Gobi Altai Mountains Research Articles

Quaternary provenance changes in the loess deposits of the western Chinese Loess Plateau: Insights from U-Pb age spectra of detrital zircon

The western region of the Chinese Loess Plateau (CLP) on the western side of the Liupan Mountains connects the Tibetan Plateau with the deserts of the northern arid zones. This region is key for understanding of the coupled relationship between tectonic uplift and surface processes (erosion and climate) on the Tibetan Plateau; however, the variation of Quaternary wind-dust sources in the region remains uncertain, confounding analysis. In this paper, we conduct a source tracing investigation using detrital zircon U-Pb dating of 12 loess layers from the Huining aeolian sedimentary sequence of the western CLP, reconstruct the history of provenance changes during the Quaternary Period, and further explore driving mechanisms. Results show that aeolian dust from the western CLP is mainly from the northeastern margin of the Tibetan Plateau (NTP). At 1.8–1.66 Ma, the main source region was the NTP, which corresponds to the Episode C uplift event of the Tibetan Plateau. The dominant source area transitioned to the Gobi Altay Mountains (GAMs) around 1.5–1.4 Ma. This shift suggests that the tectonic uplift of the Tibetan Plateau had entered a period of stasis following the conclusion of Episode C, leading to increased transport of detrital material from the GAMs by the East Asian Winter Monsoon. After 1.24 Ma, the dominant source region abruptly changed from the GAMs to the NTP and lasted until 0.04 Ma. The topographic fluctuations caused by the Kunhuang Movement appears to have been the main reason for the sudden source change. Based on our results and evidence from previous studies, the source changes that occurred during the Quaternary Period were in response to a combination of tectonic events and climate change. Comparison of zircon age spectra between the eastern and western CLP further support the idea that the Plateau Winter Monsoon was the main transport system for aeolian dust in the western CLP.

Palaeolakes, caves and settlement during the Pleistocene and Holocene around Tsakhiurtyn Hundi, Mongolia

AbstractThe authors present results from a new research project focusing on the prehistory of the area surrounding a vast flint outcrop in Mongolia, called Tsakhiurtyn Hundi, in the borderland between the Gobi-Altai Mountains and Gobi Desert. They present the discovery of a cave and the results of its exploration, confirming its use by Pleistocene hunter-gatherers.

Tracing provenance of eolian sands in the northern Ulan Buh Desert, China: Evidence from the REE geochemical characteristics

Desertification is a primary threat to crop farming, the livestock industry, and the eco-environment in northwestern China. Through field research and satellite imagery, it has been discovered that there are 4–5 sand belts in the shape of handclasps connecting major deserts in the Alxa Plateau region of northern China. These sand belts have been expanding for several decades. However, eolian sand transport between major deserts through these expanding sand belts is still underestimated. Identifying the source areas of eolian sands in deserts provide essential knowledge to prevent desertification. In this study, we collected samples from the northern Ulan Buh Desert (UBD), the Yamalik Desert (YD), and the Langshan Mountains and analyzed their REE contents in the <125 μm fraction. We compared REE geochemical characteristics of fine-grained sands in the UBD with other recently published REE data for potential source areas. Our findings indicate that the primary origins of fine-grained sands in the northern UBD are from the Qilian Mountains (QM) and Badain Jaran Desert (BJD), which are transported through the YD. Contributions from the Gobi-Altay Mountains to the north are relatively minor. The Langshan Mountains and Hawula Mountains are not considered as the primary sources of fine-grained sands in the UBD. In contrast, surface sediments in the southern UBD have a local mixture of the paleo-lacustrine deposits, the Gobi sediments, and minor external inputs from the BJD and QM. Our findings demonstrate that sand belts connecting these deserts play a crucial role in the eolian transport of fine-grained sands. Therefore, both the Chinese government and scientists should pay close attention to them in future efforts to combat desertification.

