Late Pleistocene paleoclimatic history documented by an oxygen isotope record from carbonate sediments in Qarhan Salt Lake,NE Qinghai–Tibetan Plateau

Late Pleistocene paleoclimatic variability on the northeastern Qinghai–Tibetan Plateau (NE QTP) was reconstructed using a chronology based on AMS ¹⁴C and ²³⁰Th dating results and a stable oxygen isotopic record. These are derived from lake carbonates in a 102-m-long Qarhan sediment core (ISL1A) collected from the eastern Qaidam Basin. Previous research indicates that the δ¹⁸O values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water, which in turn is a function of regional P/E balance and the proportion of precipitation that is monsoon-derived on the NE QTP. Modern isotopic observations indicate that the δ¹⁸O values of lake carbonates in hyper-arid Qaidam Basin are more positive during the warm and wet period. Due to strong evaporation and continental effect in this basin, the positive δ¹⁸O values in the arid region indicate drier climatic conditions. Based on this interpretation and the δ¹⁸O record of fine-grained lake carbonates and dating results in ISL1A, the results imply that drier climatic conditions in the Qarhan region occurred in three intervals, around 90–80 ka, 52–38 ka and 10–9 ka, which could correspond to late MIS 5, middle MIS 3 and early Holocene, respectively. These three phases were almost coincided with low lake level periods of Gahai, Toson and Qinghai Lakes (to the east of Qarhan Lake) influenced by ASM on the orbital timescales. Meanwhile, there was an episode of relatively high δ¹⁸O value during late MIS 3, suggesting that relatively dry climatic condition in this period, rather than “a uniform Qarhan mega-paleolake” spanning the ∼44 to 22 ka period. These results insight into the understanding of “the Greatest Lake Period” on the QTP.     

江西省鄱阳湖信江决口三角洲沉积特征及模式

利用实地考察、浅钻孔、探槽及卫星影像等方法,对鄱阳湖信江决口三角洲进行了系统研究。该决口三角洲是洪水冲破信江西岸天然堤流入附近的河漫湖泊形成的,其平面形态为鸟足状,总体延伸方向与主河道近垂直。在横切剖面上整个决口三角洲沉积体呈透镜状覆盖在早期的湿地或河漫湖泊沉积之上。鄱阳湖信江决口三角洲可分为3个亚相:决口三角洲平原、决口三角洲前缘和决口前三角洲。决口三角洲平原主要发育决口河道、决口天然堤、废弃决口河道和湿地,其中决口河道又可以进一步划分为决口水道、边滩、汊口滩;决口三角洲前缘主要发育河口坝、支流间湾。河漫湖泊规模小、深度浅、波浪能量弱,对河口坝和决口河道砂体的改造较弱,不易形成连片分布的席状砂;决口前三角洲不发育。决口三角洲沉积受河流作用和河漫湖泊作用的共同控制,其演化可以划分为主河道天然堤生长阶段、决口初期阶段、进积分汊阶段及分汊—废弃阶段4个阶段。     

A computational approach to Quaternary lake-level reconstruction applied in the central Rocky Mountains,Wyoming, USA

Sediment-based reconstructions of late-Quaternary lake levels provide direct evidence of hydrologic responses to climate change, but many studies only provide approximate lake-elevation curves. Here, we demonstrate a new method for producing quantitative time series of lake elevation based on the facies and elevations of multiple cores collected from a lake's margin. The approach determines the facies represented in each core using diagnostic data, such as sand content, and then compares the results across cores to determine the elevation of the littoral zone over time. By applying the approach computationally, decisions are made systematically and iteratively using different facies classification schemes to evaluate the associated uncertainty. After evaluating our assumptions using ground-penetrating radar (GPR), we quantify past lake-elevation changes, precipitation minus evapotranspiration (Δ_P−ET), and uncertainty in both at Lake of the Woods and Little Windy Hill Pond, Wyoming. The well-correlated (r = 0.802 ± 0.002) reconstructions indicate that water levels at both lakes fell at > 11,300, 8000–5500, and 4700–1600 cal yr BP when Δ_P − ET decreased to − 50 to − 250 mm/yr. Differences between the reconstructions are typically small (10 ± 24 mm/yr since 7000 cal yr BP), and the similarity indicates that our reconstruction method can produce statistically comparable paleohydrologic datasets across networks of sites.     

