فهرست مطالب mohammad khanehbad

Uniaxial compressive strength is one of the most important properties of rocks, whose determination is important for rock engineering studies in civil engineering and mining. Determining the uniaxial compressive strength is time-consuming and expensive. In order to reduce the cost and time, you can use the empirical relationships obtained from easier methods. In this research, using the artificial neural network method, experimental relationships have been presented to estimate the uniaxial compressive strength of limestones of the Esfandiar formation in the north of Tabas city. In this method, the physical characteristics of the rock sample as independent variables are the input parameters that are used to calculate the uniaxial compressive strength as a dependent variable. These relationships consist of a general structure with 4 inputs and 1 output, which was performed using a perceptron multilayer neural network. In this research, the root mean square error (RMSE) was investigated. The results of this research show that the amount of error caused by testing, testing, and validation is close to zero and these relationships can be used to estimate the uniaxial compressive strength of limestones of the Esfandiar formation. Also, the results of the artificial neural network have been compared with the results of multivariate regression, and the results show that the value of the confidence coefficient obtained from the artificial neural network is more acceptable.

The Sibzar Formation (Middle Devonian) is located about 30 Km east of Neyshabur city and is composed of lower dolostone with intercalations of sandstone, middle basaltic sill, and upper dolostone to limy dolostone, with a thickness of 334 m. The sandstone intercalations of this formation have fine to sometimes medium-grained quartz, with low values of feldspar, and rock fragment. According to petrography studies, sandstones of the Sibzar Formation were mostly quartzarenite and subarkose, however some samples plotted on litharenite. From the perspective of geochemical studies, the most abundant major oxides in these sandstones are SiO2 and Al2O3 with an average concentration of 77.8 and 8.3 (wt%), respectively. According to the ratios of SiO2/Al2O3 and Na2O/K2O and other amounts of major oxides and trace elements, such as CaO, Fe2O3, TiO2, Zr, and V, these sandstones have medium to high values of quartz; therefore have a quartzose sedimentary provenance, and are located in an intracratonic basin on the passive continental margin. Source rocks of these sandstones are intermediate to felsic igneous rock and have been affected by moderate to extreme degrees of chemical weathering. According to the evidence, the source of siliciclastic sediments for Sibzar Formation sandstones may have been Arabian and African plates.

Sorkh Shale Formation in Rabat-e-Shur stratigraphic section, west of the Tabas Depression, has been biostratigraphically investigated in this research. The Sorkh Shale Formation, with 48 meters thickness in this section, consists of shale, marl, and marly limestones, which are underlain by the Permian Jamal Formation and are overlain by the Triassic Shotori Formation dolomites. Nine conodont species belonging to four genera, Ellisonia, Hadrodontina, Parachirognathus, and Pachycladina were identified for the first time from this formation. The mentioned conodont assemblage is divided into three biozones: Hadrodontina aequabilis, Hadrodontina anceps, and Pachycladina obliqua. These taxa are in good agreement with the previously reported euryhaline assemblages from the near-shore and shallow water Western Tethyan realms in the south and east of Europe in the Early Triassic (Late Griesbachian-Middle Smithian). These conodont biozones are used for a better understanding of the distribution and affinities of the Early Triassic conodonts in West Asia, their paleobiogeographical rank, their significant role in the Early Triassic chronostratigraphy and their importance in bio-correlation of different section worldwide. Examination of the conodont alteration index of the obtained taxa from the Sorkh Shale Formation demonstrates CAI=5 during the late Griesbachian, CAI=4 in the Smithian, and CAI=6-8 in the Dienerian substages which is placed in the barren Zone for hydrocarbon production.

The present study aims to investigate the petrographic, geochemical features, and depositional facies of the Late Triassic Ashin Formation (Nakhlak Group, central Iran). For this purpose, 100 thin sections, and 13 samples of fine-grained sedimentary rocks were analyzed for their petrographic and geochemical characteristics, taken from a 330-m thick section of this formation. The petrographic types identified in this formation include sandstone, siltstone and limestone. This study suggests limestone facies are deposited in upper parts of the distal submarine fan towards the shore, sandstone facies are deposited in the middle part of the distal submarine fan, and the shale facies are deposited in lower parts of the distal submarine fan towards the abyssal plain by turbidity currents. The plotting of petrographic data on ternary diagrams for compositional classification illustrate their composition as litharenites, sub-litharenites, and a few litharenite-feldspathic and shales. Discrete diagrams refer to a tectonic setting of a continental arc complex and the active continental margin. The results of the modal analysis and geochemical data indicate the orogenic re-cycling for these deposits. CIA and CIW indexes indicate moderate weathering of the source area under semi-arid to semi-humid climates.

The Kopet-Dagh sedimentary Basin that crops out from NE Iran to Turkmenistan was formed as an intracontinental Basin due to the southeastern extension of the South Caspian Basin by Neotethyan back-arc rifting after the closure of the Palaeotethys and the early Cimmerian Orogeny (middle Triassic). A thick sedimentary package (10 kilometers) consisting of five transgressive- regressive super-sequences from Jurassic to Miocene time is deposited in the Eastern part of the sedimentary basin that is mainly controlled by NW-SW running major faults. The Cretaceous sequence in the Kopet-Dagh Basin is divided into nine formations, mainly composed of sandstones, conglomerates, mudstones, limestones, and dolomites with minor amounts of evaporates (Afshar-Harb, 1979). The regional trend of the Kopet-Dagh sedimentary basin was northwest-southeast during the Cretaceous. After the deposition of thick, red siliciclastic sediments of the fluvial system during the Early Cretaceous, a suitable condition for the deposition of carbonate sediments (named as Tirgan Formation) was provided as a result of major marine transgression during the Barremian-Aptian stages. The Tirgan Formation is one of the most widespread Upper Cretaceous formations in the eastern Kopet-Dagh that unconformably overlies the fluvial sediments of the Shurijeh Formation and is overlain by a sharp contact of the Sarcheshmeh Formation.

