Sedimentary archives of the French Atlantic coast (inner Bay of Vilaine,south Brittany): Depositional history and late Holocene climatic and environmental signals     

Philippe Sorrel  Bernadette Tessier  François Demory  Agnès Baltzer  Firas Bouaouina  Jean-Noël Proust  David Menier  Camille Traini 《Continental Shelf Research》2010,30(10-11):1250-1266

The late Holocene is of particular interest to our understanding of the evolution of coastal sedimentary systems because this period encompasses warmer and cooler periods, and rising sea level in northern Europe. Based on an approach combining AMS ¹⁴C, sedimentological and rock magnetic analyses on sediment cores complemented with seismic data collected in the macrotidal Bay of Vilaine (south Brittany), we document the depositional history of the inner bay coeval to the mid- to late-Holocene transgression in south Brittany. Correlation between sedimentary archives revealed the main sedimentary infilling phases during the last 6000 years. Four units (U1–U4) are recognized in the coastal sediment wedge of the system, corresponding to the stepwise marine invasion of the bay. We show that (1) marine inundation, due to the steep morphology of the bedrock, is diachronous between distal and proximal records. A time lag of ～1000 years is inferred over a distance of less than 5 km; (2) in the outer areas, the sedimentation has been condensed since 3000 years; (3) proximal estuarine archives offer the best record of sedimentary processes covering the last 2000 years, including the Medieval Warm Period (MWP).Correlations in proximal records in the Bay of Vilaine assess the connection between coastal sedimentary dynamics, climatic conditions and anthropogenic activities during the MWP. We match the preservation of clay deposits to increased river-borne suspended matter transported to the estuary probably as a result of accelerated land-use development (higher soil erosion) in the catchment area between ca. 880 and 1050 AD. Because the preservation of estuarine sedimentary successions is favoured when coastal wave sediment reworking is minimal, it is proposed that the prevailing climatic regime in south Brittany during the MWP likely resembled to that of the preferred negative phase of the North Atlantic Oscillation (NAO). Our data are fairly consistent with other late Holocene records from northern Europe including the Atlantic seaboard. However, they outline the difficulty in interpreting climatic and anthropogenic signatures in coastal sedimentary records where high-resolution chronologies required to unravel their respective influences are still missing.  相似文献   

Seasonal variability of community structure and breeding activity in marine phytal harpacticoid copepods on Ulva pertusa from Pohang,east coast of Korea     

Sung Joon Song  Jongseong Ryu  Jong Seong Khim  Won Kim  Sung Gyu Yun 《Journal of Sea Research》2010,63(1):1-10

Seasonal changes in community structure and reproductive status of phytal harpacticoid copepods in the shallow sublittoral bottom at two sites (Masan-ri and Guryongpo) in Pohang (Korea) are described monthly over a period of 1 year (October 1996 to September 1997). A total of 36 harpacticoid species was identified and the numerically dominant copepods were made up of the families Porcellidiidae and Tisbidae. Although the number of species did not show a seasonal trend, total harpacticoid density revealed a favorable distribution for the warmer season (spring and summer) at both sites. Multiple linear regression analyses showed that univariate indices such as density, evenness and diversity are closely associated with certain environmental parameters. For example, the dominant species fluctuated seasonally in abundance and their maximum densities were found to be temperature- (+ with Porcellidium ofunatense) and nutrient-dependent (+ with Scutellidium longicauda acheloides, + with Zaus unisetosus, and ? with P. wandoensis). In addition, the dominant species appeared to breed year round and their reproductive indices are significantly correlated with some environmental parameters such as temperature (?), pH (+), and phosphate (+). Three species (S. l. acheloides, P. wandoensis, and P. ofunatense) showed maximum density two or three months after their reproductive activity reached a maximum. Overall, the seasonal changes in a phytal harpacticoid community could be explained by combinations of environmental parameters supporting the complexity and biodiversity for this specific group of species in coastal ecosystems.  相似文献   

洋浦湾南浅滩-深槽-拦门沙近40年冲淤变化分析   总被引：1，自引：0，他引：1       下载免费PDF全文

林国尧  吴创收  陈斌 《热带海洋学报》2010,29(1):111-115

本文根据1965、1984、1999和2005的海图对比分析, 探讨了洋浦湾深槽、南浅滩以及口外拦门沙的冲淤变化, 得出: 1)1965—1984年之间, 南浅滩呈淤涨之势, 其西南部最大淤涨距离可达640m; 1984—1999年南浅滩出现了侵蚀, 这主要是由于洋浦湾波浪以及沿岸流的作用引起的; 1999—2005年, 靠近口门附近的南浅滩出现淤涨现象, 主要是由于洋浦湾口门附近水动力的影响作用; 但是目前整体基本上处于稳定的阶段。2)洋浦深槽段呈现出不同程度的西边坡淤涨, 东边坡侵蚀后退, 深泓断面缩窄、淤浅及东偏的趋势, 特别是剖面5的变化比较复杂,值得关注。3)口外拦门沙近几十年来呈现出不同的时空冲淤变化, 但是以淤积为主, 1965—2005年拦门沙总的淤积厚度达到1m左右, 但随着泥沙补给的减少, 这种淤积趋势也随着减少。  相似文献   

