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Quantifying Sediment Supply to Continental Margins: Application to Paleogene Wilcox Group Deposition, Gulf of Mexico

Abstract

Sediment supply to the ocean influences basin-margin evolution and reflects upstream landscape evolution, including patterns of sediment routing, denudation, and tectono-climatic perturbations in source areas. Constraining sediment supply is useful for inputs to stratigraphic forward models and for predictions of reservoir presence and quality. Because of the importance of sediment supply, geologists have developed various methods to estimate it. Here we present a workflow to estimate the sediment loads delivered from four Paleocene-Eocene North American river networks, the paleo-Rio Grande, Colorado/Houston-Brazos, Mississippi, and Tennessee, to the Wilcox Group, Gulf of Mexico. We perform Monte Carlo simulation of the BQART analytical model to probabilistically predict sediment load. The BQART model describes the empirical relationship between river catchment paleogeography, climate, and sediment load. The combined sediment load of the Paleocene-Eocene North American river networks diminished from a mean of 428 to 148 Mt/yr. This decrease corresponds with a period of drainage capture and a significant tectonic reorganization of the North American hinterland related to the Laramide orogeny. The mean sediment load from individual river networks varies considerably across the Gulf Coast (18-202 Mt/yr) depending on paleogeographic and climatic inputs. We balanced our Paleocene-Eocene sediment budget by comparing our upstream predictions of sediment supply to downstream depositional records of the Wilcox Group from subsurface mapping. Upstream sediment supply reconstruction reflects the temporal and spatial trends of Paleocene-Eocene Wilcox Group deposition. Our predictions of upstream sediment supply tend to be more accurate and precise than other empirical-based methods based on river catchment area, maximum relief, and channel-belt dimensions. Our probabilistic approach to sediment supply prediction, accounting for uncertainty in paleogeography and climate, is applicable in frontier exploration settings. Future work should include more integration of empirical-based methods with physics-based experimental and modeling approaches, such as those based on diffusion assumptions.