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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 >Geomagnetic paleointensity deduced for the last 300 kyr from Unzen Volcano, Japan, and the dipolar nature of the Iceland Basin excursion
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Geomagnetic paleointensity deduced for the last 300 kyr from Unzen Volcano, Japan, and the dipolar nature of the Iceland Basin excursion

机译：从日本云仙火山最后300年推断的地磁古强度和冰岛盆地漂移的偶极性质

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We have conducted paleointensity measurements of lavas and pyroclastic flows from Unzen Volcano, Japan. They have been shown in a previous study to contain a record of Brunhes Chron secular variation, with one flow recording a transitional direction (Senbongi geomagnetic excursion; 191 +/- 17 ka). Various rock magnetic analyses indicate that the main magnetic carriers of samples are Ti-poor titanomagnetites, which have mixtures of single domain (SD) (and/or pseudo-SD) and multi-domain grain sizes. The low-temperature demagnetization (LTD)-double heating test (DHT) Shaw method yielded 209 successful results from 56 sites, giving 27 acceptable site-mean paleointensities for the past 5-300 kyr. When excluding the Senbongi excursion data and two other data points, the data give an average virtual dipole moment (VDM) of 7.69 x 10(22) A m(2) with a standard deviation of 2.51 x 10(22) A m(2) (N =24). This is consistent with the selected 80 site-mean Thellier paleointensity data from the latest paleointensity database, with an average VDM of 7.64 x 10(22) A m(2) and a standard deviation of 2.56 x 10(22) A m(2). Paleointensity measurements on samples that record the Senbongi excursion, which is claimed to correlate with the Iceland Basin excursion, provide a value of 7.74-9.37 mu T using the LTD-DHT Shaw method. This corresponds to an average (standard deviation) VDM of 2.19 x 10(22) A m(2) (0.21 x 10(22) A m(2)). When calibrating sedimentary records that capture the Iceland Basin excursion by averaging the LTD-DHT Shaw VDMs obtained from the pre- and post-excursional period, the records give consistent VDM values with the volcanic (Senbongi) record during the excursion. This indicates that variation of the geomagnetic field direction and intensity during the Iceland Basin excursion can be well represented by a simple dipolar variation.
机译：我们对日本云仙火山的熔岩和火山碎屑流进行了古强度测量。在先前的研究中已显示它们包含Brunhes Chron长期变化的记录，其中一个流记录了过渡方向（Senbongi地磁偏移; 191 +/- 17 ka）。各种岩石磁性分析表明，样品的主要磁性载体是贫钛的钛磁铁矿，它们具有单畴（SD）（和/或伪SD）和多畴晶粒尺寸的混合物。低温退磁（LTD）-双加热试验（DHT）肖氏法从56个部位获得209个成功结果，在过去的5-300年中给出了27个可接受的部位-平均古强度。当排除Senbongi偏移数据和其他两个数据点时，数据给出的平均虚拟偶极矩（VDM）为7.69 x 10（22）A m（2），标准偏差为2.51 x 10（22）A m（2） ）（N = 24）。这与从最新的古强度数据库中选择的80个站点均值Thellier古强度数据一致，平均VDM为7.64 x 10（22）A m（2），标准偏差为2.56 x 10（22）A m（2） ）。记录Senbongi偏移的样品的古强度测量值据称与冰岛盆地的偏移相关，使用LTD-DHT Shaw方法可提供7.74-9.37 mu T的值。这对应于2.19 x 10（22）A m（2）（0.21 x 10（22）A m（2））的平均值（标准偏差）VDM。当校准从偏移前后获得的LTD-DHT Shaw VDM的平均值来记录捕获冰岛盆地偏移的沉积记录时，记录显示偏移期间的VDM值与火山记录（Senbongi）一致。这表明在冰岛盆地漂移期间地磁场方向和强度的变化可以用简单的偶极变化很好地表示。

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