The Phanerozoic record of Southeast Asia preserves the history of opening and subsequent consumption of the Paleotethyan Ocean and the assembly of continental fragments into Asia as part of the ...broader-scale reconstruction of Pangea. However, uncertainty remains as to which of the many suture zones in Southeast Asia represents the relict of the main ocean, when final ocean closure occurred, and the assembly history of the Eastern Cimmerian and Southeast Asia continental fragments. Our overview of the geological features of the suture zones, the bounding continental fragments and their magmatic, metamorphic and sedimentary records resolves many of these key issues. The sedimentary, biogeographical, structural, lithological, geochemical and geochronological data from the Changning-Menglian, Inthanon and Bentong-Raub suture zones argue for their linkage with the Longmu Co-Shuanghu suture zone in Central Tibet, and together constitute the main East Paleotethyan Ocean relict. The eastward subduction of the ocean resulted in the development of a series of magmatic arc-back-arc basin and continental fragments in Southeast Asia, including, from west to east, the Lincang-Sukhothai-East Malaya arc, the Jinghong-Nan-Sa Kaeo back-arc basin, the Simao/west Indochina fragment, the Luang Prabang-Loei back-arc basin, the south Indochina fragment, the Wusu and Truong Son back-arc basins, the north Indochina fragment, the Jinshajiang-Ailaoshan-Song Ma branch/back-arc basin and the South China Block. Assembly of these fragments resulted in Indosinian high temperature and high pressure metamorphism and related tectonothermal event. Available data indicate a switch from subduction of the main East Paleotethyan Ocean to the collision of the Sibumasu with Simao/Indochina blocks at ~237Ma, with subsequent syn- and post-collisional events at ~237–230Ma and ~230–200Ma, respectively, along the Changning-Menglian, Inthanon and Bentong-Raub suture zones. The timing of initial-, syn- and post-collision events along the Jinshajiang-Ailaoshan-Song Ma suture zone with its record of back-arc basin closure is at ~247Ma, ~247–237Ma and ~237–200Ma, generally ~10Ma older than that along the Changning-Menglian, Inthanon and Bentong-Raub suture zones. Our synthesis of all available data enables establishment of a comprehensive geodynamic model for the East Paleotethyan evolution. This model links the spatial-temporal pattern across Southeast Asia into a series of tectonic events including ocean/back-arc basin opening, subduction/closure, subsequent assemblage and orogenic collapse, along with associated igneous, metamorphic and sedimentary activities.
The uplift processes of the Qilian Shan (northern Tibetan Plateau) play a central role in our understanding of the dynamics of outward and upward growth of Tibet due to sustained convergence of the ...Indian and Asian plates. We employ apatite fission track chronology and geological mapping to reveal the time and pattern of the deformation along the Qilian Shan. Our results indicate that the emergence of the Tuolai Shan in the central Qilian Shan occurred at 17-14 Ma, that northern Qilian Shan thrusting began at 10-8 Ma, and that the Laojunmiao anticline formed ca. 3.6 Ma. Together with previous results that show that uplift of the southern Qilian Shan began in the Oligocene, we suggest that the Qilian Shan has undergone progressively northward expansion in the Cenozoic due to significant crustal shortening driven by Qilian Shan thrust fault systems.
This paper aims to solve the problem of the oxygen cylinder contribution to the overall scattering intensity of the open breathing diver, which is the basis for mastering the accurate prediction and ...identification of the diver. A two-dimensional finite element axisymmetric model of 3D-object with non-axisymmetric excitation is constructed. The numerical solution to the far-field frequency characteristics of the acoustic scattering by the object with different azimuths is obtained by using the acoustic-solid coupling multi-physical interface in frequency domain. The reason and the estimation formula of the bright fringe at the resonance frequency are given. Under the assumption of the linear acoustics, the numerical solution to finite element method (FEM) is taken as the system function, and the linear frequency modulation signal with the same bandwidth is taken as the input signal of the system. The echo simulation in time domain can be obtained based on the convolution theorem. Combining the bright spot mode
Menopause is a stage indicating the end of a woman's menstrual cycles. Metabolic disorders induced by changes in female hormones in postmenopausal period negatively affect the quality of life of ...women. Abnormal lipid metabolism is a common postmenopausal problem, which is often neglected due to its insidious onset, and may lead to obesity, cardiovascular disease, non-alcoholic fatty liver disease and other problems eventually, seriously endangering the health of postmenopausal women. Exercise intervention has proven to be effective in the containment of abnormal lipid metabolism. We reviewed recent advances in postmenopausal changes in E2 and FSH hormones and their influence on lipid metabolism, the effects of different exercise interventions on postmenopausal lipid metabolism abnormalities, and the pathogenesis of lipid metabolism abnormalities caused by postmenopausal hormone changes and the mechanisms of exercise regulation, then summarized that the changes of E2 and FSH hormone levels in perimenopause per
