مطالعه سنگ‌های رسوبی ائوسن زیرین در ناحیه بیرجند (برش کبوده) و خوسف (برش آرک شمالی)، با تاکید بر آنالیز رخساره‌ها و محیط رسوبی

نوع مقاله : علمی -پژوهشی

نویسنده

دانشگاه پیام نور تهران

چکیده

منطقه مورد مطالعه در حاشیه لوت، در استان خراسان جنوبی قرار دارد. دو برش چینه شناسی کبوده و آرک شمالی به منظور توصیف رخساره ها و تعیین محیط رسوبی مورد اندازه گیری و نمونه برداری قرار گرفت. برای هر برش سه دسته رخساره اصلی کربناته، آواری و مخلوط آواری-کربناته شناسایی گردید. هفت ریز رخساره برای برش کبوده و شش ریز رخساره برای برش آرک شمالی، تشخیص داده شد که از محیط های ساحلی تا ابتدای بخش خارجی پلتفرم کربناته از نوع رمپ گسترده شده اند. رخساره های برش کبوده در زیرمحیط های بار ماسه ای ساحلی، لاگون، ریف های کومه ای مرجانی، جلبکی، نومولیتی و بخش ابتدای سراشیبی قاره و ریز رخساره های برش آرک شمالی در در زیرمحیط های بار ماسه ای ساحلی، لاگون، پشته ماسه ای حمل شده، ریف کومه ای نومولیتی و بخش ابتدای سراشیبی قاره قرار دارند. بر اساس حضور گونه های شاخص فرامینیفرهای بنتیک مانند Nummulites atacicus, Assilina leymeriei و تجمعات فسیلی مانندAlveolina desipiens, Alveolina cf. ellipsoidalis, Opertorbitolites douvillie, Orbitolites minimous, Nummulites globulus, Luckartia haimei برای هر دو برش سن ائوسن زیرین (ایپریزین) پیشنهاد گردید. تاثیر تغییرات جهانی آب و هوایی مرز پالئوسن- ائوسن، در مناطق مورد مطالعه به صورت عدم تشکیل ریف های واقعی و جایگزینی فرامینیفرهای بنتیک بزرگ به جای ریف های مرجانی مشاهده می شود.AbstractThe studied area is located in southern Khorassan province at margin of Lut platform. Kaboudeh and North Ark stratigraphic sections were measured and sampled in order to describe sedimentary facies and determine the depositional environments. Carbonate facies, terrigenous facies and mixed terrigenous-carbonate facies were recognized as three main sedimentary facies sets in both sections. Seven facies types were distinguished for Kabudeh section which are occurred in beach sand bar, lagoon, coral-coralin algal-nummulitic patch reefs and proximal foreslope sub-environments and six facies types were recognized for North Arc section in beach sand bar, lagoon, reworking sand bar, nunmulitic patch reefs and proximal foreslope sub-environmets; ranging from beach to proximal part of outer ramp settings. On the basis of the index species of larger benthic foraminifera such as: Nummulitesatacicus, Assilinaleymereie and foraminiferal assemblages: Alveolinadesipiens, Alveolinacf.ellipsoidalis, Opertorbitolitesdouvillie, Orbitolitesminimous, Nummulitesglobulus, Luckartiahaimei, Early Eocene (Yprisian) is suggested for the studied deposits. Absence of real coral reefs and replacement larger benthic foraminifera are considered as the effects of Paleocene-Eocene boundary global changes in the studied area. keywords: Microfacies, Foraminifera, Sedimentary environment, Early Eocene, Lut, Birjand, Khousf 

کلیدواژه‌ها


عنوان مقاله [English]

Microfacies- Foraminifera- Environment- Early Eocene- Lut

چکیده [English]

The studied area is located in Southern Khorassan province at margin of Lut platform. Kaboudeh and North Ark stratigraphic sections were measured and sampled in order to describe sedimentary facies and determine the depositional environments. Carbonate facies, terrigenous facies and mixed terrigenous-carbonate facies were recognized as three main sedimentary facies sets in both sections. Seven microfacies types were distinguished for Kabudeh section which are occurred in lithoral sand bar, lagoon, coral-coralin algal-nummulitic patch reefs and proximal foreslope sub-environments and Six microfacies types were recognized for North Arc section in lithoral sand bar, lagoon, reworking sand bar, nunmulitic patch reefs and proximal foreslope sub-environmets; ranging from lithoral to proximal part of outer ramp settings. On the basis of the index species larger benthic foraminifera as follows: Nummulites atacicus, Assilina leymereie and foraminiferal assemblages: Alveolina desipiens, Alveolina cf. ellipsoidalis, Opertorbitolites douvillie, Orbitolites minimous, Nummulites globulus, Luckartia haimei, Early Eocene (Yprisian) is suggested for the studied deposits. Absence real coral reefs and replacement larger benthic foraminifera are considered as the effects of Paleocene-Eocene boundary global changes in the studied area

کلیدواژه‌ها [English]

  • Microfacies- Foraminifera- Environment- Early Eocene- Lut
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