پالئوژئومورفولوژی چاله سبزوار و نقش آن در هویت آفرینی مدنیت شهری

دریاچه‌ها در ژئومورفولوژی و علوم محیطی ابزارِ بازشناسی شرایط محیطی گذشته، شناخته می‌شوند. زمانی اهمیت آنها دو چندان می‌شود که هویت مکانی خاصی را برای ساکنان ناحیه ساحلی خود نیز بوجود می‌آورند. در سال 1380 انتشار نظریه «دریاچه‌های دوران چهارم، بستر تبلور و گسترش مدنیت در ایران» واقعیت عمیق‌تری از نقش دریاچه‌ها به عنوان یک اکوسیستم طبیعی برملا ‌کرد. این ادعا که دریاچه‌ها پایه ایجاد هویت مکانی و به وجود آورنده یکی از مهم‌ترین سازمندی‌ اجتماعی در ایران به شمار می‌آیند؛ برای ژئومورفولوژیست‌ها نکات درخور تامل و ابعاد جدیدی را به همراه داشت و ذهن آنها درگیر این موضوع کرد شهرهای باسابقه‌ای چون سبزوار که داشتن مدنیت شهری آن در ادوار تاریخی اثبات شده است، چه نسبتی با دریاچه‌های دوره چهارم می‌تواند داشته باشد؟ چگونه ممکن است هویت خود از دریاچه‌ حاشیه خود گرفته باشند؟ این پژوهش سعی دارد از منظر، تلاشی را در شناسایی عمیق‌تر محیط در رد یا تایید این نظریه در سبزوار با روش پدیدارشناسی و تمسّک جستن به اطلاعات ژئومورفولوژی، باستان‌شناسی و رسوب‌شناسی به عمل آورد. نتایج حاصل از این پژوهش نشان داد که مجموعه‌ای از اطلاعات باستان‌شناسی، ژئومورفولوژی و رسوب‌شناسی دال بر وجود دریاچه‌‌ای قدیمی درحوضه آبریز سبزوار به وسعت حدود 32500 کیلومترمربع بوده است. فرم‌های ناتعادلی در بخش جنوب غربی دریاچه، حکایت از شکافتگی این دریاچه و تخلیه آب آن به دشت کویر مرکزی ایران دارد و شواهد فرم‌شناسی در منطقه که متکّی به شاخص‌های توپوگرافی و نحوه استقرار سکونتگاه‌ها در منطقه است، همگی حکایت از وجود دو پادگانه در حاشیه این دریاچه دارد.

Paleogeomorphology of Basin Sabzevar and its role in identifying urban civilization

