The Origin of Magnetofossil Coercivity Components: Constraints From Coupled Experimental Observations and Micromagnetic Calculations

作者：Pengfei Xue, Liao Chang, Zhaowen Pei, R. J. Harrison · 发表于：Journal of Geophysical Research Solid Earth · 年份：2024 · DOI：10.1029/2023jb028501 · 被引用次数：5 · 研究领域：Geomagnetism and Paleomagnetism Studies、Geology and Paleoclimatology Research、Geological and Geochemical Analysis

Abstract Biogenic magnetite crystals produced by magnetotactic bacteria (MTB) and associated magnetofossils in sediments are characterized by variable morphologies, grain sizes, and chain structures. Magnetofossils are widely used in paleomagnetic and paleoenvironmental studies, but the complex magnetofossil shapes and particle arrangements significantly affect magnetic properties, hampering their magnetic detection and proxy interpretation. Here we perform coupled experimental and micromagnetic modeling analyses of typical magnetofossil‐rich sediments, where the effects of magnetofossil crystal forms and microstructures on magnetic properties can be quantitatively separated. Since the in situ magnetofossil chain structures in sediments remain poorly known, we compare results from magnetic measurements and micromagnetic simulations based on realistic magnetofossil shapes and grain size distributions. Our results suggest that bullet‐shaped magnetofossils certainly contribute to the biogenic hard (BH) coercivity component with a minor contribution from elongated prismatic particles, and collapsed equidimensional grains to the biogenic soft (BS) component. Micromagnetic simulations with different collapse models of bullet‐shaped magnetofossils produce variable FORC (first‐order reversal curve) central‐ridge contributions with similar coercivity distributions. Sensitivity test suggests that samples containing different forms of magnetofossils can produce the BH coercivity compone...