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对位于甘肃灵台的邵寨红粘土剖面进行了系统的磁性地层研究,并对色度的古气候意义进行了探讨。磁性地层研究结果表明,邵寨剖面典型风尘堆积的底界年龄约为5.23Ma B.P.;色度测试结果显示,红粘土的红度和黄度值具有较好的相关性,是反映东亚夏季风强度变化的理想指标;邵寨红粘土的亮度值变化在2.6~3.6Ma B.P.期间与成壤强度的相关性较好,但3.6Ma B.P.以后,两者相关性较差,可能与该时期形成的大量非成壤碳酸盐有关。进一步的研究并结合与已有研究成果的对比分析揭示出,邵寨红粘土剖面的红度、黄度及磁化率指标完整的记录了上新世4.4Ma B.P.以来东亚夏季风阶段性增强的演化过程,该过程与青藏高原西北缘的主体隆升及巴拿马海峡关闭在时间上是一致的,这二者可能是该时期东亚夏季风增强的主要驱动因素。
A systematical magnetic stratigraphic study was conducted on the Shaozhaihong clay profile in Lingtai, Gansu, and the paleoclimatic significance of the chromaticity was discussed. The results of magnetic stratum show that the bottom boundary age of typical dust accumulation in Shaozhai section is about 5.23Ma BP. The results of chromaticity test show that the redness and yellowness of red clay have a good correlation, which reflect the intensity of East Asian summer monsoon The change of brightness index of Shaozhaidong clay is better than that of soil strength during 2.6 ~ 3.6Ma BP. However, after 3.6Ma BP, the correlation between them is poor, which may be related to the large amount Non-carbonitrided. Further study and comparison with the existing research results reveal that the redness, yellowness and magnetic susceptibility of the Shaozhai red clay profile completely record the evolution of the East Asian summer monsoon since the Pliocene 4.4Ma BP This process is consistent in time with the main uplift of the northwestern margin of the Tibetan Plateau and the closure of the Panama Strait, both of which may be the main drivers of the intensification of East Asian summer monsoons during this period.