Himalayan-Tibetan Plateau Research Articles

Hydrochemical and isotopic characteristics on the southern and northern slopes of the Himalayas: spatio-temporal controls and source apportionment

Water-soluble ions, inorganic nitrogen, and stable isotopes in precipitation were assessed from the southern (Koshi Tappu and Khandbari) and northern slopes (Lhasa and SET) of the Himalayas to understand the sources, chemistry of regional precipitation, and climatic processes. Water soluble ions showed distinct seasonal variation, with higher concentrations in the non-monsoon. The concentration of ionic species was highest in Koshi Tappu, followed by Lhasa, SET, and Khandbari. The sources were from the terrigenous (Ca2+, HCO3−), marine (Na+ and Cl−), anthropogenic (SO42−, NO3−, and NH4+), terrigenous and marine (Mg2+), and biomass-burning (K+). The southern slope, relative to the northern, was more prone to anthropogenic emissions with higher deposition. Among all sites, inorganic nitrogen deposition at Koshi Tappu was higher than the threshold value (10 kg ha−1 y−1). The isotopic composition during the study period was higher in non-monsoon, started declining from June, and depleted in July and August compared to other months, i.e., the monsoon mature phase, along the south-to-north transect. The diminished value of stable isotopes in precipitation with increasing altitude underlines the evidence of the orographic effect in isotopic composition. Our study delineated that the higher/lower d-excess value increased with altitude on the southern/northern slope of the Himalayas. The backward trajectory analysis and the National Centers for Environmental Prediction's Final (NCEP FNL) datasets identified that most of the trajectories arrived from warm and humid low-latitude regions during monsoon and westerlies in non-monsoon. Thus, the chemical characteristics and stable isotopic composition of precipitation differed on the southern and northern slopes of the Himalayas by orographic effect and various sources. This study provides new insights into the atmospheric environment and climatic control of stable isotopes in the Himalayan Tibetan Plateau and facilitates monitoring of transboundary air pollution.

Eocene tearing and fragmentation of Indian lithosphere beneath the Woka rift, southern Tibet

When and how the syncontractional N-S−trending rifts formed in the Himalayan-Tibetan Plateau are crucial, yet unsolved issues that could help establish the interplay between geodynamic evolution and uplift of the plateau. Recent geophysical observations indicate that although Indian lithosphere tearing is the most likely trigger for rift formation, the timing of this tearing remains uncertain. To address this issue, we studied the Woka rift, which represents a typical N-S−trending rift in southern Tibet. Our results show that granitoids from the hanging wall and footwall of the Woka rift have significantly different magma crystallization temperatures (770−860 °C versus 650−750 °C) and crustal thickness (∼40 km versus ∼60 km) during the Eocene. These differences were most likely linked to tearing of the Indian lithosphere. The integration of crustal thickness trends and bedrock emplacement depth from the Eocene to the Oligocene suggest that the hanging wall exhumed at a faster rate than the footwall. From this information, it is clear that the Woka rift did not undergo E-W extension during this period. Integrating data from geophysics, thermochronology, mantle-derived, N-S−trending dikes, and adakitic rocks, we propose that Indian lithospheric tearing and fragmentation during the Eocene caused weakening of the Tibetan middle-lower crust rather than directly triggering surface extension of the Woka rift. This study has significant implications for the deep lithospheric processes and surface responses in the Himalayan-Tibetan Plateau.

Geothermal input significantly influences riverine and oceanic boron budgets

The evolution of boron isotope compositions of seawater (δ11Bsw) over the Cenozoic has important implications for reconstructions of atmospheric CO2 and is tightly linked to boron input from the Himalaya-Tibetan Plateau. However, controls on evolution inδ11Bsw remain elusive. We report geochemical measurements of the Yarlung Tsangpo River draining the Tibetan Plateau and observe exceptionally high riverine boron concentrations and extremely low δ11B values. Calculation indicates that >50% of riverine boron is sourced from geothermal waters. Combined with global datasets, we show that global riverine boron input to the ocean is largely influenced by geothermal input. Mass-balance calculations indicate that an averaged 1.5-fold decrease in global geothermal inputs is sufficient to introduce 3‰ increase in Cenozoic δ11Bsw. Therefore, geothermal waters significantly affect global riverine and thus oceanic boron budgets. The increased δ11Bsw since the Cenozoic may be resulted partly from declining global geothermal activity.

