Reconstruction of paleocoastlines for the northwestern South China Sea since the Last Glacial Maximum

The range of relative sea level rise in the northwestern South China Sea since the Last Glacial Maximum was over 100 m. As a result, lowland regions including the Northeast Vietnam coast, Beibu Gulf, and South China coast experienced an evolution from land to sea. Based on the principle of reconstructing paleogeography and using recent digital elevation model, relative sea level curves, and sediment accumulation data, this paper presents a series of paleogeographic scenarios back to 20 cal. ka BP for the northwestern South China Sea. The scenarios demonstrate the entire process of coastline changes for the area of interest. During the late glacial period from 20 to 15 cal. ka BP, coastline slowly retreated, causing a land loss of only 1×10⁴ km², and thus the land-sea distribution remained nearly unchanged. Later in 15–10 cal. ka BP coastline rapidly retreated and area of land loss was up to 24×10⁴km², causing lowlands around Northeast Vietnam and South China soon to be underwater. Coastline retreat continued quite rapidly during the early Holocene. From 10 to 6 cal. ka BP land area had decreased by 9×10⁴km², and during that process the Qiongzhou Strait completely opened up. Since the mid Holocene, main controls on coastline change are from vertical crustal movements and sedimentation. Transgression was surpassed by regression, resulting in a land accretion of about 10×10⁴km². Supported by Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (Grant No. MSGL0711), the Guangdong Natural Science Foundation (Grant No. 04001309) and Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences (Grant No. MGE2007KG04)     

Occurrence and distribution of hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system,South Korea

We investigated the occurrence and distribution of terrestrial-derived hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers(OH-GDGTs) in the Han River system and their potential impact on the application of the ring index of OH-GDGTs(RI-OH) as a sea surface temperature(SST) proxy in the eastern Yellow Sea. Thereby, we analyzed various samples collected along the Han River and from its surrounding areas(South Korea, n = 34). The OHGDGTs were found in all samples investigated. OH-GDGT-0 was the dominant OH-GDGT component in the estuary and marine samples while OH-GDGT-2 was generally dominant in the soils, the lake sediments and the river suspended particulate matter(SPM). Our results thus suggests a possible warm bias of the RI-OH-derived summer SSTs in the coastal zone to which a large amount of terrestrial organic matter is being supplied. Further studies are necessary to better assess the applicability of the RI-OH proxy in the eastern Yellow Sea.     

Terrestrial and marine biomarker estimates of organic matter sources and distributions in surface sediments from the East China Sea shelf

Revealing of the sources and distributions of sedimentary organic matter in the East China Sea (ECS) is important for understanding its carbon cycle, which has significant temporal and spatial variability due to the influences of recent climate changes and anthropogenic activities. In this study, we report the contents of both terrestrial and marine biomarkers including ∑C₂₇+C₂₉+C₃₁n-alkanes (38.6-580 ng/g), C₃₇ alkenones (5.6-124.6 ng/g), brassicasterol (98-913 ng/g) and dinosterol (125-1521 ng/g) from the surface sediments in the Changjiang River Estuary (CRE) and shelf areas of the ECS. Several indices based on biomarker contents and ratios are calculated to assess the spatial distributions of both terrestrial and marine organic matter in the ECS surface sediments, and these results are compared with organic matter distribution patterns revealed by the δ¹³C (−20.1‰ to −22.7‰) and C/N ratio (5-7.5) of total organic matter. The contents of terrestrial biomarkers in the ECS surface sediments decrease seaward, controlled mostly by Changjiang River (CR) inputs and surface currents; while higher contents of the two marine biomarkers (brassicasterol and dinosterol) occur in upwelling areas outside the CRE and in the Zhejiang-Fujian coastal zone, controlled mostly by marine productivity. Four proxies, f_Terr(δ¹³C) (the fraction of terrestrial organic matter in TOC estimated by TOC δ¹³C), odd-alkanes (∑C₂₇+C₂₉+C₃₁n-alkanes), 1/P_mar-aq ((C₂₃+C₂₅+C₂₉+C₃₁)/(C₂₃+C₂₅) n-alkanes) and TMBR (terrestrial and marine biomarker ratio) (C₂₇+C₂₉₊C₃₁n-alkanes)/((C₂₇+C₂₉+C₃₁) n-alkanes+(brassicasterol+dinosterol+alkenones)), reveal a consistent pattern showing the relative contribution of terrestrial organic matter (TOM) is higher in the CRE and along the Zhejiang-Fujian coastline, controlled mostly by CR inputs and currents, but the TOM contribution decreases seaward, as the influences of the CR discharge decrease.     

