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As the only natural satellite of the earth, the Moon has always been the first choice for human exploration of the solar system. China's lunar exploration project (Chang'e project) was launched in 2004. At present, it has created a perfect end to the three phases of "orbiting, landing and returning". A series of remarkable research achievements have been made on the basic issues of current lunar scientific research, such as the Earth-Moon space environment, lunar surface material, morphology, geological structure, lunar subsurface and internal structure, and the origin and evolution of the Moon, further deepening the human understanding of the Moon. This paper briefly reviews the development process of China's lunar exploration project, summarizes the main research results and scientific understanding, and finally prospects to the future development of China's lunar and planetary exploration. [ABSTRACT FROM AUTHOR]

The latest Coupled Model Intercomparison Project Phase 6 (CMIP6) proposes new shared pathways (SSPs) that incorporate socioeconomic development with more comprehensive and scientific experimental designs; however, few studies have been performed on the projection of future multibasin hydrological changes in China based on CMIP6 models. In this paper, we use the Equidistant Cumulative Distribution Function method (EDCDFm) to perform downscaling and bias correction in daily precipitation, daily maximum temperature, and daily minimum temperature for six CMIP6 models based on the historical gridded data from the high-resolution China Meteorological Forcing Dataset (CMFD). We use the bias-corrected precipitation, temperature, and daily mean wind speed to drive the variable infiltration capacity (VIC) hydrological model, and study the changes in multiyear average annual precipitation, annual evapotranspiration and total annual runoff depth relative to the historical baseline period (1985–2014) for the Chinese mainland, basins and grid scales in the 21st century future under the SSP2-4.5 and SSP5-8.5 scenarios. The study shows that the VIC model accurately simulates runoff in major Chinese basins; the model data accuracy improves substantially after downscaling bias correction; and the future multimodel-mean multiyear average annual precipitation, annual evapotranspiration, and total annual runoff depth for the Chinese mainland and each basin increase relative to the historical period in near future (2020–2049) and far future (2070–2099) under the SSP2-4.5 and SSP5-8.5 scenarios. The new CMIP6-based results of this paper can provide a strong reference for extreme event prevention, water resource utilization and management in China in the 21st century. [ABSTRACT FROM AUTHOR]

To achieve carbon peak targets, realize carbon neutrality vision, and tackle global climate change, China must improve the carbon emission performance at the city level. Based on the carbon emission performance of 191 prefecture-level cities in China from 1997 to 2017, this paper analyses the evolution characteristics of urban carbon emission performance from three aspects: the overall spatial and temporal evolution, the differences according to both region and city size, and the differences among clusters categorized by carbon emission performance at the city level. This paper also reveals the impact of the social and economic transition on China's carbon emission performance. The results show that: (1) The overall level of carbon emission performance of Chinese cities is low, and there is a downward trend during the study period. The differences in carbon emission performance among cities are convergent, but there is a wide gap between high and low values. (2) The carbon emission performance of cities in eastern coastal areas is higher than that in non-coastal areas cities. Large urban agglomerations and economically developed regions, such as provincial capitals, are the agglomeration areas of high urban carbon emission performance values. (3) The carbon emission performance level of cities with similar sizes will converge. At the same time, such changes will enhance the differences among carbon emission performances at the city level within the same region. (4) Cities that belong to high urban carbon emission performance clusters are mainly distributed in the eastern region. Such cities are classified into large cities, supercities, and megacities. Compared with low urban carbon emission performance clusters, cities in high urban carbon emission performance clusters show a higher proportion in the medium-high level and high level of carbon emission performance. Moreover, cities in high urban carbon emission performance clusters are more likely to improve theirurban carbon emission performance. (5) The economic agglomeration effect, industrial structure adjustment and carbon intensity reduction have a significant impact on improving urban carbon emission performance. Population agglomeration has an incremental effect, and the anticipated benefits of environmental regulation have yet to be fully realized. The impacts of different clusters and different regions are variable. Finally, this paper advances policy enlightenment according to its research findings. [ABSTRACT FROM AUTHOR]

Based on the global reanalysis data of the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research, the surface meteorological observation data, sounding data and satellite observation data, this paper comprehensively analyzes the evolution process and formation mechanism of a persistent severe dense fog process occurred on February 15–17, 2015 in Yancheng, eastern China. Through the numerical simulation experiment of Weather Research and Forecast (WRF) model, we further analyze the impact of sea-land breeze on the formation and burst reinforcement of fog. Results show that the precipitation caused by the southwesterly airflow in front of the upper-level trough and the low-pressure inverted trough are conducive to the formation of early rain fog, while the nighttime clear radiance under the control of surface cold high and the infiltration of weak cold advection are conducive to the formation and development of later radiation-advection fog. The WRF model simulates the fog evolution process, which is basically consistent with the actual fog area, and the simulation results are credible to a certain extent. The simulation results show that the establishment of sea breeze has an advection cooling effect on the near surface layer, which is conducive to the formation and development of the inversion layer on the near surface, providing stable stratification conditions for the formation and burst reinforcement of fog. On one hand, the strengthening of sea breeze circulation can continuously transport water vapor to the study area. On the other, the occurrence of ultra-low level jet is favorable for the accumulation of low-level water vapor. At the same time, the inversion intensity further strengthens, which is in favor of the burst reinforcement and long-term maintenance of fog. [ABSTRACT FROM AUTHOR]

The Banquan Basin is a pull-apart basin with the largest scale and the most prominent structure due to dextral slip of the Tanlu Fault Zone (TLFZ) in late Cenozoic. The depositional history of the basin records the start time and evolution of the right-lateral strike-slip movement of the TLFZ. This paper studies the sedimentary and tectonic evolution of the Banquan Basin by seismic reflection exploration, borehole detection and cosmogenic nuclide chronology. We analyze the coupling relationship between the pull-apart basin and the strike-slip fault and discuss the start time and tectonic significance of the right-lateral strike-slip of the TLFZ. Our study indicates that the Banquan Basin has undergone three evolutionary stages: weak rifting during the pre-pull-apart period, strong extension during the syn-pull-apart period and subsidence during the post-pull-apart period. This implies that the TLFZ, which controls the evolution of the basin, experienced an evolutionary process of weak activity, intensified activity and migration of activity toward the central basin. The sedimentary filling of the basin has strong response to the episodic pull-apart and extension of the basin. Lying upon the basement of the basin, a thin layer of Miocene mudstone slowly accumulated due to local rifting before the strong pull-apart event. Along with the dextral slipping and pull-apart process, the basin was filled with alluvial fan facies, fluvial facies and floodplain facies strata from bottom to top. The latest tectonic movement of the TLFZ in the North China Block in late Cenozoic was dominated by episodic dextral strike-slip motion, and this deformation pattern started at 4.01±1.27 Ma. The latest tectonic deformation in North China since late Cenozoic was governed by eastward extrusion and tectonic orogenesis of the eastern margin of the Qinghai-Xizang Plateau since late Miocene. The eastward thrusting of the Liupanshan fault zone and sinistral shearing of the Qinling fault zone led to the anticlockwise rotation and pushing of secondary blocks in North China, resulting in a planar bookshelf faulting and rotation pattern. This unique deformation pattern transferred eastwards to the North China Plain at ∼ Ma and the process continues to the present time. This planar bookshelf rotation, accompanied with regional sinistral strike-slip movement of the ∼EW-trending boundary fault zones to the north and south of the North China Block and dextral strike-slip motion of the NNE-trending boundary faults between secondary blocks, is likely to be the long-range effect of the strong extrusion of the eastern margin of the Qinghai-Xizang Plateau. [ABSTRACT FROM AUTHOR]

China has planned and built several world-class cascade high dams in Jinsha River, Dadu River, Lancang River, and Yarlung Zangbo River. The complex geological conditions in the reservoir area and numerous large-scale landslide bodies make the potential disaster risk of overflowing and cascade dam failure caused by landslide-generated tsunami under increasing severe situations. However, the study on describing and predicting the complex dynamic processes of generation, propagation, overflowing, wave setup, and the interaction between tsunami and lakeshore has not been systematically carried out. Based on the high-order Boussinesq-type equations, the development of the dynamic system of tsunamis in lakes coupled with the landslide process is realized using the finite volume method in this paper. To verify the accuracy and reliability of the study, the Xiluodu Reservoir is selected as the object to simulate the potential landslide-generated tsunamis. The factors such as the generation and propagation of tsunamis, dam overflowing, and wave setup in the downstream river are quantitatively evaluated and analyzed. The constructed landslide with a total volume of 24×106 m3 generates a near-field wave amplitude of about 28 m. The maximum wave run-up height is about 95 m, the volume of the dam overflowing water up to 2.13×106 m3, and the maximum wave height above the dam crest presents an M-shaped distribution. This LGWs event raises the downstream water level by nearly 40 m. The results show that the risk of landslide-generated tsunamis in the reservoir area in China cannot be ignored. The developed Boussinesq-type equations coupled with the landslide dynamics can simulate the whole process of generation, propagation, runup, and estimating the overflowing water volume of the tsunamis in the lake, laying a foundation for the quantitative risk assessment of tsunamis in lakes of high cascade dams in China. [ABSTRACT FROM AUTHOR]

Located on the southeast coast of China, Fujian is an important junction for the spread and migration of agriculture and populations from mainland Asia to Taiwan and the Island Southeast Asia. Research on the emergence of agriculture and its relationship with the regional environmental context is key to understanding the evolution of ancient human-land interactions in the coastal zone of China. This paper presents a detailed microfossil analysis of the Dapingding site, which is located in the lower reaches of the Min River on the southeast coast of China. We found a large number of phytoliths produced in rice stems and leaves from the cultural layers of this site, dated to 7,500 cal. a BP. In addition, we found rice husk impressions and rice phytoliths in the pottery sherds of these cultural layers. Among these phytoliths, rice bulliform phytoliths with ≥9 fish-scale patterns indicating the degree of rice domestication, accounted for 44%. This percentage is much higher than the established standard for wild rice bulliform phytoliths with fish-scale patterns, suggesting that rice cultivation had already occurred on the southeast coast of China approximately 7,500 years ago. Subsequently, the starting time of agricultural activity on the southeast coast of China was pushed from 5,000 to 7,500 years ago. Comparing the regional history of sea level and coastline changes in the early to mid-Holocene, we suggest that the emergence of early rice cultivation in Southeast China was associated with high sea levels in the mid-Holocene and the last transgression in the Fuzhou Basin. The 'Fuzhou Bay', formed by the retreating coastline and transgression driven by high sea levels, may have provided a sea channel for the southward movement of northern rice farmers. [ABSTRACT FROM AUTHOR]

