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Dioryctria sylvestrella
find out more... Dioryctria sylvestrella Copyright: Ben Sale

Essex Field Club
Essex Field Club
registered charity
no 1113963
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EFC Centre at Wat Tyler Country ParkWe are open today

We are normally open to the public at our centre at Wat Tyler Country Park every Saturday, Sunday and bank holiday 11am-4pm. We are also open on Wednesdays 10am-4pm.
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Geology of Essex

The rocks beneath the Essex landscape are a record of the county's prehistory. They provide evidence for ancient volcanoes, deserts, glaciers and deep seas. Some rocks also contain remarkable fossils, from subtropical sharks and crocodiles to Ice Age hippos and mammoths. The geology of Essex is a story that stretches back over 100 million years.

Chelmsford Boulder Clay Copyright: unknown The bedrock or ‘solid’ geology of Essex is relatively straightforward with layers of rock gently folded into a trough-shaped fold, or syncline, called the London Basin.  This geological structure can be clearly seen in a block diagram.  Several deep boreholes have been sunk in Essex in search of coal and water and the geological succession has been revealed across the whole county.  Two of the most famous boreholes were at Canvey Island and Harwich.  A table of geological formations in Essex reveals that the rocks of Essex are comparatively young in geological terms.

The bedrock geology of Essex is covered by a veneer of superficial or ‘drift’ deposits, such as sand and gravel, that were laid down during the Ice Age.  Therefore the geology of Essex can be mapped in two ways: either as a ‘solid and drift map’ showing all the rocks exposed at the surface, or as a ‘solid map’ with the superficial deposits removed.

An overview of our county’s geology can be found in the document An Introduction to the Geology and Fossils of Essex which was originally produced for the Essex RIGS Group, the body set up in 1999 to identify Regionally Important Geological Sites (RIGS) in Essex.


Boulder clay, or till, exposed in a road cutting near
Chelmsford - evidence that a huge ice sheet passed
this way about half a million years ago.


Essex Rock Copyright: unknownFor a popular account of the geology of Essex see the award-winning book Essex Rock by Gerald Lucy, published by the Essex Rock and Mineral Society in 1999.  Although unfortunately out of print, it is available for loan through any Essex library.  A review of Essex Rock was published in the Essex Field Club Newsletter No. 30 (1999).


Shark tooth Copyright: unknown
Other pages of the Essex Field Club’s website relate to geology.  See also Essex Geodiversity (left menu), Geological Sites in Essex and Essex Field Club Geology Group

A fossil shark tooth from
the London Clay at Althorne,
near Burnham-on-Crouch.