西藏札达盆地晚上新世—早更新世孢粉组合及其地质意义  

Geological Significances of Late Pliocene-Early Pleistocene Palynological Assemblage in Zanda Basin,Tibet

作　　者：江尚松[1,2] 向树元[3] 徐亚东[1,2] 

机构地区：[1]中国地质大学研究生院,武汉430074 [2]中国地质大学生物地质与环境地质教育部重点实验室,武汉430074 [3]中国地质大学地球科学学院,武汉430074

出　　处：《地质科技情报》2010年第4期21-31,共11页Geological Science and Technology Information

基　　金：中国地质调查局国家青藏专项(1212010610103);国家自然科学基金项目(40621002;40830212)

摘　　要：札达盆地位于青藏高原西南隅的阿里地区，是在中新世晚期约9．6Ma B.P．形成的一个NW-SE向断陷盆地。该盆地在上新世-早更新世发育一套完整的河湖-冲积扇相地层。在札达县香孜乡西北约1km处精细实测了上上新统一下更新统香孜剖面。根据前人的古地磁及ESR年龄数据确定下更新统香孜组年龄为2．60-1．67Ma B.P．。根据孢粉学研究把香孜剖面自下而上划分为3个孢粉组合带（8个孢粉组合），并据此将札达盆地2．75Ma B.P．以来的气候变化划分为3个阶段：（1）孢粉组合带Ⅰ（孢粉组合1～2），植被为温暖偏湿的常绿与落叶针阔叶混交林，2．67Ma以后气候逐渐向干旱转变，地层对比时代为晚上新世（2．75～2．60Ma）；（2）孢粉组合带Ⅱ（孢粉组合3～5），发育温凉偏湿的亚高山落叶针阔叶混交林，并在约2．38Ma逐渐变为针叶林，气候趋向变冷，地层对比时代为早更新世（2．54—2．16Ma）；（3）孢粉组合带Ⅲ（孢粉组合6～8），发育寒冷干旱的高山针叶林，并存在高寒灌丛草甸草原，低海拔处零星分布落叶针阔叶混交林，指示较强的地势差异，地层对比时代为早更新世（2．13～1．86Ma）。The Zanda Basin is a northwest-southeast extensional basin distributed in Nagri area, southwest of Tibet, formed in Late Miocene, about 9.6 Ma. It contains a well preserved series of lacustrine, fluvial and alluvial sediments. A study is made of one section in the basin located 1 km northwest of Xiangzi Village, Zanda County. Based on the previous ESR and paleomagnetostratigraphic research, the age interval of the Xiangzi Formation is dated most reasonably between 2.6 Ma B.P. and 1.67 Ma B. P.. Through abundant palynological analyses, 3 palynological zones and 8 palynological assemblages and vegetable types are recognized, and 3 phases of paleoclimatic changes are revealed： （1） 2.75-2.60 Ma, correlated with palynological zone Ⅰ and assemblage 1--2, when it was warm and damp-humid with coniferous-leaved and broad-leaved mixed forests, but the climate changed to dump-dry after 2.67 Ma. （2） 2.54-2.16 Ma, correlated with palynological zone Ⅱ and assemblage 3--5, when it turned to cool and humid deciduous coniferous-leaved and broad-leaved mixed forests, and gradually changed to cold deciduous coniferous-leaved forests, indicated by the increase in the cold-tolerant tree taxa. （3） 2.13--1.86 Ma, correlated with palynological zone Ⅲ and assemblage 6--8, the increase of cold-tolerant bush taxa and drought-tolerant herb taxa suggested the climate change into cold and arid, while coniferous-leaved and broad-leaved mixed forests survived at the low altitude.

关 键 词：青藏高原 札达盆地 孢粉组合 古气候变化 晚上新世-早更新世 

分 类 号：Q944.571[生物学—植物学]