Concurrent compound dry and hot events (CDHEs) amplified more damange on the ecosystems and human society than individual extremes. Under climate change, compound dry and hot events become more frequent on a global scale. This paper proposes a mathematical method to quantitatively attribute changes of CDHEs to changes of precipitation, change in temperature and change in the dependence between precipitation and temperature. The attribution is achieved by formulating the total differential equation of the return period of CDHEs among Meta-gaussian model. A case study of China is devised based on monthly precipitation and temperature data during the period from 1921 to 2020 for 80 major river basins. It is found that temperature is the main driving factor of increases in CDHEs for 49 major river basins in China, except for the upper and middle reaches of the Yangtze River. In West China, precipitation changes drove the increase in CDHEs in 18 river basins (23%), particularly in parts of North Xinjiang, Qinghai and Gansu. On the other hand, dependence between precipitation and temperature dominated changes of CDHEs in 13 river basins (16%) of China with other factors, including parts of South China, East China and Northwestern China. Furthermore, changes in both the mean and spread of precipitation and temperature can also contribute to changes in CDHEs. [ABSTRACT FROM AUTHOR]

There are many types of atmospheric heat engines in land-air systems. The accurate definition, calculation and interpretation of the efficiency of atmospheric heat engines are key to understanding energy transfer and transformation of land-air systems. The atmosphere over the Qinghai-Tibet Plateau (QTP) in summer can be regarded as a positive heat engine. The study of the heat engine efficiency is helpful to better understand land-air interaction and thermal-dynamic processes on the QTP. It also provides a new perspective to explain the impact of the QTP on the climate of China, East Asia and even the world. In this paper, we used MOD08 and ERA5 reanalysis data to calculate the atmospheric heat engine efficiency, surface heat source and atmospheric heat source on the QTP in summer (May to September) from 2000 to 2020. The average atmospheric heat engine efficiency on the QTP in summer from 2000 to 2020 varies between 1.2% and 1.5%, which is less than 1.6%; the heat engine efficiency in summer is higher than that in June, July and August; the Qaidam Basin is the region with the highest atmospheric heat engine efficiency, followed by the western QTP. The mean surface heat source on the QTP in summer from 2000 to 2020 is 96.0 W m−2, the atmospheric heat source is 90.7 W m−2, and the release of precipitation condensation latent heat is the most important component of the atmospheric heat source on the QTP in summer. There is a strong and significant positive correlation between the atmospheric heat engine efficiency and the surface heat source on the QTP in summer. The precipitation con densation latent heat is the most important component of the atmospheric heat source in summer and can reflect the precipitation process. There is a strong and significant negative correlation between the atmospheric heat engine efficiency and the atmo spheric heat source on the QTP in summer. [ABSTRACT FROM AUTHOR]

Helium gas is a scarce but important strategic resource, which is usually associated with natural gas. Presently, only one extra-large helium-rich gas field has been found in China: the Hetianhe Gas Field in the Tarim Basin. This paper reports a new example, the Dongsheng Gas Field (DGF) in the Ordos Basin. In this study, 92 natural gas samples from the DGF were analyzed for helium content and isotope composition using isotope mass spectrometry. The natural gas samples were found to have an average helium content of 0.133%, with 65 (70.7%) of the samples having a helium content of 0.1% or more. Based on the proven natural gas reserves of the DGF, the proven geological helium reserves were calculated to be 1.96×108 m3, suggesting that it represents the first extra-large helium-rich natural gas reservoir to be hosted in tight sandstone in China. The 3He/4He ratios of 5 natural gas samples from the DGF are within the range of 3.03×10−8−3.44×10−8. Therefore, the helium in the gas field is thought to be of typical crustal origin and to have formed in the granitic basement that is rich in uranium and thorium. The accumulation of helium-rich natural gas was controlled by regional tectonic activities. Activity along the fault connecting the reservoir with the basement caused release of the helium gas, which entered the overlying strata along the fault and accumulated with conventional hydrocarbon gas. Based on the structural background and the distribution of helium source rocks in the Ordos Basin, the main helium source rocks with high exploration potential are located in deep strata within the north and middle parts of the basin. [ABSTRACT FROM AUTHOR]

Regional processes on land-water-air interface carbon (C) budget and balance that interconnect the land and sea are in fact C neutrality critical processes within the earth system. It is therefore essential to quantitatively analyze synergistic land-water-air interface C transport and C exchange processes to gain a deep understanding of the important role that terrestrial ecosystems play in "missing C sink". This paper systematically analyzes global land-water-air interface C migration processes as well as C budget changes and associated impact mechanisms. It also investigates the important role that these C budgets and C cycling processes play in inland water bodies, respective to C budgets at the land-water-air interface. Moreover, this study reveals the regulatory mechanisms of land-water-air interface C budgets and balances under a background of global climate change. It also quantitatively evaluates the status of China's regional land-sea-air interface C budgets as well as the C sequestration potential of its lake systems. Finally, this study concludes that the explicit quantification of anthropogenic activity impacts on land-water-air interface C transport and exchange processes is of great significance to global C balances and C neutrality. [ABSTRACT FROM AUTHOR]

The Middle Miocene Climate Transition (MMCT, ∼14 Ma) is the largest cooling event in the Cenozoic "Coolhouse", which significantly impacts the global chemical weathering pattern. In this paper, the responses of the MMCT global cooling event in the deep South China Sea were studied by clay mineral assemblages analysis of the oceanic red beds (ORB) at International Ocean Discovery Program (IODP) Expedition 368 Site U1502. The results show that the clay mineral assemblages of the ORB at Site U1502 are mainly composed of smectite (56–88%), illite (7–29%), and kaolinite (6–20%), without chlorite. The contents of these clay minerals and illite crystallinity show a four-stage variation pattern during early-middle Miocene (22.8−10.8 Ma). Smectite decreased from average 81% during 22.8–16.2 Ma and 16.2–14.4 Ma to average 67% during 13.8–10.8 Ma, with a rapid decrease of ∼14% during 14.4–13.8 Ma. On the contrary, illite and kaolinite increased rapidly by ∼8% and ∼6%, respectively, during 14.4–13.8 Ma. Illite crystallinity increased from average 0.18°Δ2θ during 22.8–16.2 Ma to average 0.19°Δ2θ during 16.2–14.4 Ma, and then decreased rapidly by ∼0.02°Δ2θ during 14.4–13.8 Ma. The provenance analysis of clay minerals shows that illite and kaolinite mainly originated from South China landmass due to physical erosion, while smectite mainly came from the Luzon arc as the product of chemical weathering. Therefore, smectite/illite ratio and illite crystallinity are used as proxies of chemical weathering intensity in the early-middle Miocene. High values of the ratio and the crystallinity represent the enhanced chemical weathering, whereas low values indicate the weakened chemical weathering or the strengthened physical erosion process. The smectite/illite ratio and illite crystallinity both decreased rapidly during 14.4–13.8 Ma, indicating the chemical weathering in the surrounding area of the South China Sea weakened rapidly, which we believe is the result of the MMCT event forcing. In addition, their values increased slightly during 16.2–14.4 Ma, which is in response to the relatively enhanced chemical weathering during the Middle Miocene Climate Optimum (MMCO). The variation pattern of clay mineral assemblages of the early-middle Miocene ORB in the South China Sea and its rapid transformation during the MMCT reveal that the Cenozoic cooling played a specific role in controlling the chemical weathering of the Earth's surface. [ABSTRACT FROM AUTHOR]

Sulphate (SO42−) is a main component of PM2.5 in China. The chemical formation mechanisms of sulphate are complex, and many air quality models have been used to analyse these mechanisms. To improve the accuracy of Weather Research Forecast-Chemistry (WRF-Chem) on sulphate, an alternative method is proposed in this paper. Moreover, data assimilation is performed to adjust the chemical reaction rates of sulphate. Based on the original reactions, a new sulphate parameterisation scheme, which includes two hypothetical reactions and six undetermined parameters, was added. Based on the WRF-Chem/DART (Data Assistance Research Testbed) system, the near-ground concentrations of SO42−, SO2, NO2, O3 and particulate matter are assimilated to adjust the six parameters. After adjusting the parameters, the new scheme can effectively solve the underestimation of SO42− and overestimation of SO2. The simulation of SO42− improved as the mean bias changed from −13.1 µg m−3 to 3.5 µg m−3 while SO2 improved from 17.0 µg m−3 to 6.3 µg m−3. The temporal and spatial variation characteristics predicted by the new scheme are consistent with the theoretical research results, indicating that the complex mechanism of sulphate formation could be replaced by the temporal and spatial variation characteristics predicted by the new scheme and that the parameters can be adjusted by data assimilation. Furthermore, the reaction rates of the SO42− parameterisation scheme of the WRF-Chem model are improved in this study, and a new method for improving the accuracy of the air quality model is provided. [ABSTRACT FROM AUTHOR]

