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The hydrology of western Central Asia is highly sensitive to climatic perturbations. In order to understand its long-term variability and to infer linkages between precipitation and atmospheric and oceanic systems, we conducted a thorough sedimentary and geochemical study on a composite core retrieved in lake Son Kul (central Kyrgyzstan). A multi-proxy approach was conducted on lake sediments based on grain size analyses, magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN) and carbon and oxygen isotope analyses on bulk and biogenic materials (ostracoda and molluscs shells) at a resolution equivalent to ca 40 years, aiming to characterise the sequence of palaeolimnological changes in Son Kul. As indicated by δ 18 O record of bulk carbonates, mainly consisting of aragonite, the Holocene hydrological balance was negative during most of time, suggesting an excess of evaporation (E) over precipitation (P). Limnological conditions fluctuated rapidly before 5000 cal yr BP indicating significant changes in regional hydrology and climate. In particular, the long-term negative hydrological balance was impeded by several short stages with marked increase of precipitation, lasting several decades to a few centuries (e.g., 8300–8200, 6900–6700, 6300–6100, 5500–5400, 5300–5200 and 3100–3000 cal yr BP). Precipitation changes as inferred from δ 18 O data are also documented by increased minerogenic detritus and higher TOC. We propose that the seasonal pattern of precipitation varied transiently in western Central Asia during the Holocene, although evaporation changes may also account for the rapid changes observed in δ 18 O data. When the annual water balance was less critical (P ≤ E), the excess of water might be ascribed to increased precipitation during cold seasons mainly because winter precipitation has more negative δ 18 O than its summer equivalent. Conversely, when the annual water balance is negative (P ≪ E), the moisture was mainly delivered during the warm season, as between 5000 and 2000 cal yr BP. Our results thus imply that moisture sources could have changed as well during the Holocene. Moisture was delivered as today mainly during summer from the extended Caspian-Aral Basin and eastern Mediterranean, although Arctic and even North Atlantic seas might be important moisture sources when seasonal precipitation was dominated by winter precipitation. We hypothesise that warming Arctic and North Atlantic seas were important for the North Hemisphere circulation during the cold season. [ABSTRACT FROM AUTHOR]

Abstract: We investigated mineral aerosol (dust) deposition in the Aral Sea with intention to understand the variability of dust in central Asia and its implications for atmospheric circulation change in the late Holocene. Using an 11.12-m sediment core of the lake, we calculated bulk sediment fluxes at high time-resolution and analyzed grain-size distributions of detrital sediments. A refined age-depth model was established by combined methods of radiocarbon dating and archeological evidence. Besides, a principal component analysis (PCA) of grain-size fractions and elements (Fe, Ti, K, Ca, Sr) was used to assess the potential processes controlling detrital inputs. The results suggest that two processes are mainly relevant for the clastic input as the medium silt fractions and Ti, Fe and K are positively correlated with Component 1 (C1), and the fine size fractions (<6 μm) are positively correlated with Component 2 (C2). Taking the results of the PCA, geological backgrounds, clastic input processes into account, we propose that the medium silt fractions and, in particular, the grain-size fraction ratio (6–32 μm/2–6 μm), can serve as indicators of the variability of airborne dust in the Aral Sea region. On the contrary, the fine size fractions appear to be contributed mainly by the sheetwash processes. The bulk sediment deposition fluxes were extremely high during the Little Ice Age (LIA; AD 1400–1780), which may be related to the increased dust deposition. As indicated by the variations of grain-size ratio and Ti, the history of dust deposition in central Asia can be divided into five distinct periods, with a remarkably low deposition during AD 1–350, a moderately high value from AD 350–720, a return to relatively low level between AD 720 and AD 1400 (including the Medieval Warm Period (MWP, AD 755–1070)), an exceptionally high deposition from AD 1400 to 1940s and an abnormally low value since 1940s. The temporal variations in the dust deposition are consistent with the changes in the Siberian High (SH) and mean atmospheric temperature of the northern hemisphere during the past 2000 years, with low/high annual temperature anomalies corresponding to high/low dust supplies in the Aral Sea sediments, respectively. The variations in the fine size fraction also show a broadly similarity to a lacustrine δ18O record in Turkey (), implying that there was less moisture entering western central Asia from the Mediterranean during the LIA than during the MWP. [Copyright &y& Elsevier]

