Abstract:

Altyn Tagh fault has experienced at least three periods strike-slip and thrust movement since 100-85 Ma, 40-25 Ma, 10-8 Ma respectively. In this paper, the author carried out joints data measurements in the Meso-Cenzoic strata of southwest Qaidam basin, and then deduced the stress direction applying the strata recovery technique to different formations. The results suggest that the effect of Altyn Tagh fault to southwest Qaidam basin is difference in various periods, that is, it is very narrow just along Altyn Tagh Mountains during Late Cretaceous, while it enlarge gradually to Ganchaigou anticline and Youshashan anticline during the Eocene Shangganchaigou epoch and Miocene Xiayoushashan epoch for two stages of strike-slip and thrust movement of Altyn Tagh fault. Perhaps, the structure joint phenomenon of Qaidam basin has some relationship with the multi-phase thrust of Tibet Plateau causing Altyn Tagh fault re-active at that time. Therefore, it is necessary to consider three strike-slip movements of Altyn Tagh fault in the exploration of petroleum produce of southwest Qaidam basin.

Key words: Altyn Tagh fault, Qaidam basin, structure, joints