内蒙古萨拉乌苏河流域滴哨沟湾全新世早—中期湖相沉积的地球化学古气候响应

通过对毛乌素沙漠南缘萨拉乌苏河流域滴哨沟湾剖面沉积物粒度、有机碳含量(TOC)、碳酸盐含量、无机碳酸盐碳氧同位素组成等分析测试,在已有的大量年代测定数据基础上,重建了该地区末次冰期晚期到中全新世期间的古环境。分析表明,11 000～9 950aBP滴哨沟湾地区气候干凉,萨拉乌苏河受陕北高原降水和当地冰溶地下水补给;9 950～9 100aBP为全新世初温度、降雨增加时期,有效湿度较高,滴哨沟湾湖泊开始形成;9 100～5 850aBP气温继续上升,降雨增加,但相对湿度减小,该时期是滴哨沟湾湖泊发育最大时期,湖泊水体滞留时间较长;5 850～5 100aBP气温和降水开始下降,湖泊收缩;5 100～4 700aBP期间温度和降水继续下降,湖泊环境逐渐转变为沼泽环境;4 700～4 500aBP期间滴哨沟湾沙漠化,形成了古流动沙丘沙沉积,干旱化加强;而在4 500～4 380aBP时又一次短暂的温湿气候,在沙丘表层钙板隔水层之上形成了短暂的小规模积水;自4 380aBP之后,滴哨沟湾地区沙漠化,干旱状况持续到现在。

中德联合冬给措纳湖地区寒区环境变迁研究进展

青藏高原腹地的内陆湖及其湖相沉积物能够较真实地反映气候变化特征，在高原环境变迁研究中备受中外科学家的关注,2006年8月15日～9月10日，中德联合考察小组对青藏高原东北部的冬给措纳湖一带进行了第四纪冻土、地貌和地质学考察，并对湖岸阶地做了初步的数字高程分析,调查了冬给措纳湖底地形、地貌，采集了湖相沉积物样本,在湖的东岸和西岸发现多年冻土，湖泊西北山谷观察到古冰川活动遗迹,初步推测该湖是由断陷沉降形成,为进一步分析湖区气候和环境变迁，联合小组拟定2007年3月份钻取湖芯．

内蒙古巴丹吉林沙漠成因的粒度分析和热发光测年新证据(英文)

巴丹吉林沙漠位于中国内蒙古自治区的西部 ,是中国第三大沙漠。过去通常认为该沙漠中沙丘的可能沙源来自附近的各种沉积物和岩石 ,包括弱水河扇的沉积物 ,弱固结的二叠纪页岩、白垩纪砂岩和砾岩以及戈壁阿尔泰的古老岩石。根据对风成砂的粒度观测 ,有证据表明在沙漠内部的风成砂沉积朝东南方向具有较弱的但又确实的变细趋势。这与沙丘横脊线的SW -NE向排列以及坡面的南东指向是一致的。因此 ,可以认为西北部的弱水河冲积扇是巴丹吉林沙漠风成砂的最可能的沙源。在西北部风成床沙覆盖了较老弱水河扇起源的冲积物。这种沉积物的热发光测年范围在 190～ 10 0kaBP之间。由于测量中对沉积物漂白可能不完全以及对其中平均古水含量估算均存在不确定性 ,同时由于对沙漠该地区风成作用开始之前堆积的沉积物进行了测年 ,这一数据范围代表了最大的年龄。另外三个风成砂测年结果分别接近 133 6 6和 2 2ka ,代表有关巴丹吉林沙漠西北部风成作用开始的最小年龄。沙漠的沙丘高度平均为 2 0 0～ 30 0m ,但在东南部偶尔可达 4 5 0m。一些学者曾提出风成床沙覆盖了一个陡峭岛山突起的假说 ,来解释这些异常的空间。本次研究发现 ,在研究区之下是一个产状水平的白垩纪扇砾岩和砂岩的台地 。

Carbon and Oxygen Isotopic Compositions: How Lacustrine Environmental Factors Respond in Northwestern and Northeastern China

