Mile-deep mine-shaft shows Jurassic Whitby was stormy and stinky

Investigation borehole for Woodsmith Mine provides scientists with new insights into ancient climate change

A borehole drilled nearly a mile down into the rocks beneath Whitby, North Yorkshire, has provided scientists with an amazing new record of ancient climate change. It shows that – 182 million years ago – the Jurassic seas of North Yorkshire were stormy, stinky, and very unpleasant for sea-life.

After a year of dead crabs and clams, and sewage in the sea, you might say that not much has changed. Jurassic Whitby was certainly warmer than it is now, though. It was also located further south, in latitudes occupied by the present-day Mediterranean. The evidence for this comes from the chemicals, fossils, and rock structures preserved in the dark grey cliffs around the town, such as at Saltwick and Sandsend, and beneath Whitby Abbey.

Jurassic sandstones and mudstones in the cliffs below Whitby Abbey.

Earth scientists have known for some time that these early Jurassic mud-rocks were formed during a period of global warming, but they have had to build up the story in pieces, from different places along the coast. Now, thanks to cores drilled by the Anglo-American Woodsmith Project at Sneatonthorpe, a team of researchers has produced a new, high-resolution record from a single location, and their findings have been published as an open-access paper in the November issue of the Proceedings of the Yorkshire Geological Society.

“Whitby’s dark, fine-grained rocks are world-famous for their fossils, especially jet, ammonites, and marine reptiles,” explains researcher Dr Liam Herringshaw, Director of the Yorkshire Fossil Festival. “These were preserved during a period of Early Jurassic climate change, known as the Toarcian Oceanic Anoxic Event.”

Jurassic bivalves and ammonite from the Jet Rock of Port Mulgrave, North Yorkshire.

“The Woodsmith borehole provides the first continuous record of this event from a single site in northern England,” says project leader, Dr João Trabucho Alexandre, of Utrecht University in the Netherlands, “and has given us a unique insight into this important interval in Earth history.

“The cores allow us to study environmental change in high detail,” Dr Trabucho Alexandre explains, “and our analysis confirms how stressed the seas of Jurassic Whitby were. However, it also reveals that some of what appear to be abrupt climate shifts were actually gaps in the rock record, caused by hurricane-scale storms scouring away sediment from the sea-floor.”

Waves from a winter storm break against cliffs of Jurassic shale.

“One of the most sobering aspects of this research is how badly affected Jurassic sea-life was by this period of global warming,” adds Dr Herringshaw. “Burrowing creatures, which are normally able to cope quite well with environmental change, disappeared from the muds for thousands of years. Very few other creatures could cope with living on the sea floor either.

“Though these events took place more than 180 million years ago, they provide us with crucial information on how dramatic the impacts of climate change can be on life in shallow seas.”

Early Jurassic burrows cutting across layers of mud and silt, Kettleness, North Yorkshire.

The full study – A new subsurface record of the Pliensbachian–Toarcian, Lower Jurassic, of Yorkshire, by João Trabucho Alexandre, Darren R. Gröcke, Elizabeth Atar, Liam Herringshaw & Ian Jarvis – is published in the November issue of the Proceedings of the Yorkshire Geological Society, and is available to view and download here. Dr Herringshaw’s photographs of the cores, showing some of the fossils found, can be viewed here.

Earth scientist in York, fossilist across Yorkshire. Co-director of the Yorkshire Fossil Festival and palaeontologist for hire. Can be found twittering, facebooking, and instagramming as @fossiliam.

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