藏南泽当卡多地区中生代放射虫动物群研究及其地质意义

雅鲁藏布江蛇绿岩带一直以来被认为是新特提斯洋岩石圈的残留,其与雅鲁藏布江缝合带内相关的海相地层共同记录了新特提斯洋的演化过程以及印度—欧亚板块的碰撞过程。位于藏南泽当西南卡多附近的硅质岩剖面中发现有保存较好的中生代放射虫化石,鉴定出放射虫31属39种,识别出4个放射虫组合,并将之与邻区及西特提斯地区放射虫化石带进行对比确定其时代:Alievium longispineum-Transhsuum maxwelli组合,晚巴通期—早卡洛夫期;Hsuum maxwelli-Triactoma mexicana组合,晚卡洛夫期—牛津期;Holocryptocapsa hindei-Hiscocapsa grutterinki组合,晚巴雷姆期—早阿普特期;Hemicryptocapsa polyhedra-Obeliscoites giganteus组合,晚阿尔布期—赛诺曼期。卡多硅质岩中所含放射虫组合可为泽当蛇绿岩的形成时限及新特提斯洋的演化提供重要的微体古生物依据。

Study of the Radiolarian Fauna from Kaduo in Zedang of Southern Tibet and the Geological Significance

The Yarlung-Zangbo Ophiolite Zone has long been considered as the lithospheric residual of Neo-Tethys, jointly with the marine stratum within the Yarlung-Zangbo Suture Zone, recorded the evolution of the Neo-Tethys and the collision between India Plate and Eurasian Plate. Moderate preserved Mesozoic radiolarian fossils have been found from the Kaduo Chert, near the southwest of the Zedang of southern Tibet. And 39 radiolarian species belonging to 31 genera have been identified preliminary. Four radiolarian assemblages have been recognized as follows in ascending: Alievium longispineum-Transhsuum maxwelli assemblages (Late Bathonian-Early Callovian), Hsuum maxwelli-Triactoma mexicana assemblages (Late Callovian-Oxfordian), Holocryptocapsa hindei-Hiscocapsa grutterinki assemblages (Late Barremian-Early Aptian) and Hemicryptocapsa polyhedra-Obeliscoites giganteus assemblages (Late Albian-Cenomanian). The radiolarian assemblages in the Kaduo chert can provide an important micropaleontological evidence for the formation time constrain on the Zedang ophiolite and the evolution of the Neo-Tethys Ocean.