The magnetic susceptibility established into a fast and non-invasive parameter to estimate pollution pathways, transport processes and diagenetic alteration of marine sediments. Recent magnetic investigations that are concerned within this context are in the majority laboratory analyses of grabbed or cored samples with limited spatial resolution. Core sampling and chemical analysis can also be prohibitively expensive and impracticable in large basins. While conventional susceptibility-meters show unfeasible to measure under high conductive seawater conditions, the sensitivity of magnetometers is poor to resolve small scale variations of sedimentary structures, especially in the vicinity of a relatively strong magnetic basement. Thus, an appropriate technique for high resolution in-situ measurements in the marine realm was missing when this story began.
2007 - 2009 NERIDIS II
Synchronous in-situ mapping of the magnetic and electric signatures of marine near-surface sediments is realized by the development of a marine electromagnetic profiler, devised for coastal and shelf operations in 5 to 500 m water depths. Magnetic susceptibility is used as a proxy for fine-grained terrigenous clay/silt content, diagenetically forced magnetite depletion, as well as anthropogenic contaminants.
The system is designed to resolve subtle and gradual variations in silt and clay content, porosity and diagenesis state of marine sediments at a sub-meter scale. The electric conductivity depends on porosity, the grain-size distribution and conductivity of the pore fluid. A commercial electromagnetic (EM) induction sensor was modified for submarine operations and mounted into a special bottom-towed sled. Seawater conductivity is measured synchronously by an integrated conductivity-temperature-depth (CTD) probe.
2010 NERIDIS III
The newly designed modular multi-sensor Benthic Shuttle enables the combined use of electromagnetics, CTD and surface sampling with existing in-situ sensors (mass spectrometer, side scan sonar, sediment acoustics, Natural Gamma, upward-looking ADCP). Numerous design improvements enhance safety and expand the application spectrum of the new system in significant ways. EM-detail mapping of the Galician shelf with METEOR (GALIOMAR III, 600 nm length of profile) February / March 2011 and in the Bay of Plenty Area (NZ) have already been granted; Cruise proposals for the southern Brazilian continental shelf, the Baltic Sea and the northwestern coast of New Zealand are in preparation.