فهرست مطالب

  • پیاپی 14 (تابستان 1397)
  • تاریخ انتشار: 1397/06/10
  • تعداد عناوین: 7
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  • معصومه پورمعصومی پرشکوه، فرهاد خرمالی*، مارتین کهل، فرشاد کیانی، شمس الله ایوبی، ایوا لهندورف صفحات 123-137

    خصوصیات ژئوشیمیایی رسوبات لسی منعکس کننده شرایط هوازدگی گذشته است و از آن می‏توان برای تعیین ماهیت و منشا رسوبات لسی استفاده کرد. به ‏این منظور شش خاک رخ جنگلی تشکیل شده بر مواد مادری لس در طول یک گرادیان بارش در شمال ایران به روش استاندارد تشریح و نمونه‏های خاک و مواد مادری برای آزمایش‏های فیزیکو‏شیمیایی برداشت شد. غلظت کل عناصر اصلی و کمیاب با دستگاه XRF اندازه‏گیری شد تا عوامل تاثیر‏گذار بر ترکیب شیمیایی خاک‏ها و رفتار عناصر در طول فرایندهای خاک‏سازی ارزیابی شود. آزمایش‏های فیزیکوشیمیایی و نیز مطالعات صحرایی نشان داد آب شویی کربنات‏ها و متعاقب آن تجمع رس فرایند‏های مسئول در تفکیک افق‏های ژنتیکی در خاک‏های مورد مطالعه اند. مواد مادری همه خاک‏های مورد مطالعه ترکیب شیمیایی یکسانی داشتند که نشان‏دهنده تاریخچه هوازدگی مشابه این رسوبات است. در کل، لس‏ها تخلیه شدید عنصر محلول Na و تخلیه ضعیف عناصر محلول Sr و Mg و نیز غنی‏شدگی قابل ملاحظه Ca را در مقایسه با ترکیب شیمیایی پوسته فوقانی قاره‏ای (UCC) نشان دادند. اما روند تغییرات در هر دو گروه از عناصر با روند تغییرات ترکیب شیمیایی شیل متعلق به بعد از آرکئن استرالیا (PAAS) کمی متفاوت ولی مشابه مقدار متوسط جهانی لس (AWL) بود. الگوی عناصر اصلی و کمیاب در افق Bt خاک رخ‏ها در مقایسه با مواد مادری هر خاک رخ روندی مشابه یا نزدیک به محور اصلی نشان داد به استثنای Ca و Sr که به شدت نسبت به مواد مادری تهی شده‏اند؛ ‏طوری ‏که میزان تهی‏شدگی با افزایش بارندگی در گرادیان مورد نظر افزایش نشان داد. روند تهی شدگی Na و P نیز با شدت کمتر با گرادیان بارش موجود در منطقه هم‏خوانی دارد. در مجموع به‏ نظر می‏رسد غلظت مطلق عناصر اصلی، به‏ویژه Si، در خاک‏های مورد مطالعه تحت تاثیر اثر رقت کربنات‏ها قرار گرفته و مقدار عنصر مذکور به‏ طور معنا‏دار در مقایسه با ترکیب شیمیایی PAAS و AWL کاهش یافته است. همبستگی‏های آماری و برخی شاخص‏های ژئوشیمیایی، مانند Ba/Sr و Rb/Sr، این فرض را تقویت می‏کند که ژئوشیمی خاک‏های مورد مطالعه تحت تاثیر ترکیب کانی شناسی مواد مادری و فرایندهای پدوژنیک، مثل کلسیتی شدن، قرار گرفته است. به‏علاوه شاخص CIA و منحنی مثلثی A-CN-K نشان‏دهنده درجه هوازدگی متوسط این خاک‏هاست که با رژیم هوازدگی غالب این منطقه سازگار است.

    کلیدواژگان: ژئوشیمی خاک، فرایند های خاک سازی، گرادیان بارش، لس
  • اسماعیل پاریزی، مجتبی یمانی*، سید رضا مهرنیا، مهران مقصودی، سید موسی حسینی صفحات 139-150

    میزان جابه جایی متفاوت تپه های ماسه ای در دو سایت هم جوار در چاله درانجیر و عوامل اصلی کنترل کننده این لندفرم ها موضوع اصلی این پژوهش است. وجود یا نبود پوشش گیاهی و تفاوت مکانی تپه های ماسه ای این فرضیه را مطرح می کند که تغییر مولفه های هیدروژئولوژیکی عامل مهم اختلاف نسبی میزان جابه جایی تپه های ماسه ای در دو سایت مجاور است. برای آزمودن این فرضیه و دست یابی به هدف، تکنیک های دورسنجی، داده های میدانی، و آنالیزهای ژئوشیمیایی به کار گرفته شدند. در این زمینه، ابتدا میزان جابه جایی سالیانه تپه های ماسه ای بر اساس عکس های هوایی و تصاویر ماهواره ای در بازه پنجاه ساله (1346 1396) محاسبه شد. سپس، با مغزه گیری توسط اوگر دستی، 8 گمانه تا عمق متوسط 20/1 متر حفاری و نمونه های رسوب در هر سایت برداشت شد. حفاری با اوگر تا سطح ایستابی (متوسط عمق 1 متر) انجام گرفت و عمق آب زیرزمینی برای هر گمانه اندازه گیری شد. همچنین در هر گمانه 50 میلی لیتر آب برای آنالیز شیمیایی توسط دستگاه نمونه بردار آب برداشت شد. در مجموع 28 نمونه رسوب از سایت اول، 20 نمونه رسوب از سایت دوم، و 8 نمونه آب از 8 گمانه استخراج شد. تجزیه وتحلیل نتایج موید آن است که کمیت و کیفیت آب زیرزمینی به دو شیوه متفاوت بر میزان حرکت تپه های ماسه ای تاثیر می گذارند. در سایت اول وجود آب زیرزمینی با شوری کمتر سبب تشکیل پوشش گیاهی شده و سرعت جابه جایی تپه های ماسه ای را کاهش داده (45/0 متر در سال) است؛ ولی در سایت دوم عمق کم آب زیرزمینی، قدرت مویینگی بالا، و شوری زیاد باعث شده نرخ حرکت تپه های ماسه ای نسبت به سایت اول هم کمتر باشد (23/0 متر در سال).

