西藏阿里札达盆地早更新世早期沉积及其古气候与古环境变化  

Early Pleistocene deposits and paleoclimatic and paleoenvironmental changes in the Zanda basin, Ngari area, 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,西藏拉萨850000

出　　处：《中国地质》2006年第6期1276-1284,共9页Geology in China

基　　金：国家自然科学基金项目(40572134);中国地质调查局项目(1212010511902)资助

摘　　要：综合分析了西藏阿里札达盆地早更新世早期的多种与气候环境变化密切相关的地质记录,结果表明该区早更新世早期的沉积可划分为3种不同的沉积相和4个岩性段;古气候与古环境变化可划分为4个阶段:(1)2.68～2.45 Ma,为冲洪积相沉积,冻融褶皱开始出现,植被以乔木为主,主要为松、藜、蒿,属山地寒温气候;(2)2.45～2.11Ma,为冲洪积相,地层中冻融褶皱多呈扭曲状,草本植物迅速上升,显示出灌木草原气候特征,气候变得凉爽干燥;(3)2.11～1.49 Ma,沉积相为冲洪积相—冰缘沉积相,以冰缘沉积相为主,冻融褶皱层开始增多,出现了喜凉的介形类化石,草本植物数量和种类达到最大,灌木也相对增加,显示气候进一步趋于干旱;(4)1.49～1.36 Ma,为冰湖沉积相,地层中普遍出现冻融褶皱,喜凉的介形类化石丰度很高,草本植物有小幅下降,但蕨类植物增加幅度较大,显示了干冷草原气候特征,气候干旱寒冷。The paper analyzes various geological records closely related to the earliest Pleistocene climatic and environmental changes in the Zanda basin, Ngari, Tibet. The analytic results indicate that the earliest Pleistocene deposits in the study area may be divided into three sedimentary facies and four lithozones and that the paleoclimatic and paleoenvironmental changes may be divided into four stages： （1） the 2.68-2.45 Ma stage, which is marked by alluvial and diluvial deposits, when freeze-and-thaw folds started to appear and the vegetations were dominated by arbores, mainly including Pinus, Chenopodiaceae and Artemisia, indicating a cool-temperate alpine climate; （2） the 2.45-2.11 Ma stage, which is also marked by alluvial and diluvial deposits, when most freeze- and-thaw folds in strata were contorted, herbaceous plants increased rapidly, showing the features of the shrub- grassland climate, and the climate became cool and dry; （3） the 2.11-1.49 Ma stage, which is marked by aUuvial- diluvial and periglacial deposits （mainly periglacial deposits）, when the freeze-and-thaw folds increased, there appeared cryophilic ostracods, and the quantity and varieties of herbaceous plants reached a maximum and the shrubs also increased relatively, showing that the climate became more and more arid; and （4） the 1.49-1.36 Ma stage, which is marked by glaciolacustrine deposits, when the freeze-and-thaw folds appeared extensively in the strata, the abundance of cryophilic ostracods was very high and the herbaceous plants decreased slightly but pteridophytes increased significantly, showing the features of the cold-dry grassland climate.

关 键 词：西藏札达 早更新世早期 孢粉记录 冻融褶皱 气候与环境变化 

分 类 号：P532[天文地球—古生物学与地层学]