Scarborough Strata #3

A selection of Jurassic ammonites from our teaching collection (picture by David Chalmers)

A selection of Jurassic ammonites from our teaching collection (picture by David Chalmers)

Last month we looked at a group of fossils that have become synonymous with the Yorkshire Coast, the dinosaur footprints. Another group of fossils that have helped make the coastline famous are the ammonites. Indeed if you asked many people to draw or describe a fossil many would choose the spiral shape of these now extinct marine creatures. Whilst ammonites died out at the same time as the dinosaurs, 65 million years ago, palaeontologists are able to be very confident about what they might have looked like, not least as we have a close relative alive today in the form of the nautilus, which can be seen at Scarborough Sealife Centre.

As ammonites were marine creatures their fossils can be found in any rocks deposited at the bottom of oceans, in out part of the world that includes the limestones around Scarborough and the black shales found at Whitby. Whitby has a very close link with the ammonites, with the legend of St Hilda petrifying the snakes that plagued the Abbey forming the coiled snakestones found in the cliffs and on the foreshore. It is still possible to buy Whitby ammonites with a carved snakes head, and St Hilda has an ammonite named after her, Hildoceras. To this day these fossils feature in the Whitby town crest. The fabulous Whitby Museum has an almost unrivaled collection of ammonites from our coastline.

The fact that ammonites were so common during their heyday during the reign of the dinosaurs, called the Mesozoic, and the fact that each species only lasted a short period of geological time, perhaps one million years or so, means that they have been used to correlate rocks all around the world. This science of stratigraphy was developed by William Smith who went on to become known as the Father of English Geology and designed the Rotunda Museum.

Smith carried out his work the length and breadth of England and would have seen ammonites like those pictured from all across England. They are still one of the commonest fossils found on our coastline (even if only in fragments), and our guided fossil hunting walks are a great way  too try and  find your very own Jurassic snakestone.

First produced in Issue 20 of The Scarborough Review

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