Mapping human mobility and analyzing spatial memory: palimpsest landscapes of movement in the Gobi-Altai Mountains, Mongolia

The significance of local spatial choices and memory and their impact on mobility networks is scarcely recognised in Mongolian archaeology. Here, we present a mapping strategy aimed at disentangling the landscapes of movement and investigating the materiality that accumulated in the palimpsest of the Ikh Bogd Uul Mountain (Bayankhongor, Mongolia).Based on an integrated and diachronic approach, our analysis encompasses a variety of strategies and sources: satellite imagery and historical cartography, a rescaling of the research area and path-centered fieldwork, which we conceptualize as 'linear’ survey. We document Late Prehistoric mounds as well as ‘modern’ springs, pastoral campsites, and paths. They are interpreted as landscape-objects associated with persistent mobility patterns and the construction of local knowledge and identity – in the sense of a nutag or homeland.This study thus contributes to expanding the archaeological information available for a remote and scarcely investigated area and enriching the archaeological approach to a complex and highly mobile context over time. It also offers new insights into how ancient mobility contributed to shaping the local landscapes of movement, both in terms of seasonal pastoral shifts and long-distance networks in the Mongolian and Central Eurasian Late Prehistory and afterwards.

THE FIRST REPORTED PLEISTOCENE BEAVER, &lt;i&gt;Castor fiber&lt;/i&gt; (CASTORIDAE, RODENTIA), FROM THE GOBI ALTAI REGION OF MONGOLIA

Here, we report a fragmentary Castor fiber (Linnaeus, 1758) proximal ulna from Tsagaan Agui Cave (Gobi Altai Mountains, southern Mongolia). This constitutes the first fossil evidence of this species from Mongolia. C. fiber is currently regarded as extinct in the Gobi Desert but fossilized remains recovered from cave deposits provide evidence that optimal habitat conditions for C. fiber existed in the Gobi Desert during some periods of the Pleistocene. Pleistocene C. fiber remains are relatively rare in neighboring regions, including Siberia and the Russian Far East. Here, we review the geographical distribution of fossil C. fiber in Central Asia, southern and eastern Siberia, and the Russian Far East.

Provenance of Quaternary aeolian silts in western China and its spatial difference with source of the Yellow River sediments

Quaternary aeolian silts in the Chinese Loess Plateau (CLP) has long been regarded as a product of sand ablation during the process of transportation originally from sandy deserts of northern China and Mongolian Gobi deserts driven by winter monsoon. Recently, this traditional idea was challenged by a new idea that aeolian silts in the CLP were emitted from fluvial sediments in the middle reaches of the Yellow River which was originally transported from the Tibetan Plateau ascribed to intensified Asian summer monsoon. We systematically determined the origin of Quaternary aeolian silts in a 318-m-thick loess/palaeosol sequence by using U–Pb age spectrum of detrital zircon grains, and compared it with Quaternary fluvial sediments on the Yellow River terraces in Lanzhou, western CLP. The aeolian silts were originated from Qilian Mountains in Northeastern Tibetan Plateau since 1.4 Ma with exception in the intervals of 1.02–0.93 Ma, ∼0.75 Ma and ∼0.06 Ma when aeolian silts were originated from Gobi-Altai Mountains. In contrast, Quaternary fluvial sediments of the Yellow River were mainly originated from Songpan block south to the Qilian Mountains. We propose that the Quaternary aeolian silts in western CLP were emitted and transported by winter wind circulation from piedmonts of the Qilian Mountains more than by the Yellow River from the Songpan block to the south. This study promotes the recognition in terms of the source of the Quaternary aeolian silts in western China.

Petrology and geochronology of andalusite- and sillimanite-bearing kyanite metapelites from the Gobi Altai Mountains: Evidence for prolonged convergent tectonics in the Central Asian Orogenic Belt

