ROBUST: The ROle of BUffering capacities in STabilising coastal lagoon ecosystems     

Rutger de Wit  Lucas J. Stal  Bente Aa. Lomstein  Rodney A. Herbert  Hans van Gemerden  Pierluigi Viaroli  Victor-Ugo Cecherelli  Francisco Rodríguez-Valera  Marco Bartoli  Gianmarco Giordani  Roberta Azzoni  Bart Schaub  David T. Welsh  Andrew Donnelly  Ana Cifuentes  Josefa Antn  Kai Finster  Lise B. Nielsen  Anne-Grethe Underlien Pedersen  Anne Turi Neubauer  Marina A. Colangelo  Sander K. Heijs 《Continental Shelf Research》2001,21(18-19)

“Buffer capacities” has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that “buffering capacities” can be depleted progressively, and, therefore, we make a distinction between current and potential “buffering capacities”. We have applied this concept to understand the limited “local stability” in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant–microbe interactions in the seagrass meadows.  相似文献   

Emplacement of xenolith nodules in the Kaupulehu lava flow,Hualalai Volcano,Hawaii     

J. E. Guest  P. D. Spudis  R. Greeley  G. J. Taylor  S. M. Baloga 《Bulletin of Volcanology》1995,57(3):179-184

The basaltic Kaupulehu 1800–1801 lava flow of Hualalai Volcano, Hawaii contains abundant ultramafix xenoliths. Many of these xenoliths occur as bedded layers of semi-rounded nodules, each thinly coated with a veneer (typically 1 mm thick) of lava. The nodule beds are analogous to cobble deposits of fluvial sedimentary systems. Although several mechanisms have been proposed for the formation of the nodule beds, it was found that, at more than one locality, the nodule beds are overbank levee deposits. The geological occurrence of the nodules, certain diagnostic aspects of the flow morphology and consideration of the inferred emplacement process indicate that the Kaupulehu flow had an exceptionally low viscosity on eruption and that the flow of the lava stream was extremely rapid, with flow velocities of at least 10 m s^-1 (more than 40 km h^-1). This flow is the youngest on Hualalai Volcano and future eruptions of a similar type would pose considerable hazard to life as well as property.  相似文献   

北京西山寒武纪海相红层的分布与时代     

李明  林宝玉 《地质学报》2022,96(6):1895-1921

本文参照北京西山及国内外寒武系相关地层资料，在古生物学和地层学研究的基础上，对北京西山寒武纪海相红层进行了初步研究。在西山寒武纪地层中，共识别出14层(套)海相红层，分别为：早寒武世下苇甸组1层B∈RB1(沧浪铺期)；早—中寒武世早期3层B∈RB2、B∈RB3及B∈RB4(馒头期—毛庄期)；中寒武世中期3层B∈RB5、B∈RB6及B∈RB7(徐庄期)；中寒武世晚期1层B∈RB8(张夏期)；晚寒武世早期2层B∈RB9、B∈RB10(崮山期)；晚寒武世中期3层B∈RB11、B∈RB12、B∈RB13(长山期)：晚寒武世晚期1层B∈RB14(凤山期)。所有14层海相红层形成于陆表海浅水环境，它们均属陆棚红层。红层分布模式说明，它们的形成与其附近的古陆有关。依据海相红层及其上下层位中所含的三叶虫化石，本文初步论述了各海相红层的大致时代，并与其他地区的同期海相红层进行了对比。此外，本文还讨论了山西东部寒武纪海相红层的层序和全球早寒武世沧浪铺期海相红层的广布事件。  相似文献   

地层学研究方法的增新──自然γ测井     

冯宝华 《地层学杂志》1994,18(4):262-266

系统而扼要地介绍有关火山事件岩层中放射性元素和４０Ｋ含量及自然γ测井的基础知识及应用概况。对缺乏古生物化石和疑难地层有条件时可采用酸性火山事件岩层及其自然γ测井资料作为地层学研究的补充方法。  相似文献   

地震多元参数综合解释煤层结构     

崔若飞  耿力 《煤田地质与勘探》1993,21(3):43-46

利用时间域和频率域的多元地震参数解释煤层结构属于岩性地震勘探范畴。将该技术用于陕北大保当勘探区,配合地质研究,成功地确定了2~(-2)煤层的结构变化情况,确定的煤层分叉线同单纯依靠地震解释或地质推断的煤层分叉线比较,精度明显提高。  相似文献   

Discovery of Trace Fossils from the Sinian—Cambrian Boundary Beds in Eastern Yunnan and Their Significance for Global Correlation1     

Yin Jicheng  Li Daqing  He Tinggui 《《地质学报》英文版》1993,6(4):429-442

Abstract There are abundant and highly varied trace fossils in the Sinian—Cambrian boundary beds in eastern Yunnan. Collections from 27 sections and their study give altogether 45 ichnogenera and 87 ichnospecies. Among them, 2 ichnogenera and 7 ichnospecies are new, and 31 known ichnogenera and 38 known ichnospecies first found in the region. According to their order of appearance in the boundary beds and their assemblage features, the trace fossils in the Sinian—Cambrian boundary beds in the region may fall into 4 trace fossil assemblage zones in ascending order. In the paper they are correlated with those in the equivalent horizons abroad and their geological significance is discussed preliminarily.  相似文献   