Use of aliphatic hydrocarbons to infer terrestrial organic matter in coastal marine sediments off China

Sediment samples from the marine systems along the coast of China, covering Yellow Sea, inner shelf of the East China Sea (ECS) and the South China Sea (SCS), were analyzed for n-alkanes and organic carbon. The concentrations of Σn-C(15-35) were 120-1680ngg(-1) dry weight with an average of 560ngg(-1). Short-chain n-alkanes (C(21)) were mainly derived from terrestrial higher plants. Organic carbon deposited into Yellow Sea and Southeast Hainan within the SCS was mainly of terrestrial (13-110%; mean: 58%) and marine (48-110%; mean: 86%) sources, respectively. On the other hand, organic carbon accumulated in the SCS adjacent to the Pearl River Estuary was derived from both terrestrial and marine sources.     

A model for simulating the response of runoff from the mountainous watersheds of inland river basins in the arid area of northwest China to climatic changes

The subaerial tidal sand area in the northern Jiangsu Province (Subei), stretching from Dongtai towards east with a fan shape, is an early developing stage of radial sand ridges distributed in the South Yellow Sea. Since 5000–6000 a BP, after the Holocene transgression maximum in the northern Jiangsu Province, subaqueous tidal sand bodies were exposed and changed into land gradually. The environmental magnetism analysis shows that subaerial tidal sand strata are formed by the convergent-divergent paleo-tidal current field. The sediment source of tidal sand strata came early from the Changjiang River and late from the Yellow River. Sea floor erosion by tidal currents also served as an important sand source. Drilling cores and ground-penetrating profile show that there exists no probability of sand supplying directly by a large river through the apical area of tidal sand ridges either on land or in the sea. Fluvial deposits supplied the tidal sand bodies by alongshore transportation, which corresponds to the conclusions obtained by the analyses of provenance and paleocurrent field. Project supported by the National Natural Science Foundation of China (Grant Nos. 43236120 and 49676288).     

Impacts of Holocene and modern sea-level changes on estuarine mangroves from northeastern Brazil

Projections of the impacts of modern Relative Sea Level (RSL) rise on estuarine mangroves should be supported by coastal topographic data and records of mangrove dynamics under past RSL change. This work identified inland and seaward mangrove migrations along the Jucuruçu River (Bahia, Northeastern Brazil), during the Holocene based on sedimentary features, palynological and geochemical (δ¹³C, δ¹⁵N, C/N) data integrated with digital elevation models. During the Middle Holocene, in response to RSL rise, the estuary saw mangrove forest establish up to ~37 km inland. RSL stood between -1.4 (+0.36/-2.2 m) and +1 (2.19/0.2 m) around 7400 cal yr BP, and rose to a highest position of +3.25 (4.22/2.45 m) reached around 5350 cal yr BP. That marine incursion caused the inland replacement of freshwater vegetation by mangroves on tidal flats. Since then, the estuary experienced RSL fall, reducing inland tidal water salinity towards the Late Holocene, making that the mangroves were replaced by freshwater floodplain vegetation. Today, in the seaward part of the estuary near its mouth, mangroves occupy an area of ~10 km² along tidal channels. Considering a RSL rise of 98 cm up to the end of the 21^st century, at a rate significantly higher than that of Middle Holocene RSL rise (1.5 mm/yr) and fall (0.6 mm/yr), the current mangrove substrates are expected to drown and/or eroded near the coast, while new mangroves may establish inland, at topographically higher tidal flats in nowadays freshwater-tidal zones. Mangrove area could expand over 13 km² of coastal and flood plain. Following the same interaction between RSL/climate changes and Holocene mangrove dynamics, such upstream mangrove migration may be attenuated or intensified by changes in fluvial discharge. © 2019 John Wiley & Sons, Ltd.     

