فهرست مطالب

  • پیاپی 15 (پاییز 1397)
  • تاریخ انتشار: 1397/09/10
  • تعداد عناوین: 7
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  • حسن فتحی، محسن پورکرمانی، محمد آب دیده*، سهیلا بوذری، محمود الماسیان صفحات 235-251
    تولید و تزریق سیال ممکن است، از طریق تغییر فشار منفذی و تغییرات متناظر در میدان تنش، سبب ایجاد شکست هیدرولیکی، شکست برشی در سطوح ترک، یا فعالیت مجدد گسل ها و ناپیوستگی های موجود توسط کاهش تنش موثر شود. بنابراین، تغییر شکل زمین، لرزه های اتفاق افتاده، فعالیت مجدد ناپیوستگی ها، و ظرفیت ناتراوایی سنگ های اطراف مجموعه مخزن پوش سنگ از پدیده های مهم در اجرای پروژه های دربرگیرنده تولید و تزریق گاز در فضاهای زیرزمینی محسوب می شوند. استراتژی موفق در توسعه مخزن مطالعه و مدل سازی ژئومکانیکی مخزن را می طلبد. ساخت یک مدل جامع ژئومکانیکی شامل وضعیت تنش به صورت تابعی از عمق (جهت و مقدار)، خواص فیزیکی سنگ مخزن و سازندهای آن (مقاومت سنگ و مدول های الاستیک)، تخمین فشار منفذی، و توصیف و توزیع شکستگی ها و گسل هاست. در این پژوهش، مدل ژئومکانیکی یک بعدی ساخته شده در میدان مورد مطالعه با استفاده از نرم افزار IP توضیح داده شد و با مدل‏سازی تحلیلی به بررسی و ارزیابی امکان فعالیت مجدد گسل‏ های میدان، امکان وقوع شکستگی ‏ها طی عملیات تزریق و تولید، و میزان بحران تغییر فشار تزریق و تولید برای ایجاد شکستگی‏ های کششی و برشی پرداخته شد.
    کلیدواژگان: پوش سنگ، تزریق گاز، فشار منفذی، خواص الاستیک سنگ، فعال شدن مجدد گسل ها، مدل ژئومکانیکی، ناپیوستگی
  • رضا صفایی راد، قاسم عزیزی*، مهران مقصودی صفحات 253-271
    کوهستان زاگرس، به منزله بخشی از هلال حاصلخیز که میزبان تمدن‏های دیرینه بوده است، گذشته تاریخی شکوهمندی دارد. با توجه به این مهم، پی بردن به شرایط آب‏و‏هوایی‏ای که این تمدن‏ها در آن می‏زیسته‏اند از اهمیت فراوان برخوردار است. در این پژوهش با به کار بردن روش‏های پذیرفتاری مغناطیسی و جرم‏کاهی گرمایشی بر مغزه رسوبی تالاب هشیلان کرمانشاه، داده‏هایی با کیفیت زمانی بالا برای بازه زمانی 000/22 تا 200/2 سال پیش تولید شد. نتایج نشان داد در پلیئستوسن پسین، به دلیل شرایط آب‏و‏هوایی سرد و خشک، میزان تبخیر به شدت کاهش یافته و تالاب هشیلان تا 400/15 سال پیش حالت دریاچه‏ای داشته است و پس از آن، با افزایش گرما، به تالاب تبدیل شده است. نتایج این پژوهش رابطه متضاد آب‏و‏هوایی بین زاگرس و منطقه آب‏و‏هوایی موسمی تابستانه هندوستان، به ویژه در هولوسن پیشین، را آشکار کرد. افزایش خورتابی تابستانه نیم کره شمالی در هولوسن پیشین، که مهم ترین واداشت آب‏و‏هوایی است، از یک سو سبب تقویت موسمی‏ها و مرطوب شدن مناطق تحت نفوذ آن ها شده و از سوی دیگر با تقویت مراکز پرفشار جنب‏حاره‏ای و استقرار طولانی‏تر این مراکز بر زاگرس سبب خشکی آب‏و‏هوای آن شده است. بر اثر کاهش تدریجی میزان خورتابی از هولوسن پیشین به هولوسن میانی، موسمی‏ها تضعیف و به سمت عرض‏های جغرافیایی جنوبی‏تر جابه جا شده‏اند. این وضعیت سبب تضعیف و جابه جایی جنوب‏سوی پرفشارهای جنب‏حاره‏ای شده که نفوذ بیشتر بادهای غربی باران‏زا به زاگرس و مرطوب شدن آب‏و‏هوای آن از حدود 000/6 سال پیش را در پی داشته است.
