Autogenic and Allogenic Controls on Deep-Water Sand Delivery: Insights from Numerical Stratigraphic Forward Modeling
Ashley Harris, Sarah Baumgardner, Andrew Madof, Tao Sun, Jacob A. Covault, Zoltán Sylvester, Didier Granjeon, "Autogenic and Allogenic Controls on Deep-Water Sand Delivery: Insights from Numerical Stratigraphic Forward Modeling", Sequence Stratigraphy: The Future Defined, Bruce Hart, Norman C. Rosen, Dorene West, Anthony D’Agostino, Carlo Messina, Michael Hoffman, Richard Wild
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Allogenic and autogenic processes interact to regulate sediment distribution in sedimentary basins. Depositional systems can respond in a complex manner to these processes, complicating interpretation of the controls on the stratigraphic record. Here we used published and constant eustatic curves in a stratigraphic forward model to examine the effects of sea-level variation on deep-water sand delivery on a passive continental margin. We found that: (1) models with constant sea level and those with eustatic fluctuations deliver similar volumes of sand to deep water; (2) both large and small eustatic variations result in similar magnitudes of fluctuations in deep-water sand delivery; and (3) deep-water sand delivery signals show similar periodicities for all models. These results suggest that the characteristics of the imposed eustatic curve may not have a significant impact on the total volume of sand delivered to deep water. We propose that the equilibrium state of the shelf-edge delta, where no net deposition or erosion occurs, could explain the similarity in deep-water sand volumes. We posit that such a state could be induced by the progradation of an initial shelf-edge delta that creates a slope which maximizes the efficiency of sediment delivery across the shelf. Because our models show that autogenic and allogenic processes can result in similar deep-water sand volumes, we conclude that other characteristics of sediment-routing systems, such as sediment supply, must exert strong controls on deep-water sand volume.