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141.
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
142.
Sensitivity analysis for the GALDIT method based on the assessment of vulnerability to pollution in the northern Sfax coastal aquifer,Tunisia 总被引:1,自引:0,他引:1
Mona?GontaraEmail author Nabila?Allouche Ikram?Jmal Salelm?Bouri 《Arabian Journal of Geosciences》2016,9(5):416
Coastal aquifer of northern Sfax (Tunisia) suffers from the high risk to seawater intrusion and the water quality degradation due to the overexploitation. Hence, assessing the study area vulnerability to pollution is highly crucial so as to protect the groundwater resources. The assessment has been performed by applying the GALDIT method using Geographic Information System (GIS) software and multi-criteria evaluation techniques, and the sensitivity analysis approach to evaluate the effect of each GALDIT parameter on the vulnerability assessment. The GALDIT vulnerability map classifies the study area into three vulnerability classes: low vulnerability (30–50), moderate vulnerability (50–70), and high vulnerability (70–90), which represent 5, 30, and 65 % of the study area, respectively. The map illustrates that the coastal zones of the aquifer are the most threatened areas. The sensitivity analysis results show that the aquifer hydraulic conductivity (A) and the thickness of the aquifer (T) represent the determining factors in the modified vulnerability model. The real weight was used to elaborate the modified GALDIT model which was correlated with resistivity values for validation. This study could serve as a scientific basis for sustainable land planning and groundwater management in the study area. 相似文献
143.
Imen?TurkiEmail author Benoit?Laignel Nicolas?Massei Zeneddine?Nouaceur Nadir?Benhamiche Khodir?Madani 《Arabian Journal of Geosciences》2016,9(6):477
The long-term variability of rainfall in the Soummam watershed (NE Algeria) has been analysed over the past 108 years using continuous wavelet method in order to identify the interannual modes controlling the rainfall variability. Statistical analyses of rainfall timeseries have shown its distribution following five periods of time, limited by a series of discontinuities around 1935, 1950, 1970 and 1990. The continuous wavelet transform have demonstrated different low frequency modes: 2–4, 4–8, 8–16 and 16–32 years.The annual band is expanded during the full study period with some pics around 1905, 1920–1935 and 1960; it shows a negative long-term trend, in particular since the period 1970–1990 when a major change has been identified. Then, the relationships between climate patterns of North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI) and the hydrological variability in the frequency domain have been investigated; they have shown a mean explained variance of 40 and 24 %, respectively. Such variances are less obvious for the annual mode and increase for the interannual frequencies. The coherence suffer from high perturbations since the period 1970–1990 when the NAO (SOI) shifts from negative (positive) phases to positive (negative) ones. Such anomalies are responsible for significant changes of rainfall variability, emphasising the global warming effects. 相似文献
144.
Abbas?Majdi Hamed?Ajamzadeh Siavash?NadimiEmail author 《Arabian Journal of Geosciences》2016,9(7):512
This paper presents the results of a numerical study that has been performed to investigate the different joint types that affect the moment-rotation relation and ultimate bending moment capacity of a joint. A 3D finite element method was adapted to establish elaborate numerical models of segments. To evaluate the possible differences in moment-rotation behavior between different joint types, 10 different joint types were simulated. Additionally, the effect of different joint types on behavior of a lining ring was investigated. The validity of the peridynamic simulation was tested by comparing results obtained in this paper against the results obtained in a study performed by Hordijk and Gijsbers. Observations of the results demonstrate that in a flat joint, the expanding of joint height increased the rotation stiffness of the joint in the linear branch, and accordingly, the ultimate bending moment of the joint increased. In the ring model, it was observed that the expanding of joint height led to the decreased of ring displacement and stress concentration in the joint. Whenever there were full surface contacts (contact two segment in total cross section) in the joints, the rotation stiffness of the joints in the linear branch became equal, and, as a result, the displacement in the ring model was the same in all joint types. In addition, it was observed that using a convex joint in the ring model increases the displacement of the ring. The ultimate bending moment of bolted joints was higher than that of joints without bolts, especially in the case of a negative moment. 相似文献
145.
Tertiary reservoir represented by Jeribe, Anah, Azkand, and Azkand/Ibrahim formations has been studied from reservoir characterization point of view in Khabbaz Oil Field/Northern Iraq. Examined thin sections prepared from core rock samples which are selected from the wells Kz-8 and Kz-9 revealed the existence of different microfacies in which are varies types of porosity such as interparticle, intraparticle, moldic, vuggy, and fractures have been noticed. In addition to these different types of diagenetic features are represented mainly by cementation, dolomitization, recrystallization, and dissolution. The available log data for the wells Kz-11, Kz-14, and Kz-16 have been used in characterizing the reservoir properties of the studied formations. The detected lithologies from porosity logs showed domination of limestone, dolomitic limestone, and dolomites in addition to few thin beds of anhydrites in Jeribe Formation and thin beds of sand dominated lithologies in Azkand Formation. Clay content has been calculated from gamma ray log along the studied sections and appeared to be mostly of dispersed clay type as shown from density-neutron porosity crossplot of Thomas-Stieber. Correction from the effect of clay content has been done for all the measured sonic, density, and neutron porosities. The available porosity and permeability values which are measured from core tests in the well Kz-9 for the formations of Jeribe, Anah, and Azkand have been adapted to formalize the best equation for calculating permeability in the other studied wells which have no core test measurements but only log data (Kz-11, Kz-14, and Kz-16 wells). Depending on porosity, permeability, and shale content, the studied sections have been subdivided into seven reservoir units in the wells Kz-11 and Kz-16, and for eight reservoir units in the well Kz-14. 相似文献
146.
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148.
A general pattern for turbulent mixing in the upper layer of the South China Sea (SCS) is presented based on TurboMAP measurements in April and May 2010. The turbulence level decreased significantly overall from north to south, and weakened from east to west in the northern SCS. The average dissipation rate north of 18°N reaches 1.69 × 10?8 W/kg, approximately six times larger than that south of 18°N. The mean mixing efficiency in the SCS is 0.2, with a maximum of 0.31 near the Luzon Strait. At one repeatedly occupied station located in the central deep basin, the dissipation rate varies diurnally in the mixed layer and pycnocline due to diurnal heating and cooling by solar radiation and local barotropic tide, respectively. 相似文献
149.
Anatoly?AleksaninEmail author Vladimir?Kim Vasily?Kachur 《Journal of Oceanography》2016,72(5):801-810
Microwave satellite images used for retrieving sea surface temperatures often have such distortions as noise and blurring of the thermal fronts. An image processing approach based on the Mumford-Shah model of optimal image approximation is considered for the solution to this problem. We divide images into flat areas and frontal zones, and then process these areas separately. Image fragmentation is based on automatic detection of the thermal front lines. SST enhancement in frontal zones is achieved by using image deconvolution methods. It has been shown that SST errors in high gradient areas reach 1–3 °C. The proposed approach can decrease this discrepancy. 相似文献
150.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献