فهرست مطالب zaniar amiri

During the Quaternary period mid to high-latitude areas were affected by loess deposition. In Iran's northern and northeastern regions, significant loess deposits are prevalent and distributed throughout the Iranian Loess Plateau and along the northern foothills of the Alborz Mountains. Intercalated within these loess deposits are paleosols, formed during warm and moist climatic conditions (interglacial period). These paleosols offer an opportunity to study the climatic and environmental changes that occurred during the Quaternary period. Understanding the relationship between loess deposition and paleosol formation can offer significant insights into the mechanisms that drive changes in global climate and how they affect the Earth's geology and ecosystems. Studies have shown that loess sediments and loess-derived soils contain different concentrations of iron minerals such as hematite, iron oxyhydroxide, and goethite. These minerals are highly sensitive to environmental changes, and evaluating the changes of these minerals in loess-paleosol sequences can be a valuable indicator for studying paleoenvironmental changes. The two main minerals that cause color and magnetic susceptibility changes in loess-paleosol sequences are goethite and hematite. Therefore, the assessment of loess-paleosol sequences from the aspect of magnetic and colorimetric parameters provides the possibility to identify paleoenvironmental and climatic changes. The main goal of this research is to investigate the changes in iron oxides in the loess-paleosol sequence in the east of Golestan province using colorimetric techniques and temperature-dependent magnetic susceptibility in order to provide enough information for reconstructing the paleoclimatic conditions during the formation of paleosols.

Sampling was performed from the loess-paleosol sequence in the eastern Golestan province, for each loess and paleosol horizon. Initial colorimetric and magnetic susceptibility measurements were carried out respectively for 1345 and 24 samples at LIAG Institute in Germany. Color measurements were carried out with a spectrophotometer machine that covered the visible light range. The temperature magnetic susceptibility was carried out using in the 20–700°Ctemperature range in an argon atmosphere to minimize oxidation.

According to the results of this study, we can mention the identification of iron minerals in loess and paleosol samples using colorimetric analysis. Iron minerals such as hematite, goethite, and maghemite can be detected at wavelengths 565, 435, and 595 nm, respectively. Colorimetric results showed that the ratio of hematite to goethite of paleosols has increased compared to loess sediments in the study area, which indicates the increase in precipetation and soil moisture during the interglacial period. The heating curve (temperature-dependent magnetic susceptibility) of loess samples at 560-590 degrees Celsius showed a sharp decrease due to magnetite minerals in these samples. At the same time, this happens in paleosols at a temperature of 300-350 degrees Celsius, which is due to the loss of the maghemite mineral formed during the interglacial period. The results showed that the decrease in the heating curve in paleosols indicates the increase in the intensity of soil-forming processes.

The results of this study showed that iron minerals such as magnetite, maghemite, hematite, and goethite in loess and paleosols play an important role in magnetic properties and soil color. Also, the increase in the presence of hematite and maghemite in paleosols indicates the increase in the intensity of soil formation processes and humidity during the formation of paleosols. The results of this research showed that the colorimetric technique, along with temperature-dependent magnetic susceptibility, can be one of the fast and accurate methods in studying and identifying paleosols.

The study of loess sediments and loess-derived soils, which cover approximately 10% of the Earth's surface, is of considerable importance because of their potential to provide information on the paleoenvironment, particularly during the Quaternary. The northeastern region of Iran, with its unique climatic archive, is of significant importance as a repository of Quaternary period deposits, attracting much attention from Iranian and international scientists in recent decades. Considering that soil forms in response to interactions among the lithosphere, hydrosphere, and atmosphere, it potentially contains physical, biological, and chemical environmental information at the time of its formation. The process of becoming loess sediments into paleosol depends on various factors such as vegetation, weather, topography, microbial activity, and time, so paleosols have the potential to restore the paleoenvironment by maintaining the effect of these factors. Therefore, studying soils derived from loess can enhance our knowledge and understanding of past climatic conditions in the region and the world. Studying undistributed soils using microscopic techniques can provide valuable information for understanding the environmental and climatic conditions during the formation of derived soils from loess (paleosols). One of the quantitative methods for studying micromorphology samples is the use of indices such as MISECA, which indicate the degree of paleosol evolution. By using this index, we can have an approximate estimation of paleoprecipetation. The main aim of this research is to reconstruct the precipitation amount during the formation of late Pleistocene paleosols in the eastern part of Golestan province, using micromorphological studies.

