ABSTRACT

This paper describes temporary sections from a gravel quarry at Broomfield, near Chelmsford, Essex and places them within the regional geological context. There, two thin beds of silt and clay, containing organic material, were exposed within gravels and sand of the Kesgrave Formation, and underlying the temperate Valley Farm Soil and gravel and till of the Lowestoft Formation. The lower of the two horizons is interpreted as a laterally discontinuous unit of organic silt and clay laid down in a pool or partially abandoned meander channel on a river floodplain. The deposit is rich in fossils which indicate accumulation during the early temperate substage of an early Middle Pleistocene interglacial. Pollen spectra demonstrate mixed deciduous woodland, and plant macrofossils indicate a mosaic of local floodplain environments. They include water plants, such as the large water lily Euryale ferox , the first record from Britain, Azolla filiculoides, Salvinia natans, Trapa natans and Naias minor, not native in Britain today, which-require warmer summer temperatures than occur in Britain at present, though winters may have been cold. The sparse fauna of molluscs, small vertebrate and fish remains recovered reflects similar conditions. Fossil insects again indicate a similar range of habitats, and also include several species of southern aspect, some also no longer found in Britain.

The second deposit comprises silt, clay and sand filling a channel in the gravel and sand sequence overlying the temperate sediments. The contained pollen and spores indicate sediment accumulation under cold-climate conditions on the river braidplain, with a local herb-dominated vegetation of typical full-glacial type.

The palaeontological evidence suggests that the lower organic sequence represents a fragment of a previously unrecognised early Middle Pleistocene temperate stage not unlike the Cromerian sensu stricto., but, on stratigraphical and palaeontological grounds, probably older. Thus the deposits are thought to predate the Cromerian, yet post-date the Pastonian Stages, but correlation with the classic sequences of the North Norfolk coast and with the Beestonian is uncertain,.