High-resolution climate evolution derived from the sediment records of Erlongwan Maar Lake since 14 ka BP

Varve counts with AMS 14 C,137 Cs and 210 Pb dating of sediments(0-900 cm) from Erlongwan Maar Lake,NE China were used to establish a high-resolution chronology series for the late Quaternary.Dry density,total organic carbon(TOC) content,total nitrogen(TN) content,TOC/TN ratios and stable organic carbon isotope(13 C org) ratios were continuously analyzed on this sediment profile.On the basis of lithological characters,sporo-pollen assemblages and geochemical analyses,we identified 6 climate stages within the last 14 ka BP.The time before the Holocene(14-11.4 ka BP) represents a higher-order oscillation climatic transitional period(I).The entire Holocene climate development(from 11.4 ka BP to present) exhibited an increasing temperature trend,although there were cold and warm alternations(II-VI).The periods included were:II(11.4-9.05 ka BP) warm-wet stage,III(9.05-7.4 ka BP) cold and warm fluctuation stage,IV(7.4-4.2 ka BP) smoothly warming climate stage,V(4.2-1.67 ka BP) climate optimum stage,and VI(from 1.67 ka BP to present) cool and drier stage.Each climate stage began with a warming event and ended with an abrupt cooling event.This climate change cycle had unequal time spaces that were progressively shorter over time.Several abrupt climate shifts occurred at about 9.4-9.05,8.5-8.2,7.8-7.4,4.6-4.2,3.7-3.25,2-1.67 and 0.3-0.03 ka BP.Thus,it can be seen that the climate has been warming since 1920 AD,which indicates a new climate stage.     

萨拉乌苏河流域全新世气候变化的元素地球化学记录

通过对萨拉乌苏河流域滴哨沟湾左岸沉积剖面常量元素Si、Al、Fe、Ca、Mg、K、Na含量及其比值变化的分析,结合~(14)C测年结果及粒度、有机质指标,并综合已有研究,探讨了该地区全新世以来的气候变化.研究表明,9.6ka BP前气候干冷,沉积相为风成沉积;9.6~8.4ka BP气候由干冷向暖湿转变,期间存在干冷波动;8.4~4.0ka BP进入全新世大暖期,其中,8.4~6.5ka BP为全新世大暖期的鼎盛时期,降水增加,积水成湖,湖泊水位高且稳定;6.5ka BP气候发生明显转变;6.5~4.0ka BP湖泊水位逐步下降形成富含螺壳的浅水环境,但气候整体仍较为湿润;4.0~1.2ka BP气候变干冷,发育沼泽;1.2~0.7ka BP气候转暖湿,沉积相由沼泽相转变为湖泊相;0.7~0.5ka BP为河流相沉积,气候较为干冷.剖面记录的气候变化可与东亚季风变化、温度变化、太阳辐射进行对比,反映了该区域气候变化与全球气候变化的一致性.     

田洋玛珥湖中更新世以来磁化率特征及其环境意义

 对雷州半岛东南部的田洋玛珥湖TYC孔前40 m岩芯进行了研究,结果表明,磁化率与孢粉有很好的对应关系,因而磁化率值的高低变化能够作为该区气候环境变化的替代指标。沉积物磁化率与气候变化的关系为：磁化率的低值与气候暖湿对应;磁化率的高值则与气候寒冷或温凉相对应。中更新世以来,田洋玛珥湖气候环境演化经历了9个不同的阶段：346~301.4 kaBP,气候相对暖湿。301.4~248.8 kaBP,气候寒冷干燥。248.8~188.8 kaBP,气候相对暖湿。188.8~125.2 kaBP,气候寒冷干燥。125.2~69.3 kaBP,气候较为暖湿。69.3~40.43 kaBP,气候偏凉。40.43~25.5 kaBP,气候偏凉但较上阶段温度低,此时玛珥湖呈现出沼泽化过渡阶段。25.5~10.8 kaBP,气候寒冷干燥,玛珥湖干枯成为干玛珥湖。10.8 kaBP以来,由于后期人类活动对玛珥湖的改造,致使磁化率值不断升高。     