Southward displacement of the glacial westerly jet over Asia driven by enhanced Arctic amplification after the Mid-Brunhes Event

The climate and paleoenvironmental evolution of the East Asian continent and adjacent Northwest Pacific Ocean is governed by the interplay of the region's dominant features in oceanic and atmospheric circulation, which control the redistribution of heat and moisture. In the atmospheric realm, the subtropical westerly jet stream and East Asian monsoon are crucial components of climate evolution over East Asia, an area that is inhabited by almost half of the world's population. Reconstruction of long-term changes in atmospheric circulation in this region is to date scarce, especially on timescales predating the last glacial-interglacial cycle. Here, we reconstruct dust fluxes, marine productivity and water temperatures in the Northwest Pacific Ocean using lipid biomarkers both from terrestrial and marine organisms and elemental scanning data. Land-plant derived wax lipids in the studied sediments were used as indicators for dust fluxes and hence are representative of past changes in wind strength and pathways. We evaluate changes both in the zonal westerlies and monsoonal winds over the past 1 Ma and across major climatic events. Prior to the Mid-Brunhes Event (MBE; ~ 430 ka ago), concentrations of these compounds showed a distinct glacial-interglacial pattern, which we relate to past changes in the position of the westerly jet stream. We demonstrate substantial changes in wind patterns across the MBE, resulting in reduced dust fluxes to the Northwest Pacific in ensuing glacials. We propose that the westerly jet was permanently located south of the Himalaya-Tibetan Plateau through peak glacials, fostered by amplified Arctic cooling.

Insights into the evolutionary history of Diestramimini cave crickets (Orthoptera, Rhaphidophoridae)

AbstractDiestramimini is one of the two tribes of Aemodogryllinae and is mainly distributed in southern China and Southeast Asia. The intergeneric phylogenetic relationship and historical biogeography of this tribe remain unclear. Here, we present the first phylogenetic and biogeographical analyses of Diestramimini based on three mitochondrial (COI, 12S rRNA and 16S rRNA) and two nuclear (18S rRNA and 28S rRNA) gene fragments. The molecular phylogenetic inference strongly supports the monophyly of Diestramimini and recovers the sister‐group relationship between Diestramima + Tamdaotettix and Arboramima + Gigantettix. A new genus, Bidiestramima Zhu & Shi gen. n., is established and recovered as sister to all the remaining genera of Diestramimini. Moreover, a new species Bidiestramima hekouensis Zhu & Shi gen. et sp. n. is described. Mimadiestra is recovered as paraphyletic, and thus, we propose two new combinations based on the combination of morphological and molecular evidence: Bidiestramima dicha comb. n. and Tamdaotettix (Laotettix) gracilus comb. n. Divergence time estimation and reconstruction of ancestral areas indicate that Diestramimini in China may have originated from Southern Yunnan and Guangxi during the mid‐Oligocene and had two separate evolutionary routes. The diversification of Diestramimini has been driven by several dispersal and vicariance events since the Miocene, linked to the uplift of the Himalaya–Tibetan Plateau, the formation of the monsoon and climate fluctuations.

Tectonic and orbital forcing of the South Asian monsoon in central Tibet during the late Oligocene

The modern pattern of the Asian monsoon is thought to have formed around the Oligocene/Miocene transition and is generally attributed to Himalaya-Tibetan Plateau (H-TP) uplift. However, the timing of the ancient Asian monsoon over the TP and its response to astronomical forcing and TP uplift remains poorly known because of the paucity of well-dated high-resolution geological records from the TP interior. Here, we present a precession-scale cyclostratigraphic sedimentary section of 27.32 to 23.24 million years ago (Ma) during the late Oligocene epoch from the Nima Basin to show that the South Asian monsoon (SAM) had already advanced to the central TP (32°N) at least by 27.3 Ma, which is indicated by cyclic arid-humid fluctuations based on environmental magnetism proxies. A shift of lithology and astronomically orbital periods and amplified amplitude of proxy measurements as well as a hydroclimate transition around 25.8 Ma suggest that the SAM intensified at ~25.8 Ma and that the TP reached a paleoelevation threshold for enhancing the coupling between the uplifted plateau and the SAM. Orbital short eccentricity-paced precipitation variability is argued to be mainly driven by orbital eccentricity-modulated low-latitude summer insolation rather than glacial-interglacial Antarctic ice sheet fluctuations. The monsoon data from the TP interior provide key evidence to link the greatly enhanced tropical SAM at 25.8 Ma with TP uplift rather than global climate change and suggest that SAM's northward expansion to the boreal subtropics was dominated by a combination of tectonic and astronomical forcing at multiple timescales in the late Oligocene epoch.

