Collaborative Research: A seismic experiment to investigate mantle dynamics during the early stages of seafloor spreading in the Atlantic

Ocean basins form as continents break apart and seafloor spreading begins. The Atlantic Ocean began to form in the Early Jurassic (~190 million years ago) as the Pangaea supercontinent rifted. This project seeks to understand how the central Atlantic Ocean first formed. Geologic data of this time suggest an anomalous geology at the time of initial seafloor spreading, but for reasons that are poorly understood. New marine seismic data will address the first ~50 million years of seafloor spreading in the western Atlantic, next to Eastern North America. The new seismic data will reveal the evolution of oceanic crust and mantle as the Atlantic formed. Participation by students and early-career scientists will give them first-hand experience in marine geophysics, and advance diversity, equity and inclusion in the geosciences.Formation of ocean basins is fundamental to plate tectonics, yet initial seafloor spreading processes remain enigmatic. The asthenosphere during incipient spreading is likely anomalous in its composition, temperature, and flow patterns compared to mature seafloor spreading. The timescales of thermal and chemical depletion of the mantle and establishment of normal seafloor accretion have not been resolved. This project will shed light on these processes by conducting a novel 2D/3D seismic experiment adjacent to the Eastern North American Margin, spanning the first ~50 Myr of seafloor spreading. The seismic survey will collect four profiles along which both multichannel seismic and ocean bottom seismometer (OBS) data will be acquired. Three shorter profiles will run parallel to paleo-spreading direction, and one long profile will be perpendicular to the shorter profiles. The new data will constrain the evolution of oceanic crustal thickness, composition, and basement roughness. In addition, OBS recordings of 3D active-source mantle refractions and ambient noise surface waves will be analyzed to infer the orientation and magnitude of asthenospheric anisotropy. Seismic observations will be synthesized with petrological models of mantle melting and oceanic crust crystallization to study the chemical composition and potential temperature of the mantle source regime and how it evolved over time during early seafloor spreading. This experiment will bridge a critical gap between existing seismic datasets across the rifted margin and on mature Atlantic oceanic lithosphere.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.