安达曼海沉积物粒度记录的全新世印度洋夏季风演化

Indian Summer Monsoon evolution in the Andaman Sea during the Holocene: Evidence from grain size records

对位于安达曼海区的柱状样ADM-C1进行了沉积物粒度分析,根据标准偏差变化对粒度组分进行了划分。发现2个主要敏感粒级组分1.5~11.9μm、11.9~74μm有明显的波动变化,研究认为它们主要受控于与印度洋夏季风密切相关的海域环流动力变化。通过敏感粒级组分相关指标变化重建了安达曼海区全新世以来印度洋夏季风演化历史,结果表明全新世印度洋夏季风变化总体可以分为3个演化阶段:1)10.4~8.8ka BP,印度洋夏季风强度为3个阶段最弱时期;2)8.8~4.7ka BP,敏感粒级组分占全样的百分含量和平均粒径均明显增加,表明印度洋夏季风强度处于全新世最强盛时期;3)4.7~0ka BP,敏感粒级组分占全样的百分含量和平均粒径明显降低,指示了该时期印度洋夏季风的强度较前一阶段明显减弱。粒度重建的印度洋夏季风变化与其他重建结果在全新世有较好的一致性,表明敏感粒级组分在安达曼海可以作为研究印度洋夏季风变化的可靠替代指标。

Based on the sediment grain size analysis of the gravity core ADM-C1from the Andaman Sea,grain size populations were partitioned using the method of grain size versus standard deviation.It was found that two sensitive grain size populations(1.5~11.9μm and11.9~74μm)had significant fluctuations,and were mainly controlled by the circulation dynamics in the sea area,which was closely related to the Indian Summer Monsoon(ISM).Evolution history of the ISM in the Andaman Sea during the Holocene is reconstructed based on sensitive grain size populations.The results show that the evolution history of the ISM generally can be divided into three stages:10.4~8.8ka BP,when the intensity of the ISM was the weakest of the three stages;8.8~4.7ka BP,when percentage and average grain size of the sensitive grain size populations had significant increase,indicating that the intensity of the ISM was at its strongest stage during this period;and4.7~0ka BP,when sharp decreases of percentage and average grain size of the sensitive grain size populations indicated that the intensity of the ISM was obviously weaker than those of the previous two stages.The reconstructed evolution history of the ISM shown in this paper is consistent with many other records during the Holocene,and further verifies the feasibility that sensitive grain size can be used as a reliable proxy of the ISM in the Andaman Sea.