Thames River sediments of the British Early and Middle Pleistocene

Abstract

The Thames drainage system contains the most complete record of fluvial sediments in the British Quaternary. The Kesgrave Sands and Gravels form the main body of this sediment having been deposited over an interval that spans the later part of the Early Pleistocene and most of the Middle Pleistocene (conventional stages: Pre-Pastonian a through to early Anglian, ca. 1.2 ma). This deposit provides a stratigraphic context for related bio-, morpho-, and pedostratigraphic evidence and for the recognition of pre-Anglian (pre-OI Stage 12) upland glaciation in the Welsh mountains and intense periglaciation in lowland England. It also facilitates correlation with the stratigraphy of northern Europe and the global pattern of orbitally forced climatic change. This paper describes the first catchment-wide correlation of Thames river sediments, and proposes a formal redefinition of the lithostratigraphic units concerned. The scheme outlined here is based on two lithologically distinctive formations defined at type areas, reflecting significant changes in catchment dimensions. The earlier Sudbury Formation was formed when the Thames catchment extended into Wales and drained northwards across East Anglia; the later Colchester Formation was formed after the upper catchment had been reduced in extent to that of the present river, but continued to flow across East Anglia. The whole sediment body is now named the Kesgrave Group.