Source and origin of glacial paleovalley-fill sediments (Upper Ordovician) of Sarah Formation in central Saudi Arabia     

Omar A. Al-Harbi  M. Mujtaba Khan 《Arabian Journal of Geosciences》2011,4(5-6):825-835

A study was carried out on the combination of petrographies, geochemistry (major and trace), weathering and the digenesis of 31 sandstones samples to determine their provenance and depositional tectonic setting of sedimentary basins. Based on the composition of Detrital grains (point counting), most of the Sarah sandstones were classified as quartz arenites types (99% on an average). The petrographic data indicated that the resultant mature sandstones are derived from recycled and craton interior tectonic provenance. Tectonic setting discrimination diagrams based on major elements suggest that sandstones were deposited in a passive margin and polycyclic continental tectonic setting. The relationship between K₂O/Na₂O ratio and SiO₂ showed that the Sarah sandstone samples fall into the passive margin field. The chemical index of alteration (CIA?=?63.84%) of sandstones suggested moderate weathering or reworking in the area. The concentration of trace elements indicates that the sediments were probably derived from the mixed sedimentary-meta sedimentary provenance and changes in sedimentary process due to climatic variations. The main diagenetic events were in the form of cements, which occur as grain coats and as pore fillings. An integrated approach showed that the parent area of paleovalley-fill sediment is probably a complex of granite, metasedimentary and pre-existing sedimentary rocks.  相似文献   

Strike-slip faults parallel to crustal spreading axes: data from Iceland and the Afar Depression     

Pietro Passerini  Marta Marcucci  Giovanni Sguazzoni  Leonardo Zan  Abdourahman Omar Haga 《地学学报》1991,3(6):607-618

Slickenside studies in regions of crustal spreading such as Iceland and the Afar Depression, East Africa, reveal that a significant number of faults parallel and close to rift axes are strike-slip rather than normal. Therefore, the pattern of brittle deformation in these regions does not conform to the classic two-dimensional schemes of oceanic tectonics and pre-oceanic rifting. Dip-slip and strike-slip faulting presumably alternated along or in the vicinity of spreading axes, indicate a varying stress field and a combination of transverse and longitudinal movements. In Iceland, strike-slip faults parallel to rifts are observed both west and east of the rift system as well as in a median area between overlapping rifts; the mechanisms proposed for their origin include accommodation of oblique convergence or divergence of crustal sections due to variations of spreading directions along axis and the interaction of overlapping rifts. In the Afar Depression this kind of fault is recorded west of the rift of Asal and can be imputed to reflect an interaction among rifts in the vicinity of the Afar triple junction. Rift-parallel strike-slip faults cannot however be assumed to be a feature of all crustal spreading axes due to the peculiarity of the examined regions: both of them are hot-spot areas and the Afar Depression lies at a triple junction.  相似文献   

Advanced Mathematical Models to Predict the Compaction Properties of Coarse-Grained Soils from Various Physical Properties     

Maher Omar  Abdallah Shanableh  Mohamed Arab  Khaled Hamad  Ali Tahmaz 《Geotechnical and Geological Engineering》2018,36(6):3467-3483

An essential task in the process of construction is the determination of compaction properties of soils. Many years of laboratory test experience strengthen our belief in the existence of predictive equations that govern the compaction characteristics of soils. An advanced mathematical model developed in this research in order to uncertain the governing equations. An advanced mathematical model developed in this research in order to uncertain the governing equations. Through a comparative study among a Multiple Linear Regression (MLR) model, an Artificial Neural Network (ANN) model, Extreme Learning Machine (ELM) and a Support Vector Machine (SVM) model, the best predicting model was determined. For this purpose, Six hundred and six (606) samples collected and split into a dataset used for training the models and another used for validation of the derived model. 8 neural networks with a varying number of hidden layers and a varying number of nodes in hidden layers were employed. In ELM 1 hidden layer with varying number of units were employed. It was found that the equations derived from the ELM models described the relationship with superiority over multiple regression, ANN and SVM models for Maximum Dry Density and MLR models described the relationship with superiority over ANN, ELM and SVM models for Optimum Moisture Content.  相似文献   

