The discovery of Paleogene insect fossils in eastern Nima Basin, Tibet, and its implication for paleoclimate

Since the Cretaceous period, thick terrigenous clastic rocks interbedded with limestone strata have been deposited in the Nima Basin, northern Tibet, but the deposition age is still debatable due to the lack of fossil evidence.Recently, a lot of insect, fish and plant fossils were discovered from the fine clastic rocks interbedded with limestone strata in the Saibu Co area in the east of the Nima Basin.The insect fossils mainly consist of Aquarius lunpolaensis, which is consistent with the morphological characteristics of the species reported in the Dayu area in the Lunpola Basin and the Jiangnongtangga area in the west of Nima Basin, indicating that this set of strata was Late Oligocene Dingqinghu Formation rather than the Jingzhushan Formation or Niubao Formation.In addition, Aquarius lunpolaensis mainly existed in warm and humid environment at low elevation area and, in combination with tropical to subtropical fish and plant fossil assemblage in the Late Oligocene strata in the Lunpola and Nima basins of central Tibet found in recent years, the authors argue for a warm and humid lowlands environment in the Late Oligocene period in the central Tibet rather than high and cold climate as used to be considered.