The discovery of sporopollen fossiles bearing Lower Permian Glacio-marine sequences of Xainza area, Tibet

Abstract

The Lower Permian Lagar Formation on the Lhasa Terrane is a set of glacio-marine sequences directly related to the Late Palaeozoic Gondwanaland glaciation. The sporeopollen fossils reported for the first time in the Largar Formation in this paper suggested that the appearence of Early Permian pteridophyta spores and gymnosperm pollens have close connection with the Gondwanaland deglaciation. In the palynofloras assemblage of the Lagar Formation, content of the gymnosperms pollens is much higher than that of the pteridophyta spores even if the latter has high diversity. In the gymnosperms pollens, it is dominated by rib-bisaccate pollen and monosaccate pollen. They are dominated by the genera <italic>Hamiapollenites</italic>, <italic>Striatoabieites </italic>and <italic>Cordaitina</italic> respectively. Besides, the species of <italic>Hamiapollenites</italic>, <italic>Striatoabieites</italic>, <italic>Protohaploxypinus</italic> also have large quantity, so the assemblage <italic>Hamiapollenites</italic> <italic>Striatoabieites</italic> can be established. It is worth noting that the highly content elements of palynofloras could be compared with Lower Permian palynofloras of North Xinjiang excepted for a few typical “Gondwana-”elements such as <italic>Parasaccites obscurus</italic>, <italic>P</italic>. cf. <italic>radiplicatus</italic> and <italic>Plicatipollenites</italic> <italic>indicus</italic>. It suggests that there was a common Early Permian palynofloras between Gondwanaland and Sub-Angara. Such an interesting palynofloras links between the blocks from the north hemisphere and that of south hemisphere may have suggested that the mixing of palynofloras began sooner after the deglaciation. And, the mixing of palynofloras was ealier than the paleobiogeograhic change of marine faunas occurred in the South Qiangtang and Lhasa blocks.