Durbachites–Vaugnerites – a geodynamic marker in the central European Variscan orogen     

Jürgen F. von Raumer  Fritz Finger  Petra Veselá  Gérard M. Stampfli 《地学学报》2014,26(2):85-95

Durbachites–Vaugnerites are K–Mg‐rich magmatic rocks derived from an enriched mantle source. Observed throughout the European Variscan basement, their present‐day geographical distribution does not reveal any obvious plate‐tectonic context. Published geochronological data show that most durbachites–vaugnerites formed around 335–340 Ma. Plotted in a Visean plate‐tectonic reconstruction, the occurrences of durbachites–vaugnerites are concentrated in a hotspot like cluster in the Galatian superterrane, featuring a distinctive regional magmatic province. Reviewing the existing local studies on Variscan durbachite–vaugnerite rocks, we interpret their extensive appearance in the Visean in terms of two factors: (i) long‐term mantle enrichment above early Variscan subduction systems; and (ii) melting of this enriched subcontinental mantle source during the Variscan collision stage due to thermal anomalies below the Galatian superterrane, possibly created by slab windows and and/or the sinking of the subducted Rheic slab into the mantle. The tectonic reorganization of Europe in the Late Palaeozoic and during the Alpine orogeny has torn apart and blurred this marked domain of durbachites–vaugnerites.  相似文献   

Linkages Between Boundary-Layer Structure and the Development of Nocturnal Low-Level Jets in Central Oklahoma   总被引：1，自引：1，他引：0  

Petra M. Klein  Xiao-Ming Hu  Alan Shapiro  Ming Xue 《Boundary-Layer Meteorology》2016,158(3):383-408

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Effects of some representative petroleum refinery effluent compounds on photosynthesis and growth of natural marine phytoplankton assemblages: Part 1—cresols     

W.H Thomas  S.S Rossi  D.L.R Seibert 《Marine environmental research》1981,4(3):203-215

The effects of cresols on the photosynthesis and growth of natural marine phytoplankton assemblages from the Scripps Pier at La Jolla, California, USA were measured. In two experiments, in which dinoflagellates were the dominant algae, photosynthesis (measured by ¹⁴C uptake) was inhibited at concentrations > 100 μg litre^?1 and the concentration giving half-maximal photosynthesis was 10,000 μg litre^?1. In a third experiment, in which diatoms were dominant, photosynthesis was not inhibited until levels > 10,000 μg litre^?1 were reached and the half-maximal concentration was 20,000 μg litre^?1. These experiments suggested that dinoflagellates were more sensitive to cresols than diatoms. However, the reverse was true in an experiment using cultures. In a long-term growth experiment (natural assemblages from the Scripps Pier), only a level of 88,000 μg litre^?1 completely inhibited growth. There was a two-day lag in growth at 8500 μg litre^?1, but the algae recovered and grew as well as the controls which contained no cresols. This experiment was started with a mixed diatom-dinoflagellate-microflagellate population but only the diatoms grew. High concentrations of cresols (> 900 μg litre^?1) resulted in a decrease in the diatom Skeletonema costatum, compared with the controls. Otherwise there was no selection for resistant species. In these experiments, cresols were measured by extraction with methylene chloride from seawater followed by measurement by UV absorption. In all experiments cresol levels decreased with time. This was attributed to uptake by phytoplankton and bacterial degradation.  相似文献   

Fluid inclusions in granulite-facies metapelites of the Hercynian ancient lower crust of the Serre,Calabria, Southern Italy     

Petra Herms  Volker Schenk 《Contributions to Mineralogy and Petrology》1992,112(2-3):393-404

Investigations of fluid inclusions in granulitefacies metapelites of southern Calabria enable characterization of the fluid composition of these lower crustal rocks, and constrain the petrologically deduced retrograde P-T path characterized by isothermal uplift prior to isobaric cooling in middle crustal levels. Fluid inclusions in cordierite, garnet and sillimanite have a CO₂-rich composition. Inclusions in cordierite rarely contain minor amounts of N₂ and H₂O, and in garnets some CO₂–CH₄–N₂ inclusions have been analyzed by Raman microprobe. Quartz reveals the most complex fluid melusion compositions (1) CO₂-rich, (2) CO₂–CH₄–N₂, (3) CH₄–N₂, (4) H₂O–MgCl₂–CaCl₂–NaCl, (5) H₂O–NaCl and (6) H₂O–CO₂. The earliest fluid inclusions after peak metamorphism are rich in CO₂ with minor amounts of N₂ and H₂O. An early CO₂–(H₂O–N₂) fluid composition has been confirmed by detection of CO₂, H₂O and N₂ in the channels of the cordierite structure. Most of the early CO₂-rich fluid inclusions were modified during the uplift from the lower to the middle crustal level, resulting in a density decrease with CO₂ still dominant. The subsequent isobaric cooling led to further modifications of the fluid inclusions. High-density inclusions around implosion textures or scattered amongst lower-density ones must have formed during this cooling episode. Aqueous inclusions in quartz are mostly formed late and are consistent with trapping during retrograde rehydration.This project has been supported by the DFG as contribution to the special program Continental Lower Crust  相似文献   

Water storage dynamics in a till hillslope: the foundation for modeling flows and turnover times          下载免费PDF全文

Nino Amvrosiadi  Jan Seibert  Thomas Grabs  Kevin Bishop 《水文研究》2017,31(1):4-14

Studies on hydrology, biogeochemistry, or mineral weathering often rely on assumptions about flow paths, water storage dynamics, and transit times. Testing these assumptions requires detailed hydrometric data that are usually unavailable at the catchment scale. Hillslope studies provide an alternative for obtaining a better understanding, but even on such well‐defined and delimited scales, it is rare to have a comprehensive set of hydrometric observations from the water divide down to the stream that can constrain efforts to quantify water storage, movement, and turnover time. Here, we quantified water storage with daily resolution in a hillslope during the course of almost an entire year using hydrological measurements at the study site and an extended version of the vertical equilibrium model. We used an exponential function to simulate the relationship between hillslope discharge and water table; this was used to derive transmissivity profiles along the hillslope and map mean pore water velocities in the saturated zone. Based on the transmissivity profiles, the soil layer transmitting 99% of lateral flow to the stream had a depth that ranged from 8.9 m at the water divide to under 1 m closer to the stream. During the study period, the total storage of this layer varied from 1189 to 1485 mm, resulting in a turnover time of 2172 days. From the pore water velocities, we mapped the time it would take a water particle situated at any point of the saturated zone anywhere along the hillslope to exit as runoff. Our calculations point to the strengths as well as limitations of simple hydrometric data for inferring hydrological properties and water travel times in the subsurface.  相似文献   

Origin and contrasting succession pathways of the Western Carpathian calcareous fens revealed by plant and mollusc macrofossils     

Petra Hájková  Michal Horsák  Michal Hájek  Adam Lacina  Hana Buchtová  Barbora Pelánková 《Boreas: An International Journal of Quaternary Research》2012,41(4):690-706

Calcareous fens are unique environments whose history is almost unexplored. The radiocarbon dates of the basal layers of 49 undisturbed calcareous fens showed that in the Western Carpathians (central Europe) many of the extant fen sites originated fairly recently, with two peaks in the High Middle and Roman Ages, the former corresponding to human‐induced changes of the landscape. Conspicuous number of fens also appeared in the Lateglacial and later in the Bronze Age owing to suitable environmental conditions. The Lateglacial calcareous fens were of semi‐open character with coniferous trees, a heliophilous understorey, and mollusc communities composed of several snail species typical of glacial landscapes. We found wood of Taxus baccata in six localities between 7390 and 600 cal. a BP, suggesting that calcareous fens could have represented a refugial habitat for this red‐listed species during the middle Holocene. Using plant macrofossil and mollusc analyses of three representative profiles we illustrate the most common developmental types: (i) fens originating in the Lateglacial, having an open or semi‐open character during the whole Holocene; (ii) open fens originating as wooded wetlands; and (iii) open fens starting their development de novo in the late Holocene. Human activities were responsible for the formation of a high number of calcareous fens, especially in the Outer Western Carpathians, and became important drivers of fen biodiversity development. Only a few recently existing calcareous fens contain old sequences of calcareous deposits. They represent unique natural archives and harbour highly endangered relic populations of fen specialists, making their strict protection urgent.  相似文献   

Conceptualization in catchment modelling: simply learning?     

