塔克拉玛干沙漠的形成时代及发展过程

ON THE AGE AND EVOLUTION OF THE TAKLIMAKAN DESERT

对塔克拉玛干沙漠腹地的近期研究表明，塔里木盆地虽早在白垩纪晚期已出现明显的干旱环境，但具有现代干旱特征的环境始于第三纪末，形成于第四纪初。盆地内部沙漠环境形成于中更新世或其晚期。沙漠在晚更新世晚期和全新世中晚期大规模向西、西南地区和东部发展。

The environment with the characteristics of modern dry climate started at the end ofTertiary(or Pliocene),and formed in Quaternary although the arid environment of the TarimBasin can be traced back to Cretaceous. The whole developing period can bc divided into following stages: 1. arid tropic climate with small humid fluctuations from Cretaceous to earlyOligocene ; 2. semi － humid warm climate from late Oligocene to the end of Mibcene; 3. aridwarm climate in Pliocene ; 4. extremely arid climate with warm temperate(in interglacial andmodern time)and cold (in glacial stages)alternations.The age of the desert formation (or accumulation of the eolian sand)is much youngerthan that of the arid environment. It is because the eolian sedimentary environment(by meansof geomorphology and neotectonics)formed very late. According to the developing propertiesof the underlying formations, their ages and relationships,the bottom of the eolian sand canbe confirmed, and the formation of the desert might start at the late time of middle Pistocene,or much more generally speaking,in middle Pistocene. Accurate age of the desert should begiven by efficient dating data in the future.All studies present two important developing stages of the desert. They started respectively at late time of late Pleistocene(17.0－ 17.5 ka B. P. )and built up the foundation andthe outline of the modern eolian landforms,and at the mid － Holocene(about 5. 0 ka B. P. )finished the final development of the modern desert. The geomorphologic background of thepresent sand dunes is a complex of fiuvial sedimentary plains and buried eolian sandy plains.