试论武汉地区构造演化与岩溶发育史   总被引：5，自引：4，他引：1  

罗小杰 《中国岩溶》2013,32(2):195-202

为了更全面地揭示岩溶发育特点,运用历史比较法,研究了武汉地区构造演化和岩溶发育史。古生代—中生代早期,武汉及周边地区地壳运动以整体升降为特点,各时代地层之间为平行不整合接触。晚古生代和中生代早期发生的两次大的海进—海退作用分别形成了石炭—二叠系和下三叠统两套碳酸盐岩系,为武汉地区岩溶发育提供了物质条件。中三叠世期末的印支运动产生的强大的NNE—SSW向挤压应力,形成NWW—SEE走向的线状褶皱,控制了碳酸盐岩的平面分布格局。晚三叠世—侏罗纪,武汉以西及北部等地隆起,东部及东南部的梁子湖地区在襄樊—广济等断裂的控制下逐步开始凹陷。这一时期内,地表、地下水总体向东部梁子湖凹陷汇集,控制了武汉地区第一期地下岩溶的发育。白垩—古近纪,武汉及周边地区地壳活动表现为差异性沉降,接受沉积,岩溶作用停止。新近纪—早更新世,武汉以西的潜江凹陷继续发展,而武汉地区则总体隆升。该时期内古地势东高西低,地表、地下水由东向西流动,第二期地下岩溶也自东向西发育。中、晚更新世时期,武汉及周边地区总体下沉,广泛形成厚10～30 m不等的老粘性土层覆盖于前二期岩溶之上。由于相对不透水层的阻隔,这一时期内岩溶作用基本停止发生。全新世时期,地表水的侵蚀作用部分地破坏了老粘土盖层的连续性。由于碳酸盐岩分布于现长江水体以下10～20 m,侵蚀基准面远高于碳酸盐岩的分布高程,地下水活动很弱,岩溶作用很弱或未发生。   相似文献   

Life cycle phenology, secondary production, and trophic guilds of caddisfly species in a lake-outlet stream of Patagonia     

Cecilia Brand  María Laura Miserendino 《Limnologica》2012,42(2):108-117

Lake-outlets are transitional areas recognized as highly productive ecosystems in terms of density and biomass of aquatic insects. Life cycle, secondary production, trophic guilds and environmental constraints of caddisfly assemblages were investigated on a natural lake-outlet stream (Nant y Fall) in Patagonia, Argentina. We investigated the site monthly from May 2007 to April 2008 by recording environmental data and sampling caddis larvae using a Surber sampler at riffle areas (n = 36). Mastigoptila longicornuta, Smicridea annulicornis, Smicridea frequens, Brachysetodes quadrifidus and Parasericostoma ovale displayed well synchronized univoltine life cycles, while Neoatopsyche brevispina, Neopsilochorema tricarinatum, showed an asynchronous development pattern, although most of them had an extended recruitment, similar to those reported for non lake-outlet streams in the area. Annual secondary production per species varied from 8.22 (B. quadrifidus) to 3568.83 mg m⁻² y⁻¹ (P. ovale), with overall caddisfly production amounting to 4.8 g m⁻² y⁻¹. Shredder/collector-filterer ratio was 3.3/1 suggesting that the system was detrital based. Redundancy analysis indicated that seasonally dynamic variables such as discharge, benthic particulate organic matter and temperature were the main predictors of seasonal caddisfly assemblage variation. We propose that the variety of food resources and the significant spatial heterogeneity at lake-outlet streams contribute to sustain a rich caddisfly community.  相似文献   

历史有感地震目录编制原则方法的研究——以《中国历史有感地震目录》编制为例     

刁守中  晁洪太  孙厥祥  李霞  山长仑  刁颋 《国际地震动态》2012,(4):30-38

在吸收历史地震研究、历史政区地理研究等多方面成果基础上,基于历史有感地震记载特点,探索了历史有感地震目录的编制原则,给出了地震日期、震中位置、震级的确定方法。以《中国地震历史资料汇编》等为依据,编制了公元前618年-公元1949年期间中国境内3≤M<443/4级历史有感地震目录9 121条。目录数量为中国同期文字记载的43/4级以上破坏性地震的7倍多,比全球其他国家或地区最早的同类目录早1 695年,约占全球同期M≤4.5级有感地震目录的2/3。  相似文献   

Genetic variation and population evolutionary history of the giant mottled eel （Anguilla marmorata） based on the mito- chondrial D-loop gene     

《海洋科学》2012,36(5)