The present study conducted a comprehensive study on the distribution and source of heavy metals (Cu, Zn, Ni, Pb, Cd) in the sediments of the coastal East China Sea (ECS), one of the most developed regions in China with very active land-sea interactions, using 119 surface sediment samples and a 2-m sediment core collected after super Typhoon Chan-hom in 2015. Heavy metals in the surface sediments exhibited metal-dependent and regional distribution patterns, showing higher levels in the southern inner shelf (SIS) than the Yangtze River estuary (YRE), and generally being evaluated as unpolluted to moderately polluted in the coastal ECS (except few sites adjacent to Xiangshan Harbor were strongly polluted by Cd). Based on the organic carbon isotope compositions (δ13C) data as well as the strong correlations between heavy metals and natural major elemental contents (Al 2 O 3 , Fe 2 O 3 , and SiO 2), we suggest natural weathering detritus as the major source of heavy metals in the YRE region and the spatial distributions were highly controlled by sediment grain size and organic matter. In contrast, the spatial distributions of heavy metals in the SIS region were less correlated with sediment properties, due to more complex sources and stronger hydrodynamic impacts. The vertical distribution of heavy metals in the sediment core indicated significant enrichments since 1950s, but showed unusual gradually decreasing trends in top layer (30 cm–0.5 cm), attributing to the strong disturbance of super Typhoon Chan-hom on sediment transportation and metal partitioning. Besides, we also observed that heavy metal levels in shallow water regions of Zhejiang coast were reduced due to the passage of typhoon. Such strong impacts of super Typhoon Chan-hom on heavy metal distributions in the ECS indicates that the impacts of extreme hydrodynamic events should raise more concern when assessing the distribution and potential risks of contaminants in coastal regions. Image 1 • Natural terrestrial detritus is the major source of heavy metals in the YRE. • Cd and Cu pollution near Xiangshan Harbor should raise special attention. • Sediment grain size and organic matter controlled metal distributions in the YRE. • Metal distributions in the SIS region are impacted by complex anthropogenic inputs. • Typhoon Chan-hom reduced metals in top layer sediments in shallow water region. A comprehensive study on the distribution and source of heavy metals in the ECS, under complex geochemical and hydrodynamic (include typhoon) impacts. [ABSTRACT FROM AUTHOR]

• Climate controlled wildfires in the Changjiang River Basin before the mid-Holocene. • Enhancing human activities induced the fire regime shift since ∼ 5 ka. • Farming and bronze smelting promoted natural landscape changes by fire use. Deforestation and technical innovation have changed the natural fire regimes, topography and carbon reservoirs during the history of human evolution. Recognition of the timing, scope, and magnitude of wildfire events in large river basins such as the Changjiang (Yangtze River) is essential for understanding the impacts of climate forcing and human perturbation on Earth surface processes. Here, we present a multi-proxy study based on the pollen and black carbon (BC) abundance in sediments of Core CM97 taken from the Changjiang Delta, aiming to reconstruct the paleo-fire history in the Changjiang River Basin and further disentangle anthropogenic and climatic influences on fire regimes during the Holocene. Our results show that the average BC abundance increased from 0.88 ‰ at 12–8 cal kyr BP to 1.17 ‰ at 8–5 cal kyr BP, well corresponding to the evolution of the Asian Summer Monsoon (ASM). This suggests the wildfire occurrences were dominated by hydroclimatic conditions during 12–5 cal kyr BP. After the early Bronze Age (∼5 cal kyr BP), the sustained high anomaly of BC abundance (average 1.30 ‰), however, was decoupled from the weakened monsoon climate. We propose that this might be associated with anthropogenic destruction of natural forests through fire-assisted agriculture and bronze smelting. Especially, with the prosperity of the Han Dynasty (202 BCE − 220 CE), a rapid increase in population promoted the transition of ecosystem (vegetation type) from forests to permanent farmlands in the drainage basin. Human intervention has overwhelmed the long-term climate control over wildfire, plant diversity, soil erosion, and sediment source-to-sink processes, suggesting the dominance of anthropogenic activities on nature over the last 2 kyrs. Our study provides deep insight on the enhancing perturbation of human activities on Earth's surface at a continental scale and provides more constraints on the Anthropocene epoch. [ABSTRACT FROM AUTHOR]

