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Chinese loess deposits provide a valuable archive of East Asian monsoon variations and compare well with marine oxygen isotope records. However, post-depositional pedogenesis disturbances during some long and warm interglacials may decrease the time resolution and recording efficiency of loess deposits. In this study, we build a simple multiple-state model that involves deposition and pedogenesis processes to simulate loess-paleosol grain size variations and evaluate the recording efficiency under the impact of pedogenesis disturbance. Meanwhile, the modeling results are compared with the measured grain size time series of Xifeng profile from the center of the Chinese Loess Plateau (CLP). The results show that the recording efficiency of the loess deposits in the central CLP has been stepwise enhanced since the early Pleistocene. High-latitude signals in the Chinese loess record between 2.5 and 1.6 Ma were partly erased by post-depositional pedogenesis and only those from several intense glacial periods remain better preserved. Three finer-grained loess units appear at ~550 ka (marine isotope stage (MIS) 14), ~1045 ka (MIS 30), and ~1500 ka (MIS 52), which were likely caused by low dust accumulation rates, suggesting the moderate growth of ice sheets in the Northern Hemisphere. After the mid-Pleistocene transition (~0.9 Ma), the occurrence of grain size changes related to precessional cycles within the long-term glacial periods did not appear in our modeling results. Such variations may thus represent changes of the dust source areas controlled by the East Asian summer monsoon. However, the suppression of precessional variations in the major paleosol layers indicates that loess deposits at least in the central CLP are a low time-resolution archive for capturing precession-scale paleoclimatic changes during interglacial periods.

The Wufo Basin at the margin of the northeastern Tibet Plateau connects the upstream reaches of the Yellow River with the lowland catchment downstream, and the fluvial terrace sequence in this basin provides crucial clues to understand the evolution history of the Yellow River drainage system in relation to the uplift and outgrowth of the Tibetan Plateau. Using field survey and analysis of Digital Elevation Model/Google Earth imagery, we found at least eight Yellow River terraces in this area. The overlying loess of the highest terrace was dated at 1.2 Ma based on paleomagnetic stratigraphy (two normal and two reversal polarities) and the loess-paleosol sequence (12 loess-paleosol cycles). This terrace shows the connections of drainage parts in and outside the Tibetan Plateau through its NE margin. In addition, we review the previously published data on the Yellow River terraces and ancient large lakes in the basins. Based on our new data and previous researches, we conclude that the modern Yellow River, with headwaters in the Tibet Plateau and debouching in the Bohai Sea, should date from at least 1.2 Ma. Ancient large lakes (such as the Hetao and Sanmen Lakes) developed as exorheic systems and flowed through the modern Yellow River at that time.

Previous researches had emphasized tectonic impacts on the fluvial system at the tectonically active areas, while the effects of lithology and local base level change have received relatively rare attention. Here we investigated fluvial landforms at different spatial scales, focusing on knickpoints and channel network reorganization from an area affected by the Haiyuan Fault in the northeastern Tibetan Plateau. The geomorphic indices, i.e., drainage pattern and χ anomalies, were calculated and investigated. The results show that two regional radial drainages formed around the Laohu and Hasi Mountains. Within the interior of the radial drainage, tributaries from the southeast side of the Laohu Mountain experienced near 180° direction change. We interpret this as the gradual drainage capture originating from the height difference (~190 m) of the local base level between the two catchments. Some tributaries from the Hasi Mountain show alternating gorges and broad valleys controlled by lithology. Besides, tectonic uplift and the lowering of base level (from the incision of the Yellow River) triggered an autogenic positive-feedback transition from parallel to dendritic drainage patterns. These observations suggest that base level change and lithology play a crucial role in landscape evolution, even in a tectonically active region.

This paper describes an assemblage of diverse floodplain facies of reworked loess (facies b, c) in a Middle Pleistocene monsoonal setting of the Hanzhong Basin, central China. The vertical and lateral sedimentary sequences show changing energy conditions. Apart from the highest energy in the channel facies (facies a), a relatively high energy floodplain environment (facies b) prevailed in waterlogged conditions, with small, laterally migrating (sub)channels. Facies b generally interfingers with aggrading horizontal sheets of overbank deposits in alluvial pools and swamps in a floodplain with much lower energy (facies c), in which phases of stability (soil formation) occasionally interrupted overbank deposition. Reworked loess forms the main part of the floodplain deposits. The paleosols are considered to have been formed under low hydrodynamic conditions in an interglacial environment. These interglacial conditions follow the commonly assumed glacial conditions of channel facies a. The sedimentary successions in the floodplain show a recurrent composition and cyclicity between wet and dry floodplain sedimentation terminated by stability with soil formation. The cyclic rhythm of stacked high- and low-energy floodplain sediments is attributed to varied intensity of different hydrodynamic flooding events that may have been due to changing monsoonal rainfall or simple intrinsic fluvial behavior.

We investigate the phased evolution and variation of the South Asian monsoon and resulting weathering intensity and physical erosion in the Himalaya–Karakoram Mountains since late Pliocene time (c.3.4 Ma) using a comprehensive approach. Neodymium and strontium isotopic compositions and single-grain zircon U–Pb age spectra reveal the sources of the deposits in the east Arabian Sea, and show a combination of sources from the Himalaya and the Karakoram–Kohistan–Ladakh Mountains, with sediments from the Indian Peninsula such as the Deccan Traps or Craton. We interpret shifts in the sediment sources to have been forced by sea-level changes that correlate with South Asian monsoon rainfall variation since late Pliocene time. We collected 908 samples from the International Ocean Discovery Program Hole U1456A, which was drilled in the east Arabian Sea. Time series of hematite content and grain size of the sediments were examined downcore. We found South Asian monsoon precipitation and weathering intensity experienced three phases from late Pliocene time. Lower monsoon precipitation, with a lower variability and strong weathering intensity, occurred during 3.4–2.4 Ma; an increased and more variable South Asian monsoon rainfall, along with strengthened but fluctuating weathering intensity, occurred at 1.8–1.1 Ma; and a reduced rainfall with lower South Asian monsoon precipitation variability and moderate weathering intensity marked the period 1.1–0.1 Ma. Maximum entropy spectral analysis and wavelet transform show that there were orbital-dominated cycles of periodsc.100 andc.41 ka in these proxy-based time series. We propose that the monsoon, sea level, global temperature and insolation together forced the weathering and erosion in SW Asia.

Variability in East Asian summer monsoon precipitation during the Holocene remains of debate. In this study, we use a closed lake with well‐dated lake beach ridges located on the margin of the East ...

Northeast China lies in the transition zone from the humid monsoonal to the arid continental climate, with diverse ecosystems and agricultural land highly susceptible to climate change. This region has experienced significant greening in the past three decades, but future trends remain uncertain. In this study, we provide a quantitative assessment of how vegetation, indicated by the leaf area index (LAI), will change in this region in response to future climate change. Based on the output of eleven CMIP6 global climates, Northeast China is likely to get warmer and wetter in the future, corresponding to an increase in regional LAI. Under the medium emissions scenario (SSP245), the average LAI is expected to increase by 0.27 for the mid-century (2041–2070) and 0.39 for the late century (2071–2100). Under the high emissions scenario (SSP585), the increase is 0.40 for the mid-century and 0.70 for the late century, respectively. Despite the increase in the regional mean, the LAI trend shows significant spatial heterogeneity, with likely decreases for the arid northwest and some sandy fields in this region. Therefore, climate change could pose additional challenges for long-term ecological and economic sustainability. Our findings could provide useful information to local decision makers for developing effective sustainable land management strategies in Northeast China.

