ammonite
UKAFH field trip to Folkestone Sunday 6th October 2019
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!
Chris Tait
UKAFH field trip to Withington, near Cheltenham, Saturday 5th October 2019
UKAFH hosted its largest field trip ever on Saturday 5th October when we welcomed 50 members, many of them new joiners, to privately owned ploughed farm fields near Withington which we had obtained permission from the landlord to visit. 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 (with landlord permission) really is an excellent way to find fossils with little effort other than to look patiently and “get your eye in”. It is comparatively easy to find rocks on the surface of the topsoil and inspect them for fossils, many of which are already loose from the rock. No tools or equipment are required other than a container for your finds and, at this location, a bucket was ideal as fossils were plentiful and they are easy to carry and drop the robust fossils into as you go along.
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.
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), named from the index fossils found in those rocks.
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.
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.
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).
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 and to Andy Crawte and Alan Banyard who gave their time to assist our attendees in identifying their finds.
All in all we had a great day out and it was wonderful to welcome so many enthusiastic new members and see so many families enjoying what was for many of them their first fossil hunt. Everyone went away with finds and I saw many happy smiles! This is exactly what UKAFH is all about and I really hope we see many of you on future fossil hunts. Our 2020 hunt calendar has now been published so please take a look and I hope to see you all soon!
UKAFH field trip to Doniford Bay, Somerset on 15th September 2019
On 15th September 21 UKAFH members set out to explore the geology and fossils of Doniford Bay in Somerset. Our group assembled at Doniford Farm Park with their kind permission, since the nearby public car park was closed at the start of the year. This allowed us to park and gather easily as well as providing a wonderful opportunity to purchase delicious lunches and a variety of local produce and wares as well as meeting the farm animals!
In the glorious sunshine of a late September heatwave, we walked as a group to the nearby beach access and descended to the bay. Sam set off to check the terrain and rock exposures on the beach and Aidan, the group leader for today’s event, provided some information to the group on the geology of the area and what the group might expect to find. Directing our gaze to the distant cliffs in the direction of Watchet, Aidan explained that the red layers which were clearly visible displayed a history of interchanging desert and aquatic conditions, with water encroaching on the landmass then retreating to give way to desert conditions. These varying states, occurring as Pangaea broke up and the Triassic period came to an end, finally gave way to full inundation by the ocean as the Jurassic period commenced. The change in condition brought marine life to the area which leaves its record in the rocks beneath and around us in this location.
The rocks at Doniford Bay represent the very earliest part of the Jurassic period beginning 201 million years ago. The most abundantly evident fossil is the ammonite Psiloceras planorbis, which is a zone fossil, which means it is recognised as being the defining biological marker for the start of the Hettangian stage 201.3 ± 0.2 million years ago, the earliest stage of the Jurassic period. All ammonites with the exception of the genus Psiloceras went extinct at the end of the Triassic so all Jurassic and Cretaceous ammonites are descendants of this genus.
Aidan continued to explain that the other ammonites we were likely to see demonstrate the evolution of this ammonite as it adapted and evolved to different niches of the newly opened up marine environment following the mass extincions of the end Triassic. Firstly we will notice Caloceras johnstoni, which, like Psiloceras planorbis is always crushed flat but maintains aragonite (mother-of-pearl) shell preservation which often demonstrates spectacular rainbow iridescence but which evolved a ribbed shell which would have afforded advantages, possibly affecting buoyancy and swim control or resistance to predation or other damage. This was succeeded by larger and more ribbed species like Arnioceras and Coroniceras which we hoped to see in situ in the wave-cut shale platforms.
The post-extinction sea quickly refilled with new life and Aidan informed the group that alongside the abundant ammonites we could also hope to find fishes, marine reptiles such as ichthyosaurs and plesiosaurs and plant remains.