    کلیدواژگان: تپه ماسه ای، چاله درانجیر، فرسایش بادی، هیدروژئولوژی
  • داریوش نورالهی، قاسم عزیزی* صفحات 151-161

    به منظور بازسازی آب وهوای منطقه جنوب شرق ایران، مغزه ای به طول 5/5 متر از رسوبات کف دریاچه سردریا، در دامنه کوه تفتان، برداشت شد. روی مغزه مورد نظر آنالیز های زیست شیمی، شامل سنجش سیلیکات های زیست زا و مقدار کل مواد آلی و غیرآلی، به انجام رسید. نتایج سن سنجی نشان داد مغزه مورد نظر 578 سال اخیر را پوشش می دهد. شواهد نشان می دهد تغییرات سیلیکات های زیست زا روند کاهشی دارند که می تواند حاکی از افزایش تدریجی دمای تابستانه در منطقه باشد. تغییرات مقدار کل کربن آلی و غیرآلی، که روندی مشابه را نشان می دهند، بین سال های 1460 و 1650، پیک های افزایشی مشخصی دارند که هم زمان است با عصر یخبندان کوچک در دیگر نقاط دنیا. به طور کلی، شواهد نشان می دهد در عصر یخبندان کوچک دوره های متناوب خشکی های شدید در منطقه رخ داده که با خشک شدگی کامل سطح دریاچه همراه بوده است. این در حالی است که تحقیقات نشان می دهند عصر یخبندان کوچک شرایط مرطوب تری را در نواحی غربی و شمال غربی به وجود آورده است. این نتایج تاییدکننده واکنش های متضاد آب وهوایی منطقه جنوب شرق  نسب به نیمه غربی کشور طی هولوسن است.

    کلیدواژگان: بازسازی آب وهوا، دریاچه سردریا، عصر یخبندان کوچک
  • بهشته نخعی سرودانی، رضا جهانشاهی*، امین عصاری صفحات 163-177

    آبخوان دربرگیرنده پیت معدن گهرزمین از دو بخش آبرفتی و سنگی تشکیل‏ شده است. لایه فوقانی از آبرفت‏های کواترنری و سازند سخت زیرین عمدتا از سنگ‏های دگرگونی مربوط به کمپلکس گل‏گهر ساخته شده است. در سازند سخت، به دلیل وضعیت تکتونیکی منطقه و درزها و شکاف‏ها و بازشدگی‏ها، آب‏های زیرزمینی به سمت پیت معدن تمرکز یافته اند. وجود این آب در پیت معدن، علاوه بر مزاحمتی که در عملیات استخراج ایجاد می‏کند، سبب ناپایداری دیواره‏های پیت و ایجاد هزینه‏های اضافی در عملیات انفجار می‏شود. بنابراین، ضروری است محل زون‏های تراوا با استفاده از روش‏های زمین‏آمار شناسایی شوند و در طراحی آینده سیستم زهکشی پیت معدن مدنظر قرار گیرند. در این پژوهش روش‏ شبیه‏سازی زمین‏آماری گاوسی متوالی جهت نیل به این هدف به کار رفت. تعداد 87 گمانه اکتشافی در لایه متراکم آبرفت کواترنری و سازند سخت موجود است که داده‏های شاخص کیفیت مغزه حفاری (RQD) از آن‏ها برداشت ‏شد. در این مطالعه تحلیل اکتشافی مکانی‏ داده‏ها، شامل بررسی آمار مقدماتی و نقشه موقعیت مکانی و نمودار فراوانی و تغییرنما روی ‏داده‏های متغیر RQD، انجام ‏شد. بررسی آمار مقدماتی نشان داد این متغیر از توزیع نرمال تبعیت نمی‏کند. اعمال وزن دکلاسترینگ تاثیر چندانی بر توزیع آماری داده‏ها نداشت. بنابراین، داده‏ها با یک تبدیل گاوسی به مقادیر نرمال تبدیل شدند و تغییرنمای بدون جهت و جهت‏دار مقادیر نرمال متغیر مذکور ترسیم شد. سه جهت Azimuth 0-Dip 0، Azimuth 90- Dip 0، و Dip 90 بهترین پیوستگی مکانی را نشان دادند. این سه جهت با یک دیگر تلفیق ‏شدند و یک مدل واحد به آن‏ها برازش یافت. بررسی تغییرنمای سه‏بعدی نشان داد بیشترین پیوستگی مکانی در جهت شرقی غربی نسبت به دو جهت دیگر وجود دارد. در نهایت شبیه‏سازی‏ گاوسی متوالی متغیر RQD با استفاده از تغییرنمای سه‏بعدی مقادیر نرمال صورت گرفت و نقشه عدم قطعیت شبیه‏سازی‏ها رسم شد. نتایج نشان داد قسمت‏های جنوب شرقی، جنوب غرب، و غرب پیت بیشترین احتمال وجود زون‏های تراوا را دارند.

