Geopersia
Volume:11 Issue: 1, Winter-Spring 2021

3D seismic attributes and well logs were used to estimated porosity and water saturation in the Asmari Formation in the Dezful Embayment, SW Iran. For this purpose, at first, the 3D seismic volume was inverted base on the model, to obtain acoustic impedance cube. Afterward, the impedance and other attributes extracted from seismic volume were analyzed by multiple attribute regression transform and neural networks to predict porosity and water saturation between wells. Then linear or non-linear combinations of attributes performed for porosity and water saturation prediction. The result shows that the match between the actual and predicted porosity and water saturation improved; using only a single attribute to the derived multi attribute transforms and neural networks model. Based on the results of neural networks, the highest cross-correlation was observed between seismic attributes and the observed target logs between seven wells in the study area. Based on our study, the cross-correlation between actual and predicted porosity and water saturation increased and reached 93% and 90% respectively in the case of using probabilistic neural networks (PNN). Finally, according to the cross-validation results, PNN neural networks are used for porosity and water saturation prediction.

The April 5th 2017 Mw 6.15 Sefidsang earthquake occurred east-northeast of the town of Fariman near the Cimmerian arc-related Fariman complex. The stress distribution was estimated by seismic parameters and Coulomb stress distribution in the source region. Inferred Coulomb stress field and general pattern of aftershocks distribution revealed that the Sefidsang earthquake occurred on a northeast-dipping listric fault with dextral reverse movement. Proximity of the Sefidsang sequence to Fariman complex proposes the reactivation of the pre-existing Cimmerian arc-related faults in the present-day stress field. The crustal-penetrating low-angle inverted faults coupled with Mesozoic mafic–ultramafic magmatism can shed light on the structural aspects of the region. The kinematics was also investigated by GPS velocity fields and morphotectonic features. The counterclockwise block rotation under the left-lateral regional shear between the Doruneh fault system and the North Kopeh Dagh fault system and NE-oriented coeval shortening led to the formation of rhombic structures. Cimmerian-related basement faults in NE Iran confined the expansion of rhombic cells and sense of block rotation. The results of this study improved our understanding about kinematics of active deformation in NE Iran and had important implications for seismic hazard assessment of the region and potential future failure area.

The study area is part of the northern Urmia-Dokhtar Magmatic Belt. The northern part of this belt consists of andesite, basalt and acidic tuff. There are hyaloclastites with a distinctive bedding only in the northwestern Mahneshan area and northern Urmia-Dokhtar magmatic belt. In this region volcanism began during the Oligocene time with extremely strong hyaloclastite eruptions, and then with a stop, the volcanism continued with exceptionally extensive acidic tuff eruptions, and eventually ended up with basaltic andesite lava eruptions in the late Miocene. Field, mineralogical and petrographic studies on the major and minor minerals of the volcanic and sedimentary rocks indicate that three phases of volcanism occurred in this area. These three phases are: hyaloclastites, acidic tuffs and volcanic Lavas. hyaloclastites (Phase 1), are often composed of andesite and quartz-andesite to dacite. The highly extensive phase 2 consists of acidic tuffs interbedded with limestone. According to the fossil content and the 87Sr/86Sr age determination, this phase formed during the Chattian to Aquitanian ages. Phase 3 includes andesite-basalt, andesite and sometimes quartz-andesite. Based on the geochemical diagrams all three phases are located within the calc-alkaline field, indicating the subduction of an oceanic crust under the continental crust.

The purpose of this research is to introduce road tourist attractions. Geotrial attractions of Haraz Road (Haraz Valley), located in the Alborz Mountain, are presented in this article. The Haraz Road (Road 77) is one of the most beautiful roads in the world that connects the capital of Iran (Tehran) to Mazandaran province. In this research, the geodiversity attractions of the area outside the urban context, in the Jajrud Neck to the Filband zone have been investigated. There are 17 stops along the road. The basis of this research has been the transfer of knowledge and experience of over 20 years of field visits to this road. This research was conducted due to the various interests in the Haraz road, such as geodiversity, cultural, historical, religious, and ecological attractions. The most attractive tourist sites along the Haraz road include Lar plain, Qal'e Dokhtar, Shahandasht waterfalls, Imamzadeh Hashem, Damavand peak Gol-e Zard cave, Damavand Icy waterfall, Basaltic prisms, kafer-Keli crypts, and Shahi Bridge. This road is the cheapest road geotourism option for middle to low-income people.

