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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 >Matuyama–Brunhes reversal and Kamikatsura event on Maui: paleomagnetic directions, ~(40)Ar/~(39)Ar ages and implications
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Matuyama–Brunhes reversal and Kamikatsura event on Maui: paleomagnetic directions, ~(40)Ar/~(39)Ar ages and implications

机译：毛伊岛的Matuyama–布鲁什逆转和Kamikatsura事件：古磁方向，〜（40）Ar /〜（39）Ar年龄及其影响

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摘要

Eighty-nine basaltic lava flows from the northwest wall of Haleakala caldera preserve a concatenated paleomagnetic record of portions of the Matuyama–Brunhes (M–B) reversal and the preceding Kamikatsura event as well as secular variation of the full-polarity reversed and normal geomagnetic field. They provide the most detailed volcanic record to date of the M–B transition. The 24 flows in the transition zone show for the first time transitional virtual geomagnetic poles (VGPs) that move from reverse to normal along the Americas, concluding with an oscillation in the Pacific Ocean to a cluster of VGPs east of New Zealand and back finally to stable polarity in the north polar region. All but one of the 16 Kamikatsura VGPs cluster in central South America. The full-polarity flows, with ~(40)Ar/~(39)Ar ages spanning a total of 680 kyr, pass a reversal test and give an average VGP insignificantly different from the rotation axis, with standard deviation consistent with that for other 0–5 Ma lava flows of similar latitude. Precise ~(40)Ar/~(39)Ar dating consisting of 31 incremental heating experiments on 12 transitional flows yields weighted mean ages of 775.6±1.9 and 900.3±4.7 ka for the M–B and Kamikatsura transitional flows, respectively. This Matuyama–Brunhes age is ～16 kyr younger than ages for M–B flows from the Canary Islands, Tahiti and Chile that were dated using exactly the same techniques and standards, suggesting that this polarity transition may have taken considerably longer to complete and been more complex than is generally believed for reversals.
机译：来自哈雷阿卡拉火山口西北壁的八十九个玄武岩熔岩流保持了部分Matuyama–Brunhes（M–B）反转和前Kamikatsura事件的级联古磁记录，以及全极性反转和正常地磁的长期变化领域。它们提供了迄今为止M–B转换的最详细的火山记录。过渡带中的24个流首次显示了虚拟虚拟地磁极（VGP），该虚拟地磁极沿美洲从反向移动到法线，最后在太平洋中振荡，向新西兰东部的VGP集群，最后返回到在北极地区极性稳定。南美洲中部的16个Kamikatsura VGP集群中只有一个集群。 〜（40）Ar /〜（39）Ar年龄跨度总计680 kyr的全极性流通过反向测试，得出的平均VGP与旋转轴无显着差异，标准偏差与其他相似纬度的0-5 Ma熔岩流。精确的〜（40）Ar /〜（39）Ar测年包括12个过渡流的31个增量加热实验，分别为M–B和Kamikatsura过渡流的加权平均年龄分别为775.6±1.9和900.3±4.7 ka。这个Matuyama–Brunhes年龄比使用完全相同的技术和标准测得的来自加那利群岛，塔希提岛和智利的M–B流年龄年轻约16岁，这表明这种极性转换可能花费了更长的时间才能完成并完成。比通常认为的逆转更为复杂。

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