IntroductionThe lakes are considered as an instruments for recognition of the past environmental conditions in geomorphology and environmental sciences. They are important because of creating spatial identity for residents of their coastal zone. According to the article of Lakes of the fourth era, the basis of the growth and expansion of civilization in Iran, the historic city such a Sabzevar has been located on the on the edge of a local lake that there was no trace of that lake today.Therefore, a scientific and field study to find evidence of this claim began with the question of whether Sabzevar was once located on the edge of the local lake? The Sabzevar hole is one of the areas where its social formations are well known in eastern Iran and according to the Tarikhi Bayhaqi (6th century AH) its formations (with the same old name) still exist despite all environmental incompatibilities. The purpose of this study is to determine the spatial identity of Sabzevar and to test the reality of natural history of this city based on geomorphological, sedimentological and archaeological documents in relation to the theory of Lakes of the fourth era, the basis of the growth and expansion of civilization in Iran by phenomenological method. This article is a test to confirm or reject this theory in Sabzevar hole.Materials and methodsPhenomenological method from Isfahan school is a new method in geomorphology which has special steps and process. To address this issue phenomenologically, data from three areas of geomorphology, sedimentology and archeology have been used. Their interpretation and analysis have been integrated in 5 steps in Grand Theory. The most important variables used in the field of geomorphology are: Elevation data and their analysis in spectral classification of lake terraces Satellite image data for terraces identification Archaeological data and social formations and analysis of their position relative to lakeside terraces Sedimentological and gravimetric data, hydrometry and interpretation of sedimentary indices.Discussion and resultsBy using geomorphological, archeological, and sedimentological data at each step, information on the spatial identity of the Sabzevar hole was obtained. The boundary map of the Sabzevar catchment was obtained using digital data. Field surveys and digital data revealed two terraces in the Sabzevar hole which were plotted on the map. Then the data of 23 ancient hills, historical villages of 6th century AH, and 49 old and new villages with statistical interpretation method were obtained and then analyzed for these terraces, which confirmed the two terraces mentioned in the previous step. The water vector network is also studied in the holes which confirms the existence of a local lake in Sabzevar hole. The data of 5 sediment samples from the study area were also obtained in the laboratory. The result of the analysis of granulometric and their diagrams, calculating the sedimentary parameters of the samples and the hydrometric method of the two samples, all indicated the presence of a lake in the Sabzevar hole. Geological analysis, geomorphology of the Sabzevar hole, topographic line analysis and lake fissure location also confirmed the existence of such a lake in the area.ConclusionThe geomorphic evidence and sedimentological analysis of the Sabzevar hole showed that the Sabzevar hole undoubtedly formed a lake during a period of the Quaternary period. We can generally conclude from this proposal: The presence of the lake in the Sabzevar hole can be confirmed by geomorphology, sedimentology and historical evidence. This hole has been fissured in the western part for some reason leading to the discharge of lake water into the central desert. The largest social formation is the Sabzevar Ghasabeh, which in historical books it is referred to as a city, but other formations in the area have now become urbanized by population law (for example, the villages of Davarzan and Sheshtamad becomes a city in 1995 and 1998, respectively, or the village of Roudab became a district in 1990). Therefore, it cannot be concluded that the present identity of these areas is similar to that previously determined by the lake.References:• The language of landscape Anne whiston spirn(2015), Translated by Seyyed Hossein Bahraini, Behnaz Aminzadeh, Tehran University Press, Third Edition.• Oberlander, Theodore, 2000. Zagros Rivers from a Geomorphological Perspective, Translated by Fatemeh Rajabi, Ahmad Abbasnejad, Tabriz University press.• Babajamali, Farhad, 2014. Exceptionalities in the Identity of Iranian Civil Space, Geography and Environmental Studies, pp. 1420.• Beiranvand, Hojjatollah, 2015. Analysis of Morphometric Indices of Folded Zagros Intercontinental Lakes (Case Study: Khorramabad Old Lake), Journal of Geographical Research, Volume 30, Number 3, Successive Issue 118, Fall, pp.15170.• Tarikhi Bayhaqi, edited by Ahmad Bahmaniar, Islamieh Publications (1954).• Pourali, Maliheh, Adel Sepehr, Mohammad Hossein Mahmoudi Qaraie, 2018. The Survey of mineralogical distribution of Sabzevar Playa surface sediments, 6th National Conference of Iranian Geomorphology Association, pp. 2410.• Gedari eivazi, Jamshid, 1997. Geomorphology of Iran, Payame Noor University Press.• Jafari, Hassan, Hajir Mohammadi, 2018. Palimpsest of Ghezel Ozon Lakes, Journal of Quantitative Geomorphology Research, Volume 7, Number 2, Successive Issue 26, pp. 97116.• Habibi, Seyed Mohsen, 1998. Isfahan School in Urban Design, Fine Arts, Volume 3, Issue 995, pp. 4853.• Ramesht, Mohammad Hossein, 2001. Lakes of the fourth era, the basis of the growth and expansion of civilization in Iran, Research Journal of Isfahan University, Volume 15, pp. 1337.• Zomorrodian, Mohammad Jafar, 2013. Geomorphology of Iran (Construction Processes and Internal dynamics) Volume I, Ferdowsi University of Mashhad Publications.• Zomorrodian, Mohammad Jafar, 2013. Geomorphology of Iran (Climatic Processes and External Dynamics) Volume II, Sixth Edition, Ferdowsi University of Mashhad Publications.• Solgi, Leila, Mohammad Ali Zanganeh Asadi, Ebrat Mohammedan, 1398. Phenomenology in Geomorphology, Geography and Development, No. 54 pp. 211.• Shahzeidi, Somayeh Sadat, 2016. Quaternary Dashte Lut Shaping Transformations (with Emphasis on Reconstruction of Lake Plains, Geography and Environmental Planning, Vol. 27, No. 2, Successive 62, Summer, pp. 130119).