فهرست مطالب

  • سال دوازدهم شماره 1 (پیاپی 22، بهار و تابستان 1398)
  • تاریخ انتشار: 1399/04/31
  • تعداد عناوین: 8
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  • الهام اسدی مهماندوستی*، جهانبخش دانشیان، نعمت الله مارگیر صفحات 1-22

    سازند قم در برش چینه شناسی خانی‎آباد واقع در جنوب خاور کاشان با ستبرای 70 متر از سنگ آهک‌های ستبر، متوسط، نازک لایه، سنگ آهک‌های رسی و دولومیتی به همراه مارن تشکیل شده است. این سازند در رخنمون مورد مطالعه با مرزهای ناپیوسته فرسایشی در میان سنگ‌های قاره‌ای سرخ رنگ (سازندهای سرخ زیرین و بالایی) جای دارد. اگرچه بر روی سازند قم مطالعات مختلفی از نظر چینه‎نگاری و سنگ‎‎شناسی صورت گرفته است، اما با توجه به متغیر بودن شرایط رسوب‌گذاری سازند قم در مکانهای مختلف، نمی‌توان یک محیط رسوب‌گذاری خاص را برای آن در نظر گرفت. بررسی 98 نمونه‌ تهیه شده از این برش خانی‎آباد به شناسایی 9 ریزرخساره در 2 کمربند رخساره‌ای لاگون و سد و یک پتروفاسیس مارنی منجر شد. با توجه به بررسی‌ها و مشاهدات صحرایی (ناپیوسته بودن آثار ریفی)، فراوانی رخساره‎های با بافت پکستونی حاوی موجودات قشرساز لاگون نزدیک ریف مثل جلبک و بریوزویر، فراوانی رخساره‎های باندستونی مرجانی در حجم کم اما به تعداد زیاد و نبود رسوبات ریزشی در بخش‌های عمیق‌تر حوضه، مدل رسوبی سازند قم در ناحیه خانی‌آباد (جنوب خاور کاشان) یک سکوی کربناتی بدون لبه (شلف باز) در نظر گرفته شده است. از آن جا که بیشتر ته‌نشست کربنات‌ها در این توالی مربوط به بخش کم‌عمق لاگون بوده است، زمینه اغلب ریزرخساره‌ها را میکرایت تشکیل داده است که کمتر تحت تاثیر فرآیندهای دیاژنزی قرار گرفته است. سیمانی شدن و دولومیتی شدن بیشتر در ریزرخساره‎های سدی این برش دیده می‌شود.

    کلیدواژگان: سازند قم، ریزرخساره، محیط رسوبی، فرآیندهای دیاژنزی، ایران مرکزی
  • انسیه بهدانی، فاطمه هادوی*، مرضیه نطقی مقدم، احمدرضا خزاعی صفحات 23-34

    در این پژوهش، سازند بغمشاه در برش چینه شناسی دهشک واقع در شمال باختر قاین (شمال بلوک لوت) برمبنای نانوفسیل های آهکی مورد بررسی قرار گرفته است. ضخامت سازند بغمشاه در این برش 896 متر بوده و متشکل از شیل، مارن و مقادیر کمی سنگ آهک ماسه ای است. نتیجه این مطالعه، شناسایی 55 گونه متعلق به 26 جنس از نانوفسیل‌ های آهکی است. برمبنای گونه ‌های موجود و مقایسه با زون‌بندی نانوفسیل‌های آهکی در منطقه تتیس، سن رسوبات مطالعه شده سازند بغمشاه بریازین پیشین تا بارمین پیشین پیشنهاد می‌شود که مطابق با زیست زون ‌های CC1 تا CC5 از زون‌بندی (Sissingh (1977 می‌ باشد.

    کلیدواژگان: زیست چینه نگاری، نانوفسیل های آهکی، بغمشاه، دهشک، بلوک لوت
  • مهدی رضا پورسلطانی*، نسترن کاظمی زنجانی لطف آبادی، محمدابراهیم فاضل ولی پور صفحات 35-53

    کارده یکی از مهمترین حوضه های آبریز در استان خراسان رضوی است که در شمال شرق شهرستان مشهد قرار دارد و تامین کننده قسمتی از آب شرب و کشاورزی منطقه محسوب می‌گردد. بخش عمده منطقه توسط سازندهای کربناته مزدوران و سیلیسی آواری شوریجه و بخش کمتر توسط رسوبات نیوژن و عهد حاضر پوشیده شده است. هدف اصلی این پژوهش، مطالعه کیفیت آب‌های سطحی و تاثیر سنگ شناسی منطقه بر آن است. بر اساس آنالیزهای نمونه‌های سنگی واحدهای کربناته، سیلیسی آواری و تبخیری، منشا احتمالی افزایش غلظت کاتیون‌های کلسیم، منیزیم، آهن، سدیم، آلومینیم و همچنین آنیون‌های سولفات و بیکربنات محسوب می‌گردند. بر اساس نتایج حاصل از مطالعات انجام شده و مطابقت آنها با استاندارهای بهداشت جهانی و ایران و استفاده از نمودارهای شولر، ویلکاکس و پاپیر، وجود مقدار ‌یون‌های کلسیم، منیزیم، سدیم، پتاسیم، کلر و سولفات و همچنین میزان اسیدیته، مواد جامد محلول در آب و سختی کل، سبب گردیده که آب حوضه آبریز کارده به دلیل خورندگی و رسوب‌گذار بودن جهت مصارف صنعتی مناسب نباشد. همچنین برخی نمونه‌های آبی، گرچه از نظر وجود کاتیون‌های سدیم و منیزیم و آنیون سولفات خوب تا قابل قبول بوده، اما به دلیل وجود TDS و TH بالا از نظر شرب انسانی نامناسب هستند. از سویی، عمده آب‌های حوضه آبریز کارده دارای کیفیت خوبی بوده و به طور عمده سولفات و کلسیم ‌یون‌های غالب محسوب می‌گردند. لذا نوع آب به طور عمده سولفاته کلسیک است. در نهایت عمده نمونه‌های آب حوضه آبریز کارده در کلاس C2S1 طبقه‌بندی شده که جهت استفاده کشاورزی مناسب هستند.