In order to conduct this research, after field visits, a profile of approximately 55 meters was excavated to examine the identified loess-palaeosol sequences. Then, undisturbed samples were obtained from each horizon to prepare thin sections, and the samples were impregnated under vacuum conditions using a combination of resin, acetone, and catalyst. After the samples hardened, a thin section was cut from them and affixed to a glass slide. The thin sections were then polished using sandpaper until a thickness of 30 microns was achieved. The prepared thin sections were studied using a polarizing microscope.

Micromorphological analysis of the samples revealed that the presence of horizons rich in calcium carbonate and clay in well-developed paleosols has a significant relationship with increased precipitation.  Micromorphological studies showed that the coarse to fine (C/F) relative distributed results showed that the amount of it in loess horizons and weakly developed paleosols are 4/6 or 3/7 but this ratio in moderately and well-developed paleosols become smaller in comparison with loess horizons, indicating the weathering and leaching of primary minerals in loess sediments and their transformation into secondary minerals in paleosols. Furthermore, with increasing paleosol evolution, the microstructure of the samples changed from massive to subangular blocky and then to angular blocky. Therefore, the results of examined microstructure in the samples showed that it can be one of the important factors for identifying paleosols from loess horizons and paleoenvironment conditions. Based on the data obtained from the MISECA index, the degree of paleosol development ranged from weakly developed (MISECA index was smaller than 8) to well developed (MISECA index was bigger than 16). The estimated paleoprecipitation amount using this index showed that paleosols with weak development formed under climatic conditions with precipitation less than 500 mm per year, while paleosols with moderate and well developed formed under climatic conditions with average precipitation of 500 to 800 mm per year and more than 800 mm per year, respectively.

Considering that soils are formed as a result of interactions between the lithosphere, hydrosphere, and atmosphere, they potentially contain physical, biological, and chemical information about past environmental conditions. Therefore, by studying the Late Pleistocene loess-paleosol sequences in Golestan province, it is possible to reconstruct past climatic changes in northeastern Iran. The micromorphological investigation of the loess-paleosol sequence under study showed that the processes of transfer and deposition of clay and secondary calcium carbonate and the subsequent creation of horizons rich in clay and secondary calcium carbonate are among the most important pedogenic processes in well-developed soils. Micromorphology can be a useful tool for investigating the paleoclimate and paleoenvironments conditions during the formation time of paleosols. The results showed that the use of the MISECA index can be a valid and logical method for evaluating the degree of paleosol development.

In the studies of water resources sustainability and development planning in the watersheds, ecological values and continuance life cycle of the river ecosystems should be recognized. The natural flow regime, plays a key role in protecting river habitat components and biodiversity formation. For this purpose, in the present study, with step-by-step measuring and calculating the environmental flow of the Zarin_Gol River in Golestan province and using hydrological methods of Tennant, Tessman, Texas and Ecodeficit , the sustainable ecological conditions were studied and target fish habitat analysis with Ecohydraulic Habitat Physical Simulation Model (PHABSIM) compared. The results showed that by performing hydraulic simulation and analysis of habitat discharge-physics time series using curves Suitability Index, range of flow regime required to provide habitat ecological potential Paracobitis hicanica was between 0.85 to 4.42 m3/s, with Mean Annual Flow of 1.73 m3/s (equivalent 80 percent of natural stream of the river), It should have existed in inside the Zarin_Gol River. The flexibility and effectivenessof the flow regime of the hydrological methods of Tannant, Texas and Tessman were not sufficient for the conservation and restoration of the studied river habitat. But Ecodeficit method, by providing environmentally friendly flow statistics, while providing in-stream needs, well describes the hydrological changes of the Zarin_Gol River flow regime. According to the results, the ecological optimum flow regime assigned by habitat simulation method is able to protect the natural flow regime for preserving the ecological values of the river, Proper performance of river habitats and preservation of morphological conditions of river bed. The methods used in this study and the obtained results, provide a valuable reference for water resources planning and ecosystem protection in rivers.

