西藏阿里札达盆地上新世—早更新世的古植被、古环境与古气候演化  

Evolution of the Paleovegetation, Paleoenvironment and Paleoclimate During Pliocene-early Pleistocene in Zhada Basin, Ali, Tibet

作　　者：朱大岗[1] 孟宪刚[1] 邵兆刚[1] 杨朝斌[2] 韩建恩[1] 余佳[1] 孟庆伟[1] 吕荣平[1] 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]西藏自治区国土资源厅,拉萨850000

出　　处：《地质学报》2007年第3期295-306,共12页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号40572134);中国地质调查局项目"青藏高原第三纪重点古湖泊环境演变序列"(编号科[2005]005-02;工作项目编码:1212010511902)资助的成果。

摘　　要：本文将西藏札达盆地河湖相地层重新划分为第四系下更新统香孜组（Qp^1-1x）、新近系上新统古格组（N2^2g）和上新统托林组（N2^1t）。河湖相地层的古地磁法和ESR法测年结果表明，札达盆地内河湖相沉积地层的形成时代为新近纪上新世-第四纪早更新世。根据该套河湖相地层沉积演化和其中的孢粉组合特征、河湖相沉积中所发现的各种古动植物化石等的综合分析，笔者对札达盆地上新世-早更新世的古植被、古环境与古气候演变进行了探讨。结果表明，札达地区上新世-早更新世气候经历了从湿热-温暖潮湿-偏冷潮湿-寒冷干旱的变化，以及植被从森林-灌木-草原的逐渐演化。可将札达盆地上新世-早更新世环境演化划分为7个大的阶段，其总体特征是：①5．4～4．4Ma，札达地区处于亚热带湿热气候环境；④4．4～3．95Ma，为暖温带温暖潮湿气候；⑧3．95～3．5Ma，为偏凉潮湿阶段，气候开始转冷；①3．5～3．2Ma，为温暖潮湿阶段；⑤3．2～2．9Ma，气候转为偏冷潮湿阶段；⑥2．9～2．57Ma，该阶段气候偏冷而干旱，整体较为干冷；⑦2．57～1．36Ma，气候寒冷而干旱。表明自上新世-早更新世，该区的古气候环境在逐渐变干、变冷的总趋势上，经历了多次明显的冷暖与干湿波动。This paper divided the the fluvio-lacustrine facies sedments of Zhada basin into Xiangzi formation during late Pleistocene in Quaternary, Guge formation and Tuolin formationfour during Pliocene in Neogene. The dating results of paleomaguetism and ESR show that zhada basin sedments development between Pliocene in Neogene and Pleistocene in Quaternary. Based on the depositional evolution of the fluvio-lacustrine facies sedments, character of sporopollen assemblage, zoolites, plant fossils and so on, the authors discuss the paleovegetation, paleoenvironment and paleoenvironmental evolution during Pliocene-early Pleistocene in Zhada basin. They think that the climate change from wet-hot, warm-wet, little cold-wet, to cold-drought, and the vegetational evolution from forest, bush, to grassland in Zhada area. The environmental evolution can be divided into 7 phase in Zhada basin, and the character of every phase as follow： （1）during 5.4-4.4Ma, Zhada basin was in wet-hot subtropic climate;（2）during 4.4- 3.95Ma, was in warm-wet temperate zone climate;（3） during 3.95-3.5Ma, was in little cold-wet phase and begin to cold climate;（4）during 3.5-3.2Ma,was in warm humid phase; （5）during 5 3.2-2.9Ma,was in little cold-wet phase,（6）during 2.9-2.57Ma, was in little cold-drought climate; （7）during 2. 57- 1. 36Ma, was in very cold-drought climate. This results show that during Pliocene-early Pleistocene, the main trend of the climate was from warm to cold, from wet to drought, but there were some obviously fluctuate.

关 键 词：西藏札达 上新世-早更新世 孢粉记录 古生物 古环境与古气候 

分 类 号：Q911[天文地球—古生物学与地层学]