An overview of the diagenesis of the Upper Jurassic carbonates of Jubaila and Hanifa formations, central Saudi Arabia     

Mohammed H. Basyoni  Mohammed Khalil 《Arabian Journal of Geosciences》2013,6(2):557-572

The Jubaila Formation (Upper Jurassic) in central Saudi Arabia has been divided into lower, middle, and upper parts purely on lithologic grounds. Each part consists of a major lower unit of lime mudstone and a minor upper unit of grainstone. This persistent change in the limestone facies is interpreted as a reflection of repeated shoaling up in the depositional shelf environment. It is a normal marine carbonate sequence that varies in thickness from 85 to 126 m. In the Hanifa Formation, the lowermost brown ledges in the section comprise a series of coarsening upward sequences which generally terminate in a fossiliferous/peloidal packstone and grainstone and subordinately lime mudstone facies. The middle slope member is yellow, blocky weathered shale and marl. Above this slope member are several thick beds of brown-coated fossiliferous wackestone, packstone, and grainstone with the association of lime mudstone in certain levels. These are fairly resistant ledges due to the occurrence of stromatoporoids. Dedolomitization occurs in the Jubaila Formation in various textural forms which include composite calcite rhombohedra, zonal dedolomitization, regeneration of predolomitization fabric of the limestone, and coarsely crystalline calcite mosaics with or without ferric oxide rhombic zones. Rhombohedral pores commonly occur in intimate association with dolomite, possibly resulting from the leaching of calcitized dolomite rhombohedra. The regional dedolomitization was most likely brought about by calcium sulfate solutions reacting with dolomites. The source of sulfate solutions is the dissolved anhydrite deposits of the Arab–Hith Formations, sometime before their erosion, and it takes place at or near an exposed surface. The Hanifa Formation shows various diagenetic features. These include dolomitization, dedolomitization, micritization, cementation, and recrystallization. Most of the examined samples of the Hanifa carbonates are dolomitized and subsequently dedolomitized as evidenced by the presence of iron-coated dolomite rhombs partially or completely calcitized. Dolomite also occurs in the lime mudstone, wackestone, packstone, and grainstone facies, while leaching of wackestone and packstone and dedolomitization of dolomite and dolomitic limestone followed by recrystallization are common processes.  相似文献   

Computer Vision for the Solar Dynamics Observatory (SDO)     

P. C. H. Martens  G. D. R. Attrill  A. R. Davey  A. Engell  S. Farid  P. C. Grigis  J. Kasper  K. Korreck  S. H. Saar  A. Savcheva  Y. Su  P. Testa  M. Wills-Davey  P. N. Bernasconi  N.-E. Raouafi  V. A. Delouille  J. F. Hochedez  J. W. Cirtain  C. E. DeForest  R. A. Angryk  I. De Moortel  T. Wiegelmann  M. K. Georgoulis  R. T. J. McAteer  R. P. Timmons 《Solar physics》2012,275(1-2):79-113

In Fall 2008 NASA selected a large international consortium to produce a comprehensive automated feature-recognition system for the Solar Dynamics Observatory (SDO). The SDO data that we consider are all of the Atmospheric Imaging Assembly (AIA) images plus surface magnetic-field images from the Helioseismic and Magnetic Imager (HMI). We produce robust, very efficient, professionally coded software modules that can keep up with the SDO data stream and detect, trace, and analyze numerous phenomena, including flares, sigmoids, filaments, coronal dimmings, polarity inversion lines, sunspots, X-ray bright points, active regions, coronal holes, EIT waves, coronal mass ejections (CMEs), coronal oscillations, and jets. We also track the emergence and evolution of magnetic elements down to the smallest detectable features and will provide at least four full-disk, nonlinear, force-free magnetic field extrapolations per day. The detection of CMEs and filaments is accomplished with Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) and ground-based Hα data, respectively. A?completely new software element is a trainable feature-detection module based on a generalized image-classification algorithm. Such a trainable module can be used to find features that have not yet been discovered (as, for example, sigmoids were in the pre-Yohkoh era). Our codes will produce entries in the Heliophysics Events Knowledgebase (HEK) as well as produce complete catalogs for results that are too numerous for inclusion in the HEK, such as the X-ray bright-point metadata. This will permit users to locate data on individual events as well as carry out statistical studies on large numbers of events, using the interface provided by the Virtual Solar Observatory. The operations concept for our computer vision system is that the data will be analyzed in near real time as soon as they arrive at the SDO Joint Science Operations Center and have undergone basic processing. This will allow the system to produce timely space-weather alerts and to guide the selection and production of quicklook images and movies, in addition to its prime mission of enabling solar science. We briefly describe the complex and unique data-processing pipeline, consisting of the hardware and control software required to handle the SDO data stream and accommodate the computer-vision modules, which has been set up at the Lockheed-Martin Space Astrophysics Laboratory (LMSAL), with an identical copy at the Smithsonian Astrophysical Observatory (SAO).  相似文献   

