Magnetic records of Core MD77-181 in the Bay of Bengal and their paleoenvironmental implications  

作　　者：LI Haiyan ZHANG Shihong FANG Nianqiao WANG Hongqiang 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China

出　　处：《Chinese Science Bulletin》2006年第15期1884-1893,共10页

基　　金：supported by the National Basic Research Program of China(973 Program)(Grant No.2006CB701400);Ministry of Education(Grant No.NCET-04-0727);the National Natural Science Foundation of China(Grant No.40272074).

摘　　要：高分辨率的环境磁性的大小在孟加拉的海湾在 CoreMD77-181 上被执行，包括磁性的危险性，非滞后的残余的磁化，所有样品的等温的残余的磁化，和磁性的危险性的温度依赖和代表性的样品的磁性的磁滞现象参数。结果建议那(1 ) 磁性的矿物质集合上面 9.82 m 沉积(相应于最后 160 ka ) 被伪单人赛领域磁铁矿统治，与在冰川的时期的更丰富的粗糙的谷物比在间冰期的时期；(2 ) 最高沉积的 6.50 m (相应于最后 70 ka ) 在磁性的矿物质的谷物尺寸显示出重要时间的变化，可能反映在印度夏天季风的变化和诺思大西洋(Heinrich 事件) 的快速的冷事件之间的电视连接；(3 ) 在 9.82 m 下面的沉积被顺磁的矿物质(可能包括的黄铁矿) 统治，建议减少的成岩作用。核心 MD77-181 的磁性的记录在阿拉伯的海比得上在孟加拉，和 ODP Hole722B 的海湾的核心 MD77-180 的那些。这研究建议在 160 kasignificantly 改变了的 ~ 的苍白的海洋学的事件北印度洋的氧化还原作用状态，从在到 oxic 的事件前的减少的环境或在事件以后的 suboxic 环境。High-resolution environmental magnetic measurements were carried out on Core MD77-181 in the Bay of Bengal, including magnetic susceptibility, anhysteretic remanent magnetization, isothermal remanent magnetization of all samples, and temperature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representative samples. The results suggest that （1） the mag- netic mineral assemblage of the upper 9.82 m sediments （corresponding to the last 160 ka） is dominated by pseudo-single domain magnetite, with more abundant coarse grains in glacial periods than in interglacial periods; （2） the uppermost 6.50 m of sediments （corresponding to the last 70 ka） shows significant temporal variations in grain sizes of magnetic minerals, possibly reflecting the teleconnection between variations of the Indian summer monsoon and rapid cold events of the North Atlantic （Heinrich events）; （3） the sediments below 9.82 m are dominated by paramagnetic minerals （probably including pyrites）, suggesting reductive diagenesis. The magnetic records of Core MD77-181 are comparable to those of Core MD77-180 in the Bay of Bengal, and ODP Hole 722B in the Arabian Sea. This study suggests that the paleoceanographic event at -160 ka significantly changed the redox state of the northern Indian Ocean, from a reductive environment before the event to an oxic or suboxic environment after the event.

关 键 词：磁记录 岩化作用 北印度洋 古环境 MD77-181 

分 类 号：P318[天文地球—固体地球物理学]