Sunday, 2 June 2013

Shimmering Diamonds in an Ancient Sea


 
Field trip reports are not as plentiful on this blog as they once were. There are a few reasons for this – obviously the closure of Quarry 4 was a big blow and a few of the other quarries we were permitted to visit have now closed or have stopped allowing access. This is an unfortunate consequence of the continuing uncertain economic conditions and a health and safety culture gone mad. I have alluded to this many times before but it is still worth highlighting as our geological and palaeontological treasure chest closes ever tighter.
So when the opportunity arose for a field trip to a classic locality became available, I took the opportunity with both hands, as did three of my colleagues from our research group. The trip was a joint venture organised by the Natural History Museum (London) and the Geologists’ Association and was certain to be well attended but it was definitely a trip that you wanted to be on – especially as the site was now earmarked for a housing development. This was very likely to be the last ever permitted site visit.
Keymer Tileworks Quarry is located in the heart of the Weald at Burgess Hill in West Sussex. The tile works has existed in one form or another since the late 1500’s but the current site was migrated to from Ditchling Common when the clay reserves there became exhausted. This was certainly a long drawn out affair since it took 80 years to move the production facilities from 1860 to 1940!
The quarry itself is Late Hauterivian in age and appears to almost straddle the boundary between the Lower and Upper Weald Clay Formations and is thus slightly older than the Bluff (Barremian) – around 130 million years old. Today’s working quarry is not the original workings on the site as measured by Cook and Ross (1996) but there is obviously still a recognisable lithostratigraphic sequence.
Intriguingly, the sedimentary sequence in the quarry is very similar to the Bluff and typical of the Weald in as much it that it represents terrestrial through fluvial to lacustrine conditions (Batten & Austen, 2011) and, as a result contains a very similar fossil assemblage. These include a strictly non-marine fauna of both plants and animals and include sharks, bony fish, crocodiles, turtles, dinosaurs as well as insects, crustaceans and molluscs. Plants include ferns, conifers and horsetails.
As we pulled into the car park there was already a large group of workers there getting their equipment ready.  I recognised quite a few people from the Bluff, a few from the NHM and other groups as well and, as I had already forecast, others continued to arrive. However, it was not that large a group that it was unmanageable and after a briefing regarding the usual health and safety rules, as well as a brief introduction to the quarry, we were soon on our way in.
The tile works was significantly different from the brick works at the Bluff. Before being mothballed the Bluff was a 24/7 fully automated works but here the tiles are all handmade and a lot of the old fashioned out buildings and wooden crates holding the tiles seemed to reflect this traditional method of manufacture. I found it rather refreshing in today’s modern and efficient manufacturing industry that there are still places like this around and it is also tinged with a degree of sadness that the tile works here at Keymer’s has been selected for extinction.
Anyhow I digress. We skirted around the tile works and then slowly descended into the quarry area. As I looked to the right I could see the remnants of the original workings, now either overgrown or flooded with one particular area now almost completely consisting of a glutinous quicksand - a modern day predator trap if ever I saw one. Slowly we approached the raised ramparts of a small quarry and as I looked down there was a very small excavation that was flooded in the bottom – a pump was in situ to keep the water under control. This could not possibly be the quarry – or could it?
Indeed it was. At first I thought it was just a small offshoot from the main quarry but it wasn’t – this was it. I cannot stress how small this site was when compared to the big open sky quarries I was used to. It was like a duck pond with raised sides and I thought that after about an hour tops I would be winging my way home cursing the fact that I had travelled over 80 miles for very little. But first impressions were, to say the least, deceiving.

After the initial shock regarding the size of the quarry the next thing that struck me was the astonishing beauty of the exposed clays, silts and sandstones which were a beautiful mixture of reds, blues, greens, greys and even purple. This was further exaggerated by the succession dipping to the south west and it is another regrettable fact that this section of the quarry has still not been measured properly– nor is it likely to be.
 
