班公湖—怒江缝合带中西段改则地区木嘎岗日岩群的孢粉型化石组合及时代

Palynomorph fossil assemblages and ages of Muga-Gangri Rock Group in Gaize area of the middle and western part of Bangong Co-Nujiang suture zone in Tibet

班公湖—怒江缝合带中西段改则地区木嘎岗日岩群的沉积时代,经历了班公湖—怒江洋盆的裂解拉张和挤压会聚阶段,沉积时代跨度较大,但其沉积时代上限尚无定论。为探讨木嘎岗日岩群沉积时代上限与班公湖—怒江洋闭合时限的关系,通过野外地质调查及室内综合研究,在木嘎岗日岩群中发现了早白垩世早期典型花粉分子Dicheiropollis。这一发现表明:班公湖—怒江缝合带中西段改则地区木嘎岗日岩群在早白垩世早期还持续沉积,对探讨班公湖—怒江缝合带中西段中生代时期海域的古地理特征、沉积环境及其发展历史有重要的地质意义。

The sedimentary age of Muga-Gangri Rock Group in the middle and western part of Bangong Co-Nujiang suture zone experienced the cleavage and extension of Bangong Co-Nujiang Ocean basin and the stage of extrusion convergence.The sedimentary age span is relatively large,but its sedimentation epoch limit is still inconclusive.In order to explore the relationship between the upper limit of the sedimentary age of Muga-Gangri Rock Group and the closure time of Bangong Co-Nujiang Ocean in the rectified area,through the field geological survey and indoor comprehensive research,the authors found the typical pollen molecule Dicheiropollis in Early Cretaceous.This discovery of pollen indicates that Muga-Gangri Rock Group in the middle and western part of Bangong Co-Nujiang suture zone continued to deposit in Early Cretaceous.These discoveries have great geological significance in the discussion of paleo geographical features,sedimentary environment and their development history in Mesozoic period in the middle and western part of Bangong Co-Nujiang suture zone.