Paleomagnetic of ODP Leg 125 holes

During Leg 125, scientists drilled three holes (782A, 784A, and 786A) in the Izu-Bonin forearc near 31° N that had sufficient recovery to obtain paleoinclination data. A total of 169 paleomagnetic samples were analyzed using either alternating field or continuous thermal demagnetization. Unfortunately, poor recovery, complex magnetization in the older sediments, and dipping beds prevented us from obtaining results that were older than middle Miocene. However, six reliable data points (one Pleistocene, three Pliocene, and two Miocene) were obtained. These data agree with past work from around the Philippine Sea plate, which suggest about 20° of northward translation since the Eocene. This paleomagnetic data set can be used to help constrain models for the origin and history of the Philippine Sea plate.

在第125钻探航次期间，科研人员于北纬31°附近的伊豆-小笠原弧前（Izu-Bonin forearc）钻取了782A、784A与786A共3个钻孔，上述钻孔的取芯量充足，可获取古倾角数据（paleoinclination data）。研究团队共对169件古地磁样品（paleomagnetic samples）开展分析，测试方法分别采用交变退磁（alternating field）与连续热退磁（continuous thermal demagnetization）。遗憾的是，受取芯效果不佳、老沉积物内磁化结构复杂以及地层倾斜等因素影响，研究人员未能获取中中新世（middle Miocene）之前的古地磁结果。但最终仍获得6组可靠数据点，其中更新世（Pleistocene）1组、上新世（Pliocene）3组、中新世（Miocene）2组。该数据集与菲律宾海板块（Philippine Sea plate）周边既往研究成果一致，相关研究均表明自始新世（Eocene）以来，该板块向北平移了约20°。这套古地磁数据集可用于约束菲律宾海板块的成因与演化历史相关模型。