Dipole strength and variation of the time-averaged reversing and nonreversing geodynamo based on Thellier analyses of single plagioclase crystals
Dipole strength and variation of the time-averaged reversing and nonreversing geodynamo based on Thellier analyses of single plagioclase crystals
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DOI：
10.1029/2005jb003970
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发表时间：
2005-11
影响因子：
--
通讯作者：
J. Tarduno;R. Cottrell
中科院分区：
文献类型：
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作者：
J. Tarduno;R. Cottrell
从熔岩中分离出来的单个斜长石晶体可以包含微小的磁包裹体，这些包裹体忠实地记录了地磁场，而硅酸盐宿主则限制了自然和实验诱导的蚀变。在这里，我们使用斜长石晶体的古强度分析来研究跨越过去200 Myr的三个特征地球动力机制：古近纪的中等反转频率区间，白垩纪正极性超时的非反转场，以及晚侏罗世的非常高的反转发生时期。反转速率和强度之间存在反比关系。此外，时间平均换向场的强度比非换向场的强度变化更大。这些观测结果与活跃的下地幔一致，在数千万年的时间尺度上塑造了核心-地幔边界的热通量和地球动力的效率。
[1] Single plagioclase crystals separated from lavas can contain minute magnetic inclusions that faithfully record the geomagnetic field, while the silicate host limits natural and experimentally induced alteration. Here we use paleointensity analyses of plagioclase crystals to examine three characteristic geodynamo regimes spanning the last 200 Myr: an interval of moderate reversal frequency during the Paleogene, the nonreversing field of the Cretaceous Normal Polarity Superchron, and a period of very high reversal occurrence during the Late Jurassic. An inverse relationship between reversal rate and intensity is supported. Furthermore, the strength of the time-averaged reversing field is more variable than that of the nonreversing field. These observations are consistent with an active lower mantle, shaping core-mantle boundary heat flux and efficiency of the geodynamo on timescales of tens of millions of years.