Magnetic measurements on ODP holes 178-1095A, 178-1095B and 178-1101A

We have determined the azimuth of bottom-current flow in drift deposit sediments recovered at ODP Sites 1095 and 1101, Antarctic Peninsula, using paleomagnetic reorientation of anisotropy of magnetic susceptibility (AMS) ellipsoids. A total of 38 cores from the two ODP sites have been measured, providing spatial and directional information on the physical record of the ACC (Antarctic Circumpolar Current) in the Plio-Pleistocene. Declination and inclination of the paleomagnetic vector of each core segment were used to reorient the AMS principal axes to the geographic coordinates. The cores were reoriented using the measured direction of the characteristic remanent magnetization (ChRM) with respect to a common reference line for the core, from which we are able to determine the orientation of the paleocurrent flow for Sites 1095 (Drift 7) and 1101 (Drift 4) relative to the geographic coordinates. Both sites have paleocurrent directions trending ~NW–SE, which in the former locality are parallel to a sediment wave field. Our study shows that a combination of magnetic fabric analysis and paleomagnetism allows deep-sea sedimentary fabric to be used as a long-term proxy of bottom-current flow history.本研究通过对磁化率各向异性（anisotropy of magnetic susceptibility, AMS）椭球体进行古地磁定向，确定了南极半岛大洋钻探计划（Ocean Drilling Program, ODP）1095与1101站位钻取的漂移沉积物中的底流方位。本次研究共对两个站位的38根岩心开展测试分析，为上新世-更新世南极绕极流（Antarctic Circumpolar Current, ACC）物理记录的空间分布与方向特征提供了数据支撑。研究以每段岩心的古地磁矢量偏角与倾角为依据，将AMS主轴定向至地理坐标系。本次岩心定向以特征剩磁（characteristic remanent magnetization, ChRM）的实测方向为基础，结合岩心通用参考线完成定向，据此可确定1095站位（漂移体7）与1101站位（漂移体4）的古流相对于地理坐标系的方位。两个站位的古流方向均呈近NW-SE走向，其中1095站位的古流方向与一处沉积物波场平行。本研究表明，将磁组构分析与古地磁学方法相结合，可将深海沉积组构作为底流演化历史的长期替代指标。