Palaeolimnology of Lake Piene-Kuuppalanlampi (Kurkijoki, Karelian Republic, Russia): isolation history, lake ecosystem development and long-term agricultural impact     

Juha Miettinen  Elisabeth Grönlund  Heikki Simola  Pertti Huttunen 《Journal of Paleolimnology》2002,27(1):29-44

The post-glacial history of Lake Pieni-Kuuppalanlampi, western Lake Ladoga region, was studied by means of stratigraphic pollen and diatom analyses. Diatoms were analysed to track the isolation history of the basin and the limnological effects of the early land-use phases indicated by pollen analysis. Chrysophycean stomatocysts and Isoëtes spores were also employed in the limnological reconstructions. Sediment dating was provided by six conventional radiocarbon dates.The lower part of the 370-cm long sediment sequence represents early Holocene, large lake conditions: the (freshwater) Yoldia and Ancylus stages of the Baltic basin, with a short-term lagoonal or isolation phase at the end of Yoldia. The basin was isolated due to Ancylus lake regression at 9785 cal B.P. For the small-lake sequence (0–250 cm) we used diatom inferences (WA-method) for hindcasting water chemistry. The post-isolation limnology of Pieni-Kuuppalanlampi reflects the development of vegetation on its small hill-top catchment. In its early development, the lake was mesotrophic, but became more acidic (pH about 6) and oligotrophic after the decline of temperate hardwood trees and the spread of spruce to the area after around 5000 B.P. The lake ecosystem appears to have reacted sensitively to agricultural land-use in the catchment from AD 400–800 onwards: inferred total phosphorus levels and pH both rise during these periods.  相似文献   

P wave amplitudes in a 3-D earth     

Ileana M. Tibuleac  Guust Nolet  Caryl Michaelson  Ivan Koulakov 《Geophysical Journal International》2003,155(1):1-10

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An Mw based earthquake Catalogue for central, northern and northwestern Europe using a hierarchy of magnitude conversions   总被引：3，自引：1，他引：3  

G. Grünthal  R. Wahlström 《Journal of Seismology》2003,7(4):507-531

Data from 25 local catalogues and 30special studies of earthquakes in central,northern and northwestern Europe have beenincorporated into a Databank. The dataprocessing includes discriminating eventtypes, eliminating fake events and dupletsand converting different magnitudes andintensities to M_w if this is not givenby the original source. The magnitudeconversion is a key task of the study andimplies establishment of regressionequations where no local relations exist.The Catalogue contains tectonic events fromthe Databank within the area44°N–72°N,25°W–32°E and the time period1300–1993. The lower magnitude level forthe Catalogue entries is setat M_w == 3.50. The area covered by thedifferent catalogues are associated withpolygons. Within each polygon only datafrom one or a small number of the localcatalogues, supplemented by data fromspecial studies, enter the Catalogue. Ifthere are two or more such catalogues orstudies providing a solution for an event,a priority algorithm selects one entry forthe Catalogue. Then M_w is calculatedfrom one of the magnitude types, or frommacroseismic data, given by the selectedentry according to another priority scheme.The origin time, location, M_w magnitude and reference are specified for eachentry of the Catalogue. So is theepicentral intensity, I₀, if providedby the original source. Following thesecriteria, a total of about 5,000earthquakes constitute the Catalogue.Although originally derived for the purposeof seismic hazard calculation within GSHAP,the Catalogue provides a data base for manytypes of seismicity and seismic hazardstudies.  相似文献   

A bilinear approximation of the surface relief in terrain correction computations   总被引：2，自引：2，他引：2  

D. Tsoulis  H. Wziontek  S. Petrović 《Journal of Geodesy》2003,77(5-6):338-344

A new method is presented for the computation of the gravitational attraction of topographic masses when their height information is given on a regular grid. It is shown that the representation of the terrain relief by means of a bilinear surface not only offers a serious alternative to the polyhedra modeling, but also approaches even more smoothly the continuous reality. Inserting a bilinear approximation into the known scheme of deriving closed analytical expressions for the potential and its first-order derivatives for an arbitrarily shaped polyhedron leads to a one-dimensional integration with – apparently – no analytical solution. However, due to the high degree of smoothness of the integrand function, the numerical computation of this integral is very efficient. Numerical tests using synthetic data and a densely sampled digital terrain model in the Bavarian Alps prove that the new method is comparable to or even faster than a terrain modeling using polyhedra.  相似文献   

Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China)   总被引：26，自引：0，他引：26  

H. Willems  Z. Zhou  B. Zhang  K. -U. Gräfe 《International Journal of Earth Sciences》1996,85(4):723-754

The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian.  相似文献   

Croatia — a coastal and maritime country     

Nikola Stražičić 《GeoJournal》1996,38(4):445-453

Croatia, through its geographic position, is a Mediterranean/Adriatic and Central European/Danube state. As an Adriatic coastal state, it has a long maritime tradition, which is apparent in its well-developed shipping (2.4 million GT), the high-quality ship-building industry (among the top six in the world) and through its numerous sea ports, of which many were established in ancient times. The leading national port is Rijeka, which is at the same time an important transit port for Austria, Hungary, Slovakia and the Czech Republic.The exceptionally indented Croatian Adriatic coast with its attractive archipelagos and favorable climatic and oceanographic conditions in the coastal sea offers very advantageous conditions for comprehensive tourist utilization. This is particularly true of nautical tourism, which is complimented by a larger number of constructed and well-equipped yachting ports/marinas on the coast and islands.  相似文献   

