چکیده:
در قسمت های شمال غرب حوضه آبريز دریاچه ارومیه در بخش قوم تپه صوفیان، تپههای ماسه ای بهصورت محدود قابل مشاهده است که پس از بررسی های علمی صورت گرفته علت اصلی شکل گیری آن ها برآیند فعالیت بادهای غالب و ماسه های ریزدانه است. هدف غایی اين تحقيق بررسی کانیشناسی در منشأ یابی و تحلیل مقطع تپههای ماسهای در قم تپه صوفیان است. با توجه به اهمیت تحلیل آماری باد در منطقه، آمـار بـاد 2 ایستگاه پیرامونی اخذ و از طريق ترسيم گلبادها، تجزیه وتحلیل شده است. تغییر راستای وزش فصلی این بادها در محدوده مورد مطالعه، نتیجه تأثیر شرایط کمفشار حاکم در چاله دریاچه ارومیه و دشت تبریز است. اقليم خشک و نیمهخشک، فقر پوشش گياهي و همواري نسبي سطح زمين از مهم ترین عـواملي هستند كه باعث غلبه فرايندهاي فرسايش بادي در منطقه قوم تپه شدهاند. ماسه های نمونهبرداری شـده از 5 مقطع، از طریق آزمایش های XRF و XRD تجزیهوتحلیل شده است و درصـد زيـاد کانیهای آذريـن (كـاني سنگين) در نمونهها، زياد بودن ميانه قطر نمونهها (293 ميكرون)، رابطه ميانگين قطر ذرات بـا فاصـله حمـل (كمتـر از 20 كيلومتر)، ضرايب گردشـدگي نيمـه زاویهدار در اكثـر نمونه ها مورد تائید است. همچنین نمونه ها برآیندی از حمل آن ها توسط باد و آب بوده و نشان دهنده ارتباط منطقی مورفوسکوپی دانه هاست به دلیل فاصله زمانی حمل با منشأ رسـوبات تپه های ماسه ای نزديك و از سطوح مخروط افكنه (دشتسر) و اراضي زراعي متروكه واقع در نواحی شرق و جنوب و همچنين بسـتر رودخانه های قدیمی در بخش جنوب شرقی منطقه است. نتايج تحقيق نشان میدهد بالا بودن نسبت ذرات ماسه های كمتر از 250 ميكرون، ضعف پوشش گياهي و جهت بادهای غالب محلی، محيطی مناسب برای گسترش فرسايش بادي مهیا میسازد، بهطوریکه با كاهش اين نسبت از شدت فرسايش نيز كاسته میشود. اين مورد با بررسي نمونه های دانه سنجي، عمليات ميداني و مشاهدة عکس های هوايي نيز تأييد میگردد.
Introduction
Our country lies in the arid and desert belt of the world and is two-thirds of its size in the realm of dry land. Works such as the drying up of inland lakes, sandstorms, dust, and the intensification of wind erosion have prevented the rate of desertification in recent years in the country (Shiravi & Sepehr et al., 2016). The area of arid and ultra-arid regions is 472566 and 573884 km2, respectively, which is approximately 631.5 arid and semi-arid territories based on the modified Damarton system. In this system, the areas with drought index between 0-5 and 10-15 are considered as arid and ultrasound respectively. The amount of erosion and the volume of material transport in arid regions depend on the wind speed, direction and frequency characteristics, and on the ground, topography, and sedimentary features. Understanding the geomorphologic features of the toll that develops in the morphoclimatic environments of arid regions can inform us of such environments and aware the human beings towards actions that may alter ecosystems and natural habitats. The geomorphologic features of arid lands especially sand dunes are the result of specific dynamics and variability in these areas (Xin-Rong Li et al … 2010).
Investigating and studying the related research background, it was found that most of the geomorphologic classifications and analysis of arid lands were done using the most important factors affecting the geomorphologic, geomorphometric parameters, and the prevailing winds. The present research was conducted to identify and investigate several sections through dominant wind and mineralogical analysis in the hilltop sand dunes located on the western side of the Sufian city, which today is experiencing the development of downstream industries.
Materials and Methods
One of the important factors which is necessary for the formation of wind dunes is the source and the origin of the sand. It is not formed without the elements in the size and size of the dune sand. Therefore, in areas where there is wind erosion and the source of sand harvesting, they are heterogeneous. Pie and Tsevar (1990) find that the amount of sand supply is dependent on the type of rocks exposed in the area, the speed, weathering conditions, the erosion, and the efficiency of other sediment transport factors in separating the sand particles from the larger particles. According to Smith (1982), running water often plays a key role in the sorting and concentration of weather-induced crop transfer products. In order to provide the source and the origin of sand, conditions, and factors are known as morphogenesis and morph dynamic systems.
Results and Discussion
Morphoscopy of sand dune elements
For morphoscopy examination of sand in hill tribe, 5 specimens were selected systematically according to their dispersion while the microscopic examination was performed on them. In this study, the grains were studied from two aspects, one being the surface condition of the grains having matte, aura, luminous, physical, and chemical degradation modes, and the other in terms of abrasion; thus, the grains are more exposed to water and wind. The more it is worn, the more rounded it is and the distance traveled can be determined in addition to the shipment.
Wind situation based on synoptic stations
The purpose of this study is to study the mineralogy of the origin and to analyze sand dunes cross section in Qom Sufi hills, firstly, based on daily wind statistics of Shabestar and Tabriz synoptic stations, which is the nearest synoptic study site. Using Land Rose software, wind direction prediction (annual and monthly) was done. Based on the theoretical basis that wind flows from a high-pressure cell to a low-pressure cell, the temperature gradients have an effect on the temperature between the two currents.
