Mixed carbonate-siliciclastic sedimentation on a Miocene fault-block,Gulf of Suez,Egypt     

A. El Haddad  D.M. Aissaoui  M.A. Soliman 《Sedimentary Geology》1984,37(3):185-202

The Miocene sediments at Abu Shaar (Red Sea, Egypt) include both carbonates and detrital silicates whose distribution is closely related to a pre-Miocene basement fault-block. As such, they demonstrate the relationships between local distensional tectonics and sedimentation. Because of the vertical bathymetric relief of the basement block, the carbonates include both a spectacular talus and massive platform facies. In spite of the presence of scattered corals, sedimentation is not truly reefal as deposits consist essentially of muddy bioclastic and silicate sands. The most typical ecological elements are numerous spectacular stromatolites. Rigidity of the sedimentary mass was mainly induced by early marine cementation. Carbonate-siliciclastic transitions on and around the Abu Shaar platform were determined mainly by basement morphology and related pre-Miocene tectonics.  相似文献   

A change-detection application on the evolution of Kahak playa (South Khorasan province, Iran)     

Mohammad Hossein Rezaei Moghaddam  Mahdi Saghafi 《Environmental Geology》2006,51(4):565-579

Kahak salt playa in South Khorasan province of Iran, have special geomorphological characteristics by the presence of ephemeral saline lakes, wetlands, salt crusts, surface accumulations of salt and zones of patterned ground. Salt crusts in the soil surface are unique in the region and have laminated horizons in the playa soil. Soil-surface salt accumulations are dominated by NaCl and gypsum. It has been found that distribution of chemical soluble is not uniform across the playa landscape, and this result influences on the variety form of patterned ground. In this study, the percent changes in some of the chemical elements such as NaCl, gypsum and also brine extent have been calculated in the playa. Indicating changes in Kahak salt playa is the main aim of this study by using remote sensing and GIS techniques. In this paper, techniques such as spectral un-mixing, maximum likelihood classification, band rationing, fuzzy classification and correlation relationships are discussed. This contribution presents modeling of temporal and spatial changes of salinity and playa developing using combined approaches that incorporate different data-fusion and data-integration techniques for two periods of date. Furthermore, percent changes in the surface-patterned ground of the playa have been calculated using texture and pattern analysis of the PCA1. Results have revealed that, in the playa developing, chemical materials such as sodium, NaCl, gypsum and also brine extent are positively correlated with each other and the most increased changes are related to gypsum and the most decreased changes are related to the NaCl. Also changes in the amount of agricultural area in the playa-lakes margin, show low effects in the desertification process.  相似文献   

Pairing geotechnics and fluvial hydraulics for the prediction of the hazard zones of an exceptional flooding     

T. Mahdi 《Natural Hazards》2007,42(1):225-236

The direct consequences of exceptional floods are usually considered to be limited to the maximum flooding zone created downstream. However, considering the magnitude of the flows, the morphology of the flooded zone could undergo deep changes. To predict the hazard zone on a river undergoing exceptional flooding, numerical simulations are widely used. In this article, the simulation of the evolution of river reaches resulting from such catastrophic events is performed by coupling the hydraulic and sediment transport numerical model GSTARS with a developed slope stability model based on the Bishop’s simplified method. This is a novel methodology for the delimitation of hazard zones along riverbanks by taking into consideration not only the flood risks but also the possible induced landslides. Indeed, each section of the river reach is subject to changes caused by the river hydraulics and the associated erosion or sediment deposition and also undergoes profile changes caused by possible landslides. The initial hydraulic and geotechnical characteristics are first defined and then used to test the stability of several slopes of representative sections of the river reaches before the dam break. Validation tests are performed on specific reaches of the Outaouais River (Quebec) undergoing a dam break flood.  相似文献   

Global morphology of ionospheric sporadic E layer from the FormoSat-3/COSMIC GPS radio occultation experiment     

Lung-Chih Tsai  Shin-Yi Su  Chao-Han Liu  Harald Schuh  Jens Wickert  Mohamad Mahdi Alizadeh 《GPS Solutions》2018,22(4):118

