GP12A-06:
Insight into the mechanism of natural remanent magnetization of magnetotactic-bacteria-bearing freshwater sediments
Monday, 15 December 2014: 11:35 AM
Xiangyu Zhao1, Ramon Egli2, Kuang He1, Stuart A Gilder1, Qingsong Liu3 and Nikolai Petersen1, (1)Ludwig Maximilian University of Munich, Munich, Germany, (2)Ludwig-Maximilians Universität, Wien, Austria, (3)IGG Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
Abstract:
It is well known that magnetotactic bacteria (MTB) synthesize chains of single domain (SD) magnetite, called magnetosome or magnetofossils depending whether bacteria are alive or dead, which is considered as an ideal recording material of paleomagnetic information in natural environments. Recent advances in rock magnetic techniques, magnetofossils have been recognized to be the main remanence carriers in many types of marine and lake sediments. However, the mechanism of acquisition and preservation of paleomagnetic information by magnetofossils is poorly known. Here we present first results of redeposition experiments performed with magnetofossil-rich freshwater sediments. Coercivity analysis and central ridge on FORC diagrams confirm the predominance of magnetofossil. Different exposures to a magnetic field during and after deposition are used to investigate the carriers of the remanence. Inclination shallowing is noticed and our preliminary results confirm the key role of flocculation, porosity, and timing during sedimentary NRM acquisition.