珠江磨刀门水道咸潮上溯加剧的原因   总被引：1，自引：0，他引：1  

韩志远  田向平  刘峰 《海洋学研究》2010,28(2):52-59

对磨刀门水道不同年份地形资料和多年枯季潮位资料进行了对比分析,结果表明:大规模的河床采砂,引起磨刀门上游河段河床大幅下切,河道深泓平均加深0.59~2.25 m,河槽容积平均增加8.91×106~12.11×106m3,使该河段枯季潮差增大,进潮量增加,潮汐动力增强,导致咸水界向上游河段推移;口门围垦整治后,磨刀门口门区由众多岛屿环抱而成的内海区变成人工导堤控制的"一主一支"两条水道,水域面积减少了80%,河槽容积减少了40%,深槽趋于顺直加深,使口门区的"调淡"作用消失,这是咸潮上溯的重要原因;根据多年水文频率分析,发生严重咸潮灾害时,西、北江枯季流量并非都是枯水流量,因此枯季上游来水量变化并不是近年来咸潮灾害加剧的主要原因。  相似文献   

长江河口沙坝全新统沉积特征和环境变迁     

吕全荣  曹敏  竹淑贞 《第四纪研究》1990,10(4):326

长江口崇明、长兴、横沙等岛屿是由全新世长江的河口沙坝孕育而成。晚更新世末长江门曾遭受了强烈的侵蚀,古河谷切割甚深。嗣后,在此地质背景上发育了河口沙坝,其全新世沉积相当完整。它们是研究长江河口三角洲形成史和沉积过程的有力证据。笔者着重探讨全新统的沉积环境变迁,旨在为研究长江三角洲发育及其经济区的开发提供地质依据。  相似文献   

卫星资料在上海浦东新区热力场分析中的应用   总被引：5，自引：1，他引：5       下载免费PDF全文

杨星卫  楼萌 《应用气象学报》1994,5(3):369-373

文章利用１９９２年春、夏、秋、冬四季６个时相的ＮＯＡＡ－１１／ＡＶＨＲＲ资料，在与上海区域行政图（边界以乡为单位）进行几何精度纠正的基础上，通过图象增强处理和多通道信息组合，提取上海市区和浦东新区的热力场分布特征，并用直接对比法，建立亮温。气温的相关关系，取得较好的效果。据上海温度分布图象分析，新区的两个热中心与工业群体区、建筑群体区相对应；市区的３个热中心与商业经济密集区及工业群体区相对应。   相似文献   

长江河口地区晚更新世晚期以来沉积环境的变迁   总被引：5，自引：0，他引：5       下载免费PDF全文

郭蓄民 《地质科学》1983,(4):402-408

本文所述长江河口地区,指河口附近的陆上部分,包括北部的三角洲平原,东部的滨海平原及西南部的冲积一湖积平原。全区除局部见有一些基岩山体以外,绝大部分为第四系覆盖区。整个第四系岩相层序比较复杂,反映沉积环境有过多次更替。  相似文献   

Channel morphology and its impact on flood passage, the Tianjiazhen reach of the middle Yangtze River   总被引：1，自引：0，他引：1  

Yafeng Shi  Qiang Zhang  Zhongyuan Chen  Tong Jiang  Jinglu Wu 《Geomorphology》2007,85(3-4):176

The Tianjiazhen reach of the middle Yangtze is about 8 km long, and characterized by a narrow river width of 650 m and local water depth of > 90 m in deep inner troughs, of which about 60 m is below the mean sea level. The troughs in the channel of such a large river are associated with regional tectonics and local lithology. The channel configuration plays a critical role in modifying the height and duration of river floods and erosion of the riverbed. The formation of the troughs in the bed of the Yangtze is considered to be controlled by sets of NW–SE-oriented neotectonic fault zones, in which some segments consist of highly folded thick Triassic limestone crossed by the Yangtze River. Several limestone hills, currently located next to the river channel, serve as nodes that create large vortices in the river, thereby accelerating downcutting on the riverbed composed of limestone highly susceptible to physical corrosion and chemical dissolution. Hydrological records indicate that the nodal hills and channel configuration at Tianjiazhen do not impact on normal flow discharges but discharges > 50,000 m³s^− 1 are slowed down for 2–3 days. Catastrophic floods are held up for even longer periods. These inevitably result in elevated flood stages upstream of prolonged duration, affecting large cities such as Wuhan and a very large number of people.  相似文献   

后工业化时期伦敦创意产业的发展   总被引：1，自引：0，他引：1  

褚劲风  崔元琪  马吴斌 《世界地理研究》2007,16(3):23-28,44

英国是世界上较早重视创意产业的国家，也是最早提出创意产业内容和定义的国家。伦敦作为英国政治、经济、文化中心，世界著名的国际经济中心城市，在工业化进程中、世界经济结构由“工业型经济”向“服务型经济”转化过程中，善于吸收历次产业革命成果，善于在产业经济、城市管理等方面不断创新，使其在一定时期内，始终处于大城市发展的前列，并被称为世界创意之都。因此，研究伦敦创意产业对探讨上海发展创意产业具有较大的现实意义。  相似文献   

制度变迁与房地产业发展-匈牙利的经验和启示     

黄 《世界地理研究》2007,16(2):45-51

东欧前社会主义国家匈牙利，经过数年市场化改革和体制转型，实现了国内经济的快速增长和国民生活的不断改善。本文基于匈牙利房地产业的发展背景和现状，探讨并分析了匈牙利政府在国内房地产业相关发展政策及管理举措方面可供借鉴的若干经验和启示。  相似文献