The terrigenous sediment source-to-sink processes in continental margins are determined by complex interactions among climate, sediment discharge, sea level and oceanic circulations on various temporal and spatial scales. The northeastern South China Sea (NSCS) margin is a natural laboratory to catch a glimpse of these processes due to large amounts of terrigenous sediment inputs and continuous sedimentations during the late Quaternary. Based on a 35 m-long sedimentary sequence (core MD12-3429) retrieved from the NSCS upper continental slope, we distinguished sediment sources based on geochemical compositions, and then linked sedimentary responses to sea level change and Kuroshio intrusion over the past 244 kyrs via various sedimentary records including mass accumulation rates (MAR), foraminifera data, grain-size end-member modeling (EMM) and spectral analysis. Geochemical proxies including major element ratios and fractionation parameters of rare earth elements suggest that the detrital sediment in the core was derived primarily from the Taiwan. The MAR of terrigenous sediment yields an average 9.6 g/cm2/kyr, and high MAR values are both observed in glacial and interglacial intervals. The results of EMM reveal three end-members with dominant modal grain sizes of 6.6 μm (EM1), 26.3 μm (EM2) and 49 μm (EM3), respectively. The temporal variations of the finest end-member (EM1) and the coarsest end-member (EM3) demonstrate clearly glacial-interglacial cyclicity, and the spectral analysis indicates the dominance of 100-kyr eccentricity, which suggests that sea level changes are the first-order control for the NSCS continental margin sedimentation. In addition, the temporal variations in hydrodynamic sensitive component (EM2) and its MAR display gradually increasing trends with weakening East Asian monsoon. Combing with modern observation and modeling results, we suggest that enhanced Kuroshio intrusion might account for the transport of Taiwan-derived sediment during the late Quaternary. As indicated by a 31 kyr periodicity in EM2, we infer that the development of El Niño-like condition strengthened the intrusion of oligotrophic Kuroshio from the Luzon Strait, resulting in the obvious increase of Taiwan terrigenous MAR but decreases of the primary productivity in the northeastern South China Sea. This study provides deep insight into the complex terrigenous sediment source-to-sink processes in a fast-changing marginal sea environment during the late Quaternary. • Sea-level change was the primary control for terrigenous sediment source-to-sink processes in the NSCS since MIS7. • Strengthened intrusion of Kuroshio dominated Taiwan sediments transport. • Kuroshio intrusion and ENSO forcing were coupled on glacial-interglacial scale. • Grain size end-member modeling provides insights into sedimentary response to changes of sea level and oceanic circulation. [ABSTRACT FROM AUTHOR]

Abstract: River bed sediments were collected from the main stream and major tributaries of the Yangtze River for clay mineralogy study. Surface sediments from the Yarlung Zangbo River on the Tibetan Plateau were also examined for comparison. The results show that the clay mineral compositions of the Yangtze River display a similar pattern through the whole truck stream, with illite being dominant, kaolinite and chlorite being lesser abundant, and smectite being minor component. Clay mineralogy shows distinct differences in the tributaries, which correspond to the heterogeneous source rocks and weathering intensity of the drainage. The illite crystallity and the illite chemical weathering index (5Å/10Å peak ratio) both increase downstream, indicating a increasing trend of hydrolysis along the river. It also indicates that the upperstream of the drainage is characterized with physical weathering while the middle- and lower reaches are controlled by chemical weathering process. In accordance with the result derived by the illite indexes, sediment input from upperstream including Yalong Jiang, Dadu He, Min Jiang and Jialing Jiang accounts for the major sediment load, whereas Wu Jiang, Xiang Jiang, Gan Jiang and Dongting Lake provide relatively less sediments. [Copyright &y& Elsevier]

Abstract We have examined the possible use of Mn/Ca ratios in benthic foraminifera as a proxy for hypoxia, which has increasingly become a serious environmental issue in many coastal zones. We collected samples from the Yangtze River Estuary, one of the largest and most intense seasonally hypoxic zones in the world. In order to obtain high quality Mn/Ca data, unaffected by contamination, we examined two different cleaning protocols and instrument-based analysis methods. Our results showed that a relatively simple physical cleaning approach coupled to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) provided excellent results on single specimens. Our observations were comparable to ICP analyses of solutions made up from dozens or even hundreds of specimens and involving complicated sample pretreatments. Using the LA methodology, we analyzed Mn/Ca ratios from living Florilus decorus (F. decorus) specimens from stations in the Yangtze River Estuary with varying bottom water dissolved oxygen (DO) concentrations. Our results showed that Mn/Ca ratios in penultimate chambers of living benthic foraminifera are sensitive to bottom water DO concentrations. We also observed significant variations of both Mn/Ca and Mg/Ca ratios from different chambers within foraminiferal shell specimens. These fluctuations were likely a response to changing ambient water DO and temperature during the specimen's growth history. Combined use of foraminiferal Mn/Ca ratios together with other proxies could provide a powerful tool for historical reconstruction of low oxygen conditions in seasonal hypoxia areas. [ABSTRACT FROM AUTHOR]

