Monument record BLG 054 - Great Blakenham Quarry SSI

The Great Blakenham site exposes a sequence through Early and Middle Pleistocene sediments and soils. These include residual Crag, a thick body of estuarine sands, a thin layer of Thames river gravels, a buried soil complex, an extensive glacial till and associated outwash gravels. The present top-soil developed on the till includes periglacial soil structures and lenses of wind-blown sand. All these deposits make the site of great importance in interpreting the glacial history of southern Britain in Middle Pleistocene times. The Thames river deposits are part of a terrace sequence which represents the former course of the Thames through East Anglia. The buried soil shows a bright red colour caused by redeposited hematite, resulting from temperate weathering during several stages of the Middle Pleistocene, in addition to a periglacial soil formed in the early part of the Anglian Glaciation but before the Anglian glaciers reached the site. Formerly, the till was considered to be evidence for two separate glacial stages, but recent analysis show that differences in appearance are due to the upper part being oxidised and the sediment is now considered to represent only one glacial event, of Anglian age, but within the till three facies are represented. In the western part of the quarry there is lodgement till; to the east, on the valley-side, melt-out till overlies a sheared basal till. In this part of the quarry the till is associated with chalky ice-proximal outwash gravels. The quarry is very important for showing the spatial relationship of the till facies and the topographic position of the outwash gravels. The wind-blown sands in the top-soil are Devensian. This is a key locality for Pleistocene studies. (S1).