Seismic Stratigraphic Reconstruction of Cretaceous to Holocene Current Flow Through the Southeastern Gulf of Mexico

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Ocean circulation in the Gulf of Mexico (GoM) is dominated by the Loop Current, which flows into the Gulf through the Yucatan Channel between Mexico and Cuba and then loops up and around the Gulf before entering the Florida Straits between Florida and Cuba, where it forms the Florida Current and feeds into the Gulf Stream. This system of connected ocean currents is one of the main mechanisms for transporting heat northward in the Atlantic Ocean and thus has a key influence on the climate of North America and Europe. Despite the importance of the Loop Current for regional and global climate, little is known about its long-term history, including when it was established and how it has varied through time. Understanding how the Loop Current has impacted the northward delivery of heat in response to changes in outside forcing, for example, is critical for reconstructing ocean/climate history and for predicting future changes. Fortunately, a unique record of past Loop Current behavior is preserved in sediment drift deposits preserved on the ocean floor. As currents flow across the seafloor, they move sediment around. Sediment is eroded from areas where currents are stronger and deposited where current velocity drops. Over time, these sediments can form thick accumulations known as drift deposits that represent archives of past current flow over millions of years. Recent echosounder surveys have identified sediment drifts on the shallow Campeche Bank in the GoM. In the adjacent deep waters, seismic surveys conducted in the 1980s revealed large features on the seafloor that also appear to be sediment drifts, though these older data do not have the resolution to see internal features that are key to interpreting changes in current strength and position. This project will conduct a high-resolution multichannel seismic (MCS) survey of the deposits in both regions to map and determine the nature of these deposits and use their 3-D seismic architecture to reconstruct the Gulf of Mexico's Loop Current over the past 90 million years. The seismic data obtained will also be used as a site survey for potential future scientific drilling in the region.This project is a multinational collaboration being conducted with scientists at the National Autonomous University of Mexico (UNAM) and from Germany and Cuba. The project team will deploy the University of Texas Institute for Geophysics' portable multichannel seismic system on board UNAM's R/V Justo Sierra to conduct a seismic survey along the Campeche Bank and adjacent deep-water environments to image the drift deposits there. The ages of the sedimentary units will be determined by tracing key horizons within them to cores previously collected within the study area by the Deep Sea Drilling Project. The combined data will be used to test the following hypotheses: 1) changes in the strength of currents entering the eastern GoM drove changes in the sedimentary architecture of both the shallow Campeche Bank and the adjacent deeper water; 2) progressive cooling throughout the Cenozoic has strengthened current flow in the eastern GoM, resulting in both increased scour in some areas and increased drift deposition in others; 3) drift deposits on shallow Campeche Bank extend back to the Late Cretaceous, indicating the presence of a proto-Loop Current entering the GoM for ~90 million years; and 4) significant drift deposits in the deeper basin between the Yucatan and Florida Straits date back to the Eocene/Oligocene Boundary and track the inflow of North Atlantic Deep Water into the GoM. By identifying and studying drift deposits in the eastern GoM, this project will pave the way for future scientific ocean drilling to core these drifts and study changes in Gulf of Mexico circulation and climate in much greater detail.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.