ENVIRONMENTAL CHANGES IN THE EASTERN CHINA DURING THE LATE PLEISTOCENE

The environmental changes during the Late Pleistocene were more obvious in the eastern China than in other areas at the same latitude, which either between northern and southern, or between land and sea of the eastern China were mostly non-synchronous. The transitional period prior to the last glaciation came about in the northern part of the eastern China about 115,000 yr. ago. The desert environments of the inland of the north China were developed both in the glacial maximum and in the warm interglacial period, but the loess accumulation mostly took place during the glacial period. The sand dunes and the periglacial solifluctions in the lower Changjiang (Yangtze) River region were formed during the last glacial period. The event of lowest surface temperature occurred at 98,000 yr. B.P. and 59,000 yr. B.P. in the northern part of the South China Sea but not during the full-glacial stage. The phenomena mentioned . above were the result of the following reasons that the paleo-environmental changes in

Biogeochemistry of sedimentary organic matter in the Yongjiang River estuary in the southern part of Hangzhou Bay,China,since the Late Pleistocene

A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.

East Asian summer monsoon changes in subtropical China since late Pleistocene:Evidence from the Ailuropoda-Stegodon fauna

Previous studies on the amplitude of East Asian summer monsoon(EASM)changes mainly focused on northern China(represented by the Loess Plateau).However,a rare investigation centered on the subtropical zone of southern China,where the important route for EASM moved northward or southward,especially addressing a lack of the research on mammals.The Ailuropoda-Stegodon fauna is a representative mammal fauna in southern China since the late Pleistocene.It indicates the southern mid-subtropicaltropical forest environment with tropical climate characteristics,and its southward or northward movements in the subtropical zone imply the changes of EASM intensity.Based on previous research,combined with the species characteristics and distribution range of the Ailuropoda-Stegodon fauna with tropical animals during the marine isotope stage 5(MIS5),MIS3,MIS2,and MIS1 Megathermal periods,this paper mainly investigates its evolution and the fluctuations of EASM.The conclusions include:(1)The distribution geometric centers in the MIS5,MIS3,MIS2,and MIS1 Megathermal periods are(26°14′N,111°22′E),(24°35′N,107°30′E),(22°48′N,112°01′E),and(26°19′N,112°25′E),respectively.(2)Compared with the MIS5 period,the EASM of the MIS3 and MIS2 moved 180 km and 380 km southwards,and that of the MIS1 Megathermal period moved about 10 km northwards.The EASM movement indicated by the fauna migration happened synchronous with the climate records of stalagmites in subtropical China,the sporopollen from eastern China,and oxygen isotopes from Sulu Sea.They also correspond to the peaks and valleys of the total solar radiation at 35°N in the winter half-year.This suggests that the migrations of the Ailuropoda-Stegodon fauna are consistent with the changes of the global climate,and the driving force is mainly from the changes of total solar radiation at 35°N in the winter half-year.

Paleomagnetism and paleoclimate change in the South China Sea since the late Pleistocene

Signal processing techniques of cross-correlation, power spectral analysis and cross-power spectral analysis are used to determine the relationships between paleomagnetic properties and the oxygen isotope record of the South China Sea during the late Pleistocene. On the basis of correlation tests between the δ18O time series of cores V3 and A15 with the paleomagnetic properties of core SCS01, five events of susceptibility and intensity of natural remanent magnetization are identified as glacial events corresponding to δ18O positive events. The magnetic properties of the sediments which are independent of the geomagnetic field are sensitive climatic indicators which have frequencies corresponding to the Milankovitch orbital parameters.

Environmental evolution in the salt-water intrusion area south of Laizhou Bay since late Pleistocene

