Crustal-scale wedge tectonics at the narrow boundary between the Tibetan Plateau and Ordos block

Abstract The Tibetan plateau is bounded in part by cratonic blocks, and in part by tectonothermally younger and weaker crust. How the Tibetan plateau interacts with bordering non-cratonic crust is a continuing debate, whether the plateau is currently enlarging its area, and if so, whether by thrusting or by lower-crustal flow, or both. The gently sloping northeastern margin of Tibet has been inferred to incorporate a lower-crustal channel flow outward towards the Ordos block that is a part of the North China Craton. We calculated receiver functions using teleseismic waveforms recorded by a dense nodal seismic array crossing from the Longxi basin of northeastern Tibet across a transition zone marked by the Liupan Shan (mountains) into the Ordos block. Our image shows the Longxi upper crust overthrusts onto the Ordos block building the Liupan Shan, and the Longxi lower crust underthrusts beneath the Ordos forming a 10-km thick crustal root. The Ordos crust forms a crustal-scale wedge inserted into the Longxi crust, and deformation is limited to a narrow zone of