Discovery of Cretaceous compressional structure in northern margin of Qaidam basin and its geological significance

On the basis of the detailed geological interpretation of seismic profile in northern margin of Qaidam basin, combined with the result of field geological survey, the author concluded the studying area converted from the Jurassic NE-SW trending extensional structure framework to the NEE-SWW trending compressional structure framework during the Cretaceous Period, which formed the NNW trending fault-related folds and inverted structures, the nature of northern Qaidam basin is compression-depression basin. The variation of sedimentary rhythm, lithology and thickness of Cretaceous System and the variation of its contact with overlying and underlying strata from conformity to disconformity to conformity are mainly affected by the spatial and temporal variation of the intensity of activity of syn-tectonic fault-related folds and inverted structures. During the Cretaceous Period the deformation features of northern margin of Qaidam basin differed greatly from those basins in the East of China which indicated that structural evolution of the West of China and the East of China were controlled by different tectonic regimes, the NEE-SWW compression in northern margin of Qaidam basin during the Cretaceous Period were possibly related with the collision between the Gangdise landmass and the Eurasian continent in the Tethyan tectonic domain.