Time-series maps of aboveground biomass in dipterocarps forests of Malaysia from PALSAR and PALSAR-2 polarimetric data     

Hamdan Omar  Muhamad Afizzul Misman 《Carbon balance and management》2018,13(1):19

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Palynological evidences on paleoclimate and paleoenvironmental changes during Holocene of Al-Hussaynia District,Central Iraq     

Maysoon Omar Ali 《Arabian Journal of Geosciences》2014,7(2):589-595

This paper is concerned with the study of paleoclimate and paleoenvironmental changes of Hussaynia township which is located in Karbala at the center of the Mesopotamian plain during Holocene. Ten soil samples were examined to determine their content of pollens, spores, and marine organisms (dinoflagellates). These palynomorphs include: Graminidites, Palmaepollenites, Chenopodiaceae, Composita, Cyperaceae, Sphaginum sporites, Pinus pollenites, Convovolus, Artimesia, Laevigatosporites, Quercus, dinoflagellates, and fungi. The study revealed climatic and environmental changes in the area during Holocene and four climatic zones were determined in the studied sequence and correlated with other areas in and outside of Iraq. The climate was pluvial with intervening dry periods in the 10000 years?bp. The study indicated as well, some marine effects on the studied area on the commencement of Holocene due to the global transgression. This is based on the presence of marine organisms, dinoflagellate.  相似文献   

Manifestation of Remote Sensing Data in Modeling Urban Sprawl Using the SLEUTH Model and Brute Force Calibration: A Case Study of Sana’a City, Yemen     

Mohamed Al-shalabi  Biswajeet Pradhan  Lawal Billa  Shattri Mansor  Omar F. Althuwaynee 《Journal of the Indian Society of Remote Sensing》2013,41(2):405-416

Sana’a the metropolitan capital of Yemen, has experienced rapid spatial growth and uncontrolled development for decades. In the absence of a means to forecast and predict urban growth trends, planning and urban policy decisions have been found wanting. In this study the SLEUTH (Slope, landuse, exclusion, urban extent, transportation and hillshade) model which has been widely and successfully applied in developed countries, has been applied to predict the spatial urban sprawl pattern from 2004–2020 in Sana’a. This was to provide the necessary forecast for better planning and decision making. The model performed well as per the calibration coefficient values. The results showed that there will a 29 % increase in spatial urban sprawl growth during the modeling period. Growth of the sprawl will be mainly at the edges of the urban boundary, there will also be a wide area of scattered urban clusters. Factors that will have major influence on spatial expansion of the city will be diffusion, natural and internal growth, slope (that will hinder spread) and transportation (along which most of the urban sprawl will occur). The study also provides an insight into how the SLEUTH model performs in a poorly planned urban environment as compared to the planned and controlled environment where it has been applied.  相似文献   

Methodology and applications for the benefit cost analysis of the seismic risk reduction in building portfolios at broadscale     

Jairo A. Valcárcel  Miguel G. Mora  Omar D. Cardona  Lluis G. Pujades  Alex H. Barbat  Gabriel A. Bernal 《Natural Hazards》2013,69(1):845-868

This article presents a methodology for an estimate of the benefit cost ratio of the seismic risk reduction in buildings portfolio at broadscale, for a world region, allowing comparing the results obtained for the countries belonging to that region. This methodology encompasses (1) the generation of a set of random seismic events and the evaluation of the spectral accelerations at the buildings location; (2) the estimation of the buildings built area, the economic value, as well as the classification in structural typologies; (3) the development of vulnerability curves for each typology; (4) the estimation of the annual average loss of the buildings portfolio in the current conditions as well as in the case of a hypothetical structural intervention. The benefit cost ratio is estimated as the difference between the estimates of the present value of these two annual average losses, divided by the retrofitting costs. This methodology has been applied to the portfolio of public schools of 14 countries of Latin America and the Caribbean, for evaluating the feasibility of the seismic risk reduction at a national scale.  相似文献   

