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The Qinling Shan is located between the North China Craton and the South China Block. Not only is investigating the exhumation process of the Qinling Shan beneficial for comprehending the tectonic collision history of mainland China but also for enhancing our understanding of the development of the Yellow and Yangtze Rivers. Previous studies have predominantly focused on bedrock analysis in the Qinling Shan. However, modern fluvial detrital samples offer a more extensive range of thermal history information. Therefore, we gathered modern fluvial debris samples from the Hanjiang River, which is the largest river in the South Qinling Shan. Subsequently, we conducted apatite fission-track analysis using the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method. A total of 214 valid track ages were obtained, with an age distribution ranging from 9.5 to 334.0 Ma. The Density Plotter software was employed to decompose the data and generate four prominent age peaks: 185, 103, 69, 35, and 12 Ma. The exhumation events of the Early Jurassic (185 Ma) and Cretaceous (103–69 Ma) in the Southern Qinling Shan were strongly influenced by the collision between the South China Block and the North China Craton, as well as the subduction of the West Pacific Plate, respectively. The far-field effect of the collision between the Indian Plate and the southern Asian continent influenced the exhumation of the South Qinling Shan during the Late Eocene (35 Ma) and Middle Miocene (12 Ma), respectively. In conjunction with the reported findings, we comprehensively analyzed the geological implications of the Mesozoic and Cenozoic exhumations of the Qinling Shan. The Qinling Shan emerged as a watershed between the Ordos and Sichuan Basins in the early Mesozoic and Cenozoic, respectively. However, the exhumation and expansion of the Tibetan Plateau has forced the Yangtze River to flow eastward, resulting in its encounter with the South Qinling Shan in the late Cenozoic. The exhumation of the Qinling Shan has resulted in fault depression in the southern Ordos Basin. This geological process has also contributed to the widespread arid climatic conditions in the basin. During the Miocene, the Yellow River experienced limited connectivity due to a combination of structural and climatic factors. As a result, the Qinling Shan served as an obstacle, dividing the connected southern Yangtze River from the northern segment of the Yellow River during the late Cenozoic era. [ABSTRACT FROM AUTHOR]

The 2021 Mw 7.4 Maduo (Madoi) earthquake that struck the northern Tibetan Plateau resulted in widespread coseismic deformation features, such as surface ruptures and soil liquefaction. By utilizing the unmanned aerial vehicle (UAV) photogrammetry technology, we accurately recognize and map 39,286 liquefaction sites within a 1.5 km wide zone along the coseismic surface rupture. We then systematically analyze the coseismic liquefaction distribution characteristics and the possible influencing factors. The coseismic liquefaction density remains on a higher level within 250 m from the surface rupture and decreases in a power law with the increasing distance. The amplification of the seismic waves in the vicinity of the rupture zone enhances the liquefaction effects near it. More than 90% of coseismic liquefaction occurs in the peak ground acceleration (PGA) > 0.50 g, and the liquefaction density is significantly higher in the region with seismic intensity > VIII. Combined with the sedimentary distribution along-strike of the surface rupture, the mapped liquefaction sites indicate that the differences in the sedimentary environments could cause more intense liquefaction on the western side of the epicenter, where loose Quaternary deposits are widely spread. The stronger coseismic liquefaction sites correspond to the Eling Lake section, the Yellow River floodplain, and the Heihe River floodplain, where the soil is mostly saturated with loose fine-grained sand and the groundwater level is high. Our results show that the massive liquefaction caused by the strong ground shaking during the Maduo (Madoi) earthquake was distributed as the specific local sedimentary environment and the groundwater level changed. [ABSTRACT FROM AUTHOR]