The south coastal plain of Laizhou Bay is one of the typical salt-water intrusion areas in China, the occurrence and development of which was closely related with the palaeoenvironment evolution. Systematic analyses of pollen, foraminifera and grain size composition based on ^14C and luminescence dating from two sediment cores were performed for the purpose of understanding the salt-water intrusion in the coastal plain of Laizhou Bay from the perspective of environmental evolution since late Pleistocene. It could be classified into seven evolution stages since 120 kaBP： 120-85 kaBP was a transition period from cold to warm; 85-76 kaBP was a period with warm and wet climate having swamp lakes developed in the lower reaches of the Weihe River, south coastal plain of Laizhou Bay; 76-50 kaBP was characterized by grassland vegetation and coarse sediments in terrestrial environment, which was the early stage of Dali Ice-Age; 50-24 kaBP was a period with alternate sea deposition in the south coastal plain of Laizhou Bay; 24-10 kaBP was the late stage of Dali Ice-Age with coldest period of Quaternary, the south coastal plain of Laizhou Bay was dry grassland and loess deposition environment; 10-4 kaBP was another warm and wet climate period, sea level was high and regressed at 4 kaBP; and has been the modern sedimentary environment since 4 kaBP. Among the three warm stages, including 85-76 kaBP, 50-24 kaBP and 10-4 kaBP, corresponded to late Yangkou, Guangrao and Kenli seawater transgression respectively. The duration of the latter one in south coastal plain of Laizhou Bay was longer than that in west coast of Bohai Sea and east coast of Laizhou Bay. The three periods of seawater transgression formed the foundation of salt-water intrusion in this area.

ENVIRONMENTAL CHANGES SINCE LATE PLEISTOCENE IN ESTUARINE PLAIN OF JIULONG RIVER, FUJIAN PROVINCE

Based on the evidences of lithostratigraphy, palynology, micropaleontolopy and geochronology, paleoenvironments since the Late Pleistocene in the study area have been reconstructed. One of the most important inferences is that two marine transgressions have occurred, one in Wurm Sub-interglacial and the other Postglacial. The former had caused the study area to be in an estuary-bay envirment over the transgression maximum, with a sea level of no less than 10 m below present; foe latter reached its maximum over the Atlantic stage, with sedimentary environments of estuary-bay, hay or shallow sea, and the sea level arrived at the highest elevation in about 6 - 5 ka B.P. Furthermore, it is notable that, during the Late Wurm Glacial, the study area area had principally been in an estuary-bay environment, although the climate, like many other areas, turned cold and dry, It reflects a general trend of crustal subduction in Jiulong Estudrine Plain over this pened.

Three abrupt climatic events since the Late Pleistocene in the North China Plain

Based on the data from 121 boreholes(9552 samples) and the distribution pattern analysis of foraminifera,ostracods,pollen,spores,wooly rhinoceros,elephants,water buffalo and beachrocks in time and space,three abrupt climate change events since the Late Pleistocene are recognized in the North China Plain.These climatic events caused three very warm periods and two severely cold periods.During the two warmest periods,the mean temperature was about 7℃ higher than at present,and during the two extreme cold periods,the mean temperature was some 6℃ lower than today.Moreover,the last warm period was in the Middle Holocene;its mean temperature was 3℃ higher than now in the region.

Geochronology and Geochemistry of Late Triassic Intrusive Rocks in the Xiuyan Area,Liaodong Peninsula,Eastern North China Craton:Petrogenesis and Implications for Lithospheric Thinning

The timing and mechanisms of lithospheric thinning and destruction of the North China Craton(NCC)remain controversial,and the overall geodynamics of the process are poorly understood.This paper documents Late Triassic igneous rocks including monzogranite,gabbro,and diorite from the Xiuyan District on the Liaodong Peninsula in the eastern NCC,which have LA-ICP-MS zircon U-Pb ages of 229.0±0.4 Ma,216.2±0.9 Ma,and 210.6±2.0 Ma,respectively.Monzogranite shows high-SiO_(2) adakite affinity,negative ε_(Hf)(t)values(-20.6 to-17.9),and old T_(DM2) ages(3.53-3.29 Ga),suggesting that their parental magma was derived from thickened Paleoarchean mafic lower crust and minor mantle materials that were also involved their generation.Gabbro is ultrapotassic,strongly enriched in LREEs and LILEs,depleted in HFSEs,and has evolved zircon Hf isotopes with negative ε_(Hf) of -10.04 to-5.85 and old T_(DM2) ages(2.59-2.22 Ga).These are diagnostic signatures of a crustal component,but their high contents of Mg O,Cr,Co,Ni indicate that the primary magma originated from enriched mantle.Diorite is enriched in LILEs and LREEs,depleted in HFSEs(with negative Nb,Ta,and Ti anomalies),and contains negative ε_(Hf)(t)values(-13.64 to-11.01).Compared with the gabbro,the diorite is relatively enriched in Nb,Ta and HREEs,and also contains younger T_(DM2) ages(2.11-1.94 Ga),suggesting that the diorite was formed by mixing between ancient lower crust-derived felsic magmas and asthenospheric mantle-derived magmas.Field observations,geochronology,geochemistry,and zircon Lu-Hf isotopes indicate that Late Triassic magmatism and tectonic activity resulted from deep subduction of the Yangtze Craton beneath the NCC in the Xiuyan area.This phase of tectonic activity was completed in the eastern NCC by the Late Triassic(216 Ma),and was subsequently followed by lithospheric thinning that began in the Late Triassic.