We headed off as a group towards an area of loose rocks on the foreshore where we knew ammonites could be commonly found. Aidan pointed out some examples that were clearly visible and demonstrates how best to split the fragile shales, reminding group members to be safe using goggles and ensuring others were not close and vulnerable to flying chippings. He added that the delicate ammonites benefitted from preservation to bring out their colours and prevent deterioration and shared a tip that a smear of lemon juice was often effective in helping bring out the colour. Finally Aidan reminded members that they should only collect a few examples as no-one needs many identical specimens and there should be plenty left for others.
The group dispersed over the pebbly area and were quickly finding examples of Psiloceras and some Caloceras ammonites as well as some fragments of 3D ammonite. Chris Tait found a beautifully preserved example of Brachyphyllum, a cone- bearing plant which is known from the late Carboniferous to the Cretaceous.
After the group searched the loose foreshore pebbles Aidan took the group to the ledges of shale along the beach where we could observe the later, larger ammonites like Arnioceras and Coroniceras. The site is SSSI so hammering if in-situ rocks is mot permitted and these specimens cannot be extracted but we were all able to view, photograph and enjoy the many beautiful examples visible on the rock surfaces.
We were fortunate to observe, on close inspection, a small fossilised fish exposed in the rocks and one lucky group member found a small ichthyosaur vertebra. Also visible were crinoid ossicles and sea urchin spines.
As we returned to the slipway to leave the beach accompanied by the sound of the steam train whistles there was still a surprise yet to come – a beautiful, unusually preferved brachiopod found by Jonah.
UKAFH would like to thank Doniford Farm Park for allowing us to park for the duration of our excursion. Your pasties and pies make delicious lunches and we wish we could have stayed for the delicious looking carvery!
We hope everyone had an enjoyable day at Doniford and we hope to see you all again on future field trips.
Hock Cliff – 30 June 2019
On Sunday the 30th July, UKAFH embarked on a fossiling foray in Gloucestershire, on the River Severn near a small village called Frampton on Severn – a location known as Hock Cliff.
We met at a private car park for which we were very grateful to have received permission to use. (Please note that if visiting Hock Cliff individually parking would need to be sourced elsewhere along the road heading north west from Frampton on Severn). From here, group leader Lizzy Hingley guided us on a short walk through fields before arriving on the riverbank where a cliff, at most 20m tall, is exposed for a stretch of just over 1000m.
The cliff and foreshore exposed at Hock Cliff are made up of the lower portions of the Blue Lias formation, an early Jurassic formation about 200 million years old. As well as Gloucestershire, The Blue Lias formation is exposed along the Somerset Coast, in Dorset near Lyme Regis, South Wales and even parts of Yorkshire, so the material here was not unfamiliar to many of the seasoned hunters on this trip. The Blue Lias consist of repeating bands of a blueish limestone and darker shale (The name Blue Lias is derived from the blue colour of the limestone, the colour itself is derived from the high concentration of pyrite in the stone). These sediments were formed in a warm, placid, shallow sea which would have been much closer to the equator than present day. The surprisingly formulaic nature of the repetitive limestone and shale bands can be interpreted as resulting from a Milankovich Cycle. This is a cycle in which the earth wobbles on its longitudinal axis – a result of gravitational influence from other celestial masses – which result in earth’s polar regions becoming closer, then further from the sun and so effecting global climate and sea level; and consequently the sedimentation of this Jurassic sea as finer sediments travel further from their source, effecting the type of sediment produced. Amazingly we can calculate the length of this cycle and so can interpret each section of limestone and shale to represent about 90,000 years of time, which unlike more homogeneous strata allows us to visualise the passage of time throughout the formation.
This location is incredibly fossiliferous with well-preserved examples from much of the familiar early Jurassic marine forna abundant here. Most notably the bivalve Gryphaea (Often called Devil’s Toenails) can be found in quantity but are remarkably well preserved, often with both valves intact and with pronounced growth rings, allowing you to calculate its age when it died. Ammonites are also common, often small and preserved in pyrite, hints of gigantic ammonites can be spotted in the limestone ledges. There is also a crinoidal bed where, if exposed, mudstone packed full of crinoid beautifully preserved in calcite can be found. Hock cliff also has its share of vertebrates including fish, Hybodus sharks and marine reptiles such as ichthyosaurs and plesiosaurs. Further down the River Severn the pterosaur Dimorphodon was found in the Blue Lias above Aust cliff so the chance of terrestrial fauna is not unimaginable.
