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Zuza A.V.,University of California at Los Angeles | Cheng X.,Zhejiang University | Cheng X.,Research Center for Structures in Oil and Gas Bearing Basin | Yin A.,University of California at Los Angeles | Yin A.,China University of Geosciences
Geosphere | Year: 2016

Competing models that account for the construction of the Tibetan Plateau include continental subduction, underthrusting, distributed shortening, channel flow, and older crustal-structure inheritance. Well-constrained estimates of crustal shortening strain serve as a diagnostic test of these plateau formation models and are critical to elucidate the dominant mechanism of plateau development. In this work we estimate the magnitude of Cenozoic shortening across the northern Qilian Shan-Nan Shan thrust belt, along the northeastern plateau margin, based on detailed analysis and reconstruction of three high-resolution seismic reflection profiles. By integrating surface geology, seismic data, and the regional tectonic history, we demonstrate that this thrust system has accumulated > 53% Cenozoic strain (~50 km shortening), accommodated by several south-dipping thrust faults. Based on the observed strain distribution across northern Tibet, including lower strain (30%-45%) within the interior of the Qilian Shan-Nan Shan thrust belt, we suggest that a combination of distributed crustal shortening and minor (<250 km) southward underthrusting of the Asian lithosphere is responsible the development of the northern Tibetan Plateau. Focused shortening along the Qilian Shan frontal thrust system accommodates much of the present-day convergence between Tibet and North China, which implies that the northern plateau margin may have developed in a similar manner to that of southern Tibet through Himalayan- style continental underthrusting. We also argue that the Qilian Shan- Nan Shan, North Qaidam, and Qaidam Basin thrust systems have absorbed a minimum of 250-350 km north-south Cenozoic shortening, which is double the commonly cited value of ~150 km. © 2016 Geological Society of America.

Lin X.,Zhejiang University | Lin X.,Research Center for Structures in Oil and Gas Bearing Basin | Wyrwoll K.-H.,University of Western Australia | Chen H.,Zhejiang University | And 3 more authors.
International Journal of Earth Sciences | Year: 2015

The Sikouzi Section is located towards the northern limits of the East Asian summer monsoon, providing the opportunity of placing the stratigraphic record into the context of the East Asian summer monsoon history. We present here the results of the details of the sedimentology of the Neogene succession of the section and use these to provide insights into the evolving history of the East Asian summer monsoon. The record is marked by a strongly expressed early Miocene lacustrine phase. A well-defined evaporate bed defines the top of the lacustrine succession, marking the onset of more arid conditions during the middle Miocene. The overlying succession is dominated by a series of alluvial packages, extending into the late Pleistocene with varying stratigraphic architectures and including a subordinate lacustrine component. Given the regional setting, the onset of drier conditions during the middle Miocene must relate to a downturn of summer monsoon activity. We focus on the question: what ‘forced’ this palaeoclimate event? Earlier biostratigraphic work places the explanation of this change into the context of the global-scale middle Miocene climate reorganisation. Here we explore this question in the context of regional-scale climate dynamics and propose that the onset of drier conditions over the study area was a response to atmospheric subsidence driven by circulation changes related to the growth of the Tibetan Plateau. © 2015 Springer-Verlag Berlin Heidelberg

Lin X.,Zhejiang University | Lin X.,Research Center for Structures in Oil and Gas Bearing Basin | Lin X.,University of Western Australia | Chen H.,Zhejiang University | And 4 more authors.
Journal of Asian Earth Sciences | Year: 2010

The Cenozoic evolution of the Liupan Shan, situated at the northeast of the Tibetan Plateau, will provide constraints to test the models and mechanisms of the evolution of the plateau. In this contribution, the Sikouzi section, at the east of the Liupan Shan, has been selected to study Liupan Shan's uplift history. At around 9.5 Ma, constrained by the magnetostratigraphy, the sediment and depositing architecture characteristics obviously changed. Synchronously, flow direction changed from E → W to W → E, and accumulation rate increased to more than double. All these evidences suggest that the Liupan Shan initiated uplifting at around 9.5 Ma. Subsequently, a stage of intense uplift happened during 8.2-7.3 Ma, indicated by the apatite fission-track (AFT) data across the Liupan Shan. Regional comparison indicates that this stage of uplift is not only with local but also regional significance. The Miocene uplift of the Tibetan Plateau triggered the intensification of the East Asian Monsoon and Asian intercontinental aridity, which has been implied by the pollen results of the Sikouzi section. © 2009 Elsevier Ltd. All rights reserved.

Lin X.,Zhejiang University | Lin X.,Research Center for Structures in Oil and Gas Bearing Basin | Chen H.,Zhejiang University | Chen H.,Research Center for Structures in Oil and Gas Bearing Basin | And 8 more authors.
Acta Petrologica Sinica | Year: 2010

On the basis of previous studies of SHRIMP U-Pb chronology, geochemistry, metamorphic temperature/pressure conditions and tectonic setting, fission-track thermochronology has been conducted in this study to determine the exhumation of the basic granulite. Zircon fission-track shows Triassic and apatite fission-track shows Late Cretaceous to Early Cenozoic ages. Thermal history modeling of the fission-track data, combined with previous studies, indicate that the basic granulite was exhumed to the upper crust under about 7.8km in Triassic. From Late Cretaceous to Early Cenozoic (around 100 ∼50 Ma), the basic granulite, meta-diabase and the wall rock gneiss were cooled to the blocking temperature of apatite fission-track, which was about 3.5km below the surface. From approximately 50 to 15 Ma, they stayed at the partly-annealed zone of apatite fission-track, about 1.7km below the surface. Since about 15 Ma to present, they ware uplifted and denudated to the surface.

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