Speculation on the timing and nature of Late Pleistocene hunter-gatherer colonization of the Tibetan Plateau

Hunter-gatherer populations in greater northeast Asia experienced dramatic range expansions during the early Upper Paleolithic (45—22 ka) and the late Upper Paleolithic (18—10 ka), both of which led to intensive occupations of cold desert environments including the Mongolian Gobi and northwest China. Range contractions under the cold, arid extremes of the Last Glacial Maximum (LGM, 22—18 ka) may have entailed widespread population extirpations. The high elevation Qinghai-Tibetan Plateau is significantly more extreme in both climate and environment than either the Gobi or the Siberian taiga forests, and provides an ideal setting to test fundamental models of human biogeog- raphy in the context of regional population fluctuations. The area is presently occupied primarily by nomadic pastoralists, but it is clear that these complex middle Holocene (<6 ka) economic adaptations were not a necessary prerequisite for successful colonization of the high elevation Plateau. Exploratory field-work in 2000—2001 has established that Upper Paleolithic hunter-gatherers were present on the Qinghai-Tibetan Plateau by at least 12 ka and possibly much earlier. A speculative model for the colonization process is developed and preliminary archaeological data in support of the model are presented.

中国南方猩猩化石的研究进展

在精确年代测定基础上,研究中国南方新发现的猩猩牙齿化石,是近年来猩猩化石研究的特色。中国南方猩猩化石的发现和研究深化了学术界对更新世猩猩分类、大小演化及其与环境变化之间关系的认识。本文梳理了中国南方更新世代表性的含猩猩化石遗址和猩猩化石的最新研究成果。目前发现的猩猩牙齿化石和年代学结果表明,猩猩最早出现于早更新世早期的中国南方,并持续到了晚更新世,以猩猩魏氏种(Pongo weidenreichi)为代表。在中更新世晚期时,猩猩戴氏种(Pongo devosi)可能首次出现在中国南方。猩猩魏氏种与猩猩戴氏种之间的关系还需要更多的化石证据来证实。更新世猩猩牙齿大小演化表现出明显的阶段性,猩猩牙齿变小主要出现在中更新世。猩猩牙齿大小的这种演化关系可能与中国南方草原环境的出现和扩张有关。

Comparison of Middle-Late Holocene environment between the coastal areas of South China and California

1 Geographical setting The coast of South China, on the west Pacific front in low latitudes, is a coast of marginal sea on continental plate with a wide shelf and under tropical and south-subtropical climates: with great rainfall and many rivers running into sea. The river activities play an important role in coastal development.

94–9ka察尔汗盐湖的气候环境演化过程

本文依托柴达木盆地中东部察尔汗盐湖沉积中心102 m长钻孔(ISL1A)岩芯,应用AMS14C和不平衡U系测年方法建立了年龄-深度框架,对岩芯开展了元素地球化学分析,利用主成分分析提取影响察尔汗盐湖沉积物化学组成的2个主控因子:入湖径流量因子和湖泊蒸发量因子,结合孢粉、粒度、沉积物中石盐含量等环境代用指标,分析讨论察尔汗盐湖晚更新世湖泊波动与环境变化过程。结果表明:察尔汗古湖在晚更新世经历多次淡化期和咸化期,94–52 ka期间察尔汗古湖为微咸水-半咸水湖,湖泊入湖径流量较大,湖区植被为草原/荒漠草原植被;约52 ka各指标均反映了察尔汗古湖环境发生了显著变化,湖泊入湖径流量减小,蒸发量增加,湖泊由咸水湖退缩演化为盐湖,湖区植被由草原/荒漠草原演替为荒漠草原/荒漠。34–24 ka期间察尔汗盐湖入湖径流量增加,湖泊有所扩张,但湖水盐度较高;24–9 ka期间在冷干气候背景下,湖泊退缩演化为干盐湖。环境指标所指示的察尔汗盐湖波动演化过程得到了柴达木盆地及其周边地区其他环境变化记录的支持。