After a short introduction to the geology and paleaontology of the area, fossils were being found by the group almost immediately. Matilda Brewer was first in with a fantastic Promicroceras ammonite preserved in pyrite and Barry Taylor found an exceptional example of crinoid bed which was not very abundant on this trip. I think everyone found a great example of Gryphaea, some with the tube casts of creatures who made their home on the shell preserved. Rob Howe struck lucky when he found a small, fairly worn but significantly uncommon ichthyosaur vertebra. However, the star of the show was by far the exceptionally rare and beautifully preserved Hybodus shark tooth found by Tegan Watts.
We were not just lucky with our fossil finds but also lucky with the fine weather, which had cooled slightly from the 30C+ the previous day. Importantly the ground was solid – if visiting this site in winter months or after heavy rain it is important to take extra care as the solid ground becomes dangerous mud.
Hock Cliff is a Site of Special Scientific Interest (SSSI) and so the cliffs and foreshore must not be hammered or dug into. However, there are plenty of loose fossils to be collected along the foreshore.
A big thank you to everyone who attended our hunt at Hock Cliff, it was a great day with a great group of fossil hunters! See you all again soon.
UKAFH field trip to Withington, Gloucestershire on Sunday 30th September 2018
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!
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).
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).
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 visit to King’s Dyke Nature Reserve, Sunday 19th August
On 19th August UKAFH visited King’s Dyke Nature Reserve at Whittlesey near Peterborough. This highly productive, family-friendly location is always a popular hunt and places quickly filled up so we had a full house of 35 with leaders Aidan Philpott and Sam Caethoven.
The geology of the location consists the Peterborough Member of the Oxford Clay Formation, representing the middle Jurassic period of circa 180 million years ago. The clay is quarried for brick making but a spoil heap is provided in a designated area for fossil hunting and it was to this area we were destined today.
We were fortunate to enjoy warm but overcast weather, making hunting comfortable and dry. We kitted up we headed down to the dedicated fossil-hunting area where Aidan gave the group an introduction to the fossils that can be found. The commonest finds are ammonites (especially Kosmoceras), belemnites (especially Hibolithes) and gryphaea, an oyster often called “Devil’s toenail” because of their curled, scaly appearance. However marine reptiles have also been commonly found in the quarry as well as teeth and bones from fish including the ray-finned Leedsichthys, probably the largest fish ever to have lived. An abundance of bivalves and brachiopods can also be found.
The location has an enormous quantity of fossils available and they are very easy to find, making it equally perfect for beginners who want to take home a treasure or two and for old hands who want to find something special, be it a bone, fish remains or a particularly large, complete or well-preserved specimen. The clay is easy to dig into and split so it is never a question of finding fossils; rather of narrowing down the large volume of finds into “keepers”. Soon we had good finds turning up, including calcite Kosmoceras ammonites, plenty of belemnite sections and an abundance of gryphaea.
Although on this occasion no-one was fortunate enough to find any reptile bone, a Hybodus sp. shark tooth was found by Silas Shaul – the first I’ve personally encountered from this site. Well done Silas! Some sharp-eyed hunters like Billy Currie found small fish scales, bones and vertebrae and Tracey Herod found a beautifully preserved calcite-filled gastropod with its aragonite shell still in place.
As events drew to a close we received many kind remarks from attendees who commented on how they had enjoyed their day and were pleased with their finds. We always love to hear your comments and see pictures of your finds, whether from one of our hunts or your own forays so please do share your news on our website and facebook pages! Also please do sign up to our mailing list or keep an eye out on our website for forthcoming 2019 hunts which will be published soon.