    کلیدواژگان: حوضه آبریز کارده، خراسان رضوی، سنگ شناسی، کیفیت آب
  • محمدعلی جزی، محمدحسن کریم پور*، آزاده ملک زاده شفارودی صفحات 53-74

    کانسار سرب (نقره) نخلک در حاشیه خاوری کوه نخلک و 55 کیلومتری شهر انارک در استان اصفهان قرار گرفته است. کانی‌سازی در فضای خالی حاصل از شکستگی‌ها، درون سنگ‌های کربناته کرتاسه بالایی (واحد صدر) به صورت رگه‌های خاوری باختری و با شیب زیاد قرار گرفته است. وجود رخساره‌های ریفی، دولستونی و حالت‌های انتقالی بین سنگ آهک و دولستون از خصوصیات سنگ‌شناسی مناسب واحد صدر می‌باشد. سیال کانه‌دار سنگ میزبان را دچار دگرسانی‌هایی شامل انحلال کربنات‌ها و تشکیل کربنات‌های گرمابی نموده که در اطراف رگه‌های معدنی از قبل تا همزمان با کانی‌سازی تشکیل شده است. سه نوع اصلی دولومیت در ارتباط با کانی‌سازی مشاهده شده که دولومیت‌ نوع زین اسبی مهمترین آن‌ها می‌باشد. ژیوشیمی سنگ میزبان مجاور رگه‌های معدنی نشان می‌دهد MgO، Fe2O3 (Fe total)، MnO و نیز عناصری همچون Pb، Ba و Zn غنی‌شده و CaO در سنگ‌های دگرسان شده تهی‌شده که به تدریج با رسیدن به سنگ میزبان غیردگرسان به وضعیت عادی باز می‌گردند. رابطه مثبت مشاهده شده بین شدت دگرسانی دولومیتی، تمرکز عناصر مرتبط با کانی‌سازی و ته‌نشست کانی‌های سولفیدی پیشنهاد می‌کند که مهاجرت سیال کانه‌دار از درون رگه معدنی و توسط فرآیندهای گرمابی به درون سنگ میزبان صورت گرفته است. ارزیابی ماهیت سیال مولد دگرسانی دولومیتی کانسار نخلک نشان‌دهنده سیال شوراب حوضه‌ای (میانگین 11/14درصد وزنی نمک طعام) با دمای متوسط (میانگین 174 درجه سانتی‌گراد) بوده که تقریبا مشابه با سیال مولد کانی‌سازی کانسار است. در کانسار نخلک تاثیر متقابل سنگ میزبان کربناته و سیال کانه‌دار در طول فرآیند کانی‌سازی به صورت بازخوردی عمل نموده است، به طوری که سنگ میزبان کربناته مناسب (از نظر شیمیایی و فیزیکی) عامل ورود سیال کانه‌دار به درون سنگ‌ میزبان باعث تشکیل کانی‌سازی شده و خود کانی‌سازی باعث انحلال کربنات سنگ میزبان و ته‌نشست دولومیت شده و این رخداد‌ها با ایجاد فضای خالی بیشتر امکان ته‌نشست ماده‌ معدنی بیشتر را فراهم نموده است.

    کلیدواژگان: دولومیت، پتروگرافی، ژئوشیمی، سیال درگیر، شوراب حوضه ای، نخلک
  • علی رجب زاده، حسین کوهستانی، میرعلی اصغر مختاری، افشین زهدی* صفحات 75-90

    منطقه چهرآباد در شمال خاور ماه‌نشان و در فاصله 75 کیلومتری شمال ‌باختر زنجان قرار دارد. واحدهای سنگی رخنمون‌ یافته در این منطقه متعلق به سازندهای قرمز زیرین، قم و قرمز بالایی می‌باشند. سازند قرمز بالایی در این منطقه 980 متر ستبرا داشته و از 3 بخش اصلی تشکیل شده‌ است. این بخش‌ها به‌‌ترتیب شامل واحدهای تبخیری با ستبرای 235 متر در پایین، تناوبی از گل‏سنگ و ماسه‌سنگ‌های خاکستری‌ تا قرمز رنگ با ستبرای 590 متر در بخش میانی و افق‌هایی از گل‏سنگ‌‌های سبز با میان‌لایه‌های ژیپس با 155 ستبرا در بخش بالایی می‌باشد. توالی انتخاب شده جهت مطالعات چینه‌شناسی و رسوب‌شناسی مربوط به بخشی از قسمت دوم سازند قرمز بالایی با 231 متر ستبرا می‌باشد. این توالی شامل هفت لایه‌ ماسه‌سنگ خاکستری و قرمز رنگ است که به‌ صورت متناوب با واحد‌های گل‏سنگی قرمز رنگ قرار گرفته‌اند. بر پایه مطالعات پتروگرافی، این ماسه‌سنگ‌ها به‌ طور میانگین حاوی 21% کوارتز، 10% فلدسپات و 25% خرده‌سنگ بوده و از نوع فلدسپاتیک‌لیت‌آرنایت و لیت‌آرنایت‌ می‌باشند. بر اساس شواهدی نظیر چینه‌بندی متقاطع، حضور آثار گیاهی، نبود رسوبات گراولی، ریپل‌مارک‌های متقارن و آثار موجودات حفار و شناسایی 7 رخسار‌ه‌ ماسه‌سنگی گل‌سنگی (Fl، Fm، Sm، Sh، Sr، Sp و St) در منطقه‌ چهرآباد می‌توان بیان داشت که محیط رسوبی این واحد‌های سنگی، رودخانه‌های میاندری ماسه‌ای با پیچش زیاد نزدیک به محیط ساحل می‌باشد. براساس نتایج آنالیز مودال و بررسی نسبت بین کوارتزها، خرده‌سنگ‌ها و فلدسپات‌ها، موقعیت تکتونیکی این ماسه‌سنگ‌ها حاشیه‌های فعال‌ قاره‌ای و برپایه‌ اطلاعات ژیوشیمیایی و نسبت‌های SiO2/Al2O3 در مقابل K2O/Na2O، حاشیه‌های فعال‌ قاره‌ای و حوضه‌های فورلندی می‌باشد.