The Asian monsoon variations under global temperature changes during the Pliocene are still debated. Here we use a sedimentary record of phytoliths (plant silica) from the Weihe Basin, central China, to explore the history of C4 grasses and quantitatively reconstruct the Asian monsoon climate since the late Miocene. Our results show that C4 grasses have been a dominant grassland component since ~11.0 Ma. A subsequent marked decrease in warm- and humid-adapted C4 grasses and an increase in cool- and dry-adapted C3 grasses occurred in the Pliocene, ~4.0 Ma; the phytolith-based quantitative reconstruction of mean annual precipitation marked a decrease from 800~1673 mm to 443~900 mm, indicating a reduction in Asian monsoon rainfall in the Pliocene. Our newly obtained records conflict with the hypothesis that the growth of the Tibetan Plateau strengthened the Asian monsoon rainfall. Nevertheless, they emphasize the importance of global temperature as a determinant of Pliocene Asian monsoon variations., Asian summer monsoons and their links to global temperature changes have been the subject of intense debate. Here the authors reconstruct the Asian monsoon climate since the late Miocene, using plant silica records of C4 and C3 grasses in central China, and find that global cooling caused Asian monsoon rainfall to decrease markedly in the late Pliocene.

The Qinling Mountains (QLM) form the climatic boundary between the temperate north and subtropical south of China. Many important Paleolithic archaeological sites located on fluvial terraces in this area have been reported in recent decades. Abundant artifacts have been excavated in silt layers overlying fluvial gravels and coarse sands. These silt layers have thus far been interpreted as aeolian deposits. However, in principle they could also represent (in part) fluvial (floodplain) deposits, especially near the base of fine-grained sequences. Reconstruction of fluvial terrace formation is crucial for the correct interpretation of the environment of hominin occupation. In this paper, two sediment sequences from two Paleolithic sites, located on different terrace levels of the Hanjiang River in the Hanzhong basin, are studied mainly using grain-size and grain-shape analyses. In addition, grain-size distributions have been unraveled by applying end-member modelling to distinguish different sedimentary environments. The results show that three different units can be discriminated in each section. The lower unit, consisting of gravelly sand mixed with fine silt, is interpreted as shallow-channel-fill sediment deposited during the start of the transition from a channel to a floodplain environment. The middle unit comprises a fine-grained, gradually fining-upward sequence, representative a floodplain environment. At its base, it reflects a high-energy floodplain situation; at its top, the sequence is interpreted as a low-energy floodplain environment with aeolian input (settling in static water). The third, uppermost unit consists of aeolian loess interbedded with paleosol(s) and sediments that are interpreted as the results of episodic surface runoff. The gradual transition between the 3 units and the gradual fining upward trend of the middle unit indicates that there is no considerable age gap (no hiatus) between the fluvial- and aeolian sedimentary environments. Stone artifacts have been found in all 3 units, with difference abundance, indicating that both the aeolian and floodplain depositional environments provided favorable living conditions. For the floodplain environment, the resources of water and raw materials (fluvial gravels) for tool making may have offered fundamental resources for hominin settlement. © 2019 Elsevier B.V.

Most cities in China have suffered severe atmospheric particulate matter (PM) pollution, with reduced visibility and worsened air quality. Fugitive dust that primarily originates from soils through the action of wind and anthropogenic activities is recognized to be a major source of urban PM. However, it remains challenging to quantify and parameterize fugitive dust emission from various sources due to a lack of observation data. In this study, a portable wind erosion system, PI-SWERL, was applied to characterize the dynamics and magnitude of PM10 and PM2.5 (particles smaller than 10 μm and 2.5 μm respectively) emissions from several possible sources in Nanjing, a typical large city in the Yangtze River Delta economic regions, East China. Results indicate that aerodynamic suspension and abrasion were two major physical mechanisms responsible for fugitive dust emissions, with varying characteristics by location. Changes of emission characteristics and quantities were primarily associated with differences in the supply of fine particles available for wind erosion, controlled by source-specific surface characteristics and anthropogenic disturbances. Construction sites and unpaved roads were identified as two significant sources, with total emission rates of 95.85 (56.97) and 57.22 (32.62) kg s−1 respectively for PM10 (PM2.5) at a friction velocity of 0.82 m s−1. These values were up to five times the amounts of PM emitted from arable lands and woodlands, and 1–2 orders of magnitude greater than those from paved roads, grasslands and bare lands. These data demonstrate the importance of construction sites and unpaved roads as local PM sources which might be significant in policy making for air quality management strategies and prioritization of emission control targets in an urban area.

Long marine sequences deposited in the Arabian Sea are suitable to study the orbital sensitivity of sediment dynamics from a source-to-sink perspective. The clay mineralogy and Sr Nd isotopic compositions have been analyzed for the detrital fraction of sediments from IODP Site U1457 located in the Laxmi basin, eastern Arabian Sea to constrain the sediment sources and reconstruct a high-resolution record of sediment export to the Indus deep-sea fan over the past 600 kyr. The 87Sr/86Sr ratio (varying from 0.7154 to 0.7255) and eNd (varying from −12.9 to −9.5) imply a mixing of sediments derived from not only the Indus River but also the rivers draining the Deccan Traps. The variations in the smectite/(illite + chlorite) ratio combined with Sr Nd isotopes permit the reconstruction of past changes in the relative proportions of sediments derived from the Indus River (mainly illite, chlorite and kaolinite) and the Deccan Traps (smectite). The wavelet and cross-spectral analyses further reveal that sediment transport to the eastern Arabian Sea since 600 kyr is mainly dominated by sea-level variations in the eccentricity (100-kyr) band, while the Indian summer monsoon might contribute moderately to the precession (23-kyr) band. The eNd and turbidite frequency indicate that more turbidite events are associated with Indus River-sourced sediments at IODP Site U1457 during sea-level lowstands, which might reflect a reconnection of deep-sea channels to the Indus River mouth and/or reworking of previously deposited Indus River sediments located northward.

The interaction of surface erosion (e.g., fluvial incision) and tectonic uplift shapes the landform in the Tibetan Plateau. The Lhasa River flows toward the southwest across the central Gangdese Mountains in the southern Tibetan Plateau, characterized by a low-relief and high-elevation landscape. However, the evolution of low-relief topography and the establishment of the Lhasa River remain highly under debate. Here, we collected thermochronological ages reported in the Lhasa River drainage, using a 3D thermokinematic model to invert both late Cenozoic denudation and relief history of the Lhasa River drainage. Our results show that the Lhasa River drainage underwent four-phase denudation history, including two-stage rapid denudation at ∼25–16 Ma (with a rate of ∼0.42 km/Ma) and ∼16–12 Ma (with a rate of ∼0.72 km/Ma). In the latest Oligocene–early Miocene, uplift of the Gangdese Mountains triggered the rapid denudation and the formation of the current main drainage of the Lhasa River. In the middle Miocene, the second stage of the rapid denudation and the high relief were associated with intense incision of the Lhasa River, which is probably due to the enhanced Asian summer monsoon precipitation. This later rapid episode was consistent with the records of regional main drainage systems. After ∼12 Ma, the denudation rate decreases rapidly, and the relief of topography in the central Gangdese region was gradually subdued. This indicates that the fluvial erosion resulting from Asian monsoon precipitation increase significantly impacts on the topographic evolution in the central Gangdese region.