Sam Caethoven
Field trip to Lyme Regis February 3rd 2018
It was grey, cold and with weather forecasts that Captain Scott would have shuddered at the thought of! Undeterred, our group met in the Charmouth Road car park and descended to the beach, via the new sea wall next to Church Cliffs, with unsurpassed views of Lyme Bay and to Seatown and Golden Cap in the east. After a welcome to the delights of the Jurassic Coast location and an introductory talk, which took in the geology, Mary Anning, coprolites, public toilets, cliff falls, David Attenborough’s ‘Sea Dragon’, an introductions to UKAFH staff and our ‘guest helper’, Brandon Lennon, we all headed east.
The geology here at Lyme Regis is quite complex. The cliffs and foreshore between Lyme Regis and Charmouth represent three stages within the Early Jurassic (or Lias) period termed the Hettangian, Sinemurian and Pliensbachian, dating from approximately 199-189 million years ago.
Essentially the rocks at Church Cliffs are Jurassic-aged from the Sinemurian stage. The Hettangian stage rocks of the older Blue Lias slowly dips away eastwards beneath sea level and the Shales-with-Beef layer, capped by the Black Ven Marls (part of the Black Ven Mudstone Member) and in turn, part of thr Charmouth Mudstone Formation descend to the beach under Black Ven. The younger Pliensbachian rocks are best studied at Charmouth. During this time a shallow epicontinental sea (less than 100m deep), was present across much of Europe, including most of England, Wales and Ireland, and laid down alternating layers of clay and limestone. At that time, Lyme Regis (as it’s now known), lay closer to the equator, roughly at the latitude North Africa is today.
Armed with all the background, our intrepid explorers heading off. The best place to look for fossils is among the pebbles and rock pools on the foreshore, loose fossils including ammonites, belemnites and reptile bones can all be found with a little patience. Fossils can also be found protruding through the surface of the slumping clays along the top of the beach. At high tide the waves wash away the soft clay, leaving the more resistant fossils exposed and able to be collected by hand.
Our hunt took place on an exceptionally low tide and Lyme’s famous ledges soon began to appear. This is usually a great place to look, as fossils are washed out of Black Ven’s clays and are deposited in the rocks and boulders and in fissures on the ledges. But finds were remarkably thin on the ground and despite some of our party finding a few very small ammonites, along with fragments from larger specimens, not much else turned up. Andrew Baylis found an ichthyosaur vertebra, which is a common find at Lyme Regis. However, the rain, sleet and snow forecast did not materialise! How wrong can the forecasters get it?
As the tide extended further out into the bay, boulders with large ammonite impressions appeared, not dissimilar to those found on the ‘Ammonite Pavement’ on Monmouth Beach.
Finding fossils is never guaranteed and participants of this hunt were not disappointed with the few specimens that were found. The coastal scenery was dramatic and the forecast inclement weather held off! Many thanks o all who attended, many of whom went on to the Charmouth Heritage Centre, to see the newly displayed ichthyosaur skeleton, discovered recently at Lyme Regis and made famous by David Attenborough’s ‘Sea Dragon’ BBC documentary.
UKAFH weekender at Folkestone and Samphire Hoe, Kent 14th and 15th October 2017
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.
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- Anahoplites ammonite found by Joanna Applegate
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- Anahoplites ammonite found by Eddy Miles
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.
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- Sieving for fossils
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- Large shark tooth find
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!
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- Joanne’s selection of finds
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- Jahaan’s ammonite
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.
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- Shark vertebra found by Joanna
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- Isabelle’s sand tiger shark tooth
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.
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- Sindia’s Euhoplites nitidus
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- Anahoplites planus
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!
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- Swordfish tooth found by Brian Allen
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- Fish tooth found by Sam Caethoven
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.
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- White cliffs of Dover
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- Looking towards Samphire Hoe
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.
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- Echinoid in flint block
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- Huge clam found by Chris Tait
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.
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- Beautiful Echinocorys echinoid
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- Remains of sponge in chalk
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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UKAFH visit Seatown, 10th September 2017
On September the 10th, (which was a very blustery day) UKAFH set off on a hunt towards Golden Cap from Seatown.
