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Determining the elastic modulus of rocks is one of the crucial parameters in civil and petroleum engineering. Asmari geological formation is widely outcropped in a significant part of the west and SW of Iran and NE of Iraq. Understanding the static elastic modulus of host rocks is crucial because of the design and construction of numerous geotechnical structures and the presence of large hydrocarbon reservoirs in this formation. To determine the elastic modulus of intact rocks, the uniaxial compressive strength test is typically used. However, in jointed rocks and deep areas, where obtaining samples may be challenging, costly, or even impossible, correlations between static–dynamic elastic modulus (Es − Ed) is more frequently employed. Although some scholars have proposed correlations between Es − Ed, they had determined dynamic modules based on the ultrasonic test. In the aforementioned test, intact samples are used and the effect of discontinuities would not be considered; hence, the results cannot be considered as rock mass representative. In this study, to consider field geotechnical conditions, the dynamic modules were determined based on the downhole seismic test (DS) in a tunnel in located the west of Iran. Then from the results of static elastic modulus, which were obtained from core samples, a linear correlation was proposed between Es − Ed. The root-mean-square error and variance accounted showed that the predicted static elastic modulus by the proposed correlation is more accurate to a large extent. In addition, unlike the ultrasonic-based Ed, the results showed that the DS-based Ed is less than Es. [ABSTRACT FROM AUTHOR]

Rapid urbanization and physical development have produced a significant quantity of construction and demolition waste in Bonab, a city in northwest Iran. In order to achieve a high level of accuracy and minimize subjective bias, catastrophe theory (CT) principles were combined in the geographic information system (GIS) environment for identifying suitable locations for safe disposal of the waste. Site selection process for construction waste landfill (CWLF) in Bonab city involved preparation and integration of 12 maps representing elevation, slope, geology, soil type, land use, vegetation, distance to population centers, valuable ecosystems, river, groundwater, and access to the main roadways with the CT to reduce uncertainty associated with subjective evaluations. Evaluation of relative importance of the variables showed that elevation, slope, distance to the city, vegetation cover, and distance to communication networks have greater importance in site selection for construction waste landfill. On the contrary, distance to the river, groundwater level, distance to villages, and valuable ecosystems have the least impact. Suitable areas were identified in parts of the north and west of the city. The identified sites have a gentle slope, low agricultural potential, good access to the communication networks, suitable distance to the city, and no limitations regarding the groundwater level, geological formations, and vegetation cover. [ABSTRACT FROM AUTHOR]

The Shotori mountain range is located along the northern terminus of the Nayband fault on the eastern and western domains of the Tabas and Lut blocks, respectively. This range with NNW-SSE trending and approximately 120 km long includes a series of thrust faults approaching the right-lateral strike-slip Nayband fault. Since the Shotori range has experienced various geological events since the Triassic, our investigations suggest that the basement of the Central Iranian subcontinent of the Shotori range contains the early Triassic deep sedimentary with normal faults which confirms Triassic tensional tectonic stress regime in the region. After the middle Triassic, the mountain range has experienced thrust and strike-slip regimes. Therefore, in this study, we reconstruct the stress regimes for different geological periods using fault-slip data. The inversion of fault-slip data reveals drastic temporal changes in the maximum stress regime (σ1) over the Triassic, Jurassic, Cretaceous, Paleogene, Neogen, and Quaternary. The reconstruction of the stress field based on the age and direction of fault movement reveals that the direction of the maximum horizontal stress axis (σ1) under a tensional stress regime was approximately N129° in the Early Triassic. This stress regime is the cause of thinning and subsidence of the Shotori sedimentary basin. During the middle Triassic, the σ1 direction was about N81° and the upper Triassic, the σ1 direction was almost N115°. The middle Triassic and upper Triassic stress states exhibited two distinct strike-slip and compressive stress regimes. This stress regime led to the uplift of the Shotori sedimentary basin. During the Jurassic, the direction of the maximum horizontal stress axis (σ1) was ∼NW-SE under a compressive stress regime. During the Triassic, the σ1 direction was ∼N-S. This stress regime led to the formation of the high topography of the Shotori Mountain Range. In the Late Cretaceous, the direction of the maximum horizontal stress axis (σ1) under the extensional stress regime was ∼NE-SW. This stress regime led to the uplift of the Paleogen Dacite in eastern Iran. During the Neogene, the σ1 direction was ∼N6o°. The Quaternary tectonic regime is strike-slip and the σ1 direction is ∼N50°, consistent with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis reveals four recognized stress in this area, which includes compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the crustal diversity of the tectonic regimes was responsible for the formation of various geological structures, such as folds, faults by different mechanisms, and the present-day configuration of the Shotori sedimentary basin. [ABSTRACT FROM AUTHOR]

This research assessed stress regimes and fields in eastern Iran using fault-slip data and the tectonic events associated with these changes. Our stress analysis of the brittle structures in the Shekarab Mountains revealed significant changes in stress regimes from the late Cretaceous to the Quaternary. Reconstructing stress fields using the age and sense of fault movements showed that during the late Cretaceous, the direction of the maximum horizontal stress axes (σ1) under a compressional stress regime was ~N290°. This stress regime led to the uplifting of ophiolites and peridotites in eastern Iran. During the Eocene, the σ1 direction was NE-SW. The late Eocene and Oligocene stress states showed two distinct transpression and transtension stress regimes. This transition from transpression to transtension in the eastern Shekarab Mountains was the consequence of regional variations in stress regimes. The Quaternary stress state indicates that the tectonic regime in the Quaternary is strike-slip and the σ1 direction is ~N046°, which coincides with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis revealed that four distinct stress regimes have been recognized in the area, including compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the diversity of the tectonic regimes was responsible for the formation of a variety of geological structures, including folds with different axes, faults with different mechanisms, and the current configuration of the Sistan suture zone. [ABSTRACT FROM AUTHOR]

Improper use of alluvial aquifers and declining water levels in these aquifers have led to significant attention to the search for other groundwater sources in karst areas and hard formations. Iran is one of the countries that has a very high percentage of karst in the world and the study and tracing of karst are very important in this country. In this research, eight effective factors in karstification are identified and categorized into two groups and the relevant information layers are prepared. The first group includes average annual rainfall, type of geological formations, the density of fractures, and density of the fracture site. The second group, which is of secondary importance, includes the average annual temperature, the density of canals, slope, and type of vegetation. After preparing the information layers, quantitative parameters based on fuzzy logic and qualitative parameters were standardized by the rasterization method. The importance and weight of each of the effective factors were determined from two methods viz. Analytic Hierarchy Process (AHP) and the Fuzzy Hierarchical Analysis Process (FAHP). After multiplying the standard maps with their respective weights, they were overlaid, and finally, karst potential maps were generated. Maps were generated from the two weighting methods based on the subsurface and surface hydrogeological-geomorphological diagrams. Karst features such as Karen, dissolution cavities, depressions, caves, dry valleys, reservoir rocks of springs and water exploitation wells, and Calcareous limbs were ascertained, which indicates that the results of the FAHP method are more consistent with the existing conditions in the region. The final map was divided into five classes in terms of the karst potential, viz. very high, high, medium, low, and no potential. [ABSTRACT FROM AUTHOR]

The gravity data in a vast square including different formations of the Zagros mountains and central Iran block are investigated for delineating and modeling the localized geological strata and structures in the upper crust. The measured gravity data are firstly corrected for drift and free-air effects. The digital terrain model (DTM) is obtained through SRTM TIFF pictures with 1-arc-second resolution accessible for the survey area and its surroundings. A new approach is applied for Bouguer slab and terrain corrections. The Bouguer slab and the terrain corrections are considered as the gravity effect of the mass between the reference and the ground surfaces. The gravity effect of this mass is computed by its parameterization through advanced meshing algorithms (octree and quadtree) and then subtracted from the observed gravity data to obtain Bouguer gravity anomalies. De-trending is carried out via the polynomial fitting method. Upward continuation and radial power spectrum methods are utilized to obtain rough estimates from the depth of the anomalies. The residual gravity anomalies are inverted through a well-known algorithm used in an open-source script in Python to obtain the subsurface density distribution. The inversion results are interpreted based on a geological point of view. The maximum depth of some regional anomalies provides valuable information about the unresolved maximum thickness of stratigraphic formations, especially the oldest strata (Precambrian and lower Paleozoic) that were exposed in some parts of the survey area and have a relatively higher density. [ABSTRACT FROM AUTHOR]