Surface lake sediments, 28 from Hoh XU, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine δ13C and δ18O values. Considering the impact factors, conductivity, alkalinity, pH, TOC, C/N and carbonate-content in the sediments, CI, P, S, and metal element ratios of Mg/Ca, Sr/Ca, Fe/Mn of bulk sediments as environmental variables enable evaluation of their influences on δ13C and δ18O using principal component analysis （PCA） method. The closure and residence time of lakes can influence the correlation between δ13C and δ18O. Lake water will change from fresh to brackish with increasing reduction and eutrophication effects. Mg/Ca in the bulk sediment indicates the characteristic of residence time, Sr/Ca and Fe/Mn infer the salinity of lakes. Carbonate formation processes and types can influence the 6~3C--~1So correlation. ~180 will be heavier from Mg-calcite and aragonite formed in a high-salinity water body than calcite formed in freshwater conditions. When carbonate content is less than 30%, there is no relationship with either 613C or 6180, and also none between δ13C and δ18O. More than 30%, carbonate content, however, co-varies highly to δ13C and δ18O, and there is also a high correlation between δ13C and δ18O. Vegetation conditions and primary productivity of lakes can influence the characteristics of δ13C and δ18O, and their co-variance. Total organic matter content （TOC） in the sediments is higher with more terrestrial and submerged plants infilling. In northeastern and northwestern China, when organic matter in the lake sediments comes from endogenous floating organisms and algae, the δ13C value is high. δ13C is in the range of-4‰ to 0‰ when organic matter comes mainly from floating organisms （C/N〈6）; in the range of-4‰ to 8‰ when organic matter comes from diatoms （C/N=6 to 8）; and -8‰ to -4‰ when organic matter comes from aquatic and terrestrial plants （C/N〉8）.

Carbon and Oxygen Isotopic Composition of Surface-Sediment Carbonate in Bosten Lake (Xinjiang,China) and its Controlling Factors

Bosten Lake is a mid-latitude lake with water mainly supplied by melting ice and snow in the Tianshan Mountains. The depositional environment of the lake is spatially not uniform due to the proximity of the major inlet and the single outlet in the western part of the lake. The analytical results show that the carbon and oxygen isotopic composition of recent lake sediments is related to this specific lacustrine depositional environment and to the resulting carbonate mineralogy. In the southwestern lake region between the Kaidu River inlet and the Kongqi River outlet, carbon isotope composition （δ^13C） values of the carbonate sediment （-1‰ to -2‰） have no relation to the oxygen isotope composition of the carbonate （δ^18O） values （-7‰ to -8‰）, with both isotopes showing a low variability. The carbonate content is low （〈20%）. Carbonate minerals analyzed by X-ray diffraction are mainly composed of calcite, while aragonite was not recorded. The salinity of the lake water is low in the estuary region as a result of the Kaidu River inflow. In comparison, the carbon and oxygen isotope values are higher in the middle and eastern parts of the lake, with δ^13C values between approximately ＋0.5‰ and ＋3‰, and δ^18O values between -1‰ and -5‰. There is a moderate correlation between the stable oxygen and carbon isotopes, with a coefficient of correlation r of approximately 0.63. This implies that the lake water has a relatively short residence time. Carbonate minerals constitute calcite and aragonite in the middle and eastern region of the lake. Aragonite and Mg-calcite are formed at higher lake water salinity and temperatures, and larger evaporation effects. More saline lake water in the middle and eastern region of the lake and the enhanced isotopic equilibrium between water and atmospheric CO2 cause the correlating carbon and oxygen isotope values determined for aragonite and Mg-calcite. Evaporation and biological processes are the main reasons for the salinity and carbonate mineralogy influence of the surface-sediment carbonate in Bosten Lake. The lake water residence time and the CO2 exchange between the atmosphere and the water body control the carbon and oxygen isotope composition of the carbonate sediment. In addition, organic matter pollution and decomposition result in the abnormally low carbon isotope values of the lake surface-sediment carbonate.

High-Resolution Records of the Holocene Paleoenvironmental Variation Reflected by Carbonate and Its Isotopic Compositions in Bosten Lake and Response to Glacial Activities

The Early Holocene paleoclimate in Bosten Lake on the northern margin of the Tarim Basin, southern Xinjiang, is reconstructed through an analysis of a 953 cm long core （BSTC2000） taken from Bosten Lake. Multiple proxies of this core, including the mineral components of carbonate, carbonate content, stable isotopic compositions of carbonate, Ca/Sr, TOC and C/N and C/S of organic matter, are used to reconstruct the climatic change since 8500 a B.P. The chronology model is made by nine AMS 14C ages of leaves, seeds and organic matter contained in two parallel cores. The climate was cold and wet during 8500 to 8100 a B.P. Temperature increased from 8100 to 6400 a B.P., the climate was warm and humid, and the lake expanded. The lake level was highest during this stage. Then from 6400 to 5100 a B.P., the climate became cold and the lake level decreased slightly. During the late mid-Holocene, the climate was hot and dry from 5100 to 3100 a B.P., but there was a short cold period during 4400 to 3800 a B.P. At this temporal interval, a mass of ice and snow melting water supplied the lake at the early time and made the lake level rise. The second highest lake level stage occurred during 5200 to 3800 a B.P. The climate was cool and wet during 3100 to 2200 a B.P., when the lake expanded with decreasing evaporation. The lake had the last short-term high level during 3100 to 2800 a B.P. After this short high lake level period, the lake shrank because of the long-term lower temperature and reduced water supply. From 2200 to 1200 a B.P., the climate was hot and dry, and the lake shrank greatly. Although the temperature decreased somewhat from 1200 a B.P. to the present, the climate was warm and dry. The lake level began to rise a little again, but it did not reach the river bed altitude of the Konqi River, an outflow river of the Bosten Lake.