Monitoring the evolution of irrigated areas with Landsat images using backward and forward change detection analysis in the Kou watershed,Burkina Faso     

Farid Traoré  Yves Cornet  Antoine Denis  Joost Wellens  Bernard Tychon 《国际地球制图》2013,28(8):733-752

The Kou watershed is characterized by important water resources used for drinking, agriculture (especially in the irrigated areas), industry and the preservation of aquatic fauna and flora. For several decades, there has been increasing pressure on the Kou's water resources, partly because of the expansion of the irrigated agricultural areas. This study was conducted to examine this issue, focusing on one specific irrigated area. In order to monitor the expansion of irrigated areas in developing countries, a low-cost remote sensing method based on Landsat images and aerial photographs was developed. The method is based on maximum-likelihood classification, followed by backward and forward change detection analysis requiring agronomic expertise. Using pixel trajectory analysis, the method connects all pixels to their consecutive states in order to correct their current states. The study showed that the irrigated area has expanded by almost 70% over 20 years, with most of this expansion occurring in the past 10 years. The method, if validated, could be used to obtain better information on past occupation in the rural irrigated areas for which there is currently no archived data, making temporal analyses impossible.  相似文献   

Properties of a diffuse interface model based on a porous medium theory for solid–liquid dissolution problems     

Haishan Luo  Michel Quintard  Gérald Debenest  Farid Laouafa 《Computational Geosciences》2012,16(4):913-932

In this paper, a local non-equilibrium diffuse interface model is introduced for describing solid–liquid dissolution problems. The model is developed based on the analysis of Golfier et al. (J Fluid Mech 457:213–254, 2002) upon the dissolution of a porous domain, with the additional requirement that density variations with the mass fraction are taken into account. The control equations are generated by the upscaling of the balance equations for a solid–liquid dissolution using a volume averaging theory. This results into a diffuse interface model (DIM) that does not require an explicit treatment of the dissolving interface, e.g., the use of arbitrary Lagrangian–Eulerian (ALE) methods, for instance. Test cases were performed to study the features and influences of the effective coefficients inside the DIM. In particular, an optimum expression for the solid–liquid exchange coefficient is obtained from a comparison with the referenced solution by ALE simulations. Finally, a Ra–Pe diagram illustrates the interaction of natural convection and forced convection in the dissolution problem.  相似文献   

Arsenic in the Muteh gold mining district, Isfahan, Iran   总被引：1，自引：1，他引：0  

Behnam Keshavarzi  Farid Moore  Fatemeh Rastmanesh  Maryam Kermani 《Environmental Earth Sciences》2012,67(4):959-970

