Studies On Insect Fossils From The Miocene Of Northwestern Qaidam Basin And Its Geological Significance

Qaidam Basin, which islocated in northern the Qinghai-Tibet Plateau, is a large Cenozoic basin. Analysing on the fossils from Qaidam Basin in the Cenozoic can be used for deducing the environmental changes caused by the uplifting of the Qinghai-Tibet Plateau. And it might provide the paleontological proof for geological movement of Qinghai-Tibet Plateau. The insects have the most closely relation with the environmental changes. The species and numbers of insects can be affected by the forest ecosystem growth and development influnced by the environmental changes. The co-evolution of insects and the plants living in the same environment are mutually alternate. And the research on insect fossils is one ideal way to study palaeoenvironment. The reconstruction of palaeoenvironment in the study area, based on investigating the fossil insects which collected from northwestern Qaidam Basin in the Cenozoic, was carried out in this paper. And the Miocene environmental characteristic of the Qaidam Basin was discussed.There are all eight insects fossils collected from Qaidam Basin in the Miocene, including five adult specimens, two larval specimens, and one pupa specimen. These fossils belong to two orders, four sub-orders, five families, six genera and eight species. Adult specimens were identified as Aedes Qaidamica sp. nov.; Syrphus qaidamicus sp nov.; Agromyza qaidanica sp. nov.; Tetrastichidae qaidamican sp. nov. and Megalodontidae gen. et sp. indet.. Larval specimens were identified as Culicidae gen. et sp. indet. and Bibionidae gen. et sp. indet.. The pupa specimen was Muscidae Bibionidae gen. et sp. indet..Comparsion between the fossil and extant insect spices, analyses of insect assemblages in different living conditions have been done. It suggested that fossil insects lived near a lake with water level changing in different seasons; the grass developed at edge of the lake; alinization occoured and the forest was far from the lake in the Miocene Qaidam Basin.