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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Middle Cambrian high magnetic reversal frequency (Kulumbe River section, northwestern Siberia) and reversal behaviour during the Early Palaeozoic
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Middle Cambrian high magnetic reversal frequency (Kulumbe River section, northwestern Siberia) and reversal behaviour during the Early Palaeozoic

机译：中寒武纪高磁逆转频率（西伯利亚西北部的库卢姆贝河段）和早古生代期间的逆转行为

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摘要

We present a magnetostratigraphic study of Middle Cambrian sediments along the Kulumbe River (northwestern Siberia). The deposits are ～850 m thick and lie within the Mayan stage as constrained by trilobite fossils. Palaeomagnetic analyses reveal two magnetic components. The first component, parallel to the direction of the present day field at the site, is isolated in the low to middle temperature range. A high temperature component (HTC) is then isolated up to 580 or 680 ℃, carried either by magnetite and/or by hematite. The HTC defines a sequence of 28 magnetic polarity intervals, some of them being defined by only one sample. Considering that the studied section has a duration of ～5 Myr, we propose that the magnetic reversal frequency was high (～4-6 reversals per Myr) during part of the Middle Cambrian, among the highest values known within the Phanerozoic. The reversal frequency may have been roughly similar during the Lower Cambrian. We further suggest a drastic decrease of the magnetic reversal frequency between the Lower-Middle Cambrian and the end of the Tremadoc (Ordovician) when a superchron probably occurred. However, this behaviour is still challenged by other scenarios which depend on the chosen Early Palaeozoic time scale and on the reliability of some magnetostratigraphic data.
机译：我们介绍了沿库伦贝河（西伯利亚西北部）中寒武纪沉积物的地磁地层学研究。该矿床厚约850 m，位于三叶虫化石的约束下处于玛雅阶段。古磁性分析揭示了两个磁性成分。与现场当前磁场方向平行的第一部分在中低温度范围内被隔离。然后，分离出由磁铁矿和/或赤铁矿携带的高达580或680℃的高温成分（HTC）。 HTC定义了28个磁极性间隔的序列，其中一些仅由一个样本定义。考虑到所研究的断面的持续时间为〜5 Myr，我们建议在中寒武纪的部分期间，磁性反转频率较高（每个Myr〜4-6个反转），这是在生代时代已知的最高值。在下寒武纪期间，反转频率可能大致相似。我们还建议，当可能发生超同步时，下中寒武纪与特雷莫多克（奥陶纪）末端之间的磁反转频率急剧下降。但是，这种行为仍然受到其他情况的挑战，这些情况取决于所选择的早期古生代时标和某些地磁地层数据的可靠性。

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