Seismic Stratigraphy of Contourite Drift Deposits Associated With the Loop Current on the Eastern Campeche Bank, Gulf of Mexico.

The Loop Current is a key component of global circulation via the northward transport of warm, salty water, and an important influence on Gulf of Mexico hydrography. Understanding how the Loop Current will respond to ongoing anthropogenic warming is critically important, but the history of the Loop Current is poorly known. Here, we present the results of a high resolution (3–8 m) multichannel seismic survey of pelagic carbonate sediment drifts on the eastern Campeche Bank associated with the Loop Current. We identify three seismic megasequences: Megasequence A is a Lower Cretaceous carbonate platform, Megasequence B comprises Cretaceous to lower Cenozoic pelagic carbonates with weak/no contour current flow, and Megasequence C comprises a series of large (100s of m thick) contourite drifts representing the inception and history of the Loop Current. The base of the contourites is marked by a regionally mappable unconformity eroding underling strata, sometimes incising hundreds of meters. The drifts contain a succession of sequence sets separated from each other by regional unconformities and comprising plastered drifts and massive mounded drifts, which characterize modern deposition with active moats on the seafloor. A lack of sediment cores in the study area precludes age determination of these drifts, except for the youngest (Late Pleistocene). Comparison to legacy seismic lines across Deep Sea Drilling Project Site 95, outside our study area, implies that the base of Megasequence C is Oligocene in age, and that the Loop Current developed during the global reorganization of ocean circulation around the Eocene‐Oligocene Transition. Plain Language Summary: The Loop Current flows into the Gulf of Mexico from the Caribbean through the Yucatán Strait and exits to the Atlantic Ocean through the Straits of Florida. It is part of a series of currents that carry warm, salty water to the far North Atlantic, where it cools and sinks, and becomes a critical part of global ocean circulation. The Loop Current is also important for Gulf of Mexico climate, as it sometimes spins off warm eddies which drift west, disrupting fisheries and providing a warm water fuel source for hurricanes. Because of its role in global and regional climate, it is important to understand how the Loop Current will respond to ongoing climate change, and an essential part of that effort is seeing how it has responded to past climate changes. Here, we report the results of a seismic survey of sediment drifts on the eastern Campeche Bank which we believe records the initiation and history of the Loop Current. A lack of sediment cores in this area makes it hard to put age constraints on our observations, so we evaluate several plausible hypotheses about when the Loop Current first formed and what that means for the current's future. Key Points: High resolution multichannel seismic data reveal the evolution of contourite drifts associated with the Loop CurrentContourite deposition began in the Cenozoic, and overlies Cenozoic and Cretaceous pelagic sediments with little evidence of bottom currentsComparison of seismic facies with those present at nearby DSDP Site 95 suggest the Loop Current began in the early Oligocene [ABSTRACT FROM AUTHOR]