    کلیدواژگان: تراوایی، زمین آمار، شبیه سازی گاوسی متوالی، نرم افزار ایساتیس، RQD
  • امیر شمشکی، غلام حسین کرمی* صفحات 179-186

    تغییرات زمانی و مکانی اندرکنش آب‏های سطحی و زیرزمینی در تالاب‏ها، به منزله یکی از زیست‏بوم‏های آبی مهم، بسیار زیاد و پیچیده است. در محیط‏های خشک و نیمه خشک، که میزان بارش‏های جو ی بسیار متغیر و به میزان چشمگیری کمتر از میزان تبخیر است، آب‏های زیرزمینی عامل اصلی تعادل و حفظ محیط‏ زیست تالاب‏ها هستند. در این تحقیق تلاش شد با شناخت بهتر میزان و نحوه تغییرات در اندرکنش آب‏های سطحی و زیرزمینی تالاب قره قشلاق میزان آسیب‏پذیری این زیست‏بوم ارزشمند بررسی شود. این تالاب از نوع تالاب‏های ساحلی است و در انتهای مسیر رودخانه‏های‏ مردوق‏چای و زرینه‏رود در جنوب شرقی دریاچه ارومیه قرار دارد. تالاب‏های انتهایی، مانند این تالاب، به دلیل نداشتن سازوکار حذف نمک، چنانچه در معرض ورود آب شور قرار گیرند، نسبت به سایر تالاب‏ها آسیب بیشتری می بینند. در این پژوهش با ترسیم جهت جریان آب زیرزمینی در زمان‏های مختلف این نتیجه به دست آمد که تالاب قره‏قشلاق از آبخوان های بالادست خود تغذیه می‏شود. با استفاده از قانون دارسی، میزان آب ‏زیرزمینی ورودی به تالاب در سال آبی 1394 1395 حدود 738/0 میلیون متر مکعب برآورد شد. در روش دیگر، با استفاده از میزان ایزوتوپ‏های پایدار دوتریم و اکسیژن -18، مقدار آب زیرزمینی ورودی در سال یادشده به ترتیب 802/0 و 558/0 میلیون متر مکعب بر سال تخمین زده شد. ارزیابی مولفه‏های بیلان آب در تالاب قره قشلاق نشان می دهد حدود 20 درصد از آب این تالاب در سال آبی 1394 1395 با آب‏ زیرزمینی تامین شده است.

    کلیدواژگان: ایزوتوپ های پایدار، تالاب، قانون دارسی، نسبت اختلاط
  • علی شهریار*، کاظم طاهری نژاد صفحات 187-198

    یکی از جنبه های ژئومورفولوژیکی مورد توجه در مناطق خشک با مورفولوژی تپه های ماسه ای مرتبط است. در این زمینه، به منظور مطالعه مورفولوژی ارگ صادق آباد بافق، باد غالب و جهت باد غالب حامل ماسه (RDD) و شاخص همگنی وزش باد (UDI) بررسی شد. به این ترتیب، با استفاده از آمار بیست ساله هواشناسی ایستگاه بافق در نرم افزار Wrplot باد غالب سالیانه و فصلی تعیین و مقادیر RDD و UDI نیز با استفاده از نرم افزار SandRose Graph در مقیاس های زمانی سالیانه و فصلی و ماهیانه محاسبه شد. نتایج نشان داد بیشترین ثبات حاکم بر جهت باد مربوط به تابستان و به صورت بادهای یک جهتی شمال غربی است که بهترین شرایط را برای ایجاد تپه های ماسه ای هلالی و برخانی دارد. شاخص های بادی زمستانی و بهاری نیز از وجود بادهای دوجهته و در نتیجه توسعه سیف ها حکایت دارد. فصل پاییز و به خصوص آبان ماه نیز با حداقل مقادیر مربوط به UDI بهترین زمان جهت توسعه هرم های ماسه ای است. از طرفی مقدار پایین شاخص UDI سالیانه نیز سبب شده تپه های ماسه ای هرمی در ارگ صادق آباد بافق در سراسر سال پایدار باقی بمانند.

    کلیدواژگان: ارگ، بافق، شاخص همگنی وزش باد، مورفولوژی تپه های ماسه ای
  • محمد شریفی پیچون*، فاطمه زارع، کاظم طاهری نژاد صفحات 199-214