Diversity and conservation of higher plants in Northwest Yunnan-Southeast Tibet

Located on the southern margin of the Qinghai-Tibet Plateau, the Northwest Yunnan-Southeast Tibet (NYST) is a biodiversity hotspot. However, plant diversity in the region faces enormous threats, including forest fragmentation and overexploitation of natural resources. Here, we updated the catalogue of higher plants in NYST by integrating various data sources and referring to the newest results of molecular systematics and taxonomy. Combining phylogenetic approaches and a spatial analysis of forest landscape fragmentation, we assessed spatial variations in taxonomic richness and phylogenetic diversity, and identified potential geographic units for conservation gaps. NYST harbours nearly one-third of China's higher plant species, of which ~60% of the species listed as threatened are endemic. Among the genera, the highest number of endemic and threatened species belong to Rhododendron. The largest increase in the number of threatened species was observed in the Orchidaceae over the last 15 years. Seed plant taxonomic richness and phylogenetic diversity were significantly positively correlated at both the species and genus levels. Counties with large mountains are hotspots of phylogenetic diversity as well as total, endemic, and threatened species richness. The pattern of diversity of higher plants in the study area is likely related to the Himalayan-Tibetan Plateau uplift. The western part of Yulong County and the central to southern parts of Shangri-La County are conservation gaps in this area. In-depth local field surveys of plant diversity are needed, especially in those counties where there is large disparity between the number of species present and collected specimens (e.g., Yulong County). This study provides data and a theoretical basis for the study and conservation of NYST plant diversity.

Landform evolution in Asia during the Cenozoic revealed by formation of drainages of Wei River and Indus River

Formation and evolution of the Asian landform was determined by growth of the Himalaya-Tibetan Plateau and evolution of the Asian monsoon climate during the Cenozoic period. In this process, mountain building and degradation, and river drainage reorganization are the most obvious results. On the other hand, developments of large scale drainages preserved in related basin sediments are direct records of evolution of Asian landforms. In this study, we use thick fluvial-lacustrine sediments in the Weihe Basin near the northeastern Tibetan Plateau, and Ocean Drilling Program (ODP) sediment cores from Arabian Sea adjacent to the southwest Himalaya-Tibetan Plateau, to reconstruct erosion processes of the Himalaya-Karakorum and Qinling Mountains and infilling history of the Weihe Basin and northern Arabian Sea during the Cenozoic. Based on independent stratigraphic chronology and source-to-sink analyses, our results show that the large drainages of the Wei River and the Indus River were established at an upper limit of time by middle Eocene. Since the formation of these large drainages is mainly determined by topography and precipitation/runoff, we deduce that key parts of Asian landform such as southwestern/western Tibetan Plateau and Qinling Mountains had grown to a significant elevation to form the proto-Indus and proto-Wei rivers catchment. The modern-analogue Asian topography was established at least by the middle Eocene. Our new results support an early origin of the Asian landforms as responses to the collision of Indian and Eurasian plates and erosion by the Asian hydrology processes.

Relationship between radiogenic heat production in granitic rocks and emplacement age

Granites play a crucial role in the Earth's thermal regime and its evolution. Radiogenic heat production (RHP) by the decay of radioactive elements (U, Th, K) in granites is a significant parameter in estimating the thermal structure of the lithosphere. RHP variability of granites with their emplacement ages could provide insights for thermal modeling in different geological epochs. An aggregated RHP from 2877 globally-distributed granitic samples of continental crust are analyzed for this study; these sample cover the entire geological history. The average bulk RHP in all types of granitic rocks of all ages is 2.92 ± 1.86 μW/m3. The RHP tends to increase gradually with progressively younger geologic emplacement age, based on a statistical analysis of the data. However, the youngest granites do not necessarily have the highest RHP. The mean RHP in 181 representative Cenozoic Himalayan leucogranites— which are the youngest granites found on Earth, is as low as 1.84 μW/m3. This is probably related to the initial conditions of magma formation, magmatic source material, and differentiation processes in the Himalayan–Tibetan plateau. By correcting the decay factor, variations of the RHP in the emplaced granitic rocks are obtained, indicating the changing levels of heat production and different thermal regimes on Earth in various geological epochs. The highest RHP in granitic rocks emplaced in the Archean and Early Proterozoic corresponds to two global-scale collisional events during supercontinent cycles, at 2.7 and 1.9 Ga respectively. RHPs of granites can be an important indicator in the study of Earth's thermal regime and its evolution.

