بررسی ویژگی‌های مورفو‌ـ رسوبی مخروط ‌افکنه رودخانه کال‌شور نیشابور در شمال‌شرق ایران با تأکید بر کنترل‌ های اقلیمی کواترنر

نوع مقاله : مقاله پژوهشی

نویسندگان

1 ژئومورفولوژی، دانشکده ادبیات و علوم انسانی، دانشگاه فردوسی مشهد

2 جغرافیای طبیعی، دانشکده ادبیات و علوم انسانی، دانشگاه فردوسی مشهد

3 ژئوفیزیک، دانشکده ژئوفیزیک، دانشگاه تهران

4 زمین شناسی، دانشکده علوم، دانشگاه فردوسی مشهد

چکیده
رسوبات کواترنری مخروط ‏افکنه ‏ها اطلاعات مهمی از شرایط اقلیمی گذشته و تحولات محیطی حوضه آبریز بالادست خود ارائه می‏کنند. در این پژوهش نویسندگان به بررسی تکامل الگوی رسوبی بر سطح مخروط‏افکنه کال‌شور پرداختند تا با استفاده از تفسیر نتایج حاصل از آنالیزهای ژئوفیزیکی و ژئوشیمیایی این رسوبات محیط رسوب‌گذاری این رسوبات در دوره کواترنر را بررسی کنند. مخروط ‏افکنه کال‌شور یک مخروط کوچک و نسبتاً متقارن در شمال‌شرق ایران و در دامنه جنوبی رشته‌کوه بینالود است که بر پایه ویژگی‏های رنگ و بافت و اندازه ذرات و مطالعات میدانی سطح آن به 8 سطح مورفوـ رسوبی با نام‌های A1 تا A8 تقسیم شده است. بر پایه مطالعات رسوب‏شناسی، رسوبات مخروط‏افکنه کال‌شور دارای جورشدگی بد و بسیار بد، کج‌شدگی متقارن (تقریباً متقارن تا بسیار مثبت)، کشیدگی (متوسط و پهن)، و بافت گراول و گراول شنی هستند. در تفسیر ویژگی‏های ژئوفیزیکی، اندازه‏های میانه، نمونه‏های A2 و A5 و A6 و A7 دارای میانه پایین‌تر، جورشدگی ضعیف، و کشیدگی بیشتر نسبت به بقیه رسوبات‌اند. همچنین، بر حسب نتایج آنالیزهای شیمیایی حاصل از آزمایش XRF، میزان عناصر اکسیدهای کلسیم و آلومینیوم و سیلیس و همچنین نسبت عناصر منیزیم به کلسیم و منگنز به کلسیم به ترتیب در نمونه‏های A1 و A3 و A8 کاهش و در نمونه‏های A6 و A2 و A5 و A7 کاهش می‏یابد که به ترتیب نشان‏دهنده شرایط اقلیمی سرد و خشک و گرم و مرطوب است. به طور کلی، با توجه به نتایج آنالیزهای ژئوفیزیکی و ژئوشیمیایی سیلاب حمل‏ کننده در نمونه‏های A6 و A2 و A5 و A7 دارای سرعت بسیار زیاد (و نه لزوماً دبی بالاتر) است. همچنین این سیلاب‏ها در محیط‏هایی با اقلیم سرد و خشک و با حاکمیت تخریب فیزیکی رخ داده‏‏ اند و در نمونه‏ های A4 و A1 و A3 و A8 اقلیم گرم و مرطوب با سیلاب‏های مداوم، اما، با انرژی کمتری رخ داده‌اند. بنابراین 4 سطح رسوبی در نتیجه اقلیم سرد و خشک و 4 سطح رسوبی در نتیجه اقلیم گرم و مرطوب در سطح این مخروط قابل مشاهده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله English

Investigation of morpho-sedimentary features of Kalshour River’s fan, Northeastern Iran: Emphasizing Quaternary climatic controls

نویسندگان English

Azar Khosravi 1
Seyyed Reza Hosseinzadeh 2
Morteza Fatahi 3
Mohammad Khaneh Bad 4
1 Geomorphology, Faculty of Literature and Human Sciences, Ferdowsi University of Mashhad
2 Natural Geography, Faculty of Literature and Human Sciences, Ferdowsi University of Mashhad
3 Geophysics, Faculty of Geophysics, University of Tehran
4 Geology, Faculty of Science, Ferdowsi University of Mashhad
چکیده English

