Paleomagnetic study of Plio-Pleistocene sediments in the concentrated deformation zone along the eastern margin of the Japan Sea
Paleomagnetic study of Plio-Pleistocene sediments in the concentrated deformation zone along the eastern margin of the Japan Sea
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DOI：
10.1016/j.quaint.2015.05.022
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发表时间：
2014-12
影响因子：
2.2
通讯作者：
H. Hoshi;K. Yamada
中科院分区：
文献类型：
--
作者：
H. Hoshi;K. Yamada
本文给出了欧亚大陆东部边缘沿着会聚板块边界区一集中变形带的古地磁结果。我们采样了日本本州东北部Sasaoka组（厚约750 m）的晚上新世-早更新世凝灰岩和碎屑沉积物，以测试日本海东缘沿着CDZ内的晚上新世-第四纪地壳变形是否伴随着绕垂直轴的旋转。岩石磁学实验表明，细凝灰岩中的磁性载体主要是磁铁矿，细砂岩中的磁性载体主要是硫化铁。折叠前的特征rebinding磁化证实了使用积极的自助折叠测试。我们获得了21个可接受的站点平均特征方向，包括我们的初步发表的结果，并涵盖了从约。2.7~ 1.7Ma。一个更新的年龄-深度模型，这使我们能够对关键的互层凝灰岩床（火山岩）进行数值年龄估计。一个积极的褶皱测试也表明，五条向斜开始发展后，1.7马，这意味着褶皱开始晚上新世地壳缩短在本州东北部的启动后很久。100%展开后，总体平均方向（D= 359.7°，I= 54.9°，α95= 6.7°）与地心轴向偶极场方向没有区别，表明研究区最突出的构造单元--五城向斜的发育没有垂直轴旋转。我们的研究结果与上新世更新世的方向报告从其他地区的比较显示，没有古地磁检测旋转或邻近的CDZ，除了在本州中部的走滑断层附近的本地旋转。
Paleomagnetic results are presented for a concentrated deformation zone (CDZ) in a convergent plate boundary region along the eastern Eurasian margin. We sampled late Pliocene–early Pleistocene tuffs and clastic sediments of the Sasaoka Formation (∼750 m thick) in northeastern Honshu, Japan, to test whether the late Pliocene–Quaternary crustal deformation within the CDZ along the eastern margin of the Japan Sea was accompanied by rotation about a vertical axis. Rock magnetic experiments suggest that the principal magnetic carrier is magnetite in the fine tuffs, and magnetic iron sulfide in the fine sandstones. Pre-folding characteristic remanent magnetization was confirmed using a positive bootstrap fold test. We obtained 21 acceptable site-mean characteristic directions that include our preliminary published results, and which cover an interval from ca. 2.7 to 1.7 Ma on the basis of magnetostratigraphic correlations. An updated age–depth model is given, and this allowed us to make numerical age estimates for key interbedded tuff beds (tephras). A positive fold test also suggests that the Gojome syncline began to develop after 1.7 Ma, which means the folding began long after the initiation of late Pliocene crustal shortening in northeastern Honshu. After 100% unfolding, the overall mean direction (D= 359.7°,I= 54.9°,α95= 6.7°) is indistinguishable from the geocentric axial dipole field direction, indicating that the Gojome syncline, the most prominent structural element in the study area, developed without vertical-axis rotation. A comparison of our results with Plio-Pleistocene directions reported from other areas reveals no paleomagnetically detectable rotation in or adjacent to the CDZ, except for local rotation near strike-slip faults in central Honshu.