Fluvial floodplains prior to greening of the continents: Stratigraphic record, geodynamic setting, and modern analogues

摘要

Fluvial floodplains established prior to the greening of continents have long been overlooked, despite their relevance for landscape reconstructions in deep time. The record of fluvial overbank sedimentation dates back as far as the Mesoarchean, and mature assemblages of floodplain landforms had already developed at least by the early Palaeoproterozoic. In this review, a critical assessment of pre-vegetation floodplain processes and deposits is carried out through literature compilation and detailed descriptions of case studies. Pre-vegetation floodplains were variably composed of floodbasins, splay complexes (including crevasse- and distributary-channel fills and related splay lobes) and, in minor proportion, by channel levees. The hydrology of ancient floodbasin environments, mainly inferred from the occurrence or lack of evaporite features, is particularly topical and, once critically tested against other palaeo-environmental indicators, can be related to climate or catchment physiography.