GEOMAGNETIC PALEOINTENSITIES FROM RADIOCARBON-DATED LAVA FLOWS ON HAWAII AND QUESTION OF PACIFIC NONDIPOLE LOW
GEOMAGNETIC PALEOINTENSITIES FROM RADIOCARBON-DATED LAVA FLOWS ON HAWAII AND QUESTION OF PACIFIC NONDIPOLE LOW
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DOI：
10.1029/jb083ib04p01740
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发表时间：
1978-01-01
影响因子：
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通讯作者：
MANKINEN, EA
中科院分区：
文献类型：
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作者：
COE, RS;GROMME, S;MANKINEN, EA
在夏威夷岛上的9个玄武岩熔岩流的放射性碳年龄已经公布;年龄范围从2600年到稍早于17，900年B. P.通过使用Thelliers的方法在真空中，地磁古强度值从八个熔岩获得;第九个被证明是不合适的。最年轻的四个水流（2600-4600 aB. P.）产生的虚拟偶极矩（VDM）比V. Bucha从古地磁数据中获得的那些时间的全球值大20%至两倍以上。八个熔岩的虚拟地磁极分散度为15.5°，明显大于夏威夷较老熔岩流的平均值。这些结果与历史磁场在该地区的夏威夷，其中长期变化和非偶极子分量是非常低的。在大约10，000年B. P.，测得的VDM与长期全球平均值没有很大差异，但与Bucha平均曲线的平滑外推有很大差异。在大约18，000年B. P.，测得的VDM非常低，并且与夏威夷纬度的异常浅的古地磁倾斜有关。这些新的古强度和古方向的数据强烈表明，相当大的非偶极地磁场存在于附近的夏威夷在不同的时间在全新世时期，也许更早。
Radiocarbon ages have been published for nine basaltic lava flows on the island of Hawaii; the ages range from 2600 to somewhat older than 17,900 years B.P. By using the Thelliers' method in vacuum, geomagnetic paleointensity values were obtained from eight of the lavas; the ninth proved unsuitable. The paleointensities for the four youngest flows (2600–4600 years B.P.) yield virtual dipole moments (VDM's) that are 20% greater to more than twice the worldwide values for those times obtained by V. Bucha from archeomagnetic data. The dispersion of virtual geomagnetic poles for the eight lavas is 15.5°, appreciably larger than the average for older lava flows on Hawaii. These results contrast with the historic magnetic field in the region of Hawaii, in which both secular variation and nondipole components are very low. At about 10,000 years B.P. the measured VDM is not very different from the long‐term worldwide average but differs considerably from a smooth extrapolation of Bucha's average curve. At about 18,000 years B.P. the measured VDM is very low and is associated with an unusually shallow paleomagnetic inclination for the latitude of Hawaii. These new paleointensity and paleodirectional data strongly suggest that sizable nondipole geomagnetic fields have existed in the vicinity of Hawaii at various times during the Holocene epoch and perhaps earlier.