西藏高原洞穴堆积物的粘土矿物组合特征及其古地理意义

CHARACTERISTICS OF CLAY MINERAL COMPOSITION IN THE SPELEOTHEMS ON XIZANG PLATEAU AND ITS PALAEOGEOGRAPHIC MEANING

本文通过对西藏高原洞穴堆积物的粘土矿物组合特征的分析,初步探讨了喀斯特地貌形成的古地理环境。喜马拉雅山北坡旧定日东山洞穴堆积物是较温湿的森林草原环境下的产物,新定日西侧遮普若山北坡洞穴堆积物则是在高寒草甸环境下形成的;拉萨西南曲水大佛后溶洞堆积物形成于湿热的亚热带气候环境,而拉萨西山洞穴堆积物却形成于较温湿的草原环境;唐古拉山南坡安多一带的洞穴堆积物则是在高寒的草甸环境下形成的。并以此研讨了西藏高原喀斯特的成因和时代。

Based on an analysis on the characteristics of clay mineral composition in the speleothems on Xizang Plateau, the palaeogeographic environment in which the karst landforms were formed have been studied.Speleothems in the karst caves at Tingri with cold and dry steppe environment at present on the northern slope of the Mt. Himalaya were formed in warmer and wetter forest steppe environment. Speleothems in the karst caves on the northen slope of the Mt. Zeberi at New Tingri were formed in the cold alpine meadow environment. The brown-red light clay deposits in a karst cave at Quxu of southwest Lhasa indicate that they may be formed in warmer and wetter environment,corresponding to that of the present northern subtropical zone in East China in terms of its humidity and temperature. The cave diposits of the mountain area at the west part of Lhaza were formed in a rather warm and semi-wet steppe environment which was warmer and wetter than the present. The cave deposits on southern slope of the Mt. Tanggula at Amdo may formed in the cold slpine meadow environment. Based on these results,the formation and ages of the ancient karst landforms on Xizang Plateau are discussed.