نوع مقاله : مقاله پژوهشی

نویسندگان

1 ژئومورفولوژی، دانشکده جغرافیا، دانشگاه تهران

2 باستان شناسی ، دانشگاه آزاد اسلامی، ورامین

چکیده

در سال‌های اخیر مطالعات ژئومورفولوژی با رویکرد زمین باستان شناسی با هدف بررسی زمینه‌های ظهور و فروپاشی تمدن‌ها و نیز عوامل موثر بر آنها جهت پیدا کرده است. در این پژوهش از دستگاه غربال برای دانه سنجی ذرات بالای 63 میکرون و برای ذرات زیر 63 میکرون از روش پیپت و از نرم افزار گرداستیت برای تحلیل آماری رسوب‌ها بهره گرفته شد. در کنار آن از نتایج کانی شناسی رسی، کلسیمتری و رنگ نیز استفاده شد. بر اساس نتایج گرانولومتری رودخانه کرج در دو بازه زمانی تغییر بستر داده و رسوبات مربوط به دشت سیلابی برجای گذاشته است. ساکنین تپه مافین آباد با توجه به اینکه با فاصه بیشتری نسبت به کانال استقرار پیدا کرده بودند، به نظر می‌رسد متروکه شدن این سکونتگاه بصورت ناگهانی تحت سیلاب رودخانه نباشد. در مقابل ساکنین تپه میمنت آباد بدلیل استقرار در فاصله کم  نسبت به رودخانه تحت تاثیر رژیم رودخانه قرار گرفته اند. بر اساس نتایج کانی شناسی رسی قبل از استقرار ساکنین شرایط آب و هوایی گرم با میزان آبشویی متوسط بر منطقه حاکمیت داشته است. بطور کلی بدلیل نقش ناهمواری‌های بین رودخانه شور و کرج در جابجایی عرضی بستر رودخانه کرج، ساکنین تپه میمنت بیشتر متاثر شده اند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Environmental conditions' study governing on ancient sites with an emphasis on grain size sediment river analysis (Case study: Ancient sites of Meymanatabad and Mafinabad)

نویسندگان [English]

  • Mehran Maghsoudi 1
  • Seyed Mohammad Zaman zadeh 1
  • Asghar Navid far 1
  • Ayoub Mohammadi 1
  • Rooho allah Yousefi Zashk 2

1 Geomorphology, Faculty of Geography, University of Tehran

2 Archaeology, Islamic Azad University, Varamin

چکیده [English]

Reconstruction of the landscape response to climate change in the long-term geological scattered data due to the lack or shortage of sediment and age sediment controls is very dificult. Grain size analysis can be used to identify sediments in environments and different facies, that this in turn gives us some information about sedimentation processes and flowing type. Recognizing the many economic and environmental aspects of early humans due to their dependence on natural factors is not possible without knowing the environmental elements.in this paper we try to study Karaj and Shadchay regime changes and its effects on Meymanatabad and Mafinabad settlements.
Methodology
 Due to analyzing and reconstruction of depositional conditions in both Karaj and Shadchay rivers (a branch that is connected to the Karaj River), Sampling was attempted. Considering that the aim of the study was to examine two ancient hills Meymantabad and Mafynabad. Therefore, the sampling location after repeated field visits to the region, a situation that was chosen to be the width of the cluster. We considered in sampling of river terraces the Sediments resize and change colors. Shadchay River terraces in height of 4:40 m 11cases and from Karaj River terraces in height 7 m 12 cases Samples were taken. Firstly, all samples were analyzed by using a screening device, the second step to obtain deposition below 63 microns in size, moving the pipette method was used.
Results and Discussion
Based on granolomtry results for samples of Tow Rivers, Karaj River in two cases were changed and has left the floodplain sediments. In most cases the particle distribution between classes is above 1000 and below 63 microns. The mean average of particle is 410.76 microns. Depositional environment is constantly changing from calm to energetic; On the one hand it can be because of increase and decrease the power of the river and on the other because of the bed movement. Against the distribution of Shadchay sediments is mostly above 63 microns and rivers has high discharge by then. The average of particle diameter is between 1001.12 microns. campared to Karaj River bed changes not occurred, and are entirely river sediments. Overall, all samples were evaluated for high-energy depositional environment.

Calcymetry

In general, a process diagram for Karaj River is approximately constant. Only layer of 3:40 to 5:60 have the greatest amount of calcium carbonate. According to survey data, we see in this layer, there is only clay and a sand particle was not found in this layer.  In a depth that mixtures of clay and sand particles are deposited (in flooding cases) the amount of calcium carbonate is more. Based on Klsymtry data ersults for the Shadchay River, calcium carbonate has not favorable conditions to be deposited, but an increasing or decreasing trend from low to high exist, in other words, carbon dioxide pressure was high, in general the environment was acidic. In Meymanatabad Hill the most of calcium carbonate belongs to latest ancient layer.

Color

According to Clay Mineralogy sample results that indicate wetter conditions, and due to the location of the study area and the current situation to the first theory, based on warm and humid conditions it is  appearance that brown and red precipitates  were exist. According to the latest Mineralogy of clay that is related to LN108 is belonging to chlorite samples so that this mineral belongs to moderate condition and mild leaching conditions. In fact in temperate conditions and mild leaching rate and location of the inner part of the premountain is somehow confirming the theory of hot and humid condition in the South West of Tehran plane in the Silk period.
 
Conclusion
Based on granolumetry results of samples from two rivers, Karaj river bed changed in two cases and has left sediments of floodplain type. In most cases the particle distribution between classes is above 1000 and below 63 microns. The average particle is between 410.76 microns. Depositional environment is constantly changing from calm to energetic; On the one hand it can be because of increase and decrease the power of the river and on the other because of the bed movement. Considering that the main channel of the river in the mafinabad cluster has not much changed so Cluster residents have long been living in margins of rivers. Seems to suddenly abandoned these settlements have not been effected by devastating floods because residents were deployed with greater distance. Against the distribution of Shadchay sediments is mostly above 63 microns and rivers has high discharge. 

کلیدواژه‌ها [English]

  • Ancient cluster
  • Environmental changes
  • Karaj River
  • Sediment analysis