The Magnetization of Marine Sediments: A Search for Fossil Biogenic Magnetite

在过去的20年里，自然恢复磁化进行了 被海洋沉积物和沉积岩广泛用于 监测地磁场的历史，并限制 地壳板块 但是磁性矿物的起源 观测到的反射磁化现在才被解决。 最近的工作 表明，磁铁矿晶体沉淀的趋磁 细菌和可能其他趋磁微生物贡献了 大部分海洋沉积物磁化。 现在的技术 来提取这些粒子并通过传输来识别它们 电镜完整的“磁化石”链被发现在一些 DSDP沉积物和其他生物成因磁铁矿已经从 早寒武世石灰岩。细菌磁化石的继续研究 可能有助于更好地了解细颗粒的过程， 成岩作用以及岩石磁效应的直接测量 粒子间相互作用细菌磁化石也可能提供 古地磁强度独立测量法 海洋沉积物记录的磁场，也可能有用 初级剩磁的指示器。 磁铁矿沉淀 细菌似乎是一个需要氧气的过程，因此， 它们在时间和空间上的分布可能会限制 地球表面自由氧的历史

In the past two decades, natural remanent magnetization carried by marine sediments and sedimentary rocks has been used extensively to monitor the history of the geomagnetic field and to constrain motion of crustal plates. But the origin of the magnetic minerals contributing to observed remanent magnetization is only now being resolved. Recent work suggests that crystals of magnetite precipitated by magnetotactic bacteria and perhaps other magnetotactic microorganisms contribute a large fraction to magnetization of marine sediments. Techniques now exist to extract these particles and identify them with transmission electron microscopy. Intact 'magnetofossil' chains are found in some DSDP sediments, and other biogenic magnetites have been extracted from Early Cambrian limestone. Continued study of bacterial magnetofossils may contribute to a better understanding of the process of fine-particle diagenesis as well as direct measurements of rock-magnetic effects of interparticle interaction. Bacterial magnetofossils may also provide an independent method of measuring the paleointensity of the geomagnetic field as recorded by marine sediments, and might also be useful indicators of primary magnetic remanence. Precipitation of magnetite in bacteria appears to be an oxygen-requiring process, so knowledge of their distribution in time and space may place constraints on the history of free oxygen at the Earth's surface.