Mass movements in wavy topographic zones pose a constant danger to infrastructure, water management, plantation formation, and human life. A commonly used method in near-surface geophysical surveys is Electrical Resistivity Tomography (ERT) to define various strata levels and calculate the likely slip surface of landslides. We use a developed algorithm named ResIPy to be able to incorporate surface topography using triangular cells in finite element forward and inversion processes. Initially, a synthetic landslide case demonstrates that employing the triangular mesh results in more accurate identification of the geological formations than the rectangular mesh, which requires more CPU time. Then, field data from a prone landslide at approximately 20 km NW of the Tehran province, in Iran, was investigated using eight geoelectrical profiles spaced 20 m along the sliding surface accompanying one borehole. The sliding surface corresponds to a deep zone with low resistivity due to the presence of shale, and the sliding material is composed of gravelly soil, silt, and tuff. According to the field observations, the crown portion is vulnerable to sliding because there are transverse cracks in the uphill slope. [ABSTRACT FROM AUTHOR]

Severe droughts and vast anthropogenic activities have propelled groundwater resource contamination in Iran. An accurate investigation of groundwater vulnerability objectively reflects an area's potential for groundwater contamination and supplies a reference for contamination control and prevention. Therefore, the groundwater vulnerability of the Fasarood plain, south of Iran, was evaluated using the DRASTIC index (DI), Fuzzy-based DRASTIC index (FDI), Composite DRASTIC index (CDI), and Nitrate Vulnerability Index (NVI) methods. The input hydrogeological parameters were rated, weighted, and integrated via a geographical information system (GIS). The results of all models showed very low to moderate intrinsic and anthropogenic vulnerabilities to groundwater pollution. The zones with the most significant exposure may refer to geological formations and improper agriculture activity. The conclusions recommend that the area which was identified as having a higher groundwater pollution risk needs scientific land-use practise along with appropriate watershed management. The agriculturalists working in more vulnerable areas with high nitrate concentrations must begin practising an organic farming system and should replace chemical fertilisers with biofertilisers to reduce the groundwater contamination rate. Also, government departments should encourage reasonable control of groundwater pollution prohibition and withdraw based on changes in groundwater vulnerability in the area. [ABSTRACT FROM AUTHOR]

The populations of cave-dwelling bat species are encountering a remarkable decline all over the world. To plan effective conservation projects for bats and their cave roosts, collecting data on their distribution in a particular region is essential. Furthermore, developing an applicable index that incorporates both biotic and abiotic parameters relevant to caves is useful to prioritize caves for conservation management. Recently, there has been a growing interest in studying bat fauna of Iran. The Kurdistan province in west of the country is entirely mountainous, having a suitable geological substratum for formation of caves. Previously, five bat species were reported from Kurdistan. The current study has improved the data by doubling the number of cave-dwelling bat species of the province. A total number of 61 records of 10 species were documented. Overall, of 28 caves studied, 26 caves were used by bats. Each cave hosted one to six bat species. To prioritize Kurdistan caves for conservation programs, the Bat Cave Vulnerability Index (BCVI) was employed for 26 caves explored in this study. Four caves, including Karaftu, Kamtaran, Darvish Ouliya, and Kouna Sham-Sham, were highlighted due to their highest BCVI value. The other 22 caves received medium or low priority values. In the current study, we provided data on the bat fauna of Kurdistan caves, in addition to evaluate their conservation priorities by applying an assessing index for the first time in the country. [ABSTRACT FROM AUTHOR]

In the present study, 6 water and 16 sediment samples were collected from Hashilan Wetland (Kermanshah Province, Iran) to specify physio-chemical properties of water and sediment and to evaluate the water pollution load with reference to the water physicochemical parameters. According to the Piper diagram, Ca2+–Mg2+–HCO 3 − hydrochemical facies is dominant due to calcium carbonate dissolution in the geological formations of the study area. The wetland water had a natural to slightly alkaline pH. Although TDS and EC of the water samples fall under freshwater category, their values were higher downstream of the wetland as a result of stagnant water, low water depth, more evaporation, and impact of agricultural runoff. Based on the water quality index (WQI), all water samples were 'suitable' for irrigation purposes, while 50% of the samples were 'unsuitable' for drinking. Comprehensive Pollution Index (CPI), and Sodium Adsorption Ratio (SAR) also indicated suitability of the wetland water for irrigation. According to the Wilcox diagram, salinity is higher downstream of the wetland due to introduction of agricultural runoff. It can be concluded that the wetland water could be used for irrigational purposes, but regular monitoring is recommended to promote sustainable use of natural resources and conserve the vulnerable aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Drilling operations release considerable amounts of drilling fluids that contain pollutants such as heavy metals and hydrocarbons. By means of the ICP-OES device, the concentration of metals in the drilling mud deposited in the accumulation pools (around the drill rigs), the drilling mud used in the well (initial, input, and output mud), the soil around the drilling rig, and the control sample can be determined. Comparison of metal accumulation volume with current standards (upper crust and the region's soil) indicates that the initial drilling mud contains As, Cd, Mo, Cu, and Ag metals. Also, the outflow and associated cuttings are contaminated with Sb, showing a geological formation origin for this metal. In case of Pb, Ba, Cr, and Mn, the level of contamination is in a medium range wherein the source of the contamination is recycled mud and drilling rocks in the previous phases. Contamination of other metals is evaluated in the low range. Geo-accumulation index (Igeo), Enrichment Coefficient (EF), and Contamination Factor (CF) are used to determine the level of pollution. Results show that As, Pb, Ba, Mn, Mo, Cd, Co, Cu, and Zn have caused a lot of pollution in the area and their amounts should be controlled. [ABSTRACT FROM AUTHOR]

The Sarough watershed in NW Iran hosts a large amount of mineral occurrences and ore deposits which may be considered as the source of heavy metals in the region. The area has been studied previously; however, the methodology of this paper was less focused on previous studies. This study aimed to assess water quality, determine the spatial distribution pattern, and identify the sources of heavy metals in the main tributaries of Sarough watershed using pollution indexes, multivariate statistical methods, and processing data by geographic information system. Totally, 51 water samples were collected along the main rivers to determine the concentrations of heavy metals by ICP-MS. Regarding the drinking water, agriculture, and freshwater aquatic life guidelines, the rivers were assumed unsafe considering most of toxic elements' content, especially As. The mean values for heavy metal pollution indexes (HPI: 237.32) and metal indexes (MI: 25.37) indicated the intensive heavy metal pollution. The cluster analysis categorized the 51 sampling sites into four clusters with respect to pollution level. The results obtained from the Kruskal–Wallis and multiple comparison tests had the harmony with the results of CA in introducing the most impacted sampling sites and the parameters responsible for water quality degradation. The results of PCA showed the maximum similarity between As, Sb, Se, Fe, and Mn as well as base metals which was attributed to anthropogenic input from mining and mineral processing wastes. Association of Cr and Ni may suggest a lithology source (weathering of metamorphosed ultramafic outcrops). The maps prepared in the GIS system showed the spatial distribution pattern of toxic elements with maximum values nearby mining sites which decreases gradually toward downstream areas. Finally, the results showed that the Sarough River and its tributaries are influenced by high concentrations of heavy metals from the drainages of mining and ore processing sites and naturally occurring metal loadings as well as the geogenic sources such as weathering of geologic formations and hot springs. [ABSTRACT FROM AUTHOR]

Knowing the water retention properties of soil can help with predicting water infiltration into the soil, the potential for runoff generation and sediment yield, and ultimately, better management of natural areas. The purpose of this study was to investigate the characteristics of the soil water retention curve (SWRC) and its effects on infiltration rate and runoff generation. For this purpose, an arid area in eastern Iran for which rainfall and runoff data were available was selected. Two variables that are assumed to affect soil water retention and runoff generation were used in this study, namely geological formation and topographic wetness index (TWI). The geological formations layer for the study area was extracted from 1:100,000 geological maps, and TWI was derived from the combination of slope and the area of upstream basins. Initial infiltration rate, stable infiltration rate, and time to stable infiltration rate were determined using the double ring infiltration apparatus and were used to create the soil infiltration potential curve (SIPC). In addition, saturation soil water content, field capacity, permanent wilting point, plant available water, and area under the curve were determined using pressure plates, and were used to create SWRC. The results showed that the characteristics of SWRC, SIPC, and soil water conditions after rainfall are affected by geological formation and TWI. All characteristics of SWRC were higher in the shale formation than the sandstone formation, and areas with higher TWI had lower soil water retention. Also, soils in the sandstone formation had higher initial and stable infiltration rates and required a shorter time to reach stable infiltration rates. The results showed that conversion of the soil water curve from the soil water-suction mode to the suction-time mode allows for predicting post-rainfall soil water conditions. Finally, areas in the shale formation with maximum TWI had the highest water retention potential, lowest infiltration rates, and maximum runoff generation capacity. [ABSTRACT FROM AUTHOR]

