陕西五里铺黄土剖面中微量元素地球化学特征

通过对陕西五里铺黄土剖面微量元素的研究,发现古土壤中微量元素含量明显不同于黄土,表明风化成壤过程中不同元素的地球化学行为不同;元素含量的变化实质是气候变化的直接结果,其可以作为气候替代指标;较高的Pb、Cu、Zn、Cd、Cr、Ni、Co、Mn含量或低的Rb、Sr含量指示为古土壤,反映植被茂盛,气候湿润温暖;反之,则指示为黄土层,反映气候干冷;揭示全新时期黄土高原南部的气候并非持续温度,有明显的波动,经历了黄土（Lt)→古土壤（S0^2）→黄土（L0^2)→土壤（S0^1)→黄土及现代表土（L0^10）的发展演化阶段。     

青藏邛多江盆地40.4~30.0 cal ka BP湖相沉积物粒度特征及其古气候意义

对青藏邛多江盆地一段连续沉积剖面4个湖相沉积物样品进行AMS14C测年,得到此剖面的顶底年龄分别为30.0 cal ka BP和40.4 cal ka BP。并分析沉积物粒度的平均粒径(M_z)、中值粒径(M_d)、标准偏差(σ_1)、分选系数、频率分布曲线等,将研究区的古气候演变划分为5个阶段:阶段Ⅰ(40.4~38.5 cal ka BP)气候湿润期、阶段Ⅱ(38.5~35.4 cal ka BP)气候干旱期、阶段Ⅲ(35.4~32.4 cal ka BP)气候湿润期、阶段Ⅳ(32.4~31.7 cal ka BP)气候动荡期、阶段Ⅴ(31.7~30.0 cal ka BP)气候转干期。对比发现,粒度曲线与格陵兰冰芯氧同位素曲线有较好的响应,而且发现40.4~30.0 cal ka BP时期邛多江盆地有两次显著的气候事件:39.4 cal ka BP短暂干旱事件和35 cal ka BP强降水事件,而粒度均值曲线与格陵兰冰芯氧同位素曲线的差异,可能与特强夏季风有关。     

萨拉乌苏河流域MGS5层段CaCO3记录的末次间冰期东亚季风与沙漠环境演化

毛乌素沙漠萨拉乌苏河流域米浪沟湾剖面时代上属末次间冰期的MGS5层段可以进一步划分为5a-5e亚段．其中5a,5c和5e亚段以河湖相和古土壤为主要特征,其CaCO3含量主体呈现峰态;5b和5d亚段以风成沙丘砂沉积为主,CaCO3含量主体呈现谷态．研究表明,末次间冰期毛乌素沙漠冬季风盛行时期,沙丘砂强烈堆积,CaCO3大量迁移;夏季风盛行时期河湖相和古土壤发育,CaCO3大量聚集．研究还发现,MGS5各个亚段CaCO3记录的冬夏季风环境与格陵兰冰芯氧同位素5a-5e亚段在时间-气候性质上的变化节奏相当一致．这可能说明,末次间冰期毛乌素沙漠的演化主要受北半球冰量增减导致的东亚冬、夏季风强弱所控制．     

萨拉乌苏河流域DGS1层段主量元素记录的全新世气候变化

选取毛乌素沙漠东南部边缘萨拉乌苏河流域具有代表性的滴哨沟湾剖面全新统DGS1层段,通过测定样品的主量元素——Si O2、Al2O3、TOFE(全铁)、Ca O、Mg O、K2O、Na2O、Ti O2的含量并分析其特征,结合年代测定结果,探讨该地全新世气候演变.结果表明,主量元素表现出2个不同时期的不同波动方式:1CS~9P期间(0~3 760 a BP),Al2O3、TOFE、Ca O、Mg O、K2O、Na2O、Ti O2基本表现为在湖沼相中含量大于次生黄土,次生黄土中含量大于沙丘砂;10LS~21LS期间(3 760~11 000 a BP),Ca O、Mg O在湖沼相中出现峰值,尤其是在15LS(7 340~8 170 a BP)及其上下达到顶峰,其他主量元素表现为低值.通过分析发现,DGS1层段实际上是全新世以来多次东亚冬夏季风的交互演替过程下的堆积-风化产物,是气候地层的真实记录.依据CIA值与Si O2/(Al2O3+TOFE)比值,将DGS1层段主量元素信号记录的全新世气候可分为4个阶段:全新世早期气候好转、全新世鼎盛期、大暖期向寒冷期转变的波动期、降温不稳定和沙漠化频繁变化时期.     

宁夏长城塬全新世黄土土壤剖面微量元素动态与成壤变化

通过野外考察,在泾河上游的宁夏长城塬面发现完整典型的全新世黄土土壤剖面.在详细观察分析的基础上,进行了土壤地层划分和系统采样.利用X-Ray荧光光谱仪测定分析了V、Co、Ga、As、Y、Nb、La、Ce、Th、U等10种微量元素的含量,揭示了宁夏长城塬全新世黄土土壤剖面微量元素含量变化与成壤变化之间的关系,结果表明:微量元素V、Ga、As、Y、Nb在古土壤(S0)中富集,微量元素Th和U在过渡层中淋溶,而V和As在过渡层中富集.     

