زیست چینه نگاری ، ریز رخساره ها و دیرینه بوم شناسی سازند آسماری در برش مخملکوه، ناحیه لرستان، باختر ایران

نویسندگان

1 دانشجوی دکترا چینه‌شناسی و فسیل‌شناسی، دانشگاه آزاد واحد علوم و تحقیقات، تهران

2 دانشیار گروه مهندسی معدن، دانشگاه بین‌المللی امام خمینی (ره)، قزوین

3 دانشیار گروه زمین‌شناسی، دانشگاه پیام‌نور، تهران

4 استادیار سازمان زمین‌شناسی و اکشافات معدنی کشور، دفتر نظارت و ارزیابی، تهران

چکیده

سازند آسماری توالی ضخیم کربناته­ای در حوضه فورلند زاگرس است که در زمان الیگومیوسن نهشته شده است. به منظور انجام مطالعات زیست­چینه­نگاری، ریزرخساره­ها و تفسیر محیط­رسوبی، برش مخملکوه از پهنه لرستان واقع در باختر زاگرس مورد بررسی قرار گرفت. برش مخملکوه دارای 85 متر ضخامت است که از تناوبی از سنگ­آهک­های ضخیم لایه با میان لایه­هایی از سنگ­آهک نازک­لایه تشکیل شده است. بر اساس مطالعات زیست­چینه­نگاری­، 12 جنس وابسته به 7 خانواده از روزنبران کف­زی و پلانکتونیک در برش مورد مطالعه شناسایی شد. در این برش، دو تجمع فسیلی و 12 ریزرخساره بر اساس الگوهای پراکندگی روزن­داران با سن روپلین- آکیتانین تشخیص داده شد. تجمعات فونی با زون­های استاندارد جهانی تطابق داده شده است. مطالعه ریزرخساره­ها­ی موجود نشان­دهنده دو کمربند رسوبی شامل لاگون و دریای باز در برش مورد مطالعه است. زیرمحیط­های رسوبی سازند آسماری قابل تطابق با بخش­های رمپ داخلی، میانی و خارجی هستند که تحت شرایط مزوفوتیک، الیگوفوتیک و آفوتیک در یک رمپ هموکلینال نهشته شده­اند. 

کلیدواژه‌ها


عنوان مقاله [English]

Biostratigraphy, Microfacies and palaeoecology of the Asmari Formation in Makhmal Kuh section, Lurestan Province, western Iran

نویسندگان [English]

  • M. Rajabi 1
  • S. Senemari 2
  • M. Parvaneh Nejad Shirazi 3
  • M. Bahrammaneshtehrani 4
چکیده [English]

The Asmari Formation is a thick carbonate sequence in the Zagros Foreland Basin that was deposited during the Oligo–Miocene. In order to conduct biostratigraphic studies, microfacies and to interpret the depositional environment, the Makhmal Kuh section in the Lurestan province located in west of Zagros was investigated. The section is 85 m thick, consisting of alternating layers of thick limestone interbedded with thin-layer limestone. Based on biostratigraphic studies, 12 genera belonging to 7 families of foraminifera were identified in the studied section. In this section, two fossil assemblages and 12 microfacies were identified based on the Rupelian-Aquitanian foraminifera distribution patterns. The fauna assemblages conform to the world standard zones. The study of microfacies indicates two different sedimentary sub-environments including lagoon and open sea in the studied section. These depositional sub­-environments of the Asmari Formation are compatible with the inner, middle and outer ramp parts, formed under a Mesophotic, Oligophotic and Aphotic conditions in a homoclinal ramp.

کلیدواژه‌ها [English]

  • Aquitanian
  • Rupelian
  • Sedimentary environment
  • Zagros
  • Asmari Formation
  • Lurestan
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