Abstract

Recent exploration discoveries have extended the play fairway for Ceno-Turonian age sandstones from traditional onshore fields into the ultradeep water of the Gulf of Mexico (GOM), necessitating a reevaluation of the basin-scale depositional paleogeography. The Eagle Ford-Tuscaloosa (EFT) supersequence is a long-duration (10 my) aggregate of sand-prone depositional sequences, organic-rich shales, and shallow to deepwater carbonates. Tectonic drivers may help to explain how the Tuscaloosa depositional transport systems were able to surmount the prominent shelf-margin reef barrier that previously trapped so much sand in updip shoreline systems in underlying Lower Cretaceous supersequences. The EFT and underlying Paluxy-Washita supersequences were mapped across the Gulf Basin, from onshore to deep water, using a database of released wells, biostratigraphy, and proprietary 2D seismic data. Mapping reveals a carbonate- and shale-dominated, shallow to deep basin bisected by a sand-prone central corridor with two prominent depositional axes extending toward the Keathley Canyon and Mississippi Canyon protraction areas. Our paleogeographic reconstruction pointed to a large extrabasinal fluvial system with a catchment draining the Appalachians, confirmed by recently published detrital zircon provenance results. An older but underappreciated model for a brief but significant phase of uplift of the Mississippi embayment may explain how the basal sandstone units of the Tuscaloosa prograded and supported a large submarine fan extending more than 500 km (310 mi) from the previous Albian shelf margin. The estimated volumes of sediment generated by the local uplift are at least an order of magnitude too small to explain the deepwater grain volume suggesting related regional extension of drainage catchments during the tectonic event. Our work reveals the extent of a large sand fairway with an areal size, fan run-out length, and reservoir volume comparable in some respects with the hydrocarbon-rich Paleogene (Wilcox) in the central GOM.

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