The concentration of total dissolved mercury (HgT) in surface and groundwater resources in the coastal parts of Urmia aquifer (NW of Iran) was investigated to identify the possible sources and sinks of mercury and the geochemical mechanisms controlling its mobilization. The distribution of water samples on the Piper diagram demonstrates that most samples have the Ca-Mg-HCO3 facies. From 62 water samples collected in this area, one sample contained HgT concentrations exceeding the maximum contaminant level recommended by the WHO (6 μg/L). The principal component analysis (PCA) produced five principal components. The positive moderate correlation of HgT with EC, Cl, K, Mg, and Na indicated that the weathering of geological formations was one of the main sources of mercury in groundwater samples. Position of water samples in Eh-pH regions where microorganisms involved in mercury methylation and mineralization were potentially active demonstrated that the aquifer had undergone sulfate reduction and had reached the final stage of the terminal electron accepting process (TEAP) sequence in the methane production processes which are limited to only 37% of the water samples that have anaerobic conditions. Some Hg-bearing species are in nonequilibrium geochemical conditions. The supersaturation of water samples with magnetite and goethite indicated that these Fe-bearing minerals could act as the strong reducing agents for the reduction of Hg(II) to Hg(0). [ABSTRACT FROM AUTHOR]

Introduction: Rivers react to subsidence at their baseline by cutting and digging topographic features. The development of an upstream incision is often accompanied by a steep fracture called a river break (Loget & Van Den Driessche, 2009). The presence of river breaks in a geographical landscape is an indication of a steady-state in river systems. Therefore, the presence of knickpoints shows the system instability. The study of knickpoints can be used in the field of studies related to the evolution of valleys, identification of tectonic active areas and rock outcrops, river surface changes, erosion and sedimentation, and geomorphological changes in river systems. The basin studied in this study is located in the Qaleh Shahrokh-Chelgard area in the northeastern part of Chaharmahal and Bakhtiari province, Iran. The reason for selecting this basin is the extensive activities of the Zagros fault along the northwest-southeast and the existence of a hydrographic network affected by the trend of faults and the potential for knickpoints. Methodology: In this study, the locations of knickpoints were detected from the Radiometrically TerrainCorrected (RTC) model which is extracted from the active microwave sensor ALOS PALSAR with a spatial resolution of 12 meters (Logan et al., 2014) as input data to the MATLAB executive toolbox called Tec DEM. Tec DEM is an executable toolbox in MATLAB software and uses a Digital Elevation Model (DEM) as input for morphotectonics in the basin. Tec DEM tool can be used in a variety of fields in the analysis of surface anomalies, drainage network and surface dynamics of basins, production of base maps, incisions (local roughness), vertical dissection and drainage density of basins and sub-basins, determination of turning points or knickpoints, hypsometric analysis and slope and concavity index of canal profiles (Shahzad & Gloaguen, 2011). The determination of knickpoints according to the shape of the longitudinal profile of the river is done semi-automatically. In this study, these points in the study areas were investigated according to field observations. In this study, geological variables and geomorphic variables related to knickpoints were used to identify the knickpoints. Information layers including geology, distance from the fault, distance from the boundary of geological formations, surface roughness index, fractal dimension, base surfaces, local roughness, and the vertical dissection as predictor variables and the layers of knickpoints as the prediction variables were used for modeling. For geological and tectonic studies of the region, geological maps of 100,000 sheets of Chadegan and Fereydunshahr and 250,000 sheets of Shahrekord were used. A total of 8 raster layers were used to analyze and predict the possibility of the presence of a knickpoint in the study area. Since 8 layers have different units and are not suitable as direct input for logistic regression, the input parameters were normalized in the range of 0 to 1. Nominal layers, such as geological data, became sequential variables between 0 and 1. All of these layers were then resampled as a network format with a cell size of 195*195 m using the nearest neighbor method, to allow all layers to be combined. Then, a matrix of square cell structure was prepared for the study area. It consisted of a matrix of 273 rows and 273 columns representing a total of 39,650 cells. Of these, 74 cells were identified as knickpoint points. These areas were identified with code 1 (presence of knickpoint) and the rest of the cells that did not have knickpoints were recorded with code 0 (absence of knickpoint). Discussion: The probabilistic relationship of the presence of a knickpoint as one of the important results of the research was obtained by the logistic regression method. This relationship predicted the probability of the presence of knickpoints based on geological and geomorphic variables. The probability map of the knickpoints in the study area was obtained based on the statistical relationship. According to the results, there is a possibility of river knickpoints in the southwestern regions and parts of the northeastern Basin. The results of the probability ratio test to determine the statistical significance of each of the independent variables in the proposed model showed that the geology and the distance from the boundaries of the geological formations in the model were significant. The results of the Yuden index for the training dataset, validation, and test data were equal to 0.72, 0.76, and 0.66, respectively, which indicated the accurate information on the probability status of knickpoint points, especially for the test data of the model. The results of the Kappa agreement coefficient for training, validation, and test data were also equal to 0.62, 0.73, and 0.60, respectively, which indicated the agreement of both methods with the observed values of knickpoints. Conclusion: The results of this study showed that at the boundary of lithology, because of the presence of joints and cracks due to differences in the type of rocks, the probability of the presence of river break was more than other parts of the region. Although the presence of some relatively high slope knickpoints indicated active tectonics in that area, in the present study, the effect of the fault system or active tectonics in the formation of knickpoints was not statistically significant. Particularly, the reduction of local roughness index and baselines was associated with less tectonic activity, but in this study, the appearance of knickpoints has been associated with a decrease in these two factors. [ABSTRACT FROM AUTHOR]

Several studies have evaluated the impact of climate change on the alluvial aquifers; however, no research has been carried out on a small-scale aquifer without any human influences and pumping wells. The object of this study is to assess the response of such an aquifer to the climate change to observe if it can preserve its storage or not. Pali aquifer, southwest Iran, is solely discharged by Taraz-Harkesh stream and geological formations. On the other hand, it is recharged by precipitation and geological formations. The Taraz-Harkesh stream's discharge rates and the Pali aquifer's groundwater level were simulated by IHACRES and MODFLOW, respectively, in the base (1961–1990) and future (2021–2050) time periods under two Representative Concentration Pathways, i.e., RCP4.5 and RCP8.5. The outputs of IHACRES were regarded as the input of MODFLOW. The groundwater model was calibrated in the steady-state for the hydrological year 2007 and in the unsteady-state for the time period 2008–2014 with annual time steps. Further, the groundwater model was verified for the time period 2015–2018. The statistical criteria maintained the groundwater model's ability, consequently measuring the root mean square error to be 0.69, 0.85, and 1.18 m for the steady calibration, unsteady calibration and verification of the groundwater model, respectively. Results indicate that the stream's discharge rates would decrease in the future time period, especially under RCP8.5. Nevertheless, the groundwater level would not fluctuate considerably. Indeed, the groundwater resources, even a semi-arid, small-scaled aquifer, may be considered as the water supplying systems under the future climate change. [ABSTRACT FROM AUTHOR]

Seawater chemistry has been highly variable during Earth's history. Whereas variations in the ratio of organic relative to inorganic carbon burial in oceanic basins are considered to trigger positive shifts in global seawater δ13C values, those in δ18O are related to Earth's climate fluctuations. Positive shifts in the carbon isotope record known from Cambrian marine carbonates on a global scale have provided invaluable stratigraphic insights. Carbon and oxygen isotope data from Middle-Upper Cambrian shallow marine carbonates of the Mila Formation, eastern Alborz Ranges, Iran are presented herein. Accordingly, the Furongian SPICE (Steptoean Positive Carbon Isotope Excursion) event is documented from the Qol-Qol Member of the Mila Formation at two stratigraphic exposures where this prominent and globally recorded isotopic event is detected in micrites/skeletal limestone with a maximum δ13C value of +4‰ at both localities. The positive shift initiates at the base, reaches the climax in the middle, and then declines in upper part of the Qol-Qol Member. Therefore, the base of the latter denotes the base of Furongian Series/Paibian Stage in the Alborz Ranges. The event occurred in the Palaeadotes – Torifera and Prochuangia trilobite Zones but detailed biostratigraphic studies are yet to be undertaken. The occurrence of glauconite and abundant benthic fauna in some intervals within the rock unit can be interpreted as recurring slightly-reduced and oxygenated sea floor circumstances during deposition of the Qol-Qol Member of the Mila Formation. • Carbon and oxygen isotopes from Middle-Upper Cambrian of NE Iran investigated. • The Steptoean Positive Carbon Isotope Excursion (SPICE) event identified. • The base of Furongian Series/Paibian Stage in the eastern Alborz Ranges is defined. • SPICE event occurs in the Palaeadotes – Torifera and Prochuangia trilobite Zones. • Abundance of glauconite and benthic fauna imply oscillating oxic-slightly reduced environments. [ABSTRACT FROM AUTHOR]