The Sichuan-Yunnan area is located at the southeastern margin of the Tibetan Plateau, where tectonic movement is strong with deep and large faults distributed in a staggered manner, which results in strong seismic activities and severe earthquake hazards. Since the 21st century, several earthquakes of magnitude 7.0 or above occurred in this region, which have caused huge casualties and economic losses, especially the 2008 Ms8.0 Wenchuan earthquake. At present, earthquake monitoring and source parameter inversion, strong earthquake hazard analysis and disaster assessment are still the focus of seismological researches in the Sichuan-Yunnan region. Regional high-precision 3D community velocity models are fundamental for these studies. In this paper, by assembling seismic observations at permanent seismic stations and several temporary dense seismic arrays in this region, we obtained about 7.06 million body wave travel time data (including absolute and differential travel times) using a newly developed artificial intelligence body wave arrival time picking method and about 100,000 Rayleigh wave phase velocity dispersion data in the period range of 5–50 s from ambient noise cross-correlation technique. Based on this abundant dataset, we obtained the three-dimensional high resolution Vp and Vs model in the crust and uppermost mantle of southwest (SW) China by adopting the joint body and surface wave travel time tomography method considering the topography effect starting from the first version of community velocity model in SW China (SWChinaCVM-1.0). Compared to SWChinaCVM-1.0, this newly determined velocity model has higher resolution and better data fitness. It is accepted by the China Seismic Experimental Site as the second version of the community velocity model in SW China (SWChinaCVM-2.0). The new model shows strong lateral heterogeneities in the shallow crust. Two disconnected low velocity zones are observed in the middle to lower crust, which is located in the Songpan-Ganzi block and the northern Chuandian block to the west of the Longmenshan-Lijiang-Xiaojinhe fault, and beneath the Xiaojiang fault zone, respectively. The inner zone of the Emeishan large igneous province (ELIP) exhibits a high velocity anomaly, which separates the two aforementioned low velocity anomalies. Low velocity anomaly is also shown beneath the Tengchong volcano. The velocity structures in the vicinity of the 2008 Ms8.0 Wenchuan earthquake, the 2013 Ms7.0 Lushan earthquake and the 2017 Ms7.0 Jiuzhaigou earthquake mainly show high Vp and Vs anomalies and the mainshocks are basically located at the transition zone between the high and low velocity anomalies. Along with the segmentation characteristics of seismic activity, we suggest that areas with significant changes in velocity structures, especially in active fault zones, might have a greater potential to generate moderate to strong earthquakes. [ABSTRACT FROM AUTHOR]

On May 22nd, 2021, an MS7.4 earthquake occurred near the Maduo county of the Qinghai Province, China, within the Bayan Har Block. Seismic activities have been intense in this block, thus whether the Maduo Earthquake will bring subsequent seismic hazards to its surrounding regions raises wide concerns. In this paper, we first calculated the Coulomb failure stress changes caused by the Maduo Earthquake on nearby faults, and estimated how much these faults are brought closer or further from their next failures based on their stressing rates. Next, we combined the Coulomb failure stress changes with the rate-state fictional law to estimate the seismicity rate in the study region in the next decade. A declustered catalogue before the Maduo Earthquake was adopted to calculate background seismicity rate, and rate-state parameters are constrained by fault slip rates. Our results show that the Maduo Earthquake increases stress accumulations in the northwestern portion of the Qingshuihe fault (0.02 MPa at maximum), the two ends of the Kunlun Mountain Pass-Jiangcuo fault (0.01 MPa at maximum), and the northwestern portion of the Maduo-Gande fault (on average ∼0.09 MPa), and seismicity rates are expected to increase near these faults. What is especially worth noting is the seismic hazard in the region extending from the eastern end of the Kunlun Mountain Pass-Jiangcuo fault to the Maqin-Maqu seismic gap on the Eastern Kunlun fault, which is calculated to have experienced a maximum stress increase of 0.67 MPa after the Maduo Earthquake. On the other hand, stress accumulations are reduced in the southern end of the Elashan fault, the Eastern Kunlun fault segment to the west of Maduo, and the northwestern portion of the Dari fault. Seismic hazards are expected to be low in these regions. For the study region as a whole, the probability of an M≥6 earthquake taking place in the next decade is estimated to be 59%, about twice the value calculated for the time period before the Maduo Earthquake. [ABSTRACT FROM AUTHOR]

The Qaidam Basin on the Qinghai-Tibet Plateau is well endowed with a variety of critical metals, such as Li and Rb. However, little is known about the distribution, source, and enrichment mechanisms of these elements. In this paper, we present results of systematic geochemical and H-O-B isotopic analyses of brines in the Tertiary and Quaternary sediments of the Qaidam basin. The results reveal that the paleobrines from oil-bearing anticlines at Dafengshan, Nanyishan, Youquanzi, Jiandingshan, and Jianshishan are significantly enriched in Li and Rb, whose contents are 81.1–128.9 mg L−1 and 4.5–29.2 mg L−1, respectively, reaching levels of economic significance. High Rb contents (up to 12.5 mg L−1) and well-endowment of Li also characterize the Dongtai, Xitai, Yiliping, and Senie salt lakes in the Qaidam Basin. The Tertiary paleobrine average in δD and δ18O at −40.7‰ and 2.84‰, respectively. The paleobrine with the highest Li and Rb has δD and δ18O values close to magmatic water. The δ11B values are lower than those of river water but close to those of geothermal fluids, suggesting that replenishment by deep magmatic hydrothermal fluid is most likely the key mechanism for the anomalous enrichment of these elements in the paleobrines, though evaporation and water-rock reactions have contributed to the critical metal mineralization. The anomalous enrichment of Li and Rb in modern salt lake brines is closely related to the input of volcanic geothermal water. The relatively high Li and Rb contents of intercrystalline brines in salt lakes of the western Qaidam Basin and the increase of Li and Rb contents with increasing depth were caused by upwelling of local paleobrines along the fault zones. [ABSTRACT FROM AUTHOR]

Grass carp (Ctenopharyngodon idella) is a cyprinid species, widely living in the freshwater on the plain area of East Asia. The fish has characteristic comb-like pharyngeal teeth, an adaptation to their typical vegetarian feeding habit. This paper deals with fossil pharyngeal teeth that related to grass carp, found from about 20 localities, ranging from the lower Oligocene to Holocene. Based on the morphology of the teeth, we established two new genera and species related to the genus Ctenopharyngodon (Dezaoia saintjaquensis, Eoctenopharyngodon liui) and two new species of Ctenopharyngodon (C. xiejiaensis and C. orientalis). The first recognized C. idella pharyngeal teeth were from the lower Pliocene of Yushe, Shanxi, and many others from 11 Pleistocene to Holocene localities. Judged from the materials and their occurrences, the grass carp may have originated from the western part of China during the early Oligocene. Throughout the Miocene, the grass-carp-like pharyngeal teeth were discovered from a vast area in China, indicating an appropriate atmosphere for the grass carp to develop, although the climate in the western part of China was possibly drier than that in the eastern part. From the beginning of the Pliocene, as the consequence of a considerable uplift of the Tibetan Plateau, the large rivers in East Asia finally formed, created favorable conditions for the Recent grass carp to thrive. Most teeth were collected in association with fossil mammals. Therefore, we are using the associated fossil mammals as the checking reference against which to test our interpretation of the surrounding environment of the water system in which the grass carp lived. [ABSTRACT FROM AUTHOR]

The evolution of the Changjiang Delta is obviously affected by current rapidly rising sea level and drastically declining river discharge, and it is also vital for the sustainable development of Shanghai and the Changjiang River Economic Belt, which represent China's economic development leader and major national strategic area, respectively. In this paper, the growth pattern of Jiuduansha Island, the largest uninhabited alluvial island in the Changjiang Estuary, is studied in terms of the change in elevation, position and area over the past 50 years through using satellite-derived instantaneous shoreline positions and high/low tide exposure areas based on 497 satellite images from 1974 to 2020; and the influencing factors and future development patterns are further discussed by comparison with other alluvial islands or sandbars in the estuary The results show that Jiuduansha Island has maintained a rapid or even accelerated area growth rate, although the sediment discharge of the Changjiang River has sharply decreased in recent decades This sustained growth is mainly attributed to the existence of the estuarine turbidity maximum zone, coarsening fluvial sediment, onshore sediment replenishment by tide, cone-like geomorphology of Jiuduansha Island, and siltation promotion effect of vegetation The growth rate of the low tide exposure area of Jiuduansha Island increased from 1.9 km2 a−1 in 1974–1990 to 3.0 km2 a−1 in 1990–2020, and the growth rate of the high tide exposure area reached as high as 3.7 km2 a−1 in 1994–2020. The implementation of the Deep-Water Channel Project has significantly affected the evolution of Jiuduansha Island, including shifting the heads of Shangsha and Zhongxiasha from severe retreat to rapid accretion, and promoting tidal flat progradation seaward of the Jiangyanansha and Zhongxiasha, but restricting the growth of the low tide exposure area of Jiuduansha Island. [ABSTRACT FROM AUTHOR]

The North China Craton is the oldest continental block, and has suffered from large-scale lithospheric thinning and destruction, which in turn led to gold deposits in northern China. The decratonic gold deposits in the North China Craton became the most important gold deposits in China, and geophysical methods are key means to detect and discover gold deposits there. In this paper, based on the geological and petrophysical characteristics of the North China Craton, the geological model of the decratonic gold deposits is transformed into a geophysical model. At present, two methods of geophysical exploration of decratonic gold deposits are in use: rapid and efficient exploration on the scale of the ore concentration area, and large depth exploration on the scale of the deposit area. In detail, the airborne electromagnetic, magnetic and gravity methods are used to detect the shallow (1,500 m) anomaly area on the scale of the ore concentration area. Through the ground-controlled source electromagnetic and ground magnetotelluric methods, explorations for targets at significant depth (5,000 m) are carried out in the mining area. Then, taking the Liaodong ore concentration area as an example, geophysical methods are used to discover two prospecting areas around the Jianshanzi Fault in the Qingchengzi ore concentration area, Baiyun-Xiaotongjiapuzi deep prospecting area, and Qingchengzi deep prospecting area. Next, three prospecting areas are delineated around the Jixingou Fault in the Wulong mining area, Wulong deep prospecting area, Weishagou deep prospecting area, and Chang'an deep prospecting area. The anomalies in the ore concentration area and mining area are revealed by means of three-dimensional exploration methods, thereby providing technical support for the exploration of metal minerals such as decratonic gold deposits. [ABSTRACT FROM AUTHOR]

