بررسی تخریب پذیری سری سازندی قم در منطقه بیابانی (مطالعه موردی: کاشان) (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
از جمله عوامل اثرگذار و تعیین کننده شدت تخریب، میزان رسوب زایی و تخریب پذیری سازندها است. حساسیت متفاوت سازندها سهم آن ها را در شکل گیری واحدها برعهده می گیرد. سازندهای زمین شناسی متعددی در شکل گیری هر منطقه دخیل است. در این مطالعه، عمده سازندهای تشکیل دهنده از سازندهای سری قم است. در این پژوهش براساس روش سلبی اصلاح شده، مقاومت سازندهای قرمز بالایی، قم، قرمز زیرین و ولکانیک ائوسن برآورد و در قالب طرح آماری کاملأ تصادفی بااستفاده از آزمون چند دامنه ای دانکن مقایسه شده است. در روش سلبی شش پارامتر سختی چکش اشمیت، جهت درزه، درجه هوازدگی، عرض، فاصله و پیوستگی درزه ملاک بررسی مقاومت سنگ می باشد که وضعیت تخریب پذیری سازند را از خیلی حساس تا خیلی مقاوم تعیین می نماید. در روش اصلاح شده، فاکتور پوشش گیاهی نیز اضافه شد. طبق نتایج به دست آمده سازند ولکانیک ائوسن با 16/76 امتیاز در رده سازندهای مقاوم، سازند قم با 66/63 امتیاز در رده سازندهای متوسط، سازند قرمز زیرین با 5/47 امتیاز در رده سازندهای حساس و در نهایت سازند قرمز بالایی با 33/26 امتیاز در رده سازندهای خیلی حساس قرار گرفت. بنابراین، می توان اذعان نمود باتوجه به وضعیت تخریب پذیری؛ سازندهای سری قم عمدتاً حساس بوده و قدرت رسوب زایی بالایی دارند. بررسی شواهد ژئومورفیک دامنه ها نیز مؤید نتایج به دست آمده از پژوهش است به طوریکه سازند ولکانیک ائوسن با دامنه پرشیب و تشکیل رخساره های ستیغ و پرتگاهی بیش ترین مقاومت و سازند قرمز بالایی با ایجاد در رخساره های دامنه های کم شیب و تپه ماهوری بیش ترین حساسیت را نشان داده اند.Survey of the degradability of Qom Formation Series in the desert area (Case study: Kashan)
In most geological formations, the difference in sediment production capacity is due to differences in the texture, strength and sensitivity of the formation to erosion. One of the effective factors in sedimentation is the type of formations in the region, so that erosion-sensitive formations have more sedimentation than resistant formations. The different sensitivities of the formations, in fact, assume the difference in their contribution to the formation of plain and playa units. To classify the resistance of geological continuous materials to erosion, most properties of rock such as hardness, seams and cracks, lamination, seam factors are considered. And their sensitivity or resistance to the corrosive agent is considered. Different types of rocks affect the aeration process through physical and chemical properties. The degree of aeration of minerals depends on their chemical composition, crystal shape, size and degree of crystallization. In the present study, the outcrop of the Qom Formation series was identified in the study area by Upper Red, Lower Red, Qom and Eocene volcanic formations. After identifying the outcrop, sampling units of the study area formations were determined based on the units representing the structure. Mu unit for upper red formation (slope of marl, red conglomerate and gypsum), unit O1 for lower red formation (slope of red conglomerate, sandstone and marl), OMq unit for Qom formation (slope of reef limestone, shale Gray and sandy marl) and the Ev6 unit were identified for the Eocene volcanic formation (slopes of andesite, basalt and rhyolite lavas). After determining the sampling units; The negative method was performed to investigate the degradability of the selected units from the formations based on a completely randomized statistical design with six replications on the slope. The negative method was introduced by (negative) in 1980 to classify rock masses for geomorphological purposes. In this method, at each level, the desired parameters will be measured and scored, and it consists of six parameters of Schmidt hammer stiffness, direction of joint, degree of weathering, width, distance and joint continuity. Also, the vegetation status on the slope of the formation was studied in the form of a five-position ranking and geomorphological evidence with emphasis on the facies of the slopes representing the formation. The results were analyzed using analysis of variance and Duncan's multi-domain means comparison test and statistical inference of the results. Finally; The results were analyzed and the degradability status of the formation units was compared and the results were matched with the geomorphological evidences of the slopes and the vegetation factor was added to the negative model factors. According to the results of the analysis of variance of weekly factors, if the level of significance is less than 0.05, that factor has a significant difference and if the level of significance is greater than 0.05, that factor does not have a significant difference. Therefore, in all the above factors, the level of significance is less than 0.05 and has a significant difference. Also, Eocene Volcanic Formation with 76.16 points in the category of resistant formations, Qom Formation with 63.66 points in the category of medium formations, Lower Red Formation with 47.5 points in the category of sensitive formations and finally Upper Red Formation with 33. 26 points were placed in the category of very sensitive formations. Therefore, it can be acknowledged given the situation of destructibility; Qom series formations are mainly sensitive and have high sedimentation power. Examination of the geomorphic evidence of the slopes also confirms the results obtained from the study that the Eocene volcanic formation with steep slopes and the formation of ridge and precipice facies showed the highest resistance and the high red formation with the formation of low-slope slopes and satellite hills.The different reactions of formations to degradation are very important for the integrated management of natural resources, so that it can be considered in several categories such as erosion management, vegetation management and landscape management. In general, the behavior of different formations to biological factors, especially vegetation and habitats of the cover affect them. Since vegetation reflects environmental and human factors such as exploitation, so vegetation management is a key element in the study of ecosystems and its status can determine the health of vegetation and its position relative to equilibrium. On the other hand, due to the fact that the plants located on the formations are often less than half a meter in height and effective wind erosion takes place at this height, so determining the vegetation status and identifying it can play a special role in estimating the erosion of formations. Also, recognizing the physical-biological sedimentation behaviors of formations in desert areas can be the basis for identifying the state of degradation and erosion of these areas and be the primary source of water and wind sediments in the region. Help life. For this reason, in the present study, in addition to the six parameters of the negative method, vegetation factor was used to investigate the degradability of pre-Quaternary formations. Based on the results of the study; The most obvious example of low strength of the formations using Schmidt hammer was seen in the upper red formation with a score of five, and this indicates the instability of the formation. Also, the degree of weathering was observed for the formations of the study area from fully aerated formations to formations with high weathering. So that the upper Red Formation was completely aerated and the Qom, Lower Red and Eocene volcanic formations had a high degree of weathering. The distance between the joints was between 300 to 50 mm and the obtained score in all formations ranged from 6.17 to 22.83 which is a sign of instability and average strength of the formations. Regarding the orientation factor, the Upper Red, Lower Red, Qom and Eocene volcanic formations were estimated with scores of five, six, and 14, respectively, indicating unfavorable orientation.
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