    کلیدواژگان: آب و هواشناسی دیرینه، خورتابی، کوهستان زاگرس، موسمی تابستانه هندوستان، هولوسن
  • محمد اخوان *، گیوم ژامه، سیمون پوئو، مریم حیدری، گیوم گرن، میلاد هاشمی، حامد وحدتی نسب، ژیل بریون صفحات 273-290
    محوطه پارینه سنگی میرک (سمنان، ایران) در یک دشت سیلابی خشک در حدود شمالی دشت کویر قرار دارد. نهشته‏ های خاکی رسوبی میرک در محدوده زمانی بین پلیئستوسن پایانی تا هولوسن شکل گرفته ‏است. گاه نگاری این مطالعه به روش سن یابی لومینسانس برانگیخته نوری  (OSL)انجام شد که برای قدیمی‏ترین لایه‏ های آزمایش شده~50±3.  هزار سال پیش را برآورد می کند. در میرک، از لحاظ چینه‏ نگاری، دو لایه رسوبی مشخص قابل شناسایی است. لایه یک دربردارنده رسوبات کوهپایه ‏ای سیلابی و لایه دو دربردارنده رسوبات بادی کربناته است. بخش بالایی این لایه از خاک‏ های ریزدانه نارس خشکیده و ترک خورده در محیطی گرم‏تر و خشک‏ تر شکل گرفته است. لایه‏ های دربرگیرنده بقایای پارینه ‏سنگی میرک در مرزهای مشخصی پیدا شده و احتمال می‏رود برخی از آن ها از انباشت متعدد استقرارهای انسانی تشکیل شده ‏باشند. حوالی ~1.2±0.2 هزار سال پیش، وقفه ای به طول مدت سه هزار سال ستون رسوبی میرک را قطع کرده که روی آن را حدود 2 متر انباشت بادی پوشانده است. این ناپیوستگی در نتایج آزمایشگاهی به خوبی قابل شناسایی است. با وجود اختلاف در رژیم‏ های رسوب‏ گذاری، داده‏ های آزمایش ‏های XRD، اسپکتروسکوپی مادون قرمز، میکروسکوپ الکترونی، و میکروسکوپ نوری اختلاف کانی‏شناسی خفیفی را در کل رکورد رسوبی نشان می‏دهد. نتایج این پژوهش حاکی از یک منشا زمین‏ شناسی محلی برای رسوبات انباشته شده در محوطه میرک است. پس از رسوب‏ گذاری، نهشته‏ های رودخانه ‏ای و بادی، هر دو، در معرض درجات مختلفی از خاک زایی (پدوژنز) قرار گرفته اند و در نتیجه حاوی نشانه‏ های خاک زایی مشخصه خاک ‏های نوع Entisol و Aridisol آهکی و ژیپسی هستند. مقادیر متغیر آهن و شرایط اکسیدکننده متفاوت بین دو لایه را می‏توان به سطوح بالاتر آب زیرزمینی و محیط کاهنده آهن، به ویژه در واحدهای رسوبی نهشته شده پیش از ~28±2 هزار سال پیش، نسبت داد. به نظر می رسد وضعیت در نهشته‏ه ای هولوسن برعکس بوده است.
    کلیدواژگان: ایران، پارینه سنگی، رسوب شناسی، زمین شناسی کواترنری، میرک
  • مهسا عبدالهی*، حسین حاجی علی صفحات 291-305
    این مطالعه به منظور تهیه نقشه های هم شتاب زمین لرزه در گستره ساوه بر مبنای نرخ لرزه خیزی انجام شد. روش مطالعه شامل شناسایی چشمه های لرزه زا، برآورد پارامترهای لرزه خیزی، و دخیل کردن زمین لرزه های تاریخی در تحلیل ها بود. در نهایت، با نسبت دادن پارامتر های یادشده به چشمه های لرزه زا، تحلیل ها در محیط نرم افزار EZ-Frisk صورت پذیرفت. بر اساس این مطالعات، نقشه های هم شتاب زمین لرزه در پریود نزدیک به صفر ثانیه (PGA) برای دوره های بازگشت 475، 975، 2475 سال و بر مبنای نرخ لرزه خیزی در گستره ساوه تهیه شد. طبق این نقشه ها، مقدار بیشینه شتاب در حدود 0.94g و مربوط به زمین لرزه ای با دوره بازگشت 2475 سال است. برای دوره بازگشت 975 سال، مقادیر بیشینه شتاب حدود 0.69g است. در دوره بازگشت 475 سال بیشینه شتاب زمین لرزه در حدود 0.49g است.