The North China district has been subjected to significant research with regard to the ore-forming dynamics, processes, and quantitative forecasting of gold deposits; it accounts for the highest number of gold reserves and annual products in China. Based on the top-level design of geoscience theory and the method adopted by the National Key R & D Project (deep process and metallogenic mechanism of North China Craton (NCC) metallogenic system), this paper systematically collects and constructs the geoscience data (district, camp, and deposit scales) in four key gold districts of North China (Jiaojia-Sanshandao, Southern Zhaoping, Wulong, and Qingchengzi). The settings associated with the geological dynamics of gold deposits were quantitatively and synthetically analyzed, namely: NCC destruction, metallogenic events, genetic models, and exploration models. Three-dimensional (3D) and four-dimensional (4D) geological modeling was performed using the big data on the districts, while the district-scale 3D exploration criteria were integrated to construct a quantitative exploration model. Among them, FLAC3D modelling and the GeoCube software (version 3.0) were used to implement the numerical simulation of the 3D geological models and the constraints of the fluid saturation parameters of the Jiaojia fault to reconstruct the 4D fault structure models of the Jiaojia fault (with a depth of 5000 m). Using GeoCube3.0, multiple integration modules (general weights of evidence (WofE), Boost WofE, Fuzzy WofE, Logistic Regression, Information Entropy, and Random Forest) and exploration criteria were integrated, while the C-V fractal classification of A, B and C targets in four districts was carried out. The research results are summarized in the following four areas: (1) Four gold districts in the study area have more than three targets (the depth is 3000 m), and the class A, B and C targets exhibit a good spatial correlation with gold bodies that are controlled by mining engineering at depths greater than 1000 m. (2) The Boost WofE method was used to identify the target optimization in 3D spaces (at depths of 3000–5000 m) of the Jiaojia-Sanshandao, Southern Zhaoping, and Wulong districts. (3) The general WofE method is based on the Bayesian theory in 3D space and provides robust integration and target optimization that are suitable for the Jiaojia-Sanshandao and Southern Zhaoping districts in the Jiaodong area; it can also be applied to the Wulong district in the Liaodong area using a quantitative genetic model and an exploration model. Random forest is a multi-objective integration and target optimization method for 3D spaces, and it is suitable for the complex exploration model in the Qingchengzi district of the Liaodong area. The genetic model and exploration criteria associated with the exploration model of the Qingchengzi district were constrained by the common characteristics of the gold fault structure, magmatic rock emplacement in North China, and the strata fold and interlayer detachment structure. (4) Based on the gold reserves and the 3D block unit model of the Sanshandao gold deposit in the Jiaojia-Sanshandao district, the gold contents of the 3D block units in class A and B targets of the ore concentration were estimated to be 65.5% and 25.1%, respectively. The total Au resources of the optimized targets below a depth of 3000 m were 3908 t (including 1700 t reserves), and the total Au resources of the targets at depths from 3000 to 5000 m were 936 t. The study shows that the deep gold deposits in the four gold districts of North China exhibit a strong "transport-deposition" spatial correlation with potential targets. These "transport-deposition" spatial models represent the tectonic-magmatic-hydrothermal activities of the metallogenic system associated with the NCC destruction events and indicate the Au enrichment zones. [ABSTRACT FROM AUTHOR]

Wetland ecosystems have become one of the long-term solutions for mitigating global climate change due to their strong carbon sequestration potential. However, the key carbon cycle processes in wetland ecosystems still lack a systematic summary. In the context of wetland protection and restoration, there is still a lack of consensus on the technical pathways to realize carbon sink multiplication in wetland ecosystems. In this paper, the key processes of carbon cycle, such as photosynthetic carbon uptake, microbial carbon decomposition and carbon deposition and burial, are sorted out and summarized in four major wetland types, namely, swamp and peat wetlands, river and riparian wetlands, lake and lakeshore wetlands, and estuarine and coastal wetlands. Based on the key processes of carbon cycle, three technological pathways for carbon sink multiplication are proposed, including, vegetation carbon sequestration and sink enhancement technology, soil carbon emission reduction technology and carbon deposition and burial technology. The key technologies under each pathway are further refined. And the carbon sink effects of the carbon sink technologies in different wetland types are qualitatively described. Also, wetland protection and restoration methods in corresponding regions are given in the light of the regional characteristics of wetlands in China. This will provide a scientific basis for the strategy of doubling the carbon sinks of China’s wetland ecosystems. [ABSTRACT FROM AUTHOR]

With less than ten years left to meet its pledge to peak carbon dioxide emissions (peak emissions hereafter) by 2030, China has entered a critical emissions reduction stage. How to meet this commitment in a context in which GDP per capita will double from 2020 by 2035 is a major decision-making issue for the Chinese government and people and one which warrants further study. To reveal the relationships between the GDP growth rate, the rate of decrease of carbon intensity and the time to reach peak emissions, this study translates the question as to "when China's carbon emissions peak will occur" into "how can one control the rate of carbon intensity decrease at a given GDP growth rate". In the light of the results of a random forest algorithm used to identify and project the key drivers of carbon intensity in China, a mathematical model was developed to simulate different scenarios relating to decreases in carbon intensity. The date at which Chinese carbon emissions will peak is predicted by comparing the rate of decrease of carbon intensity with the GDP growth rate. The results show that the time to peak emissions depends on the relationship between the rate of decrease of carbon intensity and the GDP growth rate, where the former depends mainly on the energy structure and policy. If China's annual GDP growth rate were 5.0% during the 15th Five-Year Plan, and if the share of non-fossil energy in total energy consumption were 23.0% or above, China's carbon emissions will peak before 2030. If the share of non-fossil fuels were 20.0% or less, China might not be able to reach its 2030 target. In this latter case an acceleration in the pace of energy restructuring would be required to reach peak emissions before 2030. The projected peak emissions scenarios suggest that the carbon peak will occur between 2025 to 2029, with average peak emissions of 11.2 billion tons and a distribution ranging from a minimum of 10.5 billion and a maximum of 11.9 billion tons. If the GDP growth rate were 4.5%, 5.5% or 6.0% during the 15th Five-year Plan, the share of non-fossil energy must reach 23.0%, 25.0% or 27.0%, respectively, to ensure that emissions peak by 2030. The results of this study provide a series of reference points for China's pursuit of feasible pathways to peak carbon emissions by 2030. [ABSTRACT FROM AUTHOR]

The two leading modes of winter surface air temperature (SAT) over China during 1961–2017 are a spatially consistent pattern and a north-south dipole pattern. Based on the two leading modes, the characteristics of the extreme cold and warm days in the two patterns, defined by the standard deviation larger than 1.28 or smaller than −1.28 in the time series of the two leading modes, are analyzed. With the increase of winter SAT during 1961–2017, the number of spatially consistent extreme cold days decreased and their occurrence was restricted to late December to early January, whereas the number of spatially consistent extreme warm days increased significantly in January and February. Global warming is associated with an increase in the spatially consistent extreme warm days and a decrease in spatially consistent extreme cold days, but has little relation to the sum of extreme cold and warm days of either the spatially consistent or north-south dipole pattern. The Siberian High (SH) is the main factor controlling the sum of spatially consistent extreme warm and cold days. The strong (weak) SH before (after) the 1990s corresponds to an increase (decrease) in the sum of the spatially consistent extreme warm and cold days. The occurrences of extreme south-cold-north-warm and extreme south-warm-north-cold days are related to the north-south difference of the SH. When the center of the SH is in mid-high latitudes, the extreme south-warm-north-cold (south-cold-north-warm) days occur more (less) often. During the winters of 1961–2017, the total number of extreme cold and warm days of the north-south dipole pattern changes negligibly. The North Atlantic meridional overturning circulation (AMOC) may be the main factor affecting the sum of the extreme cold and warm days of the two types of SAT pattern in China. [ABSTRACT FROM AUTHOR]

Herbaceous marsh is the most widely distributed type of marsh wetland ecosystem, and has important ecological functions such as water conservation, climate regulation, carbon storage and fixation, and sheltering rare species. The carbon sequestration function of herbaceous marsh plays a key role in slowing climate warming and maintaining regional environmental stability. Vegetation biomass is an important index reflecting the carbon sequestration capacity of wetlands. Investigating the biomass of marsh vegetation can provide a scientific basis for estimating the carbon storage and carbon sequestration capacity of marshes. Based on field survey data of aboveground biomass of herbaceous marsh vegetation and the distribution data set of marsh in China, we analyzed the aboveground biomass and its spatial distribution pattern of herbaceous marsh on a national scale for the first time. The results showed that in China the total area of herbaceous marsh was 9.7×104 km2, the average density of aboveground biomass of herbaceous marsh vegetation was 227.5±23.0 g C m−2 (95% confidence interval, the same below), and the total aboveground biomass was 22.2±2.2 Tg C (1 Tg=1012 g). The aboveground biomass density of herbaceous marsh vegetation is generally low in Northeast China and the Tibetan Plateau, and high in central North China and coastal regions in China. In different marsh distribution regions of China, the average biomass density of herbaceous marsh vegetation from small to large was as follows: temperate humid and semi-humid marsh region (182.3±49.3 g C m−2)−2)−2)−2)−2). Due to the different area of herbaceous marsh, the total aboveground biomass of herbaceous marsh vegetation in different marsh distribution regions was the largest in the temperate humid and semi-humid marsh region (9.6±2.6 Tg C), and was the smallest in the coastal marsh region (1.1±0.1 Tg C). The spatial distribution of aboveground biomass of herbaceous marsh vegetation in China has obvious non-zonality characteristics, but also presents certain zonality in some regions. The aboveground biomass of herbaceous marsh vegetation in the Tibetan Plateau decreased with the increase of altitude. With the aggravation of drought, the aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions and temperate arid and semi-arid regions decreased first and then did not obviously change. The aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions was relatively larger in the regions with higher average annual temperature. The results can provide scientific basis for accurately evaluating the adjustment action of wetland ecosystems on climate, and provide decision support for adaptive management of wetland ecosystems. [ABSTRACT FROM AUTHOR]