The topography evolution of the southeastern Tibetan Plateau provides a constraint for evaluating various geodynamic models of plateau formation. We reconstruct the Paleocene to Eocene paleoelevation of the Cenozoic Gonjo basin in the Qiangtang terrane, using oxygen and carbon stable isotopic results from pedogenic carbonates of the lower Ranmugou Formation. Lithofacies associations indicate that the lower Ranmugou Formation was deposited in alluvial fan and fluvial floodplain environments. U-Pb dating of volcanics within the middle Ranmugou Formation constrains the deposition of the lower Ranmugou Formation as prior to 43.2 Ma. Paleoelevations are calculated using both a thermodynamic model and an empirical relationship. The empirical relationship of elevation-δ 18 O is determined from a series of modern water samples. Calculated paleoelevations indicate that the Gonjo basin attained a minimum average elevation of 2100–2500 m in the early Eocene. Together with recent paleoaltimetry studies in the region, it can be concluded that the crust of southeastern Tibetan Plateau was already thickened by that time. The calculation is based on the section in northern Gonjo basin, where δ 18 O values of paleosol nodules appear to be unaltered, but we cannot rule out the possibility that δ 18 O values of the pedogenic carbonates had been partially reset. Our preliminary results favor tectonic models compatible with pre-Miocene uplift of the SE-central Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of the topography of eastern Tibet reflects the dynamic interaction between processes at Earth's surface and the lower crust. Reconstruction of its spatio-temporal development provides constraints for our understanding of the geodynamics of continental deformation. This study examines the topographic evolution of the southeast margin of the Tibetan Plateau throughout the Cenozoic using stable isotope paleoaltimetry of pedogenic carbonates preserved in Cenozoic basins extending from the northern to the southern portions of the SE margin of the Tibetan Plateau (Yunnan Province, China). Paleoelevations are calculated using a Monte Carlo simulation of the normally distributed uncertainties in each parameter used to calculate elevations from the isotopic value of pedogenic carbonate. Isotope–elevation relationships are determined from a modern sampling transect along the modern Lancang (Mekong) River and an estimated Eocene Rayleigh fractionation model that was randomly resampled. Calculated elevations indicate the SE margin of Tibet was at its present elevation as early as the late Eocene, with elevations of 3.3 km as far south as the northern third of China's Yunnan Province. This result expands the extent of the Eocene Tibetan Plateau more than 1000 km east of that previously known and precludes surface uplift via lower crustal flow in the area of SW Sichuan and Northern Yunnan as a driver for drainage reorganization and an observed middle to late Miocene pulse of rapid exhumation. Elevation estimates from the southern two thirds of the study area parallel to the Red River Fault suggest approximately 1 km of post late Miocene surface uplift, consistent with estimates from previous studies. [Copyright &y& Elsevier]

Geometric complexities of a fault system have a significant impact on the rupture behavior of the fault. The 2021 Mw7.4 Maduo earthquake occurred on a multi-segmented complex sinistral fault in the interior of the Bayan-Har block in the northern Tibetan Plateau. Here, we integrate centimeter-resolution surface rupture zones and Sentinel-2 optical displacement fields to accurately determine the geometric parameters of the causative fault in detail. An adaptive quadtree down-sampling method for interferograms was employed to enhance the reliability of the coseismic slip model inversion for interferograms. The optimal coseismic slip model indicated a complex non-planar structure with varying strike and dip angles. The largest slip of ~6 m, at a depth of ~7 km, occurred near a 6 km-wide stepover (a geometric complexity area) to the east of the epicenter, which occurred at the transition zone from sub-shear to super-shear rupture suggested by seismological studies. Optical and SAR displacement fields consistently indicated the local minimization of effective normal stress on releasing stepovers, which facilitated rupture through them. Moreover, connecting intermediate structures contributes to maintaining the rupture propagation through wide stepovers and may even facilitate the transition from subshear to supershear. Our study provides more evidence of the reactivation of a branched fault at the western end during the mainshock, which was previously under-appreciated. Furthermore, we found that a strong asymmetry in slip depth, stress drop, and rupture velocity east and west of the epicenter was coupled with variations in geometric and structural characteristics of fault segments along the strike. Our findings highlight the sensitivity of rupture behaviors to small-scale details of fault geometry. [ABSTRACT FROM AUTHOR]

The evolution of the Mekong River valley offers a unique record of the rock uplift and climate history of southeastern Tibet. Faster erosion rates along the valley than those on the flanks caused valley incision and local incision rates may reflect a mix of driving mechanisms, migrating knickpoints linked to a change in base level, and large-scale surface uplift. The thermochronometric-constrained erosion rates in the 2–3 km deep river channel compared to rates outside of the channels provide unique constraints on the driving mechanisms of the river incision. In particular, the onset of river incision at various points along the Mekong River helps identify whether exhumation signals are the result of knickpoint migration that would generate a younger incision upstream, or the outgrowth of the plateau, which would produce younger incision downstream. We analyze new and published apatite (U Th)/He ages collected along two elevation transects in the upper Mekong River: downstream at Tu'Er and upstream at Deqin. The data and thermokinematic modeling predict that the exhumation rates of the valley near Tu'Er and Deqin increased more rapidly than those of adjacent high-elevation, low-relief surfaces at ~11 Ma and ~ 4 Ma, respectively. Since then, exhumation variations have caused an increase of >2 km in the depth of the valley, indicating that the major incision of the Mekong River valley began at ~11 Ma near Tu'Er and approximately 4 Ma near Deqin. The results indicate that a major phase of the Mekong River valley incision may have developed and progressed upstream since the Miocene. • Thermochronometric study of the fluvial incision history of the Mekong River • Presents new and existing apatite (U Th)/He ages from two elevation transects • Incision onset at 11 Ma downstream near Tu'Er town and 4 Ma upstream near DeQin town • 2 km deep valley formed by progressive upstream erosion since the Miocene • Exhumation-development patterns of Tibetan Plateau low-relief surfaces are nonuniform. [ABSTRACT FROM AUTHOR]

