echinoid

UKAFH fossil hunt to Cross hands quarry, Warwickshire on 21st October 2018

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We were blessed with a warm sunny day on the 21st October to Cross Hands Quarry which is located on private land owned by Mr Newman. Mr Newman had kindly created a couple of fresh spoil heaps especially for our trip, so our party had fresh pickings as will be seen below lots of fossils were found.  As the trip is now centred around these spoil heaps, this location is perfect for families to visit. Therefore we had quite a few families on our trip. 

The quarry was once used to supply building stone for the local town of Chipping Norton, which is located in the Cotswolds famous for its rich honey coloured stone buildings.

Cross Hands Quarry is a Site of Special Scientific Interest (SSSI) for its geological features. The rocks exposed in the quarry faces are mostly limestones, formed from the remains of shelly creatures living in the warm tropical seas which covered large areas of England in the Middle Jurassic Period, about 175 million years ago.

GEOLOGY

Cross Hands Quarry exposes rocks of Middle Jurassic age that were deposited in a shallow marine environment, not too dissimilar to that of the modern-day Bahamas. These rocks belong to the Inferior Oolite and comprise the Clypeus Grit, overlain by the Chipping Norton Limestone and the Hook Norton Limestone.

Towards the end of Upper Lias times sea levels fell somewhat, bringing a change of conditions which initiated the Middle Jurassic. Low sea levels persisted for 15 million years and in clear, warm, shallow waters the most important sediment was calcium carbonate. The accumulations of carbonate mud and carbonate sand have been transformed into a variety of limestones which are grouped into two series called the Inferior Oolite and the Great Oolite.

The word Oolite refers to a rock containing a proportion of polite. These are little spheres of calcium carbonate, typically half to one millimetre in diameter. The name comes from the Greek word on – meaning egg – because a densely oolitic limestone has the appearance of fish eggs.

The Inferior Oolite group of formations is so called not because of any inferior quality but because it’s rocks are older than, and therefore stratigraphically below, those of the Great Oolite. This limestone makes excellent building material as has been used in the Cotswolds to give the buildings there distinctive golden yellow colour.

SSI Noticeboard showing Geology and typical fossils that can be found at location.

During the Inferior Oolite and Great Oolite times this area was low-lying between shallow sea to the south-west and a swampy, coastal region to the north-east. In these shallow, variable environments the deposition of sediment varied greatly in amount and type from place to place and time to time. As a result the strata exhibit rapid lateral changes in thickness and character and some beds may be restricted to small areas.

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Geology Map of Whiltshire

In the early 1960’s remains of a partial right femur from a Cruxicheiros(meaning “cross hand”) is a genus of tetanuran theropod dinosaurwhich lived in the Middle Jurassic of England. The type species is C. newmanorum,described by Roger Benson and Jonathan Radley in 2010.  The 2010 paper recognized differences between the Cross Hands Quarry discovery and those attributed to Megalosaurus. These differences include lower and broader spines along the animal’s back, and differences in leg and hip bones. The authors renamed the Cross Hands Quarry specimens Cruxicheiros newmanorum; the generic name Cruxicheiros comes from a mixture of Latin and Greek, Latin crux meaning “cross” and Greek cheir meaning “hand,” in reference to the Cross Hands Quarry locality where the fossils were discovered. The specific name newmanorum honors the Newman family, who own the quarry. Cruxicheiroswas a large theropod, but the known material is very limited. The holotype, catalogued as WARMS G15770, is a partial right femur. Additional material from the site probably comes from the same individual as the holotype, based on examination of the matrix of sandy limestone and calcite which make up all the fossils. The additional material consists of “an anterior dorsal or posterior cervical vertebra; a dorsal neural arch; a partial dorsal vertebra; the anterior half of a middle-distal caudal vertebra; a partial right scapulocoracoid; a partial left ilium; the proximal end of a left pubis; [and] numerous rib and bone fragments”. The specimens are now stored at Warwickshire Museum Service (Source Wikipedia).

FINDS

Typical fossils found at this location are bivalves, brachiopods, gastropods, echinoids (such as Clypeus ploti).

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Nice big articulated bivalve – Pholadomya fidiculá
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Coral
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Lovely piece of Coral showing polyps
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Echinoid probably a Clypeus Ploti
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Echinoid – possibly a Nucleolites sp
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Gastropod- Bactroptyxis bacillus
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Gastropod – Purpuroidea morrisea

Many thanks to Mr Newman for allowing our party to visit his quarry.

UKAFH fossil hunt to Ketton quarry, Rutland on 13th October 2018

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UKAFH were fortunate to gain access to this remarkable mile-wide working quarry on Saturday 13th October. A small group of us gathered on this unseasonably mild but breezy day for an excursion into the Middle Jurassic. We assembled in the site canteen for a briefing from UKAFH leader Sam Caethoven and the site management, taking time to enjoy the displays of some of the more exceptional finds to have been previously found at the quarry, before heading into the quarry itself.

