B Ebrahimi; A Seif
Abstract
This study has been carried out with the aim of mapping karst and evaluation of potential karstification of carbonates rocks in Zagros. One objective of this paper is a spatial evaluation of karst development in Zagros considering role of the chief factors affecting karst development. The main considered ...
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This study has been carried out with the aim of mapping karst and evaluation of potential karstification of carbonates rocks in Zagros. One objective of this paper is a spatial evaluation of karst development in Zagros considering role of the chief factors affecting karst development. The main considered factors are those classified by White (1988) into three driving forces (i.e., chemical driving force, physical driving force and hydrogeological setting). Precipitation, temperature, relief, rock type, tectonic setting and stratigraphic thickness of soluble carbonate rocks are the main factors classified to describe the mentioned driving forces. In this study, precipitation and temperature are represented by the chemical weathering conditions during the modern and glacial periods prepared on the basis of Peltier's graphs. All data are mapped, classified, weighted and managed in separate layers in GIS environment. The Karst Index (Ki) is introduced to define the modeled degree of karstification computed by proper combination of six weighted layers and the final theoretical karst map of Iran is prepared based on the ranked Karst Index. According to the combination method, values of Ki could be in a range of zero to 400. The classified theoretical karst map shows that out of 109,313 km2 of carbonate units (25 % of the surface area of the study area) about 34212 km2 (31.3% of carbonate rocks) have very low to low potentials for development of karstic features. About 61272 km2 (56% of carbonate rocks) have moderate potential and about 13829 km2 (12.7% of carbonate rocks) have high to very high potentials for karstification. In other words, 68.7% of the carbonate rocks are carbonate rocks with moderate to high potentials for karstification. Densities of caves and karstic springs are the main and the most important geomorphological features used to check the calculated degree of karstification. For this purpose, complete inventories of caves and springs in Zagros were made. 64 caves and 129 springs (with discharges above 10 l/s) occur in rocks in areas of very low to low potentials for karstification. About 132 caves and 300 springs fall in the moderate class and 51 caves and 162 springs in areas with high to very high potentials for karstification. Cave densities are 0.0014, 0.0020, 0.0022, 0.0036 and 0.0039 caves per square kilometers for very low, low, moderate, high and very high classes respectively. In addition, densities of springs are 0.0035, 0.0039, 0.0049, 0.0111 and 0.0131 springs per square kilometers for very low, low, moderate, high and very high classes respectively. In other words, densities of caves and springs show a good correlation with the evaluated karstification.
R. Sharifi Najafabadi; M. Moairy; H. A. Ghayoor; H. Safaei; A. Seif
Abstract
One of The important subjects about Zagros mountain range is the lack of coordination between its drainages and geologic structure. This subject on Zayandehrood drainage system has become one of the most challenging discussions and three different theories have been proposd . To remove these disagreements ...
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One of The important subjects about Zagros mountain range is the lack of coordination between its drainages and geologic structure. This subject on Zayandehrood drainage system has become one of the most challenging discussions and three different theories have been proposd . To remove these disagreements and to achieve a general conclusion, this basin and two basins of Azna and Kakolestan at a distance of 62 and 85 km form its north east limit were studied exactly in library and in the field. With referrer to different evidence obtained from the condition of river terraces, lake sediments and fossils, cirques and glacial sediments and active tectonic, it may be concluded that during Pliocene the Zagros drainages have been flowing toward Persian Gulf, but this drainages have been trapped because of the activity of Main Recent Fault at late this period or Early Pleistocene and formed some lakes. Later as the result of some processes that most of them have been of tectonic origin, the bed of these lakes were disintegrated and the water stream was flowed in Kakolestan and Azna’s basins at the previous direction and in Zayandehrood basin at the revers direction.