In this study, high-resolution Moho depth and average crustal Vp/Vs ratio distributions in northeast China were obtained through joint inversion of receiver functions and gravity data. The new joint inversion method comprehensively considers the complementary imaging strengths of the receiver functions in the vertical direction and the gravity data in the lateral direction. To a certain extent, it can reduce the adverse effects of the receiver function data caused by the sedimentary layers of the basin, the inclination of the Moho, and the structure heterogeneity below the station. In preprocessing the receiver function data, a regularized virtual station network was constructed using the teleseismic receiver function waveform reconstruction method to improve the overall spatial resolution. To filter the gravity data, the velocity structure-guided gravity filtering method and gravity upward continuation were used for the shallower region above the Moho and the deeper region below the lithosphere, respectively. The newly obtained model shows that the Moho depths of the Hailar Basin, Erlian Basin, Sanjiang Basin, and Bohai Bay Basin are slightly shallower than those of the surrounding areas, while the Moho depths of the Greater Xing'an Range, Lesser Xing'an Range, and Zhangguangcai Range are slightly deeper. Compared with previous results, the refined Moho depth distribution obtained in this study has a better correspondence with topographic relief and basin boundaries, and the contrast is more evident across the north-south gravity gradient lineament (NSGL). In the eastern part of the Songliao Basin, the Moho is relatively shallow, and there is a high Vp/Vs ratio, which may have been caused by the intrusion of hot mantle materials into the crust induced by lateral extension of the Songliao Basin. The high Vp/Vs ratio of the crust below the Changbaishan volcanic area implies the existence of partial melting in the crust caused by upwelling hot mantle materials. [ABSTRACT FROM AUTHOR]

The contemporary carbon balance over the Tibetan Plateau is highly uncertain with a ten-fold difference between various estimates. In a warming world, the potential exists for a large carbon release from its permafrost which could compromise China's 2060 carbon-neutral goal. Here, we used a satellite- and inventory-based approach, ecosystem models, and atmospheric inversions to estimate that the carbon sink was 33.12–37.84 TgC yr−1 during 2000–2015. The carbon sink induced by climate change and increasing CO2 levels largely overcompensated for a livestock grazing-induced carbon source of 0.38 TgC yr−1. By 2060, the carbon sink is projected to increase by 38.3–74.5% under moderate to high emissions scenarios, with the enhanced vegetation carbon uptake outweighing the warming-induced permafrost carbon release. The restoration of degraded grassland could sequestrate an additional 9.06 TgC yr−1, leading to a total carbon sink of 57.78–70.52 TgC yr−1. We conclude that the Tibetan Plateau's ecosystems absorbed two-and-a-half times the amount of its cumulative fossil CO2 emissions during 2000–2015 and that their carbon sinks will almost double in strength in the future, helping to achieve China's pledge to become carbon neutral by 2060. [ABSTRACT FROM AUTHOR]

Mid-high maturity shale oil is the most realistic field for the scale breakthrough of terrestrial shale oil production in China. Generally, three deficiencies hinder shale oil development in China: heavy oil density, small sweet spot areas, and poor distribution continuity. Thus, identifying the "sweet spots" in shale oil reservoirs is critical for the efficient exploration and development of terrestrial shale oil. This study targets the siltstone type (Class-II shale oil) and pure shale type (Class-III shale oil) of the Chang 7 Member in the Ordos Basin, and identifies three stratigraphic units, namely the hydrocarbon accumulation unit, hydrocarbon generation unit, and hydrocarbon retention unit, which together constitute the in-source "shale oil system". The hydrocarbon accumulation unit is mainly siltstone, where the hydrocarbons are migrated from shales. It has favorable pore-throat network connectivity with a pore connectivity ratio of 32–57%, being the siltstone-type sweet spots. The hydrocarbon generation unit is mainly composed of high-TOC mudstone/shale and is the main contributor to in-source hydrocarbon generation and expulsion. This unit has high three-dimensional connectivity (28–30%), as shown by the pore-throat network model, associated with vertical paths for hydrocarbon expulsion. The hydrocarbon retention unit is mainly composed of low-TOC mudstone/shale retaining self-generated and migrated hydrocarbons. The pore connectivity rate is 17–42%, and the pore-throat network connectivity direction is uneven. Light and low-carbon-number hydrocarbons are preferentially trapped or even sealed in small pores of the retention unit, forming the typical mudstone/shale-type sweet spots. In the process called shale oil intra-source migration, the oil migrates in source rocks causing component fractionation, which allows more shale oil to enrich in the hydrocarbon accumulation and retention units to form sweet spots, compared with the hydrocarbon generation unit. The migration paths include the one from mudstone/shale to siltstone interlayers and that from the high-TOC mudstone/shale intervals to the low-TOC intervals. The in-source accumulation of shale oil shows the differentiated enrichment model featuring "high-TOC mudstone/shale generating hydrocarbons, low-TOC mudstone/shale retaining hydrocarbons, siltstone accumulating hydrocarbons and multiple intra-source migration paths". In the Ordos Basin, the organic-lean (TOC 1–3%) mudstone/shale intervals appear to be the sweet spots of shale oil, where there are abundant medium-short-chain hydrocarbons retained with high flowability. After fracturing stimulation, their production conditions may be even superior to those of siltstones. This proposed idea changes the previous strategy to look for sweet spots in high-TOC intervals derived from the shale gas industry. [ABSTRACT FROM AUTHOR]

The Chinese Meridian Project (CMP) is devoted to establishing a comprehensive ground-based monitoring network for China's space weather research. CMP is a major national science and technology infrastructure project with the participation of more than 10 research institutions and universities led by the National Space Science Center of the Chinese Academy of Sciences. CMP is planned to be constructed in two phases: CMP phases I and II. The first phase (CMP-I) started construction in 2008 and completed in 2012, after which it entered the operation stage. The 10-year observation of CMP-I has made significant scientific discoveries and achievements in the research fields of the middle and upper atmospheric fluctuations, metal layers in the mesosphere and lower thermosphere, ionospheric disturbances and irregularities, geomagnetic disturbances, and influences of solar activity. The review summarizes the main observations and research achievements, space weather forecast modeling and methods based on CMP-I over the past 10 years, and presents a future extension perspective along with the construction of CMP-II. [ABSTRACT FROM AUTHOR]

An M6.8 earthquake occurred in Luding, Sichuan Province, China, on September 5, 2022. Since towns and villages in the earthquake-stricken area are densely populated, the earthquake caused severe fatalities and economic losses. Rapid estimation of earthquake intensity and disaster losses is significantly important for post-earthquake emergency rescue, scientific anti-seismic deployment, and the reduction of casualties and economic losses. Therefore, we make a preliminary rapid estimation of the earthquake intensity and disaster losses in the aftermath of the Luding earthquake. The seismic intensity represents the distribution of earthquake disasters and the degree of ground damage and can be directly converted from the peak ground velocity (PGV) map. To obtain a reliable PGV distribution map of this earthquake, we combined the finite-fault model constrained by seismic observations, with the complex three-dimensional (3D) geological environment and topographical features to perform strong ground motion simulation. Then, we compared the consistency between the simulated ground motion waveforms and observations, indicating the plausibility and reliability of simulations. In addition, we transformed the PGV simulation results into intensity and obtained a physics-based map of the intensity distribution of the Luding earthquake. The maximum simulated intensity of this earthquake is IX, which is consistent with the maximum intensity determined from the post-earthquake field survey. Based on the simulated seismic intensity map of the Luding earthquake and the earthquake disaster loss estimation model, we rapidly estimated the death and economic losses caused by this earthquake. The estimated results show that the death toll caused by this earthquake is probably 50–300, with a mathematic expectation of 89. Thus the government should launch a Level II earthquake emergency response plan. The economic losses are likely to be 10–100 billion RMB, with a mathematical expectation of 23.205 billion RMB. Such seismic intensity simulations and rapid estimation of disaster losses are expected to provide a preliminary scientific reference for governments to carry out the targeted deployment of emergency rescue and post-disaster reconstruction. [ABSTRACT FROM AUTHOR]

Since Shi et al. proposed that the climate in the drylands of Northwest China experienced a significant transition from a "warming and drying" trend to a "warming and wetting" trend in the 1980s, researchers have conducted numerous studies on the variations in precipitation and humidity in the region and even in arid Central Asia. In particular, the process of the "warming and wetting" trend by using obtained measurement data received much attention. However, there remain uncertainties about whether the "warming and wetting" trend has paused and what its future variations may be. In this study, we examined the spatiotemporal variations in temperature, precipitation, the aridity index (AI), vegetation, and runoff during 1950–2019. The results showed that the climate in the drylands of Northwest China and the northern Tibetan Plateau is persistently warming and wetting since the 1980s, with an acceleration since the 1990s. The precipitation/humidity variations in North China, which are mainly influenced by summer monsoon, are generally opposite to those in the drylands of Northwest China. This reverse change is mainly controlled by an anomalous anticyclone over Mongolia, which leads to an anomalous easterly wind, reduced water vapor output, and increased precipitation in the drylands of Northwest China. While it also causes an anomalous descending motion, increased water vapor divergence, and decreased precipitation in North China. Precipitation is the primary controlling factor of humidity, which ultimately forms the spatiotemporal pattern of the "westerlies-dominated climatic regime" of antiphase precipitation/humidity variations between the drylands of Northwest China and monsoonal region of North China. The primary reasons behind the debate of the "warming and wetting" trend in Northwest China were due to the use of different time series lengths, regional ranges, and humidity indices in previous analyses. Since the EC-Earth3 has a good performance for simulating precipitation and humidity in Northwest and North China. By using its simulated results, we found a wetting trend in the drylands of Northwest China under low emission scenarios, but the climate will gradually transition to a "warming and drying" trend as emissions increase. This study suggests that moderate warming can be beneficial for improving the ecological environment in the drylands of Northwest China, while precipitation and humidity in monsoon-dominated North China will persistently increase under scenarios of increased emissions. [ABSTRACT FROM AUTHOR]

