This paper uses detrital zircon (DZ) provenance and geochronological data to reconstruct paleodrainage areas and lengths for sediment-routing systems that fed the Cenomanian Tuscaloosa-Woodbine, Paleocene Wilcox, and Oligo cene Vicksburg-Frio clastic wedges of the northern Gulf of Mexico (GoM) margin. During the Cenomanian, an ancestral Tennessee-Alabama River system with a distinctive Appalachian DZ signature was the largest system contributing water and sediment to the GoM, with a series of smaller systems draining the Ouachita Mountains and discharging sediment to the western GoM. By early Paleocene Wilcox deposition, drainage of the southern half of North America had reorganized such that GoM contributing areas stretched from the Western Cordillera to the Appalachians, and sediment was delivered to a primary depocenter in the northwestern GoM, the Rockdale depocenter fed by a paleo-Brazos-Colorado River system, as well as to the paleo-Mississippi River in southern Louisiana. By the Oligocene, the western drainage divide for the GoM had migrated east to the Laramide Rockies, with much of the Rockies now draining through the paleo-Red River and paleo-Arkansas River systems to join the paleo-Mississippi River in the southern Mississippi embayment. The paleo-Tennessee River had diverted to the north toward its present-day junction with the Ohio River by this time, thus becoming a tributary to the paleo-Mississippi within the northern Mississippi embayment. Hence, the paleo-Mississippi was the largest Oligocene system of the northern GoM margin. Drainage basin organization has had a profound impact on sediment delivery to the northern GoM margin. We use paleodrainage reconstructions to predict scales of associated basin-floor fans and test our predictions against measurements made from an extensive GoM database. We predict large fan systems for the Cenomanian paleo-Tennessee-Alabama, and especially for the two major depocenters of the early Paleocene paleo-Brazos-Colorado and late Paleocene-earliest Eocene paleo-Mississippi systems, and for the Oligocene paleo-Mississippi. With the notable exception of the Oligocene, measured fans reside within the range of our predictions, indicating that this approach can be exported to other basins that are less data rich.

Shelf sand ridges are common features on many modern continental shelves but have not been widely cited as analogs for ancient sand bodies. Modern shelf sand ridges are elongate, coastal- to shelf-sand bodies that are larger than subaqueous dunes, with lengths of the order of 10 km and heights that are more than 20% of the water depth. These ridges are also longer-lived than smaller bedforms, persisting for thousands to tens of thousands of years. Progress in understanding these features has gone from early studies of their morphology and surficial-sediment characteristics to recent investigations of current and wave dynamics and establishment of their internal stratigraphy through vibracoring. From these studies, it is clear that once formed, most ridges are maintained and even enlarged by present-day shelf-flow dynamics. Ridges existing in tide- and storm-dominated shelf regimes share many similarities, which suggests that both are formed by the same fundamental interaction between flow and an initial bathymetric irregularity. The Huthnance (1982) hydrodynamic model appears to offer an adequate description of that interaction. Synthesis of previous work indicates that storm- and tide-dominated ridges pass through three stages of development: 1) an initial irregularity (the ridge nucleus) forms due to coastal or shelf processes; 2) nearshore and/or shelf currents (either storm- or tide-driven) interact with the irregularity in the manner described by the Huthnance model; and 3) the ridge evolves as a result of continued current action. These processes and events are most likely to occur during transgressions, because sandy coastal deposits, the most common ridge nuclei, are reworked on the shelf as relative sea level rises. Thus, most ridges are expected to overlie the transgressive ravinement surface. Understanding the nature of the initial irregularity and the amount of subsequent migration is the key to explaining the diversity of ridge characteristics. Based on the degree of ridge evolution, we categorize shelf ridges into three classes: Class I-juvenile or stationary ridges that retain their initial nucleus; Class II- ridges that have migrated somewhat but retain part of their nucleus; and Class III- "fully evolved" ridges that have migrated sufficiently that they contain no trace of their origin. The degree of ridge evolution greatly affects the economic potential of ancient subsurface analogs, as ridge reworking/remolding during migration results in cleaner sand and increased sand-body volume. Transgressive conditions are most favorable for ridge development (e.g., Transgressive Systems Tracts), given the presence of widened shelf areas, drowned bathymetric irregularities that act as ridge nuclei, and loose sand derived from ravinement.

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Hydrocarbon exploration in the last decade has yielded sufficient data to evaluate the Gulf of Mexico basin response to the Chicxulub asteroid impact. Given its passive marine setting and proximity to the impact structure on the Yucatán Peninsula, the gulf is the premier locale in which to study the near‐field geologic effect of a bolide impact. We mapped a thick (decimeter‐ to hectometer‐scale) deposit of carbonate debris at the Cretaceous‐Paleogene boundary that is ubiquitous in the gulf and readily identifiable on borehole and seismic data. We interpret deposits seen in seismic and borehole data in the deepwater gulf to be predominately muddy debrites with minor turbidites based on cores in the southeastern gulf. Mapping of the deposit in the northern Gulf of Mexico reveals that the impact redistributed roughly 1.05 × 105 km3 of sediment therein and over 1.98 × 105 km3 gulfwide. Deposit distribution suggests that the majority of sediment derived from coastal and shallow‐water environments throughout the gulf via seismic and megatsunamic processes initiated by the impact. The Texas shelf and northern margin of the Florida Platform were significant sources of sediment, while the central and southern Florida Platform underwent more localized platform collapse. The crustal structure of the ancestral gulf influenced postimpact deposition both directly and indirectly through its control on salt distribution in the Louann Salt Basin. Nevertheless, impact‐generated deposition overwhelmed virtually all topography and depositional systems at the start of the Cenozoic, blanketing the gulf with carbonate debris within days.

We image deep crustal structure using marine seismic refraction data recorded by a linear array of ocean-bottom seismometers in the Gulf of Mexico Basin Opening project (GUMBO Line 3) in order to provide new constraints on the nature of continental and oceanic crust in the northeastern Gulf of Mexico. GUMBO Line 3 extends~524 km from the continental shelf offshore Pensacola, Florida, across the De Soto Canyon and into the central Gulf basin. Travel times from long offset, wide angle reflections and refractions resolve compressional seismic velocities and layer boundaries for sediment, crystalline crust, and upper mantle. We compare our results with coincident multichannel seismic reflection data. Our velocity model recovers shallow seismic velocities (~2.0-4.5 km/s) that we interpret as evaporites and clastic sediments. A Cretaceous carbonate platform is interpreted beneath the De Soto Canyon with seismic velocities >5.0 km/s. Crystalline continental crust thins seaward along GUMBO Line 3 from 23-10 km across the De Soto Canyon. High seismic velocity lower crust (>7.2 km/s) is interpreted as extensive syn-rift magmatism and possibly mafic underplating, common features at volcanic rift margins with high mantle potential temperatures. In the central Gulf basin we interpret thick oceanic crust (>8 km) emplaced at a slow full-spreading rate (~24 mm/yr). We suggest a sustained thermal anomaly during slow seafloor-spreading conditions led to voluminous basalt flows from a spreading ridge that overprinted seafloor magnetic anomalies in the northeastern Gulf of Mexico.