This study is focused on two stratigraphic sections in the Eastern Kopet-Dagh in northern Iran. Ninety thin sections were examined to identify fine-scale physical characteristics (mineralogical composition and fossil contents). Lithology, grain size, and sedimentary structures were recorded.

Based on sedimentological features, sixteen facies are recognized that grouped within five facies associations consist of deep and shallow open marine (FA), shoal (FB), lagoon (FC), and Tidal flat (FD). Deep open marine facies include green-gray fissile (sandy-silty) shale and shallow open marine facies are mainly consist of bioclastic wackestone, ooid/peloid bioclastic floatstone, sandy intraclastic floatstone, sandy intraclastic bioclastic float-rudstone, and sandy peloid bioclastic grainstone. The main constituents in this association are brachiopods, bryozoans, echinoderms, oysters, orbitolinids, intraclasts, ooids, and peloids. Micrite envelopes and borings are the common features in this association. The skeletal elements display high fragmentation, preferentially horizontal orientation, and fining up-ward fabrics. Green-gray fissile shale is deposited in a low energy depositional setting below weather wave base (SWWB), periodically affected by storm waves, suggested by the presence of the siliciclastic grains. The skeletal elements of the shallow open marine facies offer a shallow full open marine setting between SWWB and fair-weather wave base (FWWB) (Bovar-Arnal et al., 2009). High fragmentation, preferentially horizontal orientation, and fining upward skeletal elements suggest the storm-generated shell concentrations. Low energy periods of the sedimentary environment (post- and pre-storm phase) are indicated by micrite envelopes and borings. Shoal association consists of ooid grainstone and sandy ooid grainstone facies with predominantly well-sorted fabric. The main sedimentary structures in this association are sigmoidal cross-beds, wave ripples, cross lamination, and planar cross-beds with the erosional surface. These sediments are deposited in medium-high energy shoal settings above FWWB in the inner ramp environment suggested by well sorting of the elements and predominantly grainstone facies (Bachmann & Hirsch, 2006; Brandano et al., 2012). The sedimentary structures clearly show that tidal currents controlled the association's deposition in a sandy shoal environment. Lagoon association includes sandy mudstone, bioclastic wack-packstone, sandy ooid wackestone, sandy peloid packstone, intraclast, ooid float-rudstone, ooid/peloid pack-grainstone, ooidal bioclastic float-rudstone with main ooids, peloids, benthic foraminifers, echinoderms, and minor content of green algae, bivalves, brachiopods as well as siliciclastic grains that are commonly floated in the micritic matrix. These sediments are mainly deposited in a semi-restricted to restricted (sandy mudstone) lagoon setting above FWWB. The periodical water circulation suggested by the mixture of the open marine (echinoderm, brachiopods) to more restricted and brackish water elements (ostracodes, benthic forams), floated within the micritic matrix (Colombie & Strasser, 2005; Bachmann & Hirsch, 2006; Bovar-Arnal et al., 2009). The tidal flat association mainly consists of peloids, benthic foraminifers, and ostracods surrounded by flat microbial laminations. The flat geometry of the microbial lamination and the presence of the peloids and benthic foraminifers as the main elements in this association demonstrate a flat substrate in a tidal flat setting of the most internal part of the carbonate platform.

In a general view, petrography and field observations, facies associations relationship, and vertical trend of the studied successions suggest Tirgan sediments in the Kopet-Dagh basin are deposited in shallow to the deep marine environment with tidal flat, lagoon, shoal, and shallow to deep marine facies zones. These sediments were deposited in a homoclinal ramp characterized by gradationally vertical changes in the facies associations and abundant storm deposits. This carbonate system was influenced by storm (shallow marine zone) and tidal (shoal zone) currents suggested by the storm-generated shell concentrations, wave ripples, cross laminations, and sigmoidal cross-beds.

After the Mid-Cimmerian tectonic event in the Central-East Iranian Micro-continent (CEIM), the marine sediments of the Parvadeh Formation were deposited in the Middle Jurassic, with a significant expansion in the north of the Tabas block and mainly formed from dark gray fossiliferous limestone (Aghanabati, 2014; Seyed-Emami et al., 2004). In this study, two sections of Parvadeh Formation in Ravar-Mazino sub-block (92 km west of Tabas) and Kalshaneh syncline in Kalmard block (83 km north of Tabas) have been selected for diagenesis and geochemistry studies. Diagenetic events are an important key in sequence stratigraphy studies, identifying surface exposure phases and changes in environmental conditions (Moore and Wade, 2013). Analysis of trace and major elements also leads to a better understanding of environmental conditions characteristics and better identification of fluid systems associated with diagenetic processes (Nader, 2017; Oliveira and Truckenbrodt, 2019). A combination of field, petrographic and geochemical data was used to investigate the effect of diagenesis on the studied deposits.