In recent years, groundwater level in Arak plain aquifer, Iran, declines due to overabstraction and sustainable management of the aquifer is changed to a vital issue. Spatiotemporal variation groundwater quality associated with identifying hydrogeochemical characteristics is the goal of this research. In the current study, graphical methods results are compared to two distinct clustering methods, hierarchical cluster analysis (HCA), and fuzzy C-mean (FCM) to analyze the hydrogeochemical dataset. Groundwater quality of Arak aquifer is monitored over an 11-year period in two-year intervals ranging from 2004 to 2014 (i.e., 2004, 2006, 2008, 2010, 2012, and 2014) by sampling from 52 abstraction wells for each year. Graphical methods identified dominant hydrogeochemical processes in the study area. The resulting clusters were categorized into freshwater (HC1, FC1), brackish-saline water (HC2, FC2), and saline water (HC3, FC3). The analysis resulted in three clusters including recharge, transition or mixing, and discharge zones, designated as FC1 and HC1, FC2 and HC2, and FC3 and HC3; respectively. The comparison of groundwater facies in 2004 and 2014 showed that the mixing zone (classes FC2 and FC3 and classes HC2 and HC3) has expanded with time. Observation well monitoring in the area showed that groundwater quality decrease due to groundwater level declines, especially in the residential zone. In addition, the role of geological formations in groundwater quality was evident in the distribution of clusters. Comprehensive regulation and integrated groundwater management is essential to prevent further degradation of groundwater quality in the region. [ABSTRACT FROM AUTHOR]

Many arid regions in the world suffer from over-exploitation of local groundwater resources leading to the degradation of freshwater aquifer systems, drying of spring discharges, and other damage to land and infrastructure. The development of groundwater critical zone maps (GCZMs) using the best available data is one important method that can be used by decision makers to develop a justifiable regulatory framework that may ban future use of wells. The multi-influencing factor (MIF) and the analytical hierarchy process (AHP) methods were used to create GCZMs for the Kangavar sub-catchment basin (aquifer system) of western Iran. Seven mapped factors were used as input into the models that included spatial occurrence of geological formations, aquifer lithologies, aquifer thickness, aquifer recharge, annual groundwater discharge (including water use), water-well density, and groundwater quality (degradation). Weighting factors were placed on the input data based on expert opinions, and the created thematic maps were combined using the weighted sum tool within a GIS framework to create two separate GCZMs. It was found that both methods produced acceptable and similar results, but based on a receiver operating characteristic curve analysis of internal error the MIF model (0.82) was > 10% more accurate compared to the AHP model (0.72). Critical and subcritical classification areas within the basin covered areas of 94 and 77.7 km2 in the MIF and AHP maps, respectively. Banning of water-well construction in these areas is therefore technically justifiable and demonstrates the need to use two methods for development and verification of GCZMs with varying assumptions. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze the assemblage of trilobites in the Silurian sequences of Iran by exploring stratigraphic section of the Silurian Niur Formation (Asadli section). Based on comprehensive field studies and laboratory investigations three Trilobite genera were identified in the study area including Calymene blumenbachii, Gravicalymene convolva, Dalmanites brevigladiolus and Calymene sp. according to this trilobite assemblage a Rhuddanian to Telychian stages (Llandovery) is suggested for deposition of the study strata. The recognized trilobite fauna will be used as a base for future geological studies on the Silurian strata in Kopeh-Dagh Basin. This is the first report of trilobites from the Silurian (Llandovery) Niur Formation in Asadli section, north- east, Iran. [ABSTRACT FROM AUTHOR]

More than 120 exposed salt diapirs in southern Iran are connected to the adjacent aquifers and likely constitute the main sources of groundwater salinization in the region. Located in southern Iran, the Korsia salt diapir is surrounded by alluvial and karst groundwater aquifers. To investigate the impact of the salt body of Korsia on the groundwater quality of surrounding aquifers, electrical conductivity, total dissolved solids and dissolved calcium, magnesium, sodium, potassium, chloride, bromide, and sulfate concentrations were measured at 41 sampling points, including 32 exploitation wells, 7 springs and 2 surface water stations. Additionally, oxygen-18 and deuterium isotopes were analyzed at 7 sampling points to investigate the source of the salinity in the area. Our hydrogeological, hydrogeochemical, and isotopic evaluations show that the Korsia diapir deteriorates groundwater quality of the eastern karst and southern alluvial aquifers through infiltration of a spring's brine into limestone, and flow of the surface brine originated from the diapir, respectively. A karst aquifer west of the diapir is not influenced by the diapir brine because its hydraulic connectivity is interrupted by an impermeable geological formation. Construction of salt basins or diversion of brine is suggested to increase water quality of the surrounding aquifers. These procedures can be applied not only in the Korsia diapir, but also in tens of diapirs of southern Iran as remediation methods to improve water quality of their adjacent aquifers in this arid region. [ABSTRACT FROM AUTHOR]

This study investigates the impacts of different geological units on groundwater quality of an aquifer in southern Iran. The Kriging interpolation technique with a Gaussian semivariogram model was employed to prepare groundwater maps for different water quality constituents. In the next stage, two different models based on fuzzy analytic hierarchy process (AHP) and Dempster–Shafer theory (DST) were used to evaluate the overall water quality index based on the World Health Organization's drinking water standard in different parts of the aquifer. The DST model was able to generate water quality maps with 99.5%, 99%, and 95% confidence levels. The water quality maps were subsequently compared with the geology map of the area to determine the effects of different soil types on the water quality of the aquifer. Both methods showed poor water quality indices in the areas with an Asmari formation containing elevated levels of chloride and sodium ions. Comparison of water quality maps generated by the fuzzy-AHP and DST model revealed that the DST could more reliably handle the uncertainty in the water quality data, and thus was able to generate more accurate water quality maps. Increasing the confidence level in the DST model yielded water quality maps with a decreased overall water quality index. Results of this study could assist water management practices to generate water quality maps for their groundwater resources with confidence levels commensurate socio-economic importance of the region. [ABSTRACT FROM AUTHOR]

Early cretaceous sediments (Fahliyan and Gadvan Formations) in the Coastal Fars (namely Assaluyeh and Halegan), Zagros fold-thrust belt, SW Iran, were measured and sampled for micropaleontological investigations. In this research, Fahliyan Formation lies unconformably on the Hith/Surmeh formations and the Gadvan Formation overlies the Fahliyan Formation with conformable contact. The Gadvan Formation overlies by Dariyan Formation; this contact is sharp and conformable. The Fahliyan Formation in these stratigraphic sections can be divided into two informal members: Lower Fahliyan member and Upper Fahliyan member; and the Gadvan Formation was divided into three informal members: Lower Shale member, Khalij member and Lower Shale member. The Fahliyan Formation and Gadvan Formation in the Zagros include a diversified assemblage of benthic foraminifera and dasycladalean algae. In Assaluyeh and Halegan sections based on foraminifers, three biozones and one subzone are recognized that in ascending order are: (1) Pseudochrysalidina (Dukhania) zone (Berriasian), (2) Pseudocyclammina lituus zone (Valanginian–Hauterivian), (3) Orbitolina–Choffatella–Salpingoporella dinarica assemblage zone (Barremian), and (4) Montseciella arabica subzone (Barremian). [ABSTRACT FROM AUTHOR]

Palaeo-exposure surfaces are common geologic features in the Cretaceous sedimentary record of the Middle East. Two important disconformity surfaces have influenced the Cenomanian-Turonian intervals of the Sarvak Formation in the Abadan Plain. These surfaces had substantial controls on reservoir quality of their underlying succession. In this study obtained data from macroscopic core descriptions, microscopic petrography, geochemical analysis, spectral gamma ray log signatures, and clay minerals frequency in three hydrocarbon fields are combined and used for interpretations. Dissolution, cementation and recrystallization are the main diagenetic features related to the disconformity surfaces. Intensity and development of these diagenetic alterations are highly dependent on depositional facies characteristics of the underlying sequences. In mud-dominated facies, the main diagenetic process is recrystallization, while the grain-dominated facies were highly subjected by dissolution and cementation. Based on the geochemical analysis, there is an increase in Al 2 O 3 , SiO 2 , Fe 2 O 3 , Al, Fe, Mn, and Rb content beneath the disconformities. In contrast, the Sr concentration displays a decreasing trend towards the disconformities. On spectral gamma ray logs, depletion of the uranium and high values of CGR/SGR and TH/U ratios are attributed to the meteoric diagenesis. In addition, obtained data from SEM and XRD analysis indicate that the montmorillonite is the most abundant clay mineral in uppermost part of the Sarvak Formation. It shows the highest concentration at the disconformity surfaces which can be quoted to the impact of meteoric diagenesis and development of palaeo-soil horizons. These results are used for reconstruction of diagenetic sequence of the upper Sarvak Formation in subsurface sections of the Abadan Plain. [ABSTRACT FROM AUTHOR]

