مجله پژوهش های دانش زمین
پیاپی 54 (تابستان 1402)

Climate is one of the most fundamental factors in the structure of the planet Earth. Undoubtedly, the biological (including human) and non-biological fields are deeply and widely affected by climatic conditions. Climate change can have many feedbacks and consequences. During the last 30 years, the frequency of some Frein accidents has increased, and it is expected that more hazards related to weather will occur in the future. Due to the increase in climatic extremes and natural hazards in Iran, which is characterized by ecological sensitivity, these events have a significant impact on the state of water resources, agriculture, energy, tourism, and bio-climatic conditions; Therefore, studying this field is an inevitable necessity. The main goal of the current research is to investigate the simulation of average values and minimum, maximum and average daily temperatures of Zanjan based on climate scenarios and using the SDSM model.

The method of carrying out descriptive-analytical research and the method of collecting data is library (documents). SDSM model and climate scenarios (RCP2.6, RCP4.5 and RCP8.5) have been used to simulate temperature variables. The data used includes the average, minimum and maximum daily temperature recorded at the Hamdid Zanjan station during the period of 1961-2021 and the data of the general atmospheric circulation model to simulate climate variables in future periods. In order to obtain the most suitable atmospheric variables for estimating triple temperature profiles, the relationship between dependent variables (minimum, average and maximum daily temperature) with independent atmospheric variables (NCEP) was examined to select independent variables and recalibrate the model for dependent variables. Also, the Markov chain model has been used to investigate the probabilities of Frein events. In order to recalibrate the SDSM model, the observational data of Zanjan station and the data of NCEP National Center for Prediction of Environmental Variables were divided into two periods: 1961-1990 and 1991-2005. The first period was used to calibrate the model.

The simulation results of the three studied temperature variables showed that in all scenarios, they will increase the most in the period of 2082-2100 compared to the values of these variables in the base period (1961-2021). The monthly review of the simulated data and the observed data of the studied variables showed that based on the studied scenarios and the SDSM model, it was determined that from 2022-2100 the minimum temperature will increase by 2 degrees, the maximum and average temperature by 3 degrees. The average minimum and average temperature will increase the most in January and February and the least in October. While the average maximum temperature will increase the most in August and the least in April.

Result shows that all seasons of the year will become warmer, especially the cold seasons of the year. In other words, the cold seasons will be shorter. The number of extreme frequencies observed in all three temperature parameters for the 25th and 75th quartiles is less than the number of simulated extreme temperature events in all three scenarios. The highest number of extreme low frequencies is expected in January and the highest number of extreme high frequencies is expected in July.

The snows of the Alborz mountain range play an important role in providing underground and surface water for the settlements around it and the densely populated Caspian Plain, and the permanent rivers of the northern and southern slopes of Alborz are fed by the snows of the high places of Alborz. Global warming has caused changes in the atmospheric-climatic parameters of Iran; in such a way that temperature and evaporation have increased and precipitation, especially snow, has decreased. These changes, which are considered as independent variables, will cause changes in the dependent variable, which is the snow cover of the high points of the Alborz Mountains. Its consequences can be accelerating the melting of snow, increasing the process of flooding of rivers in the catchment areas of the study area, and the destruction of habitats and settlements downstream. Therefore, the monitoring of Alborz snow area can be used in formulating water management strategies and sustainable development.

In this study, the temporal-spatial variations of the Central Alborz snow cover on a seasonal scale for the years 1985 to 2020 were monitored using Landsat TM, ETM+ and OLI for 1985, 1995, 2005, 2015 and 2020. For each season of the year, an image was prepared that was a combination of 4 satellite images and radiometric and geometric corrections were made on it. SVM algorithm was used to extract the snow cover. The area of snow cover was obtained by transferring the classified map to the ArcGIS.

