Middle Holocene settlements at the western Foothills of Zagros Mountain in their Geographical setting (Survey of the relation between environmental setting and Geographical factors in the formation of the 4th millennium and early 3rd millennium BC si

Introduction The western foothills of the Zagros Mountains as a border area located between highlands of Iran and Mesopotamian lowlands, considered as an important archaeological study area. this area as a contact zone not only helping in better understand of the cultures located between this two different landscape of Near East (Mesopotamian lowlands and Zagros highlands), but by studying their formation process and the issues influenced it, the regional and interregional regional communication pathways could be synthesis more obvious. In this study, based on landscape archaeology and analytic methods and using the Pierson methods, the proportion of different variance related to formation of archaeological sites were analyzed. At the end we identified 3 settlement patterns and we find that the 3 key issues of access to water sources, the kind of lands and access to the roads are the main issues that influenced the formation of sites.    Materials and Methods The data of this research were collected based on archaeological survey in 2015, and in the next step other information was collected by documentary method. This research is a fundamental study and in terms of method is part of historical-analytical research. The authors by using Pearson’s correlation statistical method and ecological approach in archeology, will try to evaluate the role of various factors in locating and distribution of the ancient settlements of Sar Pol-e Zahab area. This study tries to answer the question that how were the settlement patterns of Sar Pol-e Zahab region as the strategic region between the Iranian heights and the land of Mesopotamia in the fourth and early third millennium BC and what variables were the affecting factors in locating of these settlements?   Results and discussion In our survey of mention plains, it was identified totally 14 sites of the fourth millennium and early third millennium BC. that their cultural materials indicate their belonging to the Uruk and Jamdat Nasr cultures. These include 13 sites in Zahab plain and one in Beshiwa plain, but no site of ​​the mention periods have been identified from the survey of Patagh and Qaleh Shahin plains. We used the Cluster analysis to know the pattern of settlements of the fourth and early third millennium BC and understanding and the better analyze of distribution of archaeological sites of this period and to find the relationship between the distribution patterns of the settlements and environmental variables. This means that environmental factors such as altitude, distance from water sources, size and direction of slope and the type of modern vegetation was considered as an independent variable and the dimension of ​​ancient sites was considered as a dependent variable and the relationship between the nature of the sites and various factors has been measured by using of Pearson’s correlation method. Based on this research, three types of settlement patterns were identified and it was found that three factors of access to permanent water resources, type of land use (soil type) and accessing to main roads had the main impact on the formation of settlements in the mentioned region.   Settlement pattern A Settlement pattern A, which has the largest number of sites, includes 8 sites. altitude level for these sites is between 510-630 meters. The sites are located between 50 to 1500 meters from permanent water sources and have a size between 7350-18020 square meters. All these sites are located in suitable lands for agriculture. The distance between this group of sites is between 30 to 4170 meters.   Settlement pattern B In this pattern, there are three sites larger than two hectares called Maikhan, Tape Kaleg and Sarab Zahab-e Ghaderi, and this case is probably more related to proximity to water sources and locating along communication routes. These sites with dimensions between 23,100 to 24,000 square meters are located at an altitude of 530 to 570 meters above sea level. The mentioned sites are located at a distance of 5 to 810 meters from the modern main water sources. These sites are located in land with agricultural use and a slope of 4%. Regarding to the location of these sites in the landscape of the region, their large size and proximity to the communication route it seems that comparing to the other groups, this group are probably strategic and important sites and due to the proximity to the main communication routes It is possible that their inhabitants are engaged in regional trade in addition to agriculture and animal husbandry.   Settlement pattern C The sites that are located in this cluster and settlement pattern are three sites of Shahouk, Sarab-e Kuwang 1 and Sarab-e Kuwang 2. Altitude of this group of sites is between 520-525 meters and they are located at a distance of 20-75 meters from permanent water sources. These sites have size ​​about 2770 to 4120 square meters and comparing to the other sites are located in a cluster due to their small size. In terms of land usage, the mentioned sites are mostly located in agricultural lands and the only difference between these sites and group A is their very small size and their location on the border of plain and adjacent to water resources (springs). Regarding to their location and their low dimension, as well as their small size of their deposits, it seems that these sites are probably seasonal sites. These sites are formed at a closer distance to the hills and foothills than other groups, which somehow indicates exploitation of heights. The small size of the sites and their distribution based on a linear pattern along water resources that are also located in low-fertile lands and have good access to pastures, may be a clue of livestock livelihood in this area.   Conclusion As the clustering of the sites shows, the pattern of spatial distribution of the settlements of the fourth and early third millennium BC in the Sar Pol-e Zahab area is divers. The reason for this diversity is largely due to environmental and natural factors. The distribution of settlements in this region is more affected by environmental factors such as water and fertility soil resources. On the other hand, these sources are not the only effective factors, but probably another factor such as communication routes has been effective in this distribution. In the analysis of the patterns of the sites of the Uruk period in Sar Pol-e Zahab area, three settlement patterns were identified that according to the location and landscape of the region, the sites of each cluster probably have different nature and functions. Environmental conditions required that in addition to the seasonal function of the sites in terms of agricultural and livestock livelihoods, due to the passing of one of the most important trade routes of the ancient world, the inhabitants of some settlements in this area could play a role in trade. Existence of permanent river Dalashir in Zahab plain, as well as several permanent and full of water mirages including Sarab-e Qara-Bolagh, Sarab-e Seyed Sadegh springs and to some extent Zahab springs with suitable slope of plain and agricultural fertility suitable soil formed Suitable conditions, as well as it is now, for formation of settlements in the region Based on agriculture which they have been able to organize water-based agriculture in the lands around the settlements by utilizing the water of mirages and springs. If this perception be correct, the possibility of irrigated cultivation can be mentioned as the most important factor in the formation of these settlements in Zahab plain. This argument is reinforced by the density of settlements in the fourth millennium BC of Zahab plain and the lack of settlements of this period in Qaleh Shahin plain and the existence of only one site in Beshiva plain.