川西高原甘孜黄土与印度季风演化关系  

RELATION BETWEEN THE LOESS STRATIGRAPHY ON THE EASTERN TIBETAN PLATEAU AND INDIAN MONSOON

作　　者：陈诗越[1] 方小敏[2] 王苏民[1] 

机构地区：[1]中国科学院南京地理与湖泊研究所 [2]兰州大学地理系,兰州730000

出　　处：《海洋地质与第四纪地质》2002年第3期41-46,共6页Marine Geology & Quaternary Geology

基　　金：国家杰出青年科学基金 (4 992 810 1) ;中国科学院引进国外杰出人才计划项目 (科发人教字 [2 0 0 0 ] 0 5 )

摘　　要：川西高原甘孜黄土地层的磁化率、土壤颜色、碳酸盐含量综合分析表明 ,早在 1.15 Ma前 ,印度季风就已影响本地区 ,并且印度季风与同期影响黄土高原的东亚夏季风相比 ,似有共同的盛衰变化 ,尤其是 0 .5 Ma前更为相似 ,说明印度季风与东亚季风有共同的驱动机制 ;但 0 .5 Ma以后 ,印度季风对本地区的影响呈逐步衰减之势 ,这可能与青藏高原又隆升到一个新的临界高度有关 ,从而阻挡了印度季风的水汽输入。另外 ,黄土高原揭示的 L 9、L 15极端冷干事件 ,甘孜黄土反映较弱。而黄土高原反映的 L 6冷干事件 ,甘孜黄土表现的却是极端冷湿事件 。Loess is widely distributed on the eastern Tibetan Plateau.It has been demonstrated that the Tibetan loess is so called 'cold loess' derived chiefly from the Tibetan Plateau itself.A so far thickest(32 m)loess section is observed in the Ganzi Basin on the sixth (highest) terrace of the Yalong Jiang River,one of the largest tributaries of the Jinsha River(upper Yangtze River).The section consists of 15 loess layers L1~L15 and 21 layers of paleosols that can be grouped into 14 distinct paleosol complexes marked as S0 to S14. Magnetic susceptibility,CaCO 3 content and soil color are widely used as sensitive proxies of summer monsoon changes.These proxies of the loess paleosol sequence in Ganzi were measured.The result shows that the Indian Ocean monsoon circulation existed before 1 15 MaBP,and climatic change in this area coincides with that in eastern China.But there are differences between them.Before 0 5 Ma,Indian monsoon seemed to be as powerful as the synchronous East Asian monsoon that affected the Loess Plateau,but after 0 5 Ma,the Indian monsoon had gradually weaker influence on this area.Maybe it had something to do with the uplift of the Tibetan Plateau,as the new critical height of the plateau had prevented the Indian monsoon from entering.It indicates that the climate has been cold dry in this area since 0.5 MaBP due to Tibetan Plateau uplift. In addition,the loess section reveals two extremely cold events spanning ca.0 92~0 95 Ma and 0 65~0 55 Ma,just matching the lithological specialities,typical loess layer L10 and greenish laminated loess layer L6.

关 键 词：印度季风 环境演化 甘孜黄土 川西高原 古气候 大气环流 东亚季风 驱动机制 

分 类 号：P642.131[天文地球—工程地质学] P532[天文地球—地质矿产勘探]