    پژوهش های مختلف نشان داده‏اند در پلئیستوسن آب‏و‏هوای کره زمین دستخوش تغییرات متوالی شده؛ به گونه‏ای که گاه با کاهش دما و احتمالا افزایش بارش ها یخچال ها پیش ر وی و با افزایش دما یا کاهش بارش ها یخچال ها پس ر وی کرده‏اند. در این پژوهش، با استفاده از آمار دما در ایستگاه های کنونی و نقشه رقومی ارتفاعی، نقشه‏ هم‏دمای حال حاضر تهیه شد. در ادامه، بر پایه آثار ژئومورفیک یخچال ها، مانند آثار سیرک ها و دره های یخچالی و مورن های برجای مانده، با دو روش رایت و پورتر، برف‏مرزهای دائمی پلئیستوسن بازسازی و بر مبنای آن و همچنین همبستگی بین دما و ارتفاع نقشه هم دمای زمان گذشته ترسیم شد. یافته ها حاکی از کاهش درجه حرارت در گذشته در منطقه به مقدار 2/13 درجه سانتی گراد است. میانگین سالیانه حداقل دما در ارتفاعات 4/4- درجه برآورد شد. با کاهش دما عمده بارش‏ها به شکل برف بوده و زبانه‏های یخی بزرگی شکل گرفته که تا ارتفاع حدود 1750 متر، یعنی خط هم دمای 2/3 درجه سانتی‏گراد، پایین می‏آمده است. تفاوت های دمایی همچنین افزایش گرادیان دمایی، بیش از 8/0 درجه سانتی‏گراد، در آن دوره را نشان می‏دهد. حجم و ارتفاع بالای شیرکوه و جهت دامنه‏ها در محل استقرار و پایین آمدن خطوط برف‏مرز و تعادل آب و یخ اثر داشته است.

    کلیدواژگان: تغییر دما، تغییر رطوبت، حوضه آبریز کذاب، یخچال های پلئیستوسن
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  • masomeh por masomi por shokoh, farhad khormali *, martin kahal, farshad kiani, shamsollah ayobi, Eva lahamdorf Pages 123-137
    Introduction

    The loess-paleosol sequences in Northern Iran are important archives represent several cycles of Quaternary climate change and can be used to complete the information gap on loess between Europe and central Asia. Loess geochemistry reflects paleoweathering conditions and it can be used to determine the nature and provenance of loess deposits. In the Caspian Lowlands, a pronounced precipitation gradient is reflected in mean annual precipitation rates decreasing from about 1850 mm at Bandar Anzali in the West to about 435 mm at Gonbad- e Kavoos in the East. The results of the along a loess climosequence in Northern Iran showed that with increasing precipitation, soil pH and calcium carbonate contents decreases, whereas soil organic carbon, clay content, and cation exchange capacity increases. Many studies have been carried out on the loess-paleosol sequences and modern loess soils in Northern Iran but more investigation is needed with emphasis on the forest soils, their geochemical properties and provenance.

    Materials and methods

    The study area is located in the northern slopes of Alborz Mountain Ranges covered with Caspian or Hyrcanian deciduous forests. Field sampling started in summer 2015. More than ten soil pedons with loess parent material were investigated based on former studies. Finally, six representatives modern pedons were selected and dug in an east-west direction on loess deposits. The climate data shows that precipitation varies from 500 mm in Qapan to up to 800 mm in Neka. Physiochemical properties of soils were studied using standard methods. Element concentrations measured on the fine-grained fractions. These extracted by sieving out material <63 µm and drying it at 105 °C for 12 hours. Eight g of the sieved material mixed with 2 g Fluxana Cereox, homogenized with a vibratory disk mill and pressed to a pellet with a pressure of 19.2 MPa for 120 s. Powdered press pills were analyzed for trace elements (V, Cr, Co, Ni, Zn, Rb, Sr, Zr, Nb, Ba, Nd, Pb) and fused discs for major (Na2O, MgO, Al2O3, P2O5, K2O, CaO, TiO2, MnO, Fe2O3) elements using energy dispersive polarized Spectro Xepos X-ray fluorescence (XRF) device. Every sample measured twice, rotating the pellet in between. Subsequently, mean values calculated from the two measurements.

    Results and discussion

    The results showed that the downward decalcification and the subsequent clay illuviation were the main criteria influencing assessment of soil development in this study. So, all of the soils host argillic and calcic horizons and are classified as Alfisols and Mollisols. All studied pedons had nearly uniform chemical composition in their parent materials, suggesting similar alteration history of these sediments. In general, all parent materials showed strong depletions of mobile element (Na) and weak depletion of Sr and Mg in UCC-normalized spider diagrams. Ca was distinctly enriched in loess compared to UCC. Variation trend of major and trace elements concentration in the studied regions was more similar to average of world loess composition (AWL), but a little different from PAAS (post-Archaean average Australian shale). The significant depletion in Ca and Sr in Bt horizon compared to their parent materials, evidenced in all pedons that was in line with present precipitation gradient and attributed to similar geochemical behavior of Ca and Sr suggesting the alteration of plagioclase. Also, slightly depletion trend of Na and P was in accordance with precipitation gradient. It seems that the absolute concentration of the major elements, especially Si in the studied soils, was influenced by dilution effect of carbonates and consequently amount of this element was significantly lower than AWL and PAAS chemical composition. Chemical Index of Alteration (CIA) values of the samples vary from 62 to 75, higher than those of the UCC (CIA~48) suggesting moderate degree of weathering in studied pedons. The spread of data in A–CN–K ternary diagram space parallel to A–CN line close to the plagioclase weathering trend, revealing comparatively stable K-feldspar/plagioclase ratios in loess.

    Conclusion

    In general, these results support the important influence of parent material on soil geochemistry in studied areas. Additionally, calcification as prevailing pedogenic processes in these areas, can effectively affect elemental distribution within soils. So, the variation of elemental composition and distributions within soil profiles are influenced by parent materials and pedogenic processes. In addition, chemical index (CIA), elemental ratios (Ba/Sr, Rb/Sr) and the A-CN-K ternary diagram indicate a moderate degree of chemical alteration for these soils, compatible with the weathering regime prevailing in the region.

