River incision and terrace formation in the Late Cenozoic of Europe

Abstract

Late Cenozoic environmental changes which affected European rivers are reviewed, focusing especially on those of mid-Pleistocene times (c.1.2–0.8 Ma or around MIS 22) and thereafter. These involved dominating but fluctuating cold-climate (periglacial) conditions, shorter but major episodes of glaciation, and brief interglacials. There were also related sea-level and tectonic responses. The known history of European rivers in this period is individually varied, but is predominantly marked by multiple stages of episodic incision the form of which changed in style at around the ‘mid-Pleistocene transition’. It is suggested that the nature of climatic oscillations, the dating of incision episodes and the processes that achieve this incision are as yet insufficiently understood. Fluvial process studies suggest that the onset of incision may broadly relate to changes in slope, discharge, sediment load and calibre, and bedrock erodibility, and these may all have been transformed as the direct or indirect result of mid-Pleistocene climatic changes. Common properties of basal sediments on strath terraces suggest that it was during the extended but variable cold-stage episodes that both valley deepening and lateral widening occurred, and that climatic change was the principal driver of episodic deep valley incision.