After completion of field studies, 113 rock samples were selected and studied by Cathodoluminescence (CL) and polarizing microscope after the thin sections were prepared, while Dickson (1966) method was used to detect calcite from dolomite. Also, 11 limestone samples were selected for geochemical analysis and then tested by Zarazma Mineral Studies Company using the ICP-OES Varian model to determine trace and major elements.

Petrographic studies indicate that the Parvadeh Formation has been affected by micritization, cementation (Isopachus, Granular, Drusy, Blocky, and Poikilotopic), neomorphism, replacement (dolomitization, silicification, and pyritization), physical and chemical compaction, iron oxide, and fracturing processes. Calcite was pink to red in staining with red alizarin, while dolomite was not stained. In addition, elemental analysis of samples from the Parvadeh Formation showed that the amount of Sr varied from 269 to 678 ppm, and the amount of Na varied from 604 to 1189 ppm. The changes ranged between 134 to 443 ppm for Mn, 1978 to 13183 ppm for Fe, 33.15 to 38.24% for Ca, and 2785 to 4639 ppm for Mg. Positive trend changes in the Fe/Mn, Fe/Na, the low Sr/Mn ratio in the studied samples, and its inverse linear relationship with Mn values showed the highest effects of meteoric diagenesis and, to some extent, burial diagenesis. Based on the Sr/Ca plot versus Mn, it is possible to figure out the open and closed diagenetic system, the ratio of water-to-rock interactions, and the oxidation and reduction conditions of the environment (Brand and Veizer, 1980).The bivariate plot of Sr/Ca versus Mn shows that fluids in an open diagenetic system have stabilized the limestone of the Parvadeh Formation. Modern and ancient tropical carbonates differ from their non-tropical counterparts by their Sr/Na ratio and Mn contents (Rao, 1991; Winefield et al., 1996). In the Parvadeh limestone, Sr/Na concentrations range from 1.44 to 0.3 (mean: 0.6), similar to carbonate samples and the subtropical-temperate climate of the recent regions. The plotting of Sr/Mn with Mn provides a valuable measure of the degree of dissolution in limestone (Rao, 1991). The average Sr/Mn ratio in the Parvadeh Formation carbonates is 1.61. The low Sr/Mn ratio in the studied samples and its inverse linear relationship with Mn values show the highest effects of meteoric diagenesis and, to some extent, burial diagenesis.

Micritization, cementation, neomorphism, physical and chemical compaction, dissolution, Viens filling and fracturing, dolomitization, silicification, and pyritization are the most important diagenetic processes of the Parvadeh Formation. These processes have been carried out in four marine, meteoric, burial, and uplift diagenetic environments, with meteoric and burial diagenesis having the most significant impact on the Parvadeh Formation, respectively. Micriticization processes, formation of microcrystalline dolomites, and some cement (overgrowth) have occurred in the stage of marine diagenesis. In contrast, dissolution, neomorphism, and appearance of some cement (Blocky, Granular, Drusy) have taken place in the stage of meteoric diagenesis. Also, physical compaction, stylolite, formation of some cement (Blocky and Drusy), and medium crystalline dolomites have occurred in the burial diagenesis stage, while the development of fractures and their filling has taken place in the uplift stage. The positive trend of changes in Fe versus Mn and Fe versus Na graphs indicates the effect of meteoric diagenesis. The low Sr/Mn ratio in the studied samples and its inverse linear relationship with Mn values show an increase in burial depth and a decreasing trend of Sr/Na versus an increase in Mn, indicating a close combination of recent temperate carbonates, whose geochemistry results are consistent with subtropical to temperate climates obtained during the Middle Jurassic. Also, changes (1000 * Sr/Ca (wt)) versus Mn indicate the open diagenetic system in the Parvadeh Formation.

Asmari carbonate formation in Qale Nar oil field is one of the most important oil reservoirs in Dezful embayment. This reservoir has a lot of heterogeneity due to intensive changes in the sedimentary environment and diagenetic processes, which makes it very difficult to predict the petrophysical properties of the rock in reservoir. Creating a logical connection between sedimentary and electrical facieses, it can be effective in better understanding the reservoir and reducing uncertainties. In this study, using petrographic data and core description in six wells, 7 limy facies associations and one coarse crystalline dolomite were identified. Based on the petrophysical well logs of gamma, neutron, density, acoustic and photoelectric, and using Geolog software by MRGC algorithm, 5 electrofacieses (from 1 to 5) of the reservoir were determined. Electrofacies 1 has the best and electrofacies 5 has the worst reservoir quality. Examination of the frequency of electrofacies shows that good and very good electrofacieses make 30% of the Asmari reservoir of Qale Nar oilfield.

In this study, the pollution of the Revenj River sediments with heavy elements has been studied. Revenj River catchment with an area of ​​131 Km2 is located 20 kilometers from the city of Torbat-e-Jam (northeast of Iran). To investigate the contamination of sediments with heavy elements, 15 samples of sediments were taken from the area and analyzed by ICP-MS. In order to monitor the contamination of Revenj River sediments with heavy elements, Enrichment Factor and Contamination Factor were used. Chromium with low eenrichment and iron and nickel with no enrichment have similar geochemical behavior and originate from weathering and erosion of ultramafic rock units and have caused low pollution. Arsenic and lead are low pollution and copper is moderately pollution in the area. Shemshak Formation has led to a focus on arsenic and lead pollution at the beginning of the Revenj River catchment. The passage of tributaries over the granite units and the confluence of these tributaries at the end of the catchment with the Revenj River has led to relatively severe enrichment and contamination of copper and lead in the sediments at the end of this catchment. The pollution load index shows the concentration of pollution at the beginning and end of the catchment area, which is in line with the previous indicators.

