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1.
More than half a century of geological and exploration studies have taken place in the Red Sea area, and still very limited information is available to the geological community in regard to the lithological distribution and the stratigraphic architecture. In this study, extensive well data was used to build the first lithologic and stratigraphic 3D models of the entire Red Sea to better understand the lithological distribution. The potential models have been constrained by bathymetric and geophysical data. Studied data demonstrate that up to 5 km of sediments were deposited in the Red Sea. It is mainly comprised of limestones, evaporites, and shales. Our models show that the evaporite body represents more than 70% of the Red Sea succession. In particular, the evaporite succession seems to be well developed in the southern region. Salt dome features are present and developed close to the margins. The models suggest that domal formation did not enable thick carbonate accumulation in some parts of the basin but the carbonate generally follows the evaporite trend. The models help to identify the main controls leading to salt diapir by highlighting the distribution of this body and the geometry of geological structures. Syn-rift faulting and rifting has been one of the most prominent structural features. Complex interplay of tectono-stratigraphic events played a significant role in shaping the stratigraphic evolution of the Red Sea basin with multiple evolution phases of paleoenvironment and paleogeographic were recognized based on the models. Our synthesis and interpretation support that moderately deep marine conditions dominated in the Miocene, whereas shallow seas dominated the whole basin during the Plio-Pleistocene period as a result of episodic marine invasion. However, lacustrine environment may have prevailed at the Oligocene time in isolated half grabens.  相似文献   
2.
In this paper, we evaluate the predictive performance of an adaptive neuro-fuzzy inference system (ANFIS) using six different membership functions (MF). In combination with a geographic information system (GIS), ANFIS was used for land subsidence susceptibility mapping (LSSM) in the Marand plain, northwest Iran. This area is prone to droughts and low groundwater levels and subsequent land subsidence damages. Therefore, a land subsidence inventory database was created from an extensive field survey. Areas of land subsidence or areas showing initial signs of subsidence were used for training, while one-third of inventory database were reserved for testing and validation. The inventory database randomly divided into three different folds of the same size. One of the folds was chosen for testing and validation. Other two folds was used for training. This process repeated for every fold in the inventory dataset. Thereafter, land subsidence related factors, such as hydrological and topographical factors, were prepared as GIS layers. Areas susceptible to land subsidence were then analyzed using the ANFIS approach, and land subsidence susceptibility maps were created, whereby six different MFs were applied. Lastly, the results derived from each MF were validated with those areas of the land subsidence database that were not used for training. Receiver operating characteristics (ROC) curves were drawn for all LSSMs, and the areas under the curves were calculated. The ROC analyses for the six LSSMs yielded very high prediction values for two out of the six methods, namely the difference of DsigMF (0.958) and GaussMF (0.951). The integration of ANFIS and GIS generally led to high LSSM prediction accuracies. This study demonstrated that the choice of training dataset and the MF significantly affects the results.  相似文献   
3.
The investigation of the impact of different forms of nitrogen fertilizer (NO3-N and NH4-N) on microbial parameters, enzyme activities and phytotoxicity in a petroleum-contaminated soil was evaluated by an incubation study. The tested enzymes, microbial activity and seed germination index showed different patterns in response to both petroleum and nitrogen fertilizer addition and time of incubation. The results apparently showed that the contamination of soil with petroleum has a negative effect on soil ecosystem. Nitrogen fertilizer could improve inhibition of petroleum hydrocarbons in soil. Nevertheless, nitrogen fertilizer had no significant effect on urease activity in the petroleum-contaminated soil. As compared to NO3-N, the addition of NH4-N to the soil resulted in a greater impact on soil performance as attested by the recovery of the soil germination capability and higher values of the respiration. The application of nitrogen fertilizer may be suggested as a good strategy for restoring soils in regions affected by the same problem.  相似文献   
4.
Two formulations for calculating dynamic response of a cylindrical cavity in cross‐anisotropic porous media based on complex functions theory are presented. The basis of the method is the solution of Biot's consolidation equations in the complex plane. Employing two groups of potential functions for solid skeleton and pore fluid (each group includes three functions), the u–w formulation of Biot's equations are solved. Difference of these two solutions refers to use of two various potential functions. Equations for calculating stress, displacement and pore pressure fields of the medium are mentioned based on each two formulations. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
5.
The Neyriz region includes outcrops of metamorphic rocks that are thrust over the Neotethyan ophiolites. These rocks are affected by a major deformational event, the result of which includes a shearing polyphase foliation present in gneissic core domes, overprinted by a crenulation cleavage. These fundamental structures developed contemporaneously with a medium-pressure metamorphism which is characterized by the syn-kinematic crystallization of kyanite and the beginning of anatexis, followed by the development of retrometamorphic mineral parageneses. The major deformation phase in the area occurred during the Early-Cimmerian orogeny in the Late Triassic. Following the orogeny, the gneiss domes started to rise into the upper levels of the crust. From the geodynamic point of view, after the Mid-Permian the studied area was situated at southern passive margin of the Iranian plate; the central Iranian microcontinent at that time was separated by the Neotethys ocean from the Gondwanian supercontinent. After the Late Triassic the region became an active margin associated with an accretionary prism. The margin was finally involved in an orogenic wedge after the closure of the Neotethyan oceanic basin in the Late Mesozoic. Closure of the basin resulted in a major thrusting of the metamorphic rocks of the southern Iranian margin over the Neotethyan ophiolites.  相似文献   
6.
