Uplift-driven valley incision and climate-controlled river terrace development in the Thames Valley, UK

The sequence of terraces of the River Thames in southeast England has previously been shown to span the period from the earliest Pleistocene to the present. This terrace sequence contains biostratigraphical and sedimentary evidence that testifies to the high-amplitude climatic changes of the Quaternary. Large-scale fluvial incision, resulting in basin-wide terrace formation, appears to have been concentrated at the warming limbs of the major climatic glacial-interglacial cycles, when sediment supply was greatly reduced. This incision and subsequent valley-floor widening created the accommodation space for the later aggradation of the terrace sediments during the following warm-cold transitions and during the cold stages, when high-sediment supply conditions prevailed. Although the timing of terrace aggradation may be controlled by climate change, the progressive valley incision recorded by terrace staircases cannot easily be explained in terms of Quaternary climatic change alone and recently developed models suggest that long-term incision by the Thames has been driven by uplift. This paper presents an overview of the available terrace data and tabulates incision amounts and rates between key stratigraphic horizons. Superimposed upon these broad changes, revealed by the complex internal sedimentary architecture of many terrace sediments, are the geomorphological system responses to both higher-frequency climate-driven changes and more localized intrinsic fluvial system adjustments. (C) 2001 Published by Elsevier Science Ltd.