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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 >High absolute paleointensity during a mid Miocene excursion of the Earth's magnetic field
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High absolute paleointensity during a mid Miocene excursion of the Earth's magnetic field

机译：地球磁场的中新世中期偏移过程中的绝对高古绝对强度

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摘要

A record of an excursion of the Earth's magnetic field was found in a ～14.3 Myr old lava sequence of the shield basalts from Gran Canaria (Canary Islands). The thermal and alternating field demagnetization of the samples from 14 subsequent lava flows revealed mainly single component magnetizations and sometimes minor viscous overprints. Four consecutive flows showed intermediate paleodirections which represent an excursion of the virtual geomagnetic pole (VGP) from the South pole towards the equator in the central Atlantic. Rock magnetic and microscopic analysis revealed high temperature oxidized titanomagnetites as the dominant carrier of remanence. On the basis of reversibility of thermomagnetic curves and limited variation of susceptibility during thermal demagnetization, we selected suitable samples for three slightly different Thellier-type paleointensity methods. The results show a minimum in paleointensity after the directional excursion with intensity values of ～9 μT. With the pole approaching the equator, values of ～27 μT are reached. The intensity at the beginning and at the end of the section is ～20 μT corresponding to a virtual dipole moment (VDM) of 6 * 10~(22) Am~2. The high intensities during the VGP excursion with a pole near the equator are explained by the same VDM.
机译：在大加那利岛（加那利群岛）的屏蔽玄武岩的〜14.3 Myr老熔岩序列中，发现了地球磁场偏移的记录。来自随后的14个熔岩流的样品的热场和交变场消磁显示出主要是单组分磁化，有时还有少量粘性套印。四次连续的流动显示出中间的古方向，代表着虚拟地磁极（VGP）从南极向大西洋中部的赤道偏移。岩石磁性和显微镜分析显示高温氧化钛磁铁矿是剩磁的主要载体。基于热磁曲线的可逆性和热退磁过程中磁化率的有限变化，我们为三种稍有不同的塞勒式古强度方法选择了合适的样品。结果表明，定向偏移后的古强度最小，强度值为〜9μT。当极点接近赤道时，达到〜27μT的值。截面起点和终点的强度约为20μT，对应于6 * 10〜（22）Am〜2的虚拟偶极矩（VDM）。相同的VDM解释了VGP在赤道附近有极点偏移时的高强度。

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