    کلیدواژگان: نرخ لرزه خیزی، نقشه های هم شتاب، EZ-Frisk
  • احمد آزادی* صفحات 307-319
    جوامع انسانی، طی یک دوره چندهزارساله، از اواخر دوره پلیئستوسن تا اوایل دوره هولوسن، توانستند شیوه معیشتی خود را که مبتنی بر شکارگری و گردآوری خوراک بود به کشاورزی و یکجانشینی تغییر دهند. این تحول شگرف، که از آن با عنوان فرایند نوسنگی‏ گرایی/ نوسنگی ‏شدن نیز یاد می‏شود، یکی از مباحث مهم باستان‏ شناسی دوره پیش از تاریخ است. در ارتباط با گستره جغرافیایی رخداد این تحول مهم، به ‏طور کلی، توافقی عمومی درباره جنوب‏ غرب آسیا بین پژوهشگران وجود دارد. پژوهش ‏های اخیر در ارتفاعات  زاگرس و کوه‏پایه‏ های آن به کشف شواهد بسیار مهمی در ارتباط با فرایند نوسنگی‏ گرایی منجر شده و بار دیگر توجه پژوهشگران را به بخش ‏های شرقی هلال حاصلخیزی معطوف ساخته است. پژوهش ‏های باستان‏ شناختی جدید در منطقه کهگیلویه، به ‏منزله بخشی از ارتفاعات جنوبی زاگرس، و شناسایی شمار قابل‏ توجهی از استقرارهای آغازین دوره هولوسن از پتانسیل‏ های بالای این منطقه برای مطالعه فرایند نوسنگی ‏گرایی در این بخش از فلات ایران حکایت دارد. در بررسی ‏های انجام‏ شده در منطقه کهگیلویه شمار 16 محوطه از استقرارهای آغازین دوره هولوسن شناسایی شده است. این استقرارها، از منظر ریخت‏شناسی نوع محوطه، در چهار گروه تپه‏ ها (5 تپه)، محوطه ‏های باز (8 محوطه)، پناهگاه‏ های صخره‏ای (2 پناهگاه)، و یک مورد غار طبقه ‏بندی می‏شوند. در مجموع الگو‏های استقراری و معیشتی این محوطه ‏ها متاثر از چند عامل دشت، رودخانه، کوهستان، و تنگه‏ هاست که نشان می‏دهد جوامع این دوره از همه پتانسیل‏ های زیست‏ محیطی این منطقه بهره برده‏ اند.
    کلیدواژگان: زاگرس جنوبی، کهگیلویه، نوسنگی بی سفال، هولوسن
  • فاطمه باقری*، غلام حسین کرمی، رحیم باقری، رضا نجف زاده، اعظم رونقی صفحات 321-339
    منابع آب سطحی و زیرزمینی، به خصوص چشمه کارستی ارناوه و سد شیرین دره، منابع اصلی آب آشامیدنی و کشاورزی در استان خراسان شمالی در شمال شرق ایران است. هدف این مطالعه تعیین منشا و بررسی خصوصیات هیدروشیمیایی و ایزوتوپی چشمه ارناوه و سد شیرین دره و کیفیت آب جهت کشاورزی و شرب بود. نمونه های آب طی یک دوره (مهرماه 1397) از چشمه کارستی ارناوه، رودخانه، و سد شیرین دره جمع آوری و مقادیر EC، TDS، یون‏های اصلی، و ایزوتوپ‏ های δ18O و 2Hδ آن‏ها تعیین شد. همچنین، دو ایستگاه باران سنجی قلعه بربر و حصه‏گاه نیز جهت نمونه‏ برداری ایزوتوپی از آب باران و ترسیم خط ایزوتوپی بارش انتخاب شدند. نتایج هیدروشیمیایی نشان داد تیپ آب کلیه نمونه‏ ها Ca-Mg-HCO3 و Ca-Mg-SO4 است. میانگین هدایت الکتریکی نمونه‏ها حدود 900 میکروموس بر سانتی‏متر بود که تغییرات مکانی و عمقی چندانی در محدوده مورد مطالعه ندارد. کیفیت آب رودخانه شیرین دره پس از اختلاط با چشمه بهتر شده و مقدار غلظت یون ‏ها کاهش یافته است. رابطه به دست آمده برای خط بارش ایزوتوپی شیرین دره + 5.67 (R= 0.96) δ18O 7.14 2H=δ بوده که به دلیل تبخیر ثانویه و شیب و عرض از مبدا آن نسبت به خط بارش جهانی کاهش پیدا کرده است. بررسی ایزوتوپی نشان می‏دهد منشا آن‏ها بارش ‏های جو ی است و نمونه ‏های مخزن، به دلیل تبخیر، غنی‏تر از رودخانه است و انحراف ناچیزی از خط بارش محلی دارد. کیفیت آب از نظر شرب و کشاورزی مناسب است.
    کلیدواژگان: خصوصیات ایزوتوپی، خط بارش ایزوتوپی، شاخص کیفی، شیرین دره، هیدروشیمی
  • عبداللطیف قوچی زاده، مظاهر معین الدینی*، رضا شهبازی، ناهید احمدی، محمود ناوور نویری صفحات 341-360
    این مطالعه با هدف تعیین کانون طوفان های گردوغبار و خط سیر آن، با استفاده از مدل HYSPLIT و شاخص های تعیین منشا جهتی، شامل گل باد و گل غبار و تابع احتمال شرطی، انجام شد. در ابتدا رخدادهای طوفان گردوغبار در بازه زمانی 2008 تا 2017 شناسایی شدند. با مدل الگوریتم انتشار، مسیریابی برای هر یک از رخدادهای شناسایی شده در سه سطح ارتفاعی 10 و 500 و 1000 متری به صورت عقب گرد به مدت 24 و 72 ساعت انجام شد. کانون های گردوغبار محدوده مورد مطالعه اکثرا از نوع سازندهای دوره کواترنری و بیشتر سازندهای تشکیل دهنده این کانون ها تراس های مخروط افکنه قدیمی و پادگانه های آبرفتی رسی است که مستعد تولید گردوغبارند. نتایج این تحقیق، از جمله گل باد و گل غبار و تابع احتمال شرطی، و مدل HYSPLIT نشان داد طوفان های گردوغبار از جهت های جغرافیایی جنوب شرق شرقی و غرب در فصول مختلف به سمت شهر قم حرکت کرده است. دریاچه نمک و اطراف آن، که کانون شماره 4 است و در شرق شهر قم قرار دارد، بیشترین تاثیر را بر کیفیت هوای شهر قم در دوره زمانی مورد مطالعه داشته است. طوفان هایی که با منشاهای خارجی در دوره مورد مطالعه شهر قم را تحت تاثیر قرار داده اند بیشتر از کشورهای عراق، عربستان، سوریه، و اردن بودند.