    Keywords: Soil geochemistry, Pedogenic process, Precipitation gradient, Loess
  • Esmail Parbozi, Mojtaba Bamani *, Seyed Reza Mehrnia, Mehran Maghsodi, Seyed Mosa Hoseini Pages 139-150
    Introduction

    About 1/4th of the world deserts is covered with Aeolian sand (McKee, 1979; Ghadiry et al., 2012). Sand dunes are considered as one of the most important geomorphic features of such environments the formation of which shows the abundant resources of sand, the sand-moving powerful wind and the suitable conditions for sediment deposit (Tsoar, 2001; Michel et al, 2018). The most significant feature of these landforms is their dynamics (Maghsoudi et al, 2017) and The dimensions of these landforms is a function of parameters like sand origin, wind power, wind aspect, the amount of particles carried and time (Ahmadi, 2008). Considering the controlling elements of sand dunes, the depth of groundwater and surface moisture are determining elements in specifying the amount of portable deposits and the formation of sand dunes (Hesp, 2000; Bauer et al, 2009; Poortinga et al, 2015; Silva et al, 2018). As a matter of fact, the high water tables limit the movement of sands (Arens, 1996; Oblinger and Anthony, 2008).

    Materials and methods

    In the first stage, two neighboring sites covered by sand dunes were selected based on Google Earth satellite images and field observations. In the second stage, after georeferencing aerial photos taken in 1967 and the satellite images taken in 2017, the rate of sand dune movements was determined and using Transec tool their movement rate with a distance of 1 meter was calculated by GIS software. In each site, regarding the location of the sand dunes and transects, four borings were located for drilling in a field operation and the status and height of the borings was determined by GPS. After the collection of sediment samples, each sample was completely mixed and 100 grams of each sample was taken for chemical analyses. After moving from the depth of groundwater, the depth of the water was measured by a tape measure in each bore. Then, 100 millimeters of water was collected by a water sample collector device for doing experiment. In the geomorphology laboratory, initially the amounts of TDS, EC, and pH in the sample waters were measured by a multi parameter device, version HI9811-5. To measure the amounts of TDS, EC and pH in sediment samples, saturated paste method was utilized. Here, the samples were initially dried in a drying device, and then 50 grams of each sample was measured with an accurate scale and mixed with 50 millimeters of distilled water. In the following step, the distilled water was mixed with sediment samples and the amounts of EC and TDS was measured using the multi parameter device and other devices.

    Results and discussion

    The analyses results of sand dune movement in case study indicate average, minimum and maximum of sand dunes movement are respectively 22.91 m, 0.11 m, 51.24 m in the first site and 11.74 m, 0.01 m, 41.6 m in the second site within 50 years. The result also indicate average of sand dune movement rate in site 1 (0.45 m in year) with Haloxylon vegetation is nearly double of site 2 (0.23 m in year) which haven’t any vegetation. The results of examinations on the qualitative nad quantitative features of the groundwater indicated that the average of ground water depth, TDS, and EC are respectively 1.25 m, 8595 ppm, 17280 µS/cm in the first site and 0.71m, 12990 ppm, and 26160 µS/cmin the second site. The finding of sample sediment analyses shows that the lowest degree of salinity belongs to the sediments of 80-100 depth in the first bore Of the first site with an amount of 840 ppm and 1820 µS/cm and the highest 11900 ppm and 23870 µS/cm belongs to the depth of 0-20 in the bore 2 of the second site.

    Conclusion

    The obtained results indicate that the relative difference in sand dune movements of the two neighboring sites is caused by the hydrologic conditions of the area. In other words, the quantity and quality of groundwater have influenced the rate of sand dune movements in two different ways. In the first site, the existence of groundwater with a lower salinity has resulted in the formation of vegetation and reduced the speed of sand dune movements. However, in the second site high water tables, high Capillary action power,  and high salinity have led to a lower rate of sand dune movements compared to that of the first site.

    Keywords: Sand dune, Daranjir playa, Aeolian erosion, Hydrogeology
  • Daryosh Norollahi, Ghasem azizi * Pages 151-161
    Introduction

    In order to recognize the mechanism of local climatic settings and to be able to establish the future climatic scenarios is essential to understand the past climatic and environmental conditions of the each area. This is also important to explore the response of local areas to the global climatic variations. The palaeoclimate researches carried out in Iran mainly considered the general pattern of Holocene climatic shifts located mostly on western half of the country  (Stevens et al, 2001: Djamali et al, 2009: Griffiths et al, 2001: van Zeis et al, 1967) and few in number in eastern part  (Hamze et al, 2016). These palaeoclimate researches have reconstructed the climatic and environmental changes in the sites located in north and the Zagros range which are roughly controlled by similar synoptic systems. This record first will help filling the existing data gap of the eastern part of Iran as an area to be subjected by monsoon rainfall nowadays and probably in a variable rate in the past.

