南极半岛鲍威尔海盆D4-9柱样古地磁及磁组构特征

PALEOMAGNETIC CHARACTERISTICS OF A CORE FROM THE POWELL BASIN,ANTARCTIC PENINSULA

为了探讨中更新世以来南极半岛东北部鲍威尔海盆沉积环境气候演变及古流向特征,对采自南极半岛东北部鲍威尔海盆内一根3 m长的柱样进行了古地磁和磁组构参数测试和特征分析。结果表明:(1)该柱样在2.73 m处为布容正极性与松山反极性期的界线,由此推算出在距今780 ka到现代该区域沉积速率较低,约为0.35 cm·ka-1;(2)中更新世以来该区域共出现过5次暖沉积事件,并且在暖期事件中存在3次明显的冷期气候波动事件;(3)该区域在暖期古流向方向不明显,水流方向变化频繁,而在暖期之间的过渡时期,古流向以近似南北向为主。

One 3-m-long gravity core （D4-9） was obtained from the Antartic Powell Basin, which is located in the northeastern area of the Antarctic Peninsula. Anisotropy of magnetic susceptibility （AMS） and paleomagnetism data were acquired using KLY-3s and 2G superconducting magnetometers. A remarkable plus inclination stage was identified at a depth of 2.73 m and based on the Matsuyama reversed polarity time ; we calculated that the sedimentation rate is 0.35 cm . ka-1 from now to 780 ka BP. Five warm climate periods were identified from magnetic susceptibility and grain size characteristics in the core, and there are 3 gradual climate transition stages between warm periods, which changed from warm to cold, and then from cold to warm. Based on our AMS analysis, we found that the paleocurrent direction was not obvious in the warm period; it changed frequently, and the approximate paleoeurrent direction was north-south in the transition period between the warm periods.