The effect of different recharge sources on the chemical evolution of an urban aquifer, Behbahan plain, southwest of Iran, has been studied using hydrogeochemistry and stable isotopes (18O and 2H). Groundwater samples were collected from 40 water wells in June 2017 and April 2018 as the dry and wet periods, respectively. The water samples were analyzed for the determination of major ions, nitrate, fluoride, and bromide for both periods and stable isotopes concentrations only for the dry period. The hydrochemical maps was investigated to determine anomalous groundwater zones associated with urban sources of groundwater pollution. Characteristic bivariate composition diagrams and cluster analysis (CA) method were employed to identify the hydrochemical processes and to evaluate the recharge sources. Two major water types Ca-SO4 and Ca(Na)-SO4(Cl) were present in the Behbahan groundwater plain. The dominant hydrogeochemaical processes in the aquifer were the dissolution of gypsum and somewhat halite, dedolomitization, scant normal and reverse cation exchange, and mixing. The main sources of the nitrate pollution of groundwater were leaching of organic manure applied to cultivated areas as well as wastewater of Behbahan City. Five distinct recharge sources were recognized for the Behbahan aquifers based on the characteristics of 2H and 18O isotopes.

Fault-related folding, due to the variety of tectonic setting, seismic and economic importance, has always been of interest to geologists. In this study, we investigate the influence of different aspects of the mechanical parameters (Young's modulus, Poisson's ratio, dilation angle, and cohesion) and boundary conditions (overburden pressure) to determine the fault-propagation folding style and its mechanical evolution through the use of a series of 2D finite-element elastic-plastic models so that the use of inelastic relationships allows permanent strains to develop in response to the applied loads. All FE-models with the mechanical parameters reduced to 15%, except for Young’s modulus and overburden pressure, lead to lower half- wavelength and amplitude values concerning the reference model, and as these parameters are changed by 15% and 30% simultaneously to validate the results, the area reduction is dramatically increased. FE-model results show that area changes in fault propagation fold are as a function of mechanical stratigraphy, mechanical parameters, and overburden pressure. Area loss can also lead to a decrease in permeability through intergranular mechanisms. We apply these insights to the Ayegan anticline, central Alborz that generally show well-designed FE-modelling matched overall structural geometry in the kink-style kinematic model.

This study is aimed to determine geochemical anomalies of rare earth elements (REEs) and provides a concentration distribution map for the Esfordi phosphate deposit (EPD), Bafq metallogenic province (BMP), Central Iran. With an average grade of 5519 ppm for REEs, the EPD is one of the prominent deposits of the region. In this research, sequential Gaussian simulation (SGS) and concentration-area (C-A) fractal modeling are used to determine concentration anomalies and provide a ∑REEs concentration map based on surface data. The log-ratio matrix is used to investigate the mineralization processes, determining the relationships between the anomalies and the rock units, and validating the results of SGS fractal modeling. The results are indicating that the main anomaly has strong correlation with the apatite-iron, and in particular, with the apatite mineralization, which can be considered as an exploration guide. The results also confirm the efficiency of simultaneous application of fractal modeling and SGS simulation.

In this paper, the land subsidence across Arak plain, a relatively vast plain located in central Iran, caused by groundwater level drop is calculated using Mohr-Coulomb elastoplastic model. Also, a modified finite element model is applied via Plaxis2D commercial software for validation. Five borehole stations at given locations across the Arak plain are considered, namely Gavkhaneh, Ebrahimabad, Safarabad, Amanabad, and MojedabadKohneh, and the mentioned model is applied at each borehole. The acquired results show a subsidence average value of 26.6 cm for 17.85 m of groundwater level drop along 1991-2014. Also, the lowest aggregated subsidence value until 2014 is observed at Safarabad station being 0.2 cm, while its maximum value is observed at Gavkhaneh station being 88.75 cm. The acquired results reminds the necessity of groundwater resources management measures and supervision over exploitation amounts.

