باز سازی برف مرزهای دائمی کواترنر پایانی در در ارتفاعات گرین در زاگرس ایران (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
بازسازی برف مرزهای دیرینه در مناطق کوهستانی ایران یکی از راهکارهای مهم جهت بررسی تحولات ژئومورفولوژی اقلیمی گذشته می باشد. در این میان شناسایی دقیق آثار یخچالی و حدود گسترش آنها در نواحی کوهستانی ایران بهترین کلید برای مرزبندی های مورفوکلیماتیک و مورفودینامیک به شمار می رود. هدف اصلی این پژوهش، بازسازی ارتفاع مرز برف های (ELA) کواترنر پایانی در ارتفاعات گرین واقع در زاگرس میانی است. برای بازسازی ELA، از پایگاه رقومی داده ها، تکنیک های ژئوماتیک، بازدیدهای مکرر میدانی و شواهد ژئومورفیک یخچالی از جمله، مورن های پایانی استفاده شده است. برای تعیین ارتفاع مورن ها و تعیین موقعیت آنها از دستگاه GPS استفاده گردید و با استفاده از روش های هوفر، لویس و کف سیرک پورتر محاسبات بازسازی انجام شده است. پس از تهیه لایه های مختلف مورد نیاز، در نهایت نقشه ژئومورفولوژی منطقه ترسیم و مکان دقیق مورن ها بر روی آن مشخص گردید. نتایج نشان می دهد که بر اساس آمار اقلیمی میزان ELA زمان حال حاضر در ارتفاع 4577 متری بازسازی شده است. ارتفاع میانگین مجموع مرز برف های واقع در دامنه های شمالی ارتفاعات گرین با روش هوفر و لویز به ترتیب 2531 متر و 2739 متر برآورد گردید. همچنین ارتفاع میانگین مجموع مرز برف های واقع در دامنه های جنوبی این ارتفاعات با روش هوفر و لویز به ترتیب 2795 متر و 2847 متر برآورد گردید. لازم به یاداوری است بر اساس روش کف سیرک پورتر ELA در ارتفاعات گرین در ارتفاع 2780 متری قرار دارد. به طور کلی در استیلای دوره های سرد کواترنری دامنه های شمالی ارتفاعات گرین از شدت یخچال زایی بیشتری برخوردار بوده است و غنی از شواهد ژئومورفیک یخچالی از جمله یخرفت ها و سیرک های یخچالی می باشد.ELA Reconstruction of late Quaternary in the Green Mountain in Zagros, Iran
Extended AbstractIntroductionPerhaps one of the most controversial topics in geomorphology is the debates related to the Quaternary climate changes and the legacies of these changes. Iran has attracted the attention of many researchers due to its great diversity in its geomorphological environments and the widespread nature of these forms. Investigating the Quaternary climatic changes and its climatic legacies is one of the most interesting topics in Iran's geomorphology. In the meantime, the investigation of glacial effects and the extent of their expansion in the mountainous regions of Iran is considered the most important for morphoclimatic and morphodynamic demarcations. Quaternary climatic changes have played a special role in the current landforms of Iran. The change of the snow territory of the permanent boundaries in the Quaternary is one of the results of these developments. MethodologyUsing frequent field visits, the end moraines along the main valleys were identified and their height was measured using GPS. To prepare the geomorphological map, first, using the Global Mapper 18 software, the study area was cut from the DEM map with an accuracy of 10 meters (obtained from the Aster satellite). Then, a bright shadow map, a geological map with a scale of 1:100,000, a slope map, a slope direction map and degree curves were made. In order to determine the exact boundaries of the sub-glacial basins, the hydrological map of the studied area was made based on Staller's classification from the DEM map. Using Arc Gis 10.5 and Portable Basemap Server V3.1 software, 1/50000 topographic maps and layers created with Google Earth satellite images were created and a combined map was created. The geomorphology map of the area was drawn using Arc Gis 10.5 software. Then, by using terminal glacial moraines, the height of the snow line of the permanent border has been reconstructed using the Lewis, Hofer method and the height of the Cirque Porter floor. Result and discussionAccording to the figure above and the linear relationship obtained between the average annual temperature and the height of ELA meteorological stations, it was calculated to be 4577 meters in the study area.According to the height of the final moraines in Gachal Valley and based on the Lewis method, the lowest ELA is 2700 meters and the highest is at 2898 meters. According to Hofer's method, the lowest ELA is at the height of 2610 meters and the highest is at the height of 2808 meters. According