    کلیدواژگان: تابع احتمال شرطی، طوفان گردوغبار، گل غبار، مدل های اسپلیت
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  • Mohammad ABDIDEH Pages 235-251
    Production and injection of fluid may cause hydraulic fracture, shear fracture at crack levels, or re-activation of faults and existing discontinuities by reducing effective stress by changing the pore pressure and corresponding changes in the stress field. Therefore, the deformation of the earth, seismic occurred, the reactivation of discontinuities and the impermeability capacity of the rocks surrounding the reservoir-caprock are considered important factors in the implementation of projects involving the production and injection of gas in underground spaces. Successful strategy in reservoir development is inevitably of geomechanical studies and modeling of reservoir. The construction of a comprehensive geomechanical model includes the stress position, a function of depth (direction and amount), the physical properties of the reservoir rock and its formations (rock resistance and elastic modulus), pore pressure estimation, description and distribution of fractures and faults. In this paper, one-dimensional geomechanical model constructed in the studied field was described using IP (Interactive Petrophysics) software, and by analytical modeling, the possibility of reactivation of the field faults, the possibility of fractures occurring during the operations of injection and production, and the critical amount of changing pressure of injection and production to produce tensile and shear fractures, have also been studied and evaluated.
    Keywords: Caprock, Reactivation of faults, Discontinuity, Gas injection, Pore pressure, Geomechanical model, Elastic properties of rock
  • Reza Safaeirad, Ghasem Azizi*, Mehran Maghsoudi Pages 253-271
    1-Introduction
     The Zagros Mountains range with a northwest-southeast direction covers a large part of western Iran. This range acts as a barrier against mid-latitude westerly airflows and thereby generates significant orographic rainfalls, resulting in a hospitable environment which has been home to ancient civilizations. Major variations in the westerlies can lead to significant environmental changes in this mountain range. Although previous researches have shed some light on the late Pleistocene and Holocene climatic and environmental conditions of the Zagros Mountains, our knowledge on the mechanisms controlling the paleoclimate of this historically important region is yet unknown. Most of our understanding of the Zagros paleoclimate is mainly based on the low-resolution pollen studies carried out on the poorly dated sediment cores. Because the response of the vegetation changes towards climate changes is mainly accompanied by a time-lag, it is difficult to compare the pollen records of the Zagros Mountains with the different climate records of the regions that their paleoclimate response to the climate forcing is well documented. Generating high-resolution sedimentological proxy data which immediately respond to climate variations and comparing them with the regional climate records, can enable us to reveal the response of Zagros paleoclimate to climate forcing. Here, we present a high-resolution Magnetic Susceptibility (MS) and Loss-on-Ignition (LOI) records from a sediment core collected from Hashilan Wetland located at the Central Zagros.
    2-Materials and methods
     Hashilan Wetland (34° 34 N, 46° 52 E, 1310 m a.s.l.) is a palustrine wetland located at 36 km to the northwest of the town of Kermanshah, Kermanshah Province, W Iran. According to the Köppen climate classification system (Köppen, 1931), the climate of the study area (annual rainfall: 410 mm, mean annual temperature: 15.5 °C and with 5 dry months from May to October) is defined as a Mediterranean type. The wetland is fed by a karst aquifer, called Khorrin aquifer, developed in the pure limestone of Bisotun and does not have any riverine input. The low dynamic storage volume of Khorrin aquifer makes the wetland very sensitive to variations in rainfall (Bagheri Seyedshokri et al., 2015). For example, the area of wetland shrank by 48% in 2007 due to a severe drought (Jafarbigloo et al., 2015).In autumn 2016, a sediment core was retrieved from Hashilan Wetland. Based on 10 radiocarbon ages the 315-cm long core (85-400 cm depth) ranges from 22 to 2.2 ka BP (1 ka: 1000 years). MS and LOI analyses were carried out in this study. The down-core MS scanning was carried out in 1-cm increments using a Bartington MS2C sensor. The Organic Matter content (OM), calcium carbonate content (CaCO3) and minerogenic content of the core was determined by analyzing 85 sediment samples.