Tight limestones with high amounts of microporosity will be the main targets of future hydrocarbon exploration and production in Middle East. In this paper, microporosity evolution in two Iranian reservoirs, Dalan and Dariyan formations, is investigated. These two formations represent the main hydrocarbon reservoirs in most of the Iranian hydrocarbon fields. Aptian Dariyan Formation is mainly composed of mud-dominated samples deposited in a ramp environment. The upper part of Permian Dalan Formation has the same facies distribution while the lower part is composed mainly of grain-dominated samples. Mud-dominated facies of Dariyan Formation have high porosity with moderate to low permeability. Micrites are rounded with punctic to serrate contacts. In contrast, mud-dominated facies of Dalan Formation have low porosity and permeability. SEM studies revealed that micrite texture has a major effect on final reservoir properties of these two formations. MICP and SEM studies showed that in grain-dominated samples of Dalan Formation, both small and large pore size throats are present. Mud-dominated samples of this formation are composed of micrites with compact-anhedral shape and coalescent contacts. These results combined with diagenetic studies confirmed the role of meteoric dissolution in microporosity development in both formations. In humid conditions of the Aptian time, micrites have been dissolved and a large amounts of microporosity have been developed. In contrast, in dry conditions of Late Permian, the original fabric of the micrites preserved until the late stages of burial. Rounded micrites are present in Dalan Formation where meteoric dissolution had a major effect on porosity development in this formation. [ABSTRACT FROM AUTHOR]

The late Jurassic Qal'eh Dokhtar Formation lithologically comprises three parts, from bottom to top, a lower sandstone unit, middle shale unit and an upper carbonate unit, which extend in a N–S direction over a wide area to the east of the Shotori Range and west of the Lut Block (Central Iran). This succession was deposited on a mixed carbonate–siliciclastic ramp. Carbonate rocks of the Qal'eh Dokhtar Formation vary from undolomitized, to partly dolomitized, to completely dolomitized. Field observations from two measured sections (the type section, 955 m thick, and the Sorond section, 639 m thick), combined with detailed petrographic and geochemical analyses, revealed the diverse types of dolomite in this formation. Five types of replacement dolomite and one type of dolomite cement were distinguished. Replacement dolomites (RD) consist of: (1) fine crystalline planar‐s (RD1); (2) medium crystalline planar‐s (RD2); (3) medium crystalline planar‐e (RD3); (4) coarse crystalline planar‐s (RD4); and (5) coarse crystalline planar‐e (RD5). Coarse crystalline planar dolomite cements (DC) were observed in low abundance and filling dissolution voids and fractures. Variation in dolomite types is mainly related to early to late diagenetic processes leading to changes in composition of the dolomitizing fluids. Replacement dolomites are non‐stoichiometric (Ca43‐56–Mg34‐45) with Sr, Mn and Fe concentrations of 41–138 ppm, 168–919 ppm and 5000–21000 ppm, respectively. These dolomites are characterized by δ18O values ranging from 0.0 to –11.8 ‰ VPDB and δ13C values of +1.1 to +3.2 ‰ VPDB. These values are depleted in δ18O relative to the postulated values for late Jurassic dolomites precipitated in equilibrium with seawater, while δ13C values are within the range of Jurassic seawater dolomite values. Fluid inclusion data of RD4, RD5 and DC yield homogenization temperatures of 72 to 118 °C. Based on petrographic, fluid inclusion microthermometric data and geochemical results, the replacement dolomites in the Qal'eh Dokhtar Formation are interpreted to have formed in the subsurface at shallow to intermediate burial depths. These dolomites were then recrystallized at increased burial depths and temperatures. Seawater was the major source of Mg2+ for early diagenetic dolomite (DR1), while Mg2+ for late diagenetic dolomites was provided from diagenesis of clay minerals in shales and mechanical compaction of mudstone in the Qal'eh Dokhtar Formation. The dolomite cement is postdated by coarsely crystalline mosaic calcite cement indicating that diagenetic fluids eventually became undersaturated with respect to dolomite and oversaturated with respect to calcite. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study characterizes the opacifiers and colouring agents used in the glazed bricks of Persepolis (mid-first millennium bc) and the Mannean site of Tepe Rabat in north-western Iran (eighth to seventh centuries bc). Various analytical studies show that lead antimonate and brizziite (NaSbO3) were used as the yellow and white opacifiers in the glazes of Persepolis and Tepe Rabat. Brizziite is shown to be incorporated in the white, green and turquoise glazes, and is also associated with lead antimonate and CaSb2O6 in some yellow and white opacifiers. The simultaneous formation of these opacifiers in one glaze might have been accidental. A possible connection between the Achaemenid glaze industry and the Mannean glaze production at Tepe Rabat is discussed. [ABSTRACT FROM AUTHOR]

In this study, biostratigraphy and paleoecology of the Asmari Formation have been investigated. The study area is located in the Izeh zone, Zagros Basin. Four outcrop sections (Halayjan, Kuh Shur, Kuh-e Bad and Gharibi Ha) have been sampled. Based on distribution of the larger benthic and planktonic foraminifera, five assemblage zones have been recognized. Assemblages 1 and 2 indicate Chattian; assemblage 3 is restricted to Aquitanian and assemblages 4 and 5 suggest Burdigalian. During the Chattian, the carbonate deposits of the Asmari Formation are mostly composed of coralline red algae and large and flat benthic foraminifera. The common components of the Aquitanian are abundant imperforate foraminifera and Favreina asmaricus. The Burdigalian is characterized by coral, coralline algae, and perforate and imperforate foraminifera. During the Burdigalian toward the SE of study area (Gharibi Ha section), the shallow water deposits are abruptly overlain by pelagic limestone. It is interpreted as the result of a regional tilting that started in the upper part of the Burdigalian. The biotic associations suggest that carbonate sedimentation occurred in tropical to subtropical waters under oligotrophic to mesotrophic conditions. The carbonate grain associations in the Asmari Formation suggest heterozoan association. According to paleoecological parameters (such as: nutrient, depth, light and salinity) in the study area, the Asmari Formation belongs to nannofor--foralgal to foramol association which were deposited in slightly hyper to normal saline environment. In the euphotic zone, abundant imperforate foraminifera are present. Basinward, lens shaped rotalids developed in mesophotic conditions, and large lepidocyclinid-nummulitids characterize the sediments of the deeper oligophotic zone. [ABSTRACT FROM AUTHOR]

Chemical compaction features are important diagenetic imprints that generally interrupt reservoir quality in most carbonate reservoirs. In the Permian-Triassic reservoirs of South Pars Field, they are recorded in various types and intensities. High- to low amplitude stylolites and solution seams are concentrated within the K1–K4 units of the upper Dalan and Kangan formations, depending on their facies characteristics, diagenetic alterations and dominant lithology. In these units, there are some meaningful trends between the chemical compaction zones and sequence stratigraphic positions including the systems tracts of third-order sequences. Control of chemical compaction on reservoir characteristics is evaluated by using the results of petrographic studies, petrophysical logs and core poroperm measurements. Internal reservoir architecture of the studied reservoirs is determined using the both hydraulic flow units and stratigraphic modified Lorenz plot approaches. Identified baffle and barrier units show close correspondence with chemically-compacted zones. This indicates that zones with high concentration of stylolites and solution seams can be considered as small-scale vertical flow barriers in the Permian-Triassic reservoirs of South Pars Field. [ABSTRACT FROM AUTHOR]

The evaporitic Gachsaran Formation consists of seven members with sequence of anhydrite, marl and salt layers. The first member (the lowest one) which is made up of anhydrite is known as the caprock of the Asmari carbonate reservoir, the most famous hydrocarbon reservoir in Iran. The geomechanical behavior of the Gachsaran Formation is the main concern of drilling and development operations in Iranian oil and gas fields. However, the chief problem is lack of deep core samples from Gachsaran sequences due to the challenging and costly coring process in the non-reservoir Gachsaran formation. In a practical approach of obtaining samples for essential geomechanical laboratory tests, caprock (anhydrite) core samples of Gachsaran Formation have been taken from depths of 80–300 m, at three dam sites. The rock physical and geomechanical properties were examined by analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) tests. The results from analysis of the properties of samples collected from Ghotvand and Chamshir dam sites showed no significant differences, but some of the characteristics of samples of Khersan dam site were considerably different from those of the other samples. Moreover, the physical properties of anhydrite samples were compared with the properties inferred from the petrophysical well logs from a depth of about 2000 m. It was demonstrated that the observed discrepancies between the measured values from Ghotvand and Chamshir samples and those from deep logs are not significant at the 95% confidence level. The investigation results illustrated that anhydrite samples taken from shallow depths can be used for evaluating the geomechanical properties of deeper anhydrites. [ABSTRACT FROM AUTHOR]