    کلیدواژگان: رخساره های رسوبی، جایگاه تکتونیکی، ماسه سنگ، سازند قرمز بالایی، چهرآباد، زنجان
  • بهزاد سعیدی رضوی*، فاطمه عسکری، محمدرضا کمالی، عزت الله کاظم زاده صفحات 91-108

    در این پژوهش، سازند سروک با سنگ شناسی غالب سنگ آهکی و ضخامت 323 متر، در یکی از میادین نفتی جنوب واقع در 100 کیلومتری غرب اهواز مورد مطالعه قرار گرفته است. به دلیل وجود ندول‌های گلوکونیتی در قاعده سازند گورپی، مرز بالایی سازند سروک با سازند گورپی به صورت ناپیوسته در نظر گرفته شده است. مرز زیرین سازند سروک نیز به علت عدم حفاری توالی زیرین آن مشخص نیست. بر اساس مطالعات دیرینه شناسی انجام شده، 5 جنس و 5 گونه از میکروفسیل‌های شناور و 25 جنس و 28 گونه از میکروفسیل‌های کف‌زی شناسایی شدند و براساس آنها سه زیست‌زون‌ شامل Nezzazata–alveolinids assemblage zone، Rudist debris zone و Oligosteginid flood zone معرفی شدند. این زیست‌زون‌ها که با زیست‌زون‌های معرفی شده توسط (Wynd (1965 مطابقت دارند، موید سن سنومانین تا تورونین برای سازند سروک در چاه مورد مطالعه هستند. بر پایه مطالعات سنگ نگاری، تحلیل بافت‌های رسوبی و فسیل‌های موجود، هفت ریزرخساره مختلف در توالی سازند سروک شناسایی شد. بر این اساس، محیط رسوب‌گذاری سازند سروک در این منطقه شامل سه بخش لاگون، شول و دریای باز متعلق به یک رمپ کربناته می‌باشد. بررسی‌های چینه‌نگاری سکانسی نیز به شناسایی یک سکانس رسوبی کامل و دو سکانس ناقص در سازند سروک انجامید.

    کلیدواژگان: زیست چینه نگاری، ریزرخساره، چینه نگاری سکانسی، سازند سروک، سنومانین تورونین
  • بهاره شاکری، حسین وزیری مقدم، علی بهرامی*، پیتر کونیگشوف، محمدعلی صالحی صفحات 109-132

    به منظور بررسی ریزرخساره‌ها و محیط رسوبی سازند بهرام در جنوب خاوری انارک، برش چینه شناسی کوه بندعبدالحسین انتخاب و مورد مطالعه قرار گرفت. سازند بهرام در این برش 366 متر ضخامت دارد و سنگ شناسی آن شامل سنگ آهک‌ های نازک تا ضخیم لایه، تناوب سنگ آهک‌ ها و شیل‌های نازک لایه، سنگ آهک ‌های ماسه ‌ای و سنگ آهک ‌های مارنی است. براساس تغییرات رخساره ای و ویژگی‌های سنگ شناختی 16 ریزرخساره در این برش تشخیص داده شده است. بررسی رخساره‌های شناسایی شده حاکی از ته‌نشینی این ریزرخساره‌ها در یک رمپ کربناته در زمان دونین میانی و پسین است. بررسی ‌های چینه نگاری سکانسی سازند بهرام بر مبنای تغییرات عمودی ریزرخساره‌ها و مقایسه آن‌ها با منحنی تغییرات سطح آب دریا به شناسایی 7 سکانس درجه 4 در برش مورد مطالعه منجر شده است. با توجه به اطلاعات به دست آمده، سکانس رسوبی اول و هفتم قسمتی از سکانس ‌های رسوبی می‌ باشند و سکانس‌ های رسوبی دوم تا ششم سکانس‌ های رسوبی کامل و دارای دسته رخساره‌های پیش‌رونده، پس‌رونده، بیشینه سطح غرقابی و مرز های سکانسی هستند.

    کلیدواژگان: سازند بهرام، محیط رسوبی، چینه نگاری سکانسی، ژیوتین بالایی فامنین بالایی، کوه بندعبدالحسین
  • محسن علامه* صفحات 133-145

    سازند سنگانه یکی از سازندهای حوضه رسوبی کپه‌داغ  به سن کرتاسه پیشین است که محیط زیست دیرینه و رخساره‌های پالینولوژیکی آن در برش امیرآباد مورد مطالعه قرار گرفته ‌است. سنگ شناسی عمده سازند سنگانه در این برش شامل شیل‌های خاکستری تیره ‌است که در بعضی از افق‌ها، حاوی کنکرسیون، مخروط در مخروط و فسیل‌های آمونیت می‌باشد و 530 متر ضخامت  دارد. مرز زیرین آن با سازند سرچشمه توسط یک لایه سنگ آهک فسیل‌دار مشخص می‌شود و مرز بالایی آن با سازند آیتامیر با گذر تدریجی است. برای مطالعه رخساره پالینولوژیکی و محیط دیرینه سازند سنگانه تعداد 50 نمونه با فواصل معین برداشت شد و پس از آماده سازی نمونه‌ها بر اساس میزان خرده‌های آلی در اسلایدهای پالینولوژیکی، سه رخساره پالینولوژیکی مختلف شناسایی گردید. با توجه به بررسی گروه‌های اصلی پالینولوژیکی و نتایج مطالعات آماری می‌توان چنین استنباط کرد که محیط رسوبی سازند سنگانه در زمان رسوب‌گذاری محیطی کم‌اکسیژن تا فاقد اکسیژن بوده‌است. همچنین با توجه به داینوسیست‌های شاخص، محیط رسوبی دریای حاشیه‌ای، تا دریای باز کم ژرفا برای سازند سنگانه در زمان رسوب‌گذاری پیشنهاد می‌شود.

