Paleomagnetic properties of ODP Site 119-744 (Appendix)

Paleomagnetic studies conducted on board JOIDES Resolution during Leg 119 indicate that the cores collected at Site 744 range from Quaternary through Eocene in age. Initial studies of the sediments completed on board the ship measured the magnetization of the archive halves of the sedimentary cores, using the pass-through cryogenic magnetometer. Stratigraphic plots of the declination and inclination derived from these measurements displayed numerous long intervals with essentially constant magnetic directions. Further study of these intervals led to a discovery that the background signal had been incorrectly computed due to faulty software on the ship. Because this background signal was not recorded in the data-processing system, corrections could not be made. Therefore, subsequent shorebased studies have been made on the individual samples collected at approximately 30-cm intervals in the cores in order to verify the initial magnetostratigraphy reported in the Initial Reports volume for Leg 119 (Barron, Larsen, et al., 1989, doi:10.2973/odp.proc.ir.119.1989). Numerous reversals were identified and correlations were suggested with the seafloor magnetic anomaly sequence of Berggren et al. (1985, doi:10.1130/0016-7606(1985)96<1407:CG>2.0.CO;2) back to anomaly number 17.

在第119航次期间于乔迪斯·决心号（JOIDES Resolution）钻探船上开展的古地磁研究（Paleomagnetic studies）表明，744站位采集的岩心年代跨度为第四纪（Quaternary）至始新世（Eocene）。船上先期完成的沉积物研究采用穿透式低温磁力仪（pass-through cryogenic magnetometer），对沉积岩心的归档半段（archive halves）开展磁化强度测量。基于上述测量得到的磁偏角（declination）与磁倾角（inclination）地层图，显示出多个持续时间较长、磁方向基本恒定的区间。后续对这些区间的深入研究发现，背景信号因船上软件故障出现了错误计算。由于该背景信号未留存于数据处理系统中，无法进行校正。因此，后续开展了岸基研究，对岩心中约每30厘米间隔采集的单个样品进行分析，以验证第119航次《初步报告》卷（Barron、Larsen等，1989，doi:10.2973/odp.proc.ir.119.1989）中报道的初始磁地层学（magnetostratigraphy）结果。本次研究识别出多次地磁反转，并提出可将其与Berggren等人（1985，doi:10.1130/0016-7606(1985)96<1407:CG>2.0.CO;2）提出的海底磁异常序列（seafloor magnetic anomaly sequence）对比至第17号磁异常。