The Shurijeh Reservoir Formation of Neocomian age is represented by a sandstone sequence, occasionally interbedded with shale, in the Gonbadli gas field, Kopet-Dagh Basin, Northeastern Iran. In this study X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were used together to characterize the Shuirjeh clay minerals in 76 core samples collected from two deep Gonbadli wells. The results of XRF analysis showed high percentages of silicon and moderate to low percentages of aluminum, sulfur, calcium, potassium, sodium, magnesium, and iron in both wells. The XRD analysis indicated that the above elements were concentrated in the form of quartz, anhydrite, dolomite, calcite, plagioclase, K-feldspar, hematite, and clay minerals. Further XRD examination of the clay fraction revealed that illite, chlorite, and kaolinite were the major types of clay minerals. Unlike, glauconite, smectite, and a mixed layer clays of both the illite–smectite and chlorite–smectite types were observed only in very few samples. The percentages of individual clay minerals were determined using external standard calibration curves and successfully validated by a system of simultaneous linear equations acquired from detailed elemental information based on the XRF analysis. The error reached ± 5% for the main mineral constituent and ± 15% for minor minerals. A local regression relationship was also derived, based on the XRF elemental information, which can be used to estimate the clay contents of other Shurijeh drilled wells with data of pulsed-neutron spectroscopy tools. According to the proposed quantitative approach, the amount of illite varied considerably, reaching 18.3%. In contrast, the amounts of kaolinite and chlorite were generally small, i.e., less than 8.4%. The amount of total clay minerals changed greatly from a minimum of 5% to a maximum of 32.5%. An increase in illite with increasing burial depth and temperature was an obvious indication of deep burial diagenesis in this formation. [ABSTRACT FROM AUTHOR]

The Upper Jurassic (Oxfordian-Kimmeridgian) Mozduran Formation is the most important gas reservoirs of the northeast Iran. Siliciclastic facies of this formation in eastern most parts of the basin have not been studied yet. Therefore, four stratigraphic sections of Mozduran Formation have been selected in the Kole-Malekabad, Kale-Karab, Deraz-Ab and Karizak to interpret depositional history and analyze depositional sequences. Based on texture and sedimentary structures, 14 slilciclastic lithofacies were identified and classified into four categories, including conglomerate (Gms, Gp, Gt), sandstone (Sh, Sp, St, Sr, Sl, Sm, Se), mud rock (Fl) and intermediate sandstone-mud rock (Sr (Fl), Sr/Fl, Fl (Sr)). Identified lithofacies formed four architectural elements CH, SB, LA and FF. Lithofacies characteristics and architectural elements with mostly bimodal pattern of paleocurrents show that the majority of Mozduran lithofacies deposited in the coastal environment (tidal influence). Sequence stratigraphic analysis shows that the Kole-Malekabad section consists of two depositional sequences while other sections are characterized by three depositional sequences. The lower and upper sequence boundaries of the Mozduran Formation in all stratigraphic sections are SB1 that are distinguished by paleosol and sometime conglomerate horizons. Most of depositional sequences in studied sections are composed only of TST and HST. The TST deposits consist mostly of quartzarenite and litharenite petrofacies that have been deposited in the tidal zone. HST packages are mostly including mud rocks with interdeds of sandstone lithofacies that are deposited in supratidal setting. The LST facies is recognized only in the DS3 (equivalent to the second depositional sequences of the Kole-Malekabad), which consist of conglomerate facies. Instead, the Kole-Malekabad section is often composed of supratidal gypsiferrous shales, indicating sea level fall in the study area. [ABSTRACT FROM AUTHOR]

ABSTRACT A detailed magnetotelluric survey was conducted in 2013 in the Sehqanat oil field, southwestern Iran to map the geoelectrical structures of the sedimentary Zagros zone, particularly the boundary between the Gachsaran Formation acting as cap rock and the Asmari Formation as the reservoir. According to the electrical well logs, a large resistivity contrast exists between the two formations. The Gachsaran Formation is formed by tens to hundreds of metres of evaporites and it is highly conductive (ca. 1 Ωm-10 Ωm), and the Asmari Formation consists of dense carbonates, which are considerably more resistive (more than 100 Ωm). Broadband magnetotelluric data were collected along five southwest-northeast directed parallel lines with more than 600 stations crossing the main geological trend. Although dimensionality and strike analysis of the magnetotelluric transfer functions showed that overall they satisfied local 2D conditions, there were also strong 3D conditions found in some of the sites. Therefore, in order to obtain a more reliable image of the resistivity distribution in the Sehqanat oil field, in addition to standard 2D inversion, we investigated to what extent 3D inversion of the data was feasible and what improvements in the resistivity image could be obtained. The 2D inversion models using the determinant average of the impedance tensor depict the main resistivity structures well, whereas the estimated 3D model shows significantly more details although problems were encountered in fitting the data with the latter. Both approaches resolved the Gachsaran-Asmari transition from high conductivity to moderate conductivity. The well-known Sehqanat anticline could also be delineated throughout the 2D and 3D resistivity models as a resistive dome-shaped body in the middle parts of the magnetotelluric profiles. [ABSTRACT FROM AUTHOR]

Geochemical analysis of crude oils from Bangestan and Khami reservoirs, and potential source and reservoirs rocks from the Marun Field in the Dezful Embayment, Zagros Fold Belt Iran show that the Kazhdumi Formation (Fm.) is likely to be thermally mature (at least in the oil window) across the entirety of the Marun field, and that it has excellent generative potential as a source rock. Geochemical data also suggest the Pabdeh Formation has remarkable generative potential but is not thermally mature at the crest of the Marun field, although it is likely to be thermally mature in synclinal regions to the NE and SW. The Gurpi Formation, while thermally mature (early oil window) has marginal generative potential. It is notable, therefore, that oils from the Bangestan and Khami reservoirs have biomarker characteristics that do not match bitumen obtained from the Kazhdumi Formation. Examples of this include the ratio of diasteranes to steranes, the proportions of different carbon numbered hopane homologues and the ubiquitous occurrence of alkylated-trimethyl-benzenes. These biomarker characteristics could only have been imparted to the Bangestan and Khami oils by a source rock other than the Kazhdumi Formation. This contrasts with the stable isotope composition of the Bangestan and Khami oils which suggest correlation to the Kazhdumi Formation. Biomarkers are a quantitatively minor fraction of oil, thus it is possible that the biomarker characteristics of the oils was created by mixing Kazhdumi-bitumen with other petroleum from the Gurpi and Pabdeh formations. This could happen if 1) multiple oil charges from different source kitchens filled the same reservoir, or 2) if oil migrated vertically from the flanks and crossed the Gurpi and Pabdeh formations – both of which have been considered regional seals. Both scenario 1) or 2) would point to a filling history more complicated than previously conceived. [ABSTRACT FROM AUTHOR]

The Aptian carbonate reservoirs of Persian Gulf, known as the Dariyan Formation (Shu'aiba equivalent), are among the most important oil reservoirs of Iran. Despite its significance, a little is known about the facies characteristics, diagenetic history, sequence stratigraphy, and reservoir quality of this formation. Using the new core data, this study presents an integrated geological reservoir characterization of this formation in four giant fields in the Persian Gulf. Using the results of the facies analysis it could be suggested that this unit formed in a shallow carbonate platform surrounding intra-shelf basins of Kazhdumi and Bab in the western and eastern Persian Gulf, respectively. A major relative sea-level fall in the Late Aptian resulted in exposure of this unit and subsequent clastic influx as well as meteoric diagenesis. This phase of meteoric diagenesis has resulted in some important diagenetic features, special geochemical trends, and considerable variations in reservoir quality of the Dariyan Formation. Sequence stratigraphic interpretation of this formation has resulted in the recognition of 2nd and 3rd order depositional sequences in the studied wells. They are closely correlated across the studied wells in the Persian Gulf, SW Iran, and other places in the Arabian Plate. Reservoir characterization has revealed that the high quality units are positioned at two stratigraphic intervals in the concerned reservoir. The first reservoir zone is located beneath the unconformity surfaces, where meteoric dissolution of grain-to mud-dominated facies has resulted in considerable amounts (10–40%) of vuggy, moldic, and micro-porosity in the highstand systems tracts (HSTs). The second reservoir zone of this formation has formed within the Lithocodium-algal facies, floatstone and boundstone, of inner ramp setting. The latter reservoir facies are mainly concentrated within the fields of the eastern Persian Gulf. [ABSTRACT FROM AUTHOR]