    3-Results and discussion
     The results of MS measurement represent a similar trend to the results of minerogenic content of the core, indicating the role of minerogenic components in controlling the MS signal. While they display an opposite trend to the OM content results. Basically mineral particles can be transported into the wetland by water or wind transportations. If they are transported by the water running from the karst aquifer, no major magnetic mineral is expected to be transposed into the wetland, as the aquifer is developed in a nonmagnetic limestone. Hence, it can be concluded that the correspondence between MS and minerogenic content is as a result of the deposition of magnetic dust particles in the wetland during the enhanced aeolian activities. Therefore, we interpret the MS signal as dust input in our record.Based on variations in the LOI and the MS results the core can be divided into five zones. A) 22-15.4 ka BP: This zone is characterized by minimum OM content, maximum CaCO3 content and very low to negative MS values, indicating a lacustrine environment with no major dust input. The pollen-inferred vegetation corresponding for this period indicates the dominance of a cold, dry Artemisia-Chenopodiaceae steppe (Safaie-Rad et al., 2014). Therefore, although the climate has been drier than present, the smaller amount of precipitation has sustained for a longer time and caused a lake to form under a cold climate in which the evaporation rate was substantially suppressed. B) 15.4-10.5 ka BP: A sharp change in the lithology from marl to gyttja indicates an environmental change from lacustrine to palustrine at 15.4 ka BP onward. This change most likely has occurred due to a notable increase in the temperature which is in agreement with a concurrent rise of the temperature inferred from changes in the diatom assemblages of the nearby Lake Zeribar (Wasylikowa et al., 2006). The increase in the MS values reflects higher dust input in this zone than the underlying zone. C) 10.5-7.8 ka BP: This zone is characterized by maximum minerogenic content and MS values vs. very low OM content (minimum in the Holocene section of the record), indicating intensified dust input into the wetland through the enhanced aeolian activities. The period between 9 and 7.8 ka BP exhibits the peak of dust input, which is in accordance with the desiccation of the wetland and consequently decay of the pollen grains in this time (Safaie-Rad et al., 2014). By contrast, a short-term interval at around 9.2 ka BP, represents an abrupt decline in the dust input probably due to the alleviation of aridity. D) 7.8-6 ka BP: A decrease in the MS signal and minerogenic content reflects a reduction in dust input, suggesting a decrease in aridity in compare to the previous zone. E) 6-2.2 ka BP: This zone is characterized by the Maximum OM content and decline in the MS values and minerogenic content, suggesting a wetting in the climate. This is supported by the expansion of the Zagros oak woodlands at around 6 ka BP (van Zeist and Bottema, 1977; Safaie-rad et al., 2014).These variations in the Holocene climate of the Zagros Mountains are completely opposite to the variations in the Indian Summer Monsoon (ISM) intensity recorded in the speleothem records from Oman and Yemen (Fleitmann et al., 2007), indicating the role of insolation changes in controlling the climate of Zagros Mountains.  
    4- Conclusion
     In this study we generated the first high-resolution paleoclimate record for the Zagros mountains by measuring MS of a sediment core retrieved from Hashilan Wetland and compared our results with the regional paleoclimate records. Following conclusions can be derived from our results  Hashilan has been a lacustrine environment from 22 ka BP (the bottom of our record) until 15.4 ka BP and changed to a palustrine environment from 15.4 ka BP onwards. The MS signal of Hashilan wetland, as the indicator of dust input, along with the LOI results revealed an out-of-phase relationship between the moisture evolution in the Zagros Mountains and the ISM domain during the Holocene. During the early Holocene (10.5-7.8 ka BP) the Zagros Mountains has experienced a dry climate characterized by enhanced aeolian activities, as reflected in high MS values particularly between 9 and 7.8 ka BP. It is most probably as a result of the longer establishment of the STHPs over the Zagros Mountains which protracts dry summer season. After 7.8 ka BP, the abrupt decrease in the MS values vs. increase in the OM content which culminates at 7.5 BP, suggests an alleviation in aridity. In the period between 7 and 6 ka BP the aridity increases again but does not reach to its intensity in the early Holocene. During the Mid-late Holocene (6-2.2 ka BP [top of our record]), low dust input and high OM content reflect a wetter climate.
    Keywords: Holocene, Indian Summer Monsoon, Insolation, Paleoclimatology, Zagros Mountains
  • Mohammad Akhavan* Pages 273-290
    Mirak (Semnan, Iran) is a Paleolithic site located in a dry floodplain near the northern edge of the Iranian Central Desert. The pedo-sedimentary successions of Mirak 8 are deposited from late Pleistocene to Late Holocene,. The chronological framework was established using optically stimulated luminescence (OSL) dating. The oldest studied units dating back to ~50 ± 3.0 ka. Within this stratigraphy, two distinct depositional environments are recognizable: Sequence I = alluvial floodplain deposits and Sequence II = calcareous aeolian deposits. The alluvial succession is represented by alternating horizons of poorly pedogenized bodies of loam, intercalated by splay sand interbeddings. The prehistorical remains occur exclusively at distinct limits and it is presumable that some prehistorical layers of Mirak are palimpsests resulted from repeated occupations. After ~1.2 ± 0.2 ka  an at least 3 ka long sedimentary hiatus cuts the sedimentary log of Mirak 8 and about 2m of aeolian assemblages take place over the discontinuity. This shift was clearly reflected in the laboratorial results. Results from XRD, FTIR, SEM and optical microscopy analyses, show very minor differences in mineralogy for the entire record regardless of the type of depositional regime and this we suggests a local and most probably polygenetic source for the deposits under study. Subsequent to deposition, both alluvial and aeolian accumulations were subjected to different extents of pedogenesis and thus developed pedogenic features characteristic of Entisols and calcareous, gypsiferous Aridisols (Bk, By). Varying iron content and different oxygenizing conditions between the two sequences are presumably relatable to higher ground water level and Fe-reducing conditions especially for the units deposited prior to ~28 ± 2 ka BP (OSL) and generally adverse conditions for the Holocene units.
