Document Type : Original Research Paper

Authors

1 PhD Student, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

2 Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

3 Associate Professor, Department of Geology, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

4 Associate Professor, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran

Abstract

Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast and the Neyrizophiolite zone at the southwest in the Neyriz region. They contain about 700 m red and green sandstone, conglomerate and marl which overlay the Jahrum Formation with a disconformity and covered by Bakhtiari conglomerate with an angular unconformity.Petrography of thin sections indicates that the rock fragments are the most constituent, and then quartz and feldspar respectively. The low compositional and textural maturity of the studied samples (angular grains and poorly sorted sandstones) shows the proximity to the source area. Petrography of the rock fragments and the bulk chemical composition of samples display that their provenance is multiple and the sediments were derived from Sanandaj-Sirjan Zone (Cretaceous limestone- metamorphic rocks- Eocene volcanic) and Zagros Zone (ophiolite sequence- radiolarites- Eocene limestone). Also, point-count data plotted on the QFL and QmFLt triangles indicate the recycled orogen and magmatic arc provenance. Based on geochemical data tectonic setting of Neyriz Miocene sediments is continental island arc and active continental margin. The averages of Cullers' index, CