Fossil Collecting: Fun, but not always fruitful.

Within the last couple of weeks I have had a couple of fossil collecting trips which have varied a lot. Both were enjoyable but couldn't be more different. One involved lots of people of a wide range of ages; the other was just myself and a friend. The first involved me searching through shale for fossils on a beach; the other had me looking at a limestone/dolomite cliff risking being nettled.

Runswick Bay - 15/07/2010

The first trip, on the 15th of July, was organised by Doncaster Museum and led by Dean Lomax of Palaeocritti. There were around 40 of us altogether, ranging from young children to the elderly. We went by coach to Runswick Bay, a well known fossil collecting locality north of Whitby, as can be seen on the map below.

It is not a place I had been before, though I knew the rocks would be of Jurassic age. There is also the potential for finding some quite random fossils, brought down to the bay by glacial erratics, but it is often best to stick to the shale in order to know what time period your collected fossil is from. We arrived at the bay in the morning to find that coaches could not get down the hill, forcing us to walk down a steep hill, so of course it rained on us. One thing I did find interesting on the trip down the hill was the paving slabs in the driveway of a house; they contained pseudofossils formed when magnesium oxide gets into cracks in limestone.The picture below shows a view of the bay:

When we were collecting fossils the weather cleared up. Some of the children started finding fossils straight away, their eyes seemed almost unnaturally attuned to spotting fossils. Rocks were repeatedly overturned, shale smashed and everyone went along at their own pace. It was one of those trips where everyone found fossils. It was very easy to come across casts of ammonites and bivalves, devil's toenails (Gryphaea) were common, along with occasional belemnites. One of the best finds was an ammonite mass mortality (Harpoceras I believe) and also a potential crustacean part (I reckon a crab) and some possible fish bones. I was also a little jealous when Dean found a chunk of rock with ripple marks; I do like ripples (and really should get the picture of me at Durdle Door next to some huge, uplifted ripples). Below is a picture of the group fossil hunting, you can see me on the left with my shorts, typical hat and big boots:

My own finds were nothing special (though all fossils are special in their own way) but then I really went just for the enjoyment of it. I have some ammonite casts, lots of bivalves (I always find bivalves) and a couple of belemnites.

South Elmsall - 20/07/2010


My trip to South Elmsall quarry was very different. South Elmsall is to the north of Doncaster towards Wakefield and happens to be just down the road from where a couple of friends of mine live. Whilst researching the geology of the area I found out that there might be fossils in South Elmsall Quarry from a paper I found online. From what I gathered from the paper, there was the possibility of finding more like those I have found in Conisbrough, plus a few others not found here. My friends who live near South Elmsall had asked me to come help them with some stuff, so I mentioned the possibility of me heading to the quarry at some point, to which they responded by saying I could take their youngest son out with me as he has just finished GCSEs and doesn't have a lot to do. So on the Tuesday we set out for about an hour to explore, with this map to guide us:

It was actually very easy to find and thankfully a lot of the cliff was exposed; a previous search on Google Maps made it look like the trip would be futile. The first thing you see when you approach the cliff are some excellent examples of stromatolitic domes. Formed by algae building up sediment, these domes resemble a lettuce in cross section. I did not have a camera with me, so sadly I could not take pictures, but here is an image from the paper:

This image is not particularly good, or at least it does not compare to how I remember them. There is no sense of scale (we are always told to make sure there is something to reference for scale at uni) and the typical graffiti at the bottom could be any size really. The stromatolites are worth looking at, so at some point I will go back and take some proper pictures. I looked around as much of the rocks as possible and found no fossils at all. No Liebea squamosa, no Dielasma elongatum. The paper had me thinking I would find many bivalves (Liebea, Bakevellia, Permophorus and Schizodus) along with bryozoa (Acanthocladia) but I should have been realistic, after all, many of these are meant to be in Conisbrough too but I have not yet found them. I did, however, find some casts which appear to have been Bakevellia binneyi as they were roughly the right size and shape, plus there were more than one of them. There was nothing I could take home with me, only the image of stromatolites and bivalve casts in my head. I intend to return, at least to take pictures, but I may also find something.

These two trips make an interesting contrast. The first had me finding things easily, coming away with a heavier bag even though I had emptied it of my lunch. The second had me coming back empty handed, which I don't mind too much as it is good experience; palaeontologists have to get used to disappointment as many of the best finds seem to be down to luck. In my opinion, going out and failing to find something to take home is more worthwhile than not going at all.

Critter of the......evening. Liebea.

This is Liebea, a Permian bivalve mollusc similar to modern mussels. They were epibyssate suspension feeders, meaning that they anchored themselves to rock or seaweed and filtered food particles out of the water. Liebea  commonly formed clumps containing only that species.