Ketton Quarry is an enormous site which provides an extensive exposure of the middle Jurassic from rocks of Bathonian age (dating to around 165 million years ago) to Bajocian age (around 175 million years old). The mile-wide quarry has been worked for many decades and is now 115.6 hectares in size. With full access, this huge quarry provides opportunities to collect fossils from many different beds, however we were limited to an area of spoil where operations were not currently ongoing for safety and practical reasons. Despite this, fossils were still abundant.

The geology at Ketton is complex, with a range of Jurassic-aged rocks recorded. Mostly, three formations are visible in the quarries: the lowest is the oolitic Lincolnshire Limestone which was laid down in the middle Jurassic about 160 million years ago. This large, blocky, rock was formed from small grains of calcium carbonate which were deposited under a warm, shallow sub-tropical sea which was subject to reasonably strong currents. Above this is the Rutland Formation – bands of delta and shoreline muds and sands carried by rivers. Each band, with shelly remains at its base and tree roots at the top, was formed when sea-level rise topped the layer below. Many colours can be seen in fresh exposures of this formation. The exposures at the working quarry (Ketton Main Quarry) are the type formation for the Rutland Formation. Above the Rutland Formation is the Blisworth Limestone, laid down under quiet, shallow, warm conditions during a marine transgression. The Blisworth limestone is full of fossil corals and shells.

Ammonites can be found but bivalves, corals, brachiopods, gastropods, echinoids (such as Clypeus ploti), shark teeth and fish remains are more common. In the past, dinosaur footprints have been seen, along with fragments of their bones, but we were not that fortunate on this occasion.

Blocks of limestone are often full of bivalves, brachiopods, or corals but you need a good geological hammer and a chisel to extract them as they can be very solid, although some rocks will have weathered to the point that fossils can be easily picked out. There were also many loose fossils to collect.  Throughout our time on site we were able to find many bivalves and echinoids as well as a few brachiopods and gastropods.  Special mention goes to James who took the time to carefully search the fine matrial for quasi-microfossils and found numerous echinoid spines, fish teeth and an Acrodus sp. shark tooth.

At the end of our hunt we gathered in the canteen for refreshments and to enjoy seeing each thers’ finds.  It’s quite unusual on a UKAFH hunt for us all to finish together and have somewhere to gather for show-and-tell afterwards and it is always a highly enjoyable part of the day.  As well as seeing all the finds and learning more about the site, the quarry staff can also see what we have found, both to share in our enjoyment and to ensure that anything rare is reported and recorded.

UKAFH would like to thank Hanson Cement and the staff at Ketton quarry for allowing us to visit and taking care of us throughout the day, including briefing us, showing us the site and allowing us the use of their facilities.

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UKAFH fossil hunt at Withington, Gloucestershire on Sunday 30th September 2018

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We were blessed with a warm, dry day for our first hunt at Withington in ploughed farm fields. The proximity of the topsoil to the Inferior Oolite below in this locality means that ploughing brings rock to the surface which contains a large variety of fossils. A field hunt really is an excellent way to find fossils with little effort other than to look patiently and “get your eye in”. The weather conditions were dry and overcast, making it an ideal day to fossil hunt as the rock was relatively clean and easy to spot so plenty of finds were made.

 

Once assembled at the farm, which we obtained special permission to visit, our guest leader and local expert for the day, Mark Baggott, gave us an introduction to the local geology and fossils. After enjoying Mark’s display and introduction to the site the group spread out to hunt across the two newly cleared fields and finds were quickly being made.  The lower field produced a good variety of abundant brachiopods, bivalves and regular echinoids and the upper field yielded complete and partial Clypeus ploti.  A number of members also found ammonites, which was unexpected as ammonite finds at this location have historically been quite uncommon.  Some beautiful gastropods were found and one lucky hunter even found a flint scraper!

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Mark Baggott’s fantastic display of Withington finds and geology and ID sheets

The Cotswold Escarpment rocks are almost exclusively marine and were deposited mainly in warm tropical seas. Plate tectonics has transported this part of the Earth’s crust northward over the last 150-200 million years to its current location. The Middle Jurassic rocks here are the characteristic ‘Cotswold Limestone’; soft, yellow, sandy limestone at the base of the Inferior Oolite (literally egg stone), a sedimentary rock formed from ooids, spherical grains composed of concentric layers. Towards the top of the Inferior Oolite the limestone becomes more fossiliferous and is referred to as ‘grits’ due to its coarser texture. Such an Inferior Oolite exposure is exposed at the farm and the fossils that this limestone contains date from between 167 to 175 million years ago at a time when this farm was at the bottom of a warm tropical sea. The rocks exposed near the farm comprise the Salperton and Aston Limestone and, from a fossil perspective, the most interesting layers are the Grits (Clypeus, Upper Trigonia Grit and Lower Trigonia Grit).