Enhanced weathering input from South Asia to the Indian Ocean since the late Eocene

Enhanced silicate weathering induced by the uplift of the Himalayan-Tibetan Plateau (HTP) has been considered as the major cause of pCO2 decline and Cenozoic cooling. However, this hypothesis remains to be validated, largely due to the lack of a reliable reconstruction of the HTP weathering flux. Here, we present a 37-million-year record of the difference in the seawater radiogenic neodymium isotopic composition (ΔεNd) of Ocean Drilling Program (ODP) sites and Fe-Mn crusts between the northern and central Indian Ocean, which indicates the contribution of regional weathering input from the South Asian continent to the Indian Ocean. The results show a long-term increase in ΔεNd and thus provide the first critical evidence of enhanced South Asian weathering input since the late Eocene. The evolution coincided well with major pulses of surface uplift in the HTP and global climatic transitions. Our foraminiferal εNd record suggests that tectonic uplift and silicate weathering in South Asia, especially in the Himalayas, might have played a significant role in the late Cenozoic cooling.

Tracing the origin of elevated springtime atmospheric sulfate on the southern Himalayan-Tibetan plateau

The Himalayan Tibetan Plateau (HTP) is one of the world's most climate-sensitive regions outside the polar regions.

Mitochondrial cytochrome b indicates the presence of two paraphyletic diverged lineages of the blue sheep Pseudois nayaur across the Indian Himalaya: conservation implications.

Populations exhibit signatures of local adaptive traits due to spatial and environmental heterogeneity resulting in microevolution. The blue sheep is widely distributed across the high Asian mountains and are the snow leopard's principal prey species. These mountains differ in their evolutionary history due to differential glaciation and deglaciation periods, orography, and rainfall patterns, and such factors causes diversification in species. Therefore, we assess the phylogeographic status of blue sheep using the mitochondrial cytochrome b gene (220bp) across the Indian Himalayan region (IHR) and its relationship with other populations. Of the observed five haplotypes, two and three were from the western Himalayas (WH) and eastern Himalayas (EH) respectively. One of the haplotypes from WH was shared with the population of Pamir plateau, suggesting historical maternal connectivity between these areas. The phylogenetic analyses split the blue sheep into two paraphyletic clades, and western and eastern populations of IHR were within the Pamir and Tibetan plateau clades, respectively. We observed a relatively higher mean sequence divergence in the EH population than in the WH. We propose five 'Evolutionary Significant Units' across the blue sheep distribution range based on observed variation in the species' ecological requirements, orography, climatic conditions, and maternal lineages, viz.; Western Himalaya-Pamir plateau (WHPP); Eastern Himalaya-Tibetan plateau (EHTP); Qilian mountains; Helan mountains and Hengduan mountains population. Despite the small sample size, population divergence was observed across the IHR, therefore, we suggest a transboundary, collaborative study on comparative morphology, anatomy, ecology, behaviour, and population genetics using harmonized different genetic markers for identifying the overall taxonomic status of the blue sheep across its range for planning effective conservation strategies.

Two kinematic transformations of the Pamir salient since the Mid-Cenozoic: Constraints from multi-timescale deformation analysis

