中国全新世的环境演化

全新世是地球历史中全新的一页，年龄为１０×１０３年，测定全新世年龄的最佳方法为１４Ｃ法，按照环境演化综合分析，全新世可以分为：前北方期（９３００ａＢＰ以前）、北方期（７５００－９３００ａＢＰ）、大西洋期（５０００－７５００ａＢＰ）、亚北方期（２５００－５０００ａＢＰ）、亚大西洋期（２５００ａＢＰ至现在）．全新世环境的主要特征是：现代人使用的新石器不断革新；全球性的大冰盖已经消逝，只有一些高山冰川和极地冰川，所以称为冰后期；海平面有多次的缓慢升降，总的趋势是不断升高；现代地壳运动是三大板块继续移动，并有多次的地震和火山喷发期；构造地貌和气候地貌的三大地貌单元已经形成；现代人的出现是全新世环境演化的最基本特征。这些特征的相互作用，构成了全新世的环境演化。     

5000年来秦皇岛至成山角海岸新构造运动分析

在列举全新世渤海海岸３１００－３９００ａＢ．Ｐ和５００－６００ａＢ．Ｐ．两期海平面遗迹资料的基础上，分析了沿海岸走向同期异地古少平面遗迹高度的变化规律，发现５０００ａ来郯庐断裂的活动对古海平面遗迹分布高度变化的影响，从而讨论了渤海海岸带的新构造特征。     

白龙江流域全新世泥石流与环境演变的初步研究

根据黄土－古土壤沉积序列研究和野外考察资料并结合放射性＾１４Ｃ测年,初步确定嘉陵江上游白龙江流域全新世泥石流共分三期,时代分别为７０００－６０００ａＢＰ、４０００ａＢＰ和２０００ａＢＰ。研究表明,泥石流频繁爆发于古气候由寒冷向温暖转换的波动时期。     

安固里淖自生碳酸盐碳氧同位素组成与环境

湖泊自生碳酸盐碳氧同位素变化是反映内陆湖泊水环境与气候环境的重要指标．通过在河北坝上安固里淖钻取沉积样柱,分样进行自生碳酸盐矿物类型分析和碳氧同位素分析,结合剖面的纹层年代以及粒度分析和易溶盐分析,对湖泊地区的全新世古环境进行了探讨：8507—7909 a B．P．,湖区气温较高,蒸发量大,夏季风先减弱随后增强．7909—7004 a B．P．,冬季风较强,气温低,蒸发量小,湖水盐度高;7004—5491 a B．P．,气温较高,降雨量大,湖水冰冻时间短,相当于大暖期鼎盛阶段;5491—4617 a B．P．,大气湿度低,气温低,冬季风较强,湖泊冰冻时间长,代表大暖期气候剧烈波动阶段;4617—574 a B．P．,冬季风较强,降水量少,河流补给少,湖泊冰冻时间较长;574 a B．P．至今,冬季风较弱,冰冻时间缩短,气候向暖湿发展．安固里淖自生碳酸盐碳氧同位素反映的环境变化与我国北方地区的全新世环境以及海平面的变化基本一致。     

中国北方农牧交错带全新世环境演变与全球变化

从本区发育的古土壤层，泥炭层、古风沙层，冻融褶曲层序列及其交错分布规律，以及湖岸阶地，湖面变化，古植被和介形类化石组合等方面资料都表面本区经历了早全新世冷干，中全新世温湿，晚全新世温凉偏干的气候变化，在千所尺度上表现在２０００ａ左右的气候变化周期区环境演变的干湿冷暖序列，即与中国东部和西部的环境演变具有相似性，也具有与全球变化的同步性特点。．     

河北坝上安固里淖风-水两相纹层的发现

安固里淖是河北坝上最大的内陆封闭湖泊,它位于张家口市张北县境内,地理坐标41°18'41°24'N,114°20'114°27'E.湖面海拔1312m左右,东南岸有季节性河流汇入,无泄水口.     