To further constrain the tectonic evolution of the convergent margin of the West Mongolian segment in the Paleo–Asian Ocean, we have investigated coarse-grained kyanite metapelites associated with quartz veins in the Gobi Altai Mountains, Mongolia, where the metamorphic belt is in a thrust contact with a Paleozoic accretionary complex. The metapelites contain coarse-grained granoblastic kyanite grains that are surrounded by sillimanite (Sil-II) with moat-like andalusite (And-II). The garnet grains in the garnet-bearing kyanite metapelites contain inclusions of andalusite (And-I) in their cores and sillimanite (Sil-I) in their mantles. Detailed textural characterization of the aluminosilicate phases indicates five distinct generations in the sequence andalusite (And-I), sillimanite (Sil-I), kyanite (Ky), sillimanite (Sil-II), and andalusite (And-II). Thermobarometric calculations and thermodynamic modeling suggest a hairpin-shaped P–T evolution with prograde conditions starting from ~530 °C at 3.5 kbar, reaching a peak of 600 °C at 6 kbar, and then a retrogression to ~550 °C at 4 kbar. U-Pb zircon and U–Th–Pb monazite ages indicate that the multistage aluminosilicate formation has occurred during c. 260–245 Ma. The detrital zircon age distribution is essentially similar to those in the accretionary sedimentary rocks from the entire Altai Range (a sharp peak at 550–490 Ma and a broad peak at 900–700 Ma), but is characterized by more abundant Proterozoic zircon grains and an older maximum deposition age (Early Ordovician) compared with Devonian pelitic gneisses in the Mongolian Altai. These petrological and geochronological results indicate the following development of the orogen: (1) Subduction of an oceanic plate beneath a microcontinental block as early as 550 Ma, evidenced by the youngest peak of detrital zircon ages. (2) Development of the accretionary wedge and volcanic front due to maturation of the arc until c. 360 Ma. The development of the volcanic front due to the magmatism has provided abundant Paleozoic detritus to the accretionary wedge and has stemmed supply of Proterozoic detritus from the inland at the same time. (3) Burial of the youngest accretionary wedge at c. 360–350 Ma, which is not observed in the current samples. Ridge subduction has also been suggested to have occurred in this period. (4) Arc magmatism in the upper (older) part of the accretionary wedge during the late Permian that resulted in prograde high-T and low-P metamorphism (formation of And-I). (5) Burial of the heated accretionary wedge to a depth of ~20 km due to subsequent collision (formation of Sil-I and Ky) at c. 260 Ma. (6) Rapid exhumation of the buried accretionary wedge to a shallow depth by thrusting (formation of Sil-II and And-II) at c. 245 Ma. In summary, the metapelites in the Altai Range clearly preserve the evolution of both the accretion and collision events as well as their transformation processes, which are likely to be a good natural example of the Wilson cycle for a period of ~300 Myr.

Gobi Altai, Khangai and Khentii Mountains mapped by a mixed-method cartographic approach for comparative geophysical analysis

Geologic and geophysical mapping has been so far limited to the traditional single-method GIS-based mapping. A new approach combining integrated analysis of data on geology, gravity, topography and geomorphology is presented for regional characterization of the geophysical setting in Mongolia: the Gobi Altai Mountains, the Khangai Mountains and Khentii Mountains with surrounding areas. Nine new maps have been produced from the high-resolution datasets: GEBCO, gravity raster, USGS geological data and SRTM-90 DEM geomorphological grid. Methodology includes three tools for cartographic data visualization: i) Generic Mapping Tools (GMT), ii) R programming language (‘raster’ and ‘tmap’ libraries); iii) QGIS. The results demonstrated strong agreement between the estimated values in gravity and topography grids, distribution of geological units and provinces over the country and geomorphological landforms with respect to the mountain ranges: Altai, Khangai and Khentii Mountains. The highest values in the gravity anomalies correspond to the mountain ranges in the Altai Mountains and Khangai Mountains (&lt;80 mGal); high values correspond to the Khentii Mountains (20–60 mGal). Contrariwise, the basins of the Uvs Nuur and Khyargas Nuur show negative values (&lt;-80 mGal). The NE- to NNE-oriented faulting and rift basins are clearly visible in the geophysical grids and geologic maps. The geomorphometric analysis performed based on the SRTM-90 DEM using R scripting demonstrated (1) slope, (2) aspect, (3) hillshade and (4) elevation models of Mongolia supported by histograms of data distribution and frequency. The study contributed to the cartographic methods and regional geological studies of Mongolia.

Decoupling of the detrital linkage between proximal dunefields and early and middle Pleistocene accumulation in the Chinese Loess Plateau: evidence from the Badain Jaran and Tengger sandy deserts

