Lateral growth, linkage and driving force of anticlines in the western Qaidam Basin, Northern Tibetan Plateau

Abstract

In fold-and-thrust belts, folds usually grow laterally, and connect with neighboring folds to form larger structures. Whilst these processes significantly impact both the surface morphology and subsurface structures, there remains a gap in understanding the deep deformation involved in lateral growth and linkage of folds. To address this issue, our study focused on the northwestern Qaidam Basin hosting a series of well-exposed NW-SE-trending Cenozoic anticlines. We conducted a comprehensive analysis of the lateral growth and linkage patterns along with their subsurface structures of the anticlines, based on high-resolution remote-sensing images and seismic reflection data. Our investigation reveals that the anticlines are primarily décollement folds, with minor influence from basement-involved reverse faults. They have grown through lateral lengthening from their nuclei, with a generally faster propagation rate toward the southeast. This growth pattern is likely driven by the southeastward decrease in strain rate, coupled with the influence from southeastward tilting of the basement and topography in the Qaidam Basin. We identify six types of lateral linkage among anticlines in the Qaidam Basin: linear linkage, linear repulsion, oblique linkage, overlapped linkage, oblique non-linkage, and triple linkage. Notably, our study reports, for the first time, instances of linear repulsion and overlapped linkage, characterized by abnormally large distance to wavelength ratios. The development of linear repulsion is associated with the buried basement-involved fault between linked anticlines, whereas that of overlapped linkage likely results from rapid lateral growth of anticlines due to intense wind erosion. Moreover, our findings indicate that the en echelon-like distribution and arcuate shapes of the anticlines in the Qaidam Basin primarily stem from the lateral growth and linkage of the short-axis anticlines, rather than inferred basement strike-slip shears. The underlying driving force is the compression from the Qiman Tagh-East Kunlun Shan and the South Qilian Shan to the south and north, respectively. Our study underscores the interplay of décollements, basement-involved faults and erosional processes in shaping the diverse growth and linkage patterns of anticlines in fold-and-thrust belts.