A large Middle Pleistocene freshwater to oligohaline lake in the contemporary hyperarid Qaidam Basin （China）

The Qaidam Basin （NW China） at the northern margin of the Tibetan Plateau is one of the driest places on Earth with mean annual precipitation not exceeding 25 mm in the western central part. Flat salt plains and wind-shaped hills characterise the bare ground over thousands of square kilometres. In contrast to presentday conditions, remnants of ancient shorelines in high positions identified by Chen and Bowler （1986） and HiJvermann and Siissenberger （1986） about 20 years ago herald of a former large lake but were not investigated further till now. Here we present the results of microfossil analysis and optically stimulated luminescence （OSL） as well as uranium-series （TIMS） dating of sediments from a thick sequence of predominantly lake deposits in the eastern central Qaidam Basin. Based on abundant ostracod （micro-crustacean） shells from this sequence, we infer that a large lake of several metres depth at least maintained primarily fresh to oligohaline conditions in the late Middle Pleistocene.

Weak Summer Monsoon during the Early Holocene Inferred from the Dingxi Lujiagou Floodplain Lake-Eolian Sand Rhythm due to Solar Impacting

Objective Precipitation was the highest in the loess plateau during the Early Holocene 10-8 ka BP even to the period 10-3.0 ka BP in the Kesang cave stalagmite westward Tianshan,Xinjiang,based on large numbers of records from paleoclimatic proxies(An et al.,2000;Zhang et al.,2009;Zhang et al.,2018).However,we discovered at first time that floodplain lake-eolian stratigraphical rhythm complex kept in the Lujiagou of Dingxi,Gansu,which was important geological proof to indicate a weak summer monsoon transition period during the Early Holocene in the Chinese Loess Plateau.

A laminated tufa carbonate from the mid Holocene of the Qilian Mountains and its potential for palaeoclimate inferences

A mid-Holocene tufa section at 3,815 m altitude in the Qilian Mountains at the northeastern margin of the Tibetan Plateau was tested as a possibly important new climate archive. The tufa carbonate displays a distinct alternation of white and dark layers most probably representing annually deposited sparry and microgranular calcite which is formed during the warm and relatively wet summer and the drier and cooler spring and autumn season with an interruption of tufa formation during the freezing period. The δ^18O record of the tufa site comprises probably 357 years of annually deposited car-bonate-about 4, 000 years bejCore present, which indicates the prevalence of wetter climatic con- ditions in comparison to the present-day situation. This inference is confirmed by palynological data and lake-level reconstructions from a number of sites in the northern foreland of the Qilian Mountains, highlighting the large potential of longer tufa sequences for high-resolution palaeoclimate studies in the future.

Sub-Recent Sexual Populations of Limnocythere inopinata Recorded for the First Time from>3500 m Altitude on the Tibetan Plateau

The central and northwestern Tibetan Plateau region,also called＂Qiangtang Plateau＂（30°27＇25＂-35°39＇13＂N,83o41＇14＂-95°10＇46＂E）,is the highest and largest arcticalpine area of the Earth covering approximately 600,000km^2 with altitude ranging from 4600 to 5100 m a.s.l.（Song et al.,2012,Fig.1）.

内蒙古萨拉乌苏河米浪沟湾MIS 5以来生态环境演变特征

通过对毛乌素沙漠南缘萨拉乌苏河流域米浪沟湾地层中有机质含量(TOC)和饱和烃分布特征,以及沉积物中碳酸盐碳氧同位素组成的分析,讨论了该地区末次间冰期以来生态环境的演变特征和过程。MIS5阶段为森林草原环境,气候比较湿润,河流径流量较大;MIS4和MIS2阶段气候干冷,以沙漠堆积为主,但MIS2在16.9-18.4kaBP期间有一次持续大约1.5ka的古环境适宜时期,森林草原发育;MIS3阶段气候温暖湿润,森林草原环境,湖泊发育;全新世早中期总体上向干旱方向发展,湖泊动荡短暂,为较少森林的草原环境。到晚全新世以沙漠沉积为主,成为与目前生态环境相似的干草原环境。该地区的生态环境演变特征反映出主要受冬夏季风变化控制,但如果西风环流加强时期植被也相对发育。