北京猿人洞穴堆积气候地层的再研究(英文)

周口店第一地点洞穴40余米厚的堆积层自下而上共分17层，新近测量的年代推前了近20万年，对堆支所含哺乳动物化石和孢粉资料进行聚类统计和因子分析，结合风化系数和微量元素含量等古气候代用指标，重新定量地描绘它所记录的古气候波动旋回，根据第2层TIMS测年为41万年BP，第14层上部是磁性地层测量的B／A界线，可以将该洞穴堆积层1－4层对比于深海岩芯δ^18O气候曲线的11－19段或中国黄土－－古土壤序列S4－S7，并且古气候旋回内的次级波动也可进行一定程序的对比。     

河南孟津地区中全新世环境变化及其对人类活动的影响

在河南孟津地区发现全新世古土壤－黄土沉积剖面和湖沼相沉积剖面。作者对这2个剖面之间进行了野外调查,绘制了其间的地层图,并在古土壤-黄土沉积剖面采样,对样品做了粒度、磁化率以及CaCO₃含量分析。通过古土壤－黄土沉积剖面与湖沼相沉积剖面的对比,研究了中全新世孟津地区环境变化及其对人类活动的影响。结果表明孟津地区在7020～5660aBP和4610～3755aBP是古湖泊形成和古土壤发育的时期,气候温暖湿润;在5660～4610aBP孟津地区经历了一次气候波动,湖泊缩小为零星湖沼, 古土壤发育中断;3755～3055aBP湖泊萎缩干涸,黄土开始沉积,气候转向冷干。河南龙山文化时代晚期,湖面水位较高,人类在古土壤上活动;二里头文化时期湖泊萎缩,人类活动向低处转移,湖泊完全干涸时人类开始在干涸的湖相沉积层上活动。     

重庆地区末次冰期H6事件起始时间探讨

本文利用重庆地区羊子洞Y02石笋的U/Th年龄数据和δ13C值建立了末次冰期60~65 ka BP时段的石笋碳同位素变化序列。Y02石笋的δ13C记录显示末次冰期的H6事件起始时间约为63 ka BP左右,不同于前人研究的60 ka BP。通过翻阅相关研究发现:末次冰期H6事件的起始时间尚存争议,早期的研究者将H6事件起始时间定于65~66 ka BP,随后的研究者又将其定于60 ka BP。通过将羊子洞Y02石笋δ13C值进行功率谱分析发现:Y02石笋δ13C记录主要存在228a,102a,77a和60a周期,表明末次冰期重庆地区的气候变化主要受控于太阳活动的影响。     

北极巴罗地区小冰期以来的冷暖事件

北极阿拉斯加巴罗(Barrow)地区(70°20′N,156°40′W)湖泊钻孔花粉记录,~(210)Pb 和~(137)Cs 测定以及多项环境代用指标测试(有机质含量、总 C 和总 N 含量、CaCO_3),揭示了小冰期以来 Barrow 地区曾发生3次暖期(公元1540～1600年,公元1660～1730年和公元1880～1992年)和3次冷期(公元1440～1520年,公元1610～1650年和公元1750～1850年)。这些冷暖事件与格陵兰世纪营和青藏高原古里雅冰芯记录对比发现,虽然在高频变化上,不同地区存在着差异,但重大冷暖事件都曾出现。     

有机质去除程度对粒度测量结果的影响及其意义

粒度分析是研究沉积物组成特征,重建古气候变化的重要手段之一.由于有机质会影响沉积物颗粒的组成状态,因此其去除程度会对粒度测试结果产生很大影响.粒度分析是风成沉积最常用的分析方法,本研究选取古土壤、弱发育古土壤、黄土、砂黄土四种有机质含量不同的沉积物样品为对象研究有机质去除程度对粒度测量结果的影响.结果显示,彻底去除有机质后的古土壤平均粒径明显增加,说明在古土壤中有机质主要以细颗粒形式存在;弱发育古土壤和黄土的平均粒径随着有机质的去除逐渐降低,说明其中的有机质以较大颗粒的形式存在并且对沉积物产生了胶结作用;而对于砂黄土,有机质的去除程度对样品粒度测量结果影响不大,因为有机质含量较少.同时文章分析了不同有机质去除方法的优缺点,并探讨了本研究的发现对于光释光测年等需要进行有机质去除的实验的应用意义.     

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.     

Melt-Water-Pulse （MWP） events and abrupt climate change of the last deglaciation

The last deglaciation is characterized by massive ice sheet melting, which results in an average sea-level rise of -120-140m. At least three major Melt-Water-Pulse （MWP） events （19ka-MWP, MWP-1A and MWP-1B） are recognizable for the last deglaciation, of which MWP-1A event lasting from -14.2 to -13.7 ka B.P. is of the most significance. However, the accurate timing and source of MWP-1A event remain debatable and controversial. It has long been postulated that meltwater of the last deglaciaUon pouring into the North Atlantic resulted in a slowdown or even a shutdown of the thermohaline circulation （THC） which subsequently affected the global climate change. Accordingly, the focus of this debate consists in establishing a reasonable relationship between MWP events and abrupt climate change. Here we summarize a variety of geological and model results for the last deglaciation, reaching a conclusion that the major MWP events did not correspond with the rigorous stadials, nor always happened within climate reversal intervals. MWP events of the last deglaciation had very weak influences on the intensity of the THC and were not able to trigger a collapse of the global climate. We need to reevaluate the influences of the temporal meltwater variability on the global climate system.     

