Chrysophycean Stomatocysts in the Upper Pleistocene and Holocene Sediments from Lake Hovsgol, Northern Mongolia

Siliceous stomatocysts of chrysophyte algae, along with diatom frustules, are well preserved in bottom sediments of various water bodies. Analysis of microfossils from a core sample of the Upper Pleistocene and Holocene sediments from the southern part of Lake Hovsgol revealed 36 different morphotypes of chrysophycean stomatocysts. Some of them were attributed to species of the genera Mallomonas Perty, Chrysosphaerella Lauterborn., Paraphysomonas (Stokes) De Saedeleer, and Dinobryon Ehr.;20 morphotypes were described as novel. The abundance and diversity of stomatocyst morphotypes in the core sample varied depending on the age of sediments. The results obtained in the study broaden views on the biological diversity of microalgae and confirm that chrysophycean stomatocysts can serve as good environmental indicators in paleolimnological and paleoclimatic reconstructions.

Late Pleistocene and Holocene Glacier Extent in the Georgian Caucasus

This article presents the information of the Georgian Caucasus glaciation at the Late Pleistocene and Holocene period (~126,000-11,700 calendar years ago). Our primary aim was to numerically reproduce the ice extent deduced from geological and geomorphological mapping. We used the analog method with the 30 m resolution SRTM DEM (Shuttle Radar Topography Mission Digital Elevation Model). In addition, the rates of glaciation of those times are identified based on the stadial moraines and erratic boulders. The current investigation has revealed that in the Late Pleistocene, the central and western Caucasus characterized the highest glaciation, while the eastern Caucasus boasted the lowest glaciated area, and in the southern Georgia’s highland glaciation has almost the same form as there is in the Eastern Caucasus today. The longest glaciers were located in the Enguri (Nenskra ~36 km, Mulkhura ~35.1 km, Dolra ~34.5 km), Kodori (Sakeni ~25 km, Klichi ~20 km, Marukhi ~17.3 km) Rioni (Buba ~23 km, Kirtisho ~20.5 km, Jejora ~17.5 km) and Tergi (Devdoraki ~38.5 km, Suatisi ~32 km) river basins. We found, that topography thresholds related to the elevation and hypsometry of individual catchments controlled the gradient of the rate of glacier expansion in the domain at that time.

Phases of Environmental Evolution Indicated by Primary Chemical Elements and Paleontological Records in the Upper Pleistocene-Holocene Series for the Salawusu River Valley,China

Studies of lithology, sedimentary facies and the distribution regularity of SiO2 and Al2O3 contents and Al2O3/SiO2 ratio allow us to divide the Upper Pleistocene-Holocene Series represented by the MUanggouwan section in China＇s Salawnsu River valley into six segments： MGS1, MGS2, MGS3, MGS4, MGS5 and MGS6. The boundary ages for MGS1 （the Dishaogouwan and Dagouwan Formations）, MGS2 （the upper Chengchuan Formation）, MGS3 （the middle Chengchuan Formation）, MGS4 （the lower Chengchuan Formation）, MGS5 （most strata of the Salawusu Formation） and MGS6 （the bottom of the Salawusu Formation and the top of the Lishi Formation） correspond to those of MIS1, MIS2, MIS3, MIS4, MISS and MIS6, respectively, from deep sea sediments or continental glaciers. MGS5 can be subdivided into five subsegments （MGS5a, MGS5b, MGS5c, MGS5d and MGS5e） and the boundary ages of these subsegments correspond to those of MISSa, MISSb, MIS5c, MIS5d and MIS5e, respectively. Based on the paleoenvironment and paleoecology indicated by the primary chemical elements, fossil vertebrates, mollusks and pollen grains, we hypothesize that MGS1, MGS2, MGS3, MGS4, MGS5 and MGS6 and the subsegments of MGS5 match the corresponding stages for oxygen isotopes in the deep sea sediments and continental glaciers, and the substages of MIS5 in terms of climatic characters, further explaining the phenomena that determined the formation of the late Quaternary strata and the paleontology of the Salawusu River valley. These phenomena relate to fluctuations in the global climate （and particularly in the East Asian monsoon） during the glacial and interglacial periods.

