بررسی تکتونیک فعال حوضه‌ آبریز مارون با استفاده از شاخص‌های ژئومورفیک

نویسندگان

دانشگاه تهران

چکیده

لندفرم­های ایجاد شده بوسیله فرایندهای تکتونیک توسط علم ژئومورفولوژی تکتونیک مطالعه می­شود؛ به عبارتی، ژئومورفولوژی تکتونیک کاربرد اصول ژئومورفیک در حل مسائل تکتونیک می­باشد. اندازه گیری­های کمی ژئومورفیک با استفاده از نقشه­های توپوگرافی، عکس­های هوایی، تصاویر ماهواره­ای و بازدیدهای میدانی صورت می­گیرد.  نتایج حاصل از چندین شاخص برای ارزیابی میزان فعالیت تکتونیکی با همدیگر تلفیق می شوند. در این مقاله به بررسی شاخص های ژئومورفیک در این حوضه پرداخت شد. در این مقاله به منظور محاسبه شاخص­های ژئومورفیک از تصاویر ماهواره­ای، نقشه­های زمین­شناسی، توپوگرافی، بازدیدهای میدانی و اصول هندسه و ریاضی و نرم افزار Arc GIS  استفاده شده است. منطقه مورد مطالعه حوضه رودخانه مارون در جنوب غربی ایران و در استان­های کهگیلویه و بویر احمد و خوزستان می­باشد. طول آبراهه 280 کیلومتر می­باشد. شاخص­های مورد استفاده در این مقاله: شاخص گرادیان طول آبراهه (SL)، شاخص تقارن حوضه (AF)، شاخص نسبت پهنای کف دره به ارتفاع (Vf)، شاخص شکل حوضه (B)، شاخص سینوسیته جبهه کوهستان (Smf)، شاخص تراکم زهکشی (P)، شاخص سطوح مثلثی شکل  (TF)، شاخص تقارن توپوگرافی معکوس (T)،  می­باشد. برای بعضی از این شاخص­ها روابط جدید و برای برخی دیگر نیز فرمول­هایی برای استانداردکردن آنها طراحی شد. در انتهای مقاله به بررسی تئوری خطاهای شاخص­ها پرداخت شد. طبق نتایج بدست آمده از بررسی شاخص ها حوضه رودخانه مارون از نظر نوزمین ساختی و بالاآمدگی فعال می­باشد. زیرحوضه­های بالادست بیشتر از زیرحوضه­های میانی و انتهایی فعال می­باشد تکتونیک منطقه تاثیر بسیار زیادی بر لندفرمها و سکونت­گاهها دارد. این نتایج با داده های حاصل از لرزه نگاری و ژئودینامیک که منطقه را منطقه ای لرزه خیز درنظرگرفته­اند همخوانی دارد.
 

کلیدواژه‌ها


عنوان مقاله [English]

Assessment of tectonic of Maroon River catchment using geomorphic indices and improved the indices relations

چکیده [English]

Extended Abstract:
Tectonic geomorphology is defined as the study of landforms produced by tectonic processes, or the application of geomorphic principles to the solution of tectonic problems. (zovoili,2004). These indices have been developed as basic reconnaissance tools to identify areas experiencing rapid tectonic deformation (keller & Pinter, 1996). For study of morphotectonic of region, we must receive the geomorphic indices. These indices are particularly used to study active tectonics.
In this paper we are undertaking a tectonic geomorphology of Maroon River catchment. That the aim of this paper is to determine the most geomorphic indexes such as SL (stream- Length gradient),  AF (Asymmetry factor) , Vf  (Vf Ratio of valley floor width to valley height), B (Basin shape index), Smf (Mountain front sinuosity index), P (Drainage density),
This paper focuses on the application of morphometric analysis at Maroon River catchment in southwest Iran and geomorphic development of Maroon River in response to the neotectonic movements along catchment.
The stream length-gradient index is correclated to stream power and is defined as , where  is the length of the stream from the point of interest, is the change in elevation of the reach and is the length of the reach.the SL index is very sensitive to changes in channel slope, to rock resistance, to topography and to the length of the stream.
The asymmetry factor (AF) is used to indicate tectonic tilting at scale of drainage basin and is calculated by equation  where  is the area of the right- hand side basin and  is total area of the drainage basin.
Triangular facets are interpreted as variably degraded remnants of fault generated footwall scarps. The Vf index is related to the shape of the valley and is calculated by equation , where  Is the width of the valley floor,  are the elevation of the left and right valley divides, respectively, and  is the elevation of the valley floor.
The Smf index reflects the balance between erosional and tectonic forces affecting a mountain front and is defined as   where is the length of the mountain front and  is the straight line length of the mountain front.
The area of research is located on southwestern of Iran in Zagros Mountains at Khuzestan province. In this research we studied Maroon River that originated in the Zagros Mountain. It forms a large alluvial fan. The start (source) from Sadat-Nil mountains and terminated to Jarahi River. The length of Maroon River  is approximately 280km. The Maroon River basin depended on altitude have some different climate. The high land and mountains (up 2500meters) have cold Mediterranean climate, and hill area have Subtropical (2500 – 1000meters) and low land and plains have semiarid. From geomorphology viewpoint, three morphologic faces are dominant on Khuzestan province. At first rocky units which are located in north east of the province. Second; hill units which have coverage in areas located around Dezful, Ramhormoz & Ahwaz cities. Third, alluvial plains & flood plains that form the grounds located in south of Ahwaz to Persian gulf beaches & are a kind of deposited geomorphologies. Mountainous part in Khuzestan is a sample from uniform folded mountainous masses that are named folded Zagros in considering having special lithologic and structural characteristics. Alluvial coverage has hidden geological characteristics of Arabian plat form but regional data especially geophysical data indicates that in this part of the province, sedimentary sequences have clastic facies and a trend of N-S, as very open folds with sides near to horizon have been folded. Geological formations of Khuzestan zone has been thrust as a part of folded Zagros have been formed in sedimentary and tectonic condition hence they have considerable facial differences in terms of time and space.
In this paper we used Arial image, topographical maps, geological maps, Digital Elevation model, field work and applied software such as ArcGIS, Google Earth,
In this paper some of formula of geomorphic indices has improved and some of them have changed. In some indices the authors designed the new formula. The geomorphic indices in this article were calculated. And for any indices the histograms and tables were prepared.
In Behbahan plain and Aghajari plain and the behind of the Maroon River there are some prehistorical settlement and ancient sites and historic sites. The tectonic and geomorphology landscapes influenced in location these sites. During the time some of the sites were abandoned because of tectonic processing and landscapes
In this paper the geomorphic indices have calculated and compared with standard tables and formula and it was concluded that the Maroon River catchment have a high active tectonic and influenced in landscapes.
In the end of paper the authors assessment the theory of errors of geomorphic indices.

کلیدواژه‌ها [English]

  • Morphotectonic
  • Bebahan
  • Maroon River
  • Geomorphic indices