Geology Site Account

Site name: Priors Green Sarsen Stone

Grid reference: TL 5752 2128

Brief description of site:

A sarsen stone about 100x80x35 centimetres in size can be seen on the grass at the entrance to the new Priors Green housing development. It was found close by in 2007 by archaeologists while carrying out a survey in advance of housing construction.

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Summary of geological interest

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 beneath the surface of the ground became cemented with quartz. They are thus very resistant to erosion and have survived the rigours of the Ice Age. They originated on the chalk downland north and west of Essex and were carried here by rivers and glaciers. After retreat of the ice they became concentrated in river valleys.

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 Priors Green Sarsen Stone. Photo: G. Lucy