Viscous magnetization of loess/palaeosol samples from Bulgaria

Abstract

The processes of acquisition of viscous remanence and its decay in zero magnetic field are studied for three sets of palaeosol and loess samples. A linear behaviour of VRM vs. log t minus is obtained for 10-10 4 min. to 30 days of acquisition experiments. Linear correlation between the obtained coefficients of viscous acquisition normalized to saturation magnetization (Sa/Js) or frequency dependent magnetic susceptibility (Sa/χfd%) and the ratio of susceptibility to saturation magnetization (χ/Js), suggests that ultra fine SP/SD grains are mainly involved in the process of viscous acquisition. Non-linear VRM vs. log t behaviour is observed during viscous decay in μ-metal shielded space, being most pronounced for the first 10 min. of the experiment. It is supposed that this phenomena is due to the presence of composite grains (core/shell structure), formed as a result of low-temperature oxidation. The latter increases towards older palaeosol units.

An investigation of the magnetic carriers and demagnetization characteristics of the Gulang loess section, northwestern Chinese Loess Plateau

“…Therefore, in unit L9, contributions to the NRM by neoformed SD/PSD particles are minimal, and coarse‐grained (coarse PSD/MD) magnetite particles are the main carriers of the DRM/pDRM. Coarse‐grained PSD/MD magnetite particles are very sensitive to VRM acquisition [ Jordanova et al ., ; Muxworthy and Williams , ; Yu and Tauxe , ], and therefore it is likely that a VRM, acquired during the Brunhes Chron, contributes significantly to the NRM of unit L9 and may even replace the original DRM/pDRM completely [cf. Deng , ; Jin and Liu , ].…”