The Pamir salient is a key part of the Himalayan–Tibetan Plateau orogenic system and has undergone intense tectonic deformation during the India–Asian collision. Delineating the Cenozoic kinematics and geodynamics of the Pamir salient requires a comprehensive understanding of the active arcuate structures along its frontal margin, from the perspective of the multi-spatiotemporal evolution of deformation patterns. Here, we reviewed the deformation rates of the major structures at different timescales, reanalyzed the published Global Positioning System velocities, and examined the present-day seismicity to constrain the kinematics of the Pamir salient since the Late Cenozoic. Integrated with the crustal evolution history during the Middle–Late Cenozoic and the deep structure, we proposed a new model to explain the multi-stage kinematics and associated geodynamics of the Pamir salient. During ∼37–24 Ma, the initial Pamir salient moved northward via radial thrusting that rotated the basins on both sides, which was driven by the continuous compression of the Indian slab after the breakoff of its oceanic part. During ∼23–12 Ma, the gravitational collapse of the Central and South Pamir crusts, which was induced by the breakoff of the continental part of the Indian slab, triggered the extension within the Pamir and foreland-ward movement of the upper crust. The upper crustal materials moved in varying directions due to the differential strength of the foreland areas, transforming the crustal kinematics from radial thrusting into a combination of radial thrusting and transfer faulting. Since the coupling of the Indian and Pamir slabs at ∼12–11 Ma, the deformation propagation towards the forelands accelerated, after which the kinematics of the Pamir salient exhibited asymmetric radial thrusting that has been sustained until the present. The asymmetric radial thrusting was likely driven by the compressive stress effect of the lithospheric basal shear generated by the underthrusting of the cratonic Indian lithosphere, which further led to the rollback of the Pamir slab and the consequent migratory extension in the South Pamir.

The stepwise Indian-Eurasian collision and uplift of the Himalayan-Tibetan plateau drove the diversification of high-elevation Scytodes spiders.

The Cenozoic Indian-Eurasian collision and uplift of the Himalayan-Tibetan Plateau (HTP) are among the most important geological events in the world. They have affected the diversification of regional biota of many taxonomic groups on and around the HTP. However, the exact timing and model of the collision and uplift events and speciation on and around the HTP are still in debate. The Himalayas group of Scytodes spitting spiders (Araneae: Scytodidae) are distributed at high elevations of the HTP and northern Indochina. Here, we reconstruct a dated molecular phylogeny for pan-Himalayan Scytodes spiders, including the Himalayas group, with full geographical sampling of the species from the HTP and Indochina. We test a hypothesis to explain that the rich montane biodiversity of the region is uplift-driven diversification-that orogeny drives rapid in situ speciation of the resident Scytodes lineages. Our findings revealed that the separation of the Himalayas clade from the Myanmar clade took place during the middle Oligocene, reflecting the final collision of India with Eurasia. The deep divergences among three clades (the Himalayas, the Myanmar and the Indochina clades) occurred from the middle Eocene to the middle Oligocene, corresponding to two early uplift events of the HTP. The evolutionary split between the Himalayas + Myanmar and Indochina clades were simultaneous with the rapid lateral extrusion of Indochina by the initial Himalayan uplift around the Eocene. This study highlights the importance of the diversification of dispersal-limited, high-elevation invertebrates as independent lines of evidence to reflect key tectonic events in the Himalayan-Indochina region, supporting the stepwise model for the Indian-Eurasian collision and uplift of HTP.

Seasonal and Semi‐Diurnal Variations in Cloud‐Phase Characteristics Over the Southern Himalayas and Adjacent Regions as Observed by the Himawari‐8 Satellite

AbstractInvestigated in this study are the seasonal and semi‐diurnal variations of the cloud‐phase climatology over the southern Himalayas and adjacent regions by using 5 years of Himawari‐8 cloud‐product data (2016–2020). The four selected regions from south to north are the Gangetic Plains (I), Himalayan foothills (II), southern slope of the Himalayas (III), and the Himalayan–Tibetan Plateau region (IV), respectively. Results showed that the cloud frequency of cloud gradually increases from region I via II to III, then sharply decreases as the altitude increases up to IV. Ice‐phase clouds occurs more frequently over regions I/II (III/IV) during boreal summer (winter), while water‐phase cloud has a higher frequency over region III/IV (I/II) in summer (winter), respectively. All of the different cloud phases have a clear seasonal cycle. Furthermore, the semi‐diurnal variation shows that water‐phase clouds tends to have an occurrence frequency peak around noon (in the later afternoon) over regions I/II/III in summer (winter), whereas over region IV it only occurs more in the morning in both seasons. Ice‐phase cloud generally occurs more in the late afternoon in both boreal summer and winter, especially over region IV. Further analysis showed that the differences in the cloud‐phase characteristics over the southern Himalayas and adjacent regions are likely related to the interactions of the synoptic‐scale circulation, the topography, and the water vapor transport.

