A Towed Electromagnetic Survey System for Mapping Shallow Sedimentation Porosity

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Funds are provided to purchase and develop a towed electromagnetic (EM) survey system which determines the porosity structure of the upper sediment column (1-20m below seafloor) across the continental shelf and slope. Such a device builds upon a similar, but unique system developed in Canada that was successfully used to identify regions of shallow gas and/or fresh water seeps. The method is able to provide quantitative estimates of sedimentary porosities over much larger areas than any other technique that currently exists. Towed EM instruments are the only tools able to provide quantitative estimates of porosity in noncohesive sediments. Combining EM data with more conventional geophysical measurements allows investigators to understand how porosity and permeability of sediments evolve through time.The EM survey system will be used in a multi-disciplinary manner to determine processes which shape the formation and evolution of the continental shelf, the critical boundary between continent and deep ocean. In particular they directly address issues of understanding process and product in shallow waters, identified as a key research area by the MARGINS initiative.