Palaeoenvironmental history of the Middle Pleistocene deposits at Gilson, Warwickshire, England: part of the High Speed Two railway route alignment

The investigation of a hillside at Gilson (Lat. 52.510341, Long. -1.718313), southwest of Coleshill, Warwickshire (within the High Speed Two railway 'Delta Junction' compound), England, has yielded evidence of sedimentation during a temperate stage. The site's stratigraphy starts with the aggregation of cold-climate sand and gravels deposited during the Anglian Stage within the proto-Tame and proto-Blythe palaeovalleys. A warm-climate period is recorded by the infill of organic material representing the second half of the Hoxnian interglacial Stage. Picea, Abies and Pinus dominate vegetation within a swamp-like environment, before a Pinus forest develops in the upper part of the organic sequence. The following cold-climate period saw incision and aggregation of the surrounding region throughout much of the Wolstonian and Devensian Stages, where much of the overlying silt, sand and gravel were reworked under intense periglacial conditions. Presented here is a geophysical examination of the shallow basin by ground-penetrating radar undertaken to understand the spatial distribution and stratigraphical history of the basin. The deposits at Gilson provide a valuable stratigraphic marker in the glacial sequence of the English West Midlands and are correlated to similar deposits at neighbouring Quinton and Nechells. At these regional sites organic accumulation occurred for most of the temperate stage, infilling lake basins. These sequences indicate an environment dominated by pollen of Abies, Quercus, Ulmus and Corylus woodland vegetation. These assemblages differ markedly from those typically found in the last interglacial and confirm correlation to the Middle Pleistocene Hoxnian interglacial Stage (c. MIS 11c).