    کلیدواژگان: پالینومرف، رخساره پالینولوژیکی، محیط دیرینه، کپه داغ، سازند سنگانه، امیرآباد
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  • Elham Asadi Mehmandosti*, Jahanbakhsh Daneshian, Nematollah Margir Pages 1-22
    Introduction 

    During the Late Oligocene -Early Miocene time, the western border of central Iran (Qom, Hamedan, Kashan and Tafresh) to the southern margin of Jazmurian and some regions of Azerbaijan as well as in the Zagros a carbonate platform formed with evidence as a vast marine progradation that was a part of the horst of Pyrenean tectonic phase. The carbonate succession is named Asmari Formation in Zagross and Qom Formation in Azerbaijan and Central Iran (Aghanabati, 2006). Due to the economic importance of the Qom Formation as a hydrocarbon reservoir and the presence of celestite and chalk deposits, this formation is important to study. Although lots of stratigraphic and lithologic studies are done on the Qom Formation, due to variations in depositional environment of the Qom Formation in different locations, it is not possible to consider one type of sedimentary environment for this formation (e.g. Seyrafian et al., 2007; Mohammadi et al., 2009; Reuter et al., 2009; Safari et al., 2014; Daneshian et al., 2017; Nasiri Ghareh Shiran, 2017). In this research, the Qom Formation was studied in Khani Abad stratigraphic section in the southeast Kashan. The aim was to investigate microfacies, sedimentary environment and diagenetic features of Qom Formation in this area.

    Methods and Material

    During the field study, sampling was performed systematically. 98 samples were collected from the Qom Formation in Khani Abad section with a thickness of 70 meters. It contains 36 soft and 62 hard samples. The sampling distance in carbonate parts was several centimeters in some areas, based on facies variations. Thin sections were prepared from hard samples. All thin sections were stained with potassium ferricyanide and alizarin-red S solution (Dickson, 1965). The petrographic classification for carbonates is based on the Dunham (1962) and Embry and Klovan (1971) classification schemes. In this study, Dolomite textural classified based on Sibley and Gregg (1987) and Mazzullo (1992) and for the size of dolomite crystals from the scale provided by Folk (1974). Wilson (1975), Pomar (2001) and Flügel (2010) facies belts and sedimentary models were also used.

    Discussion 

    The Qom Formation in Khani Abad stratigraphic section, southeast of Kashan has 70 m thickness and is composed of thick, medium and thin-bedded limestone, argillaceous limestone, dolomitic limestone and marl. This formation with erosional boundaries located between the red color non-marine rocks (the Lower and Upper Red formations). Investigations of 98 selected samples in this outcrop led to the recognition of 9 microfacies in 2 lagoonal and shoal facies belts and a marl petrofacies. The lagoonal facies are A1: Benthic Foraminifera, Bioclast Grainstone, A2: Bioclast Wackestone, A3: Benthic Foraminifera Packstone to Wackestone, A4: Bryozoan Bioclast Packstone, A5: Bivalve Packstone. A6: Bryozoa, Bivalve, Bioclast Packstone and A7: Benthic Foraminifera Red Algae Packstone to Wackestone. The shoal facies are B1: Coral Boundstone and B2: Bioclast Red Algae Grainstone. Micritization, bioturbation, cementation, dissolution, neomorphism, replacement and dolomitization are the main diagenetic features in the studied area.

    Conclusion

    According to field observations (discontinuous reef traces), the abundance of packstone facies which consist of encrusted organism related to lagoon toward the reef such as algae and bryozoa, abundance of coral boundstone facies in a low volume but large quantity and absence of gravitational sediments, the sedimentary modal of the Qom Formation in Khani Abad section (southeast of Kashan) had to be considered as non-rimmed carbonate shelf (open shelf). In the middle and top of the stratigraphical column of the Qom Formation, the amount of benthic foraminifera with porcelaneous walls reduced, while the amount of bioclast increased, which indicates normal salinity during deposition of these parts. Regarding to the degree of light penetration and according to the porcelaneous and hyaline foraminifera, the euphotic to mesophotic zones can be suggested for the study section. Since most of the carbonate sediments were deposited in shallow depth of lagoonal environment, the matrix is dominant, therefore these sediments have undergone less diagenetic processes. Cementation and dolomitization were seen mostly in shoal microfacies parts.

    Keywords: Qom Formation, microfacies, sedimentary environment, diagenetic processes, Central Iran
  • Ensieh Behdani, Ensieh Behdani*, Marziyeh Notghi Moghaddam, Ahmadreza Khazaei Pages 23-34
    Introduction

    The studied section is located in the eastern part of the Lut block (Iran). Lut Block represents an important structural unit of the Central and Eastern Iran. The block extends for about 900 Km in the north-south direction. It is separated from the Flysch Zone of eastern Iran by the Nehbandan fault in the east, whereas the western boundary with Central Iran is the Nayband fault and Shotori Mountains. Stocklin in 1968 believes that the Lut block could be divided into two parts (eastern and western). Camel mountain range (Shotori Mountain range) is regarded as the boundary between two parts. Based on petrological properties, it is shown that the mentioned parts are completely different from each other. In addition, various seismotectonic movements were seen in two parts that make the difference between the two parts. Dasht-e-Lut includes volcanic rocks of the Tertiary system with approximately 2000 m thickness. The volcanic rocks cover more than half of the Lut block.

    Materials and methods 

    Seventy-two samples for the study of the calcareous nannofossils were collected from the argillaceous limestone, pale- green marl at several different stratigraphic positions. Calcareous nannofossils were prepared in 72 smear slides using the standard techniques described by Bown and Young (1998), and studied under an Olympus Bx50 light microscope in parallel light and crossed Nicols with a magnification of 100x. Digital images of nannofossil specimens were taken with a Sony digital camera. All calcareous nannofossil specimens were identified by the taxonomic schemes of Perch-Nielsen, (1985) and Bown & Young (1998). The biostratigraphic data were interpreted by the nannofossil zonation of Sissing (1977), commonly used for the lower and upper Cretaceous in the Tethyan area.

    Results and Discussion

    In the studied samples, 55 species were identified. In most slides, the most common components of the nannofossil assemblages are the Watznaueria, Nannoconus, Conusphaera and Cyclagelosphaera genera. In the studied interval, the CC1 – CC5 calcareous nannofossil zones of Sissingh (1977) were recognized in the Deheshk section in eastern Iran. These biozones cover the Early Berriasian to Early Barremian in this section. The appearance of species like, N. colomii, N. dolomiticus, N. globulus, N. steinmannii minor and N. steinmannii steinmannii with Lithraphidites carniolensis, Polycostella senaria and Polycostella beckmannii at the base of this section was remarked and corresponded to the CC1 Calcareous Nannofossil Zone (Sissingh, 1977). The proposed biozones are arranged from the base to the top and they are Nannoconus steinmannii Zone (CC1), Stradneria crenulata Zone (CC2), Calcicalathina oblongata Zone (CC3), Cretarhabdus loriei Zone (CC4) and Lithraphidites bollii zone (CC5). Biostratigraphically, nannofossil assemblages suggest that the studied succession belongs to the CC1 Zone to CC5 Zone of Sissingh (1977) biozonation from the Tethyan province. According to this study and on the bases of calcareous nannofossils, the age of Baghmeshah Formation in the Deheshk section is Early Berriasian to Early Barremian.