Re-assessing the nitrogen signal in continental margin sediments: New insights from the high northern latitudes

Organic and inorganic nitrogen and their isotopic signatures were studied in continental margin sediments off Spitsbergen. We present evidence that land-derived inorganic nitrogen strongly dilutes the particulate organic signal in coastal and fjord settings and accounts for up to 70% of the total nitrogen content. Spatial heterogeneity in inorganic nitrogen along the coast is less likely to be influenced by clay mineral assemblages or various substrates than by the supply of terrestrial organic matter (TOM) within eroded soil material into selected fjords and onto the shelf. The δ¹⁵N signal of the inorganic nitrogen (δ¹⁵N_inorg) in sediments off Spitsbergen seems to be appropriate to trace TOM supply from various climate- and ecosystem zones and elucidates the dominant transport media of terrigenous sediments to the marine realm. Moreover, we postulate that with the study of sedimentary δ¹⁵N_inorg in the Atlantic–Arctic gateway, climatically induced changes in catchment's vegetations in high northern latitudes may be reconstructed. The δ¹⁵N_org signal is primarily controlled by the availability of nitrate in the dominating ocean current systems and the corresponding degree of utilization of the nitrate pool in the euphotic zone. Not only does this new approach allow for a detailed view into the nitrogen cycle for settings with purely primary-produced organic matter supply, it also provides new insights into both the deposition of marine and terrestrial nitrogen and its ecosystem response to (paleo-) climate changes.     

Holocene vegetation succession and responses to climate change in the northern sector of Northeast China

Sediment pollen samples from the Huola Basin in the northern sector of northeast China, and surface pollen samples from its environs, were analyzed to reconstruct accurately the historical response of vegetation to climate change since 9100 cal yr BP. Pollen analysis of the Huola Section indicates that vegetation experienced a transformation from early-mid Holocene warm-cold mixed vegetation to late Holocene cold-temperate vegetation. From 9100 to 6000 cal yr BP, the study area was warmer and moister than at present, developing Corylus, Carpinus, Pinus, Picea, Betula and Larix-dominated forests. Two cooling events at 6000–5000 and 3500–2500 cal yr BP led to a decrease in Corylus, Carpinus and other warmth-loving vegetation, whereas cold temperate forests composed of Larix and Betula expanded. After 2500 cal yr BP, Larix and Betula dominated cold-temperate vegetated landscapes. The Holocene warm period in NE China(9100–6000 cal yr BP) suggests that such warming could have resulted in a strengthening of the influence from East Asian Summer Monsoon on northernmost NE China and would have benefited the development of warm-temperate forest vegetation and an improved plant load, which also provides the similarity model for the possible global warming in the future.     

福州盆地全新世沉积物的磁学性质及其对环境变化的响应

福州盆地位于海陆过渡地带,在海陆变迁过程中,沉积物记录了高分辨率的环境信息,是揭示沉积特征对环境变化响应过程及模式的理想区域.本文选择位于福州盆地的FZ5钻孔进行岩石磁学、环境磁学和古地磁学方面的研究,以期阐明该区域沉积物磁学性质对陆源碎屑输入、海平面变化和成岩作用的响应.岩石磁学结果表明钻孔沉积物以低矫顽力的亚铁磁性矿物为主体,但是在不同的环境变化阶段,磁性矿物的类型有较大变化.在9~3 cal. ka BP的海侵过程中,沉积物中以磁铁矿为主体,存在菱铁矿和铁硫化物等还原性矿物.硫化作用使细粒磁铁矿溶解形成胶黄铁矿和黄铁矿,其峰面随碎屑磁性矿物的浓度变化而迁移.但硫化作用没有完全消除磁铁矿携带的特征剩磁和陆源碎屑输入量以及海平面升降对该阶段沉积物磁性的控制.在~3 cal. ka BP以来随着海平面下降、沉积环境向陆相氧化环境转化,虽然早期还原作用仍然存在,但后期氧化作用使磁性矿物向高矫顽力的赤铁矿等矿物转变,氧化作用基本扰乱了磁铁矿携带的剩磁.沉积及其后期成岩作用过程中,发生在约~8.2、~7.7、~7.5、~2.7、~1.5、~0.5 cal. ka BP六次强烈的古氧化界面反映了福州盆地当时异常干旱或湿热的气候事件.     

