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排序方式: 共有806条查询结果,搜索用时 31 毫秒
31.
S. Filahi M. Tanarhte L. Mouhir M. El Morhit Y. Tramblay 《Theoretical and Applied Climatology》2016,124(3-4):959-972
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Bilal?El OuaragliEmail author Mohamed?Najib?Zaghloul Hajar?El Talibi Roberta?Somma 《Arabian Journal of Geosciences》2016,9(15):660
This work deals with sedimentological, petrographic, and structural analyses of a middle Miocene late-orogenic sedimentary cycle, denoted Oued Dayr Formation, recognized in the Rifian sector of the Maghrebian Chain (Morocco). The analyzed Formation (75 m thick) starts with 15–20 m of light colored polymict conglomerates, with minor sandstone beds, lying on the Paleozoic basement and Mesozoic cover of the Ghomaride Nappe. Facies analysis indicates a fining-upward deposition in a marine environment characterized by increasing deepening, reflecting a subsidence rate that exceeds sedimentary supply. Petrographic analysis points out that sandstones are represented by litharenites originated by erosion of recycled orogen. The conglomerates pebbles and cobbles consist of Alpine low- to high-grade metamorphic rocks as metarenites, phyllites, mylonitic quartzites, micaschists, augen gneisses deriving from the exhumed deep metamorphic basement, the overlying metasedimentary of the Sebtide Nappes and of sedimentary rocks as sandstones, jaspes, limestones, and shales deriving from the Ghomaride Nappes and their sedimentary cover. Data reveal mixed provenance indicating that the Oued Dayr Formation was fed by the Internal Nappes stack of the Maghrebian Chain. Structural analysis shows that the Oued Dayr Formation accumulated in a Thrust-Top basin, during an early extension (D0 phase), recorded by synsedimentary normal faults within middle Langhian deposits on the rear of the Internal Nappes stack. Subsequent ductile and brittle compressional (D1, D2, D3) and extensional (D4) deformation phases occurred during and/or after the stacking, exhumation, and early unroofing of Sebtide Complex coeval with the opening of the western Mediterranean back-arc basins since middle Miocene time. 相似文献
33.
The influence of physical and biological processes on the ichthyoplankton communities in the Gulf of Sirte (Southern Mediterranean Sea) 下载免费PDF全文
Angela Cuttitta Sergio Bonomo Salem Zgozi Angelo Bonanno Bernardo Patti Enza Maria Quinci Marco Torri Mohamed Hamza Abdul Fatah Daw Haddoud Akram El Turki Abdul Bari Ramadan Simona Genovese Salvatore Mazzola 《Marine Ecology》2016,37(4):831-844
This paper reports on the first study on the ichthyoplankton community structure in the Gulf of Sirte and its spatial distribution in relation to environmental conditions and zooplankton abundance. The results make an important contribution to the future management of fisheries in this unexplored, but much exploited, area. Biological samples were collected in July 2008 using a Bongo40 net. In total, 1914 larvae were found and 1652 of these were identified. In particular, bathypelagic taxa were the most abundant, followed by demersal, mesopelagic, pelagic and epipelagic taxa. The ichthyoplankton community had a patchwork distribution influenced by oligotrophic conditions, the bottom depth and oceanographical features. The results suggest that environmental forcings were able to transport the ichthyoplankton to productive areas. Indeed, maximum fish egg densities were found in coastal stations in correspondence with the Atlantic Tunisian Current inflow, whereas larvae were mainly concentrated in the east side of the Gulf, probably as a result of advection by the anticyclonic circulation. Additionally, the distribution patterns of the total larvae density and the different assemblages were well matched with the abundance of the zooplankton, probably determining final larval survival, growth and recruitment. 相似文献
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Słodczyk Elżbieta Pietranik Anna Glynn Sarah Wiedenbeck Michael Breitkreuz Christoph Dhuime Bruno 《International Journal of Earth Sciences》2018,107(6):2065-2081
International Journal of Earth Sciences - The Polish Lowlands, located southwest of the Teisseyre–Tornquist Zone, within Trans-European Suture Zone, were affected by bimodal, but dominantly... 相似文献
37.
