Document Type : Original Research Paper
Authors
1 Ph.D. Student, Department of Earth Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 Associate Professor, Research Institute for Earth Sciences, Geological Survey of Iran (GSI), Tehran, Iran
3 Assistant professor, Department of Earth Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
4 Ph.D., Research Scientist, French National Center for Scientific Research (CNRS), Paris, France
5 Ph.D., Management of Geohazards, Engineering and Environmental Geology, Geological Survey of Iran (GSI), Tehran, Iran
Abstract
Lake Urmia is one of the largest salt supersaturated lakes in the world that is located in northwestern Iran. Many wetlands are located around of Lake Urmia, especially in the southern part of the lake. Wetlands are important as a platform for recording environmental and climatic events. The subject of this research is studying sedimentology and statistical parameters of sedimentology in the analysis of different sedimentary environments in the sediments of southern wetlands around Lake Urmia, including Kani Barazan and Solduz wetlands. The purpose of this study is reconstructing the fluctuations of the water table of Lake Urmia and its effect on wetland areas in the Holocene period. For this purpose, sedimentary cores with maximum depth of 12 meters and total depth of about 200 meters using a handi auger and 8 hole cores by a vibra corer were collected and examined. Sedimentary facies were identified and separated based on texture and sediment structure, composition of destructive sediments and organic matter, color, presence of plant remnant and shell residues and other macroscopic components. Sampling was performed based on changes in the type of sediments and sedimentary facies. 150 sediment samples were separated for grain size analysis. The samples were analyzed using two methods, wet sieving and particles smaller than sand (silt and clay) by laser device (Laser particle Sizer Analysette). Statistical parameters of sedimentology were calculated using Sedilizer software and were analyzed by SPSS software. Two samples of plant remnant were dated by C14-AMS isotope method. The results indicate that there are 8 facies, belonging to 3 sedimentary environments of lake, wetland and alluvial. The dating results show the average sedimentation rate in the southern part of Lake Urmia is about 0.5 mm per year. However, sedimentation rates vary in different sediment depths. According to the analysis of different cores, the reconstruction of the paleogeography of the south of Lake Urmia and it`s extention had been done in the last 20,000 years. This study shows that in the late quaternary Lake Urmia has expanded to the beginning of the current Siminehrud. At the late Pleistocene and the early Holocene, the coastline regression in the southern part and the alluvial sediments of the Zarrinehrood and Siminehrood rivers occurred in the south of the region. The late Holocene was associated with decreasing water table, slightly dry conditions (around 4000 years ago) and the expansion of marginal playa. The situation in the region has been permanent for about 2000 years.
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Plateau): Implications for Neogene evolution of the East Asian winter monsoon. Geological Society of
America Bulletin, 122: 843-854.
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