ماهیت اکثر اشکال و فرایندهای بیرونی زمین، اساساً تابع شرایط اقلیمی حاکم بر یک منطقـه در طـی زمان می بـاشد. لـذا آثـار و شـواهـد تغییرات اقلیمی دوران چهارم که مهمترین آنها وجود آثار یخچالی باقی مانده از این دوره است توانسته پدیده های متنوع ژئومورفولوژی را در سطح خارجی پوسته زمین بر جای بگذارد و با توجه به این آثار و شواهد می توان شرایط اقلیمی گذشته را بازسازی نمود. در همین راستا، در این پژوهش اقدام به بررسی آثار یخچالی در منطقه ماهان کرمان پرداخته شده است. نتایج تحقیق نشان می دهد که خط مرز برف دایمی در منطقه مورد مطالعه در ارتفاع 2900 متری و خط تعادل آب و یخ در ارتفاع 1900 متری بوده است. نقشه های رسم شده نشان می دهد که اختلاف دمای حال و دمای گذشته 5/8 درجه سانتی گراد و اختلاف بارش فعلی و گذشته درحدود 300میلیمتراست. همچنین، بر اساس رابطه مانینگ حجم یخ عبوری از دره یخچالی در منطقه مورد مطالعه با سرعتی معادل 3 متر در سال برابر 1305 متر مکعب برابر4/2 لیتردر ثانیه محاسبه شد. نتایج حاصل از بررسی های مورفوسکوپی که بر روی دانه های بسیار ریز انجام می گیرد نیز می تواند بیانگر منشا رسوبات یک منطقه باشد که بر این اساس 6/66 درصد از رسوبات منطقه مطالعاتی را رسوبات زاویه دار تشکیل می دهد که رسوبات یخچالی بوده است و رسوبات آبی 4/33 درصد را در بر می گیرد.
عنوان مقاله [English]
Study of Natural Glacial Evidences in Mahan (Case Study: Glacier of Tigrany Mahan Basin)
Most forms of external nature and earth processes are primarily a function of climatic conditions prevailing during the time zone. Climatic evidences are important reasons glacial of fourth time in the region. This evidence can be helpful to reconstruct to prove past landscape of the region. Therefore, evidences of climatic changes of fourth period that one of the most important of them is remained the glacier could keep geomorphology phenomena in the Earth's crust. According to these evidences, past climatic conditions can be reconstructed. In this study have been investigated effects of glacier area in Mahan basin. Study area called the Tigrani river basin in Mahan.
Latitude is 57º 10' to 57 ° 20’ and 29° 50' to 30° 05' east. Area of Tigrani basin is about 59 km with. Is Maximum height 3920 meters in the south of area and minimum height 1900 meters in the north of study area?
The research based on field activities and has been used geomorphologic and climatic evidences. Laboratory studies and Wright's method have been applied.For this purpose, in first glacier cirques were determined on the contour map 1:50000 scale, and field observations. Then correlation between average height and average annual temperature and precipitation of selected stations the temperature and is rain fall were prepared. Then, was calculated the border line of permanent snow and adiabatic temperature drop rate. Using the height of the snow line and adiabatic loss was drawn fast temperature isotherm map.Then, were calculated correlation between present temperature and present precipitation with overlapping present isothermal and precipitation maps and obtained formula from the precipitation map in the past were drawn. Finally, were taken samples of sediments in the field operations, and then were studied in the geomorphology laboratory and result of granolometry and morphoscopy operations on the samples of sediments was determined.
The result shows that eight cells surround the studied basins. The most powerful cells are long-range heights of west Abarq station in the southern part of study area with temperatures about -7°C. Also encompasses a cold cell in the southern basin, which has been determined the mountain Joupar whit temperature min 5 degrees below zero. Temperature increases to the northern region so that near the city of Mahan is reaches to 6 degrees. The past rainfall map shows that highest level of rainfall was happened in most ambient temperature in the past and moisture conditions similar humidity today were determined. in eight cells. The highest rainfall was available in the southern region around the cell moisture Dodaran Station (West Station Abarq) with 1400 mm rainfall. Whatever forward to the north area reduced rainfall and its amount reaches to 500 mm. While, in the present time the highest rainfall in the same Dodaran moisture cell amount 1100 mm and the northern Mahan city reaches to 170 mm.Past Precipitation map shows that rainfall in its catchment area reach of 1300 mm in height to 475 mm in the Mahan city.
The results show that snow line in the study area was in 2900 meters and water and ice equilibrium line has height of 1900 meters. The coldest period of the region have snow in all year permanently and average temperature on the height is 0°c. Then, according to field observations, and final level of glacier blind valleys and also settlements distribution in the study area 1900m height for low of the glacier. was determined Plotted maps showed that difference between the present and the past temperature was 8.5 ° C and difference between the current and past rainfall was about 300mm. Also based on the Manning formula volume passing through the valley glacier ice in the study area was calculated with a speed equal 3 m in 1305m³ equal the 2.4L/s. The results of morphoscopy studies show that fine grains can also indicate the source of sediments. Based on the studies 66.6 percent of the study area covers angular deposits form of glacier sediment, and water deposits were 33.4 percent regarding snow line and adiabatic loss track with amount of 0.67°c per 100m and temperature maps of present and past, results showed difference between current temperature and past is 8.5°C. The result showed that previous studies considered the equilibrium line of water and ice at 5°C, while during the field observations were found in the study area the equilibrium line of water and ice 1900m height, with figure 6.5 ° C.