The expansion of anatomically modern humans (AMHs) from Africa around 65,000 to 45,000 y ago (ca. 65 to 45 ka) led to the establishment of present-day non-African populations. Some paleoanthropologists have argued that fossil discoveries from Huanglong, Zhiren, Luna, and Fuyan caves in southern China indicate one or more prior dispersals, perhaps as early as ca. 120 ka. We investigated the age of the human remains from three of these localities and two additional early AMH sites (Yangjiapo and Sanyou caves, Hubei) by combining ancient DNA (aDNA) analysis with a multimethod geological dating strategy. Although U–Th dating of capping flowstones suggested they lie within the range ca. 168 to 70 ka, analyses of aDNA and direct AMS (14)C dating on human teeth from Fuyan and Yangjiapo caves showed they derive from the Holocene. OSL dating of sediments and AMS (14)C analysis of mammal teeth and charcoal also demonstrated major discrepancies from the flowstone ages; the difference between them being an order of magnitude or more at most of these localities. Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene. In light of our findings, the first appearance datum for AMHs in southern China should probably lie within the timeframe set by molecular data of ca. 50 to 45 ka.

Previous numerical–analytical approaches have suggested that the main range divide prefers to migrate towards the high uplift flank in the asymmetric tectonic uplift pattern. However, natural examples recording these processes and further verifying the numerical simulations results, are still lacking. In this study, the landscape features, and the probable drainage evolution history of the Zhongtiao Shan, a roughly west-east trending, half-horst block on the southernmost tip of the Shanxi Graben System, were investigated through the geomorphic analyses (i.e., slope and steepness distributions, and the Gilbert and χ metrics). The topographic slope and steepness results indicate that the Zhongtiao Shan, controlled by the north Zhongtiao Shan normal fault, experiences asymmetric uplift and erosion patterns, with higher uplift and erosion on the north range. In addition, the Gilbert and χ metrics suggest that the western part of the main divide is currently stable, while the eastern divide is moving southward. According to the drainage divide stability criteria, we suggest that the uplift and erosion, on the fault side, balance each other well on the western part of the range, while on the eastern part, the uplift is outpaced by the erosion. In addition, a dynamic divide migration model in the asymmetric uplift condition is proposed, indicating that the interaction between uplift and erosion controls the migration and/or stability of the main divide. Deducing through this dynamic model, we suggested that the eastern segment of the north Zhongtiaoshan Fault must have experienced higher activities in the geological history, and the western fault may remain its activity along with the mountain relief generation. This gives a case that specific information on asymmetric neotectonic history and landscape evolution in an orogenic mountain can be uncovered by the proposed dynamic model.

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change and surface processes which all adjust the ratio of sediment load to transport capacity ...

The people of the Tibetan Plateau have received extensive attention from scholars because of their unique adaptability to the low temperature and anoxic environments. However, the Tibetan communities and their habitats in the low-altitude regions of the plateau have rarely been studied in a scientific manner. Based on the extraction of geographic information of 197 towns in the Hehuang Valley and on variance analysis, this study examines the habitats and subsistence strategies of the Tibetans and other major ethnic groups in the low-latitude region of the Tibetan Plateau. Our statistical results show that the annual average temperature of Tibetan habitats in the Hehuang Valley is relatively high. The relatively warm environment of the valley allows the Tibetans in that area to cultivate wheat and barley and raise cattle and sheep—a subsistence strategy significantly different from that of other Tibetans in the high-altitude regions in the Tibetan Plateau. In addition, the Tibetan communities in the Hehuang Valley include similar agri-pastoral ethnic groups (including Hui and Salar), both of which adopt similar subsistence strategies. The agricultural ethnic groups (Han and Tu) live in a relatively cool and humid environment facilitating agricultural production, while the agri-pastoral ethnic groups (Tibetan, Hui, and Salar) inhabit relatively warm and arid environment in the valley. Due to the lack of agricultural activities, agri-pastoral groups must also engage in animal husbandry to supplement their diet. In the Ando Tibetan region, the subsistence strategies of the ethnic groups are closely related to their physical environment. Those ethnic groups communicate among themselves, integrate, and influence each other, resulting in a diversified culture. This study proves that the habitat variation at a regional scale corresponds significantly to the variation of subsistence strategies. Our findings may further refine knowledge about the human-environmental relationships of Tibetans and lead future research towards using quantitative methods to analyse the intersection of physical environment and ethnic groups’ distribution.

As a significant component of the global climate system, the East Asian monsoon (EAM) is crucial in understanding general climate change. The response of sensitivity and extent of the EAM to orbital-timescale climate change remains controversial. The composition of oxygen isotopes of authigenic (pedogenic) carbonate in loess deposits from the Northeastern Tibetan Plateau was measured, which is at the modern northwestern boundary of the present-day EAM, and compared with equivalent data from northeastern China under the influence of the EAM and two selected sites in the zone under the influence of the westerlies (Bayanbulak (Xinjiang) and Kesselt (Belgium)). The data enable discussion of the paleoclimatic implication of δ18O of carbonate in loess deposits and extension (changes) of the EAM-affected area during the Last Glacial Maximum and early Holocene. The δ18O values of authigenic carbonate at the Northeastern Tibetan Plateau were close to those from the westerly climate zone, but higher than those from regions affected by the Asian monsoon during the Last Glacial Maximum and early Holocene. This indicates that precipitation moisture sources at the Northeastern Tibetan Plateau were likely not directly derived from the EAM during Last Glacial Maximum and early Holocene. In contrast, the westerlies and locally recycled or evaporated moisture were possibly the dominant influencing factors of the relatively δ18O-enriched soil water and the authigenic carbonate in Northeastern Tibetan Plateau. Further study of loess carbonate records from the Northeastern Tibetan Plateau will reveal the past climate changes in the plateau region and provide valuable clues for the interaction between the Asian monsoon and westerly climate systems.

Alluvial-fan successions record changes in hydrological processes and environments that may reflect tectonic activity, climate conditions and changes, intrinsic geomorphic changes, or combinations of these factors. Here, we focus on the evolution of a stream-dominated fan in a tectonic depression of the Xining basin of China, laid down under a semi-arid climate in the northeastern Tibetan Plateau (NETP). The fan succession is composed of three facies associations, from bottom to top: (1) matrix to clast-supported, poorly sorted, planar cross-stratified to crudely stratified sheets of coarse-grained sediments, (2) horizontal laminated sand, laminated layers of reddish fine silt and yellow coarse silt with stacked mounds of sand, and (3) clay-rich deposits with incipient paleosols. The succession shows rapid sediment aggradation from high-energy to low-energy alluvial fans and finally to a floodplain. The dating results using optically stimulated luminescence (OSL) method show that a gravelly, high-energy fan was deposited during MIS 6, after which a low-energy fan, mainly composed of sand and silt, was deposited and finally covered by flood loam during the MIS 6&ndash, 5 transition and the warmer last interglacial. Stacked sand mounds are interpreted from their sediment structure and grain-size distribution as shrub-coppice dunes in low-energy fan deposits. They may be considered as a response to the interaction of alluvial and aeolian processes in a semi-arid environment.