Soil Erosion and Sediment Yield is one of the main environmental problems in watersheds of Iran. The purpose of this study is using MPSIAC model and application of GIS to minimize the probable errors in soil erosion evaluation and sediment yield in Eshghabad-Sule watershed. This area is located in the southwest of Quchan, and it has 81.365 km2 area and elongate form. This basin is located in Binaloud structural zone, and it has relatively thick sequence of volcanic and sedimentary rocks. Data layers of MPSIAC model are comprised of nine effective factors in erosion and sediment yield in the watershed that were obtained by digitalizing and classifying the basic information data in GIS program. The final erosion map was obtained from all information layers. The results of MPSIAC model indicated that 46.79% (3807.1751hec) was classified at IV class with high sedimentation and 53.2% (4329.3249 hec) was classified at class III of erosion category with medium sedimentation. Mean sediment yield was calculated as 5.04 and 2.844 ton/hec by MPSIAC model, respectively. The comparison of mean sediment in this watershed with mean data from the nearest hydrometery station is get acceptable results.

Parvadeh Formation (Bathonian) in Tabas block is formed of mixed siliciclastic-carbonate deposits. Six stratigraphic sections have been selected in this formation which dominantly composed of conglomerate, sandstone, shale and limestone. Integration of field and microscopic studies resulted in identifying two facies association including 4 siliciclastic and 10 carbonate facies in this formation. Analyzing facies and sea level fluctuations caused identification of two 3rd order sedimentary sequences in each of the sections. The low-stand system tracts of the recorded sequences are characterized by tidal flat and lagoon facies and shallowing-upward para-sequences. Highstand and transgressive systems tracts are generally both represented by dominantly intertidal and sub-tidal lagoon, shoal and open marine facies. The upper and lower boundaries in all stratigraphic sections of middle Jurassic successions are SB1 that are distinguished by erosional evidences and sometime red conglomerate and sandstone horizons. On the basis of detailed facies and depositional sequences analysis, global sea level fluctuations and tectonic events are the most important factors that affected system tracts and depositional sequences in the Tabas block. Local tectonic activities (mostly related to Kalmard and Nayband Faults) also have an effective role on the thicknesses of siliciclastic and carbonate deposits in different parts of study areas.

Nebkhas are one of the aeolian dunes that play an important role in wind erosion by stabilizing sediments around plants. Due to the depression of northern Shahdad plain (eastern Kerman), the sever wind impact, high rate of sediment supply and the presence of desert plants, nebkhas have expanded. In this study in order to achieve the formation of nebkha in the Shahdad plain, sedimentological parameters and the effect of vegetation on nebkha geomorphology have been investigated. Due to the expansion of the study area and the different geomorphology of the nebkha, 30 nebkha were sampled along with sediments between them. the analysis of these sediments shows that nebkha sediments are often fine sand sizes that are well-sorted and rounded. However, sediments between nebkha often have a range between gravel (pebble) and fine silt which are subdivided into either surface and sub-surface sediments (depth greater than 2 centimeters). Surface sediments are often coarse grains (granule to coarse sand) and have relatively well roundness and sorting. Field investigations and analyses have shown that genus and plant species are important in the geomorphology of nebkhas in the Shahdad plain but the effect of vegetation on the sedimentary parameters is insignificant. This is due to the fact that the three types of vegetation identified (Tamarix stricta, Seditzia rosmarinus, Prosopis farcta), the highest levels of nebkha is for Tamarix stricta but the sedimentary parameters with different vegetation are not significantly different.

Upper Cretaceous period can be considered as the peak of diapirism movements in Zagros sedimentary basin (Bosak et al, 1998). After sedimentation of Hormoz salt series, these salts were rising up towards the surface during the Lower Paleozoic (Jahani et al, 2009).  In this study, Cenomanian-Santonian strata in Fars area that consist of Bangestan group (NE-SW trend), have been studied based on effect of local and regional diapirism on these strata.

One hundred and sixty samples from two stratigraphic sections (upper part of Kajdumi Formation, Sarvak Formation and lower part of Gurpi Formation) in Darmadan anticline (Near salt dome and far from it) have been studied. All samples shave been stained with alizarin red-s to enhance differentiation of calcite from dolomite (Dickson, 1966). In petrographic studies, skeletal and non-skeletal allochem percentages have been accounted based on Tucker (1991) and Flugel (2010). Identification of microfacies based on Embry and Clovan (1971) and clastisity index based on Carrozi (1989) have been carried out.

