Paleointensity Estimates From the Pleistocene of Northern Israel: Implications for Hemispheric Asymmetry in the Time‐Averaged Field
Paleointensity Estimates From the Pleistocene of Northern Israel: Implications for Hemispheric Asymmetry in the Time‐Averaged Field
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DOI：
10.1029/2022gc010473
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发表时间：
2022-08
期刊：
影响因子：
3.7
通讯作者：
L. Tauxe;H. Asefaw;N. Behar;A. Koppers;R. Shaar
中科院分区：
文献类型：
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作者：
L. Tauxe;H. Asefaw;N. Behar;A. Koppers;R. Shaar
利用IZZI修正的Thellier - Thellier实验和严格的选择标准，在以色列北部的22个地点恢复了更新世（0.012-2.58 Ma）的古地磁轴向偶极矩（PADM）为62.2±30.6 ZAm2。使用相同的标准和年龄范围对来自南极洲、冰岛和夏威夷的可比研究的更新世数据进行重新分析，结果表明，以色列北部的数据平均略高于冰岛的数据（PADM = 53.8±23 ZAm2, n = 51个地点），甚至高于南极洲的平均值（PADM = 40.3±17.3 ZAm2, n = 42个地点）。此外，夏威夷钻探岩芯HSDP2的数据跨越了过去50万年（PADM = 76.7±21.3 ZAm2, n = 59个地点），高于以色列北部的数据。这些结果与从PINT数据库（www.pintdb.org）过滤的更新世结果相比表明，北半球中纬度地区的数据平均高于南半球的数据，也高于纬度高于60°N的数据。因此，在高纬度（南北）发现的较弱强度不能归因于时变偶极矩的时空采样不足或低质量数据。北半球中纬度地区的强磁场可能是由于地磁场中非轴偶极子项的长期存在，在不同经度的不同时间会出现强磁场。这一假设得到了全新世、100万年和500万年时间平均地磁场模型预测的不对称性的支持。
Twenty‐two sites, subjected to an IZZI‐modified Thellier‐Thellier experiment and strict selection criteria, recover a paleomagnetic axial dipole moment (PADM) of 62.2 ± 30.6 ZAm2 in Northern Israel over the Pleistocene (0.012–2.58 Ma). Pleistocene data from comparable studies from Antarctica, Iceland, and Hawaii, re‐analyzed using the same criteria and age range, show that the Northern Israeli data are on average slightly higher than those from Iceland (PADM = 53.8 ± 23 ZAm2, n = 51 sites) and even higher than the Antarctica average (PADM = 40.3 ± 17.3 ZAm2, n = 42 sites). Also, the data from the Hawaiian drill core, HSDP2, spanning the last half million years (PADM = 76.7 ± 21.3 ZAm2, n = 59 sites) are higher than those from Northern Israel. These results, when compared to Pleistocene results filtered from the PINT database (www.pintdb.org) suggest that data from the Northern hemisphere mid‐latitudes are on average higher than those from the southern hemisphere and than those from latitudes higher than 60°N. The weaker intensities found at high (northern and southern) latitudes therefore, cannot be attributed to inadequate spatiotemporal sampling of a time‐varying dipole moment or low quality data. The high fields in mid‐latitude northern hemisphere could result from long‐lived non‐axial dipole terms in the geomagnetic field with episodes of high field intensities occurring at different times in different longitudes. This hypothesis is supported by an asymmetry predicted from the Holocene, 100 kyr, and 5 million year time‐averaged geomagnetic field models.