Unraveling rift margin evolution and escarpment development ages along the Dead Sea fault using cosmogenic burial ages

The Dead Sea fault (DSF) is one of the most active plate boundaries in the world. Understanding the Quaternary history and sediments of the DSF requires investigation into the Neogene development of this plate boundary. DSF lateral motion preceded significant extension and rift morphology by ~ 10 Ma. Sediments of the Sedom Formation, dated here between 5.0 ± 0.5 Ma and 6.2_− 2.1^+ inf Ma, yielded extremely low ¹⁰Be concentrations and ²⁶Al is absent. These reflect the antiquity of the sediments, deposited in the Sedom Lagoon, which evolved in a subdued landscape and was connected to the Mediterranean Sea. The base of the overlying Amora Formation, deposited in the terminal Amora Lake which developed under increasing relief that promoted escarpment incision, was dated at 3.3_− 0.8^+ 0.9 Ma. Burial ages of fluvial sediments within caves (3.4 ± 0.2 Ma and 3.6 ± 0.4 Ma) represent the timing of initial incision. Initial DSF topography coincides with the earliest Red Sea MORB's and the East Anatolian fault initiation. These suggest a change in the relative Arabian–African plate motion. This change introduced the rifting component to the DSF followed by a significant subsidence, margin uplift, and a reorganization of relief and drainage pattern in the region resulting in the topographic framework observed today.     

Geochronology and paleoenvironment of pluvial Harper Lake,Mojave Desert,California, USA

Accurate reconstruction of the paleo-Mojave River and pluvial lake (Harper, Manix, Cronese, and Mojave) system of southern California is critical to understanding paleoclimate and the North American polar jet stream position over the last 500 ka. Previous studies inferred a polar jet stream south of 35°N at 18 ka and at ~ 40°N at 17–14 ka. Highstand sediments of Harper Lake, the upstream-most pluvial lake along the Mojave River, have yielded uncalibrated radiocarbon ages ranging from 24,000 to > 30,000 ¹⁴C yr BP. Based on geologic mapping, radiocarbon and optically stimulated luminescence dating, we infer a ~ 45–40 ka age for the Harper Lake highstand sediments. Combining the Harper Lake highstand with other Great Basin pluvial lake/spring and marine climate records, we infer that the North American polar jet stream was south of 35°N about 45–40 ka, but shifted to 40°N by ~ 35 ka. Ostracodes (Limnocythere ceriotuberosa) from Harper Lake highstand sediments are consistent with an alkaline lake environment that received seasonal inflow from the Mojave River, thus confirming the lake was fed by the Mojave River. The ~ 45–40 ka highstand at Harper Lake coincides with a shallowing interval at downstream Lake Manix.     

近40年来气候变化对青海盐湖及其矿产资源开发的影响——以小柴旦湖为例

青海是中国盐湖主要分布区之一,蕴藏着丰富的矿产资源。文章以RS和GIS技术为基础,从20世纪70年代、90年代、2000年前后、2008~2009年和2013~2014年五期Landsat遥感影像中提取了青海面积大于10 km2的所有盐湖(不包括干盐湖),分析了其近40年来的变化趋势:总体上,盐湖总面积除在2000年前后有所减少外,基本上呈现增加的趋势;具体而言,2000年前后,萎缩的盐湖主要分布在柴达木盆地;其他时期均呈现全面扩张的趋势。在全球气候变暖的大背景下,通过分析青海地区11个气象台站的年平均气温、年降雨量和蒸发量数据,可知青海地区气候呈现了向暖湿方向转型的趋势,且2002年之后更为明显。最后,以青海省小柴旦湖为例,分析了湖泊淡化、矿产资源贫化对盐湖资源开发的影响,具体为:1资源开发成本升高、难度加大,甚至使一些处于工业开发临界品位的盐湖失去开发价值;2盐湖淡化条件下,锂等矿产资源有效提取技术亟待研发;3政府制定矿产资源开发政策时,需要对气候及盐湖的动态变化过程综合考虑。以上说明,青海地区的暖湿气候使盐湖大幅度淡化,给盐湖矿产资源开发带来了新的挑战。     