南黄海盆地中部隆起CSDP-2井初步成果及其地质意义

南黄海盆地是新生代、中生代、古生代大型叠合盆地,具有良好的油气资源前景.中部隆起是南黄海盆地的二级构造单元,由于缺乏钻探资料,对中部隆起前新生代地层分布和油气资源前景的认识众说纷纭.因此,在中部隆起上实施科学钻探,探查中-古生代地层属性,对研究南黄海区域地质构造特征和油气地质条件意义重大.针对科学钻探目标,采用区域地质背景指导下的地质、地球物理综合研究的方法,拟定了科学钻探井(CSDP-2井)位置;利用叠前时间偏移成像处理剖面,采用地震相、地震速度分析和储层预测技术,进行了钻前层位预测和油气储层分析.该井由青岛海洋地质研究所负责的"大陆架科学钻探"项目实施,全取芯钻探成果表明,中部隆起上赋存了三叠系-奥陶系海相残余地层,发育中等—好级别的、厚度较大的海相中-古生界烃源岩,在三叠系青龙组、二叠系龙潭组和栖霞组、泥盆系和志留系中获得多层不同级别的油气显示.CSDP-2井的钻探发现,结束了关于中部隆起海相地层属性的争论,坚定了南黄海海相油气勘探的信心,为区域地质研究和油气地质条件分析提供了基础数据.     

Magnetic mineral diagenesis in the post-glacial muddy sediments from the southeastern South Yellow Sea: Response to marine environmental changes

Core YSDP103 was retrieved in the muddy deposit under the cold eddy of the southeastern South Yellow Sea, and the uppermost 29.79 m core represents the muddy sediments formed in the shelf since about 13 ka BP. The lower part from 29.79 to 13.35 m, called Unit A2, was deposited during the period from the post-glacial transgression to the middle Holocene (at about 6 14C ka BP) when the rising sea level reached its maximum, while the upper part above 13.35 m (called Unit A1) was deposited in a cold eddy associated with the formation of the Yellow Sea Warm Current just after the peak of post-glacial sea level rise. Rock-magnetic properties of the uppermost 29.79 m core were investigated in detail. The experimental results indicate that the magnetic mineralogy of the core is dominated by magnetite, maghemite and hematite and that, except for the uppermost 2.35 m, the magnetic minerals were subject to reductive diagene-sis leading to significant decline of magnetic mineral content and the proportion of low-coe     

The Y-3 tephra: A Last Glacial stratigraphic marker for the central Mediterranean basin

The paper reviews the existing data on the Y-3 tephra layer, first recognised in the Ionian Sea (Mediterranean basin). The collection and collation of old and new data on distal tephra occurrences in terrestrial, marine and lacustrine successions indicate that the Y-3 layer is dispersed over a wide area of the central Mediterranean basin. The peculiar homogeneous chemical composition of this layer makes its recognition rather straightforward and permits it being distinguished from other stratigraphically adjacent tephras. The best age estimate for the Y-3 layer of ca 30–31 cal ka BP, its peculiar stratigraphic position close to the Marine Isotope Stage 3/2 transition or Heinrich Event 3 onset, as well as its wide dispersion makes this layer an important marker to link and date late Pleistocene terrestrial and marine archives of the central Mediterranean basin.     

Interbasin freshwater,heat and salt transport through the boundaries of the East and South China Seas from a variable-grid global ocean circulation model

It has long been recognized that the circulation in the East China Sea (ECS) and Japan/East Sea (JES) is closely related with that in Pacific, especially with the Kuroshio (e.g., Nitani[1], Hi-daka[2]). Based on current measurements in the Taiwan Strait a…     

Modeling the Yellow River sediment flux and its deposition patterns under climatological conditions

A numerical sediment transport model was embedded into a coupled wave-tide-circulation model to quantitatively estimate the suspended sediment fluxes (SSF) and distribution in different areas for the Yellow River derived sediment. The model is validated by comparing model simulated sediment deposition rates with those from observations. Simulated results show that the SSF of the Yellow River across two major sections (the Bohai Strait and the 37° N section) are highest during September and October, whereas for the 32° N section the flux is negligibly small (less than 0.1 kg/s). We demonstrate that the sediment flux is primarily driven by the buoyancy forcing of the Yellow River freshwater discharge and modulated by the wind-driven surface wave and circulation patterns in this region. The SSF across the Bohai Strait is about 30 % of the Yellow River discharge, while across the 37° N section it is 15.8 %. Therefore, about 70 % of the total discharged Yellow River sediments are deposited in the Bohai Sea, 14.1 % in the North Yellow Sea, and 13.9 % in the South Yellow Sea. There are two deposition branches in the Yellow Sea. The primary one is located off the eastern tip of the Shandong Peninsula and extends to the southwest off the coastline, which is consistent with the observed “Ω”-shape deposition pattern. This simulated tongue shape deposition pattern is isolated from the north by the strong resuspension off the eastern tip of Shandong Peninsula. The secondary branch extends to the middle of the South Yellow Sea and has been strengthened by resuspension process. The two deposition branches are separated by the wintertime Yellow Sea Warm Current in the bottom layer.     