Holocene climatic and environmental changes recorded in Baahar Nuur Lake core in the Ordos Plateau, Inner Mongolia of China

A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar) and δ 18O (δ 18Ocar) were conducted for retrieving the Holocene chronosequence of climaticchanges based on 15 AMS 14C dates. The record documented four major stages of climate change inthe Ordos Plateau: (IV) a cold and dry condition before ～7.65 14C ka BP; (III) a warm and humid stagebetween ～7.65 and ～5.40 ka BP; (II) a generally drier and cooler climate since ～5.40 ka BP with twohumid events occurring from ～4.70 to ～4.60 ka BP and from ～4.20 to ～3.70 ka BP, and (I) a dry climatecharacterized by complete desiccation of the lake after 3.70 ka BP. Stage III can be further divided intothree sub-stages: (IIIa) a warm and humid episode from ～7.65 to ～6.70 ka BP, (IIIb) a warm and relativelydry episode from ～6.70 to ～6.20 ka BP, and (IIIc) the magthermal and maghumid episode of the Holo-cene from ～6.20 to ～5.40 ka BP.     

A high-resolution environmental change record since 19 cal ka BP in Pumoyum Co,southern Tibet

A 380-cm-long sediment core was acquired from the deep water area of Pumoyum Co, southern Tibet. Twenty-five plant residue samples were selected, and organic carbon stable isotopes were obtained using the AMS ¹⁴C chronological method. The ¹⁴C age and carbon reservoir effect were calibrated with surface sedimentation rate measurements using ²¹⁰Pb dating. Results showed that the core sediment deposited over 19 cal ka BP. Based on a multi-proxy analysis of TOC and IC contents, grain size and pollen assemblage data, the palaeoclimatic evolution of Pumoyum Co was reconstructed since the last glacial. Pumoyum Co was a shallow lake prior to 16.2 cal ka BP; although the glacier around the lake began to melt due to increasing temperatures, climate was still cold and dry. In the interval of 16.2–11.8 cal ka BP, the sedimentary environment fluctuated drastically and frequently. Two cold-events occurred at 14.2 and 11.8 cal ka BP, and these may correspond to the Older Dryas and the Younger Dryas events, respectively. After 11.8 cal ka BP, Pumoyun Co developed into the deep lake as it is now. The lake water temperature was relatively lower at that time because of influx of cold water from glacial meltwater entering the lake. As a result, the multi-proxy indicators showed no sign of warm conditions. Comparisons between the sedimentary record of Pumoyum Co with that of other lakes of the same age in southern Tibet indicate a warmer climate following the last deglaciation influenced the southeastern Tibetan Plateau. These results imply that the southwest Asian monsoon gradually became stronger since the deglaciation during its expansion to the inner plateau. The glacial-supplied water of the lake responded sensitively to cold-events. The entire southern Tibet region was dominantly influenced climatically by the southwest Asian monsoon during the Holocene.     

Pollen-inferred vegetation and environmental changes since 16.7 ka BP at Balikun Lake,Xinjiang

A high-resolution fossil pollen record from the sedimentary cores of Balikun Lake, northwestern China, combined with modern surface pollen data, is used to reconstruct the history of vegetation and climatic change since 16.7 cal. ka BP. Fossil pollen assem-blages and lithology indicate that the study area was dominated by desert. The desert had extremely arid climate and lower effective moisture during 16.7–7.9 cal. ka BP, especially from 16.7 to 8.9 cal. ka BP when the lake maybe dried up. During 8.9–7.9 cal. ka BP, the environment gradually recovered in this area. It was then followed by the optimum period from 7.9 to 4.3 cal. Ka BP, when the effective moisture obviously increased. It was characterized by the typical desert-steppe/steppe vegetation and was accompanied with several patch-birch woodlands around the lake. After that, a short but extremely arid climatic event occurred during 4.3–3.8 cal. ka BP, and the vegetation quickly changed from desert-steppe/steppe to desert. It was a relatively optimum period from 3.8 to 0.53 cal. ka BP showing typical desert-steppe/meadow-steppe landscape. Since 0.53 cal. ka BP, the climate has shown signs of deteriorating again. Furthermore, regional comparison shows that the characteristics of climatic and environmental evolution in this area were clearly different from East Asia monsoonal area during the last 16.7 cal. ka BP. It was characterized by the arid climate during the late-glacial and early Holocene, and relatively wet during the mid-late Holocene.     