    Materials and methods

    A 5.5 Meters Core was taken in May 2017 using a Livingstone corer  (Livingstone, 1955) from the middle part of the Sar Darya Lake in 1-m water depth. Samples kept in the plastic waterproof barrels and transported to the University of Bremen, Germany for the subsampling and further analysis. A number of 28 samples were dried and grounded and then the total carbon  (TC) and total nitrogen  (TN) measure with a Euro-EA Elemental Analyser. For CNS the sample is weigh in in Sn-capsules. For TOC the sample is weigh in in Ag-capsules, and treated by 80°C with 3% and 20% HCl to destroy carbonates. TIC=TC-TOC. Measurement range is from 0, 01-100%. In the next step in order to raise the resolution a number of 78 samples selected to be used with Fourier transform infrared spectroscopy  (FTIRS) method. This method confirmed to have high potential for the organic and inorganic content estimation (Rosen et al/////)For FTIRS analyses of the samples in diffuse reflectance mode, a VERTEX 70 FTIRS spectrometer  (BrukerOptik GmbH, Germany) equipped with a diffuse reflectance accessory  ("Praying Mantis" Harrick Inc., USA) was used. Sample pretreatment, IR spectroscopy measurement conditions and processing procedures applied to the raw spectra are described by Vogel et al.  (2016).

    Results and discussion

    The radiocarbon dating carried out by the analytical center of the environmental science atmospheric and ocean research institute, the University of Tokyo. The dating results show that the core expands the last 578 years, BP. In the zone considered as the little ice age the  (1460-1650 AD) the average TIC is 1.6% much higher than the upper part of the core with an average of 0.6%. This high rate is also observed in the TOC with an average of 0.6 higher than the upper part of the core with an average of 0.3%. The highest peaks of TIC and TOC with values of 8.2 and 8.4 respectively occurred in this zone. This zone is not only characterized by high TIC and TOC values but also with high standard deviation (TIC 1.9 and TOC 1.2) implying the high variation of the carbonate content of the core during this phase. Also both TIC and TOC have a low values in the lowermost of the core  (1417-1460 AD).

    Conclusion, Keywords

    The primarily assumption regarding the TIC of the lake sediment is that the low lake level phases increase the carbonate content of the sediment. However this effect could also affected by the other parameter such as the erosion action of the lake  . Additionally, although the TIC and TOC are mostly used for tracking the source of organic matter in the lake environment, show a high potential for investigating the abrupt lake level change (Yuan et al, 2006).  (Heinecke et al, 2016). In the core, high TIC and TOC follows the Ca and Fe patterns which could represent the E/P ratio in the core accordingly. The high TOC and TIC suggested as a result of dry and warm climate (Haberzettl1 et al, 2005) it seems the organic content of the sediment is controlled by the lake level changes as a result. During the LIA the high TIC values indicate a low lake level with low amount of runoff input to the lake. However, the low TIC in the lowermost section of the core, before the LIA and perhaps the last part of the MCA is therefore likely to be the result of high clastic input. During this period a very low TIC content could be related to an high organic content as a result of addition fresh water discharge into the lake which commensurate with silt or silt-clay sediments representing high precipitation and run off inputs.

    Keywords: Climatic Reconstruction, the Lake Sardarya, Little Ice Age
  • Beheshteh Nakhae Sarvdani, Reza Jahanshahi *, Amin Asari Pages 163-177

    In this research, a sequential Gaussian simulation method has been used to determine the permeable zones in the hard-rock aquifer of the Gohr-Zamin open pit mine. For this purpose, 4946 RQD data from eighty-seven exploratory boreholes was used and exploratory-spatial data analysis of these data was performed using the preliminary statistics, location maps, histograms and variograms. Results of preliminary statistics show that this variable has not a normal distribution and that the statistical parameters are not significantly affected considering the declustering weights. The RQD data was transformed to a normal distribution with a Gaussian transform. In the next step, the omnidirectional/directional experimental variograms of RQD data were calculated and modeled using the standard models. Three directions of (1) Azimuth 0-Dip 0, (2) Azimuth 90- Dip 0 and (3) Dip 90 show the best spatial continuity. These variograms were combined together in a one single model. The highest spatial continuity is in the east-west direction compared to the other two directions. Finally, the sequential Gaussian simulation of RQD variable was performed using the 3D modeled variogram and normalized data. A probability map was generated using the results of 100 simultaions. Results show that the southeastern, southwest, and western parts of the mine pit are the best places for drilling new pumping wells.

    Introduction

    Gohar-Zamin iron ore mine is located in 50 km southwest of Sirjan city in Kerman province. Due to the tectonic condition, fracture and fissure in the hard-rock aquifer of area, the groundwater has been concentrated on the pit mine. Therefore, identifying the permeable zones is essential to mine dewatering process.

    Materials and methods

    In this research, ISATIS software has been used to sequential Gaussian geostatistical simulation. The exploratory-spatial data analysis was performed including preliminary statistics, location map, histogram and variograms of RQD values. Then the cell declustring method is used to decluster the RQD variable. Moreover, Gaussian transform method is applied to data normalization. In order to investigate the spatial continuity of the RQD variable, the omnidirectional and directional variograms were generated. Finally, sequential Gaussian simulation as well as simulation uncertainty analysis have been performed using three-dimensional variograms of the RQD normal values.

