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:: Volume 2, Number 8 (9-2017) ::
کواترنری 2017, 2(8): 353-366 Back to browse issues page
Geomorphology of karst in Alamut carbonates formations, North Qazvin
Doctor Parviz Ghazanfari , Mr Mahdi Bakhtiari, Doctor Mahdi Tajabadi
Abstract:   (141 Views)
 
Identification of geomorphological phenomena that were created by the dissolution can help to identify the karst systems. Hence, karst geomorphology is usually the first step of study. Processes of Karstification on the one hand cause problems in carrying out civil projects, and on the other hand it can help in the exploitation of water resources from hard formations and development of the geotourism industry. Karst develops in many types of rock, including limestone, dolostone, gypsum, salt, quartzite, and some others. These rocks, subjected to different climates, assume many morphologies and landforms. Limestone purity (%CaCO2) is one of the most important controls on karst development. Karst landforms develop best on pure, dense and thick limestones and marbles. In karstification processes three parameters of lithology, climate and fracture are more important than others such as pedology, vegetation cover and topography. Among sedimentary rocks, salt rock has maximum dissolution rate. After that sulphate rocks such as gypsum, shows 10 times more Chemical Denudation than limestone. Limestone also has more dissolution rate compare it to dolostone. Bedding planes and fractures (joints and faults) are of the greatest importance because they host and guide almost all parts of the underground solution conduit networks that distinguish the karst system from all others. The availability of water is the key climatic factor in karst development. It is certainly the principal variable controlling total denudation by dissolution. Alamut Valley is located in north of Qazvin provenance and Central Alborz structural zone. The area of Alamut is 1866 Km2. Average rainfall in this area is more than 300 mm and average of temperature is under 14 OC. Carbonate rocks of Alamut are under highly dissolution because of climate condition and also high density of fractures. Rock units in this area include formations of Paleozoic, Mesozoic and Cenozoic Era. These formations consist of various clastic, carbonate and evaporite sedimentary rocks, as well as a variety of igneous rocks. The most important of carbonate formations of Alamut are Soltanieh (Cambrian), Rute (Permian), Elika (Triassic), Lar (Jurassic) and Tizkuh (cretaceous). In this research, potential of Karstification evaluated after field studies and sampling of carbonate rock units and compare them from the point of view of development of karst landforms formations. After sampling Carbonate rocks and preparing thin sections and also staining using Alizarin Red S for identification dolostone with calcite, they were studied under petrographic microscope. Investigation of remote sensing was performed by satellite images Landsat using ILWIS software to achieve separation and calculation of area of carbonate formations, as well as digital elevation model. The region is located in an area with tow climatic regimes of Mediterranean rainfall (semihumid) and Siberian high pressure (cold-ultracold). Water is the main factor of karst development. The most important of karstic landforms in the area are Karren, dissolution pit, vug, cave and karstic springs. Varieties of Karrens are microkarren, karren, runnel Karren, rill Karren, grike, rain pit. The caves of Alamut mostly identified in Ruteh Formation, for example: Sefidab cave in north of Sefidab village and Vali cave in near Gashnehrud. Angul cave in north of Dinak village also was formed in Elika Formation. The most important parameters casual Karstification of carbonate rocks in Alamut area are: purity, thickness, outcrop area and time of exposure of rock units, also rainfall, temperature and fracture intensity. Because of more rainfall and lower temperature, the north of Alamut valley shows more intensity of Karstification compare to south part of area. Based on combination of all field work and remote sensing data, the intensity of karstification in the area of Alamut in order from high to low are: Rute, Elika, Tizkuh, Lar and Soltanieh formations. Lar Formation shows maximum intensity of karstification in east of central Alborz zone, but in west of Alborz zone (Alamut) it doesn't have less intensity of karstification among all carbonate rock units. This difference is because of less thickness and outcrop of Lar Formation in study area. Based on geomorphic classification, Alamut can be classified as merokarst.
Keywords: Central Alborz, Geomorphology, Karstification, Qazvin
Full-Text [PDF 2121 kb]   (26 Downloads)    
Type of Study: Research | Subject: Special
Received: 2017/09/10 | Accepted: 2017/09/10 | Published: 2017/09/10
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Ghazanfari P, Bakhtiari M, Tajabadi M. Geomorphology of karst in Alamut carbonates formations, North Qazvin. کواترنری. 2017; 2 (8) :353-366
URL: http://journal.iranqua.ir/article-1-116-en.html
Volume 2, Number 8 (9-2017) Back to browse issues page
فصلنامه کواترنری ایران Quaternary Journal of Iran
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