35 ka BP climate simulations in East Asia and probing the mechanisms of climate changes

Interglacial or postglacial climates are all of charac-teristic of warmer conditions. However, if condition asso-ciated with the warm feature is wetter or drier than today,it would produce different impacts on natural environ-ments and human society. Quaternary studies found thatclimate with warm-dry or warm-wet conditions had oc-curred in China during the last 40—30 ka BP[1]. For ex-ample, it was warmer than the present during themid-Holocene (3—8 ka BP) and the late phases of MarineIsot…     

Changes in palaeoproductivity of Genggahai Lake over the past 16 ka in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau

Sequential samples of a 7.82-m sediment core from Genggahai Lake in the central Gonghe Basin,controlled with 12 accelerator mass spectrometry (AMS) 14 C dates,have been analysed for total organic carbon (TOC) and total nitrogen (TN) contents,carbon isotope of bulk organic matter (δ 13 C org),and carbonate content.Plant macrofossils and stem encrustations,derived mainly from the species of P.pectinatus,M.spicatum and Chara spp.,were identified,and they dominated the aquatic plant community of the lake.Alternations of plant macrofossils of Chara spp.and the vascular species reflect the changing productivity of the lake over time.In such a shallow lake,the carbonate content is highly related to photosynthesis of aquatic macrophytes and thus indirectly indicates variations in productivity,consistent with a quantitative estimate of palaeoproductivity.Based on these results,the palaeoproductivity history was reconstructed over the past ca.16 ka.The lake was formed or recharged at 15.3 cal ka BP,as indicated by aeolian sand deposits at the core base.A marked increase in palaeoproductivity occurred from 15.3 to 11.6 cal ka BP.Between 11.6 and 9.2 cal ka BP,a sharply increased water-level,modulated probably by the enhanced Asian summer monsoon,might have exceeded the optimum water depth for macrophyte vegetation,causing a marked decline in coverage of aquatic macrophytes and low palaeoproductivity.The palaeoproductivity appeared to be high in the early stage of the period from 9.2 to 7.4 cal ka BP,and then decreased at approximately 8.6 cal ka BP.The palaeoproductivity sustained an overall high level between 7.4 and 2.1 cal ka BP,and decreased gradually since 2.1 cal ka BP.Our results suggest that the variability of Genggahai Lake palaeoproductivity may be associated with fluctuations of the lake level controlled by the strength of the Asian summer monsoon,probably indicating changes in the Asian summer monsoon.     

Pollen records of Holocene vegetation and climate changes in the Longzhong Basin of the Chinese Loess Plateau

Pollen records with an average time resolution of 20-200 years from Holocene loess sections at Dingxi, Qin'an, and other localities of Gansu Province reveal a detailed history of vegetation and climate changes in the western Loess Plateau. For most time of the Holocene, the landscape was dominated by grasslands or forest steppes. However, during the middle Holocene (7.5-5.8 ka BP), relatively dense forests developed, and the endemic vegetation flourished, suggesting a much warmer and more humid climate condition than the present. Superimposed upon this general pattern are several dry intervals marked by the episodic expansion of grasslands or forest steppe. Xeric vegetation expanded after 3.8 ka BP, indicating a trend towards dry conditions.     