    Keywords: paleolithic, sedimentology, quaternary geology, mirak
  • Mahsa Abdollahi* Pages 291-305
    This paper bolded Because of focusing on the construction of acceleration maps in the Saveh area which based on seismicity. This Method, applies the identifying seismic sources, calculation of seismic parameters and involvement of historical earthquakes in our analyses. At last, by assigning these parameters to seismic sources, analyzes are performing in the EZ-Frisk software. On the basis of these studies, the acceleration maps in the period of close to zero seconds were processed for the returning of 475, 975 and 2475 years. According to these maps, the maximum acceleration values are 0.49, 0.69, and 0.94 g correspond to the return periods of 475, 975 and 2475 years, respectively
    Keywords: : acceleration maps, seismicity rate, EZ-Frisk software
  • Ahmad Azadi* Pages 307-319
    Introduction
    The transition from hunter-gatherer to farmer- herder is one of the most important issues in archaeological research of the Holocene period. The Zagros region of Iran, especially its central parts, has had an important role in initial phases of Neolithic research in Iran. Until a decade ago, lack of evidence on the transitional period between the end of the EpiPalaeolithic period and the beginning of the Neolithic period, caused some researchers believe that southern Zagros has received food-producing subsistence from other regions such as the Central Zagros. New investigations in the southern Zagros have shed a new light on the issues regarding the neolithisation process at the region.
    Materials and methods
    The region of Kohgiluyeh, at an elevation between 500 to 3600 meters above sea level, located in the southern Zagros highlands, has a high potential to tracking the transition from Epipalaeolithic to the Neolithic period. Based on archaeological surveys of Kohgiluyeh region, 16 sites from early Holocene period were identified. Regarding the typology of the sites, they include 5 mounded sites, 8 open sites, 2 rock shelters and one cave site. Our main criteria for assigning these sites to pre- pottery Neolithic period is the lack of Neolithic potteries on the surface of them and existence of bladelet and bladelet cores with pressure technique. Obviously, the assignment of at least a number of these sites to pre- pottery Neolithic period can be considered cautiously and it is possible that future research confirms or refutes it. The methodology of this research is processing the information fathered from archaeological surveys of the Kohgiluyeh region. The emphasis in this paper is on the lithic analyses collected from the surface of the sites.
    Results and discussion
    Geologically, mounded sites of the Neolithic period in the Kohgiluyeh region are formed in various landscapes include rolling hills landscape of the Maroun River, Dehdasht plain and foothills of the Khaeez mountains. The sites are sit at 674 to 1586 m above sea level and their areas are between 3.5 to 0.5 ha. Concentrations of the mounded sites are seen in the southern half of the Kohgiluyeh region which has an arid climate. Formation of these settlements in various landscapes indicates that the region has had a high potential to attract human groups of this period. Open sites are located in two mountainous and marginal landscape of the Sour and Maroun Rivers. These sites are sit at 599 to 1036 m above sea level and their areas are between 3.4 to 0.25 ha. It seems that the main factors in formation of these sites were their proximity to mountain and water sources. Two rock shelters and a cave identified from the survey are located in southeastern parts of the region, about 900 m above sea levels. They are opened to the east and their areas are between 6 to 100m2.        Stone artifacts of chert are the most common classes of raw materials recovered from surface of the sites. It seems that, the chert which is often of dark yellow, green, gray, red and dark red color came from of local origin such as the Bakhtiyari Conglomeratic and river pebbles. Generally, in terms of the technological structure, stone tools can be classified into four main groups including core/core fragments, debitage, tools and debris. Cores include numerous single and double platform bullet cores and few flake and mixed cores (bladelet and flake cores and blade and bladelet cores). The debitage is almost exclusively bladelet and flake based.Tools are the main group of stone artifacts and some of them are include bladelet with continuous fine retouch on one and two edge, backed bladelet, bladelet with inverse retouch on both edges, end-scraper and simple burin on a flake.ConclusionAs mentioned above, 16 sites attributed to the early Holocene period were identified. Of these, 1 site is located in the Dehdasht plain, 5 sites near the Maroun River, 6 sites in mountainous landscape and 4 sites in mouth and inside of the gorges. Generally, settlement and subsistence patterns of these sites are affected by several factors such as plain, river, mountains and gorges. It seems that during this period, the plains have not been under attention enough but the mountainous landscape and margin of the rivers such as Maroun River has had a main role in attracting the human groups.