    Conclusion

    In this study, 55 species belong to 26 genera of calcareous nannofossils were identified. Based on the present species and their comparison to the Tethyan calcareous nannofossils, the age of the Early Berriasian to Early Barremian is suggested for the studied succession that equivalent to CC1 - CC5 Zones of Sissingh (1977) biozonation.

  • Mehdi Reaz Poursoltani*, Nastaran Kazemi Zanjani Lotfabadi, Mohammad Ebrahim Fazel Valipour Pages 35-53
    Introduction

    Kardeh catchment is a part of the Kopet-Dagh zone and contains a variety of lithological composition. Mozduran and Shurijeh formations, Neogene and recent deposits form most of the outcrops in this area (Nabavieh, 1998). In this study, considering the importance of Kardeh catchment area as sources of water for the underground and surface water resources for drinking in the west of Mashhad, we have analyzed water samples from each sub-catchment and conducted chemical analysis of rocks. The impact of harmful elements in the river water, resulted from lithological erosion, in this basin are discussed. In addition, the water quality of the river in terms of agricultural use, drinking, and industry usage is also investigated (Li & Zhang, 2008; Han et al, 2010).

    Materials and Methods

    In this study, 17 water samples and 9 rock samples were collected for analysis. For this reason, temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), concentration and absorption of some ions have been measured. Based on the results, in order to determine water quality for drinking, agriculture and industrial usage, we have made comparisons with the World Health Organization drinking water standards and data from the Standards and Industrial Research Institute of Iran (Schuler, Wilcox and Piper diagrams). Rock samples have been analyzed by ICP method. Two polished thin sections were studied to determine the composition of mineral components, using the Scanning Electron Microscope (SEM) equipped with EDS.

    Discussion

    Based on the analysis carried out in the Kardeh catchment, the maximum TDS is 863.35 mg/l in the Al area, and the minimum is 571.95 mg/l in Karim-Abad. The maximum electrical conductivity (EC) is 557 microzimens/sec in the Al area, and the minimum EC is 369 microzimens/sec in Karim-Abad. The highest temperature of 24.6°C is related to the lake, and the minimum temperature measured is 10.3°C in the Mareshk area. The results indicate that among cations, magnesium and potassium have the lowest concentration, whereas sodium and calcium have the highest. Among anions, bicarbonate has the maximum concentration, and sulfate the minimum. Petrographic studies indicate that carbonate and sandstone are the main types of rocks in the study area. Carbonate facies are mainly dolomite, whereas sandstone facies are sublitharenite and feldspathic litharenite with silica, carbonate and iron oxide cements. Based on ICP analysis, aluminum, calcium, iron, potassium, magnesium, and sodium are the main elements in the rock samples. Mozduran (carbonate strata) and Shurijeh (siliciclastic strata) formations and also evaporative units are the probable sources of water-soluble ions (Kazemi et al., 1395). Based on the results of the analysis of water samples, the water is not suitable for industrial usage due to corrosion and precipitation of chemicals. Also, according to the Schuler diagram, some water samples are not suitable for drinking. On the other hand, according to the Piper diagram (Piper, 1944), the major water samples have good quality and contain sulfate, chloride, and calcium as main ions. Thus, according to the Wilcox diagram (Wilcox 1995), the major water samples are in class C2S1. So, based on the presence of slight salt in the water, therefore it is suitable for agricultural use.

    Conclusion

    The main ions in the Kardeh water samples are sodium, calcium, magnesium, iron, sulfate, and carbonate. Based on the analytical results, for drinking all samples are moderate to good, and are classified in class C2S1 of the Wilcox diagram. Although these samples are acceptable for agriculture, they are unacceptable for industrial usage. Finally, based on the Piper diagram, the quality of water samples are in sulfate and chloride groups. In the Kardeh catchment, the probable source of ions in water samples could be carbonate and siliciclastic rocks as well as Neogene and recent deposits.

    Keywords: Kardeh catchment, Khorasan Razavi, lithology, water quality
  • Mohammad Ali Jazi, Mohamad Hassan Karimpour*, Ferdowsi University of Mashhad Pages 53-74
    Introduction

    Nakhlak Pb-(Ag) deposit, one of the oldest and largest Iranian lead deposits, is located at the Nakhlak Mountain about 55 km NE of Anarak, a town in Isfahan Province, Iran. Lead ores are mainly hosted by open space of fractures and normal faults in the Upper Cretaceous carbonate (Sadr unit). The style of mineralization is stratabound and epigenetic, as shown by steeply east-west veins. Ore deposition in the Nakhlak deposit was controlled by three main factors: 1) lithology, 2) stratigraphy, and 3) structure. These can be viewed as fundamental controls of fluid transmissivity, either at the district or mine scale, that allowed the focusing of fluid flow and created opportunities for depositional processes to occur (Leach et al., 2005).

    Materials and methods 

    The Nakhlak Pb-(Ag) deposit is situated in the northwest corner of the Central Iran Structural Zone, which contains the Anarak region. The Nakhlak deposit is on the eastern fringe of Nakhlak Mountain. This mountain consists of pre-Triassic? ophiolites (Holzer and Ghasemipour, 1973; Alavi et al., 1997) and a Triassic sedimentary succession (Nakhlak Group, which comprises the Alam, Baqoroq, and Ashin formations), Upper Cretaceous (Sadr unit), and Paleocene (Khaaled unit) sedimentary cover. The Upper Cretaceous carbonate rocks (Cenomanian to Campanian), crop out across a large area of Nakhlak and reach a thickness of 258 m (Khosrow-Tehrani, 1977; Vaziri et al., 2005; Vaziri et al., 2012). The Sadr unit consists of conglomerates, sandy limestones, calcareous sandstones, sandy dolostones, sandy-argillaceous limestones, sandy dolomitic limestones, and reefal limestones that have been subdivided into five subunits based on their facies characteristics (Rasa, 1987). The Sadr unit rocks exposed on Nakhlak Mountain represent marginal-marine, shallow-shelf, and moderately deep marine environments (Vaziri et al., 2012).

