Susceptibility measured on 18 sediment cores from METEOR cruise M134/1
Sediment magnetic properties are determined by the speciation, concentration and grain‐size range of the sedimentary iron mineral assemblage and mirror both, sediment lithology and diagenesis. As geochemical redox reactions involving iron, methane and other types of organic matter were a major issue...
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| Format: | Dataset |
| Language: | English |
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PANGAEA
2020
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| Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.914649 https://doi.org/10.1594/PANGAEA.914649 |
| Summary: | Sediment magnetic properties are determined by the speciation, concentration and grain‐size range of the sedimentary iron mineral assemblage and mirror both, sediment lithology and diagenesis. As geochemical redox reactions involving iron, methane and other types of organic matter were a major issue of Cruise M134/1 to South Georgia Island, magnetic methodology has been routinely applied to all collected sediment series. All opened GC and DAPC cores were investigated for changes in magnetic susceptibility at 2 cm resolution, using a hand‐bench suitable for horizontal full‐ or half‐core logging. Magnetic volume susceptibility κ is the most commonly measured rock magnetic parameter in geoscience and describes how strongly a material is magnetized by a small and alternating external magnetic field (κ = dM/dH with volume magnetization M and magnetizing field H). κ primarily reflects the concentration of lithogenic or authigenic ferrimagnetic iron minerals while paramagnetic minerals such as iron‐bearing silicates have lesser influence except in Fe oxide depleted sediments. Diamagnetic matrix mineral (calcite, quartz, opal) and pore water content (i.e. porosity) all dilute the magnetic mineral fraction and reduce the bulk magnetic volume susceptibility accordingly. On this cruise, magnetic susceptibility was exceptionally measured on a self‐built, hand‐operated roller bench onto which a new BARTINGTON 140 mm loop sensor connected to a MS‐3 control unit was mounted (cycling time set to 5 sec). The sensor's sensitivity extends over an interval (half‐width) of ~8 cm. Consequently, sharp susceptibility changes appear smoothed in the core log and thin, magnetically contrasting layers are not appropriately resolved. Each segment was separately logged at 2 cm intervals with 10 cm extensions to both sides. Start and end data were used to assess and compensate the instrumental temperature drift. A volume correction for core diameter and full or split core data was applied. The systematic decline of the susceptibility signal ... |
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