    Keywords: Holocene, Southern Zagros, Kohgiluyeh, pre- pottery Neolithic
  • Fatemeh Bagheri Pages 321-339
    Surface and groundwater resources such as Arnaveh karstic spring and Shirin Dareh reservoir are the main sources of drinking water and agricultural activity in the North Khorasan province, northeast of Iran. The main agents of this study are to evaluate the origin, hydrochemical and isotope characteristics of water resources and also suitability of the Shirin dareh reservoir water for drinking and agriculture usages. Water samples were collected in October 2017 from Arnaveh Spring, Shirin dareh River and dam reservoir to measure the EC, TDS, major ions concentrations and stable isotopes (δ18O, δ2H) values. Furthermore, the two rain stations were selected for isotope sampling from rain waters and determining the Shirin dareh isotope Meteoric Water Line. According to hydrochemical characteristics, Ca-Mg-SO4 and Ca-Mg-HCO3 are the dominance waters type in the area. The average electrical conductivity is about 900 µS/cm. The δ2H = 7.14 δ18O + 5.67 (R= 0.96) equation is proposed as LMWL of the study area based on the precipitation samples. Its slope and intercept are lower than the GMWL due to secondary evaporation from rain drops in low humidity condition. The isotopic results suggested that the Arnaveh spring and surface waters (river) are originated from modern atmosphere precipitation. Due to evaporation, isotope composition is more enriched in dam reservoir than in river samples and has a slight deviation from the local meteoric water line. The quality indexes confirm that these water resources is suitable for Irrigation and drinking usages.
     1-Introduction
    Shirin Dareh Basin is located in northeast of Iran. Shirin Dareh dam is the main source of drinking water and agricultural activity in the Northern Khorasan region. The geochemical investigation provides more information about ground and surface waters mineralization and the processes controlling the deterioration of water quality. Water quality in dams depends on the geological characteristics of the catchment area, the quantity and quality of water entering the reservoirs of dams, the amount of precipitation and the amount of agricultural and industrial activities. Sustainable management of the water resources needs a comprehensive understanding of the sources of water and spatial variability of hydrochemical and isotope characteristics. Water isotopes are commonly used for determining the sources of surface and groundwaters. The aim of this study was to investigate the spatial variations of water quality in the river and Lake of Shirin Dareh dam, as well as the origin and chemical evolution of water resources with different methods of hydrogeochemical and isotopic methods. This type of study was carried out for the first time in this area, and in addition, the local precipitation line of the isotopic rainfall in the Shirin Dareh area was also measured and plotted.
    2-Materials and methods
    Samples were collected for one period (October 2017) from Arnaveh spring, Shirin Dare River and dam reservoir. Electrical conductivity, total dissolved solids, major ions (Ca, Mg, Na, K, HCO3, SO4, Cl, NO3) and stable isotope (18O,2H) were analyzed. Furthermore, isotope values of the precipitation samples in two rain gauge stations in the study area were also measured to determine the isotope meteoric water line. Hydrochemical diagrams, such Piper, Schoeller, Chadeha, different ions ratio, Gibbs and Saturation Index (SI) were used to evaluate the hydrogeochemical characteristics. Six factors such as residual sodium carbonate (RSC), magnesium adsorption ratio (MAR), sodium percentage (%Na), sodium adsorption ratio (SAR), Permeability Index (PI), and water quality index (WQI) were calculated to evaluate the water quality within the research area for irrigation and drinking activities.
    3-Results and discussion
    According to the Piper and Chadeha diagram, Ca-Mg-SO4 and Ca-Mg-HCO3 are dominance type of water. Gibbs plot showed that all of the samples fall in the rock dominance. The hydrochemistry results and different ions diagrams indicated that the most important factors controlling the chemistry of water included carbonate, anhydrite and gypsum dissolution and to a lesser ion exchange process. The most of water samples are saturated or oversaturated with calcite, dolomite, gypsum and anhydrite.  Dissolution of halite is negligible; therefore, SI of halite is under saturated in the study area. Arnaveh karstic spring with lower EC value has the effective role in improvement of water quality of the Shirin Dare River. The average of electrical conductivity is about 900 µS/cm. All river and dam samples are plotted between the mixing line of the two samples of upstream and Arnaveh spring; indicate that the water quality of the river after mixing with the spring has improved and the concentration of ions has decreased too.  Many factors such as evaporation and water-rock interaction can control the relative abundance of an isotope in surface water compared to the precipitation. According to the isotope composition of the precipitation samples, The LMWL equation is computed as δ2H= 7.14 δ18O + 5.67 (R= 0.96). Its slope and intercept due to secondary evaporation from rain drops in low humidity condition are lower than the GMWL. The isotopic results suggested that the Arnaveh spring and surface waters (river) are originated from modern atmosphere precipitation. Due to evaporation, isotope composition is enricher in dam reservoir than in the river samples. The isotopes stability signatures show that river samples are non-evaporated and controlled by the dissolution, whilst reservoir samples are more 18O and 2H-enriched due to the evaporation from reservoir surface. The quality indexes confirm that these water resources is suitable for Irrigation and drinking.