LATE PLEISTOCENE—HOLOCENE RAPID UPLIFT AND EROSION IN TIBET: CONSTRAINTS FROM COSMOGENIC EXPOSURE AGE DATA

Tibet is the largest and highest plateau on the Earth (having 82% of the world’s land surface area falling >4km above sea level) attributed to the India and Asian convergence tectonics. Recently, high\|resolution digital topography data (Fielding et al., 1994) confirmed the earlier observations about flat erosional surfaces in the central part of the plateau (Jujin, et al., 1995) and suggested extraordinary flatness at a wide range of scales. Much of the Tibetan plateau across different accreted terranes has shallow slopes between 5°～10° and variation in relief of about 1 km, except in its marginal parts (Himalayan ranges; Kunlun mountains) where rough and high topography with intense fluvial dissections (variations in relief up to 7km) is quite frequent. However, in the southern and south\|central part of the plateau along the Pliocene\|Quaternary grabens, slopes generally steepen.

Geochemistry and Genesis of the Pampean and Post-Pampean Formations (Late Pleistocene-Holocene), Central and Northern Argentina Pampas and Its Adjacent Region—An Approaching Case Study

Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional conformable horizontal regolithic mantle-rock bed derived from them (the Pampean and Post-Pampean Formations), were geochemically analyzed. The focus of this study is placed on the application of geochemical parameter and signature analyses related with the aforementioned geological units, which are of subcontinental extension into South America. The encountered results show an outstandingly similar geochemical behaviour between them. The main conclusion is that regolithic mantle-rock beds were derived from the littoral shallow marine mudstone (silty-argillaceous) beds. This is in oposition to previous aeolian processes proposed early in the 50’s and later. These mudstone beds constitute important sections of the littoral shallow marine sequence beds (outcropping HST parasequence). Such regolitization proposed for the Pampean and Post-Pampean Formations predominantly developed in-situ during the Late Pleistocene and Holocene. The main erosional and mobilized agents were the surface free water (pluvial, fluvial and laminar water sheets) and vadose water. So, the wind flows and/or the immense air flow hurricanes are of insignificant sedimentological influence. Otherwise, there is not a proved appropiate sandy-silty reservoir for a reasonable support of the “aeolian hypothesis”, as well as clear aeolian structures settled in the regolithic mantle-rock bed. In spite of these lines of equality textural-structural evidence, the geochemical values for both major elements and trace elements, demonstrate that the Miocene heterolithic marine succession was the mother rock of the overlying regolithic mantle-rock bed, which was formed as an in-situ mantle-rock bed.

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.

Sediment distribution and provenance since Late Pleistocene in Laizhou Bay,Bohai Sea,China

There are three transgression-regression events and evolutions of the sedimentary environment by sea level changes since the Pleistocene in the southern section of the Bohai Sea, China. It is obvious that a multi-source fluvial delta sedimentary system may be more dominant in a sedimentary environment. Based on previous research and survey or historical data, we carried out studies on the division of sedimentary units, sedimentary facies analysis and strata division and comparison, which aim to establish the sedimentary stratigraph of Laizhou Bay. We focus on the sedimentary procession of the Laizhou Bay since the early Late Pleistocene. It can be divided into two glacial periods and three interglacial periods, corresponding to two regression and three transgression events in Laizhou Bay since Late Pleistocene. In 124.6-72.0 ka BP, 60.0-24.4 ka BP and 10.2-4.0 ka BP, three times warm-wet periods occurred, respectively corresponding to the Cangzhou transgression, Xianxian transgression, and Huanghua transgression. In 72.0-60.0 ka BP and 24.4-10.2 ka BP, two dry and cold periods, it was the continental sedimentary environment, corresponding to Wurm early glacier and Wurm late glacier. The results show:(1) Sediments have the characteristics of phase and stage under the terrestrial input of the Yellow River and middle-small rivers in the southern section of the Bohai Sea.(2) PI moved towards coastal in Cangzhou transgression strata in early Late Pleistocene. PI moved northward from land in Xianxian transgression strata in the late Pleistocene. PI moved further north in the Huanghua transgression strata in Holocene.(3) During the regressive period, the land source input increased and the estuarine or lagoon sedimentation developed, which manifested as progradational superposition.(4) During the transgressive period, it mainly developed shallow coastal sediment and transitionally formed regressive deposition to the south in delta/tidal flat deposition.