The dunefields upwind of the Chinese Loess Plateau (CLP) are widely regarded as the major source of the sediments of the CLP. To test this inference, we conducted a source tracing study using U–Pb age spectra of detrital zircons from the central Badain Jaran Desert (BJD). The results reveal that since 1.1 Ma the sediments in the central BJD have originated predominantly from the Gobi-Altay Mountains (GAMs), with a dominant Northern Tibetan Plateau (NTP) provenance at ∼0.7 Ma and at the present. Together with a previous study of the neighboring Tengger Desert (TD), our results support the conclusion that during 2.35–0.62 Ma the central parts of the proximal dunefields of the BJD and TD acted as reservoirs of sediments deflated mainly from strata with a GAMs-origin, with the addition of NTP-derived sediments after 0.36 Ma. Comparison of the original provenance areas of sediments in the central parts of the BJD and TD with the loess deposits in the central and southern CLP indicates that the proximal dunefields of the BJD and TD were not the dominant sources of dust transported to the CLP during early to middle Quaternary. Based on our results, combined with evidence from previous studies, we propose that NTP-derived sediments dominated accumulation in the CLP for most of the Quaternary, while during 2.35–0.62 Ma the proximal dunefields, including the BJD and TD, acted only as reservoirs of sediments deflated and eroded predominantly from the GAMs. Essentially, these sandy deserts functioned as transfer stations, which, after ∼0.36 Ma, received increased amounts of NTP-derived sediments and subsequently supplied silt to downwind areas, including the CLP.

Archaeological and environmental cave records in the Gobi-Altai Mountains, Mongolia

Though hundreds of caves are known across Mongolia, few have been subject to systematic, interdisciplinary archaeological surveys and excavations to understand Late Pleistocene and Holocene environments. Previous cave excavations in Mongolia have demonstrated their potential for preservation of archaeological and biological material, including Palaeolithic assemblages and Holocene archaeology, particularly burials, with associated organic finds. In other cases, cave surveys found that stratigraphic deposits and archaeological materials are absent. The large number of caves makes the Mongolian Altai Mountain Range a potentially attractive region for human occupation in the Pleistocene and Holocene. Here we present the results of an interdisciplinary survey of caves in four carbonate areas across the Gobi-Altai Mountains. We report 24 new caves, some of which contain archaeological material recovered through survey and test excavations. Most caves presented limited sedimentation, and some were likely too small for human habitation. Six caves showed evidence of palaeontological remains, most likely from the Late Holocene and recent periods. The most notable anthropogenic findings included petroglyphs at Gazar Agui 1 & 13. Gazar Agui 1 also contained lithics and a bronze fragment. Tsakhiryn Agui 1 contained 31 wooden fragments that include an unused fire drilling tool kit and items commonly found in association with medieval burials. We observed that the caves remain in contemporary use for religious and economic purposes, such as the construction of shrines, mining and animal corralling. Water samples from the caves, and nearby rivers, lakes, and springs were analysed for their isotopic compositions (δ18O, δD, δ17O, 17Oexcess, d-excess) and the data, combined with backward trajectory modelling revealed that the Gobi-Altai region receives moisture mainly from western sources. These results form a baseline for future archaeological, palaeoclimate and palaeoecological studies about regional seasonality and land use.

Материалы пещеры Цагаан-Агуй из отложений голоценового возраста (по результатам раскопок 2021 года)

Tsagaan Agui Cave, situated in Tsagaan Tsakhir limestone massif in the Gobi Altai Mountains of southern Mongolia, is the one of the rare stratified Holocene archaeological sites known in the Gobi Desert. During 1995-2000 excavation campaigns, cultural material spanning the late Bronze Age through the ethnographic present was recovered. In 2021, an excavation pit (2021/1) was dug in the gallery that joints the cave’s Main and Small Chambers, and an additional sondage (2021/2) was excavated in the Main Chamber itself. Excavation Unit 2021/1 is subdivided into Layers 1, 2, and 3, in which Layers 1 and 2 are attributed to the Holocene, and 3, the lowermost, is likely of Pleistocene age. Birch barkfragments bearing Old Mongolian inscriptions, cylindrical paste beads, and one additional, presumably carnelian, bead were found in Layers 1 and 2. Excavation Unit 2021/1, Layers 1-3, yielded lithic artifacts made of yellow jasper and Devonian flint, typical of the local Paleolithic industry. Only a single transparent chalcedony microblade can be tentatively dated to the Holocene. The suite of Holocene cultural material obtained during the 2021 excavations at Tsagaan Agui requires additional analysis and interpretation and is of particular interest with respect to the reconstruction of late prehistoric trade networks linking arid southern Mongolia with remote regions and the appearance of historical documents in the Gobi Desert. The study of the Holocene layers at Tsagaan Agui Cave is also of timely significance in terms of preserving Mongolian cultural heritage, since the upper layer of the site is being destroyed due to unregulated and unsupervised tourist activity in spite of its relatively remote location.