A very rare case of deformation is described in which surface cracks are being developed in a period of few months over an area of ca. 55 km 2 in the Late Miocene–Early Pliocene Lahbari Member of Aghajari Formation outcropped in the Azar oil field of western Iran. The cracks are unique because of their activity and their relation to regional tectonic stress field, and not to shallow local processes. The cracks are almost parallel to the NE–SW shortening direction deduced from local folds, and are of almost pure tensile nature. Strike-slip faulting in the area is also in kinematic concordance with the cracks, which show a NW–SE extension direction. Erodibility of the surface geological materials and their downwashing by surface water is affecting the surface morphology very quickly. It is suggested that movement of incompetent underlying Middle Miocene Gachsaran Formation on a lateral ramp of the Zagros Foredeep Fault, and regional active shortening of the sedimentary sequence are responsible for development of the cracks. Construction of the Mohr diagram predicts that maximum depth of the tensile cracks is ca. 220 m. Weak mechanical nature of the Lahbari Member and transient pore pressure are major contributing factors for the crack development. Study of these active cracks may help to better understand the process of active and past fracturing in foreland fold thrust belts. [ABSTRACT FROM AUTHOR]

Two new Permian-aged formations 'Kariz Now Formation' and 'Aliyak Formation' are proposed for a 65-150 m-thick succession in the KarizNow area,with the type section for both (79.5mthick) located 9 kmnortheast of Aliyak village ca. 100 kmsoutheast of Mashhad city, northeastern Iran. The lower Kariz Now Formation is composed of siliciclastics. The age of this Formation is poorly constrained but its correlation with the Shah Zeid Formation in the Central Alborz suggests a possibleAsselian-Hermagorian age for the KarizNow Formation, which implies a hiatus of Yakhtashian-mid Midian (Artinskian-mid Capitanian) age between the siliciclastics of the Kariz Now Formation and carbonates of the disconformably overlying Aliyak Formation. There is also the possibility of a potential correlation of this Formation with the Kungurian Faraghan Formation in the Zagros area. The succeeding Aliyak Formation is mostly composed of carbonate rocks capped by a thin basaltic lava flow. The Aliyak Formation is unconformably overlain by dolostones that are correlated with the Middle Triassic Shotori Formation. Samples were collected from the Kariz Now and Aliyak formations, but fossils were only recovered from the Aliyak Formation. These include calcareous algae, small foraminiferans, fusulinids, crinoid stems and brachiopods. The recovered fusulinid assemblage from the Aliyak Formation is consistent with that of the upper Capitanian Monodiexodina kattaensis-Codonofusiella erki and Afghanella schencki-Sumatrina brevis zones of the Zagros Mountains and with the upper part of the Ruteh Fm in the Alborz Mountains. Although not radiometrically dated, the basaltic lava flow most probably corresponds to similar basaltic lava flows occurring in the uppermost part of the Ruteh Formation in Central Alborz. Thus, the Permian in the studied region developed in a basin that extended westward as far as the Central Alborz. A late Capitanian age for the Aliyak Formation implies it correlates with the Capitanian KS5 in Al Jabal Al-Akhdar in Oman, with Aliyak Unit 5 potentially representing the Permian maximum flooding surface MFS P25. [ABSTRACT FROM AUTHOR]

There are several source rock units in the Zagros Basin. Nevertheless, the Cretaceous Kazhdumi formation has presumably produced the majority of the commercial hydrocarbons in this area. The presence of organic matter rich and thermally mature rock units containing oil or gas prone kerogen is the key factor controlling the hydrocarbon generation potential. Owing to the lack of organic geochemical studies such a potential is poorly investigated in the Azadegan oilfield. In this study, firstly we investigate the lower Cretaceous Kazhdumi formation potential source rock based on geochemical parameters including type and amount of kerogen and thermal maturity, obtained from analyzing 45 cutting samples from 9 wells by using Rock-Eval 6 apparatus. Moreover, vitrinite reflectance measurements were carried out on 11 samples utilizing Zeiss Axioplan II microscope for further examination of the thermal maturation. Burial history analysis and thermal maturity modeling suggests that Kazdumi formation is marginally mature (vitrinite reflectance in the range of 0.5–0.7%) with hydrocarbon expulsion beginning since about 14 Ma. The results indicate increasing maturity from south to the north as a result of burial deepening of the Kazhdumi Formation. It contains type II and mixed types II/III kerogen with TOC (Total Organic Carbon) values up to 4.88 wt% and Source Potential Index (SPI) value of 3.72 t HC/m 2 providing a moderate source for the hydrocarbons encountered in the reservoir rocks. In the second part of this research, we attempt to characterize the Kazhdumi source rock by using intelligent systems. In this regard, a three-layered back-propagation Artificial Neural Network (ANN) with Levenberg–Marquardt (LM) training algorithm was designed to predict TOC values from well log data (RHOB, THOR, SGR, NPHI, DT). This network is capable of predicting TOC with correlation coefficient of 98.63% and 82.62% and MSE of 0.0067 and 0.1772 for training and testing steps, respectively. According to the ANN modeling and TOC distribution map, organic richness of the Kazhdumi formation increases from south to the north over the study area. [ABSTRACT FROM AUTHOR]

The Coastal Fars and the Iranian part of the Persian Gulf are one of the largest natural gas provinces in Iran. More than 90 percent of the natural gases in these areas are found in Dalan (Upper Permian) and Kangan (Lower Triassic) carbonate rocks. In order to determine the origin of the natural gas in Iranian sector of Persian Gulf and Coastal Fars area, we collated 23 gas samples (7 samples from Kangan Fm. 12 samples from Upper Dalan and 4 samples from Lower Dalan) from 12 gas fields in the study area and analyzed chemical and isotopic composition. Based on molecular composition and isotope data, gas samples in the study area have the thermogenic origin. In the lower part of Dalan Formation, evidence of secondary process like thermochemical reduction of sulfate (TSR) is seen. The main part of hydrocarbon gases was generated during secondary cracking of paleo-oil in these reservoirs. Based on this study, lower Silurian organic-rich shales (Sarchahan Formation) with the 1–1.8 vitrinite reflectance, is the main source for the natural gas of southern Iran. [ABSTRACT FROM AUTHOR]

To study lithostratigraphy and microbiostratigraphy of Tarbur Formations in southwest Khorram Abad (Lurestan), one stratigraphic section of the Tarbur Formation was selected in Cham-e Sangar area. Lithostratigraphic studies reveal limestone, dolomitic limestone, sandy limestone, shale and marl in this section. Identified index lithofacies in this section include grainstone, packstone and wackstone. Microbiostratigraphy studies provided on 67 thin sections from 77.3 m of Tarbur Formation sediments in Cham-e Sangar section indicate the existence of 12 genera and 23 species of benthic foraminifers. Based on assessment of an existing set of foraminifera, Omphalocyclus- Loftusia assemblage zone has been proposed for the Cham-e Sangar section. Micropaleontological studies suggest middle-Maastrichtian to late Maastrichtian age for Tarbur Formation in southwest Khorram Abad. The studies were performed for the first time in Lurestan province, Tarbur Formation where index lithology and fauna of Maastrichtian interbeds in the clastic-conglomerate deposits of Amiran Formation base as a tongue, or a projecting part of a lithostratigraphic unit extending out beyond its main body. This study indicates the age of the Amiran Formation basal part as Maastrichtian. [ABSTRACT FROM AUTHOR]

The Upper Jurassic Mozduran Formation (Oxfordian-Tithonian) is the main petroleum reservoir in the Kopet-Dagh Basin, northeast Iran, which consists predominantly of carbonate rocks with subordinate evaporites and siliciclastics deposited in platform to deep marine settings of a subtropical sea. Detailed field surveys, petrographic investigations, facies and wire line log analyses were carried out at eight surface sections and four wells in the Kopet-Dagh Basin. Integration of petrographic and isotopic data suggests primary low-Mg calcite mineralogy of Oxfordian and Tithonian ooids. On the other hand, in the wells, Kimmeridgian ooids and cements are dominantly aragonitic and high-Mg calcite mineralogy (HMC). Marine cements with isopachous, fibrous and isopachous bladed fabrics indicate original aragonite and HMC mineralogy, respectively. The domination of aragonite mineralogy could be related to increased hypersalinity, evaporite precipitation and consequently an increase in Mg/Ca ratio, which resulted in formation of aragonite in preference to calcite. Preserved ooids with radial and concentric cortices in shallow-water settings that are nearby siliciclastic source, together with aragonitic and HMC ooids accompanied by evaporites in the drilled fields, suggest original mineralogy was probably controlled inorganically following local salinity variations. This study suggests that Kimmeridgian pay zones are mainly controlled by depositional facies, aragonitic and HMC mineralogy, and diagenetic processes such as dolomitization and dissolution. [ABSTRACT FROM AUTHOR]

