Faulting and folding of basement rocks together accommodate convergence within continental orogens, forming complex zones of intraplate deformation shaped by the fault interaction. Here we use the river terraces along the Dongda river to examine the tectonic deformation patterns of the hinterland and the foreland of the eastern North Qilian Shan, a zone of crustal shortening located at the northeast margin of the Tibetan Plateau. Five Late Pleistocene-Holocene terraces of Dongda river are displaced by three major reverse faults: Minle-Damaying fault, Huangcheng-Ta’erzhuang fault, and Fengle fault, from south to north. Based on displaced terrace treads, we estimated vertical slip rates along the Minle-Damaying fault as 0.7–1.2 mm/a, and along Fengle fault as 0.5–0.7 mm/a. Deformed terraces suggest additional uplift of ~ 0.2 mm/a through folding of the Dahuang Shan anticline. Inhomogeneous uplift of the intermontane basins between the Minle-Damaying fault and the Dahuang Shan anticline indicates a 0.9 ± 0.2 mm/a uplift rate along the Huangcheng-Ta’erzhuang fault. Kinematic modeling of this thrust system shows that deformation propagated northward toward the foreland along a south-dipping 10° décollement rooted into Haiyuan fault at the depth of 20–25 km. This system accommodates 2.7–3.8 mm/a total crustal shortening rate. We suggest this broad thrust belt and the relatively high rate of shortening within this part of the eastern Qilian Shan is as a result of the oblique convergence along a restraining bend of Haiyuan fault system. The elevated shortening rate within this area indicates high potential seismic hazard.

Based on the teleseismic records of the dense broadband seismic array, the crustal anisotropy parameters of the west Ordos block and its adjacent regions were determined with P wave receiver functions. The results indicate that the dominant direction of the fast wave is N-S in the Alxa block, NEE-SWW in north Ordos block, N-S in south Ordos block, and E-W in the Yangtze block. The fast wave direction of crust anisotropy in north Ordos block is distinctly different from the south Ordos block and the Alxa block. The Dabashan thrust fold belt is a visible boundary of crust anisotropy, which implies that the crust anisotropy kept the information of ancient South China block and North China block. Comparing with the direction of the fast wave from the SKS splitting, we tentatively discussed the interaction mode between the crust and mantle. The crust and mantle are decoupled in south Ordos block and coupled in north Ordos block. Combining the results of previous geophysical studies, we presented a crust-mantle interaction model to explain the geophysical observations. The most prominent features of the model are the horizontal eastward expansion of the mantle material in the southern Ordos and the vertical upwelling of the mantle material in the northern Ordos. The different modes of movement of the mantle material led to the deep contrasting structures of north and south Ordos, including the crust anisotropy. The mantle upwelling also implies that north Ordos block might be currently experiencing craton destruction.

Northward indentation of the Qaidam Basin (QB) and southward underthrusting of North China Craton (NCC) lithospheric mantle beneath the Qilian Shan (QLS) are two frequently-cited geodynamic modes for interpreting the evolution of the northeastern Tibetan Plateau. We here aim at understanding the roles of these two dynamic processes in crustal deformation and how they interact during plateau growth in the NE margin by using sandbox experiments that simulate the convergence of the QB-QLS belt through indentation and underthrusting type of boundary conditions individually, alternately or synchronously. Results illustrate that 1) Underthrusting beneath the QLS favors a gently-tapering, one-sided thrust wedge only above the downgoing slab. 2) Indentation of the QB promotes the occurrence of doubly vergent convergent belts with two oppositely-tapering thrust wedges spreading from the slab boundary. 3) Diverse convergence histories lead to distinct deformation patterns for the modelled convergent belts. However, only when indentation and underthrusting occurred synchronously, the modelled thrust wedge resembles current QB-QLS belt in terms of growth sequence, wedge geometry and deformation localization pattern, indicating that bidirectional compression mode maybe the best approximation for the late Cenozoic northeastern Tibetan Plateau. Our experiments further reveal that shift of boundary conditions like alternation of geodynamic drivers and encountered foreland buttress, would result in limited changes in uplift rate of individual structures. Instead, switch between different structural evolutionary stages causes more pronounced variations and should be noted when interpreting thermochronologic data from the northeastern Tibetan Plateau.

The deformation pattern and slip partitioning related to oblique underthrusting of the Tarim Basin in the eastern Tian Shan are not well understood because of the lack of interior deformation images. The Baoertu fault (BF) is an E-W-striking, ~350 km-long reactivated basement structure within the eastern Tian Shan. In this study, we quantify its late Quaternary activity based on detailed high-resolution remote sensing image interpretations and field investigations. Three field observation sites along an ~80 km-long fault segment indicate that the BF is characterized by sinistral thrust faulting. Based on surveying of the displaced geomorphic surfaces with an unmanned drone and dating of the late Quaternary sediments using radiocarbon and optically stimulated luminescence (OSL) methods, we estimate a late Quaternary left-lateral strike-slip rate of 1.87 ± 0.29 mm/yr and a N-S shortening rate of 0.26 ± 0.04 mm/yr for this fault. The lithospheric BF acts as a decoupling zone and accommodates the left-lateral shearing caused by the oblique underthrusting of the Tarim block. In the eastern Tian Shan, the oblique convergence is partitioned into thrust faulting across the entire range and sinistral slip faulting on the high-dip basement structure within the orogen. This active faulting pattern in the eastern Tian Shan of sinistral shearing in the center and thrust faulting at both sides can be viewed as giant positive flower structures.