Abstract:

Submarine canyons influence oceanographic processes, sediment transport, productivity and benthic biodiversity from the continental shelf to the slope and beyond. However, not all canyons perform the same function. The relative influence of an individual canyon on these processes will, in part, be determined by its form, shape and position on the continental margin. Here we present an analysis of canyon geomorphic metrics using an updated national dataset of 713 submarine canyons surrounding mainland Australia. These metrics (attributes) for each canyon are used to classify them into canyon types across a hierarchy of physical characteristics separately for shelf-incising (n= 95) and slope-confined (blind; n = 618) canyons. We find that the canyon metrics describe a wide variety of canyon form and complexity that is consistent with a population of canyons that has evolved at different rates around the Australian margin since the break-up of Gondwana. The large number of slopeconfined canyons is interpreted to reflect dominance of slope mass-wasting processes over erosive turbidity flows from fluvial and shelf sources on an arid continent. The distribution of submarine canyons around the Australian margin is not regular, with clusters occurring in the east, southeast, west and southwest where the margin is steepest. The classification result provides a quantitative framework for describing canyon heterogeneity for application in studies of geological controls on individual canyons, canyon oceanography and canyon biodiversity.

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