The Sachun Formation in the Zagros Mountains Ranges was sampled on the basis of changes in lithology and 150 vertically oriented thin-sections were prepared and subjected to detailed petrographic study. Evaporite, carbonate and shale/marl facies are identified here. These facies which have been laid in 4 facies belts of supratidal, intertidal, lagoon and barrier, deposited on a ramp platform. Petrographic studies showed that the Sachun Formation has had a complex diagenetic history. The following diagenetic events occurred in the carbonate microfacies: micritization, dissolution, silicification, dolomitization, hematitization, compaction, fracturing and stylolitization. The diagenetic features observed petrographically in the carbonate microfacies represent changes which took place under three diagenetic environments (eogenic, mesogenic, and telogenic) with three different marine, burial, and meteoric diagenetic conditions. The diagenetic sequence of events that affected the Sachun Formation includes micritization and micrite envelope features which have been reported from an eogenic/marine environment. [ABSTRACT FROM AUTHOR]

The record of conodonts related to the Mississippian/Pennsylvanian boundary interval was investigated in four sections in Central Iran from two different structural units. Two sections from the Sanandaj-Sirjan trend zone (Asad-abad, and Darchaleh sections) and two from the East-Central Iran Microplate (Shesh-angosht and Kale-Sardar sections) exhibit a nearly complete record previously described across the Mississippian/Pennsylvanian boundary in Iran. The investigated sections can be subdivided in three formations (Ghaleh-, Absheni-, and Zaluda Formation) which belong to the Sardar Group. The mid-Carboniferous boundary was defined by the occurrence of Declinognathus noduliferus s.l.. Bio-event characteristics of the Carboniferous conodont fauna (Mississippian genera Gnathodus and Lochriea have been replaced by Pennsylvanian genera Declinognathus and Idiognathodus) as well as sedimentological changes within overall shallow water deposits were located approximately 33° S of the paleoequator and suggest sea-level changes within the framework of the Late Paleozoic Ice Age (LPIA). Furthermore, a widespread crinoid marker horizon previously described from two localities in Iran can be subdivided into three units of different ages. [ABSTRACT FROM AUTHOR]

Early Cretaceous shallow carbonate deposits in the Zagros fold-thrust belt, SW Iran, are being studied for a high-resolution stratigraphic pattern and detailed environmental analysis. These carbonates contain diversified assemblages of dasycladalean algae, indicating shallow subtidal depositional environments. A new dasycladalean alga and interesting marker is described as Mizzia zagarthica sp. nov. from Late Berriasian-Early Valanginian deposits of the Fahliyan Formation. Focusing on the presence of reproductive organs (cysts) in the laterals, the genus, which so far has been reported only from the Permian, is emended. Based on newly described material from Greece and New Mexico, the genus Mizzia is re-assessed. The paper also includes a critical revision of the genera Neomizzia and Banciloporella. [ABSTRACT FROM AUTHOR]

Wilmsen, M., Storm, M., Fürsich, F.T. and Majidifard, M.R. 2013. Upper Albian and Cenomanian (Cretaceous) ammonites from the Debarsu Formation (Yazd Block, Central Iran). Acta Geologica Polonica, 63 (4), 489-513. Warszawa. New ammonite faunas consisting of 13 taxa provide the first reliable biostratigraphic dating of the Debarsu Formation of the Yazd Block, west-central Iran, indicating several levels in the Upper Albian and Lower Cenomanian, while a foraminiferal assemblage places the top of the Formation in the Middle Turonian. Among the identified ammonite taxa, Acompsoceras renevieri (Sharpe, 1857) is recorded from Iran for the first time. The upper part of the lower Upper Albian is proved by the occurrences of mortoniceratines of the Mortoniceras (M.) inflatum Zone in the lowermost part of the Debarsu Formation. For the upper Upper Albian (traditional Stoliczkaia dispar Zone), the M. (Subschloenbachia ) rostratum and M. (S.) perinflatum zones are proved by their index taxa. However, there is no evidence of the terminal Arrhaphoceras (Praeschloenbachia) briacensis Zone. The upper part of the lower Lower Cenomanian Mantelliceras mantelli Zone (M. saxbii Subzone) is proved by M. saxbii and M. cf. mantelli. Below, there is an ammonite- barren interval of ca. 100 m in thickness between M. (S.) perinflatum zonal strata and the M. saxbii Subzone. The upper Lower Cenomanian is documented by the presence of typically M. dixoni zonal ammonites such as Acompsoceras renevieri. Upper Cenomanian and Turonian ammonites have not been found in the upper part of the Debarsu Formation, but micro-biostratigraphic evidence (planktonic foraminifers) from the uppermost part of the formation indicate that the formation ranges into the Turonian. For the development of the major tectonic unconformity at the base of the overlying Haftoman Formation (which yielded Lower Coniacian inoceramids near its base), only 2-3 myr remain, stressing the geodynamic activity of Central Iran during mid-Cretaceous times. [ABSTRACT FROM AUTHOR]

• Gypsum rocks in parsian reservoir enhances risk of water quality degradation. • Dissolution rate was estimated between 0.023 and 0.056 gr/cm2-day through experiments. • The reservoir salinization was modeled by CE-QUAL-W2 under different scenarios. • Dissolution could enhance the average TDS of the dam outflow from 1429 to 1722 mg/L. • Omitting a saline inflow river at upstream reduces TDS in outflow to 900 mg/L. Saline inflows and soluble geological formations outcropped in reservoirs contribute to reservoir water salinization (RWS). We set up 32 laboratory tests to better understand rock-water interaction and determination of dissolution rate of Gachsaran geological formation (GGF) in the Parsian dam that is currently under the study phase on the Fahlian river, Iran. Then, we used CE-QUAL-W2 (W2) to simulate GGF dissolution outcropped in some parts of the reservoir. Finally, possible solutions for mitigating the RWS were investigated using W2 driven under different scenarios: (1) having Hamze-beigi saline inflow (a main tributary of the Fahlian river) and GGF dissolution, (2) removing the saline inflow, (3) confining the GGF dissolution, and (4) driving W2 in severe floods. Although the dissolution rates (0.023–0.056 gr/cm2-day) salinize deep water, saline inflow degrades surface waters. Density gradient in the water depth formed the monimolimnion and mixolimnion separated by a distinct pycnocline in the reservoir. The pycnocline established in the early impoundment stage and lasted throughout the study period (2002–2012), leading to a crenogenic meromixis state in the reservoir. W2 driven under the 100–year and 1000–year inflows shows salinity up to 2700 mg/L in top layers from partial chemical mixing in the reservoir in cold months, although no conversion of the lake from the meromixis to holomictic state was observed in warm months. The findings suggest that, although diversion of the saline inflow satisfies the salinity requirement for hydropower generation, peak saline inflow can salinize the reservoir water and downstream river. [ABSTRACT FROM AUTHOR]

The area of Arghash in northeast Iran, prominent for its gold mineralization, was newly mapped on a scale of 1:20,000 with particular attention to the occurring generations of igneous rocks. In addition, geochronological and geochemical investigations were carried out. The oldest geological unit is a late Precambrian, hornblende-bearing diorite pluton with low-K composition and primitive isotope signatures. This diorite (U-Pb zircon age 554 ± 6 Ma) is most likely a remnant from a Peri-Gondwana island-arc or back-arc basin. About one-third of the map area is interpreted as an Upper Cretaceous magmatic arc consisting of a volcanic and a plutonic part. The plutonic part is represented by a suite of hornblende-bearing medium-K, I-type granitoids (minor diorite, mainly quartz-monzodiorite and granodiorite) dated at 92.8 ± 1.3 Ma (U-Pb zircon age). The volcanic part comprises medium-K andesite, dacite and tuffitic rocks and must be at least slightly older, because it is locally affected by contact metamorphism through the hornblende-granitoids. The Upper Cretaceous arc magmatism in the Arghash Massif is probably related to the northward subduction of the Sabzevar oceanic basin, which holds a back-arc position behind the main Neotethys subduction front. Small occurrences of pillow basalts and sediments (sandstone, conglomerate, limestone) tectonically intercalated in the older volcanic series may be relics of earlier Cretaceous or even pre-Cretaceous rocks. In the early Cenozoic, the Cretaceous magmatic arc was intruded by bodies of felsic, weakly peraluminous granite (U-Pb zircon age 55.4 ± 2.3 Ma). Another strong pulse of magmatism followed slightly later in the Eocene, producing large masses of andesitic to dacitic volcanic rocks. The geochemistry of this prominent Eocene volcanism is very distinct, with a high-K signature and trace element contents similar to shoshonitic series (high P, Zr, Cr, Sr and Ba). High Sr/Y ratios feature affinities to adakite magmas. The Eocene magmatism in the Arghash Massif is interpreted as related to thermal anomalies in crust and mantle that developed when the Sabzevar subduction system collapsed. The youngest magmatic activities in the Arghash Massif are lamprophyres and small intrusions of quartz-monzodiorite porphyries, which cut through all other rocks including an Oligocene-Miocene conglomerate cover series. [ABSTRACT FROM AUTHOR]