Following the appearance of symptoms of arsenic toxicity in the inhabitants of villages in the Muteh gold mining region, central Iran, the concentration of this element in various parts of biogeochemical cycle is investigated. For this purpose, rock, groundwater, soil, plant, livestock hair and wool, and human hair samples are collected and analysed. Total arsenic content ranges from 23 to 2,500?mg/kg in rock samples, 7?C1,061???g/l in water, 12?C232?mg/kg in soil, 0.5?C16?mg/kg in plant samples, 4.10?C5.69?mg/kg in livestock hair and wool, and 0.64?C5.82?mg/kg in human hair. Arsenic concentration in various parts of biogeochemical cycle near the gold deposit in a metamorphic complex, and also close to the gold-processing plant, is very high and decreases exponentially with increasing distance from them. Arsenic concentration in water from a well close to the Muteh gold mine is above 1?mg/L. Arsenic in hair samples taken from local inhabitants is above the recommended levels, and the control samples in Shahre-Kord city. Arsenic concentration is higher in male population and correlates positively with age. It is suggested that arsenic resulting from the decomposition of ore mineral such as orpiment (As₂S₃), realgar (As₂S₂) and arsenopyrite (FeAsS) is responsible for polluting natural resources and the human intake via drinking water and the food chain. Gold mining and processing has undoubtedly enhanced the release of arsenic and intensified the observed adverse effects in Muteh area.  相似文献   

Stable isotopes of carbon and nitrogen in suspended matter and sediments from the Godavari estuary   总被引：2，自引：0，他引：2  

V. V. S. S. Sarma  J. Arya  Ch. V. Subbaiah  S. A. Naidu  L. Gawade  P. Praveen Kumar  N. P. C. Reddy 《Journal of Oceanography》2012,68(2):307-319

Spatial distribution of the carbon and nitrogen content and their isotopic enrichment in suspended matter and sediments were measured in the Godavari estuary to identify the sources and transformation mechanism of organic matter. Significant variability in isotopic distribution was found over the entire length of the Godavari estuary, suggesting multiple sources of organic matter. The mean isotopic ratios (δ¹³C_sed −25.1 ± 0.9, δ¹³C_sus −24.9 ± 1, δ¹⁵N_sed 8.0 ± 2 and δ¹⁵N_sus 6.5 ± 0.9‰) and elemental concentrations (C_sed 0.45 ± 0.2%, C_sus 0.9 ± 0.7%, N_sed 0.07 ± 0.05% and N_sus 0.16 ± 0.1%) support a predominantly terrigenous source. Significant enrichment in the isotopic ratios of δ¹³C from the upper to lower estuary in both suspended (−27.5 and −24.3‰, respectively) and sedimentary (−26.2 and −24.9‰, respectively) phases indicates a decrease in the influence of terrigeneous material toward the mouth of the estuary. A significant positive relationship exists between the δ¹³C of suspended and sediment, which indicates that these two organic carbon pools are likely coupled in the form of a significant exchange between the two phases. A positive relationship exists between chlorophyll a and suspended organic matter, which may mean that a significant source of organic carbon is the in situ produced phytoplankton. But, applying a simple mixing model to our isotopes, data yielded about 46% as the contribution of the terrestrial source to suspended matter, which may support the excessive heterotrophic activity in the Godavari estuary reported earlier.  相似文献   

Heavy metal toxicity levels in the coastal sediments of the Arabian Sea along the urban Karachi (Pakistan) region   总被引：1，自引：0，他引：1  

Azhar Siddique  Majid Mumtaz  Nayyer A. Zaigham  Khalil A. Mallick  Sumayya Saied  Erum Zahir  Haider A. Khwaja 《Marine pollution bulletin》2009,58(9):1406-1414

  相似文献   

Geomorphology of the Alluvial Sediments and Bedrock in an Intermontane Basin: Application of Variogram Modeling to Electrical Resistivity Soundings     

Adnan Ahmad Khan  Asam Farid  Gulraiz Akhter  Khyzer Munir  James Small  Zulfiqar Ahmad 《Surveys in Geophysics》2016,37(3):579-599