Chemical speciation of iron (Fe) in sediment offers a better understanding on iron cycle, early diagenesis, paleoredox condition and paleoclimatic changes. This study reports the Fe chemical speciation (total concentration Fe T , highly reactive Fe HR , poorly reactive Fe PR and unreactive Fe U ) in the surface sediments from the Changjiang (Yangtze River) Estuary and the East China Sea shelf. The Fe HR concentrations in the estuarine and shelf sediments are much lower than those from the Changjiang and other rivers in the world, confirming the previous observations on geochemical fractionation effect in estuarine and shelf sediments. The high correlations of Fe HR with Fe T and Al concentrations and sediment surface area, suggest the dominance of clay minerals on Fe HR composition in the sediments. The apparent enrichments of Fe HR , total organic carbon and surface area in the hypoxia zone off the Changjiang Estuary are primarily caused by the local hydrodynamics and sedimentary processes. Despite the wide application of Fe HR /Fe T ratio for redox condition, its spatial distribution from the Changjiang river mouth to open shelf reveals no obvious enrichment in the hypoxia zone. This suggests that the episodic occurrence of hypoxia off the Changjiang Estuary (mostly in August) is hardly imprinted in particulate iron speciation. The distributions of Fe chemical speciation along the “river-estuary-open shelf” transect suggest the complex controls of particulate iron “shuttle transport” and deposition in the continental margin where fluvial input dominates and intense anthropogenic impact exists. Our study sheds new light on the source-to-sink process of particulate iron in the estuary and open shelf, and also provides important constraints of Fe speciation in modern and ancient archives from various depositional environments. [ABSTRACT FROM AUTHOR]

• River sediments in the eastern and western Fujian have distinct source rock compositions. • Indosinian magmatic rocks predominantly originated from the Proterozoic crust. • Yanshanian magmatic rocks originated from both the DM (Depleted Mantle) and Proterozoic crust. • The middle Zhenghe-Dabu Fault predominantly account for geochemical heterogeneity of river sediments. The Cathaysia Block is featured by intense tectonic activities and magmatic intrusions during the Mesozoic, and its geochemical evolution might greatly imprint the river sediment compositions in southeast China. This paper presents a comprehensive synthesis of data from petrology, U-Pb geochronology, and geochemistry of both river sediments and plutons in Fujian Province, and aims to reveal the constraints of Mesozoic geochemical heterogeneity and geochronology of the Northeast Cathaysia Block on local river sediment geochemistry. The Fujian terrane and relating river systems can be divided into western and eastern parts with the boundary of the Zhenghe-Dabu Fault. The sediments of eastern rivers are characterized by heavy minerals derived from granites and two major U-Pb age groups (90–110 Ma and 120–150 Ma) of detrital zircons. However, the sediments of western rivers are featured by heavy minerals from the Precambrian rocks and have seven zircon U-Pb age groups (from 90 Ma to 3.0 Ga). The Indonesian magmatic rocks predominantly originated from the Proterozoic crust, with less contribution from the depleted mantle, which are much different from the Yanshanian A-type granites and gabbros in the eastern terrane. We infer that the middle part of Zhenghe-Dabu Fault formed in the Jingningian Period primarily caused geochemical and geochronological heterogeneity of the Northeast Cathaysia Block, which further determined the totally different sediment compositions between the western and eastern Fujian rivers. [ABSTRACT FROM AUTHOR]