Modern-like elevation and climate in Tibet since the mid-Miocene (ca. 15 Ma)

Abstract When the modern-like geomorphology and climate pattern of the Himalaya-Tibetan Plateau were established still remains unclear. In this study, we apply paired stable isotope compositions of carbonate (δ18Oc) and leaf waxderived n-alkanes (δ2Halk) from the upper Gazhacun Formation in the Namling Basin to reconstruct the middle Miocene elevation and climate of southern Tibet. Depositional age of the upper Gazhacun Formation has been precisely constrained to between 15.5 Ma and 15.1 Ma by zircon U-Pb ages of dacite interlayers. Paired carbonate derived δ18Ow values (–17.9 ± 1.3‰ to –18.3 ± 1.3‰) and leaf-wax derived δ2Hw values (–131.5 ± 20‰ to –145.7 ± 20‰) plot on or very close to the global meteoric water line suggesting that these samples experienced little evaporation enrichment and isotopic alternation. Based on these two independent proxies, paleoelevation estimates for the Namling Basin are consistently between 4.6+0.7/-0.8 km and 5.2+0.7/-0.8 km, supporting a high elevation for southern Tibet in the mid-Miocene. Integrated with published paleoelevation estimates for the Himalaya, central and northern Tibet in literature, a near-present elevation across the whole Himalaya-Tibetan Plateau has already been established since the middle Miocene (ca. 15 Ma). Besides, stable isotopic values across the Himalaya-Tibetan Plateau show that the δ2Hw values gradually increase northward from the Himalaya to northeastern Tibet, quite similar to that of the present day. This pattern suggests that during the middle Miocene, the Himalaya-Gangdese system may have blocked southerly monsoonal moisture from reaching northern Tibet. Westerlies or local recycling of moisture might be the dominant moisture sources across northern Tibet, with enriched δ18Ow and δ2Hw precipitation values that could lead to erroneous paleoelevation estimates over central and northern Tibet.

Phylogeny and phylogeography of Diestramima cave crickets (Orthoptera: Rhaphidophoridae): speciation driven by multiple dispersal and vicariance events

AbstractCave crickets (Orthoptera: Rhaphidophoridae) are an understudied family with poor dispersal abilities and broad distributions, which makes them ideal for investigations of historical biogeography. Within Rhaphidophoridae, Diestramima is the largest genus of the tribe Diestramimini, and most species are endemic to China. It was divided into three subgenera based only on morphological characteristics, and no molecular evidence has been previously reported. Here, we reconstruct the phylogeny and phylogeography of Diestramima based on three mitochondrial (COI, 12S rRNA and 16S rRNA) and two nuclear fragments (18S rRNA and 28S rRNA). A total of 114 samples representing 28 morphological species were sampled from China. Molecular phylogenies were reconstructed using Bayesian inference and maximum likelihood and four approaches (ABGD, jMOTU, GMYC and bPTP) were employed to delimit species. Phylogenetic analyses highly supported the monophyly of Diestramima, but did not support the classification system consisting of three subgenera. Species delimitation methods suggested 28 species, among which six new species were described: Diestramima furcata Zhu & Shi sp. n., Diestramima spinata Zhu & Shi sp. n., Diestramima qionglaiensis Zhu & Shi sp. n., Diestramima taiwanensis Zhu & Shi sp. n., Diestramima longifolia Zhu & Shi sp. n., Diestramima sichuanensis Zhu & Shi sp. n. Divergence time estimation and reconstruction of ancestral areas indicated that Diestramima may have originated from Southern Yunnan at 17.72 Ma (95% highest probability density: 14.71–21.05 Ma) in the early Miocene. The initial divergence within the genus was likely to be correlated with geographical isolation. Most speciation events have occurred since the Pliocene, possibly driven by multiple dispersal and vicariance events and influenced by the uplift of the Himalaya–Tibetan plateau and climate change.ZooBank URL: http://zoobank.org/urn:lsid:zoobank.org:pub:D461A536‐6728‐4547‐9EC4‐AF56D3BB9000. http://zoobank.org/urn:lsid:zoobank.org:act:5FA4075B‐4CD2‐43A5‐B109‐D32882CCF369. http://zoobank.org/urn:lsid:zoobank.org:act:C3D02B4E‐1442‐456F‐BD59‐C811716F0704. http://zoobank.org/urn:lsid:zoobank.org:act:E022BD2C‐8A69‐4C00‐B008‐129DE9ABB229. http://zoobank.org/urn:lsid:zoobank.org:act:4E5552E4‐78CB‐498F‐ABB6‐98D56BEC6FBC. http://zoobank.org/urn:lsid:zoobank.org:act:480E002C‐4B82‐4F0D‐B421‐2AFD9F333333. http://zoobank.org/urn:lsid:zoobank.org:act:220EE409‐293B‐4ACC‐B853‐090EF226123D.

