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对位于孟加拉扇的MD77-181岩芯进行了详细的环境磁学测量,包括磁化率、非磁滞剩磁、等温剩磁,以及典型样品的磁化率随温度变化特征和磁滞参数等.结果表明:(1)~9.82m以上层段(相当于~160ka以来)以亚铁磁性的准单畴磁铁矿为主,磁性颗粒组合随冰期/间冰期发生周期性变化,冰期时磁铁矿的含量较相邻间冰期高,且粒度较相邻间冰期粗,反映了冰期时印度夏季风的减弱;~6.50m以上层段(相当于~70ka以来),磁性颗粒的粒度变化揭示了印度夏季风变化与北大西洋Heinrich快速冷事件之间的遥相关.(2)~9.82m以下层段(相当于~160ka以前)几乎不含亚铁磁性颗粒,顺磁性物质的影响显著,并出现黄铁矿,推测该段岩芯磁记录受还原成岩作用影响强烈.MD77-181岩芯磁记录与孟加拉扇MD77-180岩芯和阿拉伯海ODP722B岩芯具有很好的可对比性.据三支岩芯的对比研究推测,~160ka时可能发生一次改变整个北印度洋区氧化还原环境的古海洋学事件,此事件发生之前本区还原成岩作用对沉积物磁记录影响强烈,之后的环境变化抑制了还原成岩作用对沉积物磁记录的影响.
Detailed magnetic measurements of the environment of MD77-181 core located in Bengal fan, including magnetic susceptibility, non-hysteresis remanence, isothermal remanence, and magnetic susceptibility of typical samples with temperature and hysteresis parameters, etc. Results The results show that: (1) the zone above 9.82 m (equivalent to ~ 160 ka) is dominated by ferrimagnetic quasi-single-domain magnetite, and the magnetic particle assemblages change periodically with the glacial / interglacial periods, Is higher than that of the adjacent interglacials and the grain size is thicker than that of the adjacent interglacials, reflecting the weakening of the Indian summer monsoon during the glacial period. The grain size change of the magnetic particles revealed above the level of ~ 6.50m (equivalent to ~ 70ka) The teleconnection between the summer monsoon change and the Heinrich rapid cold event in the North Atlantic Ocean. (2) There is almost no ferrous magnetic particles in the zone below 9.82 m (equivalent to ~ 160 ka), the effect of paramagnetic substance is significant and yellow It is speculated that the magnetic recording of this section is strongly influenced by the reduction diagenesis.MDC77-181 core magnetic recording has a good contrast with the Bengal fan MD77-180 core and the Arabian Sea ODP722B core.According to the three rock The core of the comparative study speculated that ~ 160ka may occur once the whole change Paleoceanography event redox environment of the North Indian Ocean region, before this event occurs in this area is strongly influenced by the reduction of sediment diagenesis magnetic recording environmental changes after the suppression of the effects of the reduction of sediment diagenesis magnetic recording.