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The India-Eurasia convergence since early Cenozoic has established the Tibetan Plateau and the Circum-Tibetan Plateau Basin and Orogen System (CTPBOS). When and how the convergence-driving strain has propagated into the CTPBOS is of significant importance in deciphering the growth process of the Tibetan Plateau. In this study, we conduct a structural analysis of the West Kunlun-southern Junggar transect along the NW margin of the Tibetan Plateau to establish the deformation propagation and through this to determine the plateau growth processes. The results suggest a two-phase deformation mode. The first stage features deformation confined in pre-existing weak zones like the West Kunlun orogen, Buchu Uplift and Tian Shan orogen during Paleogene, in which the intracontinental strain was speculated to be mainly consumed by shortening of these weak zones. The second stage is characterized by deformation propagating into foreland regions since early Miocene, in which shorting along foreland fold-and-thrust belts of a scale of tens of kilometers and decreasing basinwardly plays a key role in absorbing intracontinental strain. We suggest that this two-phase deformation mode possibly reflects a shift of governing mechanism of the expansion of the Tibetan Plateau from a rigid-block manner to a critical wedge taper style.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

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A key issue in the Cenozoic evolution of the Tibetan plateau is the geodynamic drivers for north‐trending rifting in southern Tibet. Recent studies have demonstrated an eastward propagation pattern for rift initiation, but the along‐strike variations remain poorly resolved. Two models that predict different north‐south rift kinematics include northward underthrusting or southward tearing of the Indian lithospheric slab, predicting a northward or southward propagation trend of individual rifts along strike, respectively. The Yadong‐Gulu rift (YGR) is an ideal case to investigate this issue due to its long strike length (∼500 km) and location above proposed slab‐tear structures. Here, we compile constraints on both rift initiation and acceleration, and report new apatite fission track and (U‐Th)/He thermochronological data along the southern segment of YGR. Our main findings are as follows. First, the rifts west of the YGR initiated simultaneously along strike, which we suggest is at odds with predictions of either slab‐tear or slab‐underthrusting models. However, most of these rifts show a northward younging pattern in rift acceleration, which may be governed by low‐angle Indian slab underthrusting released by slab tearing. Second, the initiation timing of the Yadong rift is constrained at ∼13–11 Ma. Combined with published constraints along strike, we demonstrate a clear northward propagation in rift initiation along the YGR. This kinematic pattern may be affected by its orientation of the most oblique northeast‐trending among all rift systems or the outward expansion of the Himalayan arc.