The stress field of Late Mesozoic-Cenozoic tectonics in the northern Qaidam basin, Northwest China: Evidences from the analysis of joints data

The tectonic evolution of Qaidam basin, especial on the Mesozoic and the Cenozoic period, is still in debated. In order to determine the stress field of the northern Qaidam basin and to discuss the tectonic evolution of this area in the Mesozoic-Cenozoic, we carried out joints data measurements from sections of Lenghu No.0, No.4, Eboliang and Jielusu. We then deduced the stress direction applying the strata recovery technique to the different formations. The results suggest that the northern Qaidam basin mainly experienced E-W compression after the Middle-Late Jurassic, which is in accordance with previous results. Following the track on Jurassic strata we can conclude on NW-SE compression since the Early Cretaceous and on S-N compression after the Late Cretaceous which made the strata uplift and denudation. From the Eocene Xiaganchaigou epoch to Pliocene Shizigou epoch, northern Qaidam basin stays in a weak condition and accepts stable deposition. After the deposition of the Shizigou Formation, the NW-SE direction stress which caused by the uplift of Altyn Tagh Mountains, strongly affected the Shangganchaigou, Xiayoushashan and Shangyoushashan formations. Obviously, the strongest stress of N-S direction plays an important role to the Shizigou, Shangyoushashan and Xiayoushashan strata, even to the outcrop of Xiaganchaigou, Lulehe formations and Jurassic layer. This event not only destroys the previous petroleum system of northern Qaidam basin, but also is important to the motion and accumulation of petroleum again. Thus, more work related to joint data analysis of other profiles in northern Qaidam basin need to carry out, and it is signification to guide the exploration of the oil and gas resources in the Qaidam basin.