Biostratigraphy,sequence stratigraphy,and paleoecology of the Lower–Middle Miocene of Northern Bandar Abbas,Southeast Zagros basin in south of Iran

The Guri Member is a limestone interval at the base of the calcareous marls of the Mishan Formation. It is the youngest hydrocarbon reservoir of the southeast part of the Zagros sedimentary basin. This Member overlaid siliciclastic rocks of Razak Formation and is overlain by green and gray marls of the Mishan Formation. In order to consider the paleoecology and paleoenvironments of the Lower–Middle Miocene (Guri Member), we have studied biostratigraphy and sequence stratigraphy of the Guri Member based on foraminifer and microfacies in two stratigraphic sections including Dorahi–Homag and Chahestan. A total of 33 genera and 56 species of benthic and planktonic foraminifera were identified in two studied stratigraphic sections. Benthic and planktonic foraminifera demonstrate Aquitanian to Langhian age (Early–Middle Miocene) for this Member at the study area. Studied interval has deposited in four facies association including supratidal, lagoon, coral reef, and open sea on a carbonate ramp. Carbonate rocks of the Guri Member have precipitated in two and three depositional sequences at Chahestan and Dorahi–Homag sections, respectively. Sedimentation of marine carbonates of the Guri Member on siliciclastic deposits reflects a major transgression of sea level at Lower to Middle Miocene that led to creating a new sea in the Zagros basin at that age. Increasing siliciclastic influx along with a sea level fall finally caused burying of the carbonate ramp. Except for the beginning of sedimentation of carbonate at the base of both stratigraphic sections (depositional sequence 1), most of the system tracts are not matched to global sea level curve that reflect local effects of the basin. Distribution of foraminifera suggests precipitation in tropical to subtropical in mesotrophic to oligotrophic and eutrophic to oligotrophic conditions. Based on large benthic foraminifera (porcelaneous large benthic foraminifera and hyaline larger benthic foraminifera), water temperature average was determined between 25 and 30 °C that was confirmed by analyzing oxygen and carbon stable isotopes. Finally, we have utilized achieved data to reconstruction and modeling of paleoecology, paleoenvironments, and sea level changes in the southeast part of the Zagros basin.     

The comparison of hydrodynamic characteristics of karst aquifers: application on two karst formations in Zagros (Asmari and Ilam-Sarvak), southwest Iran

In order to study the function, hydrodynamic behavior, and hydraulic properties of the karst aquifers in Izeh, southwest Iran, time series analysis was applied to the precipitation, spring discharge, and piezometric head data of two representative karst systems of Zagros (Ilam-Sarvak and Asmari Formations). Time series analysis was applied to two karst aquifers, those of Asmari and Ilam-Sarvak Formations. The daily precipitations of anticlines were estimated based on the precipitation–elevation function which was applied on digital elevation model (DEM) of the area. The mean estimated daily precipitations were considered in bivariate time series analysis as input data of each karst system. The total length of time series was about 2.7 years, extending from May 2007 to December 2009. During the research, several one-parameter probe data loggers were installed, which daily measure the water surfaces in karst aquifers. Time series analysis was applied for describing Izeh karst aquifers with a focus on both univariate (autocorrelation and spectral analysis) and bivariate (cross-correlation, gain function, and coherency function) methods. The results show that Asmari karst aquifer in Kamarderaz Anticline has a large storage capacity. Because of lacking a well-organized karst network, in the Asmari karst aquifer, baseflow dominates with low contribution of quick-flow. In the Ilam-Sarvak karst aquifer (Shavish and Tanush Anticlines), the karstification occurred in fractures and small diameter conduits, which caused to quick-flow between dense limestone. The Ilam-Sarvak karst aquifer could be regarded as a transition between two extreme types of karst, e.g., highly karstified system and in the opposite, extremely diffused one. The analysis of well hydrograph in Ilam-Sarvak karst aquifer shows that the karst aquifer has a low storage capacity. Unlike Asmari karst aquifer, the fractures and small diameter conduits in Ilam-Sarvak karst aquifer are more enhanced, producing a better developed karst network. Contrary to the typical karst systems, however, diffuse flow and conduit flow coexist in the Asmari Formation.     