The results showed that the kappa coefficient for the classified maps was more than 0.91. The average snow covers for winter, autumn, spring and summer were 1.19, 0.47, 0.14 and 0.004 million hectares, respectively. Snow covers have been declining from 1985 to 2020, reaching 1.98 million hectares in 2020 from 1.68 in 1985 to 1.68 in winter. In the autumn, it increased from 0.84 in 1985 to 0.15 million hectares in 2020. In winter and autumn, snow cover in the eastern part of central Alborz has decreased sharply compared to the western part. In the winter of 1985, snow started at an altitude of 1,500 meters, but by 2020 it reached 2,500 meters. In the summer, snow was more than 3,900 meters high in 1985, but peaks more than 4,200 meters in 2015 and 2020. The area of snow cover in Central Alborz has a decreasing trend, which has the highest rate in winter. In order to increase the spatial accuracy of snow, the present research used Landsat series images with 30 meters pixels, and its results are more favorable than the output of MODIS images.

Therefore, the results of this study showed that the accuracy of the support vector machine algorithm is more than 0.91% in the classification of Landsat images, this method can be used to extract snow patches; in such a way that it separated the shadow snow and cloud from the snow and identified the accumulation of snow in the valleys. It can be concluded that using images with spatial resolution of 30 meters and applying classification algorithms for snow extraction is better than using NDSI index and MODIS images. On the other hand, the process of snow cover in central Alborz has been such that during 25 years, the area of snow has decreased from about 0.7 million hectares and a large amount of fresh water storage in Alborz has been lost.

Identification of active tectonics in an area and its effects on the morphology of landforms is one of the topics that has always been of interest to geomorphologists. Waterways are among the features that flow a wide range of landforms. These features are sensitive to lithological or tectonic changes and react quickly to these changes. The riverbed has been affected by these anomalies and the effects of these anomalies can be studied in the longitudinal profile of the river. In other words, waterways are active tectonic markers that give us information about the characteristics of a landform.

The study area is located in the south of the Eastern Alborz Mountains and is known as the Siah-Kuh Heights. This ridge consists of a set of dolomitic and sandstone rocks of Sibzar and Padha Formation and Damghan fault passes along it. The main purpose of this study is to investigate the morphological and tectonic structure of Siah-Kuh using steepness and concavity parameters based on the anomalies of longitudinal profiles of the rivers based on the uplift and subsidence axes. In order to calculate the rate of steepness and concavity of longitudinal profiles, the stream power low formula is used based on the two main parameters of drainage area and slope of river. This formula is based on a logarithmic plot of the slope and drainage area for which the appropriate regression line is determined. In this regression relation, the slope of the line is the concavity parameter and the intercept is steepness parameters.

The extent of the Siah-Kuh heights among a series of young Quaternary sediments at a distance of 4 km from the main mountain front, the structure of the Siah-Kuh is similar to Foreberg forms. Damghan fault in this area has led to the intersection of Quaternary sedimentary strata related to the surrounding alluvial fans and by creating a transtensional position in the form of a set of trapped traps, the Siah-Kuh Foreberg has appeared as a restraining bend on the surface Which has led to the elevation of the central part and the relative subsidence of both sides of this structure. The eastern part of the Siah-Kuh Foreberg appears to have been covered by Neogene and Quaternary sediments. Its remnants have appeared in the form of deep gorges on the surface. One of the rivers flows on the main surface of Foreberg and the other flows in the drained or buried part of Foreberg. Both rivers have several knick points in their flow path, which are taken from the location of faults and lithological differences of the riverbed. The values of the steepness parameter for the main river and the gully show high values so that the value of this parameter is 121.4 for the main river and 119.96 for the gorges. In contrast, the depression parameter rate in both rivers shows very low and even negative values. (Main river: -0.18 and gorges river: -0.92). Since the sharpness parameter is directly related to the tectonic processes; It can be said that the values of this parameter in both rivers indicate the effect of active tectonics at the level of Foreberg.

The studies performed on the study area show that the two factors of active tectonics and lithology have a great impact on the morphological structure of Siah-Kuh Foreberg. Also, factors related to sedimentary flows originating from the uplands of the area have been effective in changing these landforms in the form of burial. Also, the results showed that the use of the method based on longitudinal profile anomalies of the river in the form of steepness and concavity parameters has an effective role in identifying erosion and subsidence axes related to tectonic situation of features in relation to their topographic changes. Slight difference in the amount of steepness parameter in gorges compared to the river on the main surface of Foreberg, especially in the first trends of both rivers, which show high values of steepness parameter with a small difference (1.44), Indicates the existence of an uplift axis in this area, which somewhat confirms the burial of a structure similar to the Siah-Kuh Foreberg under sediments.

