عوامل طبيعي تاثيرگذار بر الگوي پراكنش سايت ‌هاي باستاني دشت سيلاخور در استان لرستان

Natural Factors Affecting the Distribution Pattern of Archaeological Sites in the Silakhor Plain, Lorestan Province

اهداف: سايت ‌هاي باستاني به بقاياي استقراري گفته مي ‌شود كه در دامنه و كوهپايه ارتفاعات و در شيب ‌هايي كه جهت اسكان يا تدفين و غيره مناسب بوده است، واقع شده ‌اند. هدف از اين تحقيق، بررسي ارتباط بين عوامل طبيعي(ژيومورفولوژي، توپوگرافي و منابع آب) و شكل‌ گيري سايت‌ هاي باستاني دشت سيلاخور در شمال شرقي استان لرستان به‌عنوان يكي از مناطق فعال تكتونيكي ايران است. روش: روش تحقيق توصيفي- تحليلي و با استفاده از ابزاري مانند نقشه ‌هاي توپوگرافي، زمين‌شناسي، ژيومورفولوژي و قابليت هاي تحليل مكاني نرم‌افزار Arc GIS انجام شده است. يافته ها/ نتايج: يافته هاي تحقيق نشان مي دهد كه تفاوت‌ هايي در ار تباط بين دوره تشكيل سايت ‌ها و عوامل طبيعي مشاهده مي ‌شود به‌‌طوري‌كه از ?? سايت با ارتفاع بيشتر از ???? متر، ?? سايت مربوط به دوره تاريخي است. همچنين هر يك از عوامل طبيعي مورد مطالعه، در سه دوره تشكيل سايت‌ ها، متفاوت عمل كرده اند. نتيجه‌گيري: نتايج نشان مي ‌دهد كه شكل‌ گيري سايت‌ هاي باستاني، در سه دوره تاريخي، در دشت سيلاخور، به دليل وجود توپوگرافي هموار و منابع آب كافي بوده است. واحد دشت آبرفتي به دليل وجود منابع آب، خاك حاصلخيز و ارتفاع و شيب كم، داراي بيشترين و مناطق مرتفع و كوهستاني به دليل محدوديت‌ هاي طبيعي، داراي كم ترين تراكم سايت ‌ باستاني مي باشند.

1. INTRODUCTION As far as the layout patterns of ancient settlements in an area are concerned, the role of environment and its context in a geographical perspective are of critical importance. Various geographic factors are involved in positioning, formation, and distribution of human settlements. Archeological sites are the remains of the ancient settlements located on the foothills of mountains and slopes that were suitable for settlement, burial or other uses. The vast Silakhor plain located in the northeast of Lorestan province is one of the first human settlements after the development of agricultural. Naturally, with the advent of agriculture, immense plains like Silakhor have become the subject of growing attention in the east of Lorestan. There are 283 ancient sites in Silakhor plain, indicating that thousands of people used to live in this area in the first and fourth millennium BC. These hills were home to small and large settlements built on the low plains of Silakhor. They not only provided quick access to agricultural land, but also protected the residents from animals and humans. In fact, the geographical environment of the plain was the ground for the interaction of local communities with the surrounding environment, playing an important role in the aggregation and dispersal of ancient settlements. As such, the question arises as to the relationship between environmental factors and the distribution of archaeological and historical sites. The purpose of this study is to investigate the relationship between environmental factors and the distribution of archaeological sites and to identify the most important factors involved in the formation of sites in the study area. 2. METHODOLOGY The research method is descriptive - analytical and a variety of tools such as topographic maps with a scale of 1:25000 and geological maps with a scale of 1:100,000 along with TM images of Land sat satellite were used to provide elevation classes, slopes, geomorphic landforms and geological formations. The data on water resources was collected from regional water company of Lorestan and the information about 283 archaeological sites of Silakhor plains was taken from Cultural Heritage Administration. The sites were classified based on their formation and the distance of sites from the river layer was obtained after preparing raster layers using the Distance command. The level of groundwater was calculated based on statistics of piezometric wells in the area and ordinary spherical kriging interpolation method. Then, command the numerical value of each site relative to natural factors was extracted and categorized using Extract value to point command. After providing the required layers, the relationship between each natural factors and distribution of archaeological sites was examined. 3. RESULTS & DISCUSSION The analysis of archaeological sites in terms of environmental factors such as geomorphic units, sites elevation above plain level, site elevation above sea level, slope and water resources were examined in third Islamic, historic and prehistoric periods. Most sites were located on alluvial units. The overlapping of archeological sites shows that a great part of the plains is covered by alluvial plains and about half of sites have expanded in this unit. In all three periods of site formations, most sites were established on alluvial units. The altitude study of ancient sites relative to the height of Silakhor plain shows that sites are approximately located at a height of 0 to 48 m from the plain level. The elevation of sites relative to Silakhor plain indicates that different geomorphological processes are at work at the level of plain, geological formations and heterogeneous lithology. Also, high sites are indicative of the sequence of cultural layers from different historical periods in the plain, which show permanent settlements in the area. The height analysis of Silakhor plain reveals that of 283 existing sites, 185 cases are 1520-1296 m in height. In the historical period, height was an important factor in the formation of sites while in the Islamic era, sites developed in areas with lower elevation. The slope analysis suggests that in all three periods, sites were formed in areas with low slope. Statistical analysis shows that there is a direct relationship between topography and distribution of sites. Study of surface water resources reveal that in plains, sites have developed in the proximity of rivers. Islamic period sites are mainly located away from drainage network, which is probably due to large floods. The closeness of sites to groundwater and surface water supplies indicate the importance of this factor as a settlement for human begins. 4. CONCLUSIONS & SUGGESTIONS The analysis of archaeological sites in the Silakhor plains suggests that environmental conditions of the plain in the past and present have formed human settlements in the plain and the settlement pattern of ancient sites, similar to the modern settlements, has been adapted from natural conditions. The overlapping of archaeological sites and residential areas with natural factors suggests that the formation of sites in the study area was mainly due to appropriate environmental conditions such as flat topography and availability of groundwater and surface water resources. It also appears that in different historical periods, security has not been An important issue because archaeological sites have rarely expanded in the entrance of valleys, straits and high lands. In fact, the agricultural capacities of the area have encouraged settlements in this plain.