Basement controls on deformation during oblique convergence: Transpressive structures in the western Qaidam Basin, northern Tibetan Plateau

Abstract

The Qaidam Basin, especially its western part, is characterized by numerous northwest-trending folds and faults. Understanding the style and formation mechanism of these structures is crucial for unravelling the deformation of the Qaidam Basin and the broader tectonics of the northern part of the Tibetan Plateau. Based on seismic data, we reconstruct the structural framework of the central part of the western Qaidam Basin, and find that: (1) the structures in this area display positive flower geometries in two-dimensional (2D) seismic profiles and helicoidal shapes in 3D space; (2) these positive flower structures began to develop during the middle to late Miocene (15–8 Ma); and (3) these positive flower structures are controlled by left-lateral basement faults and formed in a random temporal sequence. The left-lateral features represent the strike-slip component of distributed deformation, consistent with published global positioning system and seismicity data for oblique convergence across the north of the Tibetan Plateau. Collectively, they perform the same role as the discrete Haiyuan, Kunlun, and Altyn Tagh faults in adjacent areas.