بررسي رفتار آشوبناك تلخه رود استان زنجان در كواترنري

Investigation of Zanjan Talkheh- Rud Chaotic Behavior in the Quaternary

ژئومورفولوگ ها معمولاً به عنوان يك اصل ضروري به تشريح گذشته و حال پرداخته و آينده فرآيندها را پيش بيني مي كنند تا ماهيت و سرعت تغييرات را درك نمايند. در دو طرف زنجانرود دشت هاي وسيعي با پوشش رسوبات آبرفتي كواترنري گسترده شده است. شكل ظاهري منطقه به گونه اي است كه چنين به نظر مي رسد سراب رودخانه هاي هر دو طرف، به بلندترين ارتفاعات منتهي شوند؛ اما در قسمتي از بخش هاي جنوب غرب دشت هاي زنجانرود، در مجاورت جبهه ي كوهستان، آب هاي قسمتي از ارتفاعات جنوبي زنجان توسط رودخانه اي به قزل اوزن منتقل مي شود كه خط تقسيم آب طرف راست آن، منطبق بر رأس مخروط افكنه هاي قديمي است.براي بررسي اين رفتار آشوبناك، ابتدا 30*30 DEM محدوده مورد نظر استخراج گرديد. براي شبيه سازي توپوگرافي گذشته به وسيله نرم افزار Pixel to code خطوط منحني ميزان متعادل (صاف تا سينوسي)، رقومي شد و ارتفاع خطوط منحني ميزان نامتعادل (باي مدال و پنجه اي) در بخش هاي مختلف، بر اساس ارتفاع منحني هاي ميزان متعادل بازسازي گرديد. با تغيير سطح اساس قزل اوزن، بر آبراه هاي با حوضه آبريز كوچك كه موازي با زنجانرود، به قزل اوزن مي پيوسته، فرسايش قهقرايي غلبه كرده و مسير آبراهه هاي بخشي از دامنه هاي شمالي ارتفاعات جنوبي زنجان رود را تغيير داده است. بر اثر اين اسارت رودخانه جديدي به نام تلخه رود شكل گرفته است. شواهد اين رفتار آشوبناك يك مخروط افكنه 110 كيلومتر مربعي و دشت سري با تيپ مخروط افكنه به هم پيوسته است كه در حال حاضر هيچ حوضه آبريزي از بالادست بر آنها تسلط ندارد. كوتاه تر بودن طول آبراهه ها در يك طرف رودخانه، تفاوت اختلاف ارتفاع زياد رودخانه از خط تقسيم آب در دو طرف، وجود رسوبات آبرفتي دياژنز نشده در خط تقسيم آب، تغيير مسير 90 درجه رودخانه، منحني هاي ميزان با پالس هاي عميق در بين و پايين دست منحني هاي ميزان صاف تا سينوسي ساده ازجمله شواهد ديگر تغيير مسير اين رودخانه است.

Introduction Geomorphology usually described as essential to the past, present and future prediction of nature's processes and estimate pace of environment changes. On both sides of Zanjan- Rud plains extended that covered with quaternaries alluvial sediments. The area appearance is a in a way that rivers on upstream of both sides should lead to higher elevation. But in parts of the southwest of Zanjan- Rud plains part front Mountain rivers water south of Zanjan parallel with the front part of the heights of the mountains leads to the Ghezel owzan. Rivers chaotic behavior resembles the appearance of the area so that Disneyland has created forms that look like they emphasized their dominance Neotectonic processes. Land forms created in another part of the basin are not similar to works of the old lake terraces. Although at first sight this Landforms evidence of the activities area so that SATARI Neotectonic (2017) is known which formed the basis of the Neotectonic landforms and introduced analyze the indexes of the terms tectonically active basins has morphotectonic but Land forms is not the tectonic. the result end Although the possibility of tectonic activity is also According to faults in the area but the main factor in the formation of landforms function of changes in the Quaternary river to Neotectonic activities. Such conditions cause chaotic behavior quotation was Zanjans Talkheh- Rud does apply during the Quaternary. Materials & Methods First this chaotic behavior Study, the area Intended was determined from DEM 30 * 30 areas. For the past topography simulation was Digital Contour lines the equilibrium by Pixel to code software, and in different parts without equilibrium of Contour elevation lines, reconstituted on the basis of equilibrium line elevation. The phenomenon Direction captured of deviation and the river is now flowing in them was removed, in Table specifications latitude and longitude in Surfer software and specification X, y, Z reconstruction topographic, entered its output in software Global mapper and the spatial possible Rebuilding for past River Basin rivers. With longitudinal and transverse profiles and topographies of waterways in the direction of the current and was obtained previous simulations differences in altitude are and the rate of erosion. Referring to the field work and correct errors of interpretation and analysis was performed. Discussion of Results & Conclusions Field studies indicate that evidence of deviation in bondage or topographic maps have been reflected as follows: 1- changes the direction at an angle of 90 degrees or greater along the rivers. 2- There are coarse-grained alluvial deposits in the river upstream, elementary and middle part is the source of the water, sediment and the final or the coastal route, sometimes in the midst of the water, and they are of record sediments. 3- A basin over time almost is stream symmetric .it means a left bank and right in time is equal and symmetrical. Tectonic may be due to disruption of such a situation; but when one side has no river stream a basin as a significant and insignificant area of study changed in the river. Stream Shorter towards the other side of the river indicate redirection of the river. 4-The heigh difference is inevitable in the coastal river basins; but when the difference in altitude along the channel length less and not diagenesis alluvial deposits in the river water sharing is indicative of a change to the track previous. 5-Contours with deep pulses or deep sinuses between a smooth contour and downstream to a simple sinus uniform lithology of a change of control over the area due to regressive erosion base level changes due to the redirection of the river. With the changes of the base level of Ghezel owzan, retrogressive erosion dominant and shed on a river with very small area of basin along Zanjan- Rud to Ghezel owzan .and could be a part of divert northern slopes of the mountains south of Zanjan- Rud and lead to Gezel owzan. an‎d create a new river that termed Talkhe Rud. A 110-square-kilometer alluvial fan testator chaotic behavior and alluvial plain series fans interlocking type which no upstream basin has any control on it. Shorter length of stream at one side of the river , the difference of high Elevation difference between river dividing line water on both sides existence of alluvial sediment not digenesis in Water dividing line, rivers 90 degrees direction change contours With deep pulses within and downstream of the smooth curve are simple sinus to a change of river courses.