Holocene high lake-levels and pan-lake period on Badain Jaran Desert

Many lakes exist in southeastern Badain Jaran Desert and its hinterland, including 110 perennial lakes and some seasonal or extinct lakes. Geomorphological, sedimentological, and bioglyph evidence obtained from field investigations on Badain Jaran Desert lake group, alongside measurements and dating performed on lake relic, prove that these lakes expanded while the climate was relatively wet during early and middle Holocene. The dating results suggest that the pan-lake period of the Badain Jaran Desert began at 10 cal kyr BP, before which the limnic peat period occurred(11–10 cal kyr BP). Many lakes reached their maximal water-level during 8.6–6.3 cal kyr BP and retreated or dried up in the late Holocene(about 3.5–0 cal kyr BP). During that period, the precipitation at Badain Jaran Desert may have reached 200 mm yr~(-1) for 7.7–5.3 cal kyr BP, inferred from both the age and precipitation rate of calcareous root tubes. The water balance calculation shows that wetter and warmer climate and the increase of underground water recharge were key factors in maintaining and developing the lake group at both centennial and millennial time scales. Furthermore, lake surface expansion and the increasing fresh water availability set the background for the prosperous prehistoric culture.     

Evolution of the Southern Yellow Sea Cold Water Mass during the last 7 kyr from benthic foraminiferal evidence

The Southern Yellow Sea Cold Water Mass(YSCWM) is closely related to the modern circulation system of the east China shelf seas, which has significantly influenced regional marine environmental changes. The study of the Holocene evolution of the YSCWM will greatly improve our understanding of the mechanisms of regional environmental change. Benthic foraminifera are sensitive to bottom water environmental changes and can serve as useful indicators in bottom water environmental reconstruction. In this study, benthic foraminifera were analyzed in core N02 from the northwestern margin of the southern Yellow Sea Mud to decipher the phase evolution of the YSCWM during the last 7 kyr. Benthic foraminifera census counts and Q-mode factor analysis indicate that the Holocene sedimentary environment can be divided into three stages: From6.9–5.0 ka, the fauna was dominated by Ammonia ketienziensis, indicating that the YSCWM was at its strongest during the last 7 kyr, while the Yellow Sea Coastal Current(YSCC) had a weak influence on the bottom water of the study area. From 5.0–2.9 ka,the relative abundance of Hanzawaia nipponica remarkably increased while the abundance of A. ketienziensis decreased significantly, reflecting that the strength of the YSCWM was relatively weak and the range of the YSCWM might have contracted. The influence of the YSCC on the bottom water might have slightly increased, although its influence was still weak during this time. A notable increase in low-temperature and low-salinity species, such as Protelphidium tuberculatum and Buccella spp. has occurred since 2.9 ka, indicating that the YSCC has had a strong influence on bottom water during this period,while the strength of the YSCWM has been at its weakest during the last 7 kyr. Generally, the influence of the YSCWM and the YSCC on the bottom water properties of the study area show an obvious seesaw pattern, with one's influence increasing while the other's influence decreases and vice versa. The fluctuations in the strength of YSCWM during the Holocene may be caused by the different effect allocations of regional climatic factors(i.e. El Ni?o Southern Oscillation, East Asian Winter Monsoon,summer insolation in the northern hemisphere, etc.) acting on the circulation system during different periods.     

Environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, China

One of the goals for paleaoenvironmental research is to predict the tendency of future climate and environmental changes based on the understanding of the past. The key approach is to find similar pictures which happened in the past. By understanding the background and mechanism of the paleaoenvironmen- tal changes, reliable parameters and verifications can be provided for the numerical model to predict the tendency of future climate and environmental changes. The Mid-Holocene as the nearest …     