Earth surface processes and their effects on human behavior in monsoonal China during the Pleistocene-Holocene epochs

There is a wide diversity of landforms in China. The topography of three major ter- races, decreasing in height stepwise from west to east, was formed by the early Miocene. With the commencement of the Great Northern Hemisphere Glaciations （GHGs） and the glacial-interglacial cycles in the Pleistocene, thick loess deposits accumulated in north China, and fluvial terraces were formed and lakes expanded and contracted in eastern and central China. The earliest evidence of hominins in China is dated to ~1.7 Ma; they occupied the monsoon-dominated region for a long interval, until the late Pleistocene, ~50 ka. In this study, we investigated a large area rich in the relics and artifacts of early man. The results indicate that the early humans occupied riverine areas, especially medium-sized fluvial basins, and lake shores. Even in the relatively recent geological past, the occupation and abandonment of settlements were directly forced by the shifting of sand dune fields in the desert-loess transi- tional zone, which in turn was closely associated with variations in the monsoon climate and vegetation patterns. Our observations indicate that landforms were one of the main determi- nants of early human behavior, in that loess tableland, large alluvial plains, desert-Gobi areas, and the Tibetan Plateau, were not suitable environments for early human settlement. We infer that the early humans in China adapted their behavior to specific landforms and landform processes. The monsoon climate, which shapes the large-scale step-like pattern of fluvial landforms, promotes vegetation coverage and dominates soil formation, provides a crucial context for early human adaptation. The adaptation of early humans to earth surface proc- esses in East Asia is investigated for the first time in this study. Future investigations will provide further information that will increase our understanding of the linkage between early human behavior and landform processes in East Asia.

Mammal diversity during the Pleistocene-Holocene transition in Eastern Europe

Fossil record data on the mammal diversity and species richness are of importance for the reconstruction of the evolution of terrestrial ecosystems during the Late Pleistocene-Holocene transition.In Eastern Europe,the transformations during the Pleistocene-Holocene transition consisted mainly in changes in zonal structure and local fauna composition(Markova&Kolfschoten 2008).We investigated the species richness and the an­alogues of theα,βdiversity indexes(in the sense of Whittaker 1972)of large and medium size mammals for 13 climate-stratigraphic units dating to the Late Pleistocene and the Holocene,from the Hasselo Stadial(44-39 kBP)to the Subatlantic period and the present day.The biological diversity of the Last Glacial Maximum(LGM)and the Holocene thermal optimum was investigated in more detail using information about all mamma­lian taxa(PALEOFAUNA database;Markova 1995).One of our results show that theα,βdiversity values show only a negative correlation with the temperature conditions during the Late Pleistocene,the period that is char­acterized by the so-called‘Mammoth Fauna’complex.For the Holocene faunas the diversity indexes are nearly independent from physical conditions;theαdiversity index decreased and theβdiversity index increased.The relatively lowαdiversity and highβdiversity indexes for the present-day faunas are referred to the decrease of the population number of some forest species in historical time and the increase of the dominance of unspecial­ized species or the species connected with intra-zonal ecosystems.The study shows furthermore the occurrence of several East European‘centers’with a high mammal diversity,which are relatively stable during the Pleis­tocene-Holocene transition.The orientation of the boundaries between the large geographical mammal assem­blages depended,particularly in the northwestern part of Eastern Europe,on the expansion of the Scandinavian ice sheet.

Underestimated ^(14)C-based chronology of late Pleistocene high lake-level events over the Tibetan Plateau and adjacent areas: Evidence from the Qaidam Basin and Tengger Desert

The palaeolake evolution across the Tibetan Plateau and adjacent areas has been extensively studied, but the timing of late Pleistocene lake highstands remains controversial. Robust dating of lacustrine deposits is of importance in resolving this issue. This paper presents 14 C or optically stimulated luminescence(OSL) age estimates from two sets of late Quaternary lacustrine sequences in the Qaidam Basin and Tengger Desert(northeastern Tibetan Plateau). The updated dating results show:(1) the radiocarbon dating technique apparently underestimated the age of the strata of >30 ka BP in Qaidam Basin;(2) although OSL and 14 C dating agreed with each other for Holocene age samples in the Tengger Desert area, there was a significant offset in dating results of sediments older than ~30 ka BP, largely resulting from radiocarbon dating underestimation;(3) both cases imply that most of the published radiocarbon ages(e.g., older than ~30 ka BP) should be treated with caution and perhaps its geological implication should be revaluated; and(4) the high lake events on the Tibetan Plateau and adjacent areas, traditionally assigned to MIS 3a based on 14 C dating, are likely older than ~80 ka based on OSL chronology.

