Palynofloras across the Triassic–Jurassic boundary on Qinghai-Tibetan Plateau, Southwest China

The Triassic–Jurassic boundary (TJB) of the Qinghai-Tibetan Plateau is exposed at the Germig Section in southern Xizang (Tibet), Southwest China. This marine TJB succession is well-constrained by ammonite and bivalve stratigraphy, providing a robust chronological framework. Based on the palynofloral assemblages from the Germig Section, we recognized two assemblages, one Rhaetian and one Hettangian. The Rhaetian assemblage is dominated by bisaccate pollen, which shifts across the TJB to a Hettangian Classopollis-dominated assemblage, reflecting a change from a seed-fern/conifer-dominated flora to one dominated by cheirolepids. This palynofloral change has been recognized elsewhere, but appears to be diachronous across Gondwana. This is highlighted by our study, which demonstrates that the characteristic post-extinction cheirolepid forests appeared earlier at lower latitudes.