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西藏札达盆地晚上新世—早更新世孢粉组合及其地质意义

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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9.6 Ma 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1 km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2.60~1.67 Ma 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,2.67 Ma以后气候逐渐向干旱转变,地层对比时代为晚上新世(2.75~2.60 Ma);(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2.38 Ma逐渐变为针叶林,气候趋向变冷,地层对比时代为早更新世(2.54~2.16 Ma);(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(2.13~1.86 Ma).
Geological Significances of Late Pliocene-Early Pleistocene Palynological Assemblage in Zanda Basin, Tibet
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.

Qinghai-Tibetan PlateauZanda Basinpalynological assemblagepalaeoclimatic changeLate Pliocene-Pleistocene

江尚松、向树元、徐亚东

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中国地质大学研究生院,武汉,430074

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

中国地质大学地球科学学院,武汉,430074

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

中国地质调查局国家青藏专项国家自然科学基金国家自然科学基金

12120106101034062100240830212

2010

地质科技通报
中国地质大学(武汉)

地质科技通报

CSTPCDCSCD北大核心
影响因子:1.018
ISSN:2096-8523
年,卷(期):2010.29(4)
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