Geology Site Account

Site name: Broomfield Gravel Quarry (former)

Grid reference: TL 723 114

Brief description of site:

Historical site only. Broomfield Quarry formerly had exposures of Kesgrave (Thames) Sands and Gravels overlain by glacial sands and gravels and boulder clay (till). The quarry is notable for the discovery, in 1985, of beds of richly fossiliferous organic clay and silt within the Kesgrave Formation, deposited during a temperate stage of a Middle Pleistocene interglacial.

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Details

Broomfield gravel pit was formerly working the Kesgrave Sands and Gravels (Kesgrave Formation) which were laid down during the early Ice Age by the River Thames when it flowed through north Essex and Suffolk and out across what is now the southern North Sea to become a tributary of the Rhine. Above the Kesgrave Formation is a thickness of boulder clay, or till, which was laid down on top of these gravels about 450,000 years ago by an ice sheet during the Anglian glaciation, the most severe cold period of the whole of the Ice Age (Whiteman 1987). Between the Kesgrave Formation and the till was up to 2 metres of glacial sands and gravels (Barham Sands and Gravels) which was laid down by meltwater in front of the advancing ice sheet.

In 1985 two thin beds of silt and clay were discovered within the cold-climate gravels of the Kesgrave Formation, the lower one containing numerous fossils and thought to have accumulated during an early temperate substage of an early Middle Pleistocene interglacial. Pollen indicated a meander channel on a river floodplain in a mixed deciduous woodland environment. Fossils included many water plants such as water lily which require warmer Summer temperatures than exist in Britain today, although Winters may have been cold. There were also fossils of insects, molluscs and fish remains.

A comprehensive, 36 page paper was published on the discovery in 1996 (Gibbard et al. 1996).

Broomfield Quarry in 1971, looking NE. The upper face is composed of Chalky Boulder Clay which has a sharp contact with the underlying gravel. Photo © British Geological Survey (P211103).