What’s on : Lectures

Exceptional carrots of Yorkshire

16 Jul 2019
Start time
7:30 PM
Tempest Anderson Hall
Dr Liam Herringshaw, Geology, University of Hull

Event Information

Exceptional carrots of Yorkshire
Dr Liam Herringshaw,Geology, University of Hull

Large areas of North Yorkshire are underlain by clays and shales of Jurassic age, from the gemmiferous Jet Rock of Whitby, to the Kimmeridge Clay Formation, source rock for much of the North Sea oil. Away from the Yorkshire Coast, these rocks are rarely well-exposed, so a proper understanding of their properties, and how they formed, is strongly dependent on boreholes.

Liam’s talk will unveil the exciting world of core-hunting, explaining how a laboratory trip to Nottingham led to a carrot shed on the outskirts of Chartres, via some wooden crates in a Scarborough bus depot. It will also try to explain how the muddy materials stored in such glamorous locations have offered up exceptional insights into extinction events and global climate change during the most famous of geological periods.

This lecture will be preceded by the presentation of the John and Anne Phillips prize

Member’s report

Much of North Yorkshire is underlain by clays and shales of Jurassic age, including the Kimmeridge Clay Formation, source rock for much of the North Sea oil. Analyses of such strata is obtained from core samples – called ‘carottes’ in French.

Core samples had established that Late Jurassic strata of Kimmeridge Clay in Dorset had a smell of oil and combusted spontaneously, with up to 50% Total Organic Carbon (TOC). Comparable UK core samples from a BGS borehole in the Vale of Pickering had been lost, but detective work discovered a duplicate set in a shed outside Chartres. Analysis showed that the Dorset and Yorkshire core samples, taken 400km apart, were remarkably similar in TOC profile. However, over certain time periods there were critical differences, corresponding to absence of trace fossils that indicated anoxia and extinction. From this it is deduced that there was a southward shift in the jet stream for about one million years, which brought stormy monsoon conditions to Dorset but not Yorkshire.

Rod Leonard