through the underlying sediments, filled with till and glacial clay. The overwhelming force of glaciation is very apparent at Overstrand.

Fortunately for us, the ice has long receded and we were able to enjoy the warm spring sunshine of the current interglacial stage as we headed down on to the beach.

Fossil hunting conditions here have not been the best of late; several feet of sand have covered the foreshore for some time. Beneath this sand lays the Maastrichtian chalk from which many of our finds are to come from, however the chalk is currently only exposed on the foreshore at low tide as sparsely dispersed pockets. Despite these unfavourable conditions, UKAFH fossil hunters quickly began finding great fossils derived from both the chalk and crag deposits.

Among the shingle built up along the coastal groynes and beyond, UKAFH members found many echinoids preserved in flint – mostly of the genus Echinocorys – as well as belemnites and no end of sponge fragments. I was particularly surprised by the number of mammal bone fragments that were found, washed out from the Wroxham Crag and Cromer forest bed. One find that I found exciting was a small fish vertebra in dark Cromer Forest bed sediment found by Clare Ashworth. As the tide retreated we moved from the shingle towards the pockets of chalk exposed further on the foreshore. Here we could see a vast diversity of fauna preserved in situ: echinoids, brachiopods, corals and Ventriculites sponges with beautifully preserved detail.

Belemnite found by Harry Walsh
Two of many, many echinoids found by Chris Bite

A nice bit of Ventriculites sponge in chalk.
A fish vertebra – possibly from the Cromer Forest Bed! found by Clare Ashworth
First mammal bone of the day found by Mary Bite

More mammal bone! Found by Sam Caethoven

Unfortunately, as the chalk was exposed close to low tide, it wasn’t long before the sea turned and we were pushed back from the exposures, however we headed home very much satiated. Although the beach was in unfavourable condition, the hunt was unexpectedly productive with unexpectedly fine spring weather. With fascinating geology and many superb finds, the group proved that even six feet of sand can’t stop our eagle-eyed intrigue.

A pocket of chalk exposed on foreshore.

Solitary coral in chalk found by Aidan Philpott
More mammal bone! – Found by Harry Walsh

Fossil wood in glacial lake clay.

Thank you to everyone who came and made the day a great success!

– Please remember, the cliffs exposed at Overstrand are protected and should not be dug into. Fossils can easily be collected along the foreshore.