The Mesozoic tectonic framework of the eastern South China is mainly controlled by subduction, turning toward, and rollback of the Pacific Plate. Recent studies of receiver function imaging and ambient noise tomography have revealed the "Y-shaped" thinnest crustal belt in the eastern South China under the overall extension of the lithosphere. However, the deep dynamic environment and formation mechanisms of the thin crustal belt remain debatable. Here we obtained high-resolution images of the crustal thickness and Poisson's ratio in the eastern South China Block applying the recently proposed H-κ-c receiver function method, using data recorded by 305 dense portable broadband stations and 219 permanent stations surrounding. Additionally, we discussed the deep dynamic formation mechanism of the "Y-shaped" thinnest crustal belt coupled with two common conversion point stacked images at key locations. Results show that the average crustal thickness of the study area is 33 km (thin crust) and the average Poisson's ratio is 0.24 (low ratio). The overall crustal thinning toward the continental margin is likely because eastern South China was in a back-arc extension environment, which was induced by the rollback of the subducted plate in the Early Cretaceous. The crustal thickness of the "Y-shaped" thinnest crustal belt is <30 km, which is 3–5 km thinner than that outside the zone. The eastern branch is distributed along the trajectory of Nanchang-Ji'an-Ganzhou-Shaoguan-Guangzhou, and the western branch is around the Jianghan-Xiangzhong Basin, both of which intersect in Nanling. The eastern branch of the thin crustal zone indicates the potential location of the Pacific subduction slab breakoff, and the formation mechanism may be related to the interaction of deep-shallow processes, including the upwelling of mantle heat flow through the slab window and transtensional pre-existing faults. We developed a dynamic model that combines subduction-breakoff-rollback processes of the Paleo-Pacific Plate and accompanying deep fluid upwelling to explain the regional extension of the South China lithosphere, the formation mechanism of the thinnest crustal belt, and the distribution of granitic plutons. [ABSTRACT FROM AUTHOR]

China's helium resource is highly dependent on overseas imports. Organic-rich and U/Th-rich shale reservoirs generally contain helium, and although the helium content is low, the total reserve is large. Therefore, the effective development and utilisation of shale-type helium resources is a realistic way to improve the security of helium resources in China. In this study, the generation mechanism, helium source and content, migration modes and pathways, controlling factors of enrichment, distribution pattern, and resource potential of the helium were analysed, using the Wufeng-Longmaxi shale in the Sichuan Basin and its periphery. Furthermore, countermeasures were proposed for shale-type helium exploration and development. The results show that the Wufeng-Longmaxi shale has a high content of U and Th and a good ability to generate helium. The helium is generated by a typical crustal source of helium and is characterised by self-generation, self-storage, and wide distribution. The helium resource potential is a product of its content and the resources of the associated natural gas. The continuous supply of helium and effective preservation are the main geological factors that control the enrichment of shale-type helium. The preliminary evaluation results show that the reserves of helium in proven shale gas reserves are 10.8×108 m3 in the Sichuan Basin and its periphery, where the extra-large helium fields are likely to be discovered. Additionally, 0.0912×108 m3 of helium was produced, along with the annual production of shale gas. To avoid the waste of helium and to improve the self-supply ability, it is suggested that research on the resource potential, enrichment mechanism, and distribution pattern of shale-type helium should be carried out as soon as possible, and helium extraction techniques for helium-bearing natural gas should be studied. [ABSTRACT FROM AUTHOR]

Co-occurrence of surface ozone (O3) and fine particulate matter (PM2.5) pollution (CP) was frequently observed in Beijing-Tianjin-Hebei (BTH). More than 50% of CP days occurred during April–May in BTH, and the CP days reached up to 11 in two months of 2018. The PM2.5 or O3 concentration associated with CP was lower than but close to that in O3 and PM2.5 pollution, indicating compound harms during CP days with double-high concentrations of PM2.5 and O3. CP days were significantly facilitated by joint effects of the Rossby wave train that consisted of two centers associated with the Scandinavia pattern and one center over North China as well as a hot, wet, and stagnant environmental condition in BTH. After 2018, the number of CP days decreased sharply while the meteorological conditions did not change significantly. Therefore, changes in meteorological conditions did not really contribute to the decline of CP days in 2019 and 2020. This implies that the reduction of PM2.5 emission has resulted in a reduction of CP days (about 11 days in 2019 and 2020). The differences in atmospheric conditions revealed here were helpful to forecast the types of air pollution on a daily to weekly time scale. The reduction in PM2.5 emission was the main driving factor behind the absence of CP days in 2020, but the control of surface O3 must be stricter and deeper. [ABSTRACT FROM AUTHOR]

The food system is one of the major sources of anthropogenic greenhouse gas (GHG) emissions. The impact of emission transfer due to the separation between food production and consumption within the context of carbon neutrality remains unclear. In this study, we constructed an emission inventory for three types of grains at the production stage of their life cycle and then analysed the spatiotemporal evolution characteristics of the grain supply and demand. With the use of a spatial equilibrium model, we simulated the spatial distribution flow of the different types of grains from 1990 to 2018 and calculated the resulting GHG emission transfer efficiency. The main results include the following: (1) The imbalance between the grain supply and demand intensified, which was mainly reflected in the distance between the geographic centre of the grain supply and consumption increasing 3.2 times, and thus, the self-sufficiency decreased. (2) The total emission transfer TET of rice and wheat decreased because of the increase in the intra-regional supply, while that of maize gradually increased due to the increase in the inter-regional supply. (3) Overall, grain trade improved the carbon efficiency of grain production in China. The trade efficiency of crops varied, with wheat and maize leading to overall effective carbon reductions, while the carbon transfer efficiency of rice from trade was relatively low. (4) The carbon footprint of grain production in China's provinces exhibited a downward trend, but due to the intensified separation between the grain supply and demand, certain major grain-producing areas achieved inefficient carbon increases. Therefore, we suggest further optimization of the spatial structure of planting and breeding, strengthening of the grain supply in the region, and enhancement in the optimization of the low-carbon production structure and adjustment of cultivated land use combined with regional governance strategies. The application of these measures could contribute to achieving dual-carbon goals. [ABSTRACT FROM AUTHOR]

The existence of a 0.3 Ga "great unconformity" between the Mesoproterozoic "Undefined System" Xiamaling Formation and the "Neoproterozoic" Longshan Formation has long been controversial. In this study, stratigraphy, sedimentology, detrital zircon dating, lithium isotope, and major and trace elements were applied to systematically analyze their relationship. Results demonstrate that coarse to fine sandstone-mudstone normal cycles with different grades and thicknesses exist from the Xiamaling to the Longshan formations. Sedimentary succession formed from a restricted platform with lagoon-shallow marine shelf-tidal flat-beach and tidal shoal developing in ascending order. The pebbly sandstone at the bottom of the Longshan Formation does not have the properties of basal conglomerate with tectonic significance. The youngest detrital zircon is older than 1.6 Ga for the Longshan Formation and overlying Jing'eryu Formation sandstones. In addition, no (zircon) provenance has been found from the large igneous province of 1.32–1.2 Ga in Xiamaling Formation. The δ7Li isotope values exhibit a gradually increasing trend. The Li content and CIA (Chemical index of alteration) gradually decreases from the top of the Xiamaling Formation to the lower part of the Longshan Formation. Simultaneously, as K2O/Al2O3 and FeO/Fe2O3 decreases, Na2O/Al2O3 increases, and Li/Al, V/Cr, and V/(V+Ni) fluctuates slightly. At the boundary, the Ce/Ce* and Eu/Eu* show positive and negative anomalies, respectively. Further, the Rb/Sr and Al/Si values decrease, and U/Th values increase. This indicates that the geochemistry of the weathering crust at the interface of the Xiamaling Formation-Longshan Formation is not characteristic. However, it indicates a weakening of continental weathering intensity from the bottom to the top of the interface. These results do not support the existence of a large unconformity between the Xiamaling and the Longshan formations. Therefore, it is suggested that the Longshan Formation-Jing'eryu Formation should be moved to the lower level in the stratigraphic chart, where it should form part of the Mesoproterozoic "Undefined System" along with the Xiamaling Formation. On this basis, the paleogeography of the Xiamaling Formation-Longshan Formation-Jing'eryu Formation sedimentary period in the Yanliao area of North China has been reclassified. [ABSTRACT FROM AUTHOR]

Evaluating the hydrocarbon generation potential of highly mature organic matter is a key and critically challenging area of research in petroleum geochemistry. To explore this issue, we used negative ion electrospray ionization-Fourier transform-ion cyclotron resonance-mass spectrometry to investigate the molecular evolution of N-containing compounds in Carboniferous-lower Permian source rocks with a range of maturities in the northwestern Junggar Basin, China. The N1 compounds formed from on-fluorescent chlorophyll catabolites (NCCs), which record the characteristics of the residual soluble organic matter. These components remain in the source rocks after hydrocarbon generation and expulsion, and enable evaluation of the hydrocarbon generation potential. The newly defined indexes of molecular evolution, which are the polymerization index P1 ([DBE 18+DBE 15]/[DBE 12+DBE 9]_N1) and alkylation index R1 (RC6–35/RC0–5), combined with the vitrinite reflectance (VRo) and paleo-salinity index (β-carotane/nCmax), can identify the factors that control the evolution of highly mature organic matter. The main factor for source rocks deposited in a weakly saline environment is the maturity, but for a highly saline environment both the maturity and salinity are key factors. The high salinity inhibits the molecular polymerization of organic matter and extends the oil generation peak. Given the differences in the bio-precursors in saline source rocks, we propose a new model for hydrocarbon generation that can be used to determine the oil generation potential of highly mature organic matter. [ABSTRACT FROM AUTHOR]

