عنوان مقاله [English]
In spite of the excellent results achieved by international scientific community, the topic of quantitative evaluation of geodiversity is still an open issue. The complex geological and geomorphological environment, related to the diversity of topographic and climatic characteristics leads to the dynamics and evaluation of natural systems.
Geodiversity studies include key cognitive methodological issues such as those used for scientific observations (scale, ranking, sampling, measurement, and errors) in geomorphology.
Methods for assessing geodiversity are quantitative, qualitative and quantitative-qualitative. The study of geodiversity on a regional and local scale with traditional mapping techniques is often a difficult and costly process and statistical modeling, which is one of the quantitative methods, is used as a suitable approach in the analysis and mapping of geodiversity. The accuracy of output maps of geodiversity depends on the scale and accuracy of input data. The purpose of this study is to investigate the indicators of diversity in the Dorungar River basin.
the Dorungar River basin With an area of 2456.18 Km2 is located in the central section of the Kopeh Dagh mountain ranges, northeastern Iran. The study area is located between 37° 11΄ to 37° 42΄ North latitudes, and between 58° 11΄ to 59° 27΄ East longitudes.
The methods applied in this study can be divided into two main types, namely(1) descriptive-analytical and (2) quantitative, which has been done using an ASTER GDEM with 30*30 meters resolution, geological maps of 1: 250000, Google Earth satellite imagery, land use maps, office studies and field observations. We used the modified index of Serrano and Ruiz-Fleno (2007) to assess the amount of geodiversity. In the first stage, based on the components in the formula, the land use index, geomorphology, and topographic layers were extracted. In the second step, the required maps were prepared and produced by ArcGIS software and compared with the images obtained during fieldwork.
Results and Discussion
Geomorphological evidence of the study area indicates the continuation of neotectonic activities during the Plio-Quaternary period. in other words the study area is been located in an active tectonic zone which is resulted in an abundance of structural landforms. In addition, tectonic deformations and structural landforms control drainage patterns and channel bed streams. Therefore, this paper aims to investigate the geodiversity of the study area to lead to better planning for environmental protection. Our results found that 60% of the study area has low, 29 % moderate, and 11% high geodiversity, respectively.
The results of previous studies have shown that the index of geodiversity is consistent with mountainous areas and this index is a function of the number of non-living elements and is directly related to roughness. The study area can be considered high geodiversity due to its mountainous nature and high number of geomorphological features.
Geodiversity assessment is a new attempt to achieve quantitively and qualitative components of the physical environment to compare their frequency and variability in the landscape phenomenon. the study of Quantitative geodiversity enhances the understanding of diversity in each unit and provides it possible to identify the role of different variables and their importance. In addition, geodiversity has economic, practical, educational, and aesthetic value and unique archival diversity of climatic and environmental conditions. The results showed that in the geomorphological map, low areas have less energy and this causes the role of any morphogenic factors to be minimized and Get the lowest score for diversity. In fact, These regions are regions with low gene diversity (homogeneity) and in other words, uniformity in geomorphic genes or processes, these systems are very vulnerable to environmental changes. The high diversity was related to mountainous areas with high sensitivity and low elasticity, and in this area, the heterogeneous system had high and complex gene diversity In areas with high land use scores, the impact on natural areas with unprincipled exploitation is low and land degradation is less. In areas with low land use scores, human impacts were maximal due to the disappearance of geomorphic forms and landforms and there was the most land use degradation.
In the geological map, class I, which includes igneous and metamorphic rocks, has the lowest score related to geodiversity. The class with moderate diversity is related to sedimentary rocks. Class III includes calcareous and dolomitic formations and due to the high sensitivity of this type of rocks to dissolution, their importance in the characteristics of roughness and the formation of special shapes has the highest diversity points.
Therefore, with the study of lithology units and geomorphology landscapes, we can focus more on issues related to sustainability and environmental protection, especially in the study area because of having three protected national parks in Iran. Quantitative geodiversity study is a new method that leads us to understand the structure of terrestrial phenomena, their distribution, and the relationship of these phenomena with the landscape of the region.
According to previous researchches, it can be said that considering the above indicators will give acceptable results about the preparation of diversity maps.
Keywords: Geodiversity, Dorungar river basin, Geoheritage, Environmental conservation.