Provenance and Origin of the Late Cenozoic Dayi Conglomerates in the Western Margin of the Sichuan Basin: New Insights from Heavy Mineral and Spore-Pollen Assemblages
详细信息
- 责任者：Zheng Yong (Key Laboratory of the Earth’s Deep Interior ; Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Kong Ping
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(8)
- 关键词：砾岩 ; conglomerate ; 物源分析 ; provenance analysis ; 四川盆地 ; Sichuan Basin
- 页码：p.2949-2958
- 图表：4 illus., 2 tables, 55 refs.
- 分类号：0803
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The collision between Indian and Eurasian plates initiated in the Early Cenozoic produced the high Tibetan Plateau. Accompanied with the uplift of the Tibetan Plateau Tertiary sediments are almost absent in the adjacent Sichuan Basin,and the preserved oldest deposits are the Late Cenozoic Dayi conglomerates. Therefore,Dayi conglomerates can potentially provide information on palaeoenvironments and tectonic evolution of the Tibetan Plateau and adjacent areas. This paper reports heavy mineral compositions and spore-pollen assemblage within three Dayi conglomerates and a modern sand sample from the bank of the Min River and attempts to understand the origin of Dayi conglomerates through provenance analysis and sedimentation environment studies. Dayi conglomerates contain a variety of heavy minerals,which suggests that the provenance of the Dayi conglomerates covers a wide range of petrologic types. Except for extremely unstable minerals,the similarity in heavy mineral compositions between a newly exposed Dayi conglomerate and the modern sand from the Min River suggests that the Dayi conglomerates were delivered to the Sichuan Basin by the Min River, and during which time the Min River already dissected the Longmen Shan and was sourced to Songpan-Ganzi flysch belt. Garnet rarely occurs in natural profiles of Dayi conglomerates and we attribute this to intense weathering in an acidic environment. Spore-pollen is very scarce in the Dayi conglomerates with a concentration of 0.2 grains/g. Species are mostly derived from alpine coniferous forest and a few from deciduous broad-leaf and herbaceous plants. Such an assemblage reflects cold environment. Together with available chronological data for the Dayi conglomerates,we prefer that the Dayi conglomerates are glaciofluvial deposits formed ～2.0Ma ago. Formation of Dayi conglomerates reflects Early Quaternary cold environment in the eastern margin of the Tibetan Plateau.
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |