Search

In this paper, grain‐size records of 128 surface samples and six sediment cores retrieved from freshwater marshes across the Sanjiang Plain were employed to reconstruct the marshes' hydrological variation during the Holocene and to discuss its links to the East Asian summer monsoon (EASM) variation. The grain‐size hydrological significance for the marshes' deposits was first interpreted by quantitative analyses of 128 modern samples. The results indicate that the sand fraction exhibits a higher level significance to modern water‐level conditions than other grain‐size parameters. Thus, the sand accumulation rates of the six cores were calculated and employed to reconstruct the Holocene hydrological regime of the marshes on the plain. Based on the cluster analysis, it can be identified that three higher water‐level stages occurred during 6.2–5.6 thousand yr BP, 5.6–4.5 thousand yr BP, and 2.8–2.4 thousand yr BP, whereas four lower water‐level stages occurred during ~8.0–6.2 thousand yr BP, 4.5–2.8 thousand yr BP, 2.4–0.7 thousand yr BP, and 0.7–0 thousand yr BP, respectively. Considering the prevalent monsoon climate on the modern Sanjiang Plain, it is reasonable to believe that the local water‐level fluctuations were mainly regulated by the EASM variation rather than local factors including flooding, waterway modification, depression infilling, and human activities. The higher water‐level stages were linked to a stronger EASM and vice versa. This study provides essential background datasets for understanding the potential controls on the marsh development and degradation on the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand-palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO2, Al2O3, and Na2O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm-wet and cold-dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial-scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial-scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The goal of this research study is to describe academic issues which have been debated in the field of Chinese geosciences for a century. In 1922, Jonquei S. Lee (Li Siguang) discovered Quaternary glacial relics at Taihang Mountainin eastern China. In 1947, he published his research findings in the magazine Mount Lushan in Glacial Age. The research results had established three Ice Ages: Poyang (Gonzi), Dagu (Minde), and Lushan (Lisi). However, at that time, no Wurm glacial relics of the last Ice Age had been found in Lushan Mountain. Since then, the research team represented by Shi Yafeng, who is considered to be "the father of glaciers in China", questioned Jonquei S. Lee's research results and concluded that "Professor Jonquei S. Lee's Quaternary glacier research in Lushan Mountain having misread the debris flow". In 2005, the "middle‐low mountains" in eastern China were finally defined as follows: "We clearly and unambiguously believe that there were no glacial activities in the middle‐low mountainous areas of eastern China (east of 102° to 104°E; below 3,000 and 2,500 m) during the Quaternary Period". Currently, the long‐standing academic debate appears to have come to a conclusion. As of 2015, the author and others began to investigate and study the Quaternary glacial relics in Mengshan Mountain (1,156m above sea level), Shandong Province, one of the "middle‐low mountains" of eastern China. The relics have been observed to posses the systematic features of glacial erosion, trough and valley striations, and moraine deposits. The applied dating method shave confirmed that there were not only glacial relics of the last Ice Age (Wurm), but also Holocene glacial relics in the Mengshan Mountain area. Therefore, in order to further establish the corresponding relationship between the glacier, loess, stream sediment series, and MIS in the Mengshan Mountain area, a large number of chronological studies have been carried out regarding the various types of sediments in the area, and 24 dating datahave been obtained using OSL, CRN, and 14Cmethods. On this basis, the corresponding relationship between the sedimentary sequences and the MIS was established for the first time in eastern China, which in dicates the environmental changes which had occurred in eastern China since 80ka. These discoveries s and chronological study results confirm the existence of the Last Ice Age, as well as Holocene glacial relics at Mengshan Mountain, there by confirming that Quaternary glaciation had occurred in the middle‐low mountain areas of eastern China. [ABSTRACT FROM AUTHOR]

The Hangjiahu Plain in the lower Yangtze is one of the core areas that sustained the flourishment of the Liangzhu Civilization. This study reconstructed Holocene environmental change on the Hangjiahu Plain based on a sediment core collected from the Tangqi ZK‐3 location situated on the low‐lying Hangzhou‐Taihu region of the Yangtze Delta. We applied OSL dating, grain size analysis, pollen analysis, and magnetic susceptibility to reconstruct Holocene environmental change and compared our data with other published results. Our results showed that (i) before ~7.0 ka B.P., the ZK‐3 core recorded a strong hydrodynamic force, resulting in the widespread deposition of light grayish silt clay or clayey silt in the region. The climate was warm and humid, and the vegetation was mixed evergreen deciduous coniferous forest. (ii) Between 7.0 and 6.0 ka B.P., the hydrodynamic condition in ZK‐3 core became weaker, and the climate remained warm and humid. Although most of the Hangjiahu Plain were still covered by the light grayish silt clay or clayey silt, some higher grounds began to emerge as sea‐level rise slowed, which coincided with the development of the Majiabang culture. (iii) Between 6.0 and 4.5 ka B.P., the deposition of yellowish silty clay indicates a shallow‐water hydrological environment at ZK‐3, as the regional water level was dropping while more land was emerging, which provided a favorable physical environment for the prosperity of the Songze and Liangzhu cultures. The period experienced a drier and cooler climate, with evidence of deforestation. (iv) Between 4.5 and 3.0 ka B.P., the sediments in the ZK‐3 core were dominated by light grayish clay, indicative of a return to a deep‐water environment with a prolonged waterlogging condition. The climate remained dry and cool with further deforestation. However, the widely distributed yellowish silt clay suggests frequent floods in the region, resulting in a sharp reduction of settlement sites and the eventual decline of the Liangzhu Civilization. [ABSTRACT FROM AUTHOR]

Archaeologists frequently invoke climate change as a driving cause for ancient expansions of human populations, but geomorphic changes can also play an important role in opening or closing routes of migration. In China, archaeological evidence demonstrates that valleys in the Jialing River's watershed were important routes for the movement of Neolithic populations from the catchments of the Yellow River to the Yangtze River. Here, we examine how fluvial geomorphological regime shifts may have also influenced the migration pathways and adaptive strategies of Neolithic people into the Sichuan Basin by using a combination of sedimentological and palynological analysis at Luojiaba, an archaeological site located on one of the eastern tributaries of the Jialing River. The results show that people settled on seasonally stable landforms, including the Zhonghe River floodplain at Luojiaba (5300–4800 cal. B.P.). They carried out fishing and hunting activities on the front edge of the floodplain close to the river channel and built dwelling features on the higher ground at the back edge of the floodplain, which was not affected by seasonal floods. We hypothesize that during the Holocene Climatic Optimum before 5500 cal. B.P., high water levels as well as severe surface erosion caused by a strong East Asian Summer Monsoon (EASM) blocked pathways into the upper reaches of the Jialing River watershed. Only after a series of cold, dry climate events driven by a decrease in EASM intensity ca. 5500–5000 cal. B.P. did water levels recede significantly. This allowed alluvial aggradation to occur, which created floodplains and terraces along the valley that may have opened a new route for the migration into the Sichuan Basin. Our results reveal the human–environment dynamics surrounding Luojiaba in the uplands of southwestern China and highlight the impact of coupled climatic‐geomorphic regime shifts on human settlement and subsistence strategies, across both space and time. [ABSTRACT FROM AUTHOR]