江苏建湖庆丰剖面全新世有孔虫与海面变化

对庆丰剖面全新统每５ｃｍ取一个样，进行有孔虫分析，划分了４个组合，讨论了海面变化７．５ｋａＢＰ以前，海面在０ｍ以下，但波动上升．７．５－４．０ｋａＢＰ，为高海面时期峰期出现于６．４ｋａＢＰ，５．６ｋｂＢＰ，５．１ｋａＢＰ，４．４ｋａＢＰ，最高海面在５．６ｋｂＡＰ前后，可达＋４ｍ左右。     

大布苏湖全新世沉积岩芯的粒度特征与湖面波动

大布苏湖为构造断陷的封闭湖盆,现代沉积环境的研究表明,自湖岸到湖心,其平均粒径２依次递减,钻孔岩 的粒度分析和年代测定揭示,全新世以来,大布苏湖有两次高湖面和两次低湖面时期晚全新世以来,湖面波动式下降,湖水浓缩而演变为我国东部地区罕见的盐湖。     

洛阳盆地全新世气候环境

根据伊洛河二级阶地皂角树剖面沉积物质的理化分析数据，推断洛阳盆了全新世气候环境特点是；早期冷湿，中期温暖湿润，晚期温暖半湿润，自１．２万ａＢ．Ｐ．以来存在９个温湿和９个干旱亚阶段。     

江苏龙虬庄新石器遗址环境考古研究

龙虬庄新石器文化遗址被列为１９９３年中国十大考古发现之一。根据＾１４Ｃ测年、器物排比法断代、孢粉、粒度、氧化物和磁化率等鉴定分析,探讨了遗址区古生民生存的环境。分析表明,龙虬庄地区在经历新仙女木寒冷期之后迎来了全新世暖期环境,１００００－７０００ａＢＰ间气候进入适宜期,但当时湿润程度尚不及此后７０００－６０００ａＢＰ间的新石器时期,当时 冬春季节应当有较大的风沙沉积。６３００ａＢＰ前后的气温可能更     

青藏高原中部色林错SL-1孔粒度参数指示的5.33 ka BP以来的水位变化

 对取自青藏高原中部色林错深水区的SL-1 孔开展年代学和粒度参数研究,以此重建了该湖5.33 ka BP 以来的水位变化.结果表明,5.33~4.25 ka BP 是一期较为稳定的高湖面期,湖面波动较小,始终维持在高湖面,后期(4.30～4.25 ka BP)湖面开始下降;4.25~2.20 ka BP,风力加强,湖面较上一期有所降低,属湖面降低期,风力作用的影响增加;2.20~1.90 ka BP,稳定的低湖面期;1.90 ka BP 至今,高湖面期.但有几期短暂而快速的湖面降低,湖面降低的持续时间一般为20~50 a,具有约0.10 ka和0.20 ka 的周期性,约0.20 ka 的准周期基本贯穿了色林错自5.33 ka BP 以来的湖面变化.这种周期在青藏高原冰芯氧同位素恢复的温度序列中也存在,说明在百年尺度上,温度对色林错的湖面变化有一定影响.     

鄂尔多斯盆地延长组地层底面古构造定量化演化及其石油地质意义

为定量化明确延长组地层在几个关键沉积期的底面凹凸构造面貌特征,基于鄂尔多斯盆地大量钻井等资料并采用盆地模拟技术,划分4个地层单元,即长10～长8、长7、长6～长4+5和长3～长1,定量化考察延长期湖盆在各层地层单元沉积末期的底面古构造特征。结果表明：长8沉积期末,地层底面构造高程整体表现为“东高西低、南高北低”的特征,主湖盆范围的构造等高线在-600 m以下;长7地层沉积期末,整体表现为“南高北低”的古地貌特征,主湖盆范围主要分布在盆地北部、构造高程达-1 150 m以下;长4+5沉积期末,凹陷区分布在盆地西北区域、分布范围和构造高程差变小、约为200 m;长1沉积末期,地层底面构造面貌格局整体表现为“东高西低”的古地貌特征,地层底面凹凸构造高程差为300～400 m。各沉沉积期底面凹凸构造发育,缓坡构造面貌区域是油藏分布的有利区。     

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.     

