Persian Gulf Coastline and the Location of the new find fifith millennium BCE site Tahmachi in the Lirawi (Dylam) Plain

Introduction   Given the diverse characteristics of Iranchr('39')s geographical area, we know that the diversity of Iranchr('39')s natural landscape is not limited to the lowland and highland areas. Evidence suggests that large bodies of water in northern and southern Iran and its surrounding lands have long been one of the most attractive niches for human societies. Some misconceptions have led researchers to believe that due to successive fluctuations in sea level, one should not expect prehistoric habitats on the shores of the Persian Gulf. The new geological and especially archaeological evidence, one after the other, clearly leads us to clarify the previous assumptions. Tappe Tahmachi is one of the of the 5th millennium BCE settlements in the Lirawi (Dylam) Plain, which, in addition to being close to the Zendaroun freshwater river, is less than five kilometers from the current shores of the Persian Gulf. The assessment shows that Tahmachi, with more than ten meters of cultural accumulations, was not a temporary settlement on the coast. Therefore, for the first time on the northern shores of the Persian Gulf, significant evidence has been obtained to explain clearly the Persian Gulf coastline in the fifth millennium BCE.   Materials and Methods Due to climate changes happened during the last ice age (appr. 70.000 and 17.000 years ago) sea levels were lower 120 meters than their current situation. Prior to these changes, the Persian Gulf did not exist as a body of shallow water as today. By joining three of the most important rivers in the Near East, i.e. Euphrates, Tigris and Karun, a largely extended river had formed that ran from current Arvand River (Shat al Arab) to the mouth of the strait of Hormoz. It is clear that such a river had a huge impact on human life especially during the village period. Researchers believe that seawater reached its current level in earlier times, and even reached a level higher than this about 6,000 BC, about 1 to 2 meters above the current level. Among the documents provided for the qualitative and quantitative explanation of the Persian Gulf coastlines, the distribution of prehistoric settlements and their remoteness and proximity to the sea are of great importance. In a narrative of the prehistoric settlements increase on the southern shores of the Persian Gulf, we will see that a significant number of sites have been found near the current coastline. However, this figure is not seen in the coastal areas north of the Persian Gulf, due to the lack of prehistoric sites near the northern coast of the Persian Gulf or extensive sea fluctuations in this area. We believe, the most important reason is the lack of purposeful archaeological research.   Tahmachi prehistoric site is located in the Lirawi (Deylam) Plain, a flat, low-lying plain with a slope of less than 0.5% and 4,500 meters from the current shores of the Persian Gulf (Figure 2). As for the soil quality, if water resources are available and proper drainage is possible, we can expect the harvest of crops such as sugarcane in the surrounding areas of Tahmachi. Some areas of the plain have the potential to form salt marshes. Due to its proximity to the tidal range of the sea, the southern areas of the plain have high groundwater levels and saline soils. Hundreds of seasonal and permanent drainages have been formed from the heights of the Rag Sefid ridge to the sea due to the difference in height between the Rag Sefid and the Lirawi Plain, and especially the low point of the sea. In most gullys, water is seen when it is raining and, of course, otherwise it dries up. Meanwhile, some gullys have water all year round. Zendaroun River passes a short distance west of Tahmachi. The river originates from the Tonbata valley in the highlands of the Rag Sefid and finally flows into the Persian Gulf with great meanders in the Lirawi alluvial plain. Rivers such as Zendaroun are one of the sources used for desalination of current agricultural lands due to their fresh water content. Tahmachi, 39R417186.67 m E 3338440.23 m N, is located right on the east side of Zendaroun river and is located almost in the middle of a hypothetical straight line with a length of 10 km from the heights of Rag Sefid to the Persian Gulf coast (Figure 2). The compound consists of two north and south mounds that are located a short distance from each other (Figure 3). The height of the northern mound is 16 meters and the southern mound is 14 meters above sea level. The ratio of lands around two mounds: the southern lands of the area is about 7.25 meters and the northern lands are about 10 meters above sea level (Figure 4). Conclusion The presence of Tahmachi near the shores of the Persian Gulf has taught us important lessons. First: For decades, a very important actor (prehistoric sites) in the measurement of water fluctuations in the Persian Gulf has been ignored. Second, what has received less attention in prehistoric archeological literature is settlement diversity. However, available evidence has shown that not all settlements are necessarily functionally the same. Third, it may seem that due to the proximity to tidal fluctuations, soil salinity, heat and lack of rainfall, one should not expect any prehistoric habitat in coastal areas. Considering the Tahmachi pattern, we very much hope that surveys on the northern shores of the Persian Gulf will no longer be conducted in the same way as before, and that researchers will carefully study and assess the promising areas before making any predictions. In this case, we very much hope that the number of prehistoric settlements on the northern shores of the Persian Gulf will be much higher than the number identified so far.