    Discussion and Conclusion

    The Sadr unit displays suitable characteristics for mineralization such as the presence of reef and dolostone facies and limestone to dolostone transition. The alteration of wall rock in the Nakhlak deposit is represented by the dissolution of carbonate and hydrothermal carbonates deposition that widespread close to ore-body and occurred from pre to syn- mineralization. There are three types of dolomite concerning mineralization, which saddle dolomite is the most important type of them. MgO, Fe2O3(Fe total), MnO as well as Pb, Ba, and Zn are enriched in altered wall rock and contrast with CaO is depleted. The positive relationship observed between the intensity of the dolomitization process, concentration of ore- metals, and sulfide mineralization in carbonate host rocks; suggesting that the migration of metal-bearing fluids was linked to hydrothermal processes. The estimate of hydrothermal fluid nature of the Nakhlak Pb-(Ag) deposits hydrothermal dolomite indicate a basinal brines (average 14.11 wt% NaCl eq.) and low temperatures (average 174 C), relatively equivalent with ore-forming fluid. In the Nakhlak deposit, interaction of carbonate host rock with the ore-forming fluid of mineralization process performed by feedback mechanisms. The suitable carbonate host rock (chemically and physically) is main factor entering of hydrothermal fluid into the host rocks and mineralization causing the dissolution of carbonate host rocks and increased formation of hydrothermal dolomite in the host rock, and consequently, that dissolution and dolomitization increased permeability of the host rock for ore fluids and allowed the deposition of additional ore minerals.

    Keywords: Dolomite, petrography, geochemistry, fluid inclusion, basinal brine, Nakhlak
  • Ali Rajabzadeh, Hossein kouhestani, Mir Ali Asghar Mokhtari, Afshin Zohdi* Pages 75-90
    Introduction

    The Upper Red Formation (URF), with the age of Miocene, is mainly composed of clastic sediment including interbedded marl, sandstones and slightly conglomerate layers as well as some evaporate layers mostly in lower parts of the formation. The lithology, color and thickness of this formation are variable in a different locality (Aghanabati, 2004). This formation is the only cap rock for the Qum Formation in the Central Iran zone especially into the Sarajeh and Alborz gas-fields (e.g., Morley et al., 2008). The URF has significant distribution in the northwestern of Iran and hosts significant Cu and Pb-Zn deposits (e.g.; Sadati et al., 2016). The constituents of this formation, particularly in the sandstone layers, provide valuable information in relation to the sedimentary environment and the geodynamic location of this formation (Rieser et al., 2005). In this research, based on the facies analysis (Miall, 1996, 2000), modal analysis and geochemical data, sedimentary environment and tectonic setting of these clastic layers in the Chehrabad deposit section, northwest of Zanjan, are interpreted.

    Materials and methods

    This research is based on a detailed study of lithology, sedimentology and geochemical data of the URF. During field observations, the thickness of sandstone layers and their colors were clearly defined. In order to interpret the sedimentary environments of this formation, a detailed lithofacies have been analyzed during this study. Lateral and vertical variations in all layers have been considered. About 23 thin sections from collected samples are studied by polarizing microscope at the University of Zanjan. In each thin section, the 250-points, based on the Gazzi-Dickinson method, were counted. To investigate the tectonic setting of these sandstones, 9 samples with the least amount of weathering and calcium carbonate were selected for geochemical analyses by XRF methods.

    Discussion

    Chehrabad area is located in the northeast of Mahneshan, approximately 75 km, northwest of Zanjan. Rock units exposed in this area belong to the Lower Red, Qom and Upper Red formations. The thickness of the URF in this area is about 980 m and consists mainly of three main units. These units, from bottom to top, consist of evaporate layers, alternation of mudstone and grey to red sandstone and finally mudstone with interbedded gypsum layers with a thickness of 235, 590, and 155 m respectively. The studied sequence is a part of the middle portion of the URF, with 231 m thickness and has the highest amounts of sandstone layers. Based on the field observation, the middle parts of the formation including 7 gray to red color sandstone, which is alternate with the red mudstones. The sandstones in the Chehrabad area are grey to red and have poor imbrication. According to the sorting and roundness parameters of the grains and also the low amounts of clay matrix (less than 5%), these sandstones are perhaps to be mature in terms of texture maturity. Based on the types of sandstone grains and the Folk (1980) classification, the URF sandstones in the study area is classified as feldspathic litharenite to litharenite. Facies analyses, the color of layers, presence of cross-bedding and plant fragments, lack of gravel grains, all represent an oxidized continental environment, such as a fluvial system with a highly sinuous channel (meandering river). Also, the presence of symmetric ripple marks and marine trace fossils indicate that the sedimentation of some parts of this formation has taken place to a tidal condition and most likely close to the coastal environment. In addition, based on field studies and facies analysis, identified lithofacies in Chehrabad area include Fl, Sm, Sh, Sr, Sp, St and Fm. According to the characteristics of each facies and based on the method of Miall (1996), these sandstones were deposited in fluvial and tidal depositional systems. The results of petrography and geochemical studies have been used to interpret the tectonic setting of sandstones in the middle parts of the URF. Based on triangular diagrams of Dickinson and Suczek (1979) (Qt-F-L) and Ingersoll and Suczek (1979) (Qp-Lvm-Lsm and Lv-Lm-Ls), also using binary variables graphs of Bhatia (1983) and Roser and Korsch (1986), the tectonic setting of these sandstones is active continental margins and probably foreland basin.

    Conclusion

    The URF in the Chehrabad area consists of 3 parts and the thickness of the middle part of this formation is about 231 m, with 7 sandstone layers, which alternation with red mudstone beds. Based on microscopic studies, these sandstones are classified as feldspathic litharenite to litharenite. Based on field evidence and the presence of cross-bedding, plant fragments, lack of gravel grains, symmetric ripple marks, presence of trace fossils and also the type of facies, seven lithofacies (including Fl, Sm, Sh, Sr, Sp, St, and Fm) are recognized. The data obtained from point-count and geochemical studies clearly show that the tectonic setting of these sandstones in the Chehrabad area is an active continental margin.