In this paper, an inverse framework based on Bayes’ theorem is suggested for integrating well logs and seismic data into reservoir lithofacies modeling process. The proposed method is based on combination of the Sequential Indicator Simulation (SIS), and a stochastic optimization method (i.e. Probability Perturbation Method (PPM)). SIS is used to calculate the conditional probability of presence/absence of lithofacies indicators in each grid-block, and PPM is applied to update (perturb) the conditional probability used in SIS. A notable innovation presented in this study is using the Genetic algorithm’ crossover operator to increase the PPM exploitation capability. To demonstrate the efficiency of our proposed approach, the results of its application on a 3D test model is compared with outcomes of two commonly-used constraining approaches on SIS. Qualitative and quantitative analysis of the obtained results on 3D test model reveals a (23.8)% and (16.98)% (on average) improvement in consistency of lithofacies models generated using the proposed approach with the reference lithofacies model over the employed Vertical Probability Trend and Seismic Probability Trend constraining approaches on SIS, respectively. Besides, the obtained results show that implementing crossover operator leads to a 4.56% improvement in matching of the constructed lithofacies models with the reference model.

A tsunami had struck the Ami tribe’s settlement on the eastern coast of Taiwan in 1771. The trigger of this tsunami is still debatable. Hence, the analysis of tsunami deposits in Fengbin is needed to understand the chronology of the tsunami. There are three types of sediment samples taken from the study area, namely modern beach sand, modern fluvial sand, and sediment materials from the marine terrace. Sample analysis was carried out using the point counting, granulometry, biozonation, and paleo-bathymetry methods to determine the facies, provenance, and sediment transport mechanisms. The results of field observation indicate the presence of marine shells on the sediment deposit of marine terraces at elevations between 10.5-12.5 m. The thickness of this deposit is between 15-20 cm in the fining upward succession and there is a rip-up clast sedimentary structure. The characteristic of this deposit is similar to tsunami deposits found on the Ishigaki and Miyako Islands, Japan. The conclusion of this study is that there is a tsunami deposit in Fengbin associated with the tsunami deposits found in Miyako and Ishigaki Islands, Japan. The trigger of the tsunami in Fengbin probably attributed to tectonic activity in the Ryukyu Trench.

To determine the effect of climate changes on current critical conditions of Lake Urmia, paleoclimate of southern wetlands of Lake Urmia was investigated based on clay mineralogy. Solduz and Kani Barazan wetlands on the southern margin of Lake Urmia and also the southern part of the lake have been briefly studied in this research.A total of 24 sedimentary cores were taken for sedimentology and mineralogy study from south to north of Lake Urmia. The clay mineralogy analysis were done by XRD method. The main minerals in the sediments include quartz (over 40%), calcite, feldspars, mica, dolomite and clay minerals. Chlorite and kaolinite were the main clay minerals in the southern coastal plains of Lake Urmia. Distribution of surface samples represents reduction of clay minerals in the sediments from the margin to the center of the basin. This indicate that the percentage of detrital sediments decreases and chemical sediments increase from the margin to the center. Increasing the distance from the edge of the wetland causes it to move away from the source of the sediments. The concentration of water salts in the central part of the basin increases.

The Oligo-Miocene Asmari Formation with main carbonate and evaporate lithology is the most prolific reservoir in the Dezful Embayment, south-west of Iran. Depositional and diagenetic effects on reservoir quality in the sequence stratigraphic framework were carried out on the basis of petrographic investigation, petrophysical logs, and core measurement porosity and permeability data. Petrographic analysis resulted in the identification of 12 microfacies classified in 5 sub-environments including tidal flat, lagoon, barrier, shallow open marine and basin, which indicate deposition in a homoclinal ramp setting. Tidal flat, lagoonal and barrier microfacies are mostly present in the upper and middle parts of the Asmari Formation, while outer ramp microfacies largely developed in the middle part. Anhydrite/calcite cementation, compaction, dolomitization, dissolution, and fracturing are the main diagenetic controlling factors on petrophysical properties. Fracturing, dolomitization, and dissolution are contributed to reservoir quality enhancement, while compaction and cementation had negative effects on reservoir quality. The main controlling factor on their reservoir quality was depositional characteristics and/or a facies-dependent diagenesis. The studied successions are represented by 3 third-order sequences of early Aquitanian, late Aquitanian and early Burdigalian age that largely deposited in the highstand systems tract (HST) stage. The Burdigalian sequence represent best reservoir quality due to further dolomitization and dissolution especially close to the sequence boundary.