A. El Hanandeh M. Gharaibeh A. A. Albalasmeh 《International Journal of Environmental Science and Technology》2018,15(5):927-934
Treated wastewater is a valuable resource, particularly in countries facing water shortage such as Jordan. Nevertheless, excess nutrients, especially phosphorus, may have detrimental impacts on receiving waterbodies. Treated wastewater in Jordan often exceeds the recommended levels set by the Jordanian Standards for wastewater reuse and discharge. Therefore, it is important to reduce phosphorus loads to acceptable levels before discharge. Biofiltration is a low-cost technology that has shown good potential for wastewater treatment. The performance of biofilters largely depends on the media used. In this study, local sand and sand augmented with biochar prepared from the olive oil processing waste (SBC) were used as filter media for phosphorus removal from clarified secondary treated wastewater. The two media types were tested under different hydraulic and phosphorus loading conditions to simulate shock, flooding, and inundation conditions. The results showed that sand media was more effective in removing phosphorus (90.8 ± 2.6%) than sand amended with biochar (83.3 ± 3.2%). Both media showed resilience under extreme loading conditions. Although phosphorus removal efficiency was negatively affected following the extreme loading events, the observed effects were temporary. The simulated inundation event further showed that the media was able to retain the adsorbed phosphorus. Furthermore, the phosphorus concentration in the effluent remained within the prescribed discharge guidelines at all times. 相似文献
38.
Eman M. Ibrahim Ibrahim E. El Aassy Hayam Ahmed Abdel Ghany S. H. Gamil 《Environmental Earth Sciences》2018,77(14):534
Tailings resulted from sulphuric acid leaching process of uranium from sedimentary rocks contain high concentrations of 226Ra and its daughters, the most important of which is 222Rn. Movement of radon gas out of the tailings is strongly influenced by the physicochemical characteristics of these tailings especially their radium content and the grain size. So, the tailing samples were size fractionated into four sizes (>?250, 250–125, 125–74 and <?74 µm). The natural radioactivity was investigated using hyper-pure germanium detector and solid-state nuclear track detectors (CR-39) for bulk size and after size fractionation. The activity concentrations of different radionuclides in size-fractionated tailing samples have been shown to be strongly dependent on the size of the particles. In the range of >?250 and <?74 µm, the activity concentrations of 230Th, 226Ra, 214Pb, 214Bi, 210Pb, 232Th and 40K increased throughout with decreasing particle size, while that of 238U, 234U and 235U have an opposite effect. The results revealed an inverse relationship between the radon exhalation rate and size fractionation. Also, the results showed a good correlation between radium activity concentration and radon mass exhalation rate. 相似文献
39.
Amr Abdel Aty Abdel Hamid Hassan Ismail El Sundoly Ahmed Ali Abu Steet 《Arabian Journal of Geosciences》2018,11(11):273
Ras Abda plutonic suite, North Eastern Desert of Egypt, consists predominantly of Neoproterozoic calc-alkaline older granites. Minor exposures of pink microgranite are occurring along Wadi Ras Abda within the older granites. Previous studies on this area demonstrated that the microgranite is altered in some parts and contains anomalous concentrations of rare metal elements (Zr, Th, and U). These altered and mineralized zones are re-assessed using field observations, chemical analysis, and by the application of various transmitted light and electron microscopic techniques. The rare metals exist as mineral segregation grew freely into open cavities of the microgranite and concordant with the NNE strike-slip fault movement. The mineralized zones contain an assemblage of secondary magnetite, zircon, uranothorite, columbite-(Mn), fergusonite-(Y), and allanite-(Ce). The extreme abundance of zircon in the mineralized zone, along with other evidence, indicates a hydrothermal origin of this zircon together with associated rare metals. The geochemical investigation and mass balance calculations revealed extreme enrichment of Zr, Th, U, Y, Nb, Ta, and REE. Post-magmatic hydrothermal alterations resulted in such pronounced chemical and mineralogical heterogeneity. The hydrothermal fluids are thought to be oxidizing, alkaline and of medium temperature (>?250 °C). The average contents of the elements Zr (1606 ppm), Th (1639 ppm), U (306 ppm), Nb (955 ppm), and REE (1710 ppm) in the mineralized microgranite reach sub-economic levels and could be a potential source of these elements. 相似文献
40.
Bartosz J. Płachno Agata Jurkowska Grzegorz Pacyna Elżbieta Worobiec Przemysław Gedl Ewa Świerczewska-Gładysz 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):159-170
This paper presents the results of studies on plant macroremains found in the upper Turonian of the Folwark Quarry, Opole, Poland, associated with palynological studies of the host rocks. In addition to a few macrofossils (gymnosperm wood, conifer Geinitzia reichenbachii and fern ?Didymosorus) rich sporomorphs (bryophyte, lycopod and fern spores, conifer and angiosperm pollen grains) and marine palynomorphs (mainly dinoflagellate cysts) were recorded. The palynological analysis revealed that the vegetation on the neighbouring land (the East Sudetic Island) in the late Turonian was much more diverse than could be reconstructed based on only macrofossil remains. The latter are taxonomically restricted and dominated by one gymnosperm species (Geinitzia reichenbachii), which make them similar to most neighbouring, coeval Central European assemblages. Its over representation is, thus, a result of taphonomy. 相似文献