Today's paleomagnetic and magnetic proxy studies involve processing of large sample collections while simultaneously demanding high quality data and high reproducibility. Here we describe a fully automated interface based on a commercial horizontal pass-through ''2G'' DC-SQUID magnetometer. This system is operational at the universities of Bremen (Germany) and Utrecht (Netherlands) since 1998 and 2006, respectively, while a system is currently being built at NGU Trondheim (Norway). The magnetometers are equipped with ''in-line'' alternating field (AF) demagnetization, a direct-current bias field coil along the coaxial AF demagnetization coil for the acquisition of anhysteretic remanent magnetization (ARM) and a long pulse-field coil for the acquisition of isothermal remanent magnetization (IRM). Samples are contained in dedicated low magnetization perspex holders that are manipulated by a pneumatic pick-and-place-unit. Upon desire samples can be measured in several positions considerably enhancing data quality in particular for magnetically weak samples. In the Bremen system, the peak of the IRM pulse fields is actively measured which reduces the discrepancy between the set field and the field that is actually applied. Techniques for quantifying and removing gyroremanent overprints and for measuring the viscosity of IRM further extend the range of applications of the system. Typically c. 300 paleomagnetic samples can be AF demagnetized per week (15 levels) in the three-position protocol. The versatility of the system is illustrated by several examples of paleomagnetic and rock magnetic data processing.

Distribution, accumulation, and diagenesis of surficial sediments in coastal and continental shelf systems follow complex chains of localized processes and form deposits of great spatial variability. Given the environmental and economic relevance of ocean margins, there is growing need for innovative geophysical exploration methods to characterize seafloor sediments by more than acoustic properties. A newly conceptualized benthic profiling and data processing approach based on controlled-source electromagnetic (CSEM) imaging permits to coevally quantify the magnetic susceptibility and the electric conductivity of shallow marine deposits. The two physical properties differ fundamentally insofar as magnetic susceptibility mostly assesses solid particle characteristics such as terrigenous or iron mineral content, redox state, and contamination level, while electric conductivity primarily relates to the fluid-filled pore space and detects salinity, porosity, and grain-size variations. We develop and validate a layered half-space inversion algorithm for submarine multifrequency CSEM with concentric sensor configuration.Guided by results of modeling, we modified a commercial land CSEM sensor for submarine application, which was mounted into a nonconductive and nonmagnetic bottom-towed sled. This benthic EM profiler Neridis II achieves 25 soundings/ second at 3-4 knots over continuous profiles of up to a hundred kilometers. Magnetic susceptibility is determined from the 75 Hz in-phase response (90% signal originates from the top 50 cm), while electric conductivity is derived from the 5 kHz out-of-phase (quadrature) component (90% signal from the top 92 cm). Exemplary survey data from the north-west Iberian margin underline the excellent sensitivity, functionality, and robustness of the system in littoral (∼0-50 m) and neritic (∼50-300 m) environments. Susceptibility versus porosity crossplots successfully identify known lithofacies units and their transitions. All presently available data indicate an eminent potential of CSEM profiling for assessing the complex distribution of shallow marine surficial sediments and for revealing climatic, hydrodynamic, diagenetic, and anthropogenic factors governing their formation.

This study focuses on seafloor methane seep sites and their distribution in the northwestern part of the German North Sea. Methane seepage is a common phenomenon along marine shelves and known to occur in the North Sea, but proof of their existence was lacking in the study area. Using a ship-based multibeam echosounder we detected a minimum of 166 flares that are indicative for free gas releases from the seafloor in the German “Entenschnabel” area, which are not related to morphologic expressions at the seafloor. However, a group of small depressions was detected lacking water column anomalies but with indications of dissolved fluid release. Spatial analysis revealed that flares were not randomly distributed but show a relation to locations of subsurface salt diapirs. More than 60% of all flares were found in the vicinity of the salt diapir “Berta”. Dissolved methane concentrations of ∼100 nM in bottom waters were ten times the background value in the “Entenschnabel” area (CH4 < 10 nM), supporting the finding of enhanced seepage activity in this part of our study area. Furthermore, locations of flares were often related to acoustic blanking and high amplitude reflections in sediment profiler echograms, most prominently observed at location Berta. These hydroacoustic signatures are interpreted to result from increased free gas concentrations in the sediments. Electromagnetic seabed mapping depicts local sediment conductivity anomalies below a flare cluster at Berta, which can be explained by small amounts of free gas in the sediment. In our area of interest, ten abandoned well sites were included in our mapping campaign, but flare observations were spatially not related to these wells. Naturally seeping methane is presumably transported to the seafloor along sub-vertical faults, which have formed concurrently to the updoming salt. Due to the shallow water depths of 30 to 50 m in the study area, flares were observed to reach close to the sea surface and a slight oversaturation of surface waters with methane in the flare-rich northeastern part of the working area indicates that part of the released methane through seepage may contribute to the atmospheric inventory.

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