    Results and discussion

    It is clear from the indicator maps that high RQD values are concentrated in the south of pit and deeper levels. It is influenced by the shape of the iron ore deposit. According to the value of skewness and kurtosis coefficients of RQD, it seems that this variable do not has the normal distribution. The 3D variogram on the XY, XZ and YZ planes indicate (a) lower spatial continuity in the north-south direction relative to the east-west direction, (b) spatial continuity in the eastern-western axis is greater than the Z axis and (c) spatial continuity in the Y direction is greater than the Z direction. The final floor level in the pit is very important for designing and determining the position of pumping wells to dewatering process. Therefore, results of 100 simulations were overplayed. The mean values of simulations calculated from the final floor level in the pit to the top of hard-rock aquifer. It was observed that at each elevation, minimum of RQD were concentrated in certain regions. These maps can be used to determine the high permeable zone.
    Also, two main strike-slip faults with an almost NW-SE and E-W trend, pass through the southern part of pit. These fults and crush zones are located almost in the same direction.

    Conclusion

    According to the results of study, the RQD variable does not follow the standard distribution and declustering weight on the data did not have much effect on the mean value. It indicats a fairly uniform distribution of RQD data in the study area. Omindirectional and directional variograms of the RQD variable (normal values) showed that this variable has good spatial continuity. Moreover, the three-dimensional variogram of the RQD indicated that the E-W direction has the highest spatial continuity relative to the two N-S and Z directions. While, the spatial continuity in the N-S direction is more than the spatial continuity in Z direction. Results showed two straight-slip faults with NW-SE and E-W trends are located in the south of pit and These have important role in greating the crushed and permeable zones. Sequential Gaussian simulation and uncertainty maps in various parts of the pit showed that regions of southeast, southwest, and west of the pit have the highest probability is the low RQD and the high permeability.

    Keywords: Permeability, Geostatistics, RQD, Sequential Gaussian Simulation, ISATIS software
  • Amir Shemshaki, Gholamhosein Karami * Pages 179-186
  • Ali Shahriri *, Kazem Taheri Nejad Pages 187-198
    Introduction

    At present, about 36% of the land surface is covered by arid and semi-arid areas, with 19% of these levels completely dry and no plant life. In Iran, between one third and one-fourth of Iran's dry surfaces are covered with Sand and Sand Dunes. The arid and semi-arid conditions of Iran have caused about 80 million hectares of Iran to be covered by desert areas, sand dunes and insignificant vegetation areas. Therefore, the sand dunes are as one of the geomorphologic types dominate the, which is called Erg in a region of collection of sand dunes. From the shape, sand dunes can be divided and studied from different perspectives. For example, sand dune morphology may consider in transverse, linear, Compound and complex sand dunes or star, Barchan and crescent sand dune morphology stellate or pyramid sandy hills. In general, the first studies on sand dunes relate to the Bagnold study in 1941, which shows that influence of the wind regime on the sand particles diameter and sand dune morphology. He believed that the similarity between morphology and the behavior of sand dune morphology can be used different models to study the sand dunes and Erg morphology. In this research, by studying the wind regime of Sadegh Abad area and studying the effect of wind direction, Different conditions for the formation of various types of sand dunes morphology Influenced by wind, have been discovered.

    Materials and methods

    Daranjir Graben is located in the geographical coordinate’s 55 00 15 to 55 49 30 E, longitude, and 32 34 50 to 31 08 20 N, latitude along the southeast of Yazd, which extends from Kharandagh to Bafq. The Erg of Sadegh Abad is located in Daranjir Playa. Because of the role that wind characteristics in eroding area, Study of sand dunes requires to examine of wind characteristics of an area. Also, because of the dominant morphology of the sand dunes in ergs are dependent on wind direction variations, wind directional studies methods are necessary to investigate the morphology of the sand dunes. The easiest method to study wind regime in a region is to draw wind rose using wind speeds and wind direction data. Wind rose can be plotted monthly, seasonally, and yearly. Therefore, in this study, wind speed and wind direction data of Bafq weather station during a 20 year period (1997-2017) were used in Wrplot software to determine the wind direction in Sadegh Abad. In addition to the prevailing wind direction and drift potential sand, Sand rose was drawn up by Sand Rose Graph software.

    Results and discussion

    Considering the type of morphology of the sand dunes depends on the degree of stability and the wind direction, in order recognize wind regime at a meteorological station. In this condition may change the direction of the wind in a month or season and changing the morphology of the sand dunes over time. Therefore, in the first stage, seasonal and annual wind rose was used to determine the direction of the dominant wind in different seasons. In the next stage, with the fact that the unidirectional index (UDI) slightly changing, with the annual, seasonal and monthly calculated sand rose and another sand movement indexes in the synoptic station Bafq. The Bafq station annual wind rose shows that the direction of the wind dominates is northwest. However, winds could be seen in other directions. The annual sand rose at the summer and spring indicate that the direction of the predominant sand transport is some direction with the dominant wind direction. But, the autumn and winter sand rose show the opposite of this and can be seen the dominant winds of the sand carrier were in a direction perpendicular to the direction of the prevailing north-west winds. In addition to determining the direction of the wind, another factor that plays a more important role in morphological changes and the sand dune dominant shape in an Erg, is the UDI index, or the rate of wind stability at different time periods. In order to determine the UDI value, firstly, sand indicators such as DP and RDP should be calculated and, based on the RDP / DP ratio, calculate the UDI value. The UDI was calculated at an annual rate about 0.24 at the bafq weather station at the Bafq station. In the spring, the homogeneity index of winds has a condition that is approximately equal to a ratio of 0 and 1 (UDI = 0.51) so that in the spring, and to some extent in the winter, there is a prevailing condition that, like the summer season, one can see stability in the winds and the presence of relatively one-side winds, and not like the fall of the year saw different winds toward the Sadeq Abad.