Hydrologic and climatic implications of a multi－disciplinary study of the mid to late Holocene Lake Eastern Juyanze

A mid to late Holocene exposure in a recently desiccated lake basin in western Inner Mongolia was inves-tigated with regard to palaeoenvir onmental changes and theoverall climatic conditions in NW China between 2.7 and 5.4 cal. ka BP. High lake levels of Lake Eastern Juyanze were recorded by ostracod assemblages, shell geochemistry and sedimentology between 5.1 and 4.1 cal. ka BP. Relatively bumid conditions and a relatively strong influence of the Asian monsoon are indicated by palynological data for the corresponding period. Lake levels decreased afterwards and short-term regressive events occurred at about 4.1, 3.8 and 3.4 cal. ka BP. The overall trend towards lower lake levels culminated in repeated episodes of desiccation of Lake East-ern Juyanze between 3.2 and 2.9 cal. ka BP, in phase with very arid conditions inferred from the palynological record.Individual regressive events as well as the rapid environ-mental fluctuations of Lake Eastern Juyanze at about 3.0 cal.ka BP were regarded as driven by mid to late Holocene summer monsoon fluctuations, supported by the Dunde ice core record.     

Environmental changes during early-middle Holocene from the sediment record of the Chaohu Lake,Anhui Province

A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River,Anhui Province,China.The timing scale is constrained by AMS 14 C dating method.Climate proxies such as pollen and grain size in the core are analyzed to reconstruct the environment changes at this site approximately between 9870 and 2170 cal.a BP.The results indicate that at the research area, the climate in the early-middle Holocene had evolved through 3 stages.From 9870 to 6040 cal.a BP, proxy records show a warm and dry climate with low water levels after the late-glacial period.During this stage,cool and dry events occurred at about 8910 and 6060-6030 cal.a BP.Then,between 6040 and 4860 cal.a BP,the climate was humid and vegetation was more flourishing in the Chaohu Lake Valley.The Holocene Optimum occurred at 5840-5500 cal.a BP in the Chaohu Lake,showing the best condition of water and heat.Elm Decline occurred at the period of 5380-4930 cal.a BP.Since 4860 cal.a BP,the climate was warm and dry through 2170 cal.a BP as shown in both pollen spectrum and grain-size histories.Two obvious dry events occurred in 3760 and 2170 cal.a BP,respectively.At 2170 cal.a BP,the water level of the Chaohu Lake reached the lowest as the lakebed possibly exposed. Such lake sediment observations are consistent with the historical records in this area.     

A carbon- and oxygen-isotope record of recent environ- mental change from Qinghai Lake, NE Tibetan Plateau

An understanding of natural climatic variability is essential for evaluating anthropogenic impacts on recent and future climate[1—3]. Due to the lack of lengthy instrumental records, such an understanding must be gained from natural archives of climate change. Palaeolimnological indicators of past lake levels may provide a sensitive record of changes in effective precipitation in closed basins. This approach is particularly relevant on the Tibetan Plateau, where instrumental records are very…     

A carbon－and oxygen－isotoperecord of recent environ－mental change from Qinghai Lake, NE Tibetan Plateau

A c. 300-year oxygen and carbon isotope record derived from fine-grained and ostracod carbonate from Qinghai Lake testifies to dramatic interannual to illterde-cadal linmologicai change. Fine-grained carbonates, whichare mainly authigenic, are likely to have formed in the epillmnion of the lake and their isotopic composition reflects the summer temperature and, more importantly, the isotopic composition of the near-surface waters, which is mainly afunction of evapor ative concentration. Ostracod shells aresecreted in the benthos of the lake, and their isotopic compo-sition reflects summer bottom-water conditions, together with fractionation effects, which may differ between species.Differences between contemporaneous values from authi-genic carbonates and ostracod shells may provide an indica-tion of stratification within the lake and variations in effec-tive precip itation over the northeast part of the Tibetan Pla-tcau over the past 300 years. A period of moderate evapora-tive concentration, from about 300 to 100 yr BP, was inter-rupted by a marked wet phase from-100 to 40 vr BP. which was in turn followed by a return to drier conditions in the most recent part of the record. The increase in δ^18O values in the latter part of the record accords well with instrumental records of lake-level lowering and salinity increase since about 1955 AD.     