晚更新世以来呼伦湖地区孢粉植物群发展与环境变迁

呼伦湖是我国纬度最高的湖泊。晚更新世以来，由于气候冷暧干湿的多次波动，湖相及河流、风成为主的水上沉积交替变化。通过对该区东露天煤矿沉积剖面１１３块样品进行系统孢粉百分比及浓度分析，划分出８个孢粉组合带。结合１４Ｃ测年数据，确定了该区２００００年以来的气候演变序列。其中１３０００—１０９００ａＢ．Ｐ．的温凉湿润期相当于北欧的Ｂｏｌｌｉｎｇ—Ａｌｌｅｒｏｄ暖期，ＹｏｕｎｇｅｒＤｒｙａｓ冷期大约在１０９００—１０６００ａＢ．Ｐ，约１０６００—１００００ａＢ．Ｐ．为全新世初期升温期。全新世中期（７２００—５０００ａＢ．Ｐ．），气候温暖湿润，年均温可能比目前高３℃左右。此后气候开始向干凉化方向发展。孢粉组合可以与北欧及邻区孢粉资料相比较，并为我国气候地层学的研究提供了新的背景材料。

西藏佩枯错盆地晚更新世以来的孢粉组合特征及其古气候意义

西藏佩枯错盆地晚更新世以来河湖相沉积剖面的孢粉分析显示,该地区在晚更新世早期的127—72kaB.P.时期,气候温和湿润,植被以针阔叶混交林为主;至66—56kaB.P.时期,气候转变为温凉略干,植被转为疏林草原;在56—49kaB.P.时期,气候温凉潮湿,植被又转为针阔叶混交林为主的森林草原;而在49—46kaB.P.时期,气候温和偏干,植被转为疏林草原;在46—31kaB.P.时期,气候寒凉湿润,植被表现为温度进一步下降的疏林草原;在31—15kaB.P.时期,环境向寒冷方向发展,植被转为高寒草原;自11kaB.P.(全新世初期)开始,气候由温暖偏干转变为温凉偏湿,植被由灌丛草原转变为森林灌丛草原。这表明自晚更新世以来,该区气候环境是在逐渐变干的总趋势上,经历了多次明显的冷暖与干湿波动。

中国晚中新世陆相哺乳动物群序列:陕西蓝田的新证据(英文)

自 2 0世纪 60年代 ,陕西蓝田地区就以连续的晚新生代地层及丰富的哺乳动物化石而成为研究中国晚新生代哺乳动物与地层划分对比的经典地区之一。李传夔等 ( 1 984)根据灞河组发现的哺乳动物化石建立了灞河期 ,并与欧洲的Vallesian期对比。邱占祥等( 1 990 ,1 995)认为化石证据不充分 ,而将其与保德期合并。近年来 ,黄土高原三趾马红粘土大量的年代学资料表明 ,红粘土沉积最早可能开始于约 8Ma前。因此 ,狭义的保德期可能只代表了晚中新世晚期 ,晚中新世哺乳动物分期的再划分问题又重新被提出。自 1 997年以来 ,我们课题组在蓝田地区共发现 52个化石地点 ,其中的 2 6个含有哺乳动物化石 ,大哺乳动物化石标本共计 1 666件。经过详细野外地层测量 ,绘制了综合地层剖面 ,并将主要含哺乳动物化石的地点对比标定到综合地层剖面上。经过对各门类化石的初步研究 ,以及对已有化石材料的初步修订 ,到目前为止 ,陕西蓝田灞河组共计发现哺乳动物化石 45种 ,蓝田组 2 0种。新的化石证据表明 ,灞河组发现的哺乳动物化石组合完全不同于典型意义上的保德三趾马动物群。大哺乳动物化石以灞河三趾马与贾氏三趾马为代表 ,牛科化石组合在种级甚至属级上有明显的区别。大量的陕西转角羚羊 ,小型的Protoryx。

