[S-EM13] Geomagnetism, paleomagnetism and rock magnetism

[SEM13-08] Examination of the properties of remanent magnetization carried by magnetotactic bacteria in the early stages of sediment formation; example of mixed system with magnetic particles of inorganic origin

*Kohei Masaoka¹, Yuki Morono², Naotaka Tomioka², Go-Ichiro Uramoto³, Yuhji Yamamoto³, Masao Ohno¹ (1.Kyushu University, 2.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, 3.Kochi University)

Variation of the past geomagnetic field is recorded in marine sediments as a fossil magnetization, called natural remanent magnetization (NRM). The carrier of the NRM is not only detrital magnetic grains but also biogenic magnetic grains originated from magnetotactic bacteria. To investigate characters of NRM carried by biogenic magnetic grains we have cultured the magnetotactic bacteria Magnetospirillum magnetotacticum MS-1 (here under, MS-1) in laboratory. We made samples using them for remanent magnetization measurements to simulate the very early process of sediment formation.
Properties of the remanent magnetization carried by the samples used only MS-1 cells have been presented in Masaoka et al (2020JpGU). However, there is a difference from actual sediments containing magnetic particles of inorganic origin, and it is not possible to make a simple comparison. Various experiments and magnetic analysis were performed to fill this difference: we have made two types of samples containing reagent magnetite and MS-1 cells, and MS-1 cells crushed by ultrasonic. We will report and discuss the results.