Eight microfacies related to the open marine, shoal, lagoon and tidal flat sedimentary environment areas have been identified:Open marine facies:MF1- Pelagic Foraminifera Glauconitic Wackestone/Packstone MF2- Bioclast Wackestone. MF3- Fine grained Bioclast Packstone MF4- Intraclast Wackestone MF5- Echinoderm and Rudist debris Packstone to Rudstone Shoal microfacies:MF6- Rudist Grainstone Lagoon microfacies:MF7- Orbitolinids Wackestone/Packstone Tidal flat microfacies:MF8- Sandy Mudstone Sedimentary environment Based on lateral and vertical facies changes, marginal carbonate shelf can be proposed as the sedimentary environment for these strata. In this case, sedimentation has happened in deep, outer shelf, middle shelf and inner shelf areas. Moving towards salt dome, facies change to shoal, lagoon and intertidal shallow facies. This can be due to diapirism movements in the area. Due to upward salt dome movement, some evaporitic clasts have been transported to the sedimentary environment (Giles and Lawton, 2002); this can be observed more in near salt dome sections. Diagenetic process in two sections In areas far from salt dome section, there are some diagenetic processes such as: micritization, cementation (equant), bioturbation and, glaconitization processes, but close to salt dome sections, we can see more diagenetic processes such as: cementation (syntaxial), physical and chemical compactions (stylolite), silicification, dolomitization and hematitization. This fact shows that there are more diagenetic processes in near salt dome sections which can be related to the diapirism movement in this area.

Based on petrographic studies, eight microfacies related to the carbonate shelf (from open marine to tidal flat) have been identified. Dolomitization, silicification and cementation (anhydrite and dolomite) processes had happened because of supersaturated fluids (high mg) in this area. Some diagenetic processes such as hematitization and physical and chemical compaction have increased once moving towards the salt dome. Comparing two sections to each other based on petrography, microfacies, diagenesis, energy index allochems, siliciclastic particles, gypsum and anhydrite cements, dolomite, etc. show us that diapirism had happened as a syn-sedimentation and post-sedimentation process.

The Kangan Formation (Early Triassic) is one of the most important gas reservoirs in the Zagros fold-thrust belt. The study area is located in the west of Hormozgan Province and on the Gavbandi highland. This field is one of the important gas production anticlines in the SW Iran. To investigate the reservoir quality of the Kangan Formation in these wells, 163 microscopic thin sections were prepared from 97.68 m core for petrographic investigations. Then, petrophysical study was out carried using wireline well logs such as spectral gamma ray (SGR), sonic (DT), density (RHOB), and effective porosity (PHIE). The petrographic studies led to the identification of facies features and diagenetic processes affecting the quality of reservoir in the studied wells. These diagenetic processes include chemical and physical compaction, various cementation (especially anhydrite cement), fracturing, dissolution as well as different types of porosity resulting from these processes. Also, for the purpose of accurate evaluation, petrography studies with wells, matching and reservoir characteristics of these wells were qualitatively and quantitatively interpreted and reservoir potential horizons were determined. In general, for the first well (well "A") four and for the second well (well "B") three reservoir horizons were investigated.

The Kangan Formation (Early Triassic) is one of the most important source rocks in the gas fields of the southern Zagros and the northern Persian Gulf. The studied gas field is located in the west of Hormozgan province and is one of the most important gas fields in Iran and the world. In order to evaluate the depositional environment and sedimentary sequences of this formation in the wells, microscopic studies as well as analysis of petrophysical charts, especially gamma-ray log, have been studied which this resulted in the identification of seven microfacies, of which these facies were deposited in four depositional subenvironments as tidal flat, lagoon, mainly shoal and open marine, and two third-order sedimentary sequences with a second-order sequence boundary (correlative conformity), each of which consists of a system tract of TST (often consisting of tidal flat and lagoon facies) and HST (often containing shoal facies) was formed. This study was also carried out with the aim of investigating the quality and expansion of reservoir zones and its relation with sedimentary sequence and depositional environments. In previous studies, the Kangan Formation has been classified into four general zones in terms of petrologic characteristics, but in this research with relying on available digital files from well studies and extending this information in the software space, and finally combining the interpretive information of the existing output charts, including gamma-ray logs, sonic log, density log, effective porosity log, and stratigraphic column with thin sections and sedimentary sequences, Kangan Formation in the well of the field was divided into three general zones in terms of reservoir.

The Asmari Formation is the main reservoir rock for the Aghajari oilfieild. It is composed of about 400-meter limestone, dolostone and interlayers of sandstones. Study of 1200 meters drilling cores, 2800 microscopic thin sections, 12 SEM analyses along with 125 routine core tests in 5 cored wells indicate that the Asmari Formation was effected by various diagenetic processes such as micritization, compaction, cementation, fracturing, dissolution and dolomitization. Some of these processes (e.g. dissolution, dolomitization and fracturing) have constructive effects on the reservoir quality and created wide variety of porosity types including vuggy, intercrystaline and channel in upper parts of the Asmari Formation. Destructive diagenetic processes (micritization, compaction and cementation) have destroyed pore spaces and make the lower parts of the Asmari (specially zone 5) to a non-reservoir unit. Porosity-permeability plots on the Lucia's diagram show sandstones and carbonates rocks with interparticle porosities have good reservoir qualities and always plot on upper parts of classes 1-3. Samples with fracture porosity mainly plot on upper part of class 1. This shows fractures has no considerable role in promoting the porosity, but they strongly increase permeability. Dolostones and the rocks with vuggy porosity have plotted on classes 2 and 3 (high porosity, relatively high permeability). Paragenetic secession of the Asmari Formation shows the diagenetic processes occurred syn-sedimentary on sea floor, after sedimentation during the low-deep burry and uplift. The results of this study can be useful in detection of reservoir zones, increasing of hydrocarbon production and enhanced recovery of this oilfield.