Considering the direction of the winds in the region, the study has been attempted to identify the topography of the wind erosion forms, their location, and how they affect the direction of the region's winds. The wind data from the Tabriz Synoptic Station and Shabestar West between 2012 and 2017 were used to investigate the wind situation in the region. Accordingly, high winds at the Shabestar station, northwest-northeast and at Tabriz station, east-northeast with high frequency and speed. Of course, there were also winds with less abundance in the north, northwest, south, and southeast.
The early origin of the hill folk dunes
The wind dunes of the Northeast Highlands (Moreau), the Northwest Highlands (Misho), and the North Sufian Highlands can be considered as the primary from their original location sources after the impact of morphogenesis and degradation of the rocks due forming these mountains. Directly transported by wind and deposited in the local wind dunes it accumulates in the form of sand dunes. But, in the Qom hill Sufian can such a sand be found to have the properties to move and precipitate directly after being separated from the base stone by wind. Morphoscopy on the sands of the region also confirms this. Therefore, the material produced in these mountains by morphogenic processes is transported by transport agents, especially current waters and is accumulated in lower areas after decelerating; thereby, providing a secondary source for the dunes are examined.
Secondary origin of the hill folk wind dunes
Secondary origin is that the dispersed material is transported in elevated areas and at its initial location under the influence of morphogenic factors, especially water, and is accumulated in sediments, alluvial fans, rivers, and pits (Jian Hua XIAO et al. 2015), and then as these discrete elements dry up, the wind moves them and accumulates as wind dunes. As the dunes expand and the southwest wind prevails over other winds, the secondary origin of these dunes will be mostly in the west and southwest of the region. This does not mean, of course, that only sand is transported to the area. Because of the prevailing winds and their predominance at certain times of the year, they can move sand from other areas, especially east and northeast, due to the dominance of the east and northeast winds in summer according to the charts. Therefore, the secondary origin of wind dunes in the region can be divided into:
1) Old rivers, streams and riverbeds 2) Impact cones 3) Rubble cones 4) Lakes 5) Lakes terraces, and 6) Dunes.
Conclusion
Like most sand dunes in Qom, the sand dunes have a gentle slope to the direction and side to the wind and a steep slope to the back. On the back side of the wind, there are protrusions and recesses. The protrusions are made by connecting the arms to each other and have a lower height and slope while indentations are longer and have a higher slope. The origin of the winds in the region is mainly due to the predominantly sandy soils as well as the occurrence of fine sediments at the end of the area's fan cone and plate floodplain, which may not account for much of the surface area. And the end of by cones feeders that bring out the sedimentary are provided. In fact, the rivers of the area, after exiting the mountains, developed on the plainand and aware of there are processes affecting the development and evolution of the sandy surfaces of their have surrounding land. The results show that wind erosion is more frequent wherever plate floods are wider. As a result, the main source of sand supply is the sediment of the old rivers and the barren lands without its hard surface cover. In order to orient the source regions, the status and direction of the winds of the area were analyzed using the Globad diagrams and field data were selected from five sections systematically. High energy verifications indicate that the main contributors to sand supply and dominant winds by transport of fine sediments and rocks (carbonate and volcanic) are bedrock of old rivers and barren lands without surface cover wherever floods occur. The wider the plate, the higher the wind erosion in favor of dune development.
خلاصه ماشینی:
٥- نتایج حاصل ازآنالیز XRF داده های آنالیز اکسیدهای اصلی و LOI در ٥ نمونه ماسه طبیعی به روش XRF به شرح جدول زیر تقدیم می شود: (رجوع شود به تصوير صفحه) با توجه به اهداف این تحقیق ، ابتدا با اســـتناد به مطالعات پیشـــین و آمار باد تجزیه وتحلیل شـــده ایســـتگاه های سـینوپتیک منطقه بررسـی گردیده و سـپس در تکنیک کار، مقایسۀ ارتباط اشکال مورفولوژی تپه ها و پهنه های ماسه ای موجود و وضـعیت سـرعت ، جهت و فرکانس بادهای منطقه و نیز ارتباط تأثیر بادها براسـاس دانه سـنجی انجام شـده برروی بیش از ٥ نمونۀ ماســه بادی برداشــت شــده از ســطح منطقه بوده اســت .
الف ) بلور پیروکســن در مجاورت قطعه ســنگ ولکانیکی حاوی بلورپلاژیوکلاز؛ ب ) بلور فلدسپار زونینگ دار؛ ج ) قطعه کوارتز (رجوع شود به تصوير صفحه) پلیکریســتالین دگرگون شــده ؛ د) جانشــینی هماتیت در بلور مگنتیت اولیه ؛ ه ) تصویری از بلور همـاتیـت در زمینـه قطعـه ســنگی؛ و) (رجوع شود به تصوير صفحه) ٥-٢- نمونه شماره ٢ {مراجعه شود به فایل جدول الحاقی} مقطع مورد مطالعه نشـانگر یک نهشـته رسـوبی منفصـل متشـکل از ذرات ماسه در محدوده اندازه ٠/٢٥ تا ٠/١٢٥ میلیمتر، معادل ماسـه ریزدانه ، اسـت .
٥-٤- نمونه شماره ٤ {مراجعه شود به فایل جدول الحاقی} مقطع مورد مطالعه نشـانگر یک نهشـته رسـوبی منفصـل شامل ذرات آواری ماسه ای با میانگین اندازه در حد ماسه متوسـط دانه (medium sand) است .