River incision into a widespread, upland low-relief landscape, and related patterns of exhumation recorded by low-temperature thermochronology, together underpin geodynamic interpretations for crustal thickening and uplift of the eastern Tibetan Plateau. We report results from a suite of 11 (U–Th–Sm)/He cooling-age samples. Eight samples comprise a 1.2 km relief section collected from elevations up to 4800 m in the Jiulong Shan, an elevated, rugged region located in the hinterland of the Yalong-Longmen Shan Thrust Belt, and surrounded on three sides by upland low-relief landscape surfaces. Zircon and apatite cooling ages record two episodes of rapid exhumation in the early Oligocene and late Miocene, that were separated by a period of stability from ∼30 to 15 Ma. The first episode is consistent with a similar pulse evident from the Longmen Shan. The second episode is ongoing, and when integrated with adjacent cooling-age data sets, shows that doming of the Jiulong Shan has resulted in 2 to 4 km of differential exhumation of the plateau interior. We show from a compilation of glacial landform-mapping that the elevation of the plateau surface closely tracks global last glacial maximum equilibrium line altitude. We hypothesize that smoothing of highlands by efficient glacial and periglacial erosion, coupled with potential river captures and conveyance of sediments via external drainage, can yield an apparently continuous low-relief plateau landscape formed diachronously at high elevation. [ABSTRACT FROM AUTHOR]

Sedimentary provenance studies, which aim to identify the original source of sedimentary material, can offer valuable insights into transportation processes that occur within a given basin. Zircon and K-feldspar are complimentary and commonly used minerals in provenance tracing studies, given their representation of both stable and labile mineral components of different density. However, integration of detrital zircon and K-feldspar data has not been extensively explored for determining the source areas of the Yellow River Basin, which is one of the largest drainage basins in the world. In this study, published detrital zircon U Pb ages (n = 4773) and K-feldspar Pb isotopic compositions (n = 902) in the Yellow River Basin have been compiled and analyzed. Multidimensional scaling and inverse Monte Carlo modeling, allow holistic source-to-sink relationships for sediments in different sections of the Yellow River Basin to be established. Results show that: (1) There is no significant provenance relationship between the sediments from the upper Yellow River and those from the middle and lower reaches. (2) Sediments in the source area of the Yellow River primarily come from northeastern regions of the Tibetan Plateau. Additionally, the Western Loess Plateau and deserts contribute to the material composition of the upper Yellow River. The Yinchuan and Hetao plains are the main areas in the upper reaches of the Yellow River where substantial sediment deposition occurs. These sediments are from the recycling of older sediments transported from the upper reaches of the Yellow River to the Yinchuan and Hetao plains in the early Quaternary. (3) The detrital material in the middle reaches of the Yellow River directly from the Western North China Craton, which also supplied the Eastern Loess Plateau. Sanmen Gorge, located in the middle reaches of the Yellow River, serves as a depocentre for the detrital material from the Jinshan Gorge of the Yellow River and the Wei River, which is a major tributary of the Yellow River. (4) Sediment in the lower reaches of the Yellow River is mostly derived from the middle reaches of the river, with minor contributions from the Qinling Shan. The composition of detrital material in the Yellow River Basin exhibits spatial variations influenced by aeolian and fluvial transport processes resulting from tectonic and climatic activities in the upper and middle Yellow River. Human activities, such as the construction of reservoirs and the flushing of water and sediment along the Sanmen Gorge, have a notable impact on the material composition of the downstream section of the middle and lower Yellow River. The construction of reservoirs alters the natural flow of the Yellow River, leading to changes in sediment transport and deposition downstream. This can result in a decrease in sediment load, which affects the material composition of the riverbed and banks. Additionally, the flushing of water and sediment through the Sanmen Gorge can further modify the sediment distribution in the downstream section of the Yellow River. The U Pb ages of detrital zircon grains in the upper, middle, and lower reaches of the Yellow River exhibit broad agreement with the Pb isotope tracing results obtained from detrital K-feldspar grains, with proportional differences interpreted as relating to zircon recycling. This study provides an example of integrating multiple proxies to reconstruct the source of sediment in a large river system. The findings of this study can be used in the implementation of effective measures aimed at reducing the erosion of soil and protecting the ecology of the Yellow River Basin. [ABSTRACT FROM AUTHOR]

