Electric conductivity and magnetic susceptibility are standard physical parameters in environmental geophysics. Both can be obtained from electromagnetic induction (EMI) methods. In comparison to the extensive use on land, near surface applications of EMI methods in coastal and shelf regions are relatively novel. Recognizing the power of electromagnetic data to provide information, useful for many different fields in marine and coastal geoscience ranging from geotechnics to sediment dynamics, we developed the electromagnetic benthic profiler NERIDIS III at the MARUM – Center for Marine Environmental Sciences. This bottom-towed sled is equipped with a commercial, controlled-source EMI sensor modified for underwater applications. We use an inversion algorithm employing the in-phase and quadrature components of five operation frequencies to reconstruct the lateral distributions of electric conductivity and magnetic susceptibility of shallow marine deposits. Vertical distribution of conductivity is also recovered through 1-D inversion. Both parameter offers complementary information as electric conductivity is primarily considered as a measure of porosity (grain size, sorting), while magnetic susceptibility is used as a proxy for fine-grained terrigenous or iron mineral content and anthropogenic metallic contaminants.


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