The Hunshandake Sandy Land, which is highly sensitive to climate change, is located in North China along the margins of the area influenced by the East Asian monsoon. The upper reach of the Xilamulun River, which drains the Hunshandake Sandy Land, provides an opportunity to test the response of a river landform within a sandy region to climate change. We investigated terraces at 4 sites along a 38-km-long stretch and performed OSL dating on 26 terraces. The dating results revealed 23 terraces with unsaturated ages ranging from 0.3 ka to 36.2 ka. The observed relationship between the terrace heights and ages is abnormal, i.e., the terrace age does not increase with the terrace height. In this case, aeolian and fluvial interactions were analyzed, and a precipitation-dominated terrace formation model was developed. Higher terraces formed when the riverbed aggraded due to decreased sediment discharge and increased aeolian sand input during a period of reduced precipitation. In contrast, lower terraces developed when the riverbed eroded during a period of enhanced precipitation. We conclude that the terraces along this Hunshandake Sandy Land river respond to precipitation changes, even in the absence of background uplift.

Loess deposits are important archives of past climate change in subtropical China, where long-term terrestrial records are scarce. However, only a few long-term records with reliable dating were reported in Jiangsu Province, where loess deposits in southeastern China were first discovered and designated as the Xiashu Loess. Moreover, the provenance of the Xiashu Loess is still controversial. This study presents the magnetostratigraphy and detrital zircon U–Pb age results of loess deposits at Zhoujiashan in Nanjing, Jiangsu Province. To date, this section (with basal age of approximately 0.88 Ma) may be the oldest loess deposits discovered in southeastern China. Based on the detrital zircon U–Pb ages of the Zhoujiashan section, together with published results of geochemistry, geomorphology, sedimentology, and meteorology, we propose that the Xiashu Loess has two mixed sources. Local materials derived from the Yangtze River Basin (including exposed river/lake beds, floodplains, and mountains) served as a major contributor. The distal eolian dust that originated from the arid areas of North China (including deserts, piedmont alluvial fans, and drylands) played a minor role in the formation process of the Xiashu Loess. The nearly synchronous onset age (approximately 0.88–0.85 Ma) of the Xiashu Loess was attributed to a regional environmental event during the middle Pleistocene transition.

Projecting how the East Asian summer monsoon (EASM) rainfall will change with global warming is essential for human sustainability. Reconstructing Holocene climate can provide critical insight into its forcing and future variability. However, quantitative reconstructions of Holocene summer precipitation are lacking for tropical and subtropical China, which is the core region of the EASM influence. Here we present high-resolution annual and summer rainfall reconstructions covering the whole Holocene based on the pollen record at Xinjie site from the lower Yangtze region. Summer rainfall was less seasonal and ~ 30% higher than modern values at ~ 10–6 cal kyr BP and gradually declined thereafter, which broadly followed the Northern Hemisphere summer insolation. Over the last two millennia, however, the summer rainfall has deviated from the downward trend of summer insolation. We argue that greenhouse gas forcing might have offset summer insolation forcing and contributed to the late Holocene rainfall anomaly, which is supported by the TraCE-21 ka transient simulation. Besides, tropical sea-surface temperatures could modulate summer rainfall by affecting evaporation of seawater. The rainfall pattern concurs with stalagmite and other proxy records from southern China but differs from mid-Holocene rainfall maximum recorded in arid/semiarid northern China. Summer rainfall in northern China was strongly suppressed by high-northern-latitude ice volume forcing during the early Holocene in spite of high summer insolation. In addition, the El Nino/Southern Oscillation might be responsible for droughts of northern China and floods of southern China during the late Holocene. Furthermore, quantitative rainfall reconstructions indicate that the Paleoclimate Modeling Intercomparison Project (PMIP) simulations underestimate the magnitude of Holocene precipitation changes. Our results highlight the spatial and temporal variability of the Holocene EASM precipitation and potential forcing mechanisms, which are very helpful for calibration of paleoclimate models and prediction of future precipitation changes in East Asia in the scenario of global warming.

Nebkhas, also known as nebkha dunes or coppice dunes, are a unique biogeomorphological aeolian landform that is common in arid and semi-arid regions. They are often regarded as a signal of regional desertification and could be potential dust sources due to their relatively large content of fine sediments, but they also serve as “fertile islands” that enhance biodiversity at a micro-habitat. How the interactions between plant growth and aeolian sand deposition affect the formation and development of nebkhas has not been well documented, though. In this study, the chronology and morphological features of nebkhas in the Mu Us dune field, north-central China were studied using radionuclide (137Cs) dating and unmanned aerial vehicle (UAV) photogrammetric survey. The results show that the nebkhas are mainly distributed around lake basins and dry river valleys with relatively flat topography. Most nebkhas have heights around 0.5–1.5 m, and according to a new integrated age-height model, they mostly formed in the last fifty years. Widespread nebkha growth over that time is interpreted as a response to both desiccation of lake beds and river valleys and a pronounced decline in strong wind frequency. The regular rounded shape of the nebkhas in the study area may reflect the growth form of prostrate, extensively branched Nitraria tangutorum, the dominant formative shrub, and response to the low-energy wind environment. A nebkha's height and horizontal length increase synchronously in the early stage of the development, while the increase in horizontal length and projected area accelerates when the dunes become larger. Feedbacks involving both aeolian sand transport and shrub growth can explain a decline in growth rate with increasing height and an apparent height limit of about 4 m. This study also implies that nebkhas are important biogeomorphological features demonstrating how biotic and abiotic interactions can shape landforms and influence ecological functioning in arid and semi-arid environments.

Dust cycle is actively involved in the Earth’s climate and environmental systems. However, the spatiotemporal pattern and recent trend of dust emission from the drylands in East Asia remain unclear. By calculating dust aerosol optical depth (DOD) from the newly released moderate resolution imaging spectrometer aerosol products, we obtain a relatively long satellite-based time series of dust activity from 2001 to 2020 over China and Mongolia. We identify pronounced interannual variability of dust activity that is consistent with ground-based meteorological observations in the study area. A substantial reduction in spring dust activity in northern China is also found, which seems in accordance with the long-term weakening trend since the 1970s that has been attributed to the wind speed decline by previous studies. However, the spatial pattern of the trends in both annual mean and seasonal dust activity during the last 20 years is divergent, and the most significant dust diminishing is found over north-central China where large-scale vegetation restoration projects have been implemented. It indicates that in addition to the potential contribution of wind speed change, land-use change also plays an important role in the recent inhibition of dust emission. The current results show that dust activity occurs most intensively in spring, followed by summer and relatively weaker in autumn and winter. However, dust activity in autumn and winter has increased significantly in NW China despite the overall decreasing trend in other two seasons, probably associated with different seasonal atmospheric and land surface conditions. Finally, the DOD distribution reveals that the Tarim Basin, Gobi and Qaidam Basin Deserts are three major dust sources in East Asia. Compared to ground observations which are spatially limited and distributed unevenly, remote sensing provides an important complement, and it can serve as reference for identification of dust sources using other methods such as geochemical fingerprint and modeling.