Результаты нового цикла раскопок пещеры Цагаан-Агуй в Гобийском Алтае в 2021 году

Middle and Upper Paleolithic human migrations and dispersals throughout Central Asia are usually associated with middle altitudes and mild steppe and forest-steppe environments with herds of large game mammals. However, since at least the Middle Paleolithic, human populations penetrated areas of Central Asia characterized by extreme arid climatic and environmental conditions in modern times. Investigation of archaeological sites in such regions demands understanding whether Pleistocene environmental conditions were more favorable to human habitation, what types of adaptation pressures human populations faced, and what kinds of adaptive mechanisms were developed. The Gobi Desert and Gobi Altai Mountains of southern Mongolia comprise one such region. Exposed and stratified Paleolithic sites there include Tsagaan Agui Cave and a variety of surface occurrences. Middle and Upper Paleolithic archaeological complexes at Tsagaan Agui are associated with various faunal species recovered in situ from sediments, allowing the reconstruction of the paleoenvironmental conditions of human habitation there. Following trilateral excavations conducted at Tsagaan Agui in 1995-2000, the longitudinal profile of the cave was uncovered in 2021 to collect sediments and other samples and a small test pit was excavated in the cave’s main chamber. Layers 2.1-4 of Test Pit 2021/2 yielded a bone industry, Paleolithic art mobilier, and a small collection of lithic artifacts, all in stratigraphic context. Evidence of episodic hyaena occupation was also revealed in Layer 2.2. The 2021 Tsagaan Agui Cave excavation campaign provides clear rationale for further investigation of this site, especially excavations in the northern part of the cave that has not been previously studied, as well as garnering additional data for refined paleoclimatic and paleoenvironmental reconstructions.

Provenance variations of the Tengger Desert since 2.35 Ma and its linkage with the Northern Tibetan Plateau: Evidence from U-Pb age spectra of detrital zircons

Knowledge of variations of the sedimentary sources of the proximal deserts of the Chinese Loess Plateau (CLP) is important for understanding eolian processes linking environmental changes within provenance areas and the areas of deposition downwind. In addition, it may shed light on the history of the uplift of the Tibetan Plateau. However, the long-term variations in provenance of the proximal deserts of the CLP are still unknown. The Tengger Desert (TD) is one of the proximal deserts upwind of the CLP. It is located in a depression (also a plateau) on the northeastern margin of the Northern Tibetan Plateau (NTP) and to the south of the Gobi Altay Mountains (GAMs). Here, we present U-Pb age spectra of detrital zircon grains from 11 sand layers from core BJ14 which was drilled in the northwestern part of the TD. The ages of the sand layers range from 2.35 to 0.11 Ma. The results indicate that: (1) The GAMs and NTP were two competing provenance areas of sands in the TD. (2) The dominant provenance area of clastic materials in the TD area was GAMs during 2.35–1.80 and 1.2–0.6 Ma, and the NTP at ∼1.56 Ma and during 0.36–0.11 Ma. The shift in the dominant provenance area in the TD from the GAMs to the NTP was controlled by the phased uplift of the Tibetan Plateau against the background of global cooling. (3) The relative increase of the sedimentary contribution from the NTP was generally synchronous with increases in the accumulation rate and the enlargement of eolian sand/dust deposits downwind, but the increase began at a late stage in the phased uplift of the Tibetan Plateau. These findings indicate that the phased rapid uplift of the NTP was a trigger which dominated the variations in the provenance of the proximal deserts of the CLP and beyond.

A Levalloisian jasper cache from the Arts Bogdyn Nuruu massif in the Gobi Altai Mountains, southern Mongolia

A Pleistocene deposit of jasper cores was discovered in the Gobi Altai Mountains, within the Arts Bogdyn Nuruu massif in southern Mongolia. It was situated on a mountain ridge above the Khutul Usny valley at a height of ca. 1500m a.s.l., away from human settlement (N44°16′09.3″, E102°53′41.5″). Examination of traces of the artefacts’ use proved that at least some of them display evidence of working. Technological analysis of the artefacts revealed that the find should be related to the Levallois-Mousterian population of the central Asian Middle Palaeolithic. The cache from Arts Bogdyn Nuruu is the first discovery of this type recorded within the Gobi Desert. It is a potential source of information contributing to the discussion of the specific nature of raw material exploitation, the dynamics of settlement and hunting strategies in the Altai region.

