Describing fluvial systems: Linking processes to deposits and stratigraphy

The period since the 1960s witnessed significant progress in our ability to decipher the clastic rock record from a wide range of sedimentary environments, and spanning many spatio-temporal scales, from milli-metric to that of the sedimentary basin, and involving processes acting on timescales of seconds to millions of years. This review assesses advances in four areas of fluvial sedimentology: the nature of alluvial dunes, the role of fine-grained suspended sediment, the linking of facies models and channel planform, and the reconstruction of drainage networks within ancient sedimentary successions. The synthesis reveals that we require new thinking and research to: (1) address the range of stratification produced by dunes and their palaeohydraulic implications; (2) evolve new bedform phase diagrams capable of incorporating the reality that many fluids transport fine-grained sediment, both in flow and within the bed, which may significantly modify the bedform morphology and phase space when compared with existing bedform stability diagrams; (3) develop new alluvial facies models in which planform channel pattern is not the fundamental discriminant; and (4) re-establish consideration of process mechanics as the heart of developing ideas and debates concerning fluvial deposit preservation and alluvial architecture.