Wildfire activity is an important activity in evolution of vegetation and carbon cycling. Whether wet weather will suppress wildfire or promote them by increasing fuel reserves during the Holocene is not clear. We obtained a record of black carbon from a sediment core spanning the last 14.8 kyr from Gonghai Lake, in North China. There is a close relationship between the timing of wildfire activity and vegetation development driven by the East Asian summer monsoon intensity. On a millennial timescales, wet climatic conditions provide a sufficient biofuels reserve, in the same period wildfire increase; thus, the regional potential biofuels reserve is shown to be an important controlling of regional wildfire activity in the monsoon region of China, under natural conditions. We infer that with the strengthening of Asian summer monsoon caused by global warming, the wildfire carbon emission in Asian monsoon region may increase in the future. Plain Language Summary: Much attention has been paid to the response of wildfire activity to climate change. Understanding the past history of wildfires and their triggering factors may help us to mitigate the effects of future wildfires. Our study of the black carbon record of the sediments from an alpine lake (Gonghai Lake) in North China indicates that the level of biofuels (mainly woody vegetation) was the main control on the intensity of wildfire on a millennial timescales over the past ∼14,800 yr. When the climate was wetter, more biofuels were available as a result of increased biomass storage, wildfires were more intense with a relatively stable ignition probability. So, climate trends that favor vegetation development will lead to a higher intensity of wildfire and carbon emission in the Asian monsoon region in the future, with the strengthening of Asian summer monsoon caused by global warming. Key Points: The variation of wildfire and summer monsoon is consistent on the millennial scale, wet climate drives wildfire enhancingBiofuels reserve has controlled wildfire for the Holocene in Asian summer monsoon regionStronger monsoons caused by global warming would increase wildfire carbon emission [ABSTRACT FROM AUTHOR]

The integrated effects of ocean‐atmosphere dynamics on the temperature evolution in the western North Pacific marginal seas have remained elusive. In order to study mechanisms controlling southern Yellow Sea (YS) temperature changes, bottom water temperature (BWT) changes were reconstructed for the last 8.8 kyr by using the TEXL86 index, which archives temperature signal of the winter season Yellow Sea Warm Current. Our results reveal a series of abrupt multi‐centennial to millennial scale BWT changes (∼1°C), superimposed on a gradual long‐term cooling (>3°C) trend starting from ∼5 ka to the present. The YS BWT changes are positively correlated with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). The Western Pacific Warm Pool subsurface water cooling signal was most likely transmitted by the Kuroshio Current into the southern YS, highlighting the role of WPWP in influencing thermodynamics of the extratropical regions during the Holocene. Plain Language Summary: The Yellow Sea (YS) is a semi‐closed marginal sea located in the northwestern Pacific Ocean. During the winter season, the Yellow Sea Warm Current (YSWC) is driven by northwesterly winds, flowing into the southern YS along the west flank of the central trough. The YSWC, a continuation of the Kuroshio Current, brings warm equatorial Pacific water into the YS, leading to milder winters in the surrounding coastal cities compared with other cities on the same latitude in China. The YSWC is sensitive to changes in ocean‐atmosphere dynamics. However, its evolution during the Holocene is not well understood. We reconstruct the winter season temperature changes of the YSWC during the last 8.8 kyr. We found warm temperatures during the mid‐Holocene (8.8‐5 ka) and a gradual cooling trend over the last 5 kyr, which coincides with subsurface water temperature changes in the Western Pacific Warm Pool (WPWP). We suggest that the tropical subsurface water temperature changes of the WPWP are most likely transmitted via the Kuroshio Current into the YS. Our results shed new light on our understanding of the role played by the WPWP water masses in regulating subtropical ocean dynamics and climate during the mid‐to‐late Holocene. Key Points: The temperature evolution of the winter season Yellow Sea Warm Current was reconstructed over the past 8.8 kyrAbrupt multi‐centennial to millennial scale changes are superimposed on a gradual cooling trend starting from ∼5 ka to the presentWestern Pacific Warm Pool subsurface water cooling signal was transmitted by the Kuroshio Current into the southern Yellow Sea [ABSTRACT FROM AUTHOR]

The Gas Hure Salt Lake (GHSL) in the northwestern Qaidam Basin, western China, is rich in boron (B) resources, but its B‐resource origin is hardly known. Hydrochemical compositions and B isotope characteristics of different waters were collected around the GHSL, including the river water, stream water, spring water, salt‐lake brine, intercrystalline brine, well water, drilling brine, and solar pond brine. The hydrochemical signatures suggest that silicates, carbonates and evaporates are the main B‐bearing rocks during the water dynamic. The reservoir estimation of B resources shows that the Kulamulekesay River (KLMR) and the Atekan River (ATKR) contribute annually 18.3 tons and 22.84 tons of B, respectively, with a total amount of 11.72 × 104 tons of B during the past 5.7 ka. In comparison with the known B reservoir (32.96 × 104 tons) in the GHSL, a significant amount of B in the GHSL was probably recharged from deep fluids and sediments around the GHSL. The B concentration and B‐enrichment degree are shaped by the evaporation process, which are highly elevated at the carnallite and bischofite stages. [ABSTRACT FROM AUTHOR]

