Investigation of the Domain of Quaternary Glacial Erosion in the Northern Geomorphic Unit of Iran

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JAFARI GHOLAM HASSAN; HAZRATI NASRIN

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Journal: QUATERNARY JOURNAL OF IRAN Year:2018 | Volume:3 | Issue:1 Page(s): 67-81

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Title

Investigation of the Domain of Quaternary Glacial Erosion in the Northern Geomorphic Unit of Iran

Author(s)

JAFARI GHOLAM HASSAN | HAZRATI NASRIN | Issue Writer Certificate

Keywords

ELAQ1

CirqueQ1

NorthwesternQ2

QuaternaryQ1

Altitude RatiosQ1

Abstract

Introduction: Glacial evidence is one of the most prominent legends of the Quaternary climate. Quaternary climate changes have played a special role in the form of the current landforms of Iran. The change in the domain of the ELA is the result of these changes. Changes of the ELA are permanent boundaries throughout the Quaternary as the boundary of changes in shaping domains in Iran. Among the glacial evidence, Cirques are very important because of the ability to convert to quantitative data. The Cirques are a reflection of topography, geology, type and duration of glacier effects. Among the basic issues in glacial studies are the ELA and the water and ice equilibrium line. ELA in Porter's idea is a line in which the expansion of the glacier by accumulation is superior to ice melting over the course of the harvest. Materials and methods: The Northern geomorphic unit is said to be part of the continuous integrated mountain range of the southern and western parts of the Caspian Sea, which, like the inert barrier, separated the Caspian Sea from the interior of the country. The first step to estimating the ELA, identifying glacial evidence such as the Cirque. To track the Cirques of the area were used topographic maps with scale 1: 50000 and, the curvy lines, the 30 * 30 digital elevation model, form of glacial evidence and the ARC GIS and Global mapper softwares. Due to the wide area of the study area, the estimation of ELA was integrated with the problem, in order to solve this problem, first the ELA was calculated in the water basins of this unit. In this research, using topographic maps with scale 1: 50000, 2055 glacial Cirques were identified in the study area. For estimating the ELA were used Wright, Cirque-floor altitude, Terminus-to-Head Altitude Ratio (of Wright and Porter), and altitude ratio's methods in different geographical directions. Due to the effect of slope direction of the formation of Cirques in the temperate regions, can not trust the estimated ELA without regard to direction. In Wright's method, ELA is determined using determining the location of the Cirques and passing 60% of the line (Parizi et al, 2013: 117). For Porter, the glacier fills the Cirque when the ELA is not much higher than the average Cirque-floor height. This method is used to obtain the previous ELA (Ghorbani et al, 2016: 4). Using the terminus-to-head wall ratio approach, the equilibrium line altitude (ELA) and the THAR ratio are obtained. With THAR method, the best result is obtained for small and symmetrical glaciers with normal distribution of areas and heights (Yamani et al, 2013: 7). Results and discussion: The mountainous regions of the northern geomorphic unit are located in the central part, and this area has better conditions for the formation of the Cirques and the glacier. This unit is divided into sub-basins of Talesh-Anzali, Sefidrud-Haraz, Haraz-Gharehsu, Gharehsu-Gorganrud, northern parts of the Central Desert. In this unit, 2055 Cirques was identified. The terrains’ direction are western-eastern and the Cirques are formed on the northern-southern slopes, But the Talesh-Anzali Basin is an exception and its terrains’ direction is Northern-Southern, where the east-west slopes are more favorable for glacial activities. In this basin, 84 Cirques were identified. The abundance of Cirques in the Sefidrud-Haraz is 361, the Haraz-Gharehsu is 661, Gharehsu-Gorganrud is 103, and the Central Desert is 846. After removing pseudo-Cirques, 1948 Cirques remained with this unit and the percentage of remaining Cirques was estimated. In the northern geomorphic unit from west to east, due to the reduction of precipitation and rELAtive humidity, ELA has decreased. In Sefidrud-Haraz basin (the westernmost basin) of this unit, ELA is more than 2980 m and is estimated to be 2460 m in Gharehsu-Gorganrud basin (the easternmost basin), with an altitude difference of 520 m. There are 2 exceptions in the basins of this unit; one is the Talesh-Anzali basin that its terrains are in the North-South direction and has the lowest ELA (2033 m) throughout Iran due to local conditions. Another is the central desert basin (Northern part), whose slopes are directed toward the south (southern Alborz). Conclusion: The findings show that the ELA is estimated in different directions in the basins by using the Porter's Cirque-floor altitude and altitude ratio's methods than other methods is most receptive. According to the extent of Northern unit in the longitudinal geographic, the estimated ELA is decreased with reduced precipitation and rELAtive humidity from west to east. The highest ELA in this unit was 2987 m in the Sefidrud-Haraz basin and the lowest elevation were 2460 m in Gharehsu-Gorganrud basin. Talesh-Anzali basin with northern-southern Talesh Mountains are an important exception that has the lowest ELA in water basins (2033 m). The average ELA is estimated at 2589 meters.

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APA: Copy

JAFARI, GHOLAM HASSAN, & HAZRATI, NASRIN. (2018). Investigation of the Domain of Quaternary Glacial Erosion in the Northern Geomorphic Unit of Iran. QUATERNARY JOURNAL OF IRAN, 3(1 ), 67-81. SID. https://sid.ir/paper/381035/en

Vancouver: Copy

JAFARI GHOLAM HASSAN, HAZRATI NASRIN. Investigation of the Domain of Quaternary Glacial Erosion in the Northern Geomorphic Unit of Iran. QUATERNARY JOURNAL OF IRAN[Internet]. 2018;3(1 ):67-81. Available from: https://sid.ir/paper/381035/en

IEEE: Copy

GHOLAM HASSAN JAFARI, and NASRIN HAZRATI, “Investigation of the Domain of Quaternary Glacial Erosion in the Northern Geomorphic Unit of Iran,” QUATERNARY JOURNAL OF IRAN, vol. 3, no. 1 , pp. 67–81, 2018, [Online]. Available: https://sid.ir/paper/381035/en

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