广西田东定模遗址发掘简报

定模遗址位于广西百色田东县布兵盆地内。2010-2011年间,广西民族博物馆和田东县博物馆对定模遗址进行了试掘,面积32 m^(2),出土了2108件石制品和少量动物化石。石制品类型包括石核、石器、石片、断块、碎片、未经加工的砾石等。石器以打制石器为主,磨制石器较少;类型多样,以砍砸器、刮削器为主,另有少量锯齿刃器、凹缺器等。原料主要来自附近的右江河滩,岩性以砂岩为主。石核剥片以锤击法为主,石器毛坯以砾石和石片为主。经过^(14)C测年分析,该遗址的距今年代为1.6~0.5万年。定模遗址的试掘为探索百色地区晚更新世末期至全新世初期石器文化面貌提供了新的材料,对于探讨华南及东南亚地区晚更新世石器技术演化提供了新的参考。

晚更新世以来珠江三角洲钻孔年代及沉积演化

珠江三角洲位于我国南海的北部大陆边缘,其两套海侵—海退旋回沉积已有数十年的研究历史。已有研究大多基于14C测年,存在由于测年上限(<45 ka)导致对全新世以前地层年代框架的低估问题;而光释光(OSL)测年在珠三角的全新世以前的地层年代已有应用,但已发表数据仍然较少。

渤海海域晚更新世—全新世的活动构造

利用在渤海最新获得的约5 000 km的浅层地震资料,发现在渤海海域发育大量晚更新世—全新世断裂和褶皱,进而对其分布、浅层结构、运动学性质和活动性进行了研究,绘制了渤海海域活动断裂分布图。研究结果表明:渤海晚更新世—全新世活动断裂主要走向为北北东向、北西向和近东西向,东西向断裂数量最多;断裂的形成受区域应力场和早期断裂的控制,而褶皱则以背斜居多,通常沿早期断裂带发育;就分布密度而言,辽东湾内断裂密度远小于其他海域,而同一构造单元其边界部位断裂密度大于单元内部;具继承性发展的断裂多具有复杂的破裂结构,破裂带剖面上呈耙形或"Y"字型,晚更新世沉积层变形明显;受断裂错动地层的形成时代表明,多数断裂的最新活动发生在晚更新世中期-晚期,部分断裂在全新世发生过活动;多数断裂具有明显正断拉张作用,而郯庐断裂带和张家口-蓬莱断裂带内次级断裂还可能具走向滑移分量;渤海浅层断裂的活动性与现代地震震中的分布具有较好的相关性,这对于渤海地震危险性评价具有重要意义。

中国季风沙区晚更新世以来环境及其变化

本文以对毛乌素沙漠萨拉乌苏河流域米浪沟湾地层剖面晚更新世—全新世砂丘与河湖相、古土壤互为叠覆的高分辨率的气候地层记录的认识出发,同时基于对中国北方现代冬春季节风沙、尘霾活动发生的区域性气候—地质过程的理解,将今释古,反演了该时期中国季风区沙漠沙地曾经历的27个沙漠扩缩的周期性变化,并认为该剖面风砂沉积是过去地质时代季风沙区乃至整个中国沙区类似由现代这种冬春季西伯利亚—蒙古反气旋风系即冬季风向南伸展导致的若干风沙风尘动态过程的结果,而河湖相和古土壤的发育则主要与季风沙区受惠于东亚夏季风的影响有关。

河套盆地西缘山前低台地沉积特征对“吉兰泰-河套”古湖消退过程及其控制因素的指示意义

河套盆地西缘与北缘发育一系列山前台地,台地沉积物记录了盆地环境变化。高台地沉积物记录了"吉兰泰—河套"古大湖形成过程,而低台地记录了古大湖的消退过程。盆地东部与西部低台地沉积特征不同,东部低台地由全新世冲洪积物组成,西部狼山山前低台地由晚更新世晚期—全新世(14 C年龄(15 260±60)a cal BP与(9 810±40)a cal BP)湖相沉积组成。低台地沉积特征及测年结果表明,1.5万年至1.0万年前后,河套盆地东部湖泊消失,而西部仍发育湖泊,古湖经历了自东向西的退却过程。古湖消退受盆地周缘断裂活动的差异性控制,1.5万年至1.0万年前后,盆地周缘断裂活动性总体上东强西弱,东部大青山山前断裂活动速率较高,大量碎屑物质进入盆地,呼和坳陷湖泊萎缩甚至消失,西部狼山山前断裂活动速率较低,进入盆地碎屑物质较少,临河坳陷大部分地区发育湖泊。