The fossil above is Liebea squamosa  and is one of the bivalves I found in the Ashfield Brick-clay Pit in Conisbrough. Like the brachiopods found there, the Liebea  fossils appear to be quite small (about half the size they should be) but not to the same extent as the brachiopods. This could be interpreted as having a high infant mortality rate (due to overcrowding or a soft substrate) or small adult size due to overcrowding.

More From the Zechstein Basin

It isn't every day that a specific area of interest comes up in a lecture multiple times. I was already paying quite a lot of attention during this particular sedimentology lecture, but managed to pay even more when the Zechstein sea was brought up. I thought I would share the information I got from it.



The first mention simply came with the mention of commercial uses of evaporite deposits, as salt from the Zechstein sea is mined for industrial purposes and human consumption. Boulby mine in East Yorkshire is apparently the deepest in the UK and extends a mile out to sea.

The Zechstein basin is a saline giant, extensive marine evaporite deposits (deposited when sea water evaporates and leaves minerals) thousands of metres thick in what are known as intracratonic basins (a craton is a part of the Earth's crust that has not been split or merged). There are no modern equivalents of saline giants. Below is a picture of major Phanerozoic evaporite deposits.

Saline giants present a conundrum for geologists as evaporating sea water in the laboratory does not produce natural evaporite minerals and produces them in the wrong volumes (not enough anhydrite, too much sylvite/carnallite). Evaporating a 300m column of sea water only produces less than 5m of salt, yet in Jurassic marine deposits in America the desposits are 3500m thick, which would require the evaporation of a 240km deep marine basin!

On the left is the data predicted compared with the actual amounts found in the Zechstein basin. Below is the same data plotted in a graph. As can be seen, the predictions do not match what is produced.

The explanation for this seems to be that these basins were repeatedly replenished with sea water, possibly before the sea had fully dried out. Doncaster during the Permian was in a sea which was constantly evaporating and being refilled. This required special conditions. There needs to have been a barrier to the open ocean permitting replenishment of sea water (which could be continual or episodic); there needs to have been prolonged subsidence; and there needs to have been prolonged aridity and thermo-haline stratification (this relates to the temperature and salt content of the water).

There are different types of saline giant basins. The Zechstein was a deep barred basin, as shown on the left. These have the same mineralogy across the basin at any given time, overlying anoxic muds, with a straitified water column in 10s to 100s of metres cycles.


Hopefully future lectures will reveal more about the Zechstein basin, though I suspect that I will have to apply information from other examples in order to work out more about it.

Exploring the Zechstein Sea

I've lived in Conisbrough, a large village on the outskirts of Doncaster, for most of my life. Even so, I knew very little about the geology of the area until recently. As a child I knew that there were no dinosaurs to be found and that impressive fossils like ammonites were to be found at the coast. I also knew that I was in the heart of the South Yorkshire coal fields (Cadeby Colliery used to be in walking distance and Maltby still has a pit) so I could have guessed that Carboniferous rocks were nearby. Apart from that I also knew that there was a working dolomite quarry nearby, but not what age it was.

This Easter I decided to rectify that. Before returning home I had a look at some of the books in the university library, not really expecting to find much but still hopeful. I looked at the few books they had on the geology of South Yorkshire, mostly getting little information. Eventually I stumbled on a battered looking book from the '60s titled Geological Excursions in the Sheffield Region which contained a chapter titled "Conisborough". The spelling mistake irked me a little, but I read on, only to immediately happen upon them stating that fossils were rare in Conisbrough. Unperturbed I read on. Fortunately the book mentioned just one locality in Conisbrough where fossils could be found and I was determined to find it. The map given was poor and the descriptions of the route were heavily outdated, but still I checked it out of the library in hope.

Below is a better map which I found after finding the place for myself:

I set out looking for it with my friend Johnathan, we had plans to walk somewhere else afterwards but first we would look for fossils as it was on the way. The poorer map had us looking around 150 metres away at some bare rocks which matched none of the descriptions and clearly held no fossils. We had almost given in. As I used to go walking around here I knew of a place at the top of the hill which might just have been it, so we decided it was worth looking. When we got there we were not sure and we looked at a lot of the rocks up close but to no avail.

Up close there was a lot of interesting features on the rocks, but not the fossils we were looking for. We may have found shell casts, but with no actual shells we were not convinced. On the left is some of the interesting layering we found, including a lovely brick red colour at the top. It was around this point that Johnathan seemed to have given in. Continuing to look seemed futile and the place was not easy to get around. We were later to realise that this was the old Ashfield Brick-clay Pit, which is now only used by fly-tippers. This was useful for me in my youth as I travelled there in search of things to build dens out of; now it is a bit of a nuisance. Whilst Johnathan wandered off getting bored, I kept looking, having to do a little climbing in the slippery mud. I did find a couple of interesting features:

Above is a picture taken in what could be described as a small cave if I was being generous. What was interesting about it are the mineral precipitations from the ceiling. I can't help but wonder if any of the kids who burn their fires and drink there have ever stopped to admire this. On the right is an example of a quartz vein in the rocks there. They are surprisingly common when you start looking at the rocks, yet I reckon I am one of a handful of people who have stopped to appreciate them.