Loess deposits along the northern fringe of the European loess belt potentially record past changes in dust emission from areas proximal to former ice sheets. Recent chronologies from loess deposits across this region generally agree on greatly enhanced dust deposition rates when the Fennoscandian Ice Sheet reached its maximum extent during the late last glacial. However, uncertainties over the material's source and origin limit understanding of the causes of this enhanced dust activity. In particular, loess in southwestern Poland has been attributed to multiple origins, mainly involving glaciofluvial outwash plains along the Fennoscandian Ice Sheet margin and/or local sources in the mountainous areas of the Sudetes and Western Carpathians. Here we apply detrital zircon U–Pb age analyses for a large number of grains recovered from four loess samples taken from different stratigraphic units exposed at Bialy Kościol in southwestern Poland, previously luminescence dated to MIS 4–2, to assess loess provenance as well as its temporal evolution during last glacial Fennoscandian Ice Sheet fluctuations. Furthermore, we analysed the detrital zircon U–Pb age spectra of five samples from potential source sediments to constrain the history of sediment recycling and mixing within the Northern European Plain prior to deflation and loess deposition. The broad range of zircon age components detected in the four loess samples suggests both Fennoscandian and closer Peri-Gondwanan proto-sources while a narrow, dominant Carboniferous age peak is consistent with sourcing from the local Strzelin Hills in the Sudetic foreland. However, the presence of both Fennoscandian and Peri-Gondwanan derived grains in samples from potential source sediments reveals that this mixture of sediment sources is widespread across the Northern European Plain, as a result of long-term glacial and fluvial reworking of cover sediments in the proglacial area throughout the Quaternary. Local rivers draining the Sudetic foreland transported this Fennoscandian-Peri-Gondwanan sediment mixture along with particles denuded from the Strzelin Hills, resulting in a nearby, temporally stable dust source for the Bialy Kościol loess during MIS 4–2, while dust emission rates were substantially increased during the last glacial maximum. Given that our model for loess formation at Bialy Kościol essentially involves sediment distribution via rivers prior to short distance aeolian transport, we infer that the proportion of northern ice sheet derived particles in European loess deposits is mainly controlled by the drainage pattern of major rivers in relation to Pleistocene ice margins where glaciofluvial sediment is abundant. Based on the presence of Fennoscandian derived zircon grains in European loess deposits, we constrain a southern limit of the influence of northern ice sheet dust sources along the central European highlands that currently divide drainage between the Northern European Plain and the Danube Basins.

The proportions of woody and grassland taxa in terrestrial ecosystems played an important role in the origin and evolution of early Palaeolithic hominins. However the influence of ecosystem changes on hominin behavior and adaptations in Asia has not been studied in detail. Hominins have exploited the Luonan Basin in the Eastern Qinling Mountains, central China, since the early Paleolithic. Dated sites, consisting of alternating loess and soil deposits with in situ artefacts, are common in the region, and provide a detailed record of Early to Middle Pleistocene hominin environments. Here, we present the results of measurements of the stable carbon isotopic composition of soil organic matter (δ13CSOM) in the loess-paleosol sequences from the Longyadong Cave site. Our analyses of δ13CSOM show that for at least 400 ka the Longyadong Cave site and its surroundings were dominated by C3 woody plants, whereas the nearby Liuwan site was dominated by C4 and C3 mixed grassland or woody grassland vegetation. These findings demonstrate that between 400 and 300 ka in the Luonan Basin, hominins occupied a habitat consisting of a mosaic of grassland and woodland/forest. Although the vegetation of the region changed in response to the glacial–interglacial climatic cycles, patches of woody vegetation in landscapes such as at Longyadong Cave site persisted continuously. Such environments seem to be have been favored by hominins living in the Luonan Basin, possibly because they provided a diverse range of food resources during both glacial and interglacial intervals of the Middle Pleistocene, when most of northern China was experiencing an increasing trend of drying and cooling and steppe environments were expanding. Thus, the Luonan Basin would have served as a refugium for hominin occupation in China during the Middle Pleistocene.

Our understanding of the long-term hydroclimate variations in South China is prohibited by the shortness of meteorological records. Paleoclimatic proxies, such as tree-rings, can be pursued to extend the meteorological records back for centuries to help us better understand hydroclimatic conditions. In this study, we reconstructed the July–August standardized precipitation–evapotranspiration index (SPEIJul–Aug) based on a newly developed 127-yr adjusted latewood width chronology from Tsuga longibracteata, South China. The chronology explained 40% of the actual SPEIJul–Aug variance in the period 1953–2014. The reconstructed SPEIJul–Aug can represent large-scale July–August SPEI variations over South China, including northern Guangxi, Hunan, and Guizhou provinces. From the perspective of the past 127 years, the extreme summer drought in 2013 was not unusual because more extreme drought events occurred in the first half of the 20th century. A significant 2.0–3.6-yr hydroclimatic cycle existed in the reconstruction, which indicated that the SPEIJul–Aug might be driven by El Nino–Southern Oscillation (ENSO). We further checked the time-dependency of the relationship between SPEIJul–Aug and ENSO and found that it was unstable. Their relationship was weak before the 1950s, became significant from the 1950s to early 1990s, and then dropped to be weak again and even out of phase since the early 1990s, which may be attributable to the significant westward extension of the western Pacific subtropical high.

China is a traditional agriculture based country and one main region for crop production is southeastern China where temperature is a dominant climate variable affecting agriculture. Temperature and social disturbances both influence crop production, yet distinguishing their relative impacts is difficult due to a lack of reliable, high-resolution historical climatic records before the very recent period. Here we present the first tree-ring based warm-season temperature reconstruction for southeastern China, a core region of the East Asian monsoon, for the past 227 years. The reconstruction target was April-July mean temperature, and our model explained 60.6% of the observed temperature variance during 1953-2012. Spatial correlation analysis showed that the reconstruction is representative of April-July temperature change over most of eastern China. The reconstructed temperature series agrees well with China-scale (heavily weighted in eastern China) agricultural production index values quite well at decadal timescales. The impacts of social upheavals on food production, such as those in the period 1920-1949, were confirmed after climatic influences were excluded. Our study should help distinguish the influence of social disturbance and warm-season temperature on grain productivity in the core agricultural region of China during the past two centuries.

© 2019 The Authors The Pliocene-Pleistocene boundary marks a major change in global climate and East Asian monsoon dynamic. However, the role of the global atmospheric dust-cycle over this time is unclear; in particular the degree to which changes in the dust cycle influenced climate change, were driven by climate change, and how these processes interacted. Chinese loess records past dust-cycle history and the influences of aridification and monsoon circulation over the last 40 Ma. Previous work on the Chinese Loess Plateau argue over whether changes in dust source occur at the Pliocene-Pleistocene boundary, or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics. We present Sr, Nd and Hf isotope data from multiple sites and show that dust source largely remains unchanged across these boundaries. Shifts in geochemistry are due to changes in grain-size and weathering. While the transport pathway (river, deserts, direct aeolian) is unclear, these tracer isotopes show that dust was dominantly sourced from the Northern Tibetan Plateau, with some input from the local bedrock. This shows that a major established and constant dust source on the Tibetan Plateau has been active and unchanged since late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are a function of climate change in Tibetan Plateau source regions rather than effects from increased aridification over the Pliocene-Pleistocene boundary.

Interactions of fluvial and eolian processes are prominent in dryland environments and can significantly change Earth surface morphology. Here, we report on sediment records of eolian and fluvial interactions since the last glacial period, in the semiarid area of northwest China, at the limit of the Southeast Asian monsoon. Sediment sequences of last glacial and Holocene terraces of the Yellow River are composed of channel gravels, overlain by flood sands, eolian dunes, and flood loams. These sequences, dated by optically stimulated luminescence, record interlinks between fluvial and eolian processes and their response to climate change. Sedimentologic structures and grain-size analysis show flood loams, consisting of windblown sediment, deposited from floodwater suspended sediment. The gravel and sand were deposited during cold periods. During transitions from cold to warm phases, the river incised, and dunes were formed by deflation of channel and floodplain deposits (>70 and 21–16 ka). Dunes also formed at ~0.8 ka, probably after human intervention. After dune formation, flood loam covered dunes without erosion during peak discharges at the beginning of the subsequent warm period. The fluctuations of the Southeast Asian monsoon as a moisture-transporting agent have perhaps been the driving force for interactions between fluvial and eolian processes in this semiarid environment.

