Paleomagnetic Chronology and Record of Himalayan Movements in the Longgugou Section of Gyirong‐Oma Basin in Xizang (Tibet)

Abstract

Abstract The Neogene sedimentary environment in the Longgugou section of the Gyirong‐Oma Basin as studied by means of paleomagnetic chronology. By correlation, the Cenozoic fault basin on the north slopes of Himalayas had been formed 7.2MaB.P. ago, and then shrank and died at 3.2MaB.P. It marked that the region around the Himalayas experienced strong uplift in the time span from 7.2 to 3.2MaB.P. The age of Hipparion fossil buried in the Longgugou section is about 7.0~6.7MaB.P. In comparison with Hipparion fauna in North China, they should have similar geographic and climatic environment. Because of the continual movement of the Himalayas, the fault basin downwarped and attained the biggest area in the time span from 5.9 to 3.6MaB.P. With the uplift of the Tibetan Plateau and the subsidence of North China Plain, the terrain in western China became higher than that in eastern China, the climatic environment experienced strong differentiation between eastern and western China. Since 3.6MaB.P. rivers in the western part dissected the basins due to strong uplifting of Tibet, Gyirong‐Oma lake basin shrank from 3.2MaB.P., died completely in 1.7MaB.P., and then stepped into the stage of erosion and dissection.