Pollen-recorded climate changes between 13.0 and 7.0 ^14C ka BP in southern Ningxia, China

A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from~13.0 to~7.0 14 C ka BP.A steppe landscape under a moderately dry(and probably cool)condition(~12.7-~12.1 14 C ka BP)was replaced by a coniferous forest dominating the landscape under a generally wet climate from~12.1 to ~11.01 4C ka BP.This generally wet period,corresponding to the European B?lling/All?rod period,can be divided into three stages:a cool and wet stage between~12.1 and~11.4 14 C ka BP,a mild and rela- tively dry stage between~11.4 and~11.2 14 C ka BP,and a mild and wet stage between~11.2 and~11.0 14 C ka BP.The coniferous forest-dominated landscape was then deteriorated into steppe landscape (~11.0-~10.6 14 C ka BP)and further into a desert steppe landscape from~10.6 to~9.8 14 C ka BP,being correspondent to the European Younger Dryas period.After a brief episode of a cool and wet climate (~9.8-~9.6 14 C ka BP),a relatively mild and dry condition prevailed during the early Holocene(~9.6- ~7.6 14 C ka BP)and then a warm and humid climate started the mid-Holocene(~7.6-~7.2 14 C ka BP).     

青藏高原西南部仲巴地区细石器人类活动的时代探讨

青藏高原西南部仲巴地区已发现有3处细石器遗存地点,在仲巴地区选取了一个全新世风成沉积剖面进行年代测试分析以及粒度、地球化学元素等环境指标的分析,探讨仲巴地区的人类活动与气候变化及风沙活动的关系,进而推算细石器遗存的时代.8.9~7.3ka BP为气候湿润,风沙活动弱,成壤作用较强的时期,自然资源相对丰富,能够为细石器先民提供良好的狩猎活动条件.到7.3~3.8ka BP时期,气候干燥,风沙活动强,不利于人类活动.因此推测该区细石器遗存的形成时代在8.9~7.3ka BP左右.     

新疆巴里坤湖9.0 cal ka BP以来沉积物地球化学元素分布特征与古气候环境演化

根据中国西北干旱区巴里坤湖BLK-1剖面沉积物的地化元素分析,采用SPSS因子分析法提取了对沉积环境变化敏感的地化元素和氧化物组分.在R、Q型因子分析的基础上,结合沉积物的硅铁铝率(SiO2/(Al2O3+Fe2O3))、淋失系数(SiO2/(MgO+K2O))、CaO/MgO以及腐殖化度等指标,提取出古气候环境信息.初步研究结果表明:近9.0 cal ka BP以来,巴里坤湖地区气候环境仍以干旱化为主,全新世期间出现过多次不同程度的干湿变化,经历了5个气候阶段:9.0—7.5 cal ka BP期间,气候干旱;7.5—5.8 cal ka BP期间,气候温暖湿润,为研究区全新世最佳适宜期;5.8—3.0 cal ka BP期间,气候干旱;3.0—1.0 cal ka BP期间,气候湿润;1.0—0 cal ka BP期间,气候干旱.     

A high-resolution climatic chanse since Holocene inferred from multi-proxy of lake sediment in westerly area of China

Multi-proxy data are presented and a discuss is made of paleoclimatic and paleoenvironmental changes during Holocene from a 225-cm-long sediment core from Wulungu Lake, located in westerly area of China. The chronology is constructed from six AMS radiocarbon dates on the bulk organic matter. Analyses of pollen, TOC, TN, δ^13Corg, ostracod assemblages and the shell stable isotopes, suggest Holocene climate pattern as follows： temperate and dry （10.0-7.6 cal. ka BP） -warm and wet （7.6-5.3 cal. ka BP） -warm and moist （5.3-3.6 cal. ka BP） -temperate and dry （3.6-2.1 cal. ka BP）-temperate and moist （2.1-1.3 cal. ka BP） -cool and dry （1.3 cal. ka BP-present）. With the climatic change, Wulungu Lake experienced two large-scale retreat （5.3-3.6 cal. ka BP and 1.3 cal. ka BP-present） and an obvious transgression （7.6-5.3 cal. ka BP）. The records of climatic and environmental evolution of Wulungu Lake were in good accordance with those of adjacent areas. It responded to regional environmental change, global abrupt climate events and followed the westerly climate change mode.     

