Abstract:

Nanyishan-Jiandingshan area is in the northwest of Qaidam Basin, and it is adjacent to Aerjin slope zone. A series of NW trending tight anticlines and the gentle synclines in the between constitute the structural framework of the area. Research shows the study area underwent mainly two stages of deformation since Mesozoic: (1)during Early to Middle Jurassic, the area was mainly dominated by extension and featured by the formation of the dustpan-like faults; and (2)during Shizigou Period to present, the area has been controlled by the SW-NE trending compression. The formation of Jiandingshan anticline started in Shizigou Period, and the underlying early depression-controlling normal fault was inverted because of compression, forming large scale fault-propagation folds. The formation of Nanyishan anticline started in Qigequan Period, which was formed by a shallow anticline superimposed on a deep one, the deep anticline was a large scale fault-propagation fold, while the shallow one was a box anticline similar to detachment fold which was formed above the fault by the opposite thrust of two step thrust faults which forming Type-I triangle zone. The forms of Nanyishan anticline and Jiandingshan anticline are relatively integrated, the formation time of structure matches the time of maturity and migration of oil and gas well, indicating very favorable oil and gas exploration prospect.

Key words: structural feature, fault-related fold, growth strata, deformation time, Nanyishan-Jiandingshan area, Qaidam basin