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拉萨地块下二叠统拉嘎组是一套与冈瓦纳地区晚古生代大规模冰川作用有直接联系的沉积地层,作者在西藏申扎地区的拉嘎组中分析出孢粉化石,说明早二叠世蕨类植物孢子和裸子植物花粉的出现与冈瓦纳大陆冰川消退事件有密切联系.该套孢粉组合中蕨类植物孢子含量远低于裸子植物花粉含量,双囊具肋花粉和单囊花粉含量最高,Hamiapollenites与Striatoabieites两属地位尤为突出;组合中蕨类植物孢子含量虽低但分异度较高,单气囊花粉Cordaitina所占比例较大,双囊具肋花粉Hamiapollenites,Striatoabieites,Protohaploxypinus的种数很多,可建立Hamiapollenites-Striatoabieites组合.值得注意的是,除了少数“冈瓦纳型”分子Parasaccites obscurus,P.cf.radiplicatus,Plicatipollenites indicus的存在外,其余含量极高的分子则可与新疆北部早二叠世孢粉组合相对比,说明早二叠世冈瓦纳和亚安加拉共有某些植物类群的可能性是极大的.这类孢粉组合在早二叠世冰海相沉积物中的出现表明,拉萨、南羌塘等地块由冈瓦纳北缘向华夏区转换的过程中,微植群发生的混生可能比古动物群响应的更早,至少在早二叠世的冰期末或冰期结束后就已经发生了.
The Lhasa block, the Lower Permian Raga Formation, is a set of sedimentary strata directly linked to the Late Paleozoic glaciation in the Gondwanaland. The authors analyzed sporopollen fossils in the Laga Formation in the Xainza area of Tibet, The emergence of pollen of Permian spores and gymnosperms is closely related to the subsidence of the glacier in the Gondwanaland Continental. The spore content of ferns in the sporopollen assemblage is much lower than that of gymnosperms, The highest content of single-celled pollen was found, and the two genera of Hamiapollenites and Striatoabieites were particularly prominent. The spore content of ferns in the combination was low but their differentiation was high. The percentage of single-pollen Cordaitina was larger than that of Hamiapollenites and Striatoabieites, There are many species of Protohaploxypinus that can establish the Hamiapollenites-Striatoabieites combination.It is noteworthy that, in addition to the presence of a few “Gondwana” molecules Parasaccites obscurus, P.cf.radiplicatus and Plicatipollenites indicus, the extremely high content of other molecules It can be compared with the Early Permian sporopollen assemblage in northern Xinjiang, indicating that some plant groups were shared by Gondwana and Angara in the Early Permian Is extremely probable.The occurrence of these sporopollen assemblages in the Early Permian ice-sea sediments shows that in the process of the conversion of the Lhasa and South Qiangtang blocks from the Gondwana to the Huaxia region, The micro-flora may have mixed earlier than the paleoanthropic response, at least at the end of the Early Permian ice age or after the end of the ice age.