Considering and Analyzing Geomorphic Indexes and Their Relation with Active Morphotectonics in Arid Zones (Case Study: Ardestan Palays)

Neo-tectonics is the study of horizontal and vertical motions of Earth’s crust originating from the late periods of Neogen and Quaternary. Many researchers have defined tectotecnic as “the beginning of Earth’s crust motions after the earliest orogenic phase” (Stipancikova et al., 2008, p. 68). Since there is no possibility of having access to the old seismic reflection data in many areas and some methods of measuring active tectotecnics are very expensive (seismic methods), the use of morphometric indexes to detect and determine the active tectonics is of great importance. Therefore, “geomorphic indexes are useful materials to analyze Earth’s forms and to measure the tectotecnic activities in many areas” (Guarnier & Pirrota, 2008, p. 265).
By studying the geologic maps of the region, we realize that the study area is located in the central part of Iran and the tectonic zones of central Iran. Building blocks in this part of Iran are the result of young Alpine tectonic process. The general trend in the main buildings in the geological areas is in line with the general trend of tectonic zones in Sanandaj - Sirjan and Zagros.
The area has a complex tectonic faults due to numerous conditions, including Doruneh Fault in the north, Nain Fault, the tissue in the East and its most important fault, namely Rastgard Fault in Qom, Zefreh Fault located along the north-west and south-east, which crosses a tectonic valley in the city of Natanz and probably plays a role in the development of Eocene magmatic and volcanic activities. The other tectonic characteristics of Qom -Ardakan is located in the southern part of the study area. From the viewpoint of tectonic areas, the troughs have been developed during two structural stages in Oligo-Miocene and Pliocene periods.
Theoretical Framework: Geologists and particularly geomorphologists use geomorphic indexes to analyze the Earth forms and to measure tectotecnic activities in various areas of the world.
Geomorphic indexes in all over the world, especially in arid and semi-arid areas have been investigated by many researchers, including Bull and Mcfadden (1997), Wells (1998), Ramirez-Her (1998), Couong and Zushiewicz (2001), Silva (2003), Chen (2003), Zovili, Konstantinidi, and Koukouvelas (2004), Verrious, Zigouri, and Kokkalas (2004), Harkins, Anastasio, and Pazzalia (2006), Guarnierri and Pirotta (2008), El Hamdouni, Irigary, Fernandez, Chacon, and Keller (2008), Kale and Shejawalker (2008), and Gurbus and Gurer (2008).
In this study, first the library research method was used to collect the articles, books, and internal and external sources. And the topographic maps 1/50000 and sattelite picture ETM 2008 were also used to consider and limit the area. Meanwhile, geology maps 1/100000 was used to extract faults layer and DEM boundation for many measures. As for the analysis process, 11 quantitative methods measuring the base of tectotecnic activities (depending on the geologic, lithologic, and hydrogic conditions) along with 15 qualitative methods were used for tectonical descriptive analysis (see Tables 1 and 2). In the next phase, the quantitative methods in relation to the studied basins were calibrated using the basic information. As such, we attempt to make sure that each of the methods conforms with the considered boundation and that we use parameters which other researchers of geomorphology have used less frequently. In the end, we attempt to measure indexes, basin form, bulk of basin surface, p (trachom of superfical floodway), flexibility (BR), hypsometri of basin (HI), and standard microfacies (SMF) through an experimental method using the GIS ARC 9.3 software.
In this study, the study area is divided into 4 subbasins due to the different geological and geomorphologic features of the Degh-sork watershed and the existence of three clear geomorphologic unites (mountain, plain, and palaya). Then, the tectonic activities of the area were evaluated by using 6 geomorphic indexes based on the morphology of the basin and the drainage network. In doing so, the index of Relative Active Tectonic (Lat) was used.
Conclusions & Suggestions: The relation of Lat=S/N includes parameters which can be measured in the following: “Lat= the index of Relative Active Tectonic, S= the total classes of the measured indexes of geomorphic activities, and N= the number of measured indexes of different classifications of Lat index” (Hamdouni et al., 2008, p. 171), which are measured in the following: 1