The Palaeolithic industry in the Bose Basin, Guangxi, South China is well known in the international scientific community for its handaxes dating to the early Middle Pleistocene. Seven terraces occur in the basin, terrace 4 being best known because handaxes and tektites were recovered. Previous studies have concluded that the single phase within this industry dates to ca. 803 ka. However, before 2013 no attempt was made to excavate to the basal gravels from the top of terrace 4. Therefore, the stratigraphy and the layers from which the stone artifacts derive in terrace 4 are not clear. In 2013–2014, we conducted an excavation of 200 m2 at Gaolingpo, one of the most important Palaeolithic sites in the Bose Basin. We excavated to the basal gravels from the top of this terrace. A section more than 7 m thick was exposed and clearly shows the Pleistocene and Holocene stratigraphic sequence. Furthermore, about 800 stone artifacts including choppers, picks, and scrapers, were documented from a sequence comprising several stratigraphic layers. Based on stratigraphy and the stone artifacts, we have established three stages of Palaeolithic cultural remains from Gaolingpo. The first is probably ca. 803 ka. The second is dated to 15 ka, and the third stage to approximately 10 ka.

Cultural studies of Neolithic China have focused on the social aspects and the human–environment interactions associated with those cultures. However, the uneven spatial distribution of Neolithic sites in Northeastern China has not yet been explored. This study traces the relationship between human settlement patterns and the agro-ecological environment during the Holocene Optimum, based on the spatial distribution of 4184 Neolithic sites, together with optically stimulated luminescence (OSL) dating and pollen analysis of five profiles and 22 plant flotation samples from 10 of the archaeological sites in the West Liao River Basin, the hub of Neolithic Cultures in Northeastern China. The overwhelming majority (∼96.7%) of the Neolithic sites are located south of 43o30′N latitude in the West Liao River Basin on the southern fringe of the Horqin Dunefield. The dunefield, which has been commonly hypothesized as vegetated during the Holocene Optimum, was a typical steppe at that time and not suitable for growing millet, the primary staple crop of Neolithic Cultures. Our results and other archaeological site records reveal that the 43°30′N latitude was a remarkable barrier for the dispersal of human settlements in Northeastern China during the Neolithic Age. The barrier was probably formed by the low frost tolerance of millet and the temperature gradient associated with the latitude, making large-scale agricultural production impossible in the regions north of this latitude at the time. Our findings provide evidence for the natural northern limit of Neolithic Cultures in Northeastern China during the Holocene Optimum.

Since 2010, we have found stone artifacts at the Houfang and Dishuiyan loess sections on the second terrace of the Hanjiang River and the Wolonggang thick natural loess section on the fifth terrace of the same river near the Xuetangliangzi site. We dated Dishuiyan and Houfang loess sections by optically stimulated luminescence (OSL) and thermally transferred OSL (TT-OSL) methods respectively. Dating results showed that the loess–paleosol deposited on the second Hanjiang River terrace as L1, S1, L2, and S2 in sequence. We dated the Wolonggang loess section by high-resolution paleomagnetostratigraphic analyses. The Jaramillo subchron was found at this section. Correlating with the central Loess Plateau, we recognized the continuous loess–paleosol sequence from L9 to L15. Investigations showed that loess was continuously deposited on the terraces of the Hanjiang River at Yunxian Basin since at least 1200 ka.

There has been a significant debate about the nature and causes of the Pleistocene evolution of the Nihewan Basin, North China. We studied the eastern Nihewan Basin sedimentary facies at two main sites, Hutouliang and Donggou. A combination of field observations and measurements of sediment grain-size distribution was used to reconstruct the sequence of sedimentary environments since the middle Pleistocene, and optically-stimulated luminescence measurements were used to date the sediments. Our results indicate that a shallow lake occupied the basin center along the Sanggan River, probably lasting until ~440 kyr ago before disappearing completely ~340 kyr ago. It was succeeded by a phase of fluvial-dominated sediment accumulation which ended ~30 kyr ago. We suggest that the formation of the gorge resulted from the relative uplift of the Niuxin Mountain along the Liulengshan fault ~140 kyr ago. However, since ~30 kyr ago the fault may have become inactive and the river downcutting near Shixia was no longer offset by the relative uplift, which caused a shift from deposition to denudation in the Nihewan Basin from then on. The disappearance of the paleolake ~340 kyr ago may have been the culmination of the ongoing process of basin infilling.

For more than a century, two families of ice age theories have been proposed: insolation based theories proposed by Adhemar, and atmospheric CO2 ones proposed by Tyndall. The major technique advance of deep-sea sediment drilling, as well as new interpretations of stable oxygen isotopic composition of the deep-sea fossil foraminifera, which is regarded as a proxy index of continental ice volume and sea water temperature, established the now well recognized glacial-interglacial variations in climate over the late Pliocene and Pleistocene, e.g. ~3 Ma. A landmark progress came from Hays et al. (1976) who unambiguously demonstrated that the change in insolation induced by the Earth’s axial tilt (obliquity), the wobble of this tilt (precession), and the degree of circularity of the Earth’s orbit around the sun (eccentricity) brings on ice ages (glaciations) every hundred thousand years or so during the Pleistocene. Many subsequent observations, from the deep-sea to continental records, confirmed the co-variation between insolation and the alternation of glacial ice age phases, and warmer interglacial phases, at least in terms of frequency domains. However, these findings cannot explain the so called ~100 ka conundrum, where the size of 100 ka insolation forcing is relatively small yet the apparent ice sheet response is large, as well as the bi-polar symmetry in climate changes at precessional frequency of ~23 ka, despite the fact that the precession cycle drives insolation changes in antiphase between the two hemispheres. As such, other factors may be considered in the driving of Northern Hemisphere Glaciation (NHG) global glacial-interglacial variations. Several hypotheses have been put forward, such as: (1) the gradual decreasing CO2 drove global cooling through to a threshold value where insolation changes may force the ice age cycles; (2) the effect of local insolation that modulated the East Antarctica Ice Sheet after the gradual CO2 decline that drove its growth to maximal extent; (3) the Southern Ocean “marine biological pump” changes forced by the ocean water stratification and current changes that modulated the atmospheric CO2 thus triggered ice ages; (4) the clearing of regolith under the North American ice sheets which modulate ice sheet thickness and extent changes which allow the ice sheets to grow further south and be influenced more by precessional cycles, as well as strengthened the fresh bedrock weathering and drawdown more atmospheric CO2; and (5) because ice mass balance depends on whether the temperature is above or below the freezing point, a physically more relevant parameter to measure insolation forcing should be the insolation integrated over a given threshold that allows for ice melting, and thus triggering the glaciations. Unfortunately, we cannot determine which one is right or several of them acting together so far. The most distinct features of the ice age climate are both the onset of the NHG at ~2.7 Ma and the transition of ~41 ka based glacial-interglacial cycles to cycles of a ~100 ka dominated frequency at ~1.0 Ma, namely the Early Middle Pleistocene Transition. We suggest that, both insolation and CO2 changes together forced the climate of the ice ages: the stepwise cooling that occurred at ~2.7 Ma and ~1.0 Ma may be linked with gradual atmospheric CO2 reduction, during which the atmospheric CO2 levels fell to a threshold value that triggered high-latitude (both poles) ice expansion. Under a new cooling state since ~2.7 Ma, the dominant climatic cycle at ~41 ka was forced by obliquity (orbital tilt), while the ~23 ka precession cycle was cancelled by opposing effects at both poles. On the other hand, we propose that the ~100 ka cycles that became dominant following approximately 1 Ma were forced by a CO2 based “marine biological pump” change in the Southern Ocean, or is related to stochastic behavior of the ice sheets. The ~400 ka eccentricity cycle, which is a stronger absolute influence on insolation is an outstanding rhythm in the late Cenozoic, yet is not as strong in climate records as the precessional and obliquity cycles during the late Pliocene and Pleistocene, and thus needs further examination. In summary, we suggest ice ages are caused by the integrated forcing of insolation, atmospheric CO2, ocean conveyer and ice sheet feedback etc., in which the insolation forcing is primary, a threshold value of the other facts was attained, the ice age happened. However, our hypothesis is very tentative, more investigation is still needed on what causes the ice ages.