Introduction:

Dust storms with visibility of less than 200 meters are dangerous storms for human life and activity. By knowing the behavioral characteristics and how these storms form and spread over the sources of dust production, it is possible to reduce its many damages or adapt to it by creating the necessary infrastructure.

According to the purpose of the research, to investigate the historical trend of the occurrence of severe storms and the synoptic patterns that cause such storms, a statistical period of 33 years (corresponding to the last three solar cycles) was selected. Based on this statistical basis, 16 synoptic stations were selected as sample stations. All codes with visibility less than 200 meters were extracted for all selected stations. The days in which code was reported in at least two observatories with visibility less than 200 meters were selected as a day with a storm. To select synoptic systems, the days when this phenomenon was reported in at least one third of the sample stations were selected as a dust system. In this way, 68 study samples were extracted. These samples were tested using the method of factor analysis and visual inspection to select the dominant patterns.

The highest number of dust storms with visibility less than 200 meters occurs in two turbulent seasons in terms of weather, i. e. winter (593 cases) and autumn (426 cases). In monthly terms, the highest number of dust storms of this type occurred in January (352 cases) and December (236 cases). In terms of historical trends, from the beginning of the period (1987) to 2007, the number of storms has been almost constant. Since 2008, the number of such storms has increased significantly and this process continued until 2012. Since 2012, the number of storms has decreased slightly, but it has not returned to the conditions before 2007. In terms of spatial distribution, the highest number of storms occurred in the cold period of the year, in the eastern stations of the region, on the contrary, in the warm period of the year, the highest number of storms occurred in the western part of the study area.

Two recurring patterns are the main cause of dust storms in the cold period of the year. In the African gyre pattern, the significant northward expansion of this anticyclone ridge and the cold advection of the subpolar latitudes over the western region of Asia creates a severe temperature and pressure gradient in the entire lower and middle layer of the troposphere. Such storms generally start after the end of rain in the west of Iran. In the Sudan low pattern, with the significant expansion of the Sudan low pressure tongue over the western region of Asia and the formation of a deep trough in the middle layers, it causes the instabilities to intensify over the dust sources of Syria and Iraq. Most summer dust storms have followed a general pattern. In these patterns, three low pressure systems, Saudi Arabia, Pakistan and sometimes Lut desert, are the main cause of dust storms in the lower layer (up to the level of 850hpa). The strong winds resulting from this surface instability are the main cause of dust rising from dust sources in the region. Meanwhile, in the middle layers, calm atmosphere generally dominates the western region of Iran.

The result of this research showed that storms with visibility of less than 200 meters are increasing in the western region of Iran. In terms of spatial distribution, the highest number of such storms occurs in the cold period of the year in the eastern part of the region. From a synoptic point of view, dust particles rise from dust sources in Syria and western Iraq and enter the eastern part of the study area along the atmospheric currents of the middle layer of the troposphere. That is, during the cold period of the year, highland areas are affected by severe dust storms. Meanwhile, the western part of the study area is affected by the highest number of dust storms in the hot period of the year. Dust storms this time of the year are not very deep.

The sulphide deposits of stratabound and stratiform are one of the largest sulphide deposits for copper mineralization. by examining and comparing the deposits and mineral signment discovered in the Eocene volcanics with Mantle type deposits in Chile, they concluded that the Manto deposits were formed in the uppermost porphyry andesitic lavas of Eocene Iran and can be considered as a metallogenic unit to explore this type of mineralization. In Iran, Manto type deposits have been reported just in Urumieh -Dokhtar zone, Sanandaj-Sirjan zone and Sabzevar sub-zone. Abari and Rahbari deposits are among the Manto type deposits in the volcanic-intrusive belt, Khaf- Darooneh and the southern part Sabzevar sub-zone. In this research, mineralogy, geochemistry and formation pattern of Abari and Rahbari copper deposit were discussed and investigated.