Assessment of groundwater quality and its suitability for drinking and agricultural uses in arid environment     

Omar Ali Al-Khashman  Aiman Qasem Jaradat 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):743-753

Groundwater quality in Ma’an area was evaluated for its suitability for drinking and agricultural uses by determining the main physical and chemical properties during a 1 year survey study (August 2009 to August 2010). Several samples were collected from ten different wells and analysed for temperature, pH, conductivity, total dissolved solids, total hardness, major cations (Ca²⁺, Mg²⁺, Na⁺ and K⁺), major anions (HCO₃ ^?, Cl^?, NO₃ ^?, SO₄ ^2?, F^? and Br^?) and trace metals (Fe²⁺, Al³⁺, Mn²⁺, Cu²⁺, Zn²⁺, Pb²⁺ and Cd²⁺). The general chemistry of water samples was typically of alkaline earth waters with prevailing bicarbonate chloride. The results showed great variations among the analyzed samples with respect to their physical and chemical parameters. However, most values were below the maximum permissible levels recommended by Jordanian and WHO drinking water standards. The quality assessment shows that in general, the GW in the study area is not entirely fit for direct drinking with respect to EC, and Pb²⁺. According to the residual sodium carbonate and sodium adsorption ratio, the water in the studied wells can be used for irrigational purposes.  相似文献   

Hydrological effects of the increased CO2 and climate change in the Upper Mississippi River Basin using a modified SWAT   总被引：1，自引：0，他引：1  

Yiping Wu  Shuguang Liu  Omar I. Abdul-Aziz 《Climatic change》2012,110(3-4):977-1003

Increased atmospheric CO₂ concentration and climate change may significantly impact the hydrological and meteorological processes of a watershed system. Quantifying and understanding hydrological responses to elevated ambient CO₂ and climate change is, therefore, critical for formulating adaptive strategies for an appropriate management of water resources. In this study, the Soil and Water Assessment Tool (SWAT) model was applied to assess the effects of increased CO₂ concentration and climate change in the Upper Mississippi River Basin (UMRB). The standard SWAT model was modified to represent more mechanistic vegetation type specific responses of stomatal conductance reduction and leaf area increase to elevated CO₂ based on physiological studies. For estimating the historical impacts of increased CO₂ in the recent past decades, the incremental (i.e., dynamic) rises of CO₂ concentration at a monthly time-scale were also introduced into the model. Our study results indicated that about 1–4% of the streamflow in the UMRB during 1986 through 2008 could be attributed to the elevated CO₂ concentration. In addition to evaluating a range of future climate sensitivity scenarios, the climate projections by four General Circulation Models (GCMs) under different greenhouse gas emission scenarios were used to predict the hydrological effects in the late twenty-first century (2071–2100). Our simulations demonstrated that the water yield would increase in spring and substantially decrease in summer, while soil moisture would rise in spring and decline in summer. Such an uneven distribution of water with higher variability compared to the baseline level (1961–1990) may cause an increased risk of both flooding and drought events in the basin.  相似文献   

Reintegrating nanogranitoid inclusion composition to reconstruct the prograde history of melt-depleted rocks     

Omar Bartoli 《地学前缘(英文版)》2019,10(2):517-525

A recent fascinating development in the study of high-grade metamorphic basements is represented by the finding of tiny inclusions of crystallized melt(nanogranitoid inclusions) hosted in peritectic phases of migmatites and granulites. These inclusions have the potential to provide the primary composition of crustal melts at the source. A novel use of the recently-published nanogranitoid compositional database is presented here. Using granulites from the world-renowned Ivrea Zone(NW Italy) on which the original melt-reintegration approach has been previously applied, it is shown that reintegrating melt inclusion compositions from the published database into residual rock compositions can be a further useful method to reconstruct a plausible prograde history of melt-depleted rocks. This reconstruction is fundamental to investigate the tectonothermal history of geological terranes.  相似文献