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Greenstead Puddingstone, COLCHESTER, Colchester District, TM02162481, Potential Local Geological Site
Site category: Boulders - puddingstone
Site name: Greenstead Puddingstone
Grid reference: TM 0216 2481
Brief description of site:
A very fine, colourful boulder of Hertfordshire puddingstone, one of the best in Essex, sits on a concrete plinth in the communal garden of a block of flats in Avon Way, only a few metres from the pavement. It was formerly on full view but unfortunately it has now been enclosed within the communal garden and a hedge has grown up completely obscuring it from view.
A very fine and colourful boulder of Hertfordshire puddingstone (1.5 x 0.75 metres in size) sits on a concrete plinth in a communal garden adjacent to 160 Avon Way. It was formerly clearly visible from the public thoroughfare between 160 Avon Way and Bennett Court. Unfortunately a hedge has now been planted in front of the boulder and it is now not visible from the footpath. It can, however, be seen by entering the communal garden. At the front of 160 Avon Way is a small sarsen stone on the grass - also on a concrete plinth.
This puddingstone is a puzzle as it is in mint condition and shows no sign of being transported by a river or an ice sheet. It was presumably found when the housing estate was constructed in the 1960s. The fact that it was placed on a plinth clearly means that it was valued at the time and it is therefore very sad that it is no longer visible.
This is not the only important boulder in Greenstead. About 150 metres to the east of the puddingstone a large sarsen stone sits next to a bus stop in Avon Way - see separate site entry (Greenstead Sarsen Stone - TM 0231 2483).
The origin of Hertfordshire puddingstone
Hertfordshire Puddingstone was formed around 55 million years ago when the climate of Britain was hot and a layer of pebbles 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 in Hertfordshire, hence the name, and were probably carried to Essex by the River Thames when it flowed north of its present course. However, the distribution and abundance of Hertfordshire puddingstone in parts of Essex suggests that some occurrences may have a local Essex source.
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.
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