1- Introduction
Climate has an important role in the sedimentation of quaternary fans. In the dry climate of the present time, the surface materials of the hills have deposited during the wet or cold periods, but these deposits have been transferred to alluvial fans during the transition to dry or warm periods of Quaternary (Bull, 1991). Instead, in the present basins that are located in semi-arid climates, sediments have been transferred to fans during the wetter or colder period. Alluvial fan’s deposits are sensitive to hydrological conditions, and the study of these sediments provides worthwhile information from paleo climate. Quaternary sediments of the alluvial fans offer important information about paleoclimates conditions and paleo environmental changes of their catchments.
2-Materials and methods
In this research, the authors have studied the evolution of sedimentary pattern using the results of geophysical and geochemical analyses on the surface of the Kalshour Fan in the Northeast of Iran, during the Quaternary period. The Kalushshour fan is a small and relatively symmetrical fan in the southern slopes of the Binaloud Mountain Range in North eastern Iran (Fig.1 and 2). This area is closed to city of Neyshabour (20 km) at latitude with latitude 36 ° 10'35 "N to 36 ° 12'36" N and longitude 58 ° 59 '6 "E to 59 ° 0' 11 "E. The mean annual precipitation in the region surrounding the study area is 15 to 28 cm/year(source: Meteorological Organization of Khorasan Razavi, Iran ), suggesting that the study area lies in the arid to semiarid transitional zone. The focus of this research is on the Kalshour basin on the southern slopes of the Binaloud mountains and alluvial fan and terraces. And attempts to compare the dispersion of the major and trace element oxides with the standard averages of these sediments present.
The first map of the study area was prepared in the ArcGIS 10.3 software based on aerial photographs, topographic maps and satellite images to study the alluvial fan surface. Then different levels of geomorphological surfaces were determined according to the colour, texture and grain size parameters. Then, during the field trips, the accuracy of the map Validated with the reality on the ground and its bugs were met.
Eight samples were collected from the surface of the alluvial fan for studding of their geophysical and geochemical characteristics. Chemical analyses were performed for eight samples. Analyses were performed by x-ray influence spectrometer and inductively coupled plasma-mass spectrometry (ICP-MS) at the Bespar Payesh (Mining Material Research Co), Analytical Laboratories Ltd. in Ferdowsi university of Mashhad, Iran. The main oxides are in% and trace elements in ppm. Based on morpho-sedimentry characteristics, the surface of this fan is classified into 8 levels, called A1 to A8.
After drying the sediment in the oven, sediments were weighted at intervals of 0.5 to 5 phi. Then, other parameters related to the sediment texture, sedimentation, degradation, sorting, etc. were determined, and the associated analyses and diagrams, such as percentage cumulative graphs, percentages, etc. were mapped using the Gradistate software. To ensure the results obtained, the graphs of the name and texture of the sediment were re-constructed in the 3Dplot software environment. To improve the achievement, the corresponding graphs in the Corel DRAW Graphic Suitee software environment were restored and Set up. At the next step. Their findings were compared together.
3-Results and discussion
 Based on the geophysical analysis, A2, A5, A6, and A7 samples are poorly sorted and stretchy than the rest of the sediments. Elemental geochemistry well describes the temperature and precipitation of paleo conditions. Also according to the geochemical analysis, the amount of calcium, aluminum, and silica oxide elements and the ratio of magnesium to calcium and manganese to calcium in samples A1, A3 and A8 were decreased and in s A6, A2, A5 and A7 samples were decreased Which in turn reflects the cold - dry and warm - humid climate. In general, according to the results of geophysical and geochemical analyses, carrier flood in the A6, A2, A5 and A7 sediment samples had been passed with very high speed. Also, these floods occurred in a climatic environment with a physical watering regime. In A4, A1, A3 and A8 samples, warm and humid climate were associated with continuous but less energetic floods. Thus, four sedimentary levels due to the cold and dry environment and four sedimentary levels due to the warm and humid environment are visible at the surface of the cone.

کلیدواژه‌ها English

Alluvial fan
Morpho-Sedimentary Features
Quaternary
Climatic Control
Northeastern Iran