The Late Triassic was a key period for the evolution of the western Sichuan Basin from marine to continental sedimentation. However, the provenance of the earliest terrigenous sediments during this period remains debated, hindering our understanding of the tectonic events that ruled the evolution of the basin at that time. Herein, samples of fine sandstone from the Upper Triassic Ma'antang and Xiaotangzi formations in the western Sichuan Basin were collected for petrology, heavy mineral analysis, bulk rock geochemistry, and detrital U–Pb dating. In addition, corresponding data from potential source areas were collected for comparison. The sedimentological, geochronological, and geochemical characteristics of terrigenous sediments suggest that the clastic materials were mainly sourced from the Qinling orogenic belt and Yangtze Craton (including the northern and western margin). The Longmen Shan thrust belt likely provided clastics since the Early Norian. Siliciclastic deposits of the Late Triassic sedimentary succession of the western Sichuan Basin (Ma'antang and Xiaotangzi formations) yielded young zircon U–Pb ages of 214–245 Ma, suggesting that these zircons were likely sourced from the magmatic activities in the South Qinling orogenic belt or Yidun Island Arc. Combined with previous research, this study predates the transformation of the western Sichuan Basin from marine to continental sedimentation in the Late Carnian/Early Norian period. • The terrigenous clastics of the western Sichuan Basin first appeared in the Ma'antang during the Late Carian period. • The terrigenous clastics possibly derived from the Qinling Orogenic Belts, Yangtze Craton and its marginal blocks. • Since the deposition of the Xiaotangzi Fm., the Longmenshan thrust belt provided clastics for the Western Sichuan Basin. • The young volcanic zircons (214∼245Ma) were probably sourced from the South Qinling orogenic belt or Yidun Island Arc. [ABSTRACT FROM AUTHOR]

A multiproxy study was conducted on Holocene sediments from the alpine lake Son Kul (3010 m a.s.l, 41°48′33N/75°07′38E) in central Tien Shan (Kyrgyzstan). The combination of high-resolution pollen, palynofacies and magnetic susceptibility data allowed reconstruction of changes in sedimentary and vegetation dynamics regionally at Son Kul between 8350 and ca 2000 cal. BP. Using pollen data to quantify climatic parameters, a quantitative reconstruction of climatic conditions was performed using the “Modern Analogue Vegetation types” (MAV) method and a ranged index of seasonality. The most temperate (e.g. moister) climate conditions occurred between 8350 and 5000–4500 cal. BP when alpine meadow vegetation was enriched in plants requiring moister conditions and trees developed regionally. Conversely, more continental and arid conditions prevailed after 4500 cal. BP with the decline of arboreal vegetation (especially Juniperus) and the extension of an alpine steppe-meadow along with a regional decrease in Poaceae. This climate transition was associated with a change in seasonality as the continentality greatly intensified after 5000–4500 cal. BP. Our results are consistent with other records from the Tien Shan range and the Chinese Province Xinjiang showing that relatively wet conditions prevailed regionally before 5000 cal. BP, whereas reduced moisture conditions were established after that time. From a more global perspective, we highlight that regional rainfall in central Tien Shan and western Central Asia is likely to be predominantly controlled by the Eastern Mediterranean cyclonic system and North Atlantic climate, as based on the close correspondence between climatic archives from western Central Asia, the Levant, the Eastern Mediterranean and Caspian Sea regions. However, the effect of monsoonal dynamics on the regional climatic system in central Tien Shan still remains dubious, since recent modelling studies have shown that no dynamic link exists between humidity in Central Asia and the Indian Summer Monsoon. This study pinpoints the need to explore the effect of remote Eurasian atmospheric circulation patterns on past climate variability in Central Asia. [ABSTRACT FROM AUTHOR]

• Systematic zircon ages from offshore basins of eastern China are firstly reported. • Zircon age spectra of the modern Yangtze River firstly appeared in the late Miocene. • The Yangtze River with present erosion patterns was formed in the late Miocene. The Yangtze River originates in the Tibetan Plateau and supplies tremendous sediments to the East China Sea. To date, when and how the Yangtze River was formed is still highly debated. This paper presents systematic detrital zircon U-Pb ages (3575 grain ages from a total of 29 samples) from the Cenozoic sediments of offshore basins in East China. The zircon age spectra vary significantly in the South Yellow Sea Basin, but are relatively stable in the East China Sea Shelf Basin (ECB) and significantly different from those of present-day Yangtze River (PYR) before the late Miocene. Comparisons of zircon ages with potential source terranes suggest that the ECB has received detrital sediments that PYR features since the late Miocene, whereas before that time, the sediment provenances show a North China and Korea affinity. Considering the overwhelming sediment input from the eastern Tibetan Plateau, the first occurrence of the PYR-featured sediments in the ECB in the late Miocene suggests that the Yangtze River with approximately present erosion patterns was established at that time. This agrees well with the exhumation history of the eastern Tibetan Plateau. The unique zircon ages in the Eocene to mid-Miocene sediments imply that the Yangtze River with headwaters in eastern Tibet might not exist before the late Miocene. This study provides new insights into the Yangtze River evolution although more lines of evidence are required, which is mainly because of the complex river sediment source-to-sink processes and tectonic and climatic forcings in the large catchment. [ABSTRACT FROM AUTHOR]