Despite the proposed climate–human connection in the West Liao River Basin during the Bronze Age, the question of how climate change could have affected the subsistence strategies, and consequently, the cultural transformation from the Lower Xiajiadian to the Upper Xiajiadian periods, has never been systematically explored. Based on radiocarbon dating and the analysis of plant remains recovered by flotation, as well as the spatial distribution of archaeological sites, this study investigates the subsistence strategies of ancient people and their influence on cultural development in the West Liao River Basin during the Lower Xiajiadian (3900–3400 cal. yr BP) and Upper Xiajiadian periods (3000–2500 cal. yr BP). Carbonized seeds collected from 13 archaeological sites reveal that people engaged in millet-based agriculture in this area throughout the Bronze Age. Favorable climate during the Holocene Optimum promoted millet farming among the Lower Xiajiadian Culture. The end of the Holocene Optimum and its associated climate deterioration led to agricultural shrinkage in the Upper Xiajiadian period, which is revealed by the reduced amount of carbonized millet seeds and the ratio between foxtail millet and broomcorn millet. Climate deterioration led to diverse subsistence strategies, resulting in the dispersal of human settlements and the differentiation of the spatial distributions of different groups. People with millet-based subsistence strategies retreated southward, while people with animal husbandry and hunting-based subsistence strategies migrated westward. The above findings may offer insights in comprehending how climate deterioration could have affected the multi-facets of human societies in the West Liao River Basin, which is a climatically sensitive region, in Chinese prehistory.

In this study, late Holocene vegetation, climate and human impacts were investigated using multiproxy data-pollen percentages, pollen accumulation rates (PAR), humification and loss-on-ignition (LOI)—measured from peat sediments from Daiyun Mountain, southeast China. A stratigraphic chronology was established on the basis of four radiocarbon dates. The 4,350 year sequence of vegetation history and climate change exhibits three distinctive stages: (1) 4,350–1,000 cal bp, during which the vegetation was dominated by evergreen forests mainly composed of broad-leaf trees, indicating a warm and wet climate; (2) 1,000–550 cal bp, during which the climate was thought to be cool and dry, based on a decrease in pollen percentages and the PARs of trees, shrubs and wetland herbs, and an increase in the pollen percentage and PAR of dry land herbs, as well as high overall LOI values; and (3) 550 cal bp to modern times, during which higher pollen percentages of dry land and wetland herbs, along with low pollen percentage and PAR of trees and shrubs, as well as low absorbance and LOI values, suggest relatively cooler but wetter climate conditions. In addition, major climatic events, such as the warm period from ad 670–960, the Medieval Warm Period (ad 1050–1520) and the Little Ice Age (ad 1580–1850), could be identified within the peat sediments in this study, with climatic conditions at these times being characteristically warm and wet, warm and dry, and cold and wet, respectively. Pollen signals indicate significant human impact since 1,000 cal bp, which may be linked to the development of the local porcelain industry and a rapid increase in the population in the study region.

While saltation bombardment of sand grains on a fine substrate can produce considerable dust, the well-sorted nature of sand dunes tends to preclude them from consideration as major dust sources. Recent research, however, has revealed that sand dunes can, in some cases, be large sources of dust. We used the PI-SWERL (Portable In-Situ Wind Erosion Laboratory) to measure in the field the potential of sand dunes and other desert landforms to emit particulate matter

The Quaternary wind-blown Chinese loess-paleosol sequence, which developed as a product of the intensification of Northern Hemisphere glacial-interglacial cycles, is a major source of information on aridification of the Asian interior. In northeastern (NE) China, extensive loess deposits occur that have great potential for reconstructing the long-term paleoclimatic evolution of the region. Despite existing geochemical data indicate that the probable major source areas for these loess deposits were the nearby Horqin and Otindag deserts, it is still unclear that whether there was a long-term change in the detrital source of these loess deposits. In addition, the aridity history and long-term desert evolution of NE China are currently poorly understood. In the present study, we measured the silicate Nd and Sr isotopic composition of the 28–45 μm grain-size fraction from multiple loess sections (NYZG, SBH, and TDJZ). The results show that the loess deposits of the three sites were dominantly sourced from the Otindag sandy desert and that this source remained constant for the past 1.2 Ma. Notably, the 87Sr/86Sr ratios are influenced mainly by variations in the content of clay-sized material present in the form of aggregates or adhering to the surface of coarser particles. Therefore, caution is needed in the use of 87Sr/86Sr ratios of the 28–45 μm fraction as a tracer of eolian dust, when the clay minerals are not completely removed during the pretreatment process. The grain-size variability of the three sections indicates that stepwise enhancement of aridification in the Otindag sandy desert occurred at 1.2 Ma, 0.9 Ma, and 0.7 Ma, which coincided respectively with the beginning of the Mid-Pleistocene transition (MPT), an extremely cold event at ~0.9 Ma within the MPT, and the establishment of a full glacial climate at the termination of the MPT. This finding supports the hypothesis that the growth of high-latitude ice sheets was the major driver of the long-term aridification of Asian dust source areas.

Geological records of climate change since the last glaciation in South China, a core area of the East Asian monsoon, are key to understanding secular variation in the monsoon system. However, with the exception of the speleothems, records from this area with independent age control are few. We investigated aeolian sand deposition on a sand hill on the shore of Poyang Lake in South China and reconstructed the chronological sequence of aeolian deposition using Optically Stimulated Luminescence (OSL) dating. Without exception, all aeolian sediments were deposited within seven periods that generally match the timing of Heinrich events and other cold periods in Greenland. We argue that aeolian sand accumulation in this region is most likely forced by extreme aridity driven by weakening of the summer monsoon, while the characteristics of this deposition are influenced by winter monsoon intensity. The monsoon shifts revealed here suggest a possible link between North Atlantic cooling and summer monsoon strength in South China, and support the intensities of cooling phases recorded in Greenland ice cores.

