Part 1 of a 5 part series: please check back in coming weeks for part 2!

Banner image: Marine crocodile, The Fossils of the Oxford Clay by The Palaeontological Association (1)

Let's journey to the Millennium Country Park's very own marine Jurassic Park...!

By Duncan Willox ǀ Local geology enthusiast and poet

As the park is a long way from the sea I’d better explain...

All the lakes around Stewartby and Marston Moretaine are old pits - now flooded - created by the brick making industry that covered the  Marston Vale in the 20th century. The clay they quarried, known as Oxford Clay, was formed by particles raining down on to the seafloor of a warm shallow sea about 160 million years ago. Because of its chemical makeup it happens to be particularly suited to firing clay for bricks. It is also a famous source of beautifully preserved fossils.

To travel back in time from the Country Park, I’ll need to supply you with wet suits and oxygen tanks to survive in that Oxford Clay sea! Let your imagination run free, and come and explore what was under the waves…

As we head just below the surface, you can see an ichthyosaur swimming nearby - it looks a little like a dolphin, but with a larger “snout”. In fact - like all the large carnivores we’ll see - it is a reptile, not a mammal. Hugely successful from the early Jurassic until the Cretaceous period the ichthyosaurs became extinct some millions of years before the other marine reptiles down here did so, along with the dinosaurs with the cataclysmic events at the end of the Cretaceous period, about 65 million years ago. Those events changed the world forever, ushering in the modern day reign of the mammals, with the mighty reptiles being mainly relegated to a supporting role of snakes and rock-scurrying lizards.

image: Plesiosaur, The Fossils of the Oxford Clay by The Palaeontological Association (2)

You might also see a plesiosaur: another carnivore, this time with a long neck & tail and nasty looking teeth. The elusive Loch Ness Monster is claimed by some to be one of these beauties! There are also marine crocodiles that live in this area, and pliosaurs - the top predator of this sea. This species has the wonderful name liopleurodon ferox and, with a skull up to 2 metres or possibly longer, it is one of the largest carnivorous reptiles that’s ever existed, on land or in the sea. Bearing in mind those fearsome rows of sharply pointed teeth, we’ll have to be careful as we explore the deeper depths…

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(1) (2) Kelly, S. (1992). D. M. Martill & J. D. Hudson 1991. Fossils of the Oxford Clay. Palaeontological Association Field Guide to Fossils, number 4. 286 pp. London: The Palaeontological Association. Price £15 (paperback). ISBN 0 901702 46 3. Geological Magazine, 129(3), 374-375. doi:10.1017/S001675680001935X