Landscape Evolution Coupled to Fluvio-Deltaic Deposition: Implications for the Sequence Stratigraphy of Tectonically Active Continental Margins
Covault, Jacob A. and Sun, Tao
Terrigenous sediment is delivered to fluvio-deltaic depositional systems and submarine fans in deep-ocean basins, where it forms a stratigraphic record of the evolution of Earth's surface and climate. However, transient storage of sediment in route to its ultimate site of deposition can complicate the stratigraphic record by introducing lags. We aim to constrain the temporal and spatial distributions of sediment across a routing system and evaluate the stratigraphic response to external forcings. We developed a transport-limited landscape evolution model combined with a fluvio-deltaic depositional model in order to conceptualize source-to-sink sediment dispersal in a spatially restricted, tectonically active Southern California sediment routing system. The routing system comprises drainage basins of the Peninsular Ranges linked to submarine fans of the California Continental Borderland. The landscape evolution model links climate (precipitation) and tectonic uplift to the catchment drainage density, which, in turn, predicts water (Qw) and sediment (Qs) discharge to the distributary fluvio-deltaic system through a continuity condition for Qw and Qs, as well as morphological continuity. The fluvio-deltaic system is also subjected to sea-level fluctuations. In the absence of strong wave interactions and longshore currents, sediment is stored in accommodation on the continental shelf during periods of rising and high sea level. Even in narrow shelves offshore of Southern California (on average ~5 km wide), accommodation, set by the present sea level, will not be completely filled with sediment for another 60 k.y. However, longshore drift at high sea level can distribute sediment to a submarine canyon head at the end of a littoral cell, thereby providing sediment to deep-water depositional systems. These results are supported by a latest Pleistocene-Holocene sediment budget for the drainage basins of the Peninsular Ranges and the offshore Oceanside and La Jolla deep-water fans. Our numerical analytical model allows for us to test the sensitivities of climate, uplift, grain-size, and sea-level variation on sediment transport and deposition from source to sink. Results of this experiment will provide insights into the temporal and spatial distributions of sediment, as well as the sequence stratigraphic response to environmental changes and drainage-basin modification.
AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013