    Keywords: Sedimentary facies, tectonic setting, sandstone, Upper Red Formation, Chehrabad, Zanjan
  • Behzad Saeedi Razavi*, Fatemeh Asgari, Mohammad Reza Kamali, Ezatallah Kazemzadeh Pages 91-108
    Introduction

    Sarvak Formation is one of the units in the Bangestan lithostratigraphic group with Albian-Turonian age. The shallow sea at the end of the Albian to Cenomanian time has deposited large amounts of the shallow marine carbonates (Sarvak Formation) over a large area of the Zagros basin (Motiei, 1995). The Sarvak Formation has two different facies. At the type section and coastal Fars, shallow marine facies of this formation mostly formed while in the Lorestan area, the facies are belonging to deeper water (Motiei, 1995). The Sarvak Formation is a reservoir of hydrocarbon in the Zagros sedimentary basin. Therefore, a detailed study of this formation, based on microfacies and sequence stratigraphy, will provide useful and valuable information for further exploration in this basin. The purpose of this study was to evaluate the biostratigraphy, microfacies, depositional environment and sequence stratigraphy of the Sarvak Formation.

    Methods and Results 

    To approach the objectives of this research, two stages have been taken: Preparation of 195 thin sections from drill cores and cuttings (National South Oil Company), then Laboratory studies of thin sections prepared by binocular microscopy and identification of allochems and orthochems and the preparation of photomicrographs. The identified biozones correspond to biozones named after Wynd (1965). In this study, Flugel (2010) method used to describe the microfacies, and also Reading (1996) and Dunham (1962) methods used to determine rock texture and nomenclature Identification, photography and the creation of the Atlas of microfossils, their distribution in stratigraphic column, representation of identified biozones, and sedimentary sequence lithology in the studied area has been made possible through the study of graphs and logs, thin sections, and the use of various research satellites such as Bolli (1945; 1959; 1966), Postuma (1971) and Caron (1983). Sequence stratigraphy of the Sarvak Formation has been studied based on sequence stratigraphic methods and principles (Haq et al., 1987; Van Wagoner et al., 1988; Emery and Myers, 1996; Simmons et al., 2007).

    Results and Conclusion

    Based on this study, 5 genus and 2 species of pelagic microfossils and 25 genus and 28 species of benthic microfossils were identified. Therefore, three biozones including Nezzazata - alveolinids assemblage zone # 25, Rudist debris zone # 24, and Oligosteginid flood zone # 26 were introduced that are corresponding to the biozones introduced by Wynd (1965). Based on the studied faunal assemblage, the age of the Sarvak Formation is from Cenomanian to Turonian in the studied wells. The upper boundary of the Sarvak Formation with the Gurpi Formation is discontinuous due to the presence of glauconitic nodules at the base of the Gurpi. According to the regional geology of this area and information from the studied wells, the Ilam Formation and the 30th Wynd Biological Zone (Wynd, 1965), as well as the biodegradation of Wynd (1965) at the top of the Sarvak Formation, are absent. The drilling has not reached the base of the Sarvak Formation, therefore the lower boundary is not clear. 7 microfacies identified in the Sarvak Formation in the studied wells. These microfacies are formed in 3 main facies belts including 1- open sea, 2- shoal, and 3- lagoon. Investigation of carbonate rocks of the Sarvak Formation in the study area shows that the sedimentary environment of the Sarvak Formation in the studied field was a shallow carbonate platform of the carbonate ram type. The Sarvak Formation in the study area consists of 1 complete sedimentary sequence and 2 incomplete sequences, which are generally HST and TST in the studied sections. The HST facies in this sequence originate from a variety of marine microfacies and finished with the lagoon. The TST facies is mainly related to the open marine. Finally, the HST facies is related to the inner and middle parts of the platform; while the TST facies is related to the outer and middle parts of the platform.

    Keywords: Biostratigraphy, microfacies, sequence stratigraphy, Sarvak Formation, Cenomanian Turonian
  • Bahareh Shakeri*, Hossein Vaziri, Ali Bahrami, Mohammad Ali Salehi Pages 109-132
    Introduction 

    During the Silurian and Devonian time, some parts of Iran, including Central Iran, Alborz and Sanandaj-Sirjan basins, along with the Turkey and Afghanistan plates had been connected to the Arabian and African plates; located on the northwestern margin of the Gondwana and southern Paleotethys (Berberian and King, 1981; Husseini, 1991; Sharland et al., 2001; Ruban et al., 2007; Al-Juboury and AL-Hadidy, 2009). The Devonian deposits represent a considerable distribution in Tabas Block and Central Iran. During the Devonian time, the Iranian platform was located in the southern hemisphere, near 30° latitudes. Outcrops of the Upper Paleozoic around Isfahan region mostly limited to the northern Isfahan (Soh and Natanz districts, Najhaf, Neqeleh, Varcamar, North Tar, east Kesheh sections; Bahrami et al., 2015), Northeast of Isfahan (Zefreh, Chahriseh, and Dizlu sections; Königshof et al., 2016) and south of Isfahan (Shahreza–Ramsheh area; Bahram et al., 2014). In order to investigate the microfacies and sedimentary environment of Bahram Formation in southeastern Anarak, Kuh-e-Bande- Abdol-Hossein section was selected and studied. Kuh-e-Bande-Abdol-Hossein section is located about 32 km southeastern Anarak and northeastern Isfahan in E: 53° 52' 55" and N: 33° 10' 90 " coordinates. The Anarak route toward Khur is the way to the section; after two kilometers, through a 25 km long unpaved road the study section could be accessed.

    Materials and Methods

    In order to study the sedimentary environment and identify the sedimentation process during the Middle and Upper Devonian Kuh-band-e-Abdolhossein section in Anarak region, 230 thin sections and a few polished slabs were prepared and process with laboratory techniques to study and identify the skeletal and non-skeletal components, texture and other microscopic characteristics. Microfacies textures were identified according to Dunham (1962), Embry and Klovan, 1971 schemes, and also the further standard models of Wilson (1975) and Flugel (2010) have been used. In order to distinguish calcite mineral from dolomite, all samples were stained by Alizarin red S solution (Dickson, 1965).

