The sediment series recovered during MERIAN Cruise MSM 39 by gravity coring were subject to routine magnetic susceptibility loggin, which was usually performed on the closed full cores. The magnetic volume susceptibility κ of marine sediment is primarily determined by its ferrimagnetic mineral content; paramagnetic matrix components such as clays are of minor importance. As a dimensionless quantity, κ may vary from an absolute minimum value of -15∙10-6 for diamagnetic minerals (such as pure carbonate or silicate) to a maximum of some 10⋅10-3 for sediments rich in ferrimagnetic (titano-)magnetite (of as magmatic sources). Enhanced susceptibilities indicate higher concentrations of lithogenic components (here mainly magmatic-sourced, ice-rafted materials) versus diamagnetic matrix materials (calcite, quartz, water etc.). This relation is very useful for correlating sedimentary sequences deposited under similar global or regional conditions.
The GEOTEK core logger is mounted with a commercial BARTINGTON M.S.2 susceptibility meter with a 140 mm loop sensor. Due to the sensor's size, its sensitivity extends over a core interval of about 8 cm (half-width). Consequently, sharp susceptibility changes will appear smoothed in the κ core log and thin layers such as fine ice rafted debris layers cannot be appropriately resolved. In order to make an accurate end correction at the base of each segment and to assess the drift of the susceptibility meter, a spacer cylinder of 29.5 cm length was placed between each core segment during the measurement procedure. The measurements taken at the center of the spacer was used to assess and compensate the instrumental temperature drift. During post-processing all data related to void sections were removed to provide a continuous composite core log. The top and bottom ends were mirror-corrected. The systematic decline of the susceptibility signal between segment boundaries was recovered by summing the overlapping tail data leading to loss-free data sets.