Graphic abstract Highlights • The uplift history of the northeastern margin of the Tibetan Plateau is investigated based on river sands detrital apatite fission track data. • Before the Indian-Asian collision, the North Qilian Shan had already uplifted. • The mountain-river-basin patterns were established in the early Miocene. Abstract Thermochronometry of modern river sands exploits the natural sampling of detritus in a river catchment to infer plausible regional exhumation patterns, when combined with available bedrock thermochronometric information. Apatite fission track age distributions for six detrital samples are reported in this study to resolve the exhumation history of the upper reaches of the Heihe River, draining North Qilian Shan and Tuole Shan, the northeastern margin of the Tibetan Plateau. The apatite fission track (AFT) ages include four major populations: late Paleozoic (300 ± 55–293 ± 43 Ma), early Mesozoic (223 ± 15–205 ± 17 Ma), late Jurassic-Cretaceous (112 ± 6.2–84.8 ± 5.6 Ma), and Cenozoic (63.8 ± 5.9–19.3 ± 1.7 Ma). The ages of these populations correspond well with the deformation and cooling history of the study area. The late Paleozoic and early Mesozoic AFT age populations record cooling events resulting from continental collision between the Qiantang and Kunlun blocks. The late Jurassic-Cretaceous AFT age populations are interpreted to record cooling events associated with exhumation of North Qilian Shan and Tuole Shan due to the collision of the Lhasa block with Asian continent. The Cenozoic AFT age populations record several cooling events. A cooling event is recorded corresponding to exhumation of North Qilian Shan and Tuole Shan due to late stress from the Lhasa-Asia collision, causing deformation nearly synchronous with the India-Asia collision. Another cooling event is recorded corresponding to uplift and exhumation in Oligocene time due to ongoing India-Asia convergence. North Qilian Shan and Tuole Shan were constructed as a distal effect of India-Asia convergence in the early Miocene while approaching their present mountain-river-basin distributions. Thermochronometry applied to Heihe River sediments provide convinced evidence of multi-stage exhumation of most northeastern margin of the Tibetan Plateau in the late Paleozoic-Cenozoic. [ABSTRACT FROM AUTHOR]

Following the 2008 Wenchuan earthquake (Sichuan, China), the dextral strike-slip Longriba fault system (LFS) has been recognized as a main intracontinental structural boundary within the eastern Tibetan Plateau. While numerous studies have focused on the Longmen Shan frontal range to constrain the dynamics of the eastern Tibetan margin, little is known on the LFS, particularly on its eventual influence on the geomorphological evolution of the latter. Here, we provide a new data set of denudation rates derived from beryllium-10 concentrations in river sediments from 33 medium-sized catchments. Our sampling area covers the frontier between the dissected margin and the low relief interior plateau. Our results reveal a sharp increase of denudation across the LFS, from < 0.1 mm/y in the Ruoergai basin to 0.3 mm/y toward the Longmen Shan range. Such denudation pattern indicates a major morphotectonic control of the fault system on the eastern Tibetan margin evolution. Additional topographic analysis confirms the role of the LFS as an important geomorphological boundary, restraining the westward propagation of river incision into the low-relief areas, thus partly preventing the dismantling of the eastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Abstract: The timing of uplift of the Tibetan Plateau remains controversial, with estimates varying from Eocene to more recent than Pliocene. In particular, the paleoaltimetry of the Qiangtang terrane, on the central Tibetan Plateau, is completely unknown. Here, we present new stable isotope results of fluvial/lacustrine carbonate cement, pedogenic carbonate and marl from the Kangtuo and Suonahu formations deposited between ∼51 and ∼28Ma in the Heihuling–Bamaoqiongzong area of the northern Qiangtang terrane. The lithofacies associations indicate that the Kangtuo formation was deposited in alluvial fan and fluvial floodplain environments, and the Suonahu formation was deposited in near shore lacustrine, playa-lake and channelized fluvial environments. Carbon and oxygen isotope values, coupled with the sedimentary facies interpretations, point to evaporation and low respiration rates in the Eocene–Oligocene paleosols, suggesting an arid climate in the high Qiangtang area at the time. The δ 18Opsw values of paleo-surface water reconstructed from the lowest (i.e. the least evaporated) δ 18Oc (PDB) values of the unaltered authigenic carbonates are used to make the minimum estimates of the average paleoelevation of the drainage basin. The paleoelevation of the northern Qiangtang terrane is reconstructed as above 5000m by at least the middle Oligocene (28Ma), similar to the present elevation in this area. The aridity and the positive shift in oxygen isotope values of surface waters in our study area may suggest that the high Lhasa terrane established by the middle Oligocene blocked the northward transport of tropical moisture. Maintenance of high elevation (>5000m) from at least the Oligocene to the present suggests that the Qiangtang crust was already thickened by that time, and that underthrusting of India beneath Asia since then has continued to provide additional material while at the same time driving Asian lower crust eastward by crustal flow. [Copyright &y& Elsevier]