Here we present, to date, the highest‐resolved (~5 years) and most precisely dated Holocene monsoon climate reconstruction for the western Chinese Loess Plateau based on five replicated stalagmite δ18O records from Wuya Cave, eastern Gansu, China. Our record suggests the wettest period occurred between 10,500 and 6,600 a BP in this region. After this period, the amplitude of Asian summer monsoon decadal‐scale variability progressively increased likely in response to increasing ENSO frequency since the middle Holocene. Our study reveals similar asymmetric centennial‐scale double‐plunging structures of the 8.2, 5.5, and 2.8 ka events in the western Chinese Loess Plateau, suggesting a possible role of solar activity whose impact was amplified around 8.2 ka BP by the meltwater flood. In contrast, the 4.2 ka event exhibit gradually declining monsoon rainfall with centennial‐ to decadal‐scale fluctuations. Key Points: A 5 year‐resolved Holocene Asian summer monsoon record was reconstructed for the western Loess Plateau based on speleothemsThe wettest period occurred between 10,500 and 6,600 a BP, after that, the amplitude of decadal‐scale monsoon variability increasedSimilar structures were observed during the 8.2, 5.5, and 2.8 ka weak monsoon events, which are different from the 4.2 ka event [ABSTRACT FROM AUTHOR]

Research on abrupt paleoclimatic and paleoenvironmental change provides a scientific basis for evaluating future climate. Because of spatial variability in monsoonal rainfall, our knowledge about climate change during the mid‐ to late‐Holocene in southern China is still limited. We present a multi‐proxy record of paleoclimatic change in a crater lake, Lake Shuangchi. Based on the age‐depth model from 210Pb, 137Cs and AMS14C data, high‐resolution mid‐ to late‐ Holocene climatic and environmental records were reconstructed using multiple indices (TOC, TN, C/N, δ13C and grain size). Shuangchi underwent a marked change from a peat bog to a lake around 1.4 kaBP. The C3 plants likely dominated during 7.0–5.9 ka and 2.5–1.4 kaBP, while C4 plants dominated between 5.9–3.2 and 3.0–2.5 kaBP. Algae were dominant sources of organic matter in the lake sediments after 1.4 kaBP. Several intervals with high concentrations of coarser grain sizes might be due to flood events. These results reveal that several abrupt paleoclimatic events occurred around 6.6 ka, 6.1 ka, 5.9 ka, 3.0 ka, 2.5 ka and 1.4 kaBP. The paleoclimatic change recorded in the lake may be related to the migration of the Intertropical Convergence Zone (ITCZ) and El Niño ‐ Southern Oscillation (ENSO) activity. [ABSTRACT FROM AUTHOR]

Studies of the vegetation response to abrupt climatic events may provide valuable insights into assessing the impacts of such events under future global warming scenarios. Here we present a detailed record of regional vegetation change based on high‐resolution pollen records for the intervals 9000–7000 and 5000–3000 cal a bp from the Hulun Lake region of north‐eastern China. Our aims were to determine the regional expression of the 8.2‐ and 4.2‐ka events in north‐eastern China, especially their effects on vegetation composition. The results show that the response of the vegetation of the Hulun Lake region to the climatic cooling of the 8.2‐ka event was relatively minor; however, the 4.2‐ka event, which resulted in climatic aridification, resulted in pronounced vegetation degradation. We suggest that the specific characteristics of the 8.2‐ and 4.2‐ka events, together with their duration and the regional climatic background on an orbital time scale, were the main factors responsible for the contrasting vegetation responses. The strengthening and northward shift of the Intertropical Convergence Zone (ITCZ) tended to offset the cooling effect of the 8.2‐ka event on regional vegetation in the mid–high latitudes of East Asia; in contrast, the decrease in summer insolation in the Northern Hemisphere and the southward shift of the ITCZ may have intensified the drought effect of the 4.2‐ka event in East Asia and the associated vegetation degradation. Under future global warming scenarios, both extreme cooling events and extreme drought events may cause a deterioration of the ecological environment; however, the resulting regional vegetation responses may be substantially different. [ABSTRACT FROM AUTHOR]