青海西部尕斯库勒盐湖沉积物中铀和钍地球化学特征探讨

文章以柴达木盆地西部尕斯库勒盐湖沉积物为研究对象,通过对钻孔沉积物和地表沉积物中铀和钍含量的研究,探讨了盐湖沉积物中铀和钍的地球化学特征。分析表明,钻孔沉积物中铀和钍之间存在明显的正相关关系。在横向上,随地表取样点逐渐远离湖表卤水,沉积物中铀和钍的含量先增高后又急剧降低,且受补给水铀含量影响大;在纵向上,同一个晶间卤水层或者碎屑物沉积层内铀含量垂直分异明显,铀含量随深度增加而递增。就沉积物中铀和钍的赋存形式而言,2/3的铀被黏土质点吸附,1/3的铀夹杂在盐类矿物中;而90%以上的钍被黏土质点吸附,10%以下的钍夹杂在盐类矿物中。干盐滩中毛细蒸发和淋滤等化学沉积分异作用造成盐湖沉积中心的沉积物铀含量相对较高。     

青海湖裸鲤内脏发光细菌的分离和鉴定

2009-2013年,从青海湖裸鲤内脏器官中共分离获得6株发光细菌,编号依次为Q1、Q2、Q3、Q4、Q5、Q6.这6株发光细菌细胞壁革兰氏染色均为阴性,细胞为杆状,大小为(0.5~0.8)μm×(1.0~1.5)μm,具有单极生鞭毛,有运动性.氧化酶和接触酶均呈阳性反应,能发酵葡萄糖产酸;吲哚试验和V-P试验均为阳性反应,能分泌淀粉酶、明胶酶、DNA酶,能将硝酸盐还原为亚硝酸盐.最适生长温度为20~25℃,最适生长pH为8.5~9.0.16S rDNA基因序列分析结果表明,6株发光菌与其亲缘关系最近的属为Vibrio(弧菌属),该属内和此次实验的6株发光菌亲缘关系最近的种Vibrio anguillarum(鳗弧菌)的16S rDNA序列相似值为99.57%.Biolog GenⅢ鉴定结果显示,该实验的6株发光菌在有氧条件下,在提供的71种碳源中,只能利用其中的30种,其中,糖类12种,氨基酸类5种,羧酸类4种,聚合物类2种,其他类7种.结合6株发光菌的形态学特征、生理生化特性、Biolog Gen III鉴定结果和分子生物学特性,将菌株鉴定为Vibrio anguillarum.该菌所具有的发光特性为首次报道.     

The Quantitative Assessment System for Brine Resource Industry Based on Sustainable Development Theory:a Case Study on Xitai-Jinaier Lake,Qinghai,China

正Salt lake resource is one of preponderant and strategic mineral resources in China.Some important chemical elements contained in brine are highly significant to both agriculture security and national security.Given the     

Microbial Processes in Stratified Lake Doroninskoe(Transbaikal Region)

正In recent decades,meromictic ponds attract the attention of researchers in different directions,because here the character of the physical,chemical and biological processes differ from those of typical mixing waters(Kuznetsov,1970;Hutchinson,1969).In Transbaikalia widely distributed soda and salt lakes with different salinity.Notable among them is Lake Doroninskoye,which has a pronounced stratification for a