西藏西南部札达盆地新近纪的孢粉组合  

Neogene palynological assemblages in Zanda Basin,southwestern Tibet

作　　者：吴旌[1,2] 徐亚东[1,2] 张克信[1,2] 陈奋宁[3] 陈锐明[3] 陈林[1,2] 

机构地区：[1]中国地质大学(武汉)生物地质与环境地质国家重点实验室,湖北武汉430074 [2]中国地质大学(武汉)地球科学学院,湖北武汉430074 [3]西安地质矿产研究所,陕西西安710054

出　　处：《地质通报》2013年第1期141-153,共13页Geological Bulletin of China

基　　金：中国地质调查局国家青藏专项<青藏高原新近纪隆升与地质时间群研究>(编号:1212011121261);国家地质学理科基地人才培养基金项目(批准号:J0830520);国家自然科学基金项目<国家创新研究群体科学基金>(批准号:40921062)资助

摘　　要：札达盆地位于西藏自治区西南部阿里地区的喜马拉雅山区,是形成于晚中新世的断陷盆地。研究剖面位于札达县城南4km的多几东,发育一套良好的河湖相沉积地层。结合前人得出的古地磁结论和地层综合对比,托林组的时代为9.2～2.6Ma,香孜组的时代为2.6～1.7Ma。沿剖面自下而上可划分出6个孢粉组合及对应的植被类型:①孢粉组合1-2(9.2-约5.6 Ma),为亚热带—温带落叶针阔叶混交林,其中9Ma左右气候较寒冷干旱,经历了一次由寒冷干旱向温暖湿润的转变过程;②孢粉组合3-5(5.6-约3.1Ma),由亚热带—温带常绿—落叶针阔叶混交林,期间存在一次暖湿气候的波动;③孢粉组合6(2.8-约1.7Ma),为寒冷干旱气候下生长的温带落叶针阔叶混交林—亚高山针叶林。The Zanda Basin is a Neogene rifted basin in Ngari Prefecture, southwest Tibet. It was formed in Late Miocene, at about 9.2Ma. The Duojidong section is located about 4km south of Zanda County. It has a well-developed set of lacustrine sedimentary strata. Palaeo-current measurement and provenance analysis show that the age interval of the Tuolin Formation is about 9.2-2.6Ma, and the Xiangzi Formation is dated at about 2.6-1.7Ma. As the sporopllen data can directly reflect paleoclimate changes, sporopllen data have been always regarded as one of the best environmental indicators. Through the palynological analysis, 6 palynological assem- blages and vegetable types were recognized, and 3 phases of paleoclimatic changes were revealed： ①from 9.2Ma to 5.6Ma, correlated with assemblages 1-2, the environment was cold shrub steppe at about 9Ma, and then became warm and humid subtropical-temperate deciduous coniferous and broad-leaved mixed forests; ② from 5.6Ma to 3.1Ma, correlated with assemblages 3-5, the environment was mild and humid evergreen-deciduous broad-leaved mixed forests, and changed to the warm and a little dry deciduous conifer mixed forest at about 3.6Ma. This stage had a climate fluctuation; ③ from 8Ma to 1.7Ma, correlatied with assemblage 6, the environ- ment became cold and dry deciduous coniferous and broad-leaved mixed forests and subalpine coniferous forests.

关 键 词：札达盆地 孢粉组合 古气候变化 新近纪 

分 类 号：P534.62[天文地球—古生物学与地层学]