نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده جغرافیا، دانشگاه تهران

2 ژئومورفولوژی، دانشگاه تهران

چکیده

تحولات اقلیمی مهمترین ‌رویداد دوره کواترنری است و پلایاها میراث این تغییرات اقلیمی هستند. هدف از این پژوهش شناسایی و بررسی شواهد ژئومورفولوژیکی(پادگانه‌های دریاچه‌ای) و رسوبی لوت، برای بازسازی سطوح و مناطق دیرینه تحت تاثیر نوسانات آب دریاچه است. این دریاچه در لوت جنوبی واقع در جنوب شرقی ایران قرار دارد. در فرآیند این پژوهش با بررسی‌های میدانی در مناطق شمال‌شرقی کلوت‌ها پادگانههایی مشاهده گردید و برای تایید اطلاعات رسوب شناسی برای محدوده حاشیه‌ای دریاچه قدیمی (پادگانه‌ها) در منطقه، برداشت نمونه رسوب  انجام پذیرفت. همچنین با گذر هوایی در منطقه جنوب‌شرقی نیز پادگانه‌هایی در محل شناسایی و با استفاده از تصاویر ماهواره‌ای وDem 10 متر منطقه پادگانه‌هایی مشابه در مناطق شرقی هم مشاهده و ارتفاع آنها تعیین گردید. با توجه به داده‌های ارتفاعی بدست آمده از پادگانه‌ها که همان تراز آب دریاچه در کواترنرند حدود دریاچه برای لوت بازسازی گردید تا محدوده آبگیری دریاچه در دوره‌های گذشته و گستره دریاچه تعیین شود. همچنین با انجام آزمایشات بر روی نمونه برداشت شده و انجام محاسبات آن در نهایت با توجه به شاخص‌های رسوبی و بررسی ویژگی‌های رسوبات برداشت شده از پادگانه، این رسوبات بامیانگین رسوبات ماسه‌ای ریز تا متوسط شرایط رسوبی حاشیه دریاچه‌ای در کواترنر را تایید می‌کنند.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Determination of pluvial Lake Range of Lut based on sedimentary and geomorphological evidences

نویسندگان [English]

  • Mehran Maghsoudi 1
  • Arefeh Shabani Araghi 2
  • Masoumeh Bani Safar 2

1 Faculty of Geography, University of Tehran

2 Geomorphology, University of Tehran

چکیده [English]

Introduction
Climate changes are the most important event on the Quaternary period and Playas are the climate changes legacy. Playas are legacies of the Quaternary climate changes and have the special position among of the geomorphological areas of Iran, especially in the dry areas. Terraces, alluvial fans sequences and coastlines movement are main evidences base-level changes during the Quaternary. Playas and lakes or generally inner craters have a key role in the climatic balance and ecological changes in the Quaternary, in their surrounding areas and always have been considered to determine past climates.
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Area location
Lut desert in Iran's southeastern is in the area of SISTAN and BALUCHESTAN and KERMAN provinces. Iran Yardang is formed in west of the central Lut Desert that is the unique example of the magnitude and extent. This lake is located in the South Lut located at in south-eastern Iran in the Yardangs range .
Materials and methods
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In this study, we have examined the geomorphological (lake terraces) and sedimentological (lake sediments) evidences for reviewing the range of Lut lake. It has used the documents and library materials (including books, Persian and English articles and dissertations), video sources (including geological maps, ETM satellite sensor Landsat imagery, TM and Digital Elevation Model SRTM 90 meters and Dem 10 meters), Visit and sampling of the area (Terraces and lake levels of area were visiting and terraces were sampled to approve the lake sediments) and as well as are used laboratory operations. In this research, they have been observed terraces in the northeast areas of Yardang by field studies and sediment sampling was conducted for confirm sedimentology date for the marginal area of the past lake. Also with the passage of air in the Southeast region is detected terraces in the location and similar terraces in the eastern regions are determined by using satellite imagery and digital elevation model. Based on height data obtained from the terraces that they are the lake water level in the Quaternary it was rebuilt lake range for Lute for that was specified the lake dewatering range in prior periods and it was determined the extent of the lake. Also with tests on sediment samples and eventually the calculation of the indices due to sedimentary indexs and examination of sediments features with an average small to medium sandy sediments, sandy sediment conditions has been approved in the lake margins in Quaternary.
 
Results and discussion
Checking the Lut Desert terraces indicates that the terraces around this plains have not similar height But according to study, 330 350 404 meters depth by using of a Digital Elevation Model and compliance with satellite images having best match with the lake terraces of around the hole and based on these curves, the lake border is designated at different phases of advance and retreat in the area. Finally, we researches on the sediments of the lake terraces in the area and based on the particle average depends on source type of deposition, transport factor type and deposition conditions and sediments and indexes shows energy conditions in layers. Should be stated that this terraces confirms the lake-margin sediments conditions with an average of small to medium sandy survey.
 
Conclusion
Evidence indicates that there have been a relatively shallow lake in the past and low energy environment and it is affected by evaporation and drying conditions alternatively. As well as different levels of terraces with different heights shows the advance and retreat phases of the lake.

کلیدواژه‌ها [English]

  • Lake Terraces
  • Lut Desert
  • Quaternary
  • Determination of Range
  • Lake Pluvial