西藏纳木错晚更新世湖滩岩

通过对西藏海拔最高、面积最大的纳木错湖周缘的第四纪环境演变调查研究与1:25万当雄幅区域填图工作,在环纳木错沿岸发现了一种与湖泊演化有关的湖相沉积岩石——湖滩岩。本文首次对纳木错周缘发育的湖滩岩进行了描述。从湖滩岩水准仪测定的保存高度看,它已构成1.5～8.3m、8.3～15.6m、14～19.9m、18.7～25.8m等四级较明显的湖滩岩阶地。湖滩岩由亮晶砂屑藻凝块灰岩、泥晶白云质砾岩和方解石胶结含砾岩屑砂岩等组成,岩石具粗砂状、含砾砂状、角砾状结构,块状构造,基底式胶结。其铀系全溶样品的等时线年龄测定结果表明,湖滩岩形成于18.7±3.8～29.3±2.7ka BP的晚更新世中晚期。本文根据岩矿鉴定,并结合沉积相、岩相组合等特征,探讨了湖滩岩的形成机理。为研究该区湖泊演化、气候变化、古地理变迁及第四系划分等提供了新资料。

陕西黄土高原晚更新世环境变化

岐山剖面孢粉分析表明，黄土高原东南部晚更新世植被与气候变化可分为７ 个阶段和１３ 个小阶段。其中末次冰期的３ 个冷干阶段和２ 个温湿阶段被分别命名为秦家寨、岐山、坡头冰阶和尚家坡、杨家湾间冰阶。冰阶的植被以温带森林草原为主，间冰阶的植被以落叶阔叶林为主。

陕西关中晚更新世黄土-古土壤序列特征及其记录的古环境变迁

陕西关中盆地的泾阳南塬和西安东郊席王晚更新世黄土剖面底部的S_1古土壤是由4层古土壤及与其相间的3层黄土构成,L_1黄土是由3层黄土及夹于其间的两层古土壤构成。这是目前发现的黄土高原晚更新世黄土-古土壤序列保存较好的剖面。两剖面的地层结构、磁化率曲线和地球化学组分反映出的12个温湿、冷干气候变化阶段可以归纳为6个气候变化旋回。这是目前建立的我国黄土高原晚更新世(130—10ka B P)较短时间尺度的气候变化模式,它与经典的深海氧同位素记录曲线是不相一致的。

晚更新世末以来苕溪河道变迁

据苕溪流域现有的地层学、考古学、地方志等资料考证,其河道变迁可追溯至晚更新世末,演化过程具有阶段性:1)18—15 ka BP,苕溪河道剧烈下切,东、西苕溪独流入海,西苕溪顺地势东北流入海,东苕溪东流入杭州湾;2)15.0—7.5 ka BP,苕溪河道下切能力减弱,沉积作用加强,东、西苕溪独流入海.8.7 ka BP以前,西苕溪流进钱塘谷地后注入杭州湾,8.7 ka BP之后,西苕溪流进古太湖湾;3)7.5—4.0 ka BP,苕溪河道沉积作用明显,河口发生淤积,5.0 ka BP以前,东、西苕溪独流入海,5.0 ka BP之后,西苕溪流入古西太湖,东苕溪在余杭东改道北流,入一泻湖,并在5.0—4.0 ka BP期间3次大规模改道;4)4.0 ka BP以来,苕溪河道沉积作用明显,东、西苕溪合流入太湖,且中下游段改道频繁.苕溪河道变迁始终与本区地理环境演化密切相关,包括对海面升降变化的响应、与太湖发育及古地形演变等的互动.

晚更新世末期—全新世早期的气候突变和中国农业的起源

农业起源和气候变化关系的研究,对于目前人类社会对全球变暖的响应与适应有一定借鉴意义。农业起源需具备一定环境和人口压力、适合的地形、适宜野生稻和黍(粟)生长的气候环境、有从事高级采集-农业活动的文化背景等条件。根据环境演变和考古资料,晚更新世末期―全新世早期,中国经历了一系列气候变化事件。气候变化刺激了农业的形成与发展,新仙女木时期巨大的环境-人口压力促进了农业的产生;8.2 ka BP气候干冷事件推动了农业的扩张。根据农业起源时期的地理环境和典型遗址分布,结合农业起源需具备的条件,综合分析发现:太行山南麓、汾渭谷地一带应该是北方黍(粟)作农业起源地,长江中下游平原―南岭北麓过渡地带应该是南方稻作起源地。