High-resolution simulation of Asian monsoon response to regional uplift of the Tibetan Plateau with regional climate model nested with global climate model

Abstract Using the high-resolution regional climate model–Weather Research and Forecasting model(WRF)–nested within the National Center for Atmospheric Research Community Atmosphere Model(CAM4), a set of sensitivity experiments were conducted to investigate the Asian climate response to the regional uplift of the Tibetan Plateau (TP). The results indicated that the presence of Asian orography, including the TP, strengthened both the Indian and East Asian summer monsoon (ISM and EASM), respectively. The uplift of the central-southern TP and western TP caused an asynchronous response of monsoon precipitation over India and East Asia, while the presence of the Himalayan mountains, Gobi Altai mountains, and Mongolian Plateau increased both ISM and EASM precipitation. The enhanced summer monsoon precipitation over southeastern China due to the TP uplift was caused by strong water vapor transportation, vapor convergence and ascending movement. The Indian and East Asian winter monsoons (IWM and EAWM), however, showed asynchronous change in response to the TP uplift; the EAWM was strengthened, but the opposite holds for the IWM. This study provides further understanding of the response of Asian monsoons to the regional uplift of the TP and emphasizes the importance of high-resolution regional climate model simulation nested within global climate model.

Aspects of late Quaternary geomorphological development in the Khangai Mountains and the Gobi Altai Mountains (Mongolia)

The reconstruction of geomorphological processes as a result of environmental change is approached by investigating and dating some fluvial, aeolian and lacustrine archives at specific locations that form a N-S basin and range transect across the Khangai Mountains south to the eastern Gobi Altai mountains in Mongolia. Geomorphological processes varied a) spatially with different climatic conditions and vegetation cover in relation to different elevation and latitude and b) temporally due to climatic shifts during the late Quaternary. In total, 15 sections from three distinct sub-regions along that transect were dated by 22 OSL ages. The Khangai Mountain sub-region exhibits mainly late Glacial to Holocene aeolian silty to sandy cover sediments mainly in the upper catchment reaches (>1800 m a.s.l.). Sections in the northern and central Gobi represent river terraces and alluvial fans in basin areas as well as aeolian sediments in the mountains above 2200 m a.s.l. The oldest terrace surface found in this study (T2; NGa1) dates to the penultimate Glacial cycle. The T1 terrace surfaces, on the northern Khangai Mountain front and in the central Gobi sub-region yield a maximum accumulation during the global Last Glacial Maximum (gLGM) and late Glacial time. During the gLGM phase represents rather sheetflow dominated transport built the alluvial fans and in late Glacial times the sediments exhibit more debrisflow controlled accumulation. Incision, forming the T1-terrace edges is therefore, supposed for the Pleistocene-Holocene transition and subsequent early Holocene. The geomorphic evidence is interpreted as stronger fluvial morphodynamics induced by enhanced humidity under beginning interglacial conditions. These processes coincided with the development of aeolian mantles at higher altitudes in the Khangai and Gobi Altai mountains where higher temperatures and humidities supported the formation of a vegetation cover, that served as a dust trap at least since late Glacial times and reduced the sediment supply on the alluvial fans.

Quantitative estimation of the contribution of dust sources to Chinese loess using detrital zircon U‐Pb age patterns

AbstractThe origin and provenance of the loess deposits of the Chinese Loess Plateau (CLP) are still debated. In order to pinpoint the dust sources, surface samples from the piedmont of the Northeastern Tibetan Plateau, the Gobi Altai Mountains, and modern eolian dunes from the Tengger desert and Mu Us sand field were analyzed by using the detrital zircon dating technique. In order to quantitatively discriminate the content of different potential sources, zircon grains of different ages were grouped according to their tectonic origin. Zircon grains aged from 1300 to 550 Ma were assigned to the Northeastern Tibetan Plateau, and grains aged from 550 to 0 Ma to the Northeastern Tibetan Plateau or the Gobi Altai Mountains, or to a combination of the two. Zircon ages of around 2.8 Ga to 1.3 Ga may be a mixture of sources from the Northeastern Tibetan Plateau, Gobi Altai Mountains, or North China Craton. Sediments from the Tengger desert and Mu Us sand field consist of a mixture of the three sources and exhibit a high degree of spatial variability in terms of their source. In the northern part of the two deserts, 43–83% of the sediments are derived from the Gobi Altai Mountains, while in the south, material from the Northeastern Tibetan Plateau comprises 51–98% of the sediments. Loess deposits from the CLP also comprise a mixture of the three different sources, with material from the Northeastern Tibetan Plateau making the dominant contribution (65–100%), with material from the North China Craton and the Gobi Altai Mountains comprising 0–35% and 0–40% of the loess deposits, respectively. The contributions from the three sources to the loess deposits on CLP vary spatially. Application of the novel statistical method of provenance group analysis demonstrates that the loess deposits comprise a mixture of material from a broad region of northern China and that the Northeastern Tibetan Plateau material makes the dominant contribution.