The Sibzar Formation (Middle Devonian) is located about 30 km east of Neyshabur and is composed of lower dolostone with intercalations of sandstone, middle basaltic sill and upper dolostone to limy dolostone, with a thickness of 334 m. Based on the crystal size in this formation, three different types of dolomite (D1, D2, Vd) were identified and according to the textural classification of the dolomite, most of the dolomite are nonplanar-a (xenotopic mosaic), planar-s (hypidiotopic mosaic) and planar-e (idiotopic mosaic), respectively. The dolomite of Sibzar Formation have an average of 21.36% Ca, 10.9% Mg, in terms of the concentration of the major elements. The high concentrations of Fe (average 1835.48 ppm) and Mn (average 1824.62 ppm) indicate the reduction conditions during deep burial. The concentration of Na (average 1108 67/1 ppm) indicates the entry of hypersaline fluids into the environment. The average concentration of strontium is 455.41 ppm. The source of magnesium ions is Mg-rich sea waters, connate sea waters and migration of hydrothermal fluids. According to petrographic and geochemical evidence, D1-type dolomite have been formed in tidal environment, D2-type dolomites due to the aggrading neomorphism of D1-type dolomite and Vd-type dolomites are formed during diagenetic processes.

espotic rule is one of the governmental forms accoss the world. It goes back to the dawn of man’s political life. In terms of structure, technique of political administration and nature, despotism comprises of a government on top of which there is an authoritative and autocrat person with totalitarian power where no rule and law and tradition and norm may restrict and bar his/ her behavior. Despotic rule is assumed to be different from dictatorship. Dictatorship is the ruling by high class or limited governing group that requires their political power and behavior to observe a series of certain rules and prevalent norms in the community. This makes it different from despotism. For centuries, structure of governments in the Persian Gulf region has been mainly influenced by geographic environment and factors that generally acted as platform to form a rulling system. The present essay has been conducted by descriptive-analytic method in order to identify effective factors in he formation of despotic governments in the Persian Gulf Region.The results of study show that some factors including geographic situation, water and farming status, rentier governing bodies, security pacts, religious system, tribal and ethnic system are led to the formation, composition, development, and persistence of despotic governments in this region.

The Asmari Formation, in the Aghajari Oilfield (located in the Dezful Embayment) with about 400-meter thickness, was deposited in a homoclinal carbonate ramp and affected by various diagenetic processes. Core studies, microscopic thin sections and Scanning Electron Microscope images (SEM) from the 5 wells indicate that dolomitization is one of the most effective diagenetic processes of the reservoir quality of the Asmari Formation, and dolomitization mainly affects the upper parts of this Formation. In addition, five types of dolomites including (1) Dolomicrite (62 micron), (4) floated dolomites in the fine grain matrix, and (5) dolomite cements are recognizable. Each type of these dolomites have different effects on the trend of mercury injection curves (Pc), and therefore on the reservoir quality of the Asmari. Moreover, dolomicrospars are the most common type and have high porosity and permeability (average 16% and 35 mD respectively) due to the presence of intercrystaline porosities. Therefore, they can be saturated by mercury under low entry pressures (about 5 psi), and then show high-steep capillary pressure curves. Dolomicrites due to fine-grain nature have initially high porosity and relatively low permeability (11.5% and 4 mD respectively). But in along with dissolution, they show reservoir characteristics similar to Dolomicrospars, and their Pc curves shift to the left. Floated dolomites in matrix have no considerable role in the reservoir quality. Moreover, dolospars due to over-dolomitization and locking dolomite crystals, and dolomite cements due to disconnecting pore spaces led to decreasing in porosity and permeability. It seems zones 1 to 3 of the Asmari Formation in the Aghajari Oilfield have more potential for drilling and well-completion in the future because of more concentration of dolomicrospars and vuggy dolomicrites.

The present study focuses on facies analysis and the reservoir characteristics of the Asmari Formation in the Aghajari oilfield (located in the Zagros fold-thrust belt, southwest Iran), and how they are linked to depositional environments and reservoir characteristics. This formation consists of about 380 m carbonates with some siliciclastic intercalations. Based on the integration of 1200 m of core description and petrographic analyses of 2500 thin sections, 9 carbonate and 1 evaporite microfacies along with 2 siliciclastic petrofacies were identified. Facies analysis shows that the Asmari Formation sediments were deposited in a homoclinal carbonate ramp within open marine (facies association A), shoal (facies association B), restricted lagoon (facies association C), tidal flat (facies association D), and beach (petrofacies E) environments. Macroscopic and microscopic studies reveal that the main porosity types include interparticle, growth framework, vuggy, intercrystaline, moldic and fracture. Based on Routine core analysis (RCA), porosity of the studied reservoir varies from 0.001 to 25.8%, with an average of 12.5%. The permeability ranges from zero to 1514 mD with an average of 94.27 mD. There is a good relationship between trend of mercury injection capillary pressures (MICP) and depositional environment. Therefore, facies deposited

Travertine deposits are a kind of continental carbonates that form in specific chemical, physical and biological conditions. Garab travertines in southeast of Mashhad are studied based on field, geochemistry (elemental and stable isotope analysis) and hydro-geochemistry analysis. Field and petrographic characterization led to recognize of crystalline crust, raft, foam, shrub, laminated, black mud and tufa lithofacies. These lithofacies are composed of calcite and aragonite mineralogy. They have high concentrations of Ca, Mg, S, Fe, Na and Sr and low concentration of Mn, P and Si. These lithofacies are enriched with respect to δ13C and depleted with respect to δ18O that can be related to algal origin and meteoric water, respectively. The type of Garab springs water is Ca- HCO3- - SO42- and Na- Cl. This water is saturated with respect to bicarbonate and sulfate. The water composition and dissolved ions have a close relation to geological units (carbonate and evaporite) in Garab area.