达连海沉积物粒度特征及其古环境意义

利用达连海湖心浅井的粒度资料,分析了粒度组成、粒度频率曲线等粒度特征,并探讨了达连海粒度代表的古气候意义。结果表明,达连海沉积物频率曲线主要是正态单峰型,反映流水作用为主要沉积作用。湖心底部降水较多,湖面高,沉积物以细组分占绝对优势,频率曲线显示物源较单一,为深水沉积环境,但后期环境有所变化;中下部降水相对稀少,湖面降低,沉积物以粗组分含量增加,环境可能进一步恶化;中上部湖面上升,细组分含量增加,频率曲线显示物源由复杂变单一,为浅水沉积向深水沉积过渡环境;上部沉积物粗细间隔连续变化,频率曲线显示物源复杂,反映湖区环境进一步恶化,风砂活动频繁。沉积物粒度特征反映了达连海中全新世以来降水、流水和风力作用以及湖面水位高低的变化。达连海5 000多年来的古气候环境演化大致经历了5 600~5 100 cal a BP的湿润、5 100~2 500 cal a BP的干旱、2 500~800 cal a BP的偏湿和800 cal a BP以来的偏干4个阶段。     

新疆冰湖溃决灾害风险评价与预警研究

受全球气候变暖及人类活动的影响,冰湖溃决灾害已成为当前新疆地区经济可持续发展中的突出问题之一。利用1977(MSS)～2015年Landsat影像、2015年的Google Earth高精度影像和DEM等数据解译获取新疆冰湖的时空分布信息,并选取导致冰湖溃决的主要影响因子,运用MATLAB和SPSS等软件,利用西北地区已有冰湖数据作为训练样本拟合评价方程,建立了新疆冰湖溃决风险评价模型和基于BP神经网络算法的预警模型。结果表明:(1)1977年以来新疆三大山系中冰湖的数量和面积不断增加,冰湖数量上增加了62.0%,冰湖面积增长率为0.98 km~2·a~(-1),但增长率呈现逐年减小的趋势;(2)对分布在新疆范围内的17个典型冰湖溃决风险评价的结果显示:有5个冰湖为高危风险、5个冰湖为中等风险、7个冰湖为低等风险,新疆大约29%的冰湖需要进行实时监测。     

High－resolution precipitation variations in the Northeast Tibetan Plateau over the last 800 years documented by sediment cores of Qinghai Lake

Short cores of about 80-cm retrieved from three main basins of th e deepwater areas in Qinghai Lake,the largest inland enclosed lake in China, were studied. Sta-ble isotopes of authigenlc carbonates, grain-size, carbonate and organic matter content at 5-year resolution are used to reconstruct the climatic history over the last 800 years in the Northeastern Tibetan Plateau. Chronology was established according to 210^pb dating and 137^Cs methods and the core corrdation. It is found that cores from different deep basins of the lake can be well correlated. The sedimentary rate is highest in the western basin of the lake and lowest in the east.In the southern basin of the lake where the short core Qing-6is located, the recent average sedimentation rate is 0.1004cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data durine the last 800 years are consistent with the glacial accumulation record form the Dunde and Guliya ice cores. A dry climate lasted for 300 years from 1200 AD to 1500 AD, followed by a wet period from 1500 to 1560 AD. The two dry periods, 1560 to 1650 AD and 1780 to 1850 AD, were the results of southwest monsoon weakening. The effective precipitation generally increased since 1650 AD due to the strengthening of the Asian South-west Monsoon, resulting in a wet period until the 1950s. Ex-cept the early stage, the Little Ice Age on the Plateau is characterized b y increased effective moisture. Organic mat-ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta earbon-14 before the 1850s, indi-eating that the bioproductivity responds to solar activity.