Geochemical comparisons of weathering, provenance and tectonics in the fluvial sediments from Yarlung Zangbo to Brahmaputra River

Globally, large river sediments record crucial signatures of geology and climate change from source to sink. The Yarlung Zangbo River (YZR) is upstream of the Brahmaputra River (BJR). It originates in the active Himalaya-Tibetan Plateau (HTP) and finally enters the Indian Ocean. Therefore, YZR-BJR sediments are best for studying Earth surface processes and climate variations in Asia. However, few comparisons of their sediment chemistry have been conducted with respect to the weathering, climate, provenance and tectonic setting. Here, we examined 80 fluvial sediments measuring major and trace elements with chemical indicators. The YZR-BJR sediments are derived from a felsic source on an active continental margin with a continental island arc. Both the Lhasa terrane (LT) and Himalayan orogen are possibly the main sources of upstream (YZR) sediments that are chemically close to the upper crustal continent (UCC). In contrast, downstream BJR sediments, such as the post-Archean Australian Shale (PAAS), are predominantly sourced from the eastern Himalayan orogen, followed by LT. Due to the uplift of HTP and global cooling, the YZR sediments underwent low to moderate silicate weathering, while the downstream BJR sediments experienced weaker weathering processes with lower chemical index of alteration (CIA) values. This means dominant physical weathering and erosion in the source area and thus provides substantial sediments. Although the CIA values of finer overbank sediments are slightly higher than those in coarser riverbank sediments, they can still reveal weathering combined with other chemical indicators. The results suggest that there is no obvious contrast between YZR and BJR in the HTP due to river mixing and strong physical weathering.

Linkage between the absorbing aerosol-induced snow darkening effects over the Himalayas-Tibetan Plateau and the pre-monsoon climate over northern India

Linkage between the absorbing aerosol-induced snow darkening effects over the Himalayas-Tibetan Plateau and the pre-monsoon climate over northern India

Formation Mechanisms and Source Apportionments of Airborne Nitrate Aerosols at a Himalayan-Tibetan Plateau Site: Insights from Nitrogen and Oxygen Isotopic Compositions.

Formation pathways and sources of atmosphere nitrate (NO3-) have attracted much attention as NO3- had detrimental effects on Earth's ecosystem and climate change. Here, we measured nitrogen (δ15N-NO3-) and oxygen (δ18O-NO3- and Δ17O-NO3-) isotope compositions in nitrate aerosols at the Qomolangma station (QOMS) over the Himalayan-Tibetan Plateau (HTP) to quantify the formation mechanisms and emission sources of nitrate at the background site. At QOMS, the enhanced NO3- concentrations were observed in the springtime. The average δ15N-NO3-, δ18O-NO3-, and Δ17O-NO3- values were 0.4 ± 4.9, 64.7 ± 11.5 and 27.6 ± 6.9‰, respectively. Seasonal variations of isotope ratios at QOMS can be explained by the different emissions and formation pathways to nitrate. The average fractions of NO2 + OH and N2O5 + H2O to nitrate production were estimated to be 43 and 52%, respectively, when the NO3 + hydrocarbon (HC)/dimethyl sulfide (DMS) (NO3 + HC/DMS) pathway was assumed to be 5%. Using stable isotope analysis in the R (SIAR) model, the relative contributions of biomass burning (BB), biogenic soil emission, traffic, and coal combustion to nitrate were estimated to be 28, 25, 24, and 23%, respectively, on yearly basis. By FLEXible PARTicle (FLEXPART) dispersion model, we highlighted that NOx from BB emission over South Asia that had undergone N2O5 + H2O processes enhanced the nitrate concentrations in the springtime over the HTP region.