In this research, 100 thin and polished sections were prepared and studied, and the studies of fluids inclusion were done by preparing and studying 3 double-polished sections from surface samples. In order to identify minerals and complete alteration studies, 6 samples were analyzed by XRD method and for geochemical studies, 22 samples of ore and volcanic-sedimentary rocks were analyzed by XRF and ICP-MS methods in Binalud deposits Laboratory and Iran mineral processing Research Center.

According to the diagenetic-epigenetic model, the stages of mineralization and formation processes can be described in three stages: the first stage: initial diagenesis, the second stage: the burial diagenesis stage, and the third stage: the uplift stage (hydrothermal activities). Initial diagenesis stage: after extensive volcanic activities, during the diagenesis stage, in this stage, seawater sulfate regenerating bacteria were present in the environment, and their activity has caused regeneration conditions in the basin. As a result, the resulting sulfur with the available iron causes the deposition of pyrite in the form of scattered grains and fills the empty spaces in the rock background. Secondary diagenesis stage: from the stage of diagenesis onwards, burial occurs as a result of the deposition of newer sediments on them. the hydrothermal fluid carries the copper released from the conversion of iron hydroxide minerals into iron oxides, as well as the copper released in the network of feldspar minerals in the transformed volcanic units due to the high environment temperature and circulation in the volcanic and pyroclastic units and then turning up in the rock units, it reached the pyroclastic unit with high porosity and permeability, and chalcocite and chalcopyrite minerals were formed in the burial diagenesis stage. upwelling Stage (hydrothermal activities): at the end of the burial process and with the beginning of the uplift of the area and faulting, the open spaces increase by Darooneh and Binalood faults, which ultimately causes the activity and concentration of sulfide and copper oxide mineralization will start again along the faults, cracks, and even the empty spaces of the pyroclastic units.

The Eocene volcanic rocks of the magmatic belt in the north of the structural zone of central Iran are the host of Abari and Rahbari copper deposits with the dominant composition of andesite and basaltic andesite. The effective factors copper mineralization in the study areas including: 1) The lithology of host rocks, 2) structural controls, 3) hydrothermal fluids and 4) The presence of intrusive rocks at depth and basaltic dykes. The controllers play a significant role in the transfer of hydrothermal fluids and their accumulation and deposition. Mineralization is formed in three stages: initial diagenesis, burial diagenesis and uplift stage (hydrothermal activities). The dispersed pyrites is source of sulfur in reducing conditions (resulting from the activity of seawater sulfate reducing bacteria). Based on the studies of intermediate fluid loads, the processes of dilution with surface fluids, mixing with isothermal fluid, cooling and pressure reduction can be considered responsible for the changes created in the fluid. So that mineralization in the Abri and Rahbari area is epigenetic, strata bound that is similar to the manto type copper deposits.

The Cretaceous deposits of Golbaf region are part of the Rhine-Guk-Khana Khatun zone in the stratigraphic-structural belt of Rafsanjan (Dimitrijevic and Djokovic, 1973). In this belt, Cretaceous deposits are divided into shallow to deep facies, and the most complete Cretaceous deposits can be found in the Rhine-Guk-Khan Khatun area (Dimitrijevic, 1973). The studied sedimentary sequence is exposed in the south of Golbaf and southeast of Kerman and its thickness is 147 meters. The age of these sediments is Upper Cretaceous (Coniacian-Santonian). These sediments contain clastic deposits that are gradually and with the same slope on the Lower Cretaceous and Neogene, and the upper boundary of this section is in the form of marl limestone related to MaisTrichtian facies. This section has a lithological sequence of columnar silt, silty sandstone, and shale, which contain fossils and species that have been identified in the debris layers of this section. These fossils are mostly creeping-nutritional or nutritional traces. These fossils are found in shallow to turbidity marine environments, which are well preserved and varied, and their most abundance can be seen in the middle part of this section. In this article, an attempt was made to systematically identify the existing fossils and discuss and examine their behavioral patterns.

