Characteristics of Structural System and Its Implication for Formation Dynamics in Qaidam Basin

Structural analyses and balanced cross-section restoration were jointly used in this paper to investigate the structural system,the tectonic setting and the geodynamic evolution model of the Qaidam basin. Under the common influence of the India plate,the Siberia plate and the Pacific plate,three structural systems developed around the middle rigid block in Qaidam basin,they are the northern Qilian mountain structural system,the southern Kunlun mountain structural system and the western Altun mountain structural system. Each of the structural system contains three thrust structural belts which consists of several main faults and their relevant folds,the sublevel faults and their relevant folds distributed within the thrust structural belts diagonally,and the structural framework of Qaidam basin could be regarded as a superposition of the three great structural system. The basic dynamic setting is that the Qaidam block was compressed by India plate from south to north on the southern margin,resisted by Alxa plate from north to south on the northern margin and sideslip from north China plate on eastern margin and from Tarim plate on western margin. Combining the analysis of balance profile,the basin preliminary dynamic evolution model was established,it is that the Qaidam Basin experienced expansion within the period of Early Jurassic to middle Jurassic and episodic extrusion composited sideslip within the period of Cenozoic,and the structural framework of Qaidam basin was formed within Quaternary.