江西省丹霞地貌特征及其控制因素探讨     

陈留勤  郭福生  邵崇建  楼法生  李斌  黎广荣  郄海满  吴知勇  姜勇彪  刘富军 《地质学报》2022,96(11):4023-4037

江西省的丹霞地貌主要分布在30余个白垩纪红层盆地中，总共有228处，数量位居全国之首，以鹰潭市龙虎山世界地质公园的丹霞地貌最为典型和知名。根据形态特征，将江西省的丹霞地貌划分为山峰、陡崖、崩积体、峡谷、洞穴及其他微地貌等六大类。燕山构造旋回晚期（主要是白垩纪），在地壳伸展拉张的构造背景下，江西省形成了一系列北东走向的陆相断陷盆地，从盆地边缘到中心依次沉积红色冲 洪积扇相砾岩、河湖相砂岩和泥岩，在信江盆地的中部还发育沙漠相风成砂岩。红层岩相是丹霞地貌演变的基本物质基础，对丹霞地貌的分布具有重要影响。在喜马拉雅构造旋回中，这些红层被构造抬升、切割，随后在风化、流水侵蚀及崩塌等外动力地质作用下形成了红色陡崖坡及一系列侵蚀地貌，即丹霞地貌。以龙虎山世界地质公园核心景区仙水岩为例，用面积高程积分方法对江西省丹霞地貌的演化阶段及其主控因素进行了分析。仙水岩景区地层出露一致，丹霞地貌整体处于老年早期的残丘阶段，地貌侵蚀程度较强；由于水系溯源侵蚀，景区内不同部位地貌的演化阶段、类型及面积高程积分值（HI值）不尽相同。本文对江西省丹霞地貌基本特征及控制因素的分析和总结研究将加深对各类丹霞地貌成因的理解，推动丹霞地貌国际化进程，也为其他湿润气候区丹霞地貌地质遗迹的合理利用提供参考。  相似文献   

Paleomagnetic results of the Cretaceous marine sediments in Tongyouluke, southwest Tarim     

SHEN Zhongyue  CHEN Hanlin  FANG Dajun  DING Jinghai  ZHANG Shiben  HUANG Zhibin & LI Meng . Department of Earth Sciences  Zhejiang University  Hangzhou China  . Tarim Oil Field Company  PetroChina Company Limited  Korla  China 《中国科学D辑(英文版)》2005,48(3):406-416

Southwest Tarim (hereafter SW Tarim) is one of afew areas that well developed Cretaceous marinesedimentary rocks in China [1]. The Cretaceous marinesediments are stretched in front area along the Tian-shan and Kunlun Mountains. Toward the center ofTarim Basin, the Cretaceous sediments are buried bygreat thickness of Tertiary and Quaternary sedimentswith little exposure. Compared with the Cretaceousterrestrial strata of north Tarim, the Cretaceous marinestrata of SW Tarim continue and d…  相似文献   

“白垩纪大洋红层——海洋/气候响应”研究进展综述   总被引：2，自引：0，他引：2  

IGCP/秘书处 《地学前缘》2005,12(2):69-80

“白垩纪大洋红层”是中国学者提出并开拓的白垩纪研究新方向。在其所领导的两个国际地质对比计划项目(IGCP463/494)的推动下,“白垩纪大洋红层”所蕴含的古海洋与古气候意义,正引起越来越多的学者的重视。特别是近几年召开的学术会议对“白垩纪大洋红层”研究起到了很好的推动作用: (1)在2002 年度IGCP463 项目启动会议上,对“白垩纪大洋红层”的研究现状进行了初步的交流,制订了项目研究的总体目标和未来五年工作计划,并考察了亚平宁—阿尔卑斯—喀尔巴阡沿线的大洋红层;(2)2003 年度的IGCP463 工作会议和IGCP494 启动会议,不仅积累了大洋红层研究的资料,而且将白垩纪大洋红层研究推进到白垩纪中期;(3)2004 年度两个项目的工作会议,以及通过在第32 届国际地质大会特别讨论会的工作,进一步推进了大洋红层的研究,并将“白垩纪大洋红层”研究介绍给广大的国际地球科学界;(4)在欧洲地球科学联盟2005 年会上,“白垩纪大洋红层”研究体现出了多学科共同参与的可喜现象。回首近几年来的研究历程可以发现,“白垩纪大洋红层”研究已实现了如下转变:(1)从区域性研究到全球对比综合研究的变化;(2)从由中国科学家单独研究变为多个国家的科学家申请到项目和经费共同研究;(3)从举办IGCP项目学术年会快速向国际大会或  相似文献   

Upper Cretaceous oceanic red beds in southern Tibet:Lithofacies,environments and colour origin   总被引：6，自引：0，他引：6  

Jansa Luba 《中国科学D辑(英文版)》2006,49(8):785-795

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