Shifting material source of Chinese Loess since ~2.7 Ma reflected by Sr isotopic composition.

Deciphering the sources of eolian dust on the Chinese Loess Plateau (CLP) is fundamental to reconstruct paleo-wind patterns and paleo-environmental changes. Existing datasets show contradictory source evolutions of eolian dust on the CLP, both on orbital and tectonic timescales. Here, the silicate Sr and Nd isotopic compositions of a restricted grain size fraction (28–45 μm) were measured to trace the source evolution of the CLP since ~2.7 Ma. Our results revealed an unchanged source on orbital timescales but a gradual source shift from the Qilian Mountains to the Gobi Altay Mountains during the past 2.7 Ma. Both tectonic uplift and climate change may have played important roles for this shift. The later uplift of the Gobi Altay Mountains relative to the Qilian Mountains since 5 ± 3 Ma might be responsible for the increasing contribution of Gobi materials to the source deserts in Alxa arid lands. Enhanced winter monsoon may also facilitate transportation of Gobi materials from the Alxa arid lands to the CLP. The shifting source of Asian dust was also reflected in north Pacific sediments. The finding of this shifting source calls for caution when interpreting the long-term climate changes based on the source-sensitive proxies of the eolian deposits.

Binary sources of loess on the Chinese Loess Plateau revealed by U–Pb ages of zircon

The age distribution of detrital zircon has been used to trace sediment sources. Existing datasets show great similarity of zircon ages between the loess on the Chinese Loess Plateau (CLP) and the sediments from the North Tibetan Plateau (NTP), implying that eolian dust is delivered from the NTP to the CLP by westerly winds or via the Yellow River. However, NTP dust can also be transported by northwesterly winds from the Alxa arid lands (AALs), where materials are received from both the NTP and the Gobi Altay Mountains (GAMs). Here we report U–Pb zircon ages for AALs sands and NTP and CLP loess. The results show that the zircons in the AALs are mixed from NTP and GAMs zircons. NTP loess is mainly derived from local sources. Mixing of materials from the NTP and GAMs defines the zircon ages of the loess on the CLP better than the pure NTP source. No temporal and spatial heterogeneities of zircon ages have been observed for the loess on the CLP, which suggests that the well-mixed materials in the AALs likely have an eolian source.

Evolving sources of eolian detritus on the Chinese Loess Plateau since early Miocene: Tectonic and climatic controls

The thick deposits of eolian dust on the Chinese Loess Plateau provide a rare opportunity to explore the past changes of surface processes in response to climatic and tectonic oscillations. Here we report a 22Ma-long Nd and Sr isotopic records of the eolian sources. Decreasing εNd values and increasing 86Sr/87Sr ratios of the eolian deposits has been observed from early Miocene to about 7Ma, which indicates growing material contribution from Qilian Mountains relative to the Gobi Altay Mountains. The source shift during 22–7Ma is interpreted to reflect the erosional response of the Qilian Mountains to its surface uplift. Between 7Ma and 1.2Ma, the results show relative constant Nd and Sr isotopic compositions of the eolian deposits, and thus suggest a constant source contribution between Qilian Mountains and Gobi Altay Mountains. Synchronized uplift of the two mountain ranges during this period may explain the constant ratio of source contribution. Since 1.2Ma, Nd and Sr isotopic records indicate that the relative debris input from Qilian Mountains drops rapidly. As large-scale topographic changes would not be expected in such a short time period, the source shift since 1.2Ma might be by the differing erosional responses in Qilian Mountains and Gobi Altay Mountains to the development of full glacial climate after the middle Pleistocene transition. This work shows that combined Nd and Sr isotopic signatures of the dust records are valuable proxies to monitoring past surface processes on the million years time scale.