DEEP-WATER CHANNEL RUN-OUT LENGTH: INSIGHTS FROM SEAFLOOR GEOMORPHOLOGY

The seafloor provides high-resolution, but relatively static, perspectives of submarine sediment-routing systems, which can be employed in the development of predictive models of deep-water stratigraphic sequences. We compare 31 seafloor canyon-and-channel systems from predominantly siliciclastic continental margins and discuss their morphologic variability. The longest canyon-and-channel systems of this study generally correspond with relatively mature, passive continental margins associated with some of the largest deep-sea fans in the world with long-term, voluminous, mud-rich sediment supply. Shorter, lower-relief canyon-and-channel systems generally correspond with immature margins associated with relatively meager, sand-rich or mixed-caliber sediment supply. Seafloor continental-margin relief nonlinearly corresponds with canyon-and-channel-system length, with very high-relief margins exhibiting longer canyon-and-channel systems than predicted by a linear relationship. Nonlinearity in our observations can be accounted for by the increased occurrence and magnitude of submarine mass wasting in higher-relief and correspondingly longer canyon-and-channel systems, limitations of relief imposed by the maximum depths of ocean basins, and sediment-gravity-flow dynamics. These interpretations of controls on canyon-and-channel geomorphology represent extrinsic characteristics of land-to-deep-sea sediment supply and basin or continental-margin framework and intrinsic sediment-gravity-flow dynamics. We demonstrate that insights into seafloor channel processes, morphologic products, and scaling relationships can be broadly applied to predicting ancient subsurface and outcropping deep-water stratigraphic sequences. Our comparative analysis suggests that knowledge of the thickness of an ancient basin-margin stratigraphic sequence can be employed in order to generally predict the basinward extent of a paleo-canyon-and-channel system and underlying depositional fan. The application also potentially works in reverse: intimate knowledge of the deep-water component of a continental margin or basin margin can facilitate understanding of up-depositional-dip stratigraphic architectures where data might be lacking.