Geomorphology
Mojtaba Yamani; Shahnaz joudaki
Abstract
Terraces are important archives for paleontology. In this research, the paleotemperature changes and discharge frequency of Jajroud basin in the northeast of Tehran have been investigated based on the sedimentology and geochemistry characteristics of the reservoirs. First, the sediment samples were analyzed ...
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Terraces are important archives for paleontology. In this research, the paleotemperature changes and discharge frequency of Jajroud basin in the northeast of Tehran have been investigated based on the sedimentology and geochemistry characteristics of the reservoirs. First, the sediment samples were analyzed with calcimetry, EC, XRF, and PH techniques, and then these data were correlated with the indices of salinity, chemical weathering, acidity, and maturity of the sedimentary layers of the defenses. The results show three periods of flow changes, during the alternation of cold and warm periods of the river. One is at the peak of the glacial period, when the accumulation of snow and ice in the mountainous part has reduced the discharge (before the Holocene). In the second stage, by passing from the glacial period to the warm period (11 to 8 thousand years ago), Jajrud has experienced its highest discharge. Because the melting of glaciers has been accompanied by rainfall. The existence of very coarse layering in the early Holocene terraces indicates the occurrence of floods in this period. In the third stage, the dominance of recent hot and dry conditions (8 thousand years ago until now) and the lack of glacial deposits have led to a decrease in river flow. Based on this, the geochemical studies of the reservoirs can provide valuable data to recover the dynamic changes of flow and discharge during the Quaternary period and can be generalized to other similar basins.
Gholam hassan jafari; Mina Avaji
Abstract
1-IntroductionEarth's climate is one of the most important structural factors. More natural and human trappings are affected by the weather. The coefficient of variation of less precipitation is reagent stability and steady time distribution (Fatahi, & Rezaei, 2009). The quaternary climatic changes ...
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1-IntroductionEarth's climate is one of the most important structural factors. More natural and human trappings are affected by the weather. The coefficient of variation of less precipitation is reagent stability and steady time distribution (Fatahi, & Rezaei, 2009). The quaternary climatic changes have created different landscapes, such as glacial circus, glaciers, and especially erratic rocks, according to the first topography of Iran that found in high regions of Iran. Geomorphologists' permanent snowline altitude is determined to help the circus of mountain effects. The continuous snow line, altitude above which or latitude beyond which snow does not melt in summer (Ramesht, & Shah Zidi, 2011). The temperature conditions quaternary reconstruct based on a permanent snowline altitude temperature difference compared to today. They also estimate the maximum expansion of tabs by ice moraines, the erratic rocks, valleys of glacial sediments and granulometry, and its height to consider as ice and water equilibrium line altitude. The water and ice equilibrium line is where ice flows entirely replace the water ice flows wholly replacing the water. The quaternary climatic changes, according to particular topography of Iran, have inherited different figures and landforms such as glacial circus, glaciers, and especially wanderer rocks. We cannot analyze by changing one element changes made; a complex mix of elements change been led to changes in the process and enduring numerous landforms. Any anomalies in each component s will cause defects and commotion in the whole system. 2-MethodologyAccording to the geomorphological landform, the remaining lake last is one of the methods of forecasting and estimating their condition. The Climatic factors role has particularly essential in the current situation of the Iranian domestic water hole. We used to examine the relationship between climatic factors and its effect on local lakes, dewatering of the temperature and precipitation data of the 50-year-old Asfazari database in cells 15 x 15 km (Masoudian, 2012). In addition to measurements of temperature and precipitation of central tendency, indexes used of dispersion indexes in statistical processes (Standard deviation and Coefficient of variation). Since the standard deviation is not used to compare the distribution of both characteristic varies with different units, the coefficient of variation (CV) used. Since most time, the Earth's surface has a temperature higher than the surrounding air, in this study were rainfall receiving below two degrees Celsius on the Basin. The coefficient of snow by reducing the temperature was estimated. With put, the factors in its relations appropriate amount of heat and precipitation determined in the Quaternary cold periods. We expect the coefficient of snow and temperature changes and precipitation decrease of 3, 6, and 9°C temperature for sub-study briefly. We cannot continuously study the effect of all elements and factors related to Quaternary climate changes. Still, we are trying to interpret the lake volume fluctuation due to climate change as a system through changes in temperature, precipitation, the coefficient of rain below 2°C, the ratio of variation coefficient of variation of temperature and precipitation.3-Results and DiscussionThresholds obtained show that the basin con ensures the exit of the lake that to be the average temperature of less than 15.78, average annual rainfall more than 215 millimeters, snowy coefficient more than 13 percent, the coefficient of variation of precipitation less than 40 percent and the ratio of difference of temperature more than 7.43. All basins inside Iran changed to a temperature not fit in the Quaternary. Status and evidence there are of lakes dewatering in the Quaternary do not match whit precipitation double and decline of temperature 6-12 degrees compared to the current conditions. So that line equilibrium of water and land could be the effects of the Quaternary terrace lacks by reducing three, nine, and 12-degree temperatures and increased precipitation. Change the line equilibrium of water and land cannot interpret with a temperature and precipitation changes alone, and causality of these changes in the line equilibrium of lakes water and soil must search in changes of precipitation regime and geomorphology of the region4- ConclusionsTo investigate the impact of climate parameters on the dewatering amount of water, we used primarily average of them. Accordingly, they are receiving basins Maharloo (375), Urmia (372), and Meighan (314 mm) maximum and basins Yazd (92), Bafgh (95), and Ardestān (114 mm) minimum of basin precipitation average. The basin has a higher temperature water demand more. If they receive Precipitation equal, drought intensity increases, the average temperature of pond, and their condition are such that allocated the lowest temperature to the basins of Urmia, Meighan, Gavkhoni, and the highest temperature to the lakes Qom and basins Jazmurian, Lute, the Bafgh and Qatruyeh. Basins of Urmia and Meighan have the best conditions. The basins Bafgh and Yazd have the worst conditions dewatering in terms of combining two elements of climate, temperature, and precipitation. These parameters alone will not be able to estimate the dewatering basins' performance reliable be due to the difference in average temperature and precipitation in the basin. Therefore, we used other vectors such as the coefficient of variation of climate (temperature and precipitation) and the coefficient of rain below 2°C. Investigation and compared the ratio of precipitation below 2°C on precipitation full in fourteen basin studies represents that the basins Meighan 21%, Urmia 20.8% and Qom 20.4% allocated to the most extensive and basins Jazmurian 1% and Qatruyeh 0.6% accounted to the lowest percentage of precipitation in below 2°C. To estimate sufficient rainfall in dewatering lakes, we can put number 40 in equation (2) instead of CVp, and we expect threshold precipitation of the basins. Number 40 is a threshold effect coefficient of variation Precipitation in dewatering lakes.Keywords: Quaternary, Climate, line equilibrium of water and land, Interior Lakes of Iran. 5-ReferencesFatahi, E., & Rezaei, T. (2009). Pattern of Daily Climate Circulation on Iran, Journal of Geographical Research, Isfahan University, No. 93: 45-74Masoudian, A. (2012). Iranian Climate, Sharia Toos Publications, Isfahan.Ramesht, M., Shah Zidi, S. (2011). Geomorphology Application in National, Regional, Economic, Tourism Planning, Second Edition, Isfahan University Press.
