Quaternary fluvial archives and landscape evolution: a global synthesis

Late Cenozoic (and especially Quaternary) fluvial deposits and related landforms provide valuable information about landscape evolution, not just in terms of changing drainage patterns but also documenting changes in topography and relief. Recently compiled records from river systems worldwide have shed much light on this subject, particularly records of terrace sequences, although other types of fluvial archive can be equally informative. Terraces are especially valuable if they can be dated with reference to biostratigraphy, geochronology or by other means. The various data accumulated support the hypothesis that the incision observed from river terraces has been a response to progressive uplift during the Late Cenozoic. This has not occurred everywhere, however. Stacked fluvial sequences have formed in subsiding depocentres and have greater potential for surviving to become part of the longer-term geological record. More enigmatic are regions in the ancient cores of continents (cratons), which show little indication of sustained uplift or subsidence, with fluvial deposits of various ages occurring within a restricted range of elevation with respect to the valley floor. In areas of dynamic crust that were glaciated during the Last Glacial Maximum, post-glacial river valleys are typically incised and often terraced in a similar way to valleys on post-Precambrian crust elsewhere, although the terraces and gorges in these systems are very much younger (∼15 ka) and therefore the processes have been considerably more rapid. This paper is illustrated with various case-study examples of these different types of archives and discusses the implications of each for regional landscape evolution.