This study includes two stages of field and laboratory operations. In the field operation, after identifying the intended cut and determining the boundaries as well as the beginning and end of the desired cut, the thickness of each layer was measured and examined.  The required information was noted down, and if sampling was done, fossils were taken from the sediments. In the laboratory, after photographing each sample, the characteristics of each fossil, such as shape, size, dimensions and type of preservation in relation to the level of layering, decorations and various components, were identified (Miller, 2007; Seilacher, 2007). Then the trace fossils were classified based on the behavioral status first presented by (Seilacher, 1964) and discussed by (Bromley, 1996) and finally the fossil systematics was written completely.

Trace fossils are biological constructions in sedimentary environments that are formed by organisms in soft to hard sediments. Trace fossils are biological constructions in sedimentary environments that are formed by organisms in soft to hard sediments. Trace fossils are biological constructions in sedimentary environments that are formed by organisms in soft to hard sediments. Turbidites are generally found as flysch deposits and are considered as deep basin rock facies. These sediments, in expanded patterns, Boma include a series of diverse clastic-mudstone facies (Pickering et al, 1989). On the other hand, trace fossils have complex geometrical shapes that are usually observed with marine and deep pelagic sediments. Since the trace fossils in Golbaf region are widespread and abundant, therefore, in order to achieve turbidite sedimentary environments, based on the data of Archeology It is necessary to combine the archeology data with sedimentological data and structural elements. The rock facies of the studied sequence include The facies are siltstone, silty sandstone, and Chile. In these beds, the amount of sedimentation is low to high. According to the archeological data, diversity and abundance of fossils in the studied sedimentary sequence, on the surface of silty sandstone and siltstone layers, it can be concluded that most of the fossils are in the form of molds on their lower surface, in other words, the activity of animals has an effect on They are concentrated on the upper surface and have been molded by silty sandstone and siltstone sediments after deposition. Therefore, most of the fossils were formed in the middle parts after the occurrence of turbulent currents and in a relatively calm environment.

Upper Cretaceous flysch deposits in Golbaf area have a good thickness and ichnofossils in this section have a very high diversity and abundance.Ethnological and sedimentology studies on the sediments of the studied area indicate calm conditions in the bed of the basin. It seems that the availability of environmental conditions such as bed oxygen, amount of organic matter in sediments, time fluctuations, textural composition of sediments, sedimentation rate, abundance of biological communities and their distribution have caused the abundance of effectors.According to the type, frequency and spread of fossils in the studied sequence, it can be concluded that a thickness of the Set bar sequence in the south of Golbaf is in suitable conditions for creating fossils.

Northwest-southeast structural trend, is one of the dominant structural trends in the east of Iran. Dextral N-S striking Nehbandan fault system, is located between Sistan and Lut structural zones. The tectonic model and growth of northwest-southeast trends in the east of Iran will be introduced by deformation analysis in Hematabad region.

The rock units of the Sistan subzone include: Cretaceous ophiolitic and metamorphic units and flysch-pyroclastic units. Hematabad region includes: ophiolitic units extending in the northwest-southeast direction, volcanic rocks, and sandstone, shale, limestone units with metamorphism ranging from slate, phyllite to schist.The northwest plunging folds in the tertiary’s shale and sandstone units have steep forelimb on the southwest side, which indicates the southwest tectonic vergence. From northeast to southwest, ophiolite outcrops, folded cretaceous and tertiary sediments can be observed, which can be a reason for the growth of structures from northeast to southwest. North-south and northwest-southeast striking fault zones are dominated in this region. Geometric and kinematic analysis of mentioned fault zones, indicates the main axis of compression in the region has an average trend of N25E. The shear component is dominant in the north-south fault zones and the compressive component is dominant in the northwest-southeast ones. According to the geometrical analysis of the faults and their mechanisms, folds and the rock units outcrop, the activity of the faults in the northeastern part can be considered as older (earlier) faults. Therefore, they are a series of thrust faults that are growing from the northeast to the southwest.