We made our way into the quarry and I arrived with others on the south east face to start prospecting. Prospecting is perhaps the wrong descriptive word to use in this case for as we looked at the light grey/green clay layer that lay directly below a reddish-brown layer we could see fish scales and bones weathering out – loads of material. It was apparent that there had been nobody collecting here for quite a while and the continual erosion throughout this extraordinarily hard Winter had done its job.
Several of us immediately lay down and got to work. It was great fun as careful examination of the clay in combination with a gentle raking of the clay produced many scales of various fish which included lepidotids and Lissodus. Vertebrae, despite not being as common as scales, were still plentiful and ranged in size from about 8mm in length to those that could barely be made out with the naked eye. Odd fish teeth and bone made up the other most collected fossils.
The abundance was astounding and you could not fail to find material and the closer you got to the clay the more you would find. The scales were absolutely beautiful and collecting them was strangely compelling and I got the feeling that everybody felt like a kid in a sweetshop as you picked them up one after another – they were like shimmering diamonds in an ancient sea.
Whilst this was going on, the team from the NHM were busily digging into the same microvertebrate bed to remove bulk samples for sieving. They were attempting to remove as much material as possible since this was meant to be the last ever visit to this quarry and, as the bags slowly built up, I actually thought they might struggle to drive it all away. My colleagues Mark and Simon were also part of the team that was continuously beavering away and filling up the sacks with matrix.   
As the day wore on the microvertebrate bed was stripped bare of its fossils and the group began to slowly spread out leaving the NHM crew to their toil. Not only was this active quarry being prospected but others had started to spread out across the site. Those particularly interested in fossil insect remains started to inspect the randomly spread siltstones that had been excavated over the years while others started to scour the older excavations which were only available in small sections due to either being overgrown or flooded.
We decided to stick to the current quarry and continue the search but due to the size of the quarry it was already difficult to find an untouched spot. But this is part of the fun and one of the spots that I had earmarked earlier was a small mound of clay from the same fish bed that had actually been used as a spot where many people dumped their bags, ruck sacks and equipment. As they dispersed the mound became available for prospecting and we soon moved onto the spot.
This turned out to be an inspired choice and we recovered many more scales from the mound and I was also pleased to find a disassociated fish spine and there appeared to be quite a bit of it. I carefully removed the larger parts before recovering the smaller parts of the spine which were obviously quite delicate. Careful excavation of the clay with a dental pick revealed no more parts of the spine and, satisfied there was no more to be recovered, we decided to move on.
On the south west side of the quarry was a well-known reddy-brown clay with a history of exposing vertebrate material. Unfortunately, this had seen better days and was covered in some form of crust that rendered any excavation unlikely in the time available. But there had been the odd rock fall and the spoil had been well searched by others prior to our arrival. Immediately parallel to this however was another exposure of the microvertebrate bed of which some had been piled up as a big spoil heap that probably ran for about fifty yards. This too had been receiving attention and there was lots more material recovered.
However, many people were so engrossed in the spoil that they neglected to look under their feet but we did not and began to recover yet more scales. But only five yards from where we had recovered the fish spine we started to find much bigger scales from a lepidotid fish and they appeared to be in a much tighter area – most people had simply walked over them.
They appeared to be weathering out from a large mound of clay situated just before the previously mentioned spoil heap began. A careful search of the mound revealed yet more scales but no bone was forthcoming. The scales were large and uniform and it seemed likely that there was more to be found of this fish in this proximity but try as we may we could find no more.
Having exhausted this area we decided to spread out and try more places but there was not too much more forthcoming and people began to drift away and the site got quieter. Except, that is, for the NHM crew who were still at it. We had to hand it to them – they had really put a lot of effort in today and would deserve their forthcoming finds. Our colleagues were suffering though as Mark was starting to suffer some back issues and Simon was starting to run on empty.
Some of the NHM crew hard at it.
 
Eventually the day was drawing to a close but even then it was still possible to find the odd scale glistening in the sun and you could not resist them. I don’t think I’ve had so much fun collecting fossils for ages. Other notable finds reported include some insect and plant remains form the siltstones including one nice cockroach with legs attached, an odd reptilian vertebrae, a small limb bone and, I imagine, the find of the day was an unfortunately water abraded theropod tooth which Steve Sweetman believes to be velociraptorine.
But it was the fish remains that ensured that everyone had an enjoyable day and even the weather was about spot on as well. As we slowly drifted away from the quarry, we looked back and the NHM crew had actually finished excavating and were in the process of transporting the bags of matrix to the vehicles ready for shipping out. We later found out that they had managed to ship eighty one sacks all told – an excellent effort. I hope they are rewarded with a few excellent finds – especially mammal teeth which I know they are quite eager to find.
It was with a tinge of sadness that we left Keymer’s in the realisation that our first visit was likely to be our last but at least there had been lots of material recovered and it was great to see familiar faces. It’s just such a shame that another classic quarry is earmarked for closure – our palaeontological heritage is shrinking fast.

Footnote
Those of you who have followed this blog for some time will know that I tend to use pseudonyms for most localities to protect them from illegal collecting but, in this case, since this is meant to be the last visit before the site is developed, it seemed right to give the quarry its correct title.
It was interesting that, when examined under the microscope, a few of the scales turned out to be actually teeth and there are a few sections of minute jaws with teeth in as well – which is interesting indeed. The fish spine is missing substantial parts and there was only two parts that fit together but this also looks good under the microscope. And we have also heard that, if all goes well, there may yet be another “final” trip to the quarry and, if there is, you can count me in for a return visit.
Here are some of the fossils recovered:
 
 

 

Tiny jaw section
 

Part of the fish spine 
 

Teeth
 
 
References
Batten, D.J. & Austen, P.A. 2011. The Wealden of south-east England. 15 - 51. in Batten, D.J. (ed). English Wealden Fossils. Palaeontological Association, London, Field Guides to Fossils, 14, ix + 769 pp.
Cook, E. & Ross, A.J. 1996. The stratigraphy, sedimentology and palaeontology of the Lower Weald Clay (Hauterivian) at Keymer Tileworks, West Sussex, southern England. Proceedings of the Geologists' Association, 107, 231 - 239.

3 comments:

Romain said...

Hello,

Congratulations for your very interesting site.

I'm french, I search fossils and I have a website on fossil vertebrates of my area fossilesdes2charentes.over-blog.com

With friends we go in England in September to search fossils on the south coast and visit the British Museum. I was wondering if it would be possible to indicate sites on the Oxford Clay? Are there any quarries accessible?
Thanking you for your response.
Romain

Mark Wildman said...

Hi Romain - apologies for not getting back to you sooner. Most Oxford Clay exposures these days are limited to the coast. There are exposures at Osmington Mills and Weymouth on the south coast and Cayton Bay and Gristhorpe in the North East.

Other places where the clay is exposed includes Grafham Water (a reservoir where the clay is exposed as the water recedes) and Yaxley near Peterborough where one of the old flooded brick pits is accessible and fossils can be found weathering out of the waterside banks.

There is only one working quarry left in the UK that excavates the Oxford Clay and access is more or less impossible and heavily regulated.

Romain said...

thank for the info
I'll let you know if we go in this area

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