The influence of a flood event on phytoplankton succession   总被引：1，自引：0，他引：1  

Fredy Elber  Ferdinand Schanz 《Aquatic Sciences - Research Across Boundaries》1990,52(4):330-344

The effect of the August 1987 River Reuss flood event on the phytoplankton biocoenosis in Lake Uri (Urnersee, part of Lake Lucerne, Switzerland) was investigated firstly by comparing biological, chemical and physical data sampled before the event with equivalent data sampled after the event; and secondly by comparing the phytoplankton succession in 1987 with that occurring in the floodfree year 1989. As a consequence of the flood, the physical and chemical environment of the phytoplankton was found to have undergone a change which resulted in an alteration in the composition of the phytoplankton community. The phytoplankton community existing previous to the flood event, which had been dominated byTabellaria fenestrata sensu Husted 1930 (K-strategist), was replaced by a biocoenosis characterized mainly by various species of flagellates, which represent a typical spring successional stage (r-strategists). After the externally-imposed perturbation, the return to stable physical and chemical conditions was followed by the re-establishment of the successional stage which had existed before the flood (termed reversion by Reynolds, 1980).  相似文献   

High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years     

Yunchao HAO Zhigang GUO Dejiang FAN 《中国地球化学学报》2006,25(B08):13-13

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.  相似文献   

Real eukaryotes and precipitates first found in the Middle Riphean stratotype, southern Urals   总被引：1，自引：0，他引：1  

V. N. Sergeev  Lee Seong-Joo 《Stratigraphy and Geological Correlation》2006,14(1):1-18

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萨拉乌苏河流域萨拉乌苏组沙丘砂沉积特征   总被引：7，自引：1，他引：7  

欧先交  李保生  靳鹤龄  吴正  温小浩  董光荣  曾兰华  欧阳椿陶  杨艺  刘宇飞 《地理学报》2006,61(9):965-975

萨拉乌苏河流域米浪沟湾剖面萨拉乌苏组含7层古流动沙丘砂、4层古固定-半固定沙丘砂.对这些沙丘砂的沉积构造观察以及粒度、扫描电镜和常量化学元素分析结果表明：（1）这些沙丘砂具有与现代沙丘砂相似的风成沉积构造特征;（2）粒度及其参数——Mz、σ、Sk和Kg,以及主要化学组分SiO2、Al2O3和TOFE也与现代沙丘砂相近;（3）Mz-σ、SiO2-Al2O3＋TOFE散点图和概率累积曲线显示这些沙丘砂与萨拉乌苏组中的河湖相、古土壤差别明显,而与现代沙丘砂一致;（4）石英砂颗粒具有良好的磨圆以及碟形坑、新月形坑、麻坑、上翻解理薄片、硅质沉淀和硅质裂纹等表面结构特征,反映其曾受持久的风力搬运作用.沉积构造、粒度、石英砂颗粒表面结构和化学元素等多个方面具备了与现代沙丘砂类似的风成特征,证明这些沙丘砂的成因是风成的.  相似文献   

Seasonal Diatom Variability and Paleolimnological Inferences – A Case Study     

Dörte Köster  Reinhard Pienitz 《Journal of Paleolimnology》2006,35(2):395-416

The seasonality of physical, chemical, and biological water variables is a major characteristic of temperate, dimictic lakes. Yet, few investigations have considered the potential information that is encoded in seasonal dynamics with respect to the paleolimnological record. We used a one-year sequence of diatoms obtained from sediment traps and water samples, as well as the sedimentary diatom record covering the past ca. 1000 years in Bates Pond, Connecticut (USA), to investigate which variables influence the seasonal distribution of diatoms and how this can be used for the interpretation of the fossil record. The seasonal patterns in diatom assemblages were related to stratification and, to a lesser extent, to nitrate, silica, and phosphorus. During mixing periods in spring and autumn, both planktonic and benthic species were collected in the traps, while few lightly silicified, spindle-shaped planktonic diatoms dominated during thermal stratification in summer. Changes in fossil diatom assemblages reflected human activity in the watershed after European settlement and subsequent recovery in the 20th century. A long-term trend in diatom assemblage change initiated before European settlement was probably related to increased length of mixing periods during the Little Ice Age, indicated by the increase of taxa that presently grow during mixing periods and by application of a preliminary seasonal temperature model. We argue that the analysis of seasonal diatom dynamics in temperate lakes may provide important information for the refinement of paleolimnological interpretations. However, investigations of several lakes and years would be desirable in order to establish a more robust seasonal data set for the enhancement of paleolimnological interpretations.  相似文献   