Wind erosion is a serious problem throughout the world which results in soil and environment degradation and air pollution. The main objective of this study was to evaluate feasibility of microbial-induced carbonate precipitation, as a novel soil-strengthening technique, to reduce wind erosion risk of a sandy soil. For this purpose, the erosion of biocemented soil samples was investigated experimentally in a wind tunnel under the condition of wind velocity of 45 km h?1. The weight loss of treated samples relative to the weight loss of control treatment was 1.29 and 0.16 % for low and high bacterial mix concentrations, respectively, indicating a significant improvement in erosion control in biologically treated samples. The effect of biological treatment on wind erosion control was even superior at the higher velocities. Thereafter, the penetration resistance of the surface layers as a simple index of resistance against wind erosion was measured. Significant improvements in the penetration resistance of the treated soil samples were observed. Although low bacterial mix concentrations did not significantly improve the penetration resistance of the samples, significant improvements in the penetration resistance of the treated soil samples were observed reaching to the highest measured strength (56 kPa) in high bacterial mix concentrations samples. Finally, the morphology of precipitated CaCO3 crystals using scanning electron microscopy and X-ray powder diffraction analysis showed that the CaCO3 was mainly precipitated as vaterite crystals forming point-to-point contacts between the sand granules.  相似文献   
7.
Geotechnical and Geological Engineering - Mulching is fastest strategy to control sand dune movement in arid and semiarid areas. In the present study the effect of micro silica- cement mixture was...  相似文献   
8.
The Myall Creek copper prospect is in unmetamorphosed carbonaceous dolosiltstone and sandstone at the base of the late Proterozoic (Adelaidean) Tapley Hill Formation. It contains disseminated, fine-grained chalcopyrite, zincian tennanite, bornite, chalcocite, pyrite, sphalerite and galena, and irregular to straight chalcopyrite-rich veinlets. Some ore minerals rim and/or partially replace pyrite or clastic grains. There is no evidence of hydrothermal activity. The 34SCDT values of pyrite and the other sulfides fall in the wide range –3.6 to +44.2. Dolomite in both mineralised and unmineralised samples has 13CPDB values concentrated around –3, and 18OSMOW values around +25. It is concluded that the mineralising fluids were near-neutral brines which leached metals from the basement and early Adelaidean rocks. They entered the Tapley Hill sediments at moderately low temperatures via permeable strata and faults. The metals were precipitated by biogenic H2S, and also fixed by reaction with iron sulfides and, possibly, organic matter. Continuing ascent of brines into the mineralised strata caused breakdown of detrital feldspars and Fe-Ti oxides, and some solution-remobilisation of early-formed sulfides.  相似文献   
9.
The Laal-Kan fluorite deposit (west of Zanjan city, NW Iran) mainly occurred as some open-space filling and vein/veinlet in the schist of the Paleozoic age. Mineralogically, calcite, fluorite types (white, smoky, and violet), and quartz are the principal constituents accompanied by a number of minor accessory minerals such as hemimorphite, hematite, barite, and clays. Based on chemical analyses, fluorites of various colors were found to have low rare earth element (REE) concentrations (4.16–25.67 ppm). The chondrite-normalized REE patterns indicated that early fluorites were enriched in LREE, relative to HREE, whereas late fluorites were enriched in HREE relative to LREE. This study, therefore, indicated that fugacity of oxygen likely played a significant role in the occurrence of positive Ce and negative anomaly in the late fluorite. Furthermore, the Gd behavior of the fluorite samples could be attributed to the Gd-F complex in ore-forming fluids. On the other hand, low pH hydrothermal fluids under alkaline conditions were probably the main mechanism responsible for the deposition of the early fluorites in this district. Fluorite-hosted fluid inclusion analyses also indicated that fluorite-forming fluids consisted of NaCl, MgCl2, CaCl2, and LiCl with a narrow TH (118–151 °C) and high salinities (18.96–23.47 wt.% NaCl equiv.). Further, the diagram of Tb/La-Tb/Ca ratios revealed that fluorites were predominantly deposited in the hydrothermal environment and the late stage fluorites could be considered as the product of the secondary mineralization of the early fluorites due to the interaction of the fluid with the early fluorites.  相似文献   
10.
The textural and geochemical aspects of the sediments of subtropical mangrove ecosystem and surrounding areas have been studied and discussed. Forty sediment samples were collected from different areas of mangrove environment and surrounding areas along the Egyptian Red Sea coast. The sediments of each study areas are characterized by the abundance of sand with minor amounts of mud and gravel. The mean size of the sediments ranged from medium grained to fine grained at the study areas. Cluster analysis showed that the distribution of gravel, sand, and mud fractions is related to bottom facies and type of sediment source. Generally, sand fraction is the main category among the three constituents. Carbonate content recorded minor values in the study areas. The CaCo3 content of the sediments ranged from 4.7 % at Hamata area to 64.9 % at Erier area. Terrigenous and biogenic components are the factor controlling of the carbonate content of studies sediments. The organic carbon content ranged from 1.10 at Hamata area to 3.1 % at Sharm el-Qibli and Erier areas, which is controlled by particle size of the sediments. Phosphorus content in the different studied localities is related to the sources of phosphorus to the area. Our observations provide evidence that there are no significant differences in environmental texture and geochemistry of the sediments of subtropical mangrove ecosystem and surrounding areas of the Egyptian Red Sea coast.  相似文献   
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