Based on geomorphological evidences such as displaced rivers, shutter ridges and fault scarps in Hematabad region, fault zones migrate to the southwest. In addition, tectonic activity decreases from southeast toward the northwest. By asessement of the fault and folds, outcrop of the rock units and the morphotectonic features, the following structural model can be presented:The first stage: by NE component of compressive stress, the NW-SE striking Hematabad fault zone in which the pressure component is dominant, ophiolitic units was exposed.The second stage: a new fault the same as Hemmatabad fault zone (NW-SE) has been formed in its southwestern part with a reverse right-lateral mechanism. With the continuation of mentioned deformation, folding of Cretaceous and Paleocene-Eocene sedimentary rocks and displacement in rivers occurred.Third stage: Shutter ridges develop with the formation of new faults. In this model, the growth of the structures has been done from the northeast to the southwest.NE component of compressive stress, has caused folds with a northwest-southeast axial trace in the region. In north-south striking faults, the strike-slip component is dominant, but in northwest-southeast striking faults (such as Hematabad fault zone), the reverse component is dominant.The morphotectonic evidences indicate that the uplift of fault scarps is decreasing from the northeast to the southwest, and the deflection of rivers is decreasing from the southeast to the northwest. Therefore, the tectonic activity in the southeastern part is more than the northwestern part in this region.

The growth of structures in this area continues with the creation of NW-SE striking fault zones from the northeast to the southwest, which indicates the structural growth in the northwest-southeast trends in the east of Iran.

Baba-Ali and Galali deposits are located in 30 and 60 km northwest of Hamedan in northwest part of the Sanandaj-Sirjan zone. The host rocks of these deposits are metavolcano-sedimentary successions of Songhor series in Permo-Triassic age. Stratigraphic position of ore horizons, geometry of orebodies, ore structures and textures in different scales and paragenetic sequence of minerals all show close genetic relation between iron ore and the metavolcanosedimentary and subvolcanic rocks. The host rocks in the area are felsic to intermediate metavolcanic rocks, more than lava and rhyolitic tuffs with interculations of carbonate and metatuff-sandstones. Field observations and petrography show that emplacement of plutons and subvolcanic rock units with composition of gabbrodiorite, quartzmonzodiorite, granodiorite, syenite, syenogranite and granite in these successions caused deformation and metamorphism of ore and country rocks.

In this research, 56 polished sections were prepared from iron ore of Baba Ali and Galali deposits, and the mineralogical characteristics and texture of the mineral in relation to gangue minerals were carefully studied using a reflected light mineralogical microscope. In order to determine the origin of ore-rich fluid, studies of fluid inclusions have been carried out on 6 double polished sections in the research laboratory of Tarbiat Modares University. Also, 29 samples of separated phases of sulphide, oxide-silicate and carbonate minerals from ore and gangue minerals of Baba Ali and Galali iron deposits have been analyzed for stable isotope analysis in Queen's University Isotope Research Laboratory in Canada.

From field evidences, fluid inclusions data, as well as stable isotope analysis in this study, emplacement of plutons and subvolcanic rock units with composition of gabbrodiorite, quartzmonzodiorite, granodiorite, syenite, syenogranite and granite in these successions caused deformation and metamorphism of ore and country rocks. Fluid inclusion studies within the quartz crystals indicate that main salinity varies between 12±5 and 9±5 wt.% NaCl equivalent in Baba-Ali and Galali deposits respectively. Homogenization temperature for Baba-Ali and Galali deposits are 226±5 and 220±5 oC respectively. Occurrence of dynamothermal regional metamorphism in these deposits typically involves a lengthy period of time, during which there was a tendency toward isotopic homogenization specifically in O (3 to 10.5 ‰) and H (-10 to -35 ‰) stable isotopes and show the role of metamorphic waters in mineralization process. Measurement of δ34S (CDT) in first generation of pyrite is higher than another one, so these data confirm the volcano-sedimentary origin of primary iron mineralization.

Field observations, structure and texture, host rock, intercualation, geochemistry, alterations, studies of fluid inclusion and stable isotopes in Baba Ali and Galali deposits show that these deposits are volcanic-sedimentary iron deposits. Since most of these mineralizations are located in metamorphosed volcanic-sedimentary units, these rock groups are of great importance in terms of iron exploration. Investigating these stone units in the region and generalizing the evidence obtained from them to similar areas in Sanandaj-Sirjan zone can lead to the identification of this type of iron deposits.

