试论青藏高原第四纪沉积地球化学演化与环境变迁

GEOCHEMICAL EVOLUTION AND ENVIRONMENT CHANGES SINCE QUATERNARY IN QING-ZANG(INGHAI-TIBET)PLATEAU

本文扼要介绍最近几年青藏高原第四纪沉积物的元素地球化学、同位素地球化学、有机地球化学和矿物学及其与气候环境关系研究的一些新进展。青藏高原第四纪沉积地球化学信息综合分析，初步建立了长、短期时间尺度的气候曲线。揭示了青藏高原强烈隆升引起的气候环境配制的改变，即在３．４０－０．７３ＭａＢ，Ｐ．高原强烈隆升，亚洲季风稳定形成，气候以干冷、湿暖型波动为主；０．７３ＭａＢ．Ｐ．以来高原再次强烈隆升，气候环境愈趋干旱；进入全新世以来，出现凉干、暖干、暖湿和冷湿的多种气候波动模式。在空间格局上划分二个地球化学沉积区，即西藏和新疆为富镁区；青海为富钾区。还揭示了青藏高原湖泊沉积地球化学的分带性，其分带规律与高原隆起的差异性是一致的。此外，青藏地区风化壳和古土壤的地球化学演化与高原古气候变迁也有紧密联系。

The paper briefly introduces research advances in elemental geochemistry,isotopegeochemistry,organic geochemistry and mineralogy of sediments sihce Late Cenozoic andtheir relations with climatic environmental changes in Qing-Zang Plateau,Syntheticanalysis of geochemical information has preliminarily established climatic curves of longand short time scales.The changes of climatic environment compound were revealed,which was due to uplift of Qing-Zang Plateau,that is:in 30-3.4Ma B.P.,the uplift wasnot fast and the monsoon not yet stable ,and climate was sometimes dry and warm,andsometimes cold and humid;in 3.4-0.73Ma B.P.,Qing-Zang Plateau rapidly uplifted,Asian monsoon tended to be stable,and climatic fluctuation mainly appeared as cold-dryand warm-humid;the plateau intensively rose again since0.73Ma B.P.,and climatic en-vironment became more dry;and varied model of climatic fluctuation appeared as cool-dry,warm-dry,cold-humid and warm-humid since Holocene. In space pattern,two depo-sitional areas of geochemistry were divided,one is the area of Xizang(Tibet)and Xinjiangwhich is rich in magnesium,the other area is Qinghai which is rich in potassium,Thegeochemical zones of deposition were also revealed in Qing-Zang Plateau ,and the zona-tion regularity corresponded to discrepancy of plateau uplift.In addition,geochemicalevolution of weathering crust and paleosols in Qing-Zang area was closely related to pa-leoclimate changes of the plateau