     4- Conclusion
    To summarize the geochemical and isotopic techniques and water quality indexes were used to evaluate the origin and chemical evolution of surface and groundwaters in the study area. The groundwater samples from Arnaveh spring is mainly affected by natural factors and processes such as lithology, evaporation and water-rock interaction. The isotope composition (18O and deuterium) indicates the importance of evaporation in dam reservoir, and recharge with modern rainfall. The water quality in the study area seems to be good for different usages.
    Keywords: Hydrochemistry, Isotope characteristics, LMWL, quality indexes, Shirin dareh
  • Mazaher Moenoddini* Pages 341-360
    1-Interoduction
      Air pollution has been considered as one of the global challenges. According to world health organization (WHO), dust particles are the 5th most dangerous cause of death 4.2 million in the world. According to the world meteorological organization (WMO), when the wind speed increases more than 15 m/s and the visibility decreases because of dust particles less than 1 km, it is called a dust storm. Considering the potential impact of dusts around the city of Qom, it is possible to influence the impact of dust storms on the extent of these centers and their contribution to the air quality of the city of Qom in the aftermath of a storm of dust.The dust storms that affect Qom are originated from two local and transitional emission sources. The main objectives of this study were identification of the main quaternary geological structures as emission sources of dust storms, study dust storms paths and determine the important emission sources that are affect Qom air quality.
    2-Material and methods
    Initially, dust storms were detected using dust codes and verification of MODIS images during the period 2008 to 2017. Remote sensing is a suitable method for detecting dustborne events and has recently been successfully used to understand the location of dust sources. The position of geological formations at the site of the focal points indicates that the bed of most of the focal points is from quaternary deposits. The Quaternary geological period is the fourth and final period of geology, and most of the constituent parts of these centers, including the ancient coniferous terraces and clay alluvial tundra, are prone to dust production. This study were trajectory using HYSPLIT model and orientation index (windrose, dust rose and CPF). In order to investigate the wind condition as one of the most important factors in dust storms, windrose and dust rose were used using WRPLOT software. One of the common ways to identify the geographic direction of dust sources is the CPF function. The CPF examines the potential of any direction in the transfer of pollutants, especially particulate matter released from a source in which the wind is greater than the specified threshold. The HYSPLIT model is one of the most practical methods for determining the duct movement, dispersion and dip galvanizing simulationThe model of the propagation algorithm was identified for each occurrence and was investigated at three altitudes of 10, 500 and 1000 m in backward for 24 hours for local Events and 72 hours for transitional Events.
    3-Results and discussion
    Out of 531 identified events, after verification by dust codes and MODIS images, 400 events were detected in Qom between 2008 and 2017 years about 84 percent of the incidents occurred in the spring and summer. The results of windrose and dust rose indicate that east and west directions have the highest wind direction in Qom, which are differents in different seasons, and the results of windrose are more similar to the seasonal results of summer and spring, the occurrence of most events in two seasons spring and Summer shows. Seasonal CPF results with slightly different windrose and dust rose results, show the northwest and east directions in the spring and summer, and northwest in the autumn and winter seasons. Due Because of the CPF shows the potential for dust production and most of the events occurred in the spring and summer season, the results of the windrose spring and summer and dust rose were similar and confirm the occurrence of this dust numbers in the two seasons of spring and summer In these directions. The results of HYSPLIT At three altitudes of 10, 500 and 1000 meters in the period from 2008 to 2017 in Qom Due Because of the two altitudes of 1000 and 500 meters are far away from the phenomena and topographic changes of the Earth, they have little effect on the dusts. Dust routing results at 10 m elevation were studied. The results of trajectiries the HYSPLIT model at 10 m elevation in the study period in Qom show that the most important directions of dust entering the city of Qom, Like the results of wind rose, dust rose and CPF, it is east, southeast, west, and southwest, who There are many events in the east and south-east of the west and southwest, and From these directions, there is no significant dusting in the southwest direction around the city of Qom, and in other directions there are many dusty centers. Investigating the frequency and direction of the dust storm trajectory occurring in Qom during the studied period shows that the most important centers dust that affect the air quality of Qom city, where the threat of more events has passed, Respectively, the centers of numbers 4, 10, 11 and 2 are located among these centers, centers numbers 4, 10 and 11 in the direction of east and south-east of the city of QomThe center number 2 is located west of the city of Qom, and this direction was also Is important recognized by the results of wind rose, dust rose and CPF. Also, the results of the HYSPLIT model trajectory for transitional dusts Which has influenced the city of Qom during the studied period, shows that most of these dusts from the country are than Iraq, then Syria and Saudi Arabia.4-ConclusionThere are several dusts centers around the city of Qom. Among these centers, the center of number 4 (the distance between salt lake and Houz-e-Sultan), located east of Qom, is due to the close distance, high area, the genus of the formation and, most importantly, the abundance The passage of events from this center, which includes the largest number, and centers of numbers 10, 11 and 2 too After the center of number 4, is the most important and most influential source of dust on the city of Qom relative to other centers.
    Keywords: Dust Storm, HYSPLIT, Dust Rose, CPF