Ceno-Mesozoic sedimentary and tectonic evolution in the western Qaidam basin

Abstract：Based on an integrated analysis of the surface geological, aeromagnetic, gravity, MT and seismic data from the area of Mangnai to Serteng Mountains in the western Qaidam basin, the authors think that the Qaidam basin is sandwiched between the North Kunlun block and Serteng tectonic belt, including two first-order tectonic units-the Qaidam block and the southern margin of the Qilian block-and four second-order tectonic units-the northern margin of the North Kunlun block, Qaidam basin, Serteng tectonic belt and Suhai lake basin in the south of the Qilian block. The general structure of the basin is marked by the tectonic framework of compressional ramp of the East Kunlun Mountains and the Qilian Mountains toward and subsidence of the central part of the basin. The tectonic style inside the basin is characterized by occurrence of anticlines from the margins to center of the basin, with two limbs mostly starting from reverse faults, developing a tectonic pattern of two faults sandwiching an uplift. The compressional stress mainly comes from SW, and the NE direction acts as a resistance. Under the strong compression from the orogenic belts on both sides, in the Jurassic an atypical foreland basin developed on the southern margin of the Qilian orogenic belt; in the Tertiary, a two-side foreland basin formed between the Qilian orogen and Kunlun orogen; in the Quaternary, the Qaidam basin is a compressional, downwarped basin.