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。     

Interhemispheric climate links revealed by late-glacial cooling episode in southern Chile

Understanding the relative timings of climate events in the Northern and Southern hemispheres is a prerequisite for determining the causes of abrupt climate changes. But climate records from the Patagonian Andes and New Zealand for the period of transition from glacial to interglacial conditions--about 14.6-10 kyr before present, as determined by radiocarbon dating--show varying degrees of correlation with similar records from the Northern Hemisphere. It is necessary to resolve these apparent discrepancies in order to be able to assess the relative roles of Northern Hemisphere ice sheets and oceanic, atmospheric and astronomical influences in initiating climate change in the late-glacial period. Here we report pollen records from three sites in the Lake District of southern Chile (41 degrees S) from which we infer conditions similar to modern climate between about 13 and 12.2 14C kyr before present (BP), followed by cooling events at about 12.2 and 11.4 14C kyr BP, and then by a warming at about 9.8 14C kyr BP. These events were nearly synchronous with important palaeoclimate changes recorded in the North Atlantic region, supporting the idea that interhemispheric linkage through the atmosphere was the primary control on climate during the last deglaciation. In other regions of the Southern Hemisphere, where climate events are not in phase with those in the Northern Hemisphere, local oceanic influences may have counteracted the effects that propagated through the atmosphere.     

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).     

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.     

Model evidence for climatic impact of thermohaline circulation on China at the century scale

Based on transient simulation of the last deglaciation (significant global warming period) using a fully coupled model and sensitivity experiment, we show explicitly how the thermohaline circulation (THC) affects the climate of China, especially during periods of abrupt climate change. The simulated evolution of the Chinese climate was consistent with the paleoclimate record during the last deglaciation. For example, the whole Chinese region warmed significantly during the Bølling-Allerød warming event (BA). When the magnitude of the THC was reduced in the sensitivity experiment during BA, warming of the Chinese region was greatly affected. Our work shows that in addition to orbital forcing and greenhouse gases, the THC is an important factor influencing climate change in China at the century scale.     

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.     

川东北气田储层微量元素及沉积环境分析

海相沉积碳酸盐岩微量元素值域变化对了解古海平面起伏变化、气候条件和及古沉积海水温度具有较大的意义。以PG1井为检验井,取其储层岩芯样品共计122组,分析微相元素纵向演化特征,判识其沉积环境。实验分析表明:Ca/Mg比值从下至上逐渐增大、飞一~飞二段边缘浅滩相的Ca/Mg值(约1.2)小于飞三段的潮坪相的Ca/Mg值(约2.0),说明飞一、飞二段白云化程度高于飞三段;因此其白云化岩较发育,是优势储层。长兴-飞仙关组Sr、Mn、Fe元素含量分别位于80~500μg/g、7~90μg/g、0.6%~1.4%之间,具有高Sr,低Fe、Mn的特征,二者白云岩化流体具有同源性,反映其白云岩成因是在封闭、淡水没有参与的体系下形成。研究认为:川东北晚二叠世-早三叠世气候非常干旱赤热,强烈的蒸发作用导致沉积物中的孔隙水及海水盐度慢慢增大,Mg2+逐渐置换了水体中的Ca2+离子,不仅有利于碳酸盐岩发生准同生白云岩化作用,同时有利于在台地两侧高能边缘礁滩沉积环境中发生埋藏白云岩化作用。     

The timing of the last deglaciation in North Atlantic climate records

To determine the mechanisms governing the last deglaciation and the sequence of events that lead to deglaciation, it is important to obtain a temporal framework that applies to both continental and marine climate records. Radiocarbon dating has been widely used to derive calendar dates for marine sediments, but it rests on the assumption that the 'apparent age' of surface water (the age of surface water relative to the atmosphere) has remained constant over time. Here we present new evidence for variation in the apparent age of surface water (or reservoir age) in the North Atlantic ocean north of 40 degrees N over the past 20,000 years. In two cores we found apparent surface-water ages to be larger than those of today by 1,230 +/- 600 and 1,940 +/- 750 years at the end of the Heinrich 1 surge event (15,000 years BP) and by 820 +/- 430 to 1,010 +/- 340 years at the end of the Younger Dryas cold episode. During the warm B?lling-Aller?d period, between these two periods of large reservoir ages, apparent surface-water ages were comparable to present values. Our results allow us to reconcile the chronologies from ice cores and the North Atlantic marine records over the entire deglaciation period. Moreover, the data imply that marine carbon dates from the North Atlantic north of 40 degrees N will need to be corrected for these highly variable effects.