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运用粒级-标准偏差和粒度端元模拟算法两种方法,对南海北部ODP1146站陆源沉积物粒度数据进行了分析和对比,探讨了东亚季风近20Ma以来的演化历史.选用粒级-标准偏差法提取出的两个敏感粒度组分含量的比值即10~19μm/1.3~2.4μm用来指示东亚冬季风相对夏季风强度的变化.粒度端元模拟法得出的粗端元组分EM1(风尘)堆积速率用来指示东亚冬季风强度及相应的风尘源区——亚洲内陆干旱地区的干旱程度的变化,而EM1/(EM2+EM3)比值可以指示冬季风相对夏季风强度的变化.组合指标变化显示出东亚冬季风强度和冬季风相对夏季风的强度在8MaBP左右显著加强,而3MaBP左右冬夏季风可能同时增强,结果可以与黄土、北太平洋风尘沉积、南海微体古生物记录等很好对比.青藏高原的阶段性隆升可能促进了东亚季风的这两次加强.
The grain-size data of terrestrial sediments in ODP1146 station in the northern South China Sea are analyzed and compared with the methods of grain size-standard deviation and particle size end-point simulation, and the evolution history of the East Asian monsoon since 20 Ma has been discussed. The grain-size-standard deviation The ratio of the content of the two sensitive grain fractions extracted is 10 ~ 19μm / 1.3 ~ 2.4μm, which is used to indicate the change of East Asian winter monsoon relative to the summer monsoon intensity.The coarse endmember EM1 ) The rate of accumulation is used to indicate the strength of the East Asian winter monsoon and the corresponding change in the degree of drought in inland arid regions of Asia, aridity, while the EM1 / (EM2 + EM3) ratio indicates the change in winter monsoon relative to the summer monsoon. The change of indicator shows that the intensities of East Asian winter monsoon and winter monsoon relative to the summer monsoon are significantly strengthened at around 8MaBP, while the winter-summer monsoon around 3MaBP may be enhanced at the same time. The result can be compared with that of loess, North Pacific dust deposit and Nanhai Microfacies The phased uplift of the Tibetan Plateau may have contributed to these two intensification of the East Asian monsoon.