Abstract:

The subsidence history and the balanced cross sections are applied in this paper. The former is used for researching the up and down history in the vertical direction, and the latter is used for researching the extensional and compressional history in horizontal direction. The analysis of the quantitative research result with the regional geology background proves that tectonic evolution can be divided into Mesozoic(J-K)and Cenozoic(start from E₁₊₂)phases from Mesozoic in the Northern Margin Region of the Qaidam Basin. In the Mesozoic evolution phase(J₁-J₂), the subsidence history curve has the quality of extensional basin, and the restoration result of the balanced cross sections has the quality of extension, too. The maximal extension ratio of it is 1.9% and the rate is 19.48 m/(Ma·km). The extension stress field is aroused by the difference of the Qaidam plate and the adjacent plates-movements. Besides, because of the self-circumgyrate of the Qaidam plate, the subsidence rates and the extension ratios are different in the three sags. In the Cenozoic evolution phase, the subsidence curve has the character of the foreland basin, and the restoration result of the banlanced cross sections has the quality of compression, too. The maximal compression ratio of it is 4.96% and the rate is 14.09 m/(Ma·km). The  compression stress field is aroused by the collision between the India plate and Eurasia plate. Furthermore, because of the Himalayan movement, the subsidence rates and extension ratios have the character of the graduate “episode ”.

Key words: the northern margin region of the Qaidam Basin, subsidence history, balanced cross section, basin analysis, back-stripping