The study describes a methodology used to integrate legacy resistivity data with limited geological data in order to build three-dimensional models of the near subsurface. Variogram analysis and inversion techniques more typically found in the petroleum industry are applied to a set of 1D resistivity data taken from electrical surveys conducted in the 1980s. Through careful integration with limited geological data collected from boreholes and outcrops, the resultant model can be visualized in three dimensions to depict alluvium layers as lithological and structural units within the bedrock. By tuning the variogram parameters to account for directionality, it is possible to visualize the individual lithofacies and geomorphological features in the subsurface. In this study, an electrical resistivity data set collected as part of a groundwater study in an area of the Peshawar basin in Pakistan has been re-examined. Additional lithological logs from boreholes throughout the area have been combined with local outcrop information to calibrate the data. Tectonic activity during the Himalayan orogeny has caused uplift in the area and generated significant faulting in the bedrock resulting in the formation of depressions which are identified by low resistivity values representing clays. Paleo-streams have reworked these clays which have been eroded and replaced by gravel–sand facies along paleo-channels. It is concluded that the sediments have been deposited as prograding fan-shaped bodies and lacustrine deposits with interlayered gravel–sand and clay–silt facies. The Naranji area aquifer system has thus been formed as a result of local tectonic activity with fluvial erosion and deposition and is characterized by coarse sediments with high electrical resistivities.  相似文献   

Pattern recognition of major asperities using local recurrence time in Alborz Mountains, Northern Iran     

Khalil Motaghi  Khaled Hessami  Mohammad Tatar 《Journal of Seismology》2010,14(4):787-802

In this study, seismic data recorded during the period 01/01/1996 to 09/01/2009 has been used to evaluate the seismic hazard potential along the Alborz region, Northern Iran. The technique of mapping local recurrence time, T _L, is used to map major asperities, which are considered as the areas with maximum hazard. We calculated T _L from a and b values which are in turn derived from the frequency–magnitude relation constants within a radius of 30 km about every corner point of a 10-km spacing grid. Since b value is inversely related to applied stress, the areas with lowest b values and/or shortest T _L are interpreted to locate the asperities or the areas of maximum seismic hazard. To test this method, we computed T _L map using seismic catalogues before and after the 2004 Baladeh earthquake of M _w 6.2. The local recurrence time map before the earthquake shows anomalously short T _L in the epicentral region of the Baladeh earthquake a decade before its occurrence. The T _L map after the earthquake indicates that this large event has redistributed the applied stress in the Alborz region. The microseismicity of the region after the Baladeh earthquake, however, suggests that there are two anomalies in T _L map positioned in Alborz. The places where these anomalies are observed can be considered as the areas with maximum seismic hazard for future large earthquake in the Alborz region.  相似文献   

Simulation of groundwater level in a coastal aquifer     

Mohammad-Mahdi Ansarifar  Khalil Ghorbani  Abdol-Reza Kaboli 《Marine Georesources & Geotechnology》2020,38(3):257-265

Abstract

The groundwater levels can have a significant impact on structures and infrastructures of coastal areas. The simulation of the hydraulic behavior of coastal aquifers is very important due to its specific boundary conditions. In this study, the groundwater level in the Bandar-e-Gaz coastal aquifer in the Gorgan Gulf region located in northern Iran is simulated using the MODFLOW mathematical model. The modeling of the coastal aquifer behavior carried out in two calibrations (steady and unsteady states). The validation periods (unsteady state), the mean absolute error (MAE) and mean bias error (MBE) were used to evaluate the results. The values of MAE and MBE criteria for the steady state were 0.31 (m) and –0.08 (m), while the average of these criteria in the unsteady state in calibration period were 0.46 and –0.39, and in the validation period were 0.42 (m) and –0.31 (m), respectively. The mentioned results confirm the precision of the model for the entire simulation period, they also indicate that the simulation has a limited underestimation behavior. Moreover, it shows that the precision of the results has a negligible variability, which means the simulation also has considerable reliability. The highest and lowest amount of error in the winter and summer seasons are in accordance with the lowest and highest seawater levels, and it shows the significant sea effect on the hydraulic behavior of the coastal aquifer.  相似文献