Qadir Member of Nayband Formation in the eastern part of central Iran have a wide outcrop. Investigating the lithofacies and sedimentary environment of Qadir Member of Nayband Formation (Upper Triassic) in east central Iran, Tabas Block, resulted in identifying the coastal plain, deltaic and open marine deposits. Based onfield evidences, the facies features and the geometry of beds, this member consists of two lithofacies include carbonate and siliciclastic facies. The siliciclastic facies were identified as having four sandstone facies (medium-grained), including Sr, Sh, Sp, St and three fine-grained lithofacies, including FI, Fm, Fl (Sr) / Sr (FI) and one coal facies (C). Also carbonate facies are calcirudite and calcarenite. Regarding the field, laboratory studies and identifying the lithofacies, the coastal plain, deltaic (including deltaic plain, proximal delta front, distal delta front, and prodelta) and open marine environments were identified for Qadir Member on which it is under the impact of tidal currents.

Tufa is the non- marine carbonates that formed from cold to low temperature freshwater at low depth and low energy flow conditions. Abgarm’s tufa is a typical kind of these deposits. Field and microscopic studies led to recognize of seven allochthonous and autochthonous lithofacies. The presence of dense plant covering river margins, increasing use of dissolve CO2 in water and providing chemical conditions due to turbulence are factors that are important in the formation of tufa. Based on concentrations of dissolved ions, the type of Abgarm water is Ca- Mg- HCO3. Based on ions ratio, the water with primary meteoric origin is affected by passing through dolomitic limestone and evaporite of the Mozduran and Shurijeh formations. The high concentrations of these ions caused the carbonate to be trapped between algae filamentous and formed a kind of active tufa. The presence of gastropod species show a dominance wet climatic conditions when these deposits formed. At the next step, decreasing rainfall and increasing temperature and evaporation, caused the death of two gastropods species (Melanopsis praemorsa and Galba truncatula) in the studied area. Isotopic analysis of oxygen and carbon show the effects of meteoric waters and Mozduran aquifer limestone formation in isotopic compositions of tufa in Abgarm area.

The Aitamir Formation (Albian- Cenomanian) consists of sandstone, shale, siltstone and several limestone beds. Artenj and Ghorghoreh sections have studied in east of basin for determination of the ichnofacies. In this research, trace fossils types and ichnofacies are recognized and their relation with depositional environment has interpreted. Trace fossils in studied sections consist of Arenicolitesisp., Cylinderichnous concentricus, Ophiomorpha isp., Palaeophycus heberti, Paleophycus tubularis and Thalassinoidesisp. that can be placed in glossifunjites and Cruziana ichnofacies. Glossifunjites ichnofacies with low diversity of trace fossils and oblique to vertical orientation of the Y branched Thalassinoides, Paleophycus and Arenicolites in trough and planar cross-bedded were formed in high-energy barrier complex. Whereas Cruziana ichnofacies with higher diversity and mainly oblique to horizontal trace fossils in sandy substrate with low to moderate sorting are formed in low energy condition in shoreface environment.

In order to understand the impact of salt plug on facies, depositional environment and diagenesis of the Sarvak Formation in the Kourdeh Anticline, three sections close to the salt plug measured and studied. The thickness of Sarvak Formation in three sections are 25 (close the salt plug), 90 and 185m (away from the salt plug) and is composed of limestone. Based on facies analysis and petrography, 11 microfacies identified. Microfacies analysis, high dip of sediments, differences in thickness, reducing of interbedded shale and shallowing environment toward the salt plug show that the Sarvak Formation deposited in three facies belts including outer, middle and inter shelf. Approaching to the salt plug, facies are shallower so that tidal flat facies have been in the margin of salt plug and deeper facies formed away from the salt plug. Digenetic processes affected this formation include micritization, neomorphism, dissolution, compaction, fracture, replacement (silicification, dolomitization, hematitization and pyritization) and cementation (equant, darusy, blocky, overgrowth and isopachous). The salt plug caused changes such as fracture and dolomitization of the bioclasts, reduction of dissolution, increases compaction and silicification that are operated in three Eogenetic, mesogenesis and telogenetic stages