During the Late Carboniferous-Early-Permian, glaciers covered a large part of Gondwana (Aghanbati, 2009). In the Late Asselian-Early Sakmarian, due to the increase in temperature, glaciers have retreated from all of Gondwana (Aghanbati, 2010) and after that progress has occurred continuously at the beginning of the Permian. during the Early Permian, mostly mixed siliceous sediments Carbonate-debris of Droud formation was mainly deposited in continental and intermediate environment, with increasing depth gradually in the late Permian, Middle Permian and early Permian of Ruteh Formation with carbonate facies and then in the late Permian. Ruteh formation was identified and introduced for the first time by Assereto (Assereto, 1963) in the valley of Ruteh village in the northeast of Tehran. in this study of Ruteh formation based on detailed lithological characteristics (macroscopic and microscopic) and identification of benthic foraminifera in a stratigraphic section 30 km south of Amol in central Alborz, in terms of rocks Stratigraphy and biostratigraphy have been investigated.

After preparing microscopic thin-sections from all samples, the sections were stained with red alizarin solution according to Dickson's method (Dickson, 1965) to distinguish calcite from dolomite and then studied under a microscope to identify microfossils. After the identification of microfossils, the bio zonation of the sediments of Ruteh Formation was started based on the biozone of Leven and Okay (1996) belonging to the West of Paleo-tethys.

In the biostratigraphic studies of the Ruteh formation in the stratigraphic section of South Amol, whereas 31 genera and 57 species of benthic foraminifera were identified, three local biozones were identified and introduced as described below. Small Foraminifera and Fusulinids together with green and red algae constitute the most important microfossils of Ruteh formation. Neoendothyra bronnimanni-Neoendothyra reicheli assemblage zone This biozone, which is an accumulation type, is defined based on the existing symbiotic community in it, and it occupies 72 meters from the base of the Ruteh formation after the erosion boundary between the Dorud and Ruteh formations. The lower boundary of this biozone is determined by the beginning of the symbiotic complex below and its upper boundary by the appearance of the indicator foraminifera of Midian stage, such as Chusenella sinensis and Codonofusiella erki. The age of this biozone based on its identified species such as various speciesof Neoendothyra and the comparison of this cumulative biozone with Khachik Julfa layers and other areas of the Tethys region such as Afghanistan indicates the late Murgabian age for this zone. Chusenella sinensis - Codonofusiella erki Pachyphloia assemblage zone This cumulative biozone includes 282 meters of the thickness of Ruteh formation after biozone 1. Its lower boundary is determined based on the emergence of the midian Chusenella sinensis, and the upper boundary of this biozone is determined by the emergence of the foraminifera such as Dagmarita chanakchiensis and Paraglobivalvulina mira. The age of this formation is based on the presence of foraminifera such as Chusenella sinensis and the comparison of this accumulation biozone with midian foraminifera of Khuf Formation Paraglobivalvulina mira - Dagmarita chanakchiensis assemblage zone This biozone, which is defined based on the following symbiotic complex, inhabits 288 meters from the top of the Ruteh Formation in the studied section. Based on the symbiont complex, the age of this biozone has been identified as the early Julfian. However, an indicator species such as Pachyphloia iranica is accepted by most of the experts as the indicator species of Julfian stage (Bozorgnia, 1973).

The following results have been obtained in the Lithostratigraphic and biostratigraphic studies of the Ruteh formation in the section of the mansion:The thickness of the sediments of Ruteh formation in this section is 642 meters and in terms of lithology, it mainly consists of thick to medium and thin dark limestone along with dolomitic limestone, limy dolomite, sandy limestone, cherty limestone, shale and sandstone.The lower boundary of Ruteh Formation with Dorud Formation is disconformity, so that the limestones at the base of Ruteh Formation are placed on the eroded surface of the sandstones at the top of Dorud Formation. Its upper border is also with the Nesen Formation, which is discontinuous and eroded along with a laterite horizon. Based on the above biological zones and the set of fossils identified in them, the age of the Late Murgabin-Early Julfian Ruteh formation was determined.