The Carpatho-Balkanides and adjacent area: a sector of the Tethyan Eurasian metallogenic belt   总被引：3，自引：1，他引：3  

S. Janković 《Mineralium Deposita》1997,32(5):426-433

The Tethyan Eurasian metallogenic belt (TEMB) was formed during Mesozoic and post-Mesozoic times in the area of the former Tethyan ocean on the southern margin of Eurasia, with the Afro-Arabian and Indian plates to the south. It extends from western Mediterranean via the Alps and southeastern Europe through the Lesser Caucasus, the Hindu Kush, and the Tibet Plateau to Burma and SW Indonesia, linking with the West Pacific metallogenic belt. The Carpatho-Balkan region is one of the sectors of the TEMB, characterized by some specific features. The emplacement of ore deposits is related to a definite time interval, and to specific tectonic settings such as: 1. Late Permian-Triassic intracontinental rifting along the northern margin of Gondwanaland and/or fragments already separated. This setting involves volcanogenic and volcano-sedimentary deposits (iron, lead/zinc, manganese, antimony, mercury, barite), skarn deposits associated with volcano-plutonic complexes of bimodal magmatism, and low temperature carbonate-hosted lead/zinc deposits. 2. Jurassic intraoceanic rifting – ophiolite complexes: This setting hosts major magmatic (particularly podiform chrome deposits) and volcano-sedimentary deposits, mainly of the Cyprus type. 3. Subduction-related setting involves porphyry copper deposits, lesser skarn deposits (iron, locally Pb-Zn), massive sulphide Cu (e.g. Bor) accompanied locally by Pb-Zn of replacement type, epithermal gold deposits, associated with calc-alkaline igneous complexes of the Early Tertiary-Late Cretaceous, and the Neogene gold/silver and base metals deposits. 4. Post-collision continent-continent setting includes deposits of Pb-Zn, Sb, As, Au-Cu associated with volcano-plutonic complexes of calc-alkaline affinity. Several major Alpine metallogenic units are developed in the Carpatho-Balkanides and adjacent area, each characterized by specific development, mineral associations, and types of ore deposits. Received: 3 June 1996 / Accepted: 10 January 1997  相似文献   

Influence of the Load Wavelength on the Permeability of a Viscosity Interface in the Mantle     

Čížková  Hana  Čadek  Ondřej  van den berg  Arie P. 《Studia Geophysica et Geodaetica》1997,41(1):64-72

Assuming a radially stratified Newtonian mantle in a steady-state approximation, we demonstrate that the permeability of a viscosity interface at 660-km depth strongly depends on the wavelength of buoyancy forces driving the flow. The flow induced by long-wavelength loads penetrates through the boundary freely even if the viscosity increases by two orders. In contrast, the boundary is practically impermeable for short-wavelength loads located in the upper mantle. Thus, a stepwise increase of viscosity is a significant obstacle for small descending features in the upper mantle, but huge upper mantle downwellings, or upwellings formed in the-lower mantle can overcome it easily. This indicates that certain care is necessary in interpreting the seismic structure of the mantle by means of flow models. The global tomographic image includes only the first few degrees of the harmonic series and, consequently, its interpretation in terms of a present-day flow field results in a predominantly whole-mantle circulation even for extreme viscosity contrasts.  相似文献   

Remote sensing detection of atmospheric pollutants by differential absorption LIDAR 510M/SODAR PA2 mobile system     

J. Keder  M. Střižík  P. Berger  A. Černý  P. Engst  I. Němcová 《Meteorology and Atmospheric Physics》2004,85(1-3):155-164

Summary Air pollution problem in the Czech Republic is very complex due to large number of factors as turbulent dispersion and chemical reactions concurring in the status of the PBL. For this 3D distribution of pollutants is a key information that cannot be given by conventional monitoring stations. Combined use of DIAL lidar and sodar can give access to such information. Case studies of air pollutants transport are presented using 3D concentration fields of NO₂ and ozone measured by lidar and meteorological conditions monitored by Doppler Sodar.  相似文献   

Effet du vieillissement des céramiques poreuses sur leur capacité à évaluer la concentration de pesticide en solution     

Nicolas Domange  Caroline Grégoire  Véronique Gouy  Michèle Tremolières 《Comptes Rendus Geoscience》2004,336(1):49-58

The soil solution sampling by ceramic cups allows pesticide transfer monitoring in the soil during long times. The ageing of material involves a bias in the sampling results. In laboratory, the comparison of two types of ceramic suction cups, new and installed in situ during four years, shows a modification of the hydrodynamic properties and a possible evolution of the adsorption capacity of the matrix. The passage rate, as well qualitative as quantitative, is better for the old material. Recommendations about site management are finally exposed. To cite this article: N. Domange et al., C. R. Geoscience 336 (2004).  相似文献