290 / 2019-08-23 14:13:39

Constrain the time of collisions on the eastern margin of Pangea using tetrapod records

Permian,North China Block,South Chinese Block,Indo-China Block

Paleogeographic maps are reconstructed by the methods such as paleomagnetism, basin analysis, biogeography, geochemistry, but the time of collision of plates is mainly deduced from tectonics, paleomagnetism combining with dating. Due to some fundamental data are absent and some are conflict, different team proposed different time for the time of collisions, and produced different maps for the same ages. The migration of the tetrapods was controlled by the movement of plates, and the terrestrial tetrpods can provide direct evidence for the connection of lands. The early terrestrial tetrapods of China (Carboniferous—Triassic) can be used to constrain the time of collisions on the eastern margin of Pangea.
The oldest tetrapod record is Urumqia liudaowanensis from Lucaogou Formation of Xinjiang, Cisuralian (291–284 Ma) in age. It confirmed the presence of the land bridge between the Kazakstan collage system and the North China block (NCB), same as the current reconstructions. The Dashankou Fauna from Yumen, Gansu is regarded as Roadian or Wordian in age. So this area had connected to the Baltica craton via Kazakhstan block and became part of Pangea at least by early Guadalupian (~270Ma).
Recent years, the tetrapods were reported from the Purple Claystone Formation of Laos and are the latest Permian or earliest Triassic in age. Our work shows they are closely related to the tetrapods from China, and should be latest Permian in age. It shows the NCB was connected to the Indo-China Block in land by that time, so the collision of NCB AND South China Block is in Permian rather than Triassic.