通过测定花鳗鲡∞nguilliamarmorata）海南群体（HN）和菲律宾群体（PH）共19尾个体的线粒体D．100p基因的核苷酸序列（约1017bp）,分析了花鳗鲡的种群遗传结构。结果表明：A、T、G、C4种核苷酸的平均含量分别为39．8％、28_3％、12．4％、19．4％,A＋T含量（68．1％）明显高于G＋C含量（31．8％）。所测序列中存在73个变异位点,共有18个单倍型。其中海南群体的单倍型多样度（删）、核苷酸多态性（Pi）、平均核苷酸差异数（纠分别为0．982、0．21577和219．655,而菲律宾群体的单倍型多样度、核苷酸多态性、平均核苷酸差异数分别为1．000、0．26728和271．821,两个群体之间平均遗传距离（P）为0．3203。结果表明2个群体遗传变异较大,菲律宾群体的遗传多样性较海南群体更加丰富。通过构建NJ分子系统树表明2个群体的亲缘关系较近。利用中性检验Tajima’s D（海南群体D=I．35345,P〉0．01;菲律宾群体D=0．79220,P〉0．01）和Fs（海南群体Fs=3．759;菲律宾群体Fs=2．231）探讨其种群历史,表明花鳗鲡群体进化过程种群数量较为稳定。  相似文献   

Spatially different nutrient histories recorded by multiple cores and implications for management in Taihu Lake, eastern China     

CAO Yanmin  ZHANG Enlou  Peter LANGDON  LIU Enfeng  SHEN Ji 《中国地理科学(英文版)》2013,23(5):537-549

The Taihu Lake,a large shallow lake in the floodplain of the Changjiang(Yangtze) River in the eastern China,is faced with challenging ecological problems resulting from eutrophication,which has affected the regional freshwater supply of a large population.Although efforts have been made to assess the nutrient evolution histories in the northern bays,little is known regarding nutrient histories in different parts across the entire lake basin.In this paper,we present nutrient histories for different parts of the lake based on chironomid transfer functions applied to four short cores obtained from the northern,western and eastern regions of the lake.The chironomid-inferred total phosphorus(CI-TP) concentrations were compared with the phosphorus concentrations obtained by using instrumental and sedimentary data.The results suggest that trophic evolution histories were asynchronous throughout the lake during the past decades in response to different ecological regimes controlled by the nutrient input,wind direction and shoreline topography.The restoration of aquatic plants may be an effective option for the management of lake rehabilitation to ′natural′ conditions.Given the multiple factors controlling the biotic communities in such a large and complex lake,combined analyses among the multi-proxies encountered in the sediments are necessary for comprehensive insight into paleolimnological studies.The spatial heterogeneity in the ecological trajectories within this complicated ecosystem suggests that different management practices should be undertaken for specific lake zones in the Taihu Lake.  相似文献   

THOMAS JEFFERSON,AMERICAN GEOGRAPHERS,AND THE USES OF GEOGRAPHY*     

William A. Koelsch 《Geographical review》2008,98(2):260-279

ABSTRACT. Thomas Jefferson (1743–1826) had a lifelong interest in geography. Except for his role in the Lewis and Clark Expedition and a few references to his Notes on the State of Virginia, however, geographers have taken a relatively slight interest in this aspect of his thought, despite his having sometimes been referred to as “one of the greatest American geographers.” This essay suggests that we need to reexamine Jefferson as a geographical thinker. Reviewing some of the more important literature thus far, it suggests where such topics may profitably be extended and points to some aspects of his geographical interests not yet incorporated into the geographical literature.  相似文献   

Knowing our own history? Geography department archives in the UK   总被引：1，自引：0，他引：1  

Ron Johnston  Charles W J Withers 《Area》2008,40(1):3-11

The paper presents an analysis of the returns to a questionnaire survey on the state of department archives within UK departments of geography. The results of the survey are discussed in relation to recent work in geography which has examined the archive as a site for knowledge's making but seldom in its own terms as a resource for the history of geography, and studies within the archival sciences which have considered the archive as something more than a 'storehouse' for collective memory. The paper reveals that the archival record for the history of British geography is at best uneven, and in many departments non-existent, although information on departmental history is held, often as memory, by individual geographers. The paper considers the survey's implications for the future histories of British geography and addresses the nature of the UK geography department archive as resource and responsibility.  相似文献   

Prolonged impact of earthquake-induced landslides on sediment yield in a mountain watershed: The Tanzawa region, Japan   总被引：5，自引：0，他引：5  

