藏北唐古拉山地区沱沱河组孢粉组合及其地层意义

唐古拉山地区广泛出露早新生代陆相红层, 确定这些红层的时代对认识青藏高原的形成具有非常重要的意义.沱沱河组上部的孢粉化石组合以被子植物花粉为主, 且主要为三沟和三孔沟类, 包括栎粉属 (尤其是小栎粉和小亨氏栎粉) 、楝粉属、坡氏粉属和三孔沟粉属等, 具孔类花粉很少, 大部分属种为古近纪常见分子;组合中出现少量鸡爪勒粉属、唇形三沟粉属、山萝卜粉属、管花菊粉属等草本植物花粉;并含有零星古老类型的成分, 如克拉梭粉属、五边粉属和江汉粉属;裸子植物花粉含量低, 蕨类植物孢子零星.基于孢粉组合特征分析, 认为沱沱河组上部的地质时代为始新世中晚期, 为进一步完善了该区新生代地层系统提供了新的依据. 

Sporopollen Assemblage from the Totohe Formation and Its Stratigraphic Significance in the Tanggula Mountains, Northern Tibet

The Cenozoic fluvial redbeds are widely exposed in the Tanggula mountains. Dating these!redbeds can provide very important data for understanding the geological history of the Tibetan plateau. The sporopollen assemblage found from the upper part of the Totohe formation are characterized by the dominace of angiospermous pollen,most of the sporopollens being the common elements of Paleogene. Among the angiospermous pollen, there are plenty of tricolpate and tricolporate pollen grains of various kind, mainly including Quercoidites(especially Q. minutus, Q. microhenrici), Meliaceoidites, Pokrovskaja, and Tricolporopollenites, etc., and the porate pollen is very low in quantity. There is a small amount of herbaceous pollen, such as Scabiosapollis, Labitricolpites, Randiapollis, and Tubulifloridites, as well as sporadic old pollen in these assemblages, such as Classopollis, Pentapollenites, and Jianghanpollis. The quantity of gymnospermous pollen is not high, and the pteridophyte spore is sporadic in the assemblage. Based on the analysis of the characteristics of the sporopollen assemblages, we conclude that the geological age of the upper part of the Totohe Formation is middle and late Eocene, which can provide new basis for further improvement of the Cenozoic stratigraphic system in the Tanggula mountains, northern Tibet.