Age revision of the Xiala Formation in Konglong area, Nangren County, Tibet, and its constraints on the sedimentary evolution of the Gangdese belt in the Middle and Late Permian

The existence of the uplift event in the Gondese belt during Late Permian is still long debated.On the basis of the detailed stratigraphic and paleontological works, this paper reports a continuous marine sedimentary section found in Konglong area, Nangren County, Tibet.The Xiala Formation is divided into two lithologic parts.The lower part mainly consists of bioclastic limestone and microcrystalline limestone, and the coral samples Wentzelella typical, Neokueichowpora gemina and fusulinid samples Rugososchwagerina, Neoschwagerina sp., Nankinella sp. were found in this part.The age of the lower part of the Xiala Formation is the Middle Permian Wordian to Capitanian.The lower part mainly consists of nodular limestone and crystalline limestone.The conodont specimens found in this part are grouped into Neogondolella cf. leveni, Clarkina orientalis, Clarkina longicuspidata and Hindeodus typicalis, they are from the Wuchiapingian to Changhsingian.The age of the Xiala Formation was redefined to the Middle Permian Ward to Late Permian Wujiaping, and the age of the topmost part of the Xiala Formation may extend to Changhsingian stage.We conclude that the study area was a continuous marine depositional environment during the Middle Permian-Late Permian period, and there was no tectonic uplift event at the turn of the Middle Permian and the Late Permian.The view that western Gangdise was a land during the Late Permian and Triassic should be reconsidered.