The role of lithology in the formation of inselbergs in Safi Abad plain in northeastern Iran

A B S T R A C T
The morphology of each region is related to its landforms, the morphology of flat areas is related to inselbergs. The presence of inselbergs in desert and dry areas gives a special appearance to the morphology of these areas. The study of these landforms and the effective factors in their formation is considered a necessity in terms of regional development. According to the studies, various factors play a role in the formation of inselbergs, and the role of lithology seems to be more prominent. In this research, which was conducted with the method of field and library studies, we identified 18 inselbergs in Safi Abad plain and by studying them, we came to the conclusion that the inselbergs of this plain are mainly formed in sedimentary rocks such as limestone, conglomerate and sandstone. Among the geological formations, the largest and most diverse inselbergs in the Safiabad plain are formed in the mass conglomerate formation with good hardening because this formation is the most widespread in this plain. But the most typical inselbergs of this plain are formed in thick layered limestone. Because this formation is more resistant to erosion. Lar Formations including Limestone and Thick Limestone’s to Mass Dolomite and Delichai Formations have also played an important role in the formation of inselbergs in this plain. Although the extent of these formations is not significant, but due to their significant resistance to erosion and being far from these processes, they have caused the formation of evolved inselbergs in this plain
Extended Abstract
Introduction
Inselbergs are ridges with a height of less than 500 meters formed with a steep slope in the plains. Their resistance to erosion has caused them to be considered capable players in the morphology of arid and semi-arid regions. Due to their uniqueness in desert areas, these areas are of interest to tourists, and the economic situation of these areas can be improved by attracting tourists. The prominence of inselbergs in desert areas has caused researchers to pay attention to their studies, the most important of which are the studies of Pye in Kenya (1984), Nenonen in Finland (2018), Luiza in Brazil (2021), Laetitia in Africa (2019), and Mashaal in Egypt (2020). Although the conditions for inselberg formation are available in some areas of Iran, and these landforms have given a particular face to the morphology of this country, no significant study has been done on them so far. This research attempts to investigate the role of lithology in inselberg formation in Safi Abad Plain by using library and field studies.
 
Methodology
Safi Abad plain in the northeast of Iran and North Khorasan province and in terms of geographical coordinates between 36-˚ 48-05 to 36-22-55˚ North and 37-57˚ East to 36-˚ 37-08 It is located at 57-58-11 east. Field and library studies were used to study the inselbergs of this plain. The entire region was surveyed in 2 years in the field studies, and 18 inselbergs were identified. Then, the location and extent of their expansion were determined. In the morphometry that was done as a survey, the minimum height, length-to-width ratio of inselbergs, and their distance from each other were measured with GPS. The study of the concepts, definitions, and effective processes in inselberg formation was done with the library method. The maps of this research were drawn with Adobe Illustrator software.
 
Results and discussion
Inselbergs are diverse in terms of morphology; in the studied area, 18 inselbergs were identified, most of which are mixed. Most of them are rocky and have less vegetation. Regarding lithology, inselbergs are particular forms of igneous and metamorphic rocks, but some are also formed in other rocks. Although lithology plays an essential role in inselberg morphology, it cannot be claimed that inselbergs formed in the same formation have the same shape. Although the dominant lithology of the Safi Abad plain is formed from sedimentary rocks, due to the different resistance of its formations, the height, shape, and slope of the inselbergs of this plain are different in different parts of the region. The difference in these characteristics has caused the different shapes of the land in this plain. According to the studies of the most resistant formations of Safi Abad plain against erosion, limestone is a thick layer of chert mass formed due to the resistance against the erosion of the complete inselbergs.
After this formation, the Lar formation consists of fine-grained uniform dolomitic limestone with thick to massive layering, which is more resistant; that is why many inselbergs in the region have formed in it. The third formation in terms of resistance is the Apsin-Albin unit, which includes orbitolinate limestone and thick limes to a mass of dolomite. Although this unit has a small area, its inselbergs are closer to typical inselbergs. In terms of area, most of the area is composed of mass conglomerates with good hardening. Due to the different effects of this formation from different processes, its inselbergs do not have the same morphology. The inselbergs formed in this formation are in the middle part of the high area, low in the southern part, incomplete in the western part, and incomplete mushrooms in the path of the Gerati River. After this formation, gray shales are the most resistant to erosion. This formation, which belongs to the Jurassic period, has formed a large part of the northeastern inselbergs. The alternation of limestone and marl in the Delichai formations in the middle part of the region provides the basis for the formation of mushroom-shaped inselbergs in the future.
 
Conclusion
Safiabad Plain is in the northeast of Iran, and in terms of geomorphological units, it is part of central Iran. Inselbergs form part of the morphology of this plain. In this study, 18 inselbergs were identified in this plain, and their detailed study showed that their primary skeleton was established by tectonic activities in the Devonian to Miocene period with the formation of Posht Bahram mountains. It was formed when the tectonic activities calmed down and in opposition to the lithology and erosion of the inselbergs of this plain. In terms of lithology, the well-hardened conglomerate formation covers nearly 47% of this plain, and due to its large size and different distances from erosion processes, various inselbergs have been formed in it. The southern inselbergs formed in this formation have a regular shape due to wind and blue erosion. In contrast, the middle inselbergs have an incomplete shape due to the distance from higher erosion, and the western inselbergs have an incomplete shape due to the superiority of blue erosion. Another formation that plays a vital role in this field is Lar Mei Formation. Although this is the second formation in terms of size and strength, many inselbergs have formed in it. The Shemshak formation is placed after the Lar formation in terms of resistance. This formation has caused the formation of chain inselbergs in the northeast of the region. The most typical inselbergs of the region are observed in the thick layered limestones of the formation (Maastrichtian). Also, this research found that inselbergs may be formed in all flat areas of the world and even in sedimentary formations. However, the inselbergs formed are far from those formed in tropical regions' igneous and metamorphic formations.
 
Funding
There is no funding support.
 
Authors’ Contribution
The authors contributed equally to the conceptualization and writing of the article. All of the authors approthe contenttent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
The authors declared no conflict of interest.
 
Acknowledgments
 We are grateful to all the scientific consultants of this paper.