Structural Coupling Between the Qiman Tagh and the Qaidam Basin, Northern Tibetan Plateau: A Perspective From the Yingxiong Range by Integrating Field Mapping, Seismic Imaging, and Analogue Modeling

Abstract

AbstractThe Qiman Tagh and the Qaidam Basin within the northern Tibetan Plateau are contrasting in geomorphological, geological, and geophysical features. The Yingxiong Range is the largest anticlinal belt in the SW Qaidam Basin and holds a key in understanding the relationship between the above two tectonic units. Herein, we investigated the geometry, shortening, timing and mechanism of the structural deformation across the Yingxiong Range by integrating field mapping, interpretation of 3‐D/2‐D seismic reflection data and analogue modeling. The structural interpretation demonstrates that the Yingxiong Range is primarily controlled by NE‐directed basement‐involved reverse faults. These faults likely sole into a décollement layer at depth of ~15 km through the excess area‐depth analysis. This pattern is complicated by the development of a local salt layer that decouples the deformation of underlying and overlying strata, as indicated by analogue modeling. Deformation initially occurred at ~8.1 Ma but strengthened at ~2.5 Ma, with total shortening up to ~5 km in the NW part but decreasing to <2 km to the SE. Together with published results, our findings revealed an NE‐directed thrust system involving the Qiman Tagh and the SW Qaidam Basin, with the Yingxiong Range as the front of this system. We further inferred that this NE‐directed thrust system in the upper crust, together with the previously identified SW‐directed deep reverse fault offsetting the Moho, may form a southwestward tapering tectonic wedge, which likely results from the heterogeneity of lithospheric mantle between the Qaidam Basin and the Qiman Tagh‐East Kunlun Shan.