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Fluvial rocks and sediments form an important part of the geological record from the terrestrial environment, from the Archaean to the recent. Precambrian fluvial archives record the change in Earth's atmosphere from anoxic to oxygen-rich, while the absence of land plants led to significant differences between Precambrian and Palaeozoic fluvial regimes and those from later in the geological record. In the Mesozoic and Cenozoic, river valleys were populated by land animals and their deposits are repositories for the fossils that record these biomes: dinosaurs and mammals being the prominent groups, respectively, in these eras. By the Cenozoic some of the drainage systems that exist at present had been initiated; their evolution during this era, and especially in the Quaternary, is evident from fluvial archives worldwide. The record of Quaternary rivers reveals the increasing influence of global cooling, with the severity of climate a potential driver of erosional isostatic uplift, bringing about incision of landscapes and the formation of river terraces in all but the most stable areas and subsiding basins. In the Holocene the fluvial environment experienced increasing influences from early humans as catchments and slopes were transformed by deforestation and farming, and later by industries such as mineral mining. These themes are represented in contributions to this special issue, arising from a Geologists’ Association conference and field meeting convened in Exeter in October 2012. |
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