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Sediment Dispersal Pattern of the Paleogene Wilcox Formation in the Deep-Water Gulf of Mexico Basin Based on Detrital Zircon Analysis and Forward Modeling


An integrated source-to-sink analysis was conducted for the Paleocene-Eocene Wilcox Formation with the main objectives to understand provenance, extent of drainage areas, and sand-delivery pathways in the offshore Gulf of Mexico. For this study we used detrital zircon provenance analysis of onshore and offshore samples and stratigraphic forward models calibrated to regional isopach maps and constrained by paleo-environmental parameters. The Wilcox Formation includes the sediment of Late Paleocene to Early Eocene age. By early Paleocene the drainage area included the southern part of North America from the Western Cordillera to the Appalachian Mountains in which several major deltaic-fluvial systems developed. The data for this study include 1540 new detrital zircon U-Pb analyses representing 14 samples from the five offshore wells covering the entire deep-water Wilcox system in the east-west direction. Results from offshore wells corroborated by published onshore samples suggest a shift in the Wilcox sediment provenance from Paleocene to Eocene and in the east-west direction. The shift is reflected by the varying activity of the Holly Springs, Rockdale, and Rosita delta complexes. The eastern part of the system was fed by the Holly Springs through Paleocene and Eocene. The central part of the system showed mixed signatures reflecting the overlapping input from the Rockdale and Holly Springs deltas in the Paleocene, with latter being less active in the Eocene. The western part of the system has an overall increased volume of the younger grains from Cordilleran arc, reflecting a predominant input from the Rosita Delta, or alternatively reworking of distal plinian ash deposits. The sediment delivery to the deep-water from the Paleo-Tennessee River was not significant suggesting the presence of a smaller system with most of the sediments probably stored on the shelf. Stratigraphic forward models using Dionisos were built based on paleoenvironmental parameters, mass-balance constraints, and global sediment supply databases. The models were calibrated to isopach maps, well data, and the provenance analysis results. These models provide an improved understanding and visualization of the evolution of the Wilcox depositional system and offer probabilistic scenarios for distribution of depositional environments and position and gradient of the paleoslope, linking the well-known onshore and offshore parts of the system.