塔里木盆地东河砂岩沉积和储层特征及综合分析   总被引：21，自引：0，他引：21  

贾进华  张宝民  朱世海  朱运成  李占银 《古地理学报》2006,8(3):339-352

东河砂岩是一套海侵初期的沉积产物，东河砂岩不是一个等时沉积体，相当于晚泥盆世晚期至早石炭世早期沉积，具体沉积时间各地有差异。由于东河砂岩是覆盖广泛的海侵初期沉积，因此具有海侵初期填平补齐的特征，其沉积相决定于海侵的速度、沉积物的供给和海侵前的古地貌。塔北地区受塔北古隆起的阻挡，海水在古隆起周围滞留时间较长，又有较粗粒的物源供给，其沉积产物主要是滨岸海滩沉积；塔中地区由于地形复杂，沉积类型也比较复杂，底部砾岩段有河流相沉积，而块状砂岩段和砂砾岩段有河口湾和滨岸海滩沉积，不同段在成分、分选性和粒级上有较大的差异；而其它低平地区主要是海侵期快速的滨岸和陆架沉积。受沉积因素影响，东河砂岩有效储层的分布具有地域性；除沉积因素外，低的地温梯度和短期的深埋藏是优质储层发育的重要控制因素。  相似文献   

吉尔嘎朗图凹陷宝饶洼槽下白垩统层序地层与沉积体系     

易定红  石兰亭  曹正林  贾义蓉  李林波 《华东地质学院学报》2006,29(1):22-26

运用高分辨率层序地层学原理和方法,通过对钻井和地震资料的综合分析,在二连盆地吉尔嘎朗图凹陷下白垩统中识别出1个超长期基准面旋回(二级层序)SSC1和5个长期基准面旋回(三级层序):LSC1,LSC2,LSC3,LSC4,LSC5,分析了各旋回的发育特征。识别出五种类型的沉积体系:滨浅湖近岸水下扇、较深水湖浊积扇、滨浅湖扇三角洲、滨浅湖辫状河三角洲和河流沉积体系,并在等时地层格架内分析了各基准面旋回的沉积体系构成和储层砂体的发育情况。综合分析生、诸、盖条件后认为,在垂向上,LSC3旋回为本区最有利的储集层段,在平面上,本区的油气勘探应主要寻找宝饶构造带辫状河三角洲前缘砂体,主要储层砂体类型为前缘分流水道砂和前缘席状砂。  相似文献   

新疆库木库里盆地演化   总被引：3，自引：0，他引：3  

肖爱芳  黎敦朋  李新林  周小康  杜少喜 《陕西地质》2005,23(1):59-69

通过对新疆库木库里盆地的地质调查，渐新统一上新统识别出冲积扇、河流、湖泊三角洲、湖泊四种沉积相、六种亚相、十种微相；具有盆地演化早、晚期碎屑成熟度较低，盆地演化中期碎屑成熟度较高的特征；通过物源分析得出盆地演化早期碎屑物质来自盆地南部，晚期碎屑物质来自盆地西部，碎屑物质均来源于再旋回造山带构造背景区，并具有早期南高北低、晚期西南高东北低的古地理格局；盆地分析表明新疆库木库里盆地从渐新世形成大致经历了渐新世一早中新世盆地萌芽、中中新世一晚中新世盆地的生长发育、上新世盆地萎缩三个演化阶段。  相似文献   

鄂尔多斯西缘前陆盆地上古生界沉积相特征研究   总被引：3，自引：0，他引：3  

赵培坤  纪友亮 《新疆地质》2005,23(2):152-157,i006

在层序地层学研究的基础上，对鄂尔多斯盆地西缘逆冲构造带上古生界进行了详细的沉积相研究．分析出该地发育了6种沉积相，分别为碳酸盐潮坪相、障壁砂坝-泻湖相、河口湾相、三角洲相、河流相、湖泊相．并按上古生界识别出的2个二级层序，推测出沉积相的平面展布特征，总结出鄂尔多斯盆地西缘地区，晚古生代沉积演化经历了拗拉槽再活动背景下的裂谷海湾充填、陆表海充填和内陆坳陷充填3个发展阶段．并结合构造、物源供给、海侵、古气候等条件分析了鄂尔多斯西缘前陆盆地上古生界沉积相演化的控制因素．  相似文献   

陈家庄凸起北坡古近系层序地层特征及沉积体系     

庄博  刘玉琴  张建中 《新疆地质》2005,23(2):164-168

陈家庄凸起北坡发育了多种类型的储集体．根据岩心、钻井和测井资料，以层序地层学理论和方法为指导，从分析、识别层序的主要界面，如层序界面、初始湖泛面、最大湖泛面等入手，对陈家庄凸起北坡古近系层序、准层序和体系域进行了划分．通过钻井层序分析与地震层序解释，在层序地层分析的基础上，对沉积体系进行了研究．指出本区发育的低位域水下扇、低位域复合扇、湖扩展体系域滨岸沉积和高位域三角洲沉积等，是进行岩性油藏勘探的有利目标．  相似文献