Deep soil organic carbon (SOC) plays an important role in carbon cycling. Precisely predicting deep SOC at the regional scale is crucial for the accurate assessment of carbon sequestration potential in soils but has been challenging for a century. Herein, we developed a depth distribution function-based empirical approach to predict SOC in deep soils at the regional scale. We validated this approach with a dataset from four regions of the world and examined the application of this approach in China's Loess Plateau. We found that among the reported depth distribution functions describing vertical patterns of SOC, the negative exponential function performed best in fitting SOC along the soil profile in various regions. Moreover, the parameters (i.e., Ce and k) of the negative exponential function were linearly correlated to surface SOC (0–20 cm) and the changing rates of SOC within the topsoil (0–40 cm). Based on the above relationships, the empirical equations for predicting the negative exponential parameters are established. The validation results from site-specific and regional dataset showed that combining the negative exponential function and such empirical equations can precisely predict SOC concentration in soils down to 500 cm depth. Our study provides a simple, rapid and accurate method for predicting deep soil SOC at the regional scale, which could simplify the assessment of deep soil SOC in various regions. [ABSTRACT FROM AUTHOR]

Cratons formed due to the specific melting regime of the primitive mantle with elevated mantle temperature during Archean. However, each craton has undergone a distinct evolution history, and some have lost their stability. To investigate to what degree cratons in comparison with one another have been modified from their analogous initial form, we employed Sn-Pn differential (PSn) traveltimes to derive Vp/Vs ratio, which is thought to be related to Mg# of the uppermantle. We assessed Pn, Sn, and PSn data using three datasets based on epicentral distance: (1) 2°–12°, (2) 2°–7°, and (3) 7°–12°. The results suggest that most cratons show comparable seismic properties with high velocities and low Vp/Vs ratio, implying a highly depleted uppermost mantle that resembles the original residue from the partial melt extraction of the primitive mantle during the Archean. Conversely, the Eastern North China Craton (ENCC) displays the lowest P- and S-wave velocities, and noticeable high Vp/Vs ratios in all datasets, implying a systematic difference with other cratons. This observation suggests a scenario of total removal of the depleted Archean mantle lithosphere beneath the ENCC. In contrast, the Ordos Block located at the western part of the North China Craton (WNCC) shows velocities and Vp/Vs ratio comparable with those of the typical cratons, suggesting that it has still maintained its Archean mantle lithosphere. The Wyoming Craton has a high Vp/Vs ratio similar to that of the ENCC and a high P-wave velocity comparable to that of the typical cratons. These features suggest that the Archean mantle lithosphere has been significantly modified rather than totally removed and replaced by a younger fertile mantle. The Indian Craton presents a low Vp/Vs ratio and comparatively high velocities at shallow parts of the mantle lithosphere but a high Vp/Vs ratio at deeper parts similar to that of the ENCC, suggesting a partial modification of the Indian Craton at deeper parts. [ABSTRACT FROM AUTHOR]

We report the extraordinarily preserved euarthropod Sidneyia minor sp. nov. from the Cambrian Stage 3 Xiaoshiba Lagerstätte in Yunnan, South China. So far this is the earliest occurrence of the genus. As with other species of Sidneyia, the new taxon shares similar features such as a crescent-shaped head shield with paired lateral notches for stalked eyes, but more significantly and new, is the presence of three pairs of post-antennal appendages beneath the head shield identified by micro-CT methods. We conclude that Sidneyia is a sister group to other members of Vicissicaudata within the diverse radiation of Artiopoda. [ABSTRACT FROM AUTHOR]

Peatlands are some of the largest carbon reservoirs in terrestrial ecosystems and play a key role in the global carbon cycle. Understanding peatland development, carbon accumulation processes, and the peatland response to varying forcing factors over different temporal and spatial scales helps reveal the underlying processes and general patterns of these ecosystems. To assess the role of climate and local conditions in peatland development, the basal samples from 23 peat cores and three well dated long peat cores were used to explore peatland initiation, lateral expansion, and carbon accumulation rate in the Baijianghe peatland located in the Changbai Mountains, Northeast China. Our results reveal that the Baijianghe peatland was initiated from forest conditions at 7.9 cal. kyr BP and then expanded laterally by paludification. The rapid expansion between 5 and 4 cal. kyr BP likely resulted from high precipitation and gentle topography. The mean carbon accumulation rates of the three long peat cores were 36.3, 39.1 and 48.4 g C m−2 yr−1, respectively, which are higher than rates from the northern peatlands. Both climate and local conditions have exerted an important influence on carbon accumulation rates in the Baijianghe peatland since the middle Holocene. The carbon accumulation patterns between 5 and 1.5 cal. kyr BP were probably linked to local conditions rather than climatic settings, including topography, hydrological conditions, and plant composition. The consistently decreasing carbon accumulation rate values at all locations within the BJH peatland over the last 1.5 cal. kyr BP suggests that climate is the primary control. This study highlights the varying primary controls on the process of peatland development and reveals the important role of local conditions in carbon accumulation. [ABSTRACT FROM AUTHOR]

This study focuses on the illumination and temperature at China's next lunar candidate landing site Shackleton crater. We used the NASA's SPICE system to evaluate the terrain obscuration effect on real-time illumination; the resulting illumination map resembles previous studies, validating the methodologies used in our study. In addition, we estimated an accumulated illumination map for the period of likely rover movement. The map indicates the illuminated inner wall of the Shackleton crater is close to 27% of the whole, meaning that the rover will likely receive solar radiation during its movement. Using the real-time illumination and the distributed 1-D thermal diffusion model, we continuously evaluated the regolith temperature for more than 20 years to stabilize the temperature, and selected the temperature of the end time as the initial value used in a thermal study set for July 20, 2023 and May 8, 2027. Our results indicate the temperature in the permanent shadow region remains nearly constant, thus validating the stability of our estimated initial temperature. Our results also indicate that the surface temperature is more sensitive to transient illumination, but the subsurface temperature is more likely to be associated with the accumulated illumination. This difference indirectly implies that the conductivity of the lunar regolith is inefficient. The locations receiving more solar radiation show a temperature larger than the threshold (∼112 K) of ice stability. The permanently shadowed regions can be as cold as 25 K, and such extreme coldness is a hazard to the rover. There are suitable temperature locations which have a warm surface but cold subsurface to preserve water ice. To further ensure normal rover movement, we provided a map of suitable temperature sites and found that these locations exist not only in the Shackleton crater's inner wall, but also outside the crater. We suggested four trade-off sampling sites with suitable temperatures and gradual slopes. [ABSTRACT FROM AUTHOR]

Inter-city mobility is one of the most important issues in the UN Sustainable Development Goals, as it is essential to access the regional labour market, goods and services, and to constrain the spread of infectious diseases. Although the gravity model has been proved to be an effective model to describe mobility among settlements, knowledge is still insufficient in regions where dozens of megacities interact closely and over 100 million people reside. In addition, the existing knowledge is limited to overall population mobility, while the difference in inter-city travel with different purposes is unexplored on such a large geographic scale. We revisited the gravity laws of inter-city mobility using the 2.12 billion trip chains recorded by 40.48 million mobile phone users' trajectories in the Jing-Jin-Ji Region, which contains China's capital Beijing. Firstly, unlike previous studies, we found that non-commuting rather than commuting is the dominant type of inter-city mobility (89.3%). Non-commuting travellers have a travel distance 42.3% longer than commuting travellers. Secondly, we developed more accurate gravity models for the spatial distribution of inter-city commuting and non-commuting travel. We also found that inter-city mobility has a hierarchical structure, as the distribution of inter-city travel volume follows Zipf's law. In particular, the hierarchy of non-commuting travel volume among the cities is more in line with an ideal Zipf distribution than commuting travel. Our findings contribute to new knowledge on basic inter-city mobility laws, and they have significant applications for regional policies on human mobility. [ABSTRACT FROM AUTHOR]

The West Qinling orogen in central China, formed from continental collision between the North China and Yangtze cratons in the Late Triassic, hosts numerous gold deposits with a total Au endowment of about 2000 t. Most deposits were emplaced at ca. 250–195 Ma and are genetically associated with the Triassic orogenesis. Here in situ U-Pb titanite dating with laser ablation inductively coupled plasma mass spectrometry indicates the Ma'anqiao gold deposit in the northern portion of this orogen has a distinctive age and under a contrasting tectonic regime. This structurally controlled gold deposit is hosted in Late Ordovician to Early Silurian sub-greenschist facies metasedimentary rocks. The gold mineralization is hosted in quartz-pyrite-pyrrhotite veins and pyrite-pyrrhotite disseminations in hydrothermally altered rocks, which are crosscut by K-feldspar-calcite-chlorite±pyrite veins. Titanite, present both in the disseminated sulfide ores and later veins, was used for in situ U-Pb dating. Titanite from three disseminated sulfide ore samples with Th and U averaging 27.46 and 39.31 ppm (1 ppm=1 µg g−1), respectively, yielded lower-intercept ages of 121.1±3.1 to 120.7±3.5 Ma (2σ) in the Tera-Wasserburg diagram. Titanite from three later vein samples with much lower Th and U concentrations averaging 2.74 and 16.21 ppm, respectively, yielded overlapping ages of 120.8±3.2 to 120.3±5.8 Ma (2σ). These new titanite U-Pb ages tightly constrain the formation of the Ma'anqiao gold deposit at ca. 121–120 Ma and, when combined with independent geological data, indicate it is not related to the Triassic Qinling orogeny. Rather, its formation is attributed to lithospheric thinning and destruction of the North China craton during the Late Jurassic to Early Cretaceous which has generated numerous gold deposits along the southern margin of this craton. This catastrophic event caused extensive magmatism in large areas of the North Qinling terrane and northern edge of the West Qinling orogen immediately to the south of the North China craton. The heat flux and elevated geothermal gradients associated with this magmatism could have induced prograde metamorphism of the Paleozoic sedimentary infrastructure in and beneath these areas with the derived fluids ascending along pre-existing crustal-scale regional structures to form the Ma'anqiao gold deposit. We suggest that areas in the North Qinling terrane that have been affected by the Late Mesozoic magmatism are potential targets for future exploration of the decratonization-related gold deposits. Additionally, this study highlights the use of titanite U-Pb dating as a robust geochronometer for metasedimentary rock-hosted gold deposits in Phanerozoic orogens, which has previously not been utilized. [ABSTRACT FROM AUTHOR]

