Geology Site Account

Site name: Wivenhoe Gravel Pit SSSI

Grid reference: TM 050235

Summary of geological interest

Site of Special Scientific Interest designated for the importance of its geology. Wivenhoe Gravel Pit is the type locality for the Wivenhoe Gravel, which was laid down by the Thames when it flowed across this area before being diverted to its present course by ice during the Anglian glaciation.

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Site description

Wivenhoe Gravel Pit is the type locality for the Wivenhoe Gravel, part of the Kesgrave Sands and Gravels which was laid down by the Thames when it flowed across this area before being diverted to its present course by ice during the Anglian glaciation. The Wivenhoe Gravel was laid down during two cold stages of the Ice Age and interbedded within the gravel is an organic silty clay containing fossils from a warm or temperate climate. These include plants, pollen from temperate-climate trees, and beetle remains. This clay represents an intervening interglacial stage but unfortunately the fossils it contains are not yet sufficiently distinctive to identify which interglacial stage. However, judging from the position of the Wivenhoe Gravel in the old Thames terrace sequence it is likely to be the temperate interval that immediately preceded the Anglian glaciation (this glaciation brought about the diversion of the Thames about 450,000 years ago). Much work is therefore required before this interval, recognised in recent years elsewhere in Britain but undefined, can be fully evaluated. Its status as a full interglacial has also yet to be established and it may be just an interstadial (a short-lived temperate-climate event in a predominately cold period). It is possible that the sediments date from the latter part of the Cromerian interglacial, as defined by the Cromer Forest-bed in Norfolk.

The position of these temperate sediments in the Thames gravels is therefore highly significant, making Wivenhoe Gravel Pit an important source of evidence for reconstructing the evolution of the Thames.

Of additional interest at Wivenhoe Gravel Pit was the discovery of two flint flakes in the interglacial sediments that may have been worked by humans. If they represent a period of human occupation at Wivenhoe it will be the earliest evidence of humans anywhere in Essex and over 500,000 years old. They would be about the same age as the human tools and remains discovered at Boxgrove in Sussex, which are thought to represent occupation by Homo heidelbergensis, a species of human that is probably a direct ancestor of the Neanderthals.