    Discussion

    The Bahram Formation in this section is 366 m thick and lithologically is composed of thin to thick-bedded limestone, an alternation of limestone and thin-bedded shale, sandy limestone and marly limestone. Based on facies changes and petrological properties, 16 microfacies were identified in this section. Investigation of the identified facies indicates the deposition of these microfacies has taken place in a carbonate ramp during the Middle and Late Devonian time in the study section in Anarak region. On the basis of vertical and lateral microfacies variations and their comparison with the sea level changes’ curve, sequence stratigraphic studies of the Bahram Formation led to the identification of seven fourth-order sequences in the study section. According to the obtained data, the first and the seventh sedimentary sequences are as parts of complete sedimentary sequences, while second to sixth sedimentary sequences are complete sequences including transgressive system tracts, high stand system tracts and maximum flooding surface as well as sequence boundaries.

    Conclusion

    The Bahram Formation in the Kuh-e-Bande-Abdol-Hossein section, SE Anarak with a thickness of 366 m is composed of thin to thick-bedded limestone, an alternation of limestone and thin-bedded shale, sandy limestone, and marl limestone. Microfacies analysis has led to the recognition of 16 microfacies and their lateral and vertical distribution show that carbonates were deposited on a ramp type carbonate platform. Storm deposit or very slight steepened slope resulted in the deposition of very rare redeposited fine-grained bioclasts in the deeper part of the platform. According to the sequence, stratigraphy analysis seventh fourth-order depositional sequences are recognized in the Bahram Formation. Microfacies analysis indicates that this section shows rather deeper paleoenvironments in comparison to the previously studied sections of the Bahram Formation in Central Iran.

    Keywords: Bahram Formation, microfacies, sedimentary environment, sequence stratigraphy, Upper Givetian-Upper Famennian, Kuh-e-Bande-Abdol-Hossein
  • Mohsen Allameh* Pages 133-145
    Introduction 

    The Sanganeh Formation is one of the Early Cretaceous formations which is deposited in the Kopet-Dagh sedimentary basin. It is investigated from palynofacies and palaeoecological points of view in the Amir Abad stratigraphic section. This formation has a thickness of 530 m and is mainly composed of dark grey shales. It contains septarian nodules as well as cone-in-cone structures with ammonite in some horizons. The Sanganeh Formation overlaid the Sarcheshmeh Formation and is distinguished by a limestone rich-in fossil and is gradually underlain by the Aitamir Formation. Sanganeh Formation in the Amirabad section is located at 36o34‘ northern latitude and 60o 5’ eastern longitude 852 meters above sea level, in Amirabad village along Mashhad Kalat road.

    Discussion

    50 samples were systematically collected from the Sanganeh Formation. The traverse method (Traverse 1998) was used to produce Palynological slides. About 40 grams of each sample was cleaved and washed carefully and kept in 20% concentration HCL for 24 hours and afterward 24 hours in 40% concentration HF. Furthermore, samples were boiled in 20 concentration HCL for 20 minutes and sieved using 20-micron nylon sieve. Moreover, in order to separate palynomorphs from heavier materials, samples were centrifuged with a zinc chloride solution between 1.9 to 2 densities. Fensome and Williams (2004), Fensome et al., (2008), Slimani et al. (2008, 2010, 2011), were used for categorizing and identification of dinoflagellates species. The following species are the most important dinoflagellates that were identified from analysis of Palynological slides from Sanganeh Formation: Achomosphaera neptuni- Astrocysta sp.- Batiacasphaera sp.- Cerbia tabulate- Cleistosphaeridium sp.- Cribroperidinium sp.- Cribroperidinium orthoceras- Cymososphaeridium sp.- Coronifera oceanica- Diconodinium sp.- Endoscrinium campanula- Eucladinium sp.- Fromea amphora- Gardodinium trabeculosum- Hystrichosphaeridium sp.- Kiokansium polypes- Odontochitina sp.- Odontochitina operculata- Oligosphaeridium albertense- Oligosphaeridium cf. fenestratum- Oligosphaeridium complex- Oligosphaeridium pulcherrimum- Oligosphaeridium sp.- Pseudoceratium polymorphum- Pseudoceratium retusum- Spiniferites sp.- Spiniferites ramosus. From the identified fossils and different Palynological elements, three species of palynofacies were identified: 1) Highly proximal shelf or basin, 2) Marginal dysoxic - anoxic basin, 3) Proximal suboxic-anoxic shelf. A good interpretation of the environments can be obtained, using the data from Palynological Facies and the study of some conservation factors of organic materials. These results are obtained from the combination of quantitative and qualitative criteria. Most important factors are listed below: Fraction of transparent AOM to opaque AOM: This factor demonstrates the less oxygen or low oxygen (in very few slides) conditions during sedimentation. Lability factor: The Lability factor for the Sanganeh Formation samples shows low levels of Lability factor, due to lack of existence or low existence of brown palynomacerals trace in these samples. This indicates that deposition has taken place far from shore, far from the source, and extremely in the low oxygen conditions. Transparent AOM to a fraction of marine palynomorphs fraction and opaque AOM to marine palynomorphs fraction: Increases from AOMt to MPs is an indicator of low oxygen or oxygen-free conditions and slow sedimentation rate, also decreases from AOMop to MPs is an indicator of low oxygen conditions during sedimentation in Sanganeh Formation. Opaque same dimension Palynomaceralto Spiky Palynomaceral fraction: In general, a high fraction of PM4R to PM4B is an indicator of sedimentation in deeper parts of the basin. Corate to proximate Dinoflagellate fraction, proximocorate to cavate (C/PPC): High occurrence of proximate, caveat, and proximocorate Dinoflagellate is an indicator of shallow sedimentation in this Stratigraphy Section. (Vajda 2003; Ghasemi-Nejad et al., 1999).

    Conclusion

    From the study of identified Palynological slides from the Sanganeh Formation, Three kinds of Palynofacies were recognized and dominant environmental conditions were the quasi airborne and low energy during deposition of this formation. Also, it has shown that the basin of Sanganeh Formation was varied from inner Neritic to outer Neritic and shows that low oxygen or oxygen-free conditions occurred during sedimentation.

    Keywords: Palynomorph, Palynofacies, Kopet Dagh, Sanganeh Formation, Amir Abad