During the sustainable development of land surface system, different territories undertake different functions. The understanding and representation of territorial differentiation of the land surface system is the main purpose of comprehensive function regionalization research. Focusing on the theoretical gap of comprehensive geographical regionalization, that is, the spatial decoupling of the physical environment and human activities, the non-nested relationship of spatial scale transformation, and the persistence and uncertainty of the dynamic evolution of territorial functions, this research proposed the identification principles and division methods of comprehensive functional regions. Based on the major function zoning in China, the systematic classification method with function orientation was employed to delineate the comprehensive functions of each territory, such as ecological security, food production and urban development. Then, the geographical regionalization method, which follows the principles of interconnection of different regionalization objectives at different levels and a combination of top-down decomposition and bottom-up aggregation, was used to determine the geographic boundaries. To meet the objective requirements of flexible and dynamic boundaries, two sets of land regionalization schemes for 2035 and 2050 were finally formed, each of which had three spatial levels. The first-level regionalization identified four major regions, which comprehensively represented the relatively stable state of China's land development and protection pattern under the leading role of physical environment differentiation. The second-level regionalization identified 12 regions, which comprehensively represented the spatial layout of a new development pattern of multi- and inter-provinces coordinating the innovation chain, industrial chain and supply chain based on a relatively independent and complete natural carrier. The third-level regionalization identified 80 sub-regions, which comprehensively represented the functional differentiation patterns of sub-provinces during sustainable development. Compared with the current geographical differentiation research, the study of territorial function differentiation has academic values for the development of integrated geography in exploring the territorial system of the human-environment relationship, and it can provide a scientific basis for determining the territorial model of sustainable development and optimizing the pattern of spatial development and protection in China. [ABSTRACT FROM AUTHOR]

Understanding the stability of terrestrial carbon sinks (S-TCS) contributes to more accurate prediction of the terrestrial carbon sink (TCS) in the context of future global change and helps inform climate change mitigation policies. Here, focusing on China, we analyzed the spatial distribution and driving mechanisms for the S-TCS, quantified by the interannual variability of the TCS, using three independent approaches (atmospheric inversions, ecosystem carbon cycle models, and machine learning models based on flux tower observations). We found that the interannual variability of the TCS in China is relatively small compared with the conterminous United States and geographic Europe, indicating a generally stable TCS in China. Spatially, the S-TCS is lower in the North China Plain, Northeast China Plain, and western Yunnan-Guizhou Plateau than in other regions, with varying underlying mechanisms. Large interannual variations in precipitation and high TCS sensitivities to precipitation fluctuations explain the low S-TCS in the North China Plain and Northeast China Plain, while high TCS sensitivities to temperature variations drive the low S-TCS in the western Yunnan-Guizhou Plateau. Our findings highlight the importance of considering local contexts for stabilizing and enhancing China's TCS in a changing environment. [ABSTRACT FROM AUTHOR]

As the globe has witnessed the pandemic, epidemic diseases exert a strong impact on human beings and ecosystems. Since the Sun is the primary energy source of the Earth, some scientific pioneers attempted to search for the discernible relation between solar activity and the incidence of epidemics. In this study, the periodic changes and trends of ancient Chinese epidemic data were analyzed in comparison with those of sunspot numbers, a solar activity proxy. The results show that the epidemic and solar activity changes are in good agreement to a certain extent, especially during the Gleissberg and the de Vries cycles. The wavelet coherence shows that the frequency of the epidemic data and sunspot numbers are highly associated. In addition, results from the ensemble empirical mode decomposition illustrate consistent variations in low-frequency decompositions. This study has important implications for further understanding of the potential impact of solar activity on Earth's biosphere, the underlying mechanism of which needs further exploration. [ABSTRACT FROM AUTHOR]

The distribution development of oak has significant effects on ecosystems and society. Long-term forest distribution studies can help to better understand the vegetation dynamics under climate change or human activities in the future. In this study, we integrated different methods (i.e., palaeoecology, phylogeography, and species distribution models) to investigate the likely locations of glacial refugia and the postglacial development of the main deciduous oak species (i.e., Quercus variabilis, Q. mongolica, Q. dentata, Q. aliena, Q. acutissima and Q. liaotungensis). The results indicated that mountains such as the Changbai, Qinling, and Dabie Mountains acted as the refugia in northern and central China during the Last Glacial Maximum (LGM). The present Quercus in northern China could be the result of local dispersal during the postglacial period rather than only that of long-distance migration from south to north. Climate was the main influencing factor for oak migration, while human activities did not show much influence on this widespread genus. The topography acted as a buffer and made the mountains to act as refugia under a deteriorated climate. Compared with other main tree genera (e.g., Pinus and Betula), the refugia locations and migration routes of deciduous oak species were different because of their physiological differences. The individual migration dynamics of these three genera need to be considered when modelling their dynamics. [ABSTRACT FROM AUTHOR]

Reconstructing historical land use and land cover change using explicit temporal, quantitative, and spatial information is not only the prerequisite for simulating long-term climate change and ecological effects but is also a scientific basis for comprehensively understanding the process and mechanism of anthropogenic land use alterations. Considering changes in historical borders and administrative divisions, a provincial cropland area dataset for China over the past millennium was created on the basis of existing estimations since the Song Dynasty. Land suitability for cultivation was then assessed by incorporating altitude, slope, soil texture, and the maximum potential productivity of climate. Subsequently, a gridding allocation model for cropland was constructed, and the provincial cropland area for 24 years over the past millennium was allocated into grids with a resolution of 10 km. The cropland area in China increased from 3.71×107 ha in AD 1000 to 12.92×107 ha in AD 1999, with a peak of 13.50×107 ha in AD 1980. The total cropland area in China showed fluctuating increasing trends that can be divided into three phases: fluctuation without notable net change for AD 1000–1290, slow increase for AD 1290–1661, and rapid increase for AD 1661–1999. Spatially, cropland intensified in the middle-lower reaches of the Yellow and Yangtze Rivers and expanded to mountainous and frontier areas over the last millennium. Specifically, over the entire period, the fractional cropland areas (FCAs) in the middle-lower reaches of the Yellow and Yangtze Rivers increased by 1.4 and 0.8 times, respectively. Since the mid-Qing Dynasty, large-scale land reclamation expanded to areas of low reclamation in southwest and northeast China. The FCAs for southwest and northeast China increased from 2.13% and 0.55% in AD 1661 to 18.00% and 26.61% in AD 1999, respectively. For AD 1661–1999, the proportion of cropland increased by 55% in the hills and low mountains and 27% in the middle and high mountains. The comparison with remote sensing cropland data shows that the grid cells with absolute differences of 0–10% accounted for 70.35% of all grid cells, while grids with differences exceeding 60% accounted for only 0.83%. This finding indicates that the reconstruction method is feasible, and the reconstruction results objectively reveal the historical spatiotemporal changes in cropland. [ABSTRACT FROM AUTHOR]

The rainfall changes in East Asian summer monsoon (EASM) regions on the orbital timescale remain controversial due to the lack of reliable rainfall records. Here, we present new multiproxy records (δ18O, δ13C, Sr/Ca and Mg/Ca) of a 230Th-dated stalagmite from Hulu Cave in central eastern China. Multiproxy records reconstruct a regional hydroclimate history from 340 to 261 kyr BP (thousand years before present), approximately covering the antepenultimate glacial period. The δ18O record is dominated by the precessional cycles, suggesting that EASM responds to changes in Northern Hemisphere summer insolation (NHSI) on the orbital timescale. Significant correlations amongst the δ13C, Sr/Ca and Mg/Ca suggest that a common factor, i.e., the local hydrological cycle, controlled their variability, and their leading principal component can be used as a proxy linked to regional rainfall. This composite record bears a good similarity to those from the Chinese Loess Plateau, showing a gradually decreasing rainfall during the antepenultimate glacial period, consistent with changes in global ice volume. Superimposed on the long-term trend, three relative wetter intervals were responding to the higher NHSI periods, suggesting that EASM rainfall variability was induced by integrated effects of global ice volume and NHSI. The increased ice sheets and lower NHSI resulted in an increased meridional temperature gradient and southward shift of the westerlies, which shortened the duration of Meiyu and midsummer rainfall. The differences between the rainfall record and the stalagmite δ18O record indicate that the latter represents the overall EASM intensity linked to monsoon circulation, but does not directly reflect the rainfall changes at the cave sites. [ABSTRACT FROM AUTHOR]

Maturity evaluation of highly evolved organic matter is an important problem in oil and gas geochemistry, because conventional organic geochemical proxies are not applicable due to hydrocarbon generation and expulsion. In this study, we investigated the pyrobitumen in the reservoirs of the Sinian Dengying Formation in the Sichuan Basin, China. We focused on aromatic hydrocarbon biomarkers, and the calibration and application of aromatic maturity proxies using pyrobitumen reflectance and Raman spectral parameters. Our results show that only the thiophene compounds are effective maturity indicators, such as MDR (4-/1-MDBT), MDR′ (4-MDBT/(1-MDBT+4-MDBT)), MDR1 (1-MDBT/DBT), 4,6-/(1,4+1,6)-DMDBT, (2,6 +3,6)-/(1,4+1,6)-DMDBT, and [2,1]BNT/([2,1]BNT+[1,2]BNT), as these are largely independent of the optical anisotropy of pyrobitumen The condensation and incorporation of thiophene compounds can lead to an increase in the reflectance of pyrobitumen, which means the thiophene compound parameters are positively or negatively correlated with pyrobitumen reflectance New potential maturity parameters were proposed, including DMDBTs/MDBTs, TeMDBTs/(DBT+MDBTs +DMDBTs+TMDBTs+TeMDBTs), 1-MDBT/MDBTs, and [2,1]BNT/BNTs. This method and these parameters are universally applicable to maturity characterization, especially in rocks that lack vitrinite, contain strongly anisotropic organic matter, and have high contents of thiophene compounds. [ABSTRACT FROM AUTHOR]