鄂西七姊妹山泥炭藓湿地沉积物粒度特征及其环境意义探讨

以鄂西七姊妹山泥炭藓湿地QZMS钻孔沉积物为研究对象,通过AMS14C测年、岩性特征与沉积物粒度综合分析,探讨了鄂西南山地13 000 cal. a BP以来的沉积环境变迁.研究结果显示：QZMS钻孔沉积物粒度组成主要以细粉砂和中粉砂为主,频率分布曲线均为单峰分布,由下至上,峰度由宽到窄,偏度从近于对称到正偏,揭示了搬运动力和沉积环境的演变过程;综合分析结果表明研究区沉积环境演化可分为4个阶段：1) 12.9～11.6 cal. ka BP,气候波动频率高,但幅度较小,水动力条件相对较弱;2) 11.6～10.2 cal. ka BP为晚更新世向全新世的过渡阶段,水动力条件持续较弱,环境相对稳定;3) 10.2～7.7 cal. ka BP早全新世,气候变得暖湿,水动力条件较前一阶段有所增强,泥炭藓湿地开始形成;4) 7.7～2.0 cal. ka BP气候暖湿,水动力条件达到最强,峰度和偏度波动频率低,但幅度增大,为沼泽湿地环境.研究表明七姊妹山泥炭藓湿地沉积物的粒度粗细与区域内水文条件和物源的变化密切相关,借助粒度组成和参数特征,可反演该区域的沉积环境演变,揭示泥炭藓湿地发育形成的过程,为该地区泥炭藓湿地的保护和气候环境变化研究提供科学参考.     

Stalagmite-inferred Holocene precipitation in northern Guizhou Province,China, and asynchronous termination of the Climatic Optimum in the Asian monsoon territory

An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest China. The  18O-inferred climate conditions are divisible into three distinct stages: (1) a maximum humid era from 9.9-6.6 ka BP; (2) a gradual declining precipitation interval between 6.6-1.6 ka BP; and (3) a relatively low precipitation time window after 1.6 ka BP. Consistency of contemporaneous stalagmite Holocene 18O records between Shigao and other caves in the Indian and East Asian monsoon realms support the effect of primary orbital solar forcings on monsoonal precipitation. However, statistical analysis shows a significant spatial asynchroneity of the Holocene Optimum termination in the Asian monsoon territory. The Holocene Optimum ended at 7.2-7.4 ka BP in Oman, located in the Indian monsoon region, and at 5.6-5.8 ka BP in Central China, in the East Asian monsoon zone. In Southwest China, the termination occurred between these periods, at 6.6-7.0 ka BP, and was influenced by both monsoon systems. We propose that this spatially asynchronous ending of Holocene Optimum in Asia may be attributed to sea surface temperature changes in the western tropical Pacific, which is a primary moisture source for the East Asian monsoon.     

腾格里沙漠南缘末次冰消期微量元素反映的古气候环境

腾格里沙漠南缘土门剖面52L~41FD层段由3层风成沙丘砂、2层湖相沉积、2层古土壤和5层砂黄土构成. 分析结果表明:微量元素含量的高低变化依次为Mn、P、Sr、Rb、Cr、V、Zn、Ni、Cu、Nb,各元素含量在砂黄土、古土壤和湖相沉积中表现为相对峰态,而在沙丘砂层段中则呈现为相对谷态;在垂直方向上,各微量元素含量随着各沉积相的多次更替,构成了10条峰谷交替的锯齿状形态的元素波动过程线. 结合研究区地理位置与微量元素特征,认为可用Zn（ppm）、P（ppm）为代表作为气候替代性指标,指示本区东亚冬夏季风变化. 据此划分出了8个冷暖波动事件:冷干事件,即C1(11 870~11 640 a BP)、C2(12 650~12 050 a BP)、C3(13 340~13 010 a BP)、C4(13 810~13 620 a BP), 暖湿事件, 即W1(12050~11870 a BP)、W2(13010~12650 a BP)、W3(13620~13340 a BP)、W4(14850~13810 a BP). 本研究与格陵兰GRIP冰芯和中国南京葫芦洞H82石笋之间较高的同步性,这表明,腾格里沙漠南缘气候波动可能与格陵兰气候变化受相同的高纬动力驱动.     