At this point I was enjoying looking at the rocks and the surprises they held. When I reached the place in the picture on the left I decided to have a look at some of the higher rocks and found myself climbing a very wobbly tree. I found some interesting clays and more quartz veins whilst I sifted through little rocks I found, hoping to find a fossil. Somehow I did it. I picked up a small rock and realised that I was probably holding an ancient shell. I shouted to Johnathan that I thought I had found something, but I really wasn't sure as I had a niggling feeling that I was seeing what I wanted to see.

It was then that I found another, which I sadly do not have a picture of as I gave it to Johnathan as a souvenir of our little expedition. I felt almost triumphant, I had succeeded. In my hands I held two little pieces of ancient history, long dead bivalve molluscs that have been fortunate to fossilise and survive hundreds of millions of years. I've had this feeling before as these were not my first fossil finds, but this meant more to me. Conisbrough will always feel like home to me and now I have a piece of its ancient history. Our fossil hunting was over for the day, so we continued on our walk with some sense of achievement.

My automatic reaction to this is to do some more research. I classified both of these specimens as belonging to genus Liebea but I may be wrong. It certainly does occur around here, but so does Bakevellia and to be honest I can't tell which is which in some examples. I am certain some of my later finds are Liebea, however, it was those that made me think the first specimen might not be. During my research I found this paper which I wish I had in the first place. It has a more detailed description of the rock exposure, is more up to date, and has a map which would have led me to instantly recognise the place.

A few days later I was playing guitar in church on Easter Sunday when I spotted Andrew, a friend I hadn't seen for a long time. After church we went over to the church hall for a cup of tea and a bit of a catch up. I can't remember how we got onto the subject of fossils, but when I said I had found some in Conisbrough his eyes lit up and his mouth dropped. Fossil hunting had become a hobby for him recently and he was even doing a project on them (he is an artist). I think he felt as I did, the thought of finding fossils in Conisbrough, the place of our youth, was exhilarating. It didn't take long before we were both thinking of heading there straight away, I feel like we read each others' minds. So off we set, myself with a guitar on my back, off to the Ashfield pit in search of ancient life.

When we got to the place I had found fossils Andi was using his keen observational skills. He suggested we looked in the area where the rocks had fallen for fossils which had come away from the rock face. I can't believe I had not done this myself, but then I am used to being told to look right up at a rock in order to identify sedimentary structures. As soon as he had suggested surveying the floor I spotted one, a lovely Liebea specimen. I showed Andi so that he knew what to look for and he went on to find four fossils of his own. I went up to my spot up the tree and came across my first brachiopod find, identified as Dielasma, along with a bivalve mollusc which has me baffled at the moment, as it does not fit with anything listed in the paper. Below are my finds up to that point. On the left is my first specimen. The other three are what I found with Andi. They are Liebea (the one which makes me want to reassess the first), Dielasma, and the unidentified bivalve.

After this I did more research. I already knew that I was looking at Permian rocks, so this put the fossils at around 250,000,000 years old. During the late Permian the Earth looked like this, as seen on the picture to the right. Conisbrough sits in an area which used to be the Zechstein sea, an area which stretches to Poland. The Zechstein sea was shallow and land-locked, containing many reef systems, particularly bryozoan reefs in this area it seems.

Predictably I decided I would go back at least one more time before heading to Portsmouth again. This time I went more prepared as I had a bag for specimens, a notepad and pen, and a camera to take pictures of the location. Partly simply to have documented it, partly in case others would like to explore the ancient history of Conisbrough.

This time I barely had to put in any effort. Spotting the fossils became so easy. I brought home around 20 this time and left a few there, keeping only my first finds and the most interesting ones. 

I'd love to spend ages putting up pictures of all of these, but I won't. On the left is a bit of substrate which I have kept in its original condition as it contains the mould of a Liebea specimen, along with two other shells, one of which is definitely a bivalve, but the other I cannot see enough of. After this are the bivalve specimens, one of which has what appears to be the original colouration. Over on the right are the brachiopods I collected, including the smallest which is a tiny 4mm in length. 

After I had found all of these I went to look at more of the rocks. I found no fossils but the rocks were interesting to look at. I also found a spot where an owl or another bird of prey might rest to eat occasionally, as I found numerous small bones. Judging by the jaw bones it was a rodent. Sadly the batteries in the camera died as I tried to take pictures of it, so I packed up and came home.

When I got home I documented them and eventually put them in a safe place (a biscuit tin). Over summer I will be returning to the place as there are species listed in the papers I have looked at which I have not found. For now I will have to wait though as I return to university in just two days.