S. M. Dunn  J. Freer  M. Weiler  M. J. Kirkby  J. Seibert  P. F. Quinn  G. Lischeid  D. Tetzlaff  C. Soulsby 《水文研究》2008,22(13):2389-2393

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Seasonality and time scales in the relationship between global SST and African rainfall   总被引：1，自引：0，他引：1  

Heiko Paeth  Petra Friederichs 《Climate Dynamics》2004,23(7-8):815-837

The main goal of this study is to determine the oceanic regions corresponding to variability in African rainfall and seasonal differences in the atmospheric teleconnections. Canonical correlation analysis (CCA) has been applied in order to extract the dominant patterns of linear covariability. An ensemble of six simulations with the global atmospheric general circulation model ECHAM4, forced with observed sea surface temperatures (SSTs) and sea ice boundary variability, is used in order to focus on the SST-related part of African rainfall variability. Our main finding is that the boreal summer rainfall (June–September mean) over Africa is more affected by SST changes than in boreal winter (December–March mean). In winter, there is a highly significant link between tropical African rainfall and Indian Ocean and eastern tropical Pacific SST anomalies, which is closely related to El Niño-Southern Oscillation (ENSO). However, long-term changes are found to be associated with SST changes in the Indian and tropical Atlantic Oceans, thus, showing that the tropical Atlantic plays a critical role in determining the position of the intertropical convergence zone (ITCZ). Since ENSO is less in summer, the tropical Pacific and the Indian Oceans are less important for African rainfall. The African summer monsoon is strongly influenced by SST variations in the Gulf of Guinea, with a response of opposite sign over the Sahelian zone and the Guinean coast region. SST changes in the subtropical and extratropical oceans mostly take place on decadal time scales and are responsible for low-frequency rainfall fluctuations over West Africa. The modelled teleconnections are highly consistent with the observations. The agreement for most of the teleconnection patterns is remarkable and suggests that the modelled rainfall anomalies serve as suitable predictors for the observed changes.  相似文献   

Water quality in rural areas of the Czech Republic: Key study Slapanka River catchment   总被引：1，自引：0，他引：1  

Petra Judov  Bohumír Janský 《Limnologica》2005,35(3):160-168

The article evaluates the water quality in rural areas in the Czech part of Labe River catchment using the example of Slapanka River catchment. This river drains a typical landscape of Ceskomoravska Highland. Water quality in rural areas is still very low and the attention is paid to organic substances and nutrients. Increased amount of them in streams is caused mainly by agriculture and production of municipal wastewater resulting in increased eutrophication. A significant part of the article consists in the evaluation of point and non-point sources of water pollution. Identifying the type of the pollution source is helped by regression analysis using data from the public monitoring network. Eleven sampling sites were selected for evaluating the water quality. Physical and chemical analyses were made 12 times during the field monitoring in the years 2001–2003.In long-term development water quality has improved in all monitored parameters during the last 15 years. Least significant improvement has been found with the concentration of nitrate nitrogen. The water quality within the whole catchment area still remains low.To reduce the influence of pollution sources, we recommend the sanitation of diffuse sources of pollution from small settlements with less than 2000 inhabitants, and a successive change from agricultural management and intensive mass production to extensive ways, especially in mountain and sub-mountain areas.  相似文献   

Application of a forest succession model to a continentality gradient through Central Europe   总被引：1，自引：0，他引：1  

Marcus Lindner  Petra Lasch  Wolfgang Cramer 《Climatic change》1996,34(2):191-199

The forest succession model FORSKA was applied to a west-east transect across Central Europe using points from a global climate data set. Climate change experiments were undertaken for two general circulation model scenarios and two different site classes. The simulated climate changes lead to reduced forest productivity and a changed species composition on most sites. Under current climate, the broad scale pattern of the climatically driven distribution of forest communities is quite realistically reproduced. However, the resolution of climate data imposes limitations on the simulation of forest dynamics in subcontinental climate, because climate variability and extreme events are not well represented.  相似文献