Evolution of prehistoric agriculture in central Gansu Province,China: A case study in Qin’an and Li County

This study, based on environmental archaeological studies focused on Qin’an County and Li County in Gansu Province, China, shows that during 8–7.3 ka BP few cultivated crop seeds were found. After 6.4 ka BP, during the Banpo period, many crop seeds appeared, indicating the development of agriculture. Millet agriculture in this area appeared and flourished a little later than in the Central Plain of China. Climate change is an important factor that influenced the development of agriculture in this area. The rapid expansion of agriculture during late Yangshao and Changshan benefited from the humid and warm climate in the mid-Holocene, especially the emergence of rice. After 4 ka BP, climate became drier, and agriculture began to decline. So Siwa Culture is char-acterized by pastoral economy, until the Eastern Zhou period, agriculture began to recover, when wheat and barley appeared in Li County, indicating diversification of agriculture of this time.     

Paleoproductivity variations in the southern Okinawa Trough since the middle Holocene: Calcareous nannofossil records

Based on 17 AMS 14 C age data,we reconstructed high-resolution records of sea surface primary productivity(PP) in the southern Okinawa Trough(MD05-2908) over the last 6.8 ka BP using the calcareous nannofossil carbon isotope and the relative percentage contents of Florisphaera profunda indexes.The underlying mechanism controlling the sea surface PP was then discussed.The sea surface PP,indicated by the coccolith δ 13 C and %Fp conversional equations,decreased with some fluctuations since 6.8 ka BP.This decrease may be connected to the decreased terrigenous input resulting from the reduced East Asian Summer Monsoon(EASM) precipitation.Both the periods of 4-2 ka BP(PME) and 6.8-4.8 ka BP were characterized by relatively higher PP.The former was mainly controlled by the weakening of the Kuroshio Current,whereas the latter mainly resulted from the greater terrigenous input associated with the stronger EASM.     

太原盆地QK1钻孔60ka.B.P以来气候环境演化的沉积记录

通过对太原盆地QK1钻孔60 ka.B.P.以来的沉积物进行粒度、磁化率分析,探讨了太原盆地60 ka.B.P.以来的气候环境演化过程。太原盆地60 ka.B.P.以来主要经历了以下演化阶段:59.6～40 ka.B.P.属滨湖相沉积;40～31.5 ka.B.P.属以河流相漫滩沉积;31.5～14.58 ka.B.P.属河流相边滩沉积;14.58～12.5 ka.B.P.河流相漫滩沉积;12.5～9 ka.B.P.河漫湖泊沉积;9 ka.B.P.至今属河流相边滩沉积。60 ka.B.P.以来太原盆地的气候由温暖偏湿转为温暖湿润,在末次冰期表现为寒冷干燥,进入全新世大暖期以后,气候具有全球性特征的同时也兼具区域性特点。各指标分析表明太原盆地的气候环境演化主要受全球性气候变化及区域气候的影响,由于盆地沉降中心与边缘沉积速率的差异,在一定程度上受到地区构造活动的影响。     

Evidence and modeling study of droughts in China during 4―2 ka BP

Four periods with predominated droughts are identified in 4-2 ka BP according to documentary data, namely 3.6-3.5, 3.1-3.0, 2.8-2.7, and 2.45-2.35 ka BP. Palaeo-environmental data indicated that droughts were predominated in 4-2 ka BP in the south of Northeast China, Inner-Mongolia, east of Qinghai-Tibetan Plateau, and South China. Modeling study shows that precession may be responsible for the occurrence of droughts in 4-2 ka BP, integrating the GCM with forcing of insolation.