Analysing the provenance changes of synorogenic sediments in the Turpan‐Hami basin by detrital zircon geochronology is an efficient tool to examine the uplift and erosion history of the easternmost Tian Shan. We present detrital zircon U‐Pb analysis from nine samples that were collected within marginal lacustrine Middle‐Late Jurassic and aeolian‐fluvial Early Cretaceous strata in the basin. Middle‐Early Jurassic (159–172 Ma) zircons deriving from the southern Junggar dominated the Middle Jurassic sample from the western Turpan‐Hami basin, whereas Permian‐Carboniferous (270–330 Ma) zircons from the Bogda mountains were dominant in the Late Jurassic to Early Cretaceous samples. Devonian‐Silurian (400–420 Ma) and Triassic (235–259 Ma) zircons from the Jueluotage and Harlik mountains constituted the subordinate age groups in the Late Jurassic and Early Cretaceous samples from the eastern basin respectively. These provenance transitions provide evidence for uplift of the Bogda mountains in the Late Jurassic and the Harlik mountains since the Early Cretaceous.

: The timing of onset of deposition of the Lulehe Formation is a significant factor in understanding the genesis of the Qaidam basin and the evolution of the Tibetan Plateau. Here, we describe a detailed magnetostratigraphic and magnetic fabric study of the middle and lower parts of the Lulehe Formation. A total of 234 samples were collected from 117 sites throughout a thickness of almost 460 m of fluvial and lacustrine deposits at the Xitieshan section in the northeastern Qaidam basin. Out of these sites, 94 sites yielded well‐defined characteristic remanent magnetization components by stepwise thermal demagnetization and were used to establish the magnetostratigraphy of the studied section. Based on correlation with the geomagnetic polarity timescale, the studied section spans the period from 53.8 Ma to 50.7 Ma. Our results show a three‐fold decrease in sedimentation rates as well as marked change in facies from braided river to delta and shore–shallow lake around 52.6 Ma, which suggests tectonic uplift of the northeastern Qaidam basin margin ridge was rapid at the onset of formation of the Qaidam basin and subsequently weakened after 52.6 Ma. The anisotropy of magnetic susceptibility results indicate that tectonic compression stress had reached the northeastern Tibetan Plateau by the early stages of Indo–Eurasian plate collision and that the direction of stress in the study area was NE–SW. Furthermore, a weakening of tectonic compression stress around 52.6 Ma is consistent with sedimentary records. The age of initial deposition of the Qaidam basin (around 53.8 Ma) was almost synchronous with that of the Qiangtang, Hoh Xil, Xining, and Lanzhou basins, which implies that stress was transferred rapidly through the Tibetan Plateau during or immediately after the onset of Indo–Eurasian collision.

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[1] Better constraints on the uplift history of Tian Shan will increase our understanding of both mountain building processes and deformation patterns related to the India-Asian collision. Anisotropy of magnetic susceptibility (AMS) holds great potential to track variations in tectonic strain, which is ultimately responsible for mountain uplift. Here we present an AMS record, spanning the interval of 28-4 Ma, from the fluviolucastrine Jingou River section in the Tian Shan foreland. Rock magnetic measurements show that the AMS are dominated by antiferromagnetic hematite and some paramagnetic minerals, both of which have a crystallographic preferred orientation, and therefore the AMS sequence may be applied to reconstruct tectonic strain. Although the principal minimum (K min ) direction is nearly perpendicular to the bedding plane, indicative of a predominantly sedimentary fabric for the section, the tightly grouped principal maximum (K max ) parallel to the fold axis suggests that the section was subject to an embryonic deformation at least since the Late Oligocene. The K max direction is most likely associated with the N-S strain caused by the India-Asian collision. During the intervals of 23.3-20.0 Ma and 16.5-14.0 Ma, the strain markedly increased as evidenced by more tightly grouped K max directions and K min largely distributed within a clear N-S girdle. These two intervals are accompanied by changes in sedimentary facies (higher energy conditions and doubled sedimentation rates), and are interpreted as the periods when the Tian Shan experienced significant uplift. A conceptual model is tentatively proposed to reconcile various timings for the Tian Shan uplift.