to the height of the final moraines in Taznab Valley and based on the Lewis method, the lowest ELA is 2636 meters and the highest is at 2687 meters. According to Hofer's method, the lowest ELA is at the height of 2511 meters and the highest is at the height of 2562 meters. According to the height of the final moraines in Gamasiab Valley and based on the Lewis method, the lowest ELA is 2752 meters and the highest is at 2884 meters. According to Hofer's method, the lowest ELA is at the height of 2673 meters and the highest is at the height of 2806 meters. According to the geomorphic evidence and the height of the terminal moraines in the sub-basin of Sohran glacier and according to the Lewis method, the highest ELA in this sub-basin is located at an altitude of 3153 meters. According to Hofer's method, ELA is located at an altitude of 3097 meters. According to the geomorphic evidence and the height of the terminal moraines in the Venai sub-basin and based on the Lewis method, the lowest ELA in this sub-basin is 2876 meters and the highest is 3196 meters. According to Hofer's method, the lowest ELA in this sub-basin is at an altitude of 2791 meters and the highest is at an altitude of 3119 meters. According to the geomorphic evidence and the height of the terminal moraines in the collider sub-basin and based on the Lewis method, the lowest ELA in this sub-basin is 2814 meters and the highest is 2854 meters. According to the geomorphic evidence and the height of the terminal moraines in the sub-basin of Ab Sarda glacier and according to the Lewis method, the lowest ELA in this sub-basin is 3036 meters and the highest is 3146 meters. According to Hofer's method, the lowest ELA in this sub-basin is at an altitude of 2946 meters and the highest is at an altitude of 3053 meters. According to the geomorphic evidence and the height of the terminal moraines in the Vorkhash sub-basin and based on the Lewis method, the highest ELA in this sub-basin is 2817 meters. According to Hofer'smethod, the highest amount of ELA in this sub-basin is located at an altitude of 2786 meters. According to the Lewis method, the lowest ELA in this sub-basin is 2722 meters and the highest is at 3040 meters. According to Hofer's method, the lowest ELA in this sub-basin is at an altitude of 2652 meters and the highest is at an altitude of 2970 meters.ConclusionThe calculation results of the reconstruction of the height of the past snow border based on the lowest number of the end moraines and the application of Hofer and Lewis method in the selected basins of the northern slopes of the Green Heights are as flows: in Gachal basin using the Hofer method 2610 meters and Lewis method 2700 meters, in Taznab basin using Hofer method 2511 meters and Lewis method 2636 meters, in Gamasiab basin using Hofer method 2673 meters and Lewis method 2752 meters, in Sohran basin using Hofer method 2764 meters and the Lewis method 2820 meters, in the Venai basin using the Hofer method 2100 meters and the Lewis method 2791 meters, in the Collider basin using the Hofer method 2798 meters and the Lewis method 2814 meters. Also, the average height of the total snow border located in the northern slopes was estimated to be 2531 meters and 2739 meters, respectively, by Hofer and Lewis methods. The results of calculations in the selected basins of the southern slopes of Green are: in Absardeh basin using Hofer method 2946 meters and Lewis method 3036 meters, in Warkhash basin using Hofer method 2786 meters and Lewis method 2817 meters and in Kohman basin 2652 meters were estimated using the Hofer method and 2847 meters using the Lewis method. The average height of the total snow border located on the southern slopes of these heights is estimated to be 2795 meters and 2847 meters, respectively, by Hofer and Lewis method. FundingThere is no funding support. Authors’ ContributionAll of the authors approved the content of the manuscript and agreed on all aspects of the work. Conflict of InterestAuthors declared no conflict of interest. AcknowledgmentsWe are grateful to all the scientific consultants of this paper.
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