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EFC Centre at Wat Tyler Country ParkWe are closed due to the Covid-19 situation, but we are otherwise normally open to the public at our centre at Wat Tyler Country Park every Saturday, Sunday and bank holiday 11am-4pm, check. We are also normally open on Wednesdays 10am-4pm.

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Chadwell St Mary Sarsen Stone, , Thurrock District, TQ64637850, General geological site

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Site name: Chadwell St Mary Sarsen Stone

Grid reference: TQ 6463 7850

Brief description of site:

In the churchyard of Chadwell St. Mary church is a sarsen stone (1 metre x 0.5 metres x 0.35 metres in size) with mammillated surfaces.

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Sarsen stones

Sarsens are extremely hard boulders of sandstone formed around 55 million years ago when the climate of Britain was hot and a layer of sand on the surface of the Chalk became cemented with quartz. They are thus very resistant to erosion and have survived the rigours of the Ice Age.

The formation of silcretes (which includes sarsens and puddingstones) has been the subject of recent scientific debate. Research has compared the conditions under which sarsens and puddingstones may have been formed with the present day climate in the Kalahari Desert and parts of Australia.

The sarsen stones of Thurrock are some of the best-preserved examples in the UK and most have curious rounded protuberances on their surfaces (‘mammilated’), which are growth structures formed as the quartz slowly crystallised between the sand grains.



Chadwell St Mary Sarsen Stone. Photo: G. Lucy

 

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