Along with the climate, Soil is an essential natural resource. Although soil studies in Iran have been started more than 50 years ago, the soil map of the country has not been fully prepared yet, and only 20-25% of the lands have been mapped already. Many soil maps of Iran need to be updated, but the common methods in soil mapping are costly and time-consuming. Hence, using data obtained from remote sensing is trending nowadays. These data possess a great importance as a proper approach for preparation of various maps due to timely presentation of information, variety in type, being digitized and possibility of digital processing. Classification is one of the useful methods of obtaining data from remote sensing images which allows the user to generate various types of information such as different maps. Different regions of Golestan province are covered with loessial sediments. Recent studies in loess plateau of Golestan province show that these loesses possess useful information about climate change and landscape evolution in quaternary period. The aims of the present study was mapping different lithologic units in loess plateau of eastern Golestan using remote sensing technique and evaluating the efficiency of using remote sensing images to identify and prepare the distribution map of different lithology units in the study area.

Loess plateau of Golestan province which is located at the north of Alborz Mountains and western region of Qopeh-dagh Mountains possesses an area equal to 250000 hectares; the height of the mentioned loess plateau is in the range of 45 m to 700 m from sea level. In this study, about 40 km2 of western part of Golestan loess plateau is selected as the study area located near Aghband village, 60 km from Gonbad city. In the following study, distribution map of different lithology units using the data from Landsat 8 and Sentinel 2 satellites was performed via classification of support vector machine, maximum likelihood and photomorphic image analysis methods in GIS software interface by Sentinel-2A (RGB band  No. 2,3, 4) and Landsat8-OLI (band  No. 2,3, 4). After preparing distribution map of different lithology units, their accuracy was evaluated via confusion matrix, The produced maps were evaluated by 607 ground truth points obtained by field survey and Google Earth and their overall accuracies and kappa coefficients were calculated.

Field observations revealed four types of lithology units including loess, loess-paleosol of early Pleistocene, marl and limestone. Each of these lithology types had specific colors and could be identified by color difference in true color composite bands of satellite data and Google Earth images. After the lithology units were digitally classified via the maximum likelihood and support vector machine methods, their distribution maps were prepared and evaluated. Classification of Sentinel 2 images via support vector machine and maximum likelihood methods led to a accuracy of 89.45% and 87.7%, respectively, whereas these values for Landsat were 85.17% and 81.87%.

Each lithology of Golestan loess plateau had a specific color of its own; color of loesses are yellow and yellowish, marls have different colors including blue and green and colors between them, color of lime-stone are white and milky and color of loess-paleosols are red.The results associated with the comparison of overall accuracy and Kappa coefficient of the classified images indicate that although both algorithms of support vector machine and maximum likelihood which are utilized for digital classification had high overall accuracy and Kappa coefficient, superiority of support vector machine compared to maximum likelihood method is obvious in both images utilized in the present study. However, on the other hand, a higher accuracy may be observed in the images taken by Sentinel 2 due to smaller pixel size. Thus, it may be concluded that support vector machine method not only has performed more capably in detection of different lithologies, but also changing the source of the satellite images has no impact on the efficiency of this method. Noting that one of the objectives of the study was evaluating the efficiency of using remote sensing technique to identify and prepare the distribution map of different lithology units in the study area, it was concluded that utilizing remote sensing techniques in the studied region may be feasible along with the other mapping methods.