南黄海盆地基底及海相中、古生界地层分布特征

南黄海盆地是大型海相中、古生界和陆相中、新生界两期叠合型盆地,本文根据最新地震资料结合钻井资料及与海陆地质资料的对比研究对盆地内地震层序进行了划分,得到了陆相中、新生界盆地基底即中、古生界海相盆地的顶界埋深、三叠系和上二叠统的残留厚度,推断了陆相层基底地层分布,并根据磁力异常资料推测了海相中、古生界盆地结晶基底埋深,推断了海相中、古生界整体残留情况.下三叠统青龙组和上二叠大隆及龙潭组在南黄海盆地南部坳陷及勿南沙隆起广泛存在,而在北部坳陷的分布则狭窄,中部隆起则由于隆起和剥蚀作用导致这两套地层几乎没有残余.对中-古生界海相盆地和中-新生界陆相盆地的基底特征进行了比较,认为海相中、古生界在南黄海地区区域性存在,海相层厚度分布特征受基底起伏控制,同时受到印支板块运动的影响,中部隆起区是海相中、古生界比较稳定的地区.下古生界可能在南黄海盆地广泛分布,但受资料限制,还难以获知其残余地层的特征.     

Sediment accumulation rates in subarctic lakes: Insights into age-depth modeling from 22 dated lake records from the Northwest Territories,Canada

Age-depth modeling using Bayesian statistics requires well-informed prior information about the behavior of sediment accumulation. Here we present average sediment accumulation rates (represented as deposition times, DT, in yr/cm) for lakes in an Arctic setting, and we examine the variability across space (intra- and inter-lake) and time (late Holocene). The dataset includes over 100 radiocarbon dates, primarily on bulk sediment, from 22 sediment cores obtained from 18 lakes spanning the boreal to tundra ecotone gradients in subarctic Canada. There are four to twenty-five radiocarbon dates per core, depending on the length and character of the sediment records. Deposition times were calculated at 100-year intervals from age-depth models constructed using the ‘classical’ age-depth modeling software Clam. Lakes in boreal settings have the most rapid accumulation (mean DT 20 ± 10 yr/cm), whereas lakes in tundra settings accumulate at moderate (mean DT 70 ± 10 yr/cm) to very slow rates, (>100 yr/cm). Many of the age-depth models demonstrate fluctuations in accumulation that coincide with lake evolution and post-glacial climate change. Ten of our sediment cores yielded sediments as old as c. 9000 cal BP (BP = years before AD 1950). From between c. 9000 cal BP and c. 6000 cal BP, sediment accumulation was relatively rapid (DT of 20–60 yr/cm). Accumulation slowed between c. 5500 and c. 4000 cal BP as vegetation expanded northward in response to warming. A short period of rapid accumulation occurred near 1200 cal BP at three lakes. Our research will help inform priors in Bayesian age modeling.     

Holocene vegetational and climatic variation in westerly-dominated areas of Central Asia inferred from the Sayram Lake in northern Xinjiang,China

Changes in the vegetation and climate of the westerly-dominated areas in Central Asia during the Holocene were interpreted using pollen-assemblages and charcoal data from a 300-cm-long sediment core of the Sayram Lake,northern Xinjiang.Accele-rator Mass Spectrometry(AMS) radiocarbon dating methods were applied to bulk organic matter of the samples.Artemisia spp./Chenopodiaceae ratios and results from principal component analysis were used to infer that the lake basin was dominated by desert vegetation before ca.9.6 cal.ka BP,which suggests a warm and dry climate in the early Holocene.Desert steppe/steppe expanded during 9.6-5.5 cal.ka BP,indicating a remarkable increase both in the precipitation and temperature during the mid-Holocene.Desert vegetation dominated between 6.5 and 5.5 cal.ka BP,marking an extreme warmer and drier interval.The steppe/meadow steppe recovered,and temperatures decreased from 5.5 cal.ka BP in the late Holocene,as indicated by the increased abundance of Artemisia and the development of meadows.Holocene temperatures and moisture variations in the Sayram Lake areas were similar to those of adjacent areas.This consistency implies that solar radiation was the main driving factor for regional temperature changes,and that the effect of temperature variations was significant on regional changes in humidity.The evolution of climate and environment in the Sayram Lake areas,which were characterized as dry in the early Holocene and relatively humid in the middle-late Holocene,are clearly different from those in monsoonal areas.Dry conditions in the early Holocene in the Sayram Lake areas were closely related to decreased water vapor advection.These conditions were a result of reduced westerly wind speeds and less evaporation upstream,which in turn were caused by seasonal changes in solar radiation superimposed by strong evaporation following warming and drying local climate.