Geology Site Account

Site name: Tesco Distribution Centre Quarry, West Thurrock

Grid reference: TQ 570781

Brief description of site:

Disused chalk quarry now occupied by Tesco distribution centre. The upper part of the chalk face is a fine exposure of coombe rock.

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Summary of geological interest

Tescos distribution centre occupies the southern part of Greenlands Quarry (see separate site record for Purfleet Chalk Pits SSSI) and is accessed from Dolphin Quarry via Dolphin Way through a tunnel under the A1090 (Stonehouse Lane). Fine chalk cliffs encircle the building but the cliff on the north side is of particular interest as the top third is coombe rock.

Coombe rock is evidence of the severe climate that existed in Essex towards the end of the last glacial stage, between 10,000 and 20,000 years ago, when the ground was permanently frozen (permafrost) with only the top metre or so thawing during each brief summer and freezing again the next autumn. Here, the Chalk was close to the surface and the constant freezing and thawing turned the top layer into a mass of saturated chalk rubble, which was capable of slowly flowing down a slope like thick porridge to accumulate in valley bottoms. Now hardened into what is known as coombe rock it can be seen at the top of the cliffs here.

The best view of this cliff is obtained from the pavement on the west side of A1090 (Stonehouse Lane).

The top section of the chalk cliff to the north of Tescos distribution centre consists of coombe rock, proof of an arctic climate in Thurrock, about 20,000 years ago. Photo © G.Lucy