Electrofacies in gas shale from well log data via cluster analysis: A case study of the Perth Basin,Western Australia

Identifying reservoir electrofacies has an important role in determining hydrocarbon bearing intervals. In this study, electrofacies of the Kockatea Formation in the Perth Basin were determined via cluster analysis. In this method, distance data were initially calculated and then connected spatially by using a linkage function. The dendrogram function was used to extract the cluster tree for formations over the study area. Input logs were sonic log (DT), gamma ray log (GR), resistivity log (IND), and spontaneous potential (SP). A total of 30 reservoir electrofacies were identified within this formation. Integrated geochemical and petrophysics data showed that zones with electrofacies 3, 4, 9, and 10 have potential for shale gas production. In addition, the results showed that cluster analysis is a precise, rapid, and cost-effective method for zoning reservoirs and determining electrofacies in hydrocarbon reservoirs.     

Stable isotope (O and C) geochemistry of non-sulfide Zn–Pb deposits; case study: Chah-Talkh non-sulfide Zn–Pb deposit (Sirjan,south of Iran)

The study of oxygen and carbon isotopic ratios has gained importance to determine the origin of ore-bearing fluids, carbon origin, and also to determine the formation temperature of non-sulfide Pb and Zn minerals. In order to determine the origin of fluids and carbon existing in Zn carbonate minerals in Chah-Talkh deposit, initially the amounts of δ¹⁸O_SMOW and δ¹³C_PDB changes in various zinc minerals in important deposits in Iran and the world were studied, and then by comparing these values in Chah-Talkh deposit with those of other deposits, the origin of fluids responsible for ore forming, carbon, and formation temperature of Chah-Talkh deposit was determined. The range of δ¹⁸O_SMOW changes in smithsonite mineral in non-sulfide lead and zinc deposits varies from 18.3 to 31.6 ‰, and δ¹⁸O_SMOW in hydrozincite mineral varies from 7.8 to 27 ‰. Due to the impossibility of smithsonite sampling from Chah-Talkh deposit (due to it being fine-grained and dispersed), hydrozincite minerals which have high isotopic similarities with smithsonite are used for the isotopic analysis of carbon and oxygen. The range of δ¹⁸O_SMOW changes in hydrozincite mineral of Chah-Talkh deposit varies from 7.8 to 15.15 ‰, which places in the domain of metamorphic water. The extensiveness of δ¹⁸O_SMOW changes in Chah-Talkh indicates the role of at least two fluids in the formation of non-sulfide minerals. The obtained formation temperature of non-sulfide minerals (hydrozincite) in Chah-Talkh deposit is 70 to 100 °C, which indicates the role of metamorphic fluids in the formation of deposit. Complete weathering of sulfide minerals to a depth of 134 m confirms the role of rising metamorphic fluids in the formation of non-sulfide minerals. The δ¹³C_PDB values of Chah-Talkh deposit are set in the range of atmospheric CO₂ and carbonate rocks, in which the existence of atmospheric CO₂ indicates the role of atmospheric fluids, and the existence of carbonate carbon rock indicates of the role of metamorphic fluids in the precipitation of non-sulfide Zn minerals.     

Source of salinity in the groundwater of Lenjanat Plain,Isfahan, Iran

The present study aimed at identifying the salinity source in the groundwater of Lenjanat Plain. To do so, non-isotopic geochemical methods were employed: groundwater samples were collected seasonally from 33 wells widespread in the area, and physicochemical parameters as well as major and minor elements were measured in the 132 samples. The data collected from the field and laboratory measurements were interpreted through statistical and hydrogeochemical graphs, mass ratios and saturation indexes obtained from modeling. The results revealed that hydrogeochemical properties of the study aquifer were controlled by rock/water interactions including ion exchange, dissolution of evaporation deposits (halite and gypsum) and precipitation/dissolution of carbonates. Based on the values of Cl/Br ratio in Lenjanat groundwater (329–4,492), dissolution of evaporation deposits in aquifer was the main cause for groundwater salinity. Considering the Lenjanat groundwater geochemical properties, the data confirm the reported Cl/Br ratios for groundwater affected by the dissolution of evaporation deposits (Cl/Br > 300) and overlaps with the range of Cl/Br ratios for domestic sewage effluent groundwater. Selecting the best chemical components and their ratios in non-isotopic geochemical methods provides an accurate distinction between sources of groundwater salinity.     

Correlation of production rate of ornamental stone with rock brittleness indexes

The prediction of production rate in ornamental stones sawing is very important in cost estimation and process planning of the rock sawing plants. The main aim of this paper is finding a mathematical correlation between production rate and rock brittleness indexes. The utilized data have been collected from several stone factories in Iran. Seventeen different granite and carbonate rocks have been experienced sawing conditions with large-diameter circular saws. The laboratory tests such as uniaxial compressive strength and tensile strength, were carried out on the rock samples which were collected from these factories. The ratio of compressive strength to tensile strength (B ₁), the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength (B ₂), and the area under the line of compressive strength and the line of tensile strength (B ₃) were used as brittleness indexes in this study. Then, the relationships between these brittleness indexes and production rate were investigated by using a regression analysis. The results show that, there is not a good relationship between the production rate and B ₁ and B ₂. However, the production rate correlates with B ₃ very well. Therefore, there is a reliable prediction for ornamental stones production based on B ₃ as a brittleness indexes.     