The 900-km-long Yushu-Ganzi-Xianshuihe fault system that separates the Bayan Har and Qiangtang/Chuandian blocks is a primary tectonic structure in central eastern Tibet. Being one of the world's most ...seismically active fault systems, it hosted 12 M>7 earthquakes since the 18th century, and its future seismic risk has been the subject of extensive research over the past two decades. Previous studies have suggested that the western segment of the fault system differs largely from its eastern segment in strain accumulation and release, but the origin of such difference remains unknown. Here we use Sentinel-1 data to produce a complete map of present-day deformation for the entire fault system, in order to explore the along-strike variation in fault slip behaviour. Based on the InSAR deformation map, we solve for fault kinematic parameters including slip rate, locking depth and dip angle using a Bayesian Markov Chain Monte Carlo inversion approach. Slip rate on the Dangjiang-Yushu-Ganzi fault is consistently ∼5–6 mm/yr, only half of that on the Xianshuihe fault. This rate difference originates from nonuniform deformation mechanism within the Bayan Har block, with the western part of the block deforming more rigidly than the eastern part. Both historical and modern earthquake catalogues show that the western fault segment has only recorded M>7 earthquakes whereas the eastern segment has seen many small-to-moderate ruptures in addition to large earthquakes. These observations imply that the western fault segment may be more structurally mature than the eastern segment, which agrees with the long-term fault propagation as indicated by geochronological data and fault geometrical complexities. We calculate the seismic moment deficits along the fault system and find that several segments, e.g. the Dangjiang fault and the Manigange segment of the Ganzi fault, have accumulated a large seismic moment (equates to an Mw>7 earthquake) since the last major event.
•We explore lateral variation in slip behaviour along the YS-GZ-XSH fault system.•Slip rate on the YS-GZ fault is 5-6 mm/yr, only half of that on the XSH fault.•Rate variation results from nonuniform deformation within the Bayan Har block.•The western YS-GZ-XSH fault segment is more mature than its eastern segment.•Some segments have accumulated a large seismic moment that equates to Mw>7.
The establishment of continental-scale drainage systems on Earth is largely controlled by topography related to plate boundary deformation and buoyant mantle. Drainage patterns of the great rivers in ...Asia are thought to be highly dynamic during the Cenozoic collision of India and Eurasia, but the drainage pattern and landscape evolution prior to the development of high topography in eastern Tibet remain largely unknown. Here we report the results of petro-stratigraphy, heavy-mineral analysis, and detrital zircon U-Pb dating from late Cretaceous-early Palaeogene sedimentary basin strata along the present-day eastern margin of the Tibetan Plateau. Similarities in the provenance signatures among basins indicate that a continental-scale fluvial system once drained southward into the Neo-Tethyan Ocean. These results challenge existing models of drainage networks that flowed toward the East Asian marginal seas and require revisions to inference of palaeo-topography during the Late Cretaceous. The presence of a continent-scale river may have provided a stable long-term base level which, in turn, facilitated the development of an extensive low-relief landscape that is preserved atop interfluves above the deeply incised canyons of eastern Tibet.
Whereas most continental faults are interseismically locked, some exceptions have been observed to exhibit aseismic slip over a range of depths in the Earth's upper crust, i.e. shallow creep. This ...unusual slip behaviour helps probe frictional properties of natural faults. Here, we investigate the kinematic features of a newly discovered shallow creeping fault, the Gozha Co fault in northwestern Tibet, using Sentinel-1 radar interferometry. High-resolution velocities derived from 4 tracks of Sentinel-1 data reveal a 120-km-long creeping section on the Gozha Co fault, with a mean surface fault-parallel rate of ∼3 mm/yr. We use a simple elastic dislocation model to invert for the rate and depth extent of creep. Results show that creep occurs at all depths in the crust at the tectonic loading rate, ∼5 mm/yr, indicating that the discovered shallow creep is steady-state in response to continued tectonic loading, which is supported by the analysis of surface creep time-series that yields a time-independent creep rate. The Sentinel-1 velocities also show that the Longmu Co fault, part of the commonly called Longmu-Gozha Co fault system, has no measurable motion, and therefore may be inactive. Present-day deformation within the Tianshuihai Terrane, 3.8±0.8 mm/yr E-W shear and 0.6±0.6 mm/yr N-S shortening as the GPS velocities show, is in fact accommodated by motion on the Gozha Co fault.
•We discover a 120-km-long shallow creeping section along the Gozha Co fault (GCF).•Creep on the GCF occurs at all seismogenic depths at the tectonic loading rate.•The newly discovered shallow creep on the GCF is a steady-state behaviour.•The GCF absorbs most of the present-day deformation within the Tianshuihai Terrane.
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