Takashi Koi  Norifumi Hotta  Ituro Ishigaki  Norimasa Matuzaki  Yoshimi Uchiyama  Masakazu Suzuki 《Geomorphology》2008,101(4):692-702

To determine for how long a landslide affects sediment discharge, the sediment yields of 15 check-dam basins were compared with the time series of landslide distributions in a mountain basin in the Tanzawa region, central Japan. The distribution of sediment yield was quantitatively estimated from deposition in the sediment pools of check dams. The relationship between the landslide history and sediment discharge in the Nakagawa River basin was examined for an approximately 80-year period. Two major landslide events occurred during this period: the 1923 Kanto Earthquake and the 1972 disaster caused by heavy rainfall. The resulting trend in sediment discharge of the whole basin, estimated using reservoir sedimentation in the Miho Dam at its base, was nearly constant, with high sediment discharge (2897 m³ km^− 2 yr^− 1) in the intervening quarter-century, despite the recovery of vegetation on landslide areas in this period. Comparisons of the landslide distributions resulting from the two disasters, the sediment yields of check-dam basins, and the sediment discharge of the whole basin indicate that recent sediment discharge contains landslide debris that was originated by the Kanto Earthquake that occurred over 80 years ago. Thus, to understand high sediment discharge, it is essential to investigate not only the current basin condition and recent events, but also the landslide history of the basin for at least the previous 100 years.  相似文献   

Geographical extremes in the glacial history of northern Eurasia: post-QUEEN considerations     

Valery Astakhov 《Polar research》2008,27(2):280-288

This paper summarizes the principal results produced by the European Science Foundation's programme, Quaternary Environment of the Eurasian North (QUEEN). These results concern the distribution of late Quaternary glaciers of different ages across northern Eurasia. The pattern of glaciation is compared with the west–east climatic gradient of the continent. Of particular significance is the coincidence of the Late Weichselian ice margin with the modern 30°C difference between the July and January mean air temperatures. The difference between west and east in the annual amplitude of air temperature did not decrease during the Pleniglacial. The asymmetry of the glacial history suggests a progressive aridification of the Eurasian North, with the result that by marine isotope stage 2 significant ice volumes could only accumulate along the Atlantic seaboard. The different climatic signals of thermochrons and cryochrons of the extreme west and east of the continent are discussed. The growth of continentality eastwards restrains the applicability of pollen proxies for climatic reconstructions.  相似文献   

Dinocyst microlaminations and freshwater "red tides" recorded in Lake Xiaolongwan,northeastern China   总被引：1，自引：0，他引：1  

Guoqiang Chu  Qing Sun  Patrick Rioual  Andrés Boltovskoy  Qiang Liu  Peiqi Sun  Jintai Han  Jiaqi Liu 《Journal of Paleolimnology》2008,39(3):319-333

We reported a special type of lamination formed in the sediments of Lake Xiaolongwan, northeastern China. The lamination consists of light- and brown-colored laminate couplets in the thin sections. The brown-colored layer is composed mainly of dinoflagellate cysts. The grey-colored layer consists of other organic and siliceous matter (plant detritus, diatoms, chrysophyte cysts) and clastics. Preliminary sediment trap results show that a distinct peak of dinocyst flux occurred in November. The dinocyst flux maximum also corresponds to the peaks of diatom flux and chrysophyte stomatocyst flux. These suggest that "red tide blooms" occur in this freshwater lake. We speculate that the dinocyst flux maximum could be related to autumn overturn due to increased nutrients, and the availability of cysts for germination from the lake bottom. Additionally, it may also reflect increasing dissolved organic matter after leaf fall. An independent chronology derived from ¹³⁷Cs and ²¹⁰Pb shows a good agreement with counted laminations. From the sediment trap data and the independent chronology data, the dinocyst microlaminae appear to be annually laminated, and probably could be called dinocyst varves. Although vegetative (thecate stage) cells of Peridinium volzii and Ceratium furcoides are found in the water samples, it is not possible to relate the dinocysts to these two dinoflagellate species. Based on morphological and ecological analyses, we suggested that they have affinities with species of Peridinium (sensu lato), most probably to P. inconspicuum. Detailed investigations should be carried out to understand the red tide history in this freshwater lake. Annually laminated dinocyst microlayers in freshwater and marine sediments not only provide an uncommon archive for understanding the history of red tides and harmful algal blooms, and why and how certain species periodically bloom over several thousands years, but also provide important records of paleoenvironmental and paleoclimatic changes at seasonal to annual resolution.  相似文献