Evaluation of sediment yield and soil loss by the MPSIAC model using GIS at Golestan watershed, northeast of Iran

Watershed degradation due to soil erosion and sedimentation is considered to be one of the major environmental problems in Iran. In order to address the critical conditions of watershed degradation in arid and semiarid regions, a study based on the Modified Pacific Southwest Inter-Agency Committee (MPSIAC) model was carried out at Golestan watershed, northeast of Iran. The model information layers comprising nine effective factors in erosion and sedimentation at the watershed site were obtained by digitalization and spatial interpolation of the basic information data in a GIS program. These factors are geology, soil, climate, runoff, topography, land cover, land use, channel, and upland erosion. The source data for the model were obtained from available records on rainfall and river discharge and sediment, topography, land use, geology, and soil maps as well as field surveys and laboratory analysis. The results of the MPSIAC model indicated that 60.75 % (194.4 km²) and 54.97 % (175.9 km²) of the total watershed area were classified in the heavy sedimentation and erosion classes, and the total basin sediment yield and erosion were calculated as 4,171.1 and 17,813.4 m³ km^?2 year^?1, respectively. In the sensitivity analysis, it was found that the most sensitive parameters of the model in order of importance were topography (slope), land cover and use, runoff, and channel erosion (R ²?=?0.92–0.94), while geology, climate (rainfall), soil, and upland erosion factors were found to have moderate effect to the model output (R ²?=?0.74–0.59).     

Groundwater exploration using remote sensing and geographic information systems in a semi-arid area (Southwest of Urmieh, Northwest of Iran)

Shortage of water required for drinking and agricultural uses is a subject with a vital importance in most arid and semi-arid regions. The area of this study is one of the semi-arid regions located in southwest of Urmieh lake, northwest of Iran, between N 37°00′, 37°15′ latitude and E 45°05′, 45°30′ longitude which is composed of Permian dolomitic limestone, limestone, and post-Jurassic granite with a very low primary porosity/permeability character. In order to delineate groundwater potential zones in this area, the study focused on identifying secondary porosity/permeability indicators such as lineaments, vegetation cover, lithology, drainage pattern, drainage density, etc. In this regard, a remote sensing and geographic information system-based methodology was selected. Landsat ETM, IRS (pan), SPOT data, digital elevation model, and digital image processing techniques such as filtering, false color composite, principal component analysis, band rationing and classification have been applied to reach the purposes. Information layers extracted for analysis and interpretation stage were then integrated with other data and modeled through the use of existing geographic information system (GIS) software and their related analytical functions. Finally, based on determined ground water favorability index for different sub zones, layers, weighting, and overlapping, a ground water potential index (GWPI) was defined which respectively was utilized to groundwater potential zoning and preparation of GWPI map of the region. Within the six different sub zones defined, two sub zones labeled with high and very good potential areas were highly recommended for further development and exploration purposes. Geophysical investigations in target areas confirm the labeled subzones. Based on the obtained results of the study, it can be concluded that remote sensing data are very useful tool to extract information of groundwater exploration. Also, application of geographic information systems to find target areas for groundwater exploration are effective to save time and cost.     

Optimizing 3-D seismic survey design parameters using genetic algorithm—a case study in southwest of Iran

The crucial advantages of a 3-D seismic survey are the proper migration of the reflection points and the more accurate study on the structural and stratigraphic targets, reservoir characterization, and joint study. In this article we will focus on Pardis Project in southwest of Iran where no 3-D seismic survey has ever been carried out. The local geological information, previous 2-D seismic, VSP data, and interval velocity information obtained from check shots were taken into consideration to determine the requirements of the survey. The objective is to adequately sample the primary and secondary targets at the depth of 1,200 and 5,000 m, respectively. On the base of the logic dominating a genetic algorithm, the best operational layout was offered to satisfy the geophysical requirements looking forward to satisfy financial constraints. Using Genetic Algorithm Toolbox in MATLAB, we could formulate a mathematical constrained optimization problem. Applying this technique we derived nominal designs which are needed to be evaluated to make sure how well they could image the targets.