ENVIRONMENTAL MAGNETISM OF QUATERNARY MARINE SEDIMENTS FROM THE ANTARCTIC REGION AND ITS PALEOCLIMATE IMPLICATIONS.

对日本国家石油公司(JNOC)南极地质地球物理研究项目采集的22个沉积物岩心样品进行了古地磁和岩石磁学研究。这些岩心被转移到日本地质调查局。这些磁芯没有受到严重的磁性损坏，尽管它们在冷藏了10多年后自2002年以来一直保存在室温中。我们对自然剩余磁化强度(NRM)和磁化率的测量结果与JNOC报告的结果一致。测量了岩石的磁化参数、磁滞剩余磁化强度(ARM)、饱和等温剩余磁化强度(SIRM)、磁化率各向异性(AMS)和高温、低温热磁曲线。此外，我们还测量了一些样品的粒度分布。粒度分布表明，这些沉积物来自南极洲，与冰盖一起输送。岩石磁学结果表明，这些沉积物中的磁性矿物为磁铁矿和磁铁矿。我们找不到硫化铁。因此，我们认为南极周围的第四纪海洋环境是富氧的。我们关联了东南极威尔克斯兰(60-75°S，110-180°E)海洋沉积物的粒度分布和岩石磁性参数，因为岩石磁性参数显示出几个明显的变化。这些参数是S比(背磁场：0.1T)、HRC/Hc、MR/ms和Sirm/k，结果表明，晶粒度分布与S比和Sirm/k都有明显的相关性，这些核底部的年龄约为0.7 Ma。这些岩石磁性参数的变化是由冰盖的减少和增加引起的。

Paleomagnetic and rock magnetic studies were performed on 22 sediment core samples taken by the Antarctic Geological and Geophysical Research Project of the Japan National Oil Corporation (JNOC). These cores were transferred to the Geological Survey of Japan. These cores did not suffer serious magnetic damage, though they have been kept in a room temperature since 2002 after being kept refrigerated for more than 10 years. Our results of measurements of natural remanent magnetization (NRM) and magnetic susceptibility agree with the results of the JNOC reports. We measured some rock magnetic parameters, anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), anisotropy of magnetic susceptibility (AMS) and high and low temperature thermo-magnetic curves. In addition, we measured grain size distributions of some samples. The grain size distribution shows these sediments came from Antarctica transported with ice sheets. Rock magnetic results show magnetic minerals of these sediments are magnetite and maghemite. We could not find iron sulfide. Therefore, we concluded Quaternary marine environment around Antarctica were oxygen rich.We correlated grain size distributions and rock-magnetic parameters in marine sediments from off Wilkesland, East Antarctica (60-75deg.S, 110-180deg.E), because the rock magnetic parameters show several clear changes. These parameters are S-ratio (back magnetic field : 0.1T), Hrc/Hc, Mr/Ms, and SIRM/k. As a result, clear correlation was found between grain size distribution and both S-ratio and SIRM/k. The age at bottom of these core are about 0.7Ma. We concluded these rock magnetic parameter changes caused by decrease and increase of ice sheets.