Geology Site Account

Site name: Priors Pit, Furneaux Lane, Fingringhoe.

Grid reference: TM 0300 1986

Brief description of site:

On the west edge of Priors Pit is a preserved cliff of glacial sand and gravel. A public footpath runs along the top of the cliff but permission to access the cliff face must be obtained from the landowner.

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Summary of the geological interest:

On the west edge of Priors Pit is a preserved cliff of glacial sand and gravel. Priors Pit is a former sand and gravel pit which ceased working in about 2015. The pit has not been infilled and the cliff retained for the benefit of sand martins.

The cliff consists mostly of sand with occasional seams of flint gravel. This is thought to be the Upper St. Osyth Gravel which was also worked at the nearby gravel pit which is now Fingringhoe Wick Nature Reserve. This sand and gravel was deposited some 450,000 years ago by colossal torrents of meltwater issuing from the Anglian ice sheet, the edge of which was then situated only 12 kilometres west of here. At that time ice covered almost all of Britain. This cliff therefore provides evidence of an exceptionally cold period of the Ice Age.

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Scientific interest and site importance

The Fingringhoe area is underlain by Lower St. Osyth Gravel and Upper St. Osyth Gravel (Bridgland 1994). The Lower St. Osyth Gravel was laid down by the River Thames when it flowed through central Essex, to the south of Colchester, and out across the low-lying land that is now the North Sea to become a tributary of the Rhine. Shortly afterwards the Anglian Ice Sheet blocked the valley of the Thames upstream and diverted the river to its present course. As the ice sheet spread into central Essex the former Thames valley became a channel for glacial meltwater which flowed across the Fingringhoe area laying down the Upper St. Osyth Gravel, a typical glacial outwash deposit. The junction between the two gravels therefore represents the point at which the Thames ceased to flow through central Essex. The Thames at that time was a very large, braided river and its diversion must have been a catastrophic event.

The sand and gravel exposed in this cliff is thought to be Upper St. Osyth Gravel. However, there is a distinct junction half way up the cliff which may be the junction between the Upper St. Osyth Gravel and the Lower St. Osyth Gravel. If this is so, the junction will represent the diversion of the Thames.