Paleomagnetic evidence for fossil biogenic magnetite in western Crete
Paleomagnetic evidence for fossil biogenic magnetite in western Crete
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DOI：
10.1016/0012-821x(82)90140-6
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发表时间：
1982-07
影响因子：
5.3
通讯作者：
J. Kirschvink
中科院分区：
文献类型：
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作者：
J. Kirschvink
先前的古地磁研究表明，在两次连续的地磁转换期间，保存在克里特岛西部中新世海洋粘土中的细粒磁铁矿的浓度下降，尽管这种效应的机制尚不清楚。趋磁细菌的磁铁矿沉淀提供了一个简单的解释，这种减少。在反转期间降低的场强将使具有细胞内磁铁矿的竞争优势受到限制，并且如果细菌要在地磁场中保持相同的排列，则将迫使细菌沉淀相应更多的磁铁矿。他们这样做的能力受到几个磁物理约束的限制，这些约束应该起到减少磁铁矿沉淀细胞数量的作用，特别是在小于目前水平约12%的磁场中。这将导致沉积物中细菌数量的供应减少。完整的趋磁细菌化石的恢复可能会导致一种新的方法来估计沉积岩的古强度。
Previous paleomagnetic research has shown that the concentration of fine-grained magnetite preserved in Miocene marine clays of western Crete drops during two successive geomagnetic transitions, although the mechanism responsible for this effect was not known. Magnetite precipitation by magnetotactic bacteria offers a straightforward explanation for this decrease. Reduced field strengths during a reversal will strain the competitive advantage of having intracellular magnetite and will force bacteria to precipitate correspondingly more magnetite if they are to maintain the same alignment in the geomagnetic field. Their ability to do this is limited by several magnetophysical constraints which should act to reduce the numbers of magnetite-precipitating cells, particularly in fields of less than about 12% of the present level. This would lead to a decrease in the supply of bacterial magnitude to the sediments. Recovery of intact magnetotactic bacterial fossils may lead to a new method for estimating paleointensities from sedimentary rocks.