    Conclusion

    The morphology of the Sand dunes is dependent on the region's wind regime, especially wind direction and its sustainability. In the monthly review of the change in RDD, it is evident that the maximum slope of wind change is in the fall season and between two months of October and November, about 90 degrees. This sudden change of wind direction from the southwest in November has had an important role in changing the morphology of the barchan and Crescent sand dunes to star sand dunes. Therefore, by examining the Bafq's wind regime at different time periods, it can be stated that the best conditions for the development of the Star sand dunes are provided in the winter and mid-spring While summer with the highest unidirectional index (UDI = 0.74) and autumn with the lowest unidirectional index (UDI = 0.19) respectively, are suitable for the development of barchan and star sand dunes in the erg of sadegh abad.

    Keywords: Erg, Sand dunes morphology, UDI, Sadegh Abad
  • Mohammad Sharifi Pichon *, Fatemeh Zare, Kazem Taheri Nejad Pages 199-214

    Climate changes and remained geomorphic evidences due to the changes has been interested by geomorphologists in the world. Different researches have shown that world climate has been changed successively in Pleistocene so that with decreasing in temperature and probably increasing in precipitation, glaciers has been progressed and with increasing in temperature and decreasing in precipitation, they has been retreated. Because climate changes in the period has changed the surfaces of the earth, identifying and tracking the effect of the changes is very important in the understanding of environmental conditions during this period. One of the most important evidence of climate changes in Quaternary is remained landforms of glaciers. Although climate change is a global phenomenon, but the trend and the value of these changes varies in different regions of the world. So, the study of these changes should pay attention to in a local scales. Therefore. The main goal of the research is assessment of climate condition in Kazab Basin in the past and calculating differences temperature and precipitation between past and present time. Kazab Basin has located in the South-west Yazd city in the west of Shirkuh Mountain along 31°
    52´  to 32° 7´  of northern latitudes and 53° 52´  to 54° 7´  of eastern longitudes. The range of elevation in the region is between 1732 meters in the output point of the basin and 2916 meters in the peaks of mountains. The area of the region is about 47 square Km. Primary studding show some landform which has created by glaciers such as cirques, U form valleys, and erratic stones. In the researches, we have tried to reconstruct past climate condition according to the landforms as indicators

    Materials and Methods

    The research is based on field observations which according to geomorphic evidences remained from the past, we have studied morphoclimatic condition in the Pleistocene period. For reconstructing past climate condition in the research, we used many data such as topographical and geological map, aerial photographs, satellite images, Google Earth and DTM maps with resolution 20 meters, and also some software like GIS, Excel and GPS system. In addition, for studding present climate and comparing it with the past, we used temperature and precipitation data of 8 stations of rain gauge, 3 station of climatology, and 3 station of synoptic in the region and its surrounding. At first, using topographical maps and according to the form of contours, aerial photographs, satellite images as well as field studying, we marked glacier cirques. For drawing the maps of present isotherm, we create the correlation between altitudes and annual temperature amongst surrounding stations the region. Then, using altitude points extracted from DEM we provided isotherm map for present time. Furthermore, for drawing past isotherm and map, we calculated zero C. line (snowline) for the past with Wright and Porter methods. Then, we obtained an equation according to the correlation between altitude and temperature, and based on that, we evaluated adiabatic lapse rate. Using permanent snowline altitude and adiabatic lapse rate it would be draw past isotherm map.

    Results and Discussion

    In the research, remained geomorphic indicators has been studied at first. Those which can help to understand and reconstruct Pleistocene paleoclimatic in the central of Iran. Therefore, permanent snow line was determined. The line has located at the height about 2274 meters on the basis of wright method and at height about 2200 meters according to Porter method. The line accepted as the border of temperature of zero degree in the past. Also, on the basis of erratic stones in the region was determined the equilibrium line of water and ice in the past. Findings show that the temperature in the region has decreased so that the minimum temperature in high altitude has reached to – 4,4 C.. Therefore, glacier’s tongue has been descended to about 1750 meters and there has been melt; because temperature in the altitude has increased to 3.2° C. The remained erratic stones in the altitude affirm the hypothesis. Therefore, with comparison of isotherm map of the region for present and past time, we estimated about 12, 4° C. changes in the temperature in the region. Also, different temperature show that lapse rate has been about 0.8° C. in the past, but it is about 0.65 at now. Probably, Siberian high pressure has dominated in the region during more often the months of the year.

    Conclusion

    Results show great changes in climate in the region so that with field studding we observed many glacier landforms in the region such as a few cirques, U form valleys, stone traces as well as erratic stones. In according to these landforms as indicators for calculating climate changes, we tried to reconstruct climate condition in the past. Thus, we drew isotherm and isohyet maps for past and present time and compared them together using GIS. Results show that the temperature has been colder than now about 12,4° C.  Besides, the area of the glaciers has been spread to about 2200 meters (permanent snowline). But, glacier’s tongue has been descended to about 1600 meters inside the plain, and there has been melt; because temperature in the altitude increased to 4.1° C. the remained erratic in the region affirm the hypothesis.

    Keywords: Kazab Basin, Humidity Change, Pleistocene Glaciers, Temperature Change