The northeastern Qinghai‐Tibetan Plateau (QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significance for recognizing the spatial‐temporal pattern of Asian monsoons in the past and predicting environmental change in the future. Nevertheless, the framework of the Holocene moisture variation and related mechanisms remain controversial, owing to complex hydroclimatic conditions triggered by the landform of the large mountain‐arid basin. Here, we employed geochemical proxies from typical aeolian sand‐palaeosol sequences in the Gonghe Basin, northeastern QTP, together with Optically Stimulated Luminescence (OSL) dating, to reconstruct the pattern of effective moisture variation and associated mechanisms in this region. Our results indicate that the regional effective moisture was at its lowest until 9–8 ka, and approached a maximum during 8–4/3 ka of the middle Holocene. Afterwards, the climate became relatively dry in general, but with a transient humid interval around 2–1 ka. Our geochemical evidence indicates that the dry early Holocene probably can be attributed to a strong winter monsoon forced by remnant ice sheet, combined with the high evaporation caused by solar insolation. Also, shifts of humid‐dry are closely linked to the Asian summer monsoonal strength and therefore the balance of evaporation‐precipitation in the middle and late Holocene. Thus, the pattern of the Holocene effective moisture variation is characterized as the 'monsoon model' in a closed intermontane arid and semi‐arid basin near the western Asian monsoonal limit. [ABSTRACT FROM AUTHOR]

We report a new high‐resolution Holocene 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China, aimed to detect the atmospheric 10Be production signal in low‐latitude regions. After minimizing climatic effects by regression analyses between 10Be concentration and climatic proxies from the same archive, we successfully distinguished variations in geomagnetic field intensity and solar activity using 2,000‐year low‐ and high‐pass filtering, respectively, of the residual 10Be record (a proxy of the atmospheric 10Be production rate). The resulting 10Be‐derived record of geomagnetic field intensity is generally comparable with geomagnetic models, and the solar‐modulated 10Be signal shows significant correlations with solar activity proxies. The preservation of 10Be production signal in the sediments of this low‐latitude maar lake highlights the largely unexplored potential as well as limitations of 10Be as a tool to reconstruct variations in solar activity and geomagnetic field intensity. Plain Language Summary: The atmospheric production rate of cosmogenic 10Be depends on the cosmic ray flux penetrating the atmosphere, a process that is mainly controlled by the geomagnetic field strength and solar activity. The geomagnetic imprint on 10Be has been well established in previous studies of ice cores and marine sediments. The relationship between solar activity and 10Be has also been studied in ice cores and high‐latitude lakes. Here we for the first time present a high‐resolution 10Be record from Huguangyan Maar Lake in subtropical‐tropical South China over the Holocene. We successfully separated the atmospheric 10Be production signal from climatic effects that contribute to up to ~52% of the variance in 10Be concentration. After eliminating the climatic effects, variations in both geomagnetic field intensity and solar activity signals were reconstructed from the residual 10Be record, using 2,000‐year low pass, and high‐pass filtering, respectively. The geomagnetic‐ and solar‐modulated 10Be production signals are evaluated by comparisons with independent records. This result unambiguously indicates that the 10Be‐derived solar activity signal at a low‐latitude subtropical site can be obtained, even when the 10Be signal is dominated by regional climate, in our case, accounting for up to ~65% of the variance in the record during the early‐middle Holocene. Key Points: We for the first time report on a multidecadal to centennial‐scale 10Be record throughout the Holocene in subtropical‐tropical South ChinaWe separated atmospheric 10Be production signal from regional environmental effects that account for ~52% of variance in 10Be concentrationGeomagnetic‐ and solar‐derived 10Be signals were reconstructed by 2,000‐year low‐ and high‐pass filtering, respectively, of the residual record [ABSTRACT FROM AUTHOR]