gastropod

UKAFH field trip 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 field trip 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 field trip to 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.

Field trip to Barton on Sea, May 13th 2018

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On Sunday 13th May UKAFH met at Barton on Sea in Hampshire, a coastal village a few miles east of Bournemouth.

Before heading onto the beach, Chris Tait provided examples of likely finds and explained the area’s geology and paleoenvironment. The cliffs and slippages here comprise the Barton Beds, a series of clay and sandy clay that was deposited about 36 million years ago during the Eocene epoch in what was a warm shallow sea. The sea would have been further south during the Eocene epoch, similar in latitude to modern day Spain and so the climate considerably warmer. We were very fortunate to be provided an example of warm weather as the day was bathed in sunshine and temperatures pleasantly mild. The warm, shallow Eocene sea was a rich ecosystem and the clay provided a great medium to preserve the remains of creatures that lived there which means the area is incredibly fossiliferous. The area is noted for having over 600 named species of bivalve and gastropod and is also particularly abundant in shark teeth and fish remains.

We ventured down from the carpark to the beach which, in such fine weather, is very popular with tourists. We began by investigating the base of the clay slippages. Although ill advised to dig into the slippages, on the surface of the clay are many fossils already washed out.  These include a whole variety of shells, especially bivalves which can be particularly ornate. Everyone found a variety of different species of gastropod. The shells here can be quite fragile, so it is important to bring a box, preferably with some padding to protect the specimens.

Later in the afternoon, many of us stopped for lunch which was an ideal opportunity to sit on the shingle and rootle through the flint pebbles in search of shark teeth. Once we got our eye in, many great examples of shark teeth were found, predominantly of the Striatolamia genus and Sam Caethoven found the dental palate of a fish, one which would have had shell crushing teeth, ideal for feeding on the abundant gastropods an bivalves here.

Later in the day, Chris Tait led a small group up onto the slippages to get a better look at the geology. It is extremely important that care is taken when on the slippages and it is not advised this is attempted without a guide as it can be easy to become stuck in mud. Evidence of this danger was provided by a number of abandoned wellington boots!

Thank you to everyone who attended and a big thank you to Chris Tait and Sam Caethoven for leading the hunt. I hope you all had a great time!

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Left to Right: UKAFH leaders Sam Caethoven, Aidan Philpott, Chris Tait and Nicky Parslow.

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