The Cenozoic fi ll of the Gulf of Mexico basin contains a continuous record of sediment supply from the North American continental interior for the past 65 million years. Regional mapping of unit thickness and paleogeography for 18 depositional episodes defi nes patterns of shifting entry points of continental fl uvial systems and quantifi es the total volume of sediment supplied during each episode. Eight fl uvio-deltaic axes are present: the Rio Bravo, Rio Grande, Guadalupe, Colorado, Houston-Brazos, Red, Mississippi, and Tennessee axes. Sediment volume was calculated from digitized handcontoured unit thickness maps using a geographic information system (GIS) algorithm to sum volumes within polygons bounding interpreted North American river contribution. General age-dependent compaction factors were used to convert calculated volume to total grain volume. Values for rate of supply range from >150 km to <10 km 3 /Ma. Paleogeographic maps for eleven Cenozoic time intervals display the evolving matrix of elevated source areas, intracontinental sediment repositories, known and inferred drainage elements, and depositional fl uvial/deltaic depocenters along the northern Gulf of Mexico basin margin. Patterns of sediment supply in time and space record the complex interplay of intracontinental tectonism, climate change, and drainage basin evolution. Five tectonoclimatic eras are differentiated: Paleocene late Laramide era; early to middle Eocene terminal Laramide era; middle Cenozoic (Late Eocene-Early Miocene) dry, volcanogenic era; middle Neogene (Middle-Late Miocene) arid, extensional era; and late Neogene (Plio-Pleistocene) monsoonal, epeirogenic uplift era. Through most of the Cenozoic, three to four independent continental-scale drainage basins have supplied sediment to the Gulf of Mexico.

No abstract

No abstract

Empirical scaling relationships between known deepwater siliciclastic submarine fan systems and their linked drainage basins have previously been established for modern to submodern depositional systems and in a few ancient, small-scale basins. Comprehensive mapping in the subsurface Gulf of Mexico basin and geological mapping of the North American drainage network facilitates a more rigorous test of scaling relationships in a continental-size system with multiple mountain source terranes, rivers, deltas, slopes, and abyssal plain fan systems formed over 65 m.y. of geologic time. An immense database of drilled wells and high-quality industry seismic data in this prolific hydrocarbon basin provide the independent measure of deepwater fan distribution and dimensions necessary to test source-to-sink system scaling relationships.Analysis of over 40 documented deepwater fan and apron systems in the Gulf of Mexico, ranging in age from Paleocene to Pleistocene, reveals that submarine-fan system scales vary predictably with catchment length and area. All fan system run-out lengths, as measured from shelf margin to mapped fan termination, fall in a range of 10%-50% of the drainage basin length, and most are comparable in scale to large (Mississippi River-scale) systems although some smaller fans are present (e.g., Oligocene Rio Bravo system). For larger systems such as those of the Paleocene Wilcox depositional episodes, fan runout lengths generally fall in the range of 10%-25% of the longest river length. Submarine fan widths, mapped from both seismic reflection data and well control, appear to scale with fan run-out lengths, though with a lower correlation (R 2 = 0.40) probably due to uncertainty in mapping fan width in some subsalt settings. Catchment area has a high correlation (R 2 = 0.85) with river length, suggesting that fluvial discharge and sediment flux may be primary drivers of ancient fan size.Validation of these first-order source-to-sink scaling relationships provides a predictive tool in frontier basins with less data. Application to less-constrained early Eocene fan systems of the southern Gulf of Mexico demonstrates the utility for exploration as well as paleogeographic reconstructions of ancient drainage systems. This approach has considerable utility in estimating dimensions of known but poorly constrained submarine fans in the subsurface or exposed in outcrop.

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.