Ionospheric sporadic-E (Es) activity and global morphology were studied using the 50 Hz signal-to-noise ratio amplitude and excess phase measurements from the FormoSat-3/Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) GPS radio occultation (RO) observations. The results are presented for data collected during the last sunspot cycle from mid-2006 to the end of 2017. The FS3/COSMIC generally performed more than 1000 complete E-region GPS RO observations per day, which were used to retrieve normalized L1-band amplitude standard deviation (SDL1) and relative electron density (N_e) profiles successfully. More or less 31% of those observations were identified as Es events based on SDL1 and peak SDL1 altitude criteria. We found that the peak Es-event i values are approximately proportional to the logarithms of the corresponding peak N_e differences. Five major geographical zones were identified, in which the seasonal and diurnal Es occurrence patterns are markedly different. These five zones include the geomagnetic equatorial zone (??5°?<?magnetic latitude (ML)?<?5°), two extended geomagnetic mid-latitude zones (15°?<?ML?<?55°, and ??55°?<?ML < ??15°), and two auroral zones (70°?<?ML, and ML < ??70°). The Es climatology, namely its variations with each identified zone, altitude, season, and local time has been documented.  相似文献   

Evaluation of deep learning algorithms for national scale landslide susceptibility mapping of Iran     

Phuong Thao Thi Ngo  Mahdi Panahi  Khabat Khosravi  Omid Ghorbanzadeh  Narges Kariminejad  Artemi Cerda  Saro Lee 《地学前缘(英文版)》2021,12(2):505-519

The identification of landslide-prone areas is an essential step in landslide hazard assessment and mitigation of landslide-related losses.In this study,we applied two novel deep learning algorithms,the recurrent neural network(RNN)and convolutional neural network(CNN),for national-scale landslide susceptibility mapping of Iran.We prepared a dataset comprising 4069 historical landslide locations and 11 conditioning factors(altitude,slope degree,profile curvature,distance to river,aspect,plan curvature,distance to road,distance to fault,rainfall,geology and land-sue)to construct a geospatial database and divided the data into the training and the testing dataset.We then developed RNN and CNN algorithms to generate landslide susceptibility maps of Iran using the training dataset.We calculated the receiver operating characteristic(ROC)curve and used the area under the curve(AUC)for the quantitative evaluation of the landslide susceptibility maps using the testing dataset.Better performance in both the training and testing phases was provided by the RNN algorithm(AUC=0.88)than by the CNN algorithm(AUC=0.85).Finally,we calculated areas of susceptibility for each province and found that 6%and 14%of the land area of Iran is very highly and highly susceptible to future landslide events,respectively,with the highest susceptibility in Chaharmahal and Bakhtiari Province(33.8%).About 31%of cities of Iran are located in areas with high and very high landslide susceptibility.The results of the present study will be useful for the development of landslide hazard mitigation strategies.  相似文献   

Optimum structural design of full-scale steel buildings using drift-tribe-charged system search     

Talatahari  Siamak  Veladi  Hedayat  Azizi  Mahdi  Moutabi-Alavi  Ali  Rahnema  Salar 《地震工程与工程振动(英文版)》2022,21(3):825-842

Earthquake Engineering and Engineering Vibration - In this paper, the potential of utilizing improved metaheuristic approaches in optimal design of building structures is concerned. In this regard,...  相似文献   

Early Mesozoic sedimentary‒tectonic evolution of the Central-East Iranian Microcontinent: Evidence from a provenance study of the Nakhlak Group     

Seyyedeh Halimeh Hashemi Azizi  Payman Rezaee  Mahdi Jafarzadeh  Guido Meinhold  Seyyed Reza Moussavi Harami  Mehdi Masoodi 《Chemie der Erde / Geochemistry》2018,78(3):340-355