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Clypeus ploti found by Sam Caethoven

The commonest fossil found at this location is the sea urchin (echinoid) Clypeus ploti. These are more commonly known as Chedworth Buns (after the nearby village where they were often found) or Pound Stones, because their weight was usually a good approximation to 1lb. Clypeus lived in burrows on the seafloor, and burrowed their way through the sediment to get nutrients. They had fine hair-like spines and are an example of what is known as an “irregular” echinoid because they are shaped, not rounded.  Because these irregular echinoids lived in the sediment, they didn’t need the spiky and sometimes poisonous spines that the spiny sea urchins (known as regular echinoids) that we can see on the seafloor today have for protection. As well as the Clypeus Ploti we find other echinoid species which are “regular” and would have had sharp spines.  Unfortunately the spines rarely fossilize still attached, but they can frequently be found individually in the same sediment.

Trigonia bivalves gave their name to the second grit since they are very common at this horizon.  Trigonia are a family of saltwater clams, noticeable because the exterior of the shell is highly ornamented. Other fossils to be found comprise of brachiopods, bivalves and gastropods. Brachiopods are a marine animal that had hard valves (shells) on the upper and lower surfaces.  They are distinguished from bivalves which also have two valves/shells but in a left/right arrangement rather than upper and lower.

Brachiopods are bottom dwelling marine animals and, although rare today, in Jurassic times they dominated the sea floor and were frequently found in large colonies. One characteristic unique to brachiopods is the pedicle, which is a long, thin fleshy appendage which is used to burrow into the sea floor as an anchor while the brachiopod could feed clear of the silt.  Although the fleshy pedicle itself does not preserve in the fossils, the opening at the top of the animal from whence the pedicle connected (known as the foramen) is clearly visible. Brachiopods are filter feeders, gathering microscopic organisms and bits of organic matter from the water that flows by them using a specialized organ called a lophophore. This is a tube like structure with cilia (hair like projections). The cilia move food particles down the lophophore to the mouth.

Brachiopods are often known as lamp shells as the curved shell of the some classes look rather like Roman pottery lamps. There are two main groups of articulate brachiopods from the Jurassic, terebratulids and rhynchonellids. A common example of a telebratulid brachiopod found here is Stiphrothyris tumida; their main characteristics are their ovoid/circular shape, presence of a clear hinge line and a circular pedicle opening located in the beak. This brachiopod is a type example for lower Trigonia grit. The second of the main orders of articulate brachiopods is the rhynchonellids. The main characteristics are their strongly ribbed wedge shape, the absence of a clear hinge line, the line between the valves/shells is often zigzagged and a circular pedicle opening located in the beak. An example of such a brachiopod found here is Burmirhynchia sp.  The rhynchonellids were able to extrude their lophophore out of the shell in water, whereas the terebratulids maintained their lophophore within the shell.  The ability to extrude the lophophore led to more efficient food-gathering and is probably why rhynchonellids survived the mass extinction events better than the terebratulids.

Bivalves include such animals as clams, oysters, cockles, mussels, and scallops are also found at Withington. The majority are filter feeders and often they bury themselves in sediment where they can be safe from predators. Others lie on the sea floor or attach themselves to rocks or other hard surfaces, a few such as scallops are able to propel themselves through the water. The shell consists of two usually similar valves, and is joined at the hinge line by a flexible ligament with interlocking teeth on each valve. This arrangement allows the shell to be opened and closed for feeding without the two halves becoming disarticulated. Bivalves found here include Thracia (a member of the clam family) and Pleuromya (a member of the mussel family).

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Large ammonite found by Sarah Scott

If we compare brachiopods and bivalves, although they resemble bivalves, brachiopods are not even molluscs.  They are so unique that they have been placed in their own phylum, Brachiopoda. Brachiopods are shelled marine organisms that superficially resembled bivalves in that they are of similar size and have a hinged shell in two parts. However, brachiopods evolved from a very different ancestral line, and the resemblance to bivalves only arose because of a similar lifestyle. The differences between the two groups are due to their separate ancestral origins. Different initial structures have been adapted to solve the same problems, a case of convergent evolution. In modern times, brachiopods are not as common as bivalves. Brachiopod shells are often made of calcium phosphate as well as calcium carbonate, whereas bivalve shells are composed entirely of calcium carbonate.

Also to be found at Withington are gastropods. They are called univalves because they build a single coiled shell to protect their soft bodies. Ancient fossilized gastropods are related to living gastropods of today and are snails. Gastropods can be carnivorous or herbivorous. Their tongue is covered with thousands of tiny teeth to tear apart food.

UKAFH would like to sincerely thank the landowner for allowing us access to the fields.  Special thanks also to Mark Baggott for organising the visit and providing a fantastic display of local fossils and information for us all to refer to throughout the day.  Thank you also to Mark and to Alan Banyard for bringing along some very nice examples of undamaged and prepared Clypeus ploti and ammonites from nearby locations for members to take home.

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!

Click here for our UKAFH news and to see out upcoming events (we update the list regularly so check back often!)

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.