Investigation and analysis of paleogeomorphology of Degh Sorekh desert

Doctoral dissertation in the field of natural geography, geomorphology

Abstract

The lakes of the end basins are very smooth and low-sloping surfaces in dry areas. As one of the most important geomorphological units of dry areas, these sunken pits, which are usually the place of accumulation of surface water, contain valuable paleogeomorphic and paleoclimatological information.

The Degh Sorekh Desert in central Iran is one of the playas that the history of its ancient environment along with the change and replacement of its environmental conditions have been illustrated in this research. In this way, the old Deq Sorekh lake had a hydrological connection with the Namak lake in the adjacent basin in the past flood periods. The proof of this, in addition to finding the existing terraces of 950 meters in both basins, has been confirmed by RS and GIS software and techniques.

In fact, the main goal of this research, in addition to identifying, separating and classifying the form units of Degh Sorekh playa based on the hierarchical theory, is to discover the ancient static relationships between the old Degh Sorekh lake and the salt lake, because the current conditions of a playa are the result of various factors affecting the playa and outside the playa. Therefore, in order to better understand and trace the events and conditions that happened on the playa, a comprehensive scientific analysis of the geomorphic features of the playa should be done. For this purpose, in addition to using related sciences such as geology, climatology, hydrology, mathematics, statistics, physical research tools such as topographic maps 1/25000, 1/50000, 1/250000, geological maps, DEM, IRS, ETM+, SID satellite images were used. Also, it was tried to use geographic information system and remote sensing technique and landscape compactness and geomorphological landscapes to morphological, hydrological and radiological modeling and by strengthening morphological imagination and thinking to provide the possibility of recognizing and analyzing different forms and faces of the earth in a three-dimensional coordinate system. It proves 1067 meters. In addition, the level of the terrace in the salt lake has been traced at a height of 950 meters, which is exactly the same as the level of the terrace seen at the edge of the Degh Sokh playa, as a result, according to the law of related vessels, these two lakes could have a surface hydrological relationship with each other at this level.

The investigation of the hydrological situation and the type of deformation of the drainage network in both playas showed that the waterways changed direction at the level of 950 meters. which indicates that this drainage network has reached the old base level.

Key words: Degh Sorekh playa, paleogeomorphology, static relationships, eyes, modeling.   

Chapter 1

Research overview

Although the bareness of dry areas and especially playas is considered as an obstacle from the point of view of biological and plant sciences, but from the point of view of geomorphologists, the natural bareness of these areas is considered as a privilege. The reason is the reduction of the form and processes that have limited the biological activities. This allows the geomorphologist to analyze the history of these areas with more accuracy and concentration by removing additional factors or cleaning them.

On the other hand, we know that desert environments, especially pits and deserts in Iran, are usually located at the end of the basin and are somehow located at the point of accumulation and concentration of any pedological system. As a result, due to the influence of changes in other parts of the basin over time, they can be a suitable source for paleontological studies. Because a collection of evidence and environmental changes, whether in the playa environment (hole) or outside it, can affect the playa environment changes with hydrological networks and even underground systems and with the help of changes in balance and sediment volume. The feature of Playa is its low level compared to other parts of the basin. The result of this situation is that this environment is more influenced by the surrounding high levels. In the morphic logic of the earth, which is a function of natural physical and mechanical laws, it shows the agency and dominance of high levels over the changes of flat and low levels, therefore, according to the above explanations, it can be said that the playa environment is a readable notebook of environmental changes (climatic, pedological, hydrological and morphological changes). As a result, the importance of studying dry areas is not hidden from anyone.. In this regard, we tried to achieve more reliable and documented results with computer techniques and tools and to reduce the machine error and to achieve a more accurate and comprehensive analysis by increasing the computational and graphic accuracy. 1-2- Description and statement of the research problem. Quaternary has passed. Due to the adjustment and reduction of the speed of morphogenesis in such territories, the stability of ancient Quaternary forms has favorable conditions. So that single-origin and multi-origin shapes, as well as ancient forms such as headlands and playas, show the dominance of diverse and different processes governing the region in the Quaternary bed (Seif, 2014: 3).

Degh Sork Desert in the east of Ardestan is considered as one of the playas of central Iran, which contains valuable paleogeomorphological information as a geomorphological archive. It lies in itself. Therefore, the study of the paleogeomorphology of this region helps us to explain and reconstruct the governance of processes and forms as well as the change and replacement of its environmental conditions, and in this way to analyze the ancient history of the Quaternary environment of Degh Sorekh playa, but the introduction to knowing the paleogeomorphology of the region is to prepare maps of geomorphic units. Therefore, in this treatise, using ETM+, IRS satellite data, and in some cases ASTER and geographic information system, the units, types, facies and even sub-facies of Degh Sorekh desert were identified. Then, on a macro scale, the paleogeomorphological relationship between Degh Sohkh and Namak Lake was investigated as a past climatic heritage; Because the main hypothesis is based on the fact that during the Quaternary period, the two playas of Degh Sorekh and the Salt Lake had a hydrological connection with each other. On the other hand, one of the important and effective factors in changing the shape of landforms and disconnection or connection of phenomena with each other in Quaternary tectonics is Jenba. Therefore, it was decided to trace the effects of neotectonic developments in the Deq Sorkh water basin (including the four sub-basins of Bad-Khalidabad, Toruq-Abiazen, Ardestan and Deq Sorkh) by using geomorphic indicators and identifying, analyzing and observing the existing geoforms in the study area.   

Proofing the hypotheses in the long term will be possible through climatic and geomorphic evidence and everything that helps in explaining this hypothesis, and short-term changes will be analyzed through the processing and interpretation of past and present satellite images with the help of additional information such as meteorological and sediment statistics. and geomorphological territories help. Features such as the application of various processes on digital data, general visibility and macroscopic view of the territory, as well as the multi-spectral and multi-temporal nature of digital satellite data have increased the recognition and differentiation of geomorphological levels and territories and enable the geomorphologist to identify and analyze geomorphological units and levels by analyzing digital satellite data of gauges. Therefore, this research aims to use the technique of processing satellite images to prepare geomorphological maps of Chale Degh Sorekh, and then analyze the geomorphic territories of the studied area and provide geomorphological maps of the region with a series of fieldwork and image processing. This is while the state and conditions of the paleogeomorphology of the study landscape have been investigated and analyzed using methods, techniques and field operations. These areas have been because access to these areas has been difficult and limited due to its special conditions. Playas, as one of the geomorphological units of arid regions, have experienced a complex and different climatic-environmental history in the Quaternary. In these territories, ancient forms have a lot of diversity, therefore, knowing the geomorphological changes of the fourth era and explaining the cause and manner of their occurrences will lead to a better understanding of the environment and how it was formed in the past, which will lead to a reasonable and sustainable use of the environment.