In Central Iran, the mixed siliciclastic?carbonate Nakhlak Group of Triassic age is commonly seen to have a Cimmerian affinity, although it shows considerable resemblances with the Triassic Aghdarband Group in far northeastern Iran, east of Kopeh-Dagh area, with Eurasian affinity. The Nakhlak Group is composed of the Alam (Late Olenekian?Anisian), Baqoroq (Late Anisian??Early Ladinian), and Ashin (Ladinian??Early Carnian) formations consisting mainly of volcanoclastic sandstone and shale and fossiliferous limestone. The Baqoroq Formation contains also metamorphic detritus. Sandstone petrofacies reflect the detrital evolution from active volcanism to growing orogen and again active volcanism. Textural and modal analyses of volcanic lithic fragments from the Alam Formation reflect the eruption style and magma composition of a felsic to intermediate syn-sedimentary arc activity. The detrital modes of the Baqoroq Formation sediments suggest a recycled orogenic source followed by arc activity in a remnant fore-arc basin. The sandstone samples from the Ashin Formation demonstrate a continuity of felsic to intermediate arc activity. Major and trace element concentrations of the Nakhlak Group clastic samples support sediment supply from first-cycle material and felsic magmatic arc input. The enrichment in LREE, the negative Eu anomalies, and the flat HREE patterns indicate origination from the old upper continental crust and young arc material. The chemical index of alteration (CIA ～51–70 for sandstone and 64–76 for shale samples) indicates medium degrees of chemical weathering at the source. Petrographical and geochemical evidence together with facies analysis constructed the following depositional conditions for the Nakhlak Group sediments: In the Olenekian, a fore-arc shallow to deep marine depositional basin developed that later was filled by recycled and arc-related detritus and changed into a continental basin in the Anisian. Ladinian extension let to a deepening of the basin. With respect to the similarities between the Nakhlak and Aghdarband (NE Iran) groups and unusual present-day position of the Nakhlak Group with no stratigraphic connection to the surrounding area, the development of first a fore-arc basin and later change into a back-arc depositional basin in close relation with the Aghdarband basin at the southern Eurasian active margin in the Triassic are here proposed. Understanding the basin development recorded in the Nakhlak Group provides constraints on the closure history of Palaeotethys and of the tectonic evolution of early Mesozoic basins at the southern Eurasian margin before the Cimmerian Orogeny.  相似文献   

Numerical Analysis of Pile–Soil–Pile Interaction in Pile Groups with Batter Piles     

Hasan Ghasemzadeh  Mohsen Tarzaban  Mohammad Mahdi Hajitaheriha 《Geotechnical and Geological Engineering》2018,36(4):2189-2215

Battered piles are usually used to counteract lateral forces in a pile group. As there is little spacing between piles, they are affected by one another, and there is interaction between them. In this study, pile–soil–pile interaction in a group of battered piles was numerically simulated using finite element analysis. Double and frictional pile groups under static lateral and axial loadings were analyzed separately. The effects of batter angle, slenderness ratio, spacing between piles, pile–soil stiffness ratio, and soil plasticity on interaction factors were computed and presented in curves.  相似文献   

The behaviour of an artificially cemented sandy gravel   总被引：1，自引：0，他引：1  

S.?Mohsen?HaeriEmail author  S.?Mahdi?Hosseini  David?G.?Toll  S.?Shahaboddin?Yasrebi 《Geotechnical and Geological Engineering》2005,23(5):537-560

The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore water pressure and a barrelling failure mode. However, cemented samples and uncemented samples tested at low confining pressure (25 and 50 kN/m²) showed dilative behaviour accompanied with negative excess pore water pressure. Shear zones were formed in these samples and a clear peak in excess pore water pressure and stress ratio against strain could be observed. Test results showed that the limiting stress ratio surface for cemented samples is curved and expands as the cementation and density increase. Unconfined compression strength of cemented samples increases with increases in cementation and density as well.  相似文献   

Surface sediment carbonate mineralogy and water column chemistry: Nicaragua Rise versus the Bahamas     

AndrW. Droxler  John W. Morse  Karen S. Glaser  Geoffrey A. Haddad  Paul A. Baker 《Marine Geology》1991,100(1-4):277-289

Periplatform surface sediments were studied for carbonate mineralogy in conjunction with analyses of the water column for carbonate chemistry on the eastern Northern Nicaragua Rise (NNR) in the Caribbean Sea. The results show a strong correspondence between variations and disappearance, with increasing water depth, of metastable carbonate minerals (fine aragonite and magnesian calcite) and their respective saturation levels in the overlying waters. Similar correspondence between variations in sediment proportions of fine aragonite and magnesian calcite and their respective saturation levels has previously been established in the Bahamas. There are, however, significant differences between the two areas. The sharp decrease in aragonite content and the measured aragonite saturation level occur at 4000 m in the Bahamas, compared to 1800 m on the eastern NNR. In both areas, magnesian calcite minima correspond to the in situ PCO₂ maxima in the water column. The magnesian calcite minimum, however, is at 950 m in the Bahamas and 750 m on the eastern NNR. Magnesian calcite disappears in the Bahamas at 3800 m and at 2000 m on the eastern NNR. These results demonstrate the importance of the influence of overlying water chemistry on the preservation of metastable carbonate minerals in off-bank periplatform sediments, and they clearly demonstrate the difference in terms of carbonate preservation between the poorly ventilated waters of the Caribbean Sea and the well-oxygenated waters of the adjacent Atlantic Ocean. They also open the possibility of obtaining paleoceanographic information on the depth of the CO₂ maximum (O₂ minimum) and its separation from the aragonite saturation depth in at least some areas.  相似文献