The Chinese Loess Plateau in north central China contains one of the most valuable Cenozoic climate archives on land. Establishing the origin of this substantial archive of aeolian sediments is critical for the interpretation of loess climate proxies, past atmospheric wind patterns and changing climatic/tectonic controls on erosion over potentially the past 25. Ma. Despite this significance there are a number of disagreements over the precise source areas and the extent to which these vary through time and across the plateau. To address this, we utilize a multi-technique, approach of combined detrital single-grain zircon U-Pb dating and heavy mineral analysis to establish the sources of loess through the Quaternary and constrain their variation geographically across the Loess Plateau. We combine our data with suitable published single-grain datasets from loess and possible source regions. The results demonstrate a dramatic spatial heterogeneity of dust sources across the plateau. Sites to the west of the Loess Plateau show strong affinity to the Yellow River and the northern Tibetan Plateau, while further east the influence of North-China-Craton-derived material becomes more significant (Fig. 1). This spatial variability in source implies a far more complex relationship to dust sources than previously envisioned. The provenance of loess/soil units also varies through time, although there is no consistent relationship between these shifts and changing glacial/interglacial periods, as hypothesized previously. This variation demonstrates highly dynamic and variable dust sources and transport modes that are influenced by abrupt climate shifts within individual glacial-interglacial episodes, and potentially the dynamics of the Yellow River system.

The chronology of dust deposition and climate during the last interglacial is poorly known on the Chinese Loess Plateau. Here, 51 samples were taken from the ∼5 m S1 palaeosol (MIS5) at the desert marginal Jingbian site to develop what is currently the most detailed S1 chronology on the Plateau using instrumental dating techniques. We use the post-IR IRSL signal from sand-sized grains of K-rich feldspar. Signal resetting in the agricultural layer shows that it is possible to almost completely zero this signal in nature. First IR stimulation plateau measurements show that there is no clear dependence of D e on first IR stimulation temperature between 50 and 260 °C suggesting negligible signal fading. Resultant ages are consistent with a last interglacial age (∼130 to ∼75 ka) and are also consistent within errors with continuous linear sedimentation rates. The average mass accumulation rate for S1 is ∼150 g m −2 a −1 , considerably higher than at many other sites but within the overall range of Loess Plateau estimates. The remarkably stable sediment accumulation at the site contrasts with a more complex record of environmental and monsoonal change recorded in grain-size and magnetic susceptibility.

Hf-Nd-Sr isotopic fingerprinting has been employed as a powerful method for distinguishing dust sources. However, the Hf and Sr isotopic compositions of dust are highly dependent on particle size to accurately identify dust provenance. Here we compare the Hf-Nd-Sr isotopic compositions of clay-sized fractions from dust sources (the Mongolian Plateau) to sinks (Beijing and Greenland). Our results document that clay-sized Hf-Nd-Sr isotopic compositions of Mongolian dust are controlled by two isotopic/geochemical provinces: Southern Mongolian Gobi (SMG) and Northern Mongolian Plateau (NMP). Our data indicate that the SMG is potentially an important dust source to the loess in Beijing and Hulun Buir and could be a contributing source of dust to Greenland, whereas the NMP contributes little dust to the Chinese loess and the Greenland. Furthermore, we demonstrate that the deserts of northwest China are one of the main dust contributors to Beijing and Greenland, but not to Hulun Buir.

The substantial tectonic uplift (1000–2500 m in a few million years) of the Northeastern Tibetan Plateau (NETP), together with the major climatic changes during the Quaternary, provides an opportunity to study the impact of tectonic and climatic changes on the morphological development and sedimentary architecture of fluvial deposits. The effects of these processes are revealed by a terrace staircase, together with the stratigraphy of each individual terrace, in the confluence zone of the Huang Shui and Yellow Rivers in the NETP, during the late Quaternary. On the basis of morphological mapping and OSL-dating, at least seven strath terraces were identified that formed during the last glacial cycle, which are preserved at locations where tectonic uplift was sufficient to separate them altitudinally from one another. The terraces are composed of stacked fluvial gravels, sands and alluvial loams. The principal result is that we demonstrate that the terraces were formed in response to climatic cycles on a suborbital timescale. For each terrace, the lower coarse-grained sediments (gravel and sand) were deposited during cold periods (such as the LGM, MIS3b, MIS4 and MIS5d) associated with a strong Asian winter monsoon. The aggradation during cold periods was associated with floodplain widening. The river incised slightly during the transitions from cold to warm phases, resulting in the transformation of the previous river plain into a terrace. The coarse grained cold phase deposits are covered by inter-bedded, horizontally-laminated silt and sand (representing flood sediments that often contain reworked soil material), during the (cold to warm) transitional phases. The floodplain accumulation on the terrace continued during the subsequent warm period. The warm periods (such as MIS3a, MIS3c, and MIS5a) of the climatic cycles are associated with a strong Asian summer monsoon. Pronounced incision took place at the subsequent warm–cold transitions. After this warm–cold transition, aeolian loess accumulated on the abandoned terrace without any further fluvial reworking. Our results demonstrate that critical thresholds for fluvial response can be crossed at climatic changes on a suborbital timescale given conditions of accelerated tectonic uplift in the NETP. In addition, based on the OSL ages of different units in the sedimentary sequences of the terraces, we conclude that the durations of terrace aggradations and floodplain widening lasted much longer than the periods of fluvial downcutting.

The sources of modern dust aerosols and their emission magnitudes are fundamental for linking dust with climate and environment. Using field sample data, wind tunnel experiments and statistical analysis, we determined the contributions of wadis, gobi (stony desert), lakebeds, riverbeds, and interdunes to modern dust aerosol availability in the three important potential dust sources including the Tarim Basin, Qaidam Basin, and Ala Shan Plateau of China. The results show that riverbeds are the dominant landscape for modern dust aerosol availabilities in the Qaidam Basin, while wadis, gobi, and interdunes are the main landscapes over the Ala Shan Plateau and Tarim Basin. The Ala Shan Plateau and Tarim Basin are potential dust sources in northwestern China, while the Qaidam Basin is not a major source of the modern dust aerosols nowadays, and it is not acting in a significant way to the Loess Plateau presently. Moreover, most of modern dust aerosol emissions from China originated from aeolian processes with low intensities rather than from major dust events.

There are 56 officially-recognized ethnic groups in China. However, the distinct geographic patterns of various ethnic groups in relation to the physical environment in China have rarely been investigated. Based on the geo-referenced physical environmental parameters of 455 Han, Tu, Hui, Salar, Mongolian, and Tibetan communities in Qinghai, we found that the communities could be statistically demarcated by temperature and aridity threshold according to their ethnicity, implying that the geographic distribution of each ethnic group is mediated by the physical environment. We also observed that the habitat of each ethnic group is ecologically compatible with current subsistence strategies. Tibetans settle in cold and humid high-altitude regions owing to the cultivation of highland barley and the breeding of yak, dzo, Tibetan sheep and Tibetan goat. Mongolians survive by animal husbandry in cold and dry grassland areas. Han and Tu people settle in the Huangshui River Valley, which offers relatively humid climate and flat land for agriculture. Hui and Salar people occupy the Yellow River Valley with its relatively arid environment and grassland vegetation suitable for animal breeding. Our findings offer a new perspective in explaining the geographic patterns and the varieties of ethnic groups in China and elsewhere.

National Natural Science Foundation of China [41202127, 41072122]; Priority Academic Program Development of Jiangsu Higher Education Institutions; Fundamental Research Funds for the Central Universities [1082020904]; CAS [XDA05130201]; Chinese Academy of Sciences [KZCX2-YW-BR-24]