In the right scouring conditions when the ledges are uncovered from the shingle, Seatown beach can be incredibly productive with the Belemnite Marls exposed – bringing out countless iron pyrite ammonites, crinoid stems and belemnites. Unfortunately, despite the gale that was blowing, the ledges remained covered.
We worked along the landslips on route to Golden Cap. The slips can produce green nodules (named because of the green calcite that makes up the preservation of the ammonites within). which contain many different ammonites, occasionally bivalves and very occasionally marine reptile remains. Within these nodule beds it is also possible to find parts of ammonites which have not been preserved within a nodule have been partially preserved. Many partially crushed Androgynoceras ammonites were found by members of the group, along with plenty of belemnites.
Once the group reached Golden Cap, we explored a little around the exposed Belemnite Marls and the landslips on the Seatown side (any further round, the wind became far too strong!). More belemnites and Androgynoceras ammonites were found. Despite the weather some great fossils were found!
Thanks to all who came along to Seatown and we hope you enjoyed the experience of
Photos from UKAFH’s fossil hunt at King’s Dyke Nature Reserve, Sunday 13th August
UKAFH King’s Dyke Nature Reserve Fossil Hunt on 2nd July 2017
The 2nd July was a momentous day in UKAFH history being the last hunt that founder Craig Chapman would lead before stepping down from leadership duties and we were very hopeful it would be a good hunt. We weren’t disappointed!
I had only been to King’s Dyke once before on a blisteringly hot day and got quite pink in the sun! So I was relieved that there was some cloud cover and we didn’t have to worry about people getting sunburnt.
The hunt was very well attended with about 30 or so people eager to pick through the clay in search of ancient treasure. I must thank the quarry owners for having refilled the area the day before giving us 2 large areas of fresh clay to pick through. After a brief introduction at the identification board we headed up to the smaller heap just up the hill and the hunt was on!
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- Large ammonites
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- Typical King’s Dyke ammonites
One of the best features of this locality is that is suitable for all the family and is productive enough that hunters are guaranteed to go home with something, and everyone who wanted one of the plentiful (and beautiful) flat ammonites found at least one. Belemnites are also very common and range in size from a few centimetres to several inches (sorry about mixing metric and imperial!) The largest complete ones are not to be found everywhere and are quite the prize and I was lucky enough to find a couple of beauties. James found the biggest most complete one and was justifiably delighted with it!
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- James and an enormous belemnite
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- Unusually well preserved ammonite
After about an hour or so at the secondary heap we headed down into the main larger fossil hunting area where we were hoping to find some of the other things that can be found from this section of the Jurassic. Fish, crocodiles, ichthyosaurs and plesiosaurs are all known from here but are not common and are a major highlight if you are lucky enough to spot them. Between us we found 5 Lepidotes fish scales and even a couple of fish coprolites.
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- Lepidotes scale
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- Fish coprolite
I am deliberately leaving the best till last, and chronologically they were found last, all within the last 30 minutes of our time hunting. It wouldn’t have been a proper UKAFH hunt in the Jurassic without Craig finding a vertebra and he duly obliged with a lovely ichthyosaur vertebra. I chipped in with 20 minutes to go with my most spectacular UK find – a plesiosaur vert which truly made my day. Then just as we were packing up, a random family who weren’t even part of our group arrived and the young man hunting with his Mum and sisters found a “weird belemnite” that we were not at all jealous to identify as a plesiosaur tooth! They were on their first ever fossil hunt so I shamelessly plugged UKAFH as a great group to join!! Maybe we’ll see them again on a hunt another time, who knows.
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- Chris’s plesiosaur vertebra
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- Plesiosaur tooth
Either way it was a great day and the feedback was very positive. Thanks again to the quarry owners for the fresh clay to hunt through and I look forward to hunting there again next month with a new group.
Chris Tait
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- Craig’s ichthyosaur vertebra (of course!)
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- Craig – we love you! THANK YOU FOR GIVING US UKAFH xx
