[S-EM15] Geomagnetism, paleomagnetism and rock magnetism

[SEM15-P04] Properties of remanent magnetization carried by magnetotactic bacteria Magnetospirillum magnetotacticum MS-1 in the early stages of sediment formation – system with reduced efficiency of NRM acquisition

*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 Natural Remanent Magnetization (NRM). The NRM is carried not only by detrital magnetic grains but also by biogenic magnetic grains originated from magnetotactic bacteria. To clarify the characters of NRM in sediments carried by biogenic magnetite we have simulated the very early process of sediment formation by solidifying agarose including magnetotactic bacteria Magnetospirillum magnetotacticum MS-1 (here after, MS-1) cultured in laboratory.

The properties of the remanent magnetization of agarose samples including MS-1 were reported in Masaoka et al. (2018JpGU, 2018SGEPSS, 2019JpGU, 2019SGEPSS, 2020JpGU, 2021JpGU, 2021SGEPSS). However, there was a large difference between the prepared samples and real marine sediments; the MS-1 cells were very efficiently oriented to the applied magnetic field. In this study, we prepared samples with various agarose temperature at the start of magnetic field application and various applied field strength in order to investigate the characteristics of NRM acquired under conditions where orientation was suppressed. We will report and discuss the results in the presentation.