Wednesday, 12 August 2009

Quarry 4


Quarry 4 (name changed) is another of those amazing Oxford clay quarries that continues to yield abundant and varied fossils. Situated along the A1 corridor, the quarry is still being worked for its high quality brick making clay.

Because it is still being worked, the pit changes shape rapidly and good finds are virtually guaranteed. The clay is Jurassic in age, Callovian, about 160 million years old.

The most common fossils are the ammonites, but these are nearly always paper thin and not very collectable, although some of the clay matrix is very beautiful and the ammonites can be preserved in situ to make a really nice piece for study. Occasional three dimensional ammonites can be found but these are exceptionally rare.

The next most common fossils are the belemnites and Gryphaea, the Devil’s Toenails. The belemnites are often large and well preserved. Most are broken but some full length fossils survive intact and these make impressive pieces. Occasionally, they are recovered on slabs of clay with the outline of the soft parts preserved, including the tentacles and these are highly sought after.

Not so common but of great interest are the occasional remains of trees and plants. These are often land plants that have been washed out to sea, sank and were covered by sediment to become fossilised. A lot of these are poorly preserved but every now and then, a really nice example survives and I was very fortunate to recover a superb piece of bark on my last visit here.

But this quarry and others like them are rightly renowned for the remains of the fish and marine reptiles that swam in the open sea. Many fine specimens of ichthyosaurs, plesiosaurs and pliosaurs have been found over the years, and it was these fossils that I was determined to seek out.

When you first visit a highly productive quarry such as Quarry 4, you cannot help but collect loads of fossils and pretty soon you have a bag full of belemnites and the like. Nothing wrong with that, but the hard part comes when you start to look between these fossils for bone or teeth and then it becomes a lot more difficult.

But I was determined to try on this latest trip.

Lessons Learnt

Unfortunately we arrived about 15 minutes later than our associates and by the time we dropped into the quarry and reached the search areas, the freshly turned over sections were already being scoured for their fossils. I noticed, however, that the “hot” section from the last trip was devoid of people, so we opted to start there – a mistake I was later to realise.

Despite our closest attentions along this whole section we turned up very little. Without sounding blas̩, there were, of course, plenty of belemnites and shells but try as we may, no vertebrate fossils were forthcoming. The sun was beating down on us as well Рwe were sweating for very little return.

After a while we decided to head for the freshly turned clay as some of the others had moved on but even there we struggled. As we started to head back to the meeting area for lunch, news reached us that an ichthyosaur had been located on the upper level of the quarry and was being assessed for possible excavation.

We went back to the car for lunch and were able to see the morning spoils. Some nice pieces of bone had been recovered but the highlights were two teeth found by the same guy. The first was a nicely preserved plesiosaur tooth, jet black and slightly curved but the second was an exceptional pliosaur tooth, about 2 inches long, on matrix with exceptional enamel preservation and colour. To say I was a little envious is an understatement!

Shortly afterward, two of the more experienced collectors returned with the ichthyosaur bones that were exposed on the surface. They removed the bone because of the possibility that the pieces may be illegally collected – a sad factor in today’s world.

The site was marked out and photographed and permission will be obtained from the quarry owners for a proper excavation. Confidence is high that the rest of the skeleton is probably there. Hopefully I will be able to let you know the outcome in a separate post.



Moon Pit

After the excitement of the ichthyosaur and lunch duly finished, we were delighted to find out that we were going to another quarry for the afternoon. This was only about a mile away and a somewhat famous quarry in the area.

The quarry, which we will call Moon Pit, is no longer being worked for its clay but is rightly famous for its marine reptile fossils and, more recently, aroused nationwide interest when the giant fish Leedsichthys problematicus was excavated there and television cameras were there to capture it on film.

Arriving at the quarry, one was struck by how much of it was already overgrown and surprised at the sight that there was a solitary excavator positioned there digging into the fresh clay. On one side of the quarry, there was a clay “peak” that had been heavily excavated on both sides leaving a strange hoodoo- like structure that was quite eerie.

We all went our separate ways to search for fossils. Initially, we went to the area where the excavator was in the hope of finding freshly uncovered specimens, but the clay was strangely barren. We slowly circumnavigated the quarry until we reached the area with the most spoil heaps and searched there.

In the centre of this area was a long man-made trench and it would appear to be the place where Leedsichthys had been removed. Searching in the vicinity revealed very little, a few belemnites and not much else and I suspected that today was going to be one of those days.

As the afternoon wore on it was obvious that everyone was struggling so we slowly headed back to the cars (these, incidentally, were parked in the bottom of the pit – not every day you park your car on an ancient sea floor!). On arriving at the cars, we found to our surprise that the guy, who had found those teeth back at Quarry 4, had also found a partial plesiosaur paddle bone and some other fossil bone. Well, when your luck’s in.....

The day had drawn to a close, an unsuccessful day from a personal point of view but highly rewarding none the less. We had seen some nice fossils recovered and had been on site when at least a partial ichthyosaur had been discovered.

We headed home, a little more wiser than earlier in the day and determined to return next year for a more successful trip.

Footnote

Shortly after I finished this article, the ichthyosaur site was revisited but unfortunately the hope of a complete skeleton soon disappeared. Instead, it appeared that a conglomeration of not only ichthyosaur, but also plesiosaur bone had come together and was scattered about on the surface over a fairly wide area. However, all the bones have now been recovered and taken to a repository, and we hope for better luck next time.

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