摘要
西藏的白垩—古近纪孢粉资料迄今鲜有发掘,因此我们对西藏当时的古植物区系、古植被和陆地生态系统等的了解也就甚为了了。本文对位处当时劳亚大陆南部边缘的仲巴县错江顶白垩系—古近系进行了孢粉分析。研究揭示,剖面的孢粉组合可划分为两个孢粉组合带,自下而上分别为Classopollis-Exesipollenites-Cycadopites组合和Pinuspollenites-Quercoidites-Trilobapollis组合,其时代分别为晚白垩世晚期Santonian—Maastrichtian和古近纪古新世—始新世。剖面的白垩系/古近系界线可能位于曲贝亚组和曲下组之间。针叶树花粉大量繁盛,特别是一些类型如Abiespollenites、Cedripites、Piceapollis和Tsugaepollenites仅见于曲下组顶部至加拉孜组底部的孢粉组合,反映了一次与构造运动密切相关的古环境变化事件,可能指示了印度—劳亚板块碰撞的开始。研究区孢粉植物区系与中国南方植物区系有很好的可比性,而与印度北缘同期植物区系区别明显,暗示着印度与劳亚大陆之间的海域直至始新世仍然具有明显的隔离作用,阻碍着两侧大陆上植物区系间的交流。
Scarcity of the data on the Cretaceous and Paleogene sporo-pollen results in a poor understanding of palaeofloras, palaeovegetation, and palaeo-ecosystem in Tibet. This paper mainly analyzed sporo-pollen from the Cretaceous and Palaeogene sediments at Cuojiang, Zhongba County, which is located at the southern margin of the Laurasia continent. Two palynological assemblage zones were recognized from the section including, in ascending order, the Classopollis Execlpollenites Cycadopites assemblage zone and the Pinuspollenites Quercoidites Trilobapollis assemblage zone. The both can be assigned to late Late Cretaceous or Santonian to Maastrichtian, and Paleogene, or Palaeocene to Eocene respectively. The Cretaceous/Paleogene boundary in this section might possibly locate between the Qubeiya Formation and the Quxia Formation. Pollen of needle-leafed trees flourished greatly; but some pollen such as abiespollenites, cedripites, piceapollis and tsugaepollenites were only present at top of the Quxia Formation and base of the Jialazi Formation, suggesting a paleoenvironmental event closely related to a certain tectonic activity, probably the beginning of the collision between Indian and Laurasian plates. The studied palynofloras can be compared with those in south China, but different from those in the northern margin of India, implying that the marine realm between India and Laurasia continents had been isolating floral communication of two continents by Eocene.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2008年第5期584-593,I0002,I0003,共12页
Acta Geologica Sinica
基金
国家重点基础研究发展规划项目(编号2006CB701402)
国家自然科学基金项目(编号40502003)资助的成果
关键词
孢粉
白垩纪
古近纪
板块碰撞
西藏
palynology
Cretaceous
Paleogene
plates collision
Xizang （Tibet）