Introduction The siliciclastic sediments of Kashafrud Formation (Bajocian–Bathonian) in the Kopet-Dagh Basin (Madani, 1977; Afshar-Harb, 1979) are composed of conglomerate, sandstone and shale. It is reported that these sediments were mostly deposited in deep water environment in the eastern Kopet-Dagh basin (Poursoltani et al., 2007; Taheri et al 2009; Poursoltani and Gibling, 2011). The study area is located in west of Bojnurd in the western parts of the basin with a thickness of about 749 m and consists of three units. It covers unconformably the limestone of Triassic Elika Formation and overlaid by carbonate sediments of Chamanbid Formation. The purpose of this research is to interpret depositional environment and sequence stratigraphic analysis of the Kashafrud Formation in order to understand the paleogeography of Middle Jurassic time.
Methods This research is based on field observations of one measured stratigraphic section in Navia area and petrographic studies of 69 samples. Lithofacies are classified, using Miall codes (2000, 2006) and thin sections are used for determination of composition and texture of coarse grain rocks. 10 shale samples have also washed for micro- paleontological study and three samples, including shale and sandstone, have studied with SEM and EDX by LEO-1450 V model in Central Laboratory of Ferdowsi University of Mashhad. We also measured 44 directional structures azimuths for paleocurrent analysis.
Results Based on field studies, three lithofacies are recognized in the study area as follow.
Conglomerate lithofacies are observed in the basal part of the studied section with 7 m thickness and is composed of Gcm, Gt and Gmm lithofacies. They are mostly grain-supported with graded bedded, poorly sorted with rounded pebbles, low sandy matrix and trough cross-beds (Gt). Gmm is identified by increases in sandy matrix, moderate sorting and quartz pebbles content.
Sandstone lithofacies consist of St, Sp, Sm, Se, Sl, Sr, Sh, Sm and St lithofacies. St is the most abundance sandstone lithofacies in unit 1. In this lithofacies grain size decreases upward and changes to thin-bedded and fine grain sandstones. Sp with planar cross bedding has Ophiomorpha trace fossil in unit 2. It has low angle and planar cross bedding that vertically changes to Sr lithofacies. Sr (Rippled lamination and layered sandstone) is present in both units 1 and 2 but it has Palaeophycus and Thalassinoides trace fossils in second unit. Sh lithofacies is recognized by parallel or horizontal bedding and lamination. This lithofacies is less abundant in unit 1 and interbeded with mud rocks lithofacies, while in unit 2 it seen with Sl lithofacies. Sl (Low angle cross-bedded sandstone) and is the most abundant lithofacies in unit 2 and mostly fine grain and associated with Sh and Sr. Se (Erosional scours) is mostly observed at the base of sandstones and associated with Sp and Sm.
The Kashafrud sandstones are mostly sublitharenite and minor amounts of litharenite with mineralogically supermature and textural submature.
Mud rock lithofacies consist of laminated (Fl) and massive (Fm) fine grain rocks. The Fl lithofacies is mainly composed of silt-size grains with Palaeophycus, Planolites and Rhizocorallium trace fossils in unit 3.
Discussion Kashafrud Formation is interpreted to be deposited in fluvial and deltaic environments. Fluvial environmentis supported by fining upward cycles, abundance of sandstone, well-rounded grains, trough cross-bedded and Plant remnants in red shale. They have mostly sublitharenite composition. Calculated chemical weathering index indicated that the rocks at the source area have been highly affected by high weathering condition that can be related to warm and semi-humid climatic conditions (Sarbaz et al., 1395, in press). Paleocurrent analysis also revealed that the probable source of these sediments can be located in south of the Kopet-Dagh basin.
Deltaic sediments are composed of proximal and distal delta front as well as prodelta. Proximal deposits consist of several coarsening upward cycles including shale and fine to coarse grain sandstones with a thickness of about 7 m. Dominant sedimentary structures are horizontal and low angle cross-lamination, wavy ripple cross-lamination, massive beds, hummocky and trough cross-beds as well as plant fragments. These evidences show that sediments may have been affected by interaction of long-shore waves as well as storm events (e.g. Edwards et al., 2005; Hampson, 2010).
Distal delta front form the main parts of sediments including fine-grain black to olive green shale and siltstone with fine sandstones interbeds. Major lithofacies are Fl and Fm with Palaeophycus, Planolites and Rhizocorallium trace fossils. These intervals may have been deposited below wave base under low energy conditions (Einsele 2000; Alvan and Eynatten, 2014).
Prodelta sediments are mostly composed of clayey and silty shale. Based on vertical variations of these sediments to silty and fine to very fine grained sandstones of distal delta front, they may have been deposited in low energy and probably more reduction conditions (Hoir et al., 2002). The study of small foraminifera of deltaic shale led to identification of 14 different species of 12 genera. The community of these microfossils, which is reported for the first time, show that deposition may have taken place in the shallow water near shore environment within about 50m depth (e.g. Murray, 1991).
Sequence stratigraphy Kashafrud Formation in this section is composed of two depositional sequence (DS1 and DS2). The lower boundary of the first sequence (DS1), based on angular unconformity (above Triassic limestone of Elika Formation) and fluvial conglomerate deposits, is type I (SB1). The upper boundary of DS1 is SB2 and is located in proximal delta front deposits with no subaerial exposure evidences. The thickness of the first sequence is about 400 m and consists of LST, TST and HST. The LST is composed of continental sediments (137 m) that is covered by transgressive surface. This surface reveals by massive shale (50 m) of distal delta fronts and maximum flooding surface is located in the upper part of these deposits. HST (215 m) is composed of 12 shallowing and coarsening parasequences. DS2 with thickness of about 349 m is separated from DS1with sequence boundary type 2. This depositional sequence is only composed of TST with Fm and Fl lithofacies that transitionally changes to deeper water black shale that follows by marl and fine grain carbonate sediments of the Chaman-Bid Formation. Therefore, the maximum flooding surface is probably located within the Chaman-Bid Formation. Interpreted sea level fluctuation curve of the study area can be related to regional geological history and sometimes can be relatively correlated with global sea level curve (Haq et al, 1987)