西藏佩枯错盆地第四纪湖相地层的厘定、划分和佩枯错群的建立

通过对环西藏佩枯错的T1—T16湖积阶地中湖相沉积的野外地质调查和实测剖面,对分布于盆地内的第四纪早更新世—全新世湖相地层进行了详细的研究和划分,重新厘定了该区早更新世—全新世的岩石地层单元,确立了生物地层和年代地层序列。首次建立了青藏高原第四纪早更新世—全新世湖相地层单位——佩枯错群(QP),佩枯错群由第四系下更新统拉洋组(Qp1l)、中更新统茫家冻组(Qp2m)、上更新统帮荣组(Qp3b)和全新统罗马仁布组(Qhl)4个组组成。为青藏高原湖泊演化、气候变化、古地理变迁的研究,以及第四纪地层的划分与对比等提供了新资料。

西藏纳木错晚更新世以来古降水量变化及其环境响应

通过对西藏面积最大(1940km2)和海拔最高(4718m)的大湖—纳木错的调查,发现纳木错周缘有大面积分布的湖相沉积。U系法和14C法测年结果表明,纳木错沿岸湖相沉积的时代为晚更新世和全新世。根据纳木错周缘不同时代湖相沉积物的范围分布的变化,探讨了湖泊演化,计算出纳木错流域古降水量。研究结果,本区自晚更新世以来气候环境由湿润转向干旱,自全新世以来降雨量呈下降趋势。

南阳盆地更新世以来的孢粉分析及其古气候记录

通过对南阳盆地的2个控制性钻孔样品进行精确的光释光定年、ESR定年和孢粉分析,结合现代表土植被概貌,重建了该区更新世以来的植被和环境演化历史。结果表明,早更新世,该区以草原和森林植被的草本植物为主,略大于木本植物,后期随着森林植被的发育,沉积环境相对稳定;中更新世主要表现为木本植物快速减少,蕨类也减少,其次是水生和陆生草本植物的相应增加;晚更新世,主要表现为次生的松属植被明显增加,水生植物明显减少;全新世,钻孔最上部藻类植物的大量增加,反映了水体面积较大,表明该时期该区水量丰沛。区域对比显示,该区从更新世到全新世气候温暖湿润,变化不大,未出现过冰期气候,各时段的气温差异不大,但干湿变化比较明显。气候环境演化特征与典型的东亚季风影响区有着明显差异,这与南阳盆地局部的环境有密切关系。

江苏江都市大桥镇晚更新世晚期—全新世有孔虫动物群的发现及其地质意义

在江苏省江都市ZKA4钻孔孔深4.0～42.6 m岩心段中发现有孔虫化石,鉴定识别出有孔虫38属56种,其中9个未定种,根据有孔虫动物群在钻孔剖面上的分布规律,建立了3个有孔虫化石组合,自上而下为:Ammonia beccarii(Linne)vars.-Orbulina universa组合,Ammonia beccarii(Linne)vars.-Cibicidoides bellus组合和Ammonia beccarii(Linne)vars.-Lagena sreiata组合,并将钻孔的有孔虫化石组合与国内其他地区相同层位的有孔虫化石组合对比,将滆湖组的时代厘定为晚更新世晚期,将如东组的时代厘定为全新世。据光释光测年结果,ZKA4钻孔有孔虫动物群始现年龄(孔深42.6～42.8 m)约为(14.2±0.6)ka,该有孔虫动物群是末次冰期冰后期大海侵的产物,此次海侵可细分为两个次一级旋回,影响区域达江苏省西部。

晚更新世晚期以来古尔班通古特沙漠南部的气候环境演化

本文通过对古尔班通古特沙漠南部的一个钻孔剖面沉积物沉积物沉积特征的分析 ,证明该沙漠南部地区在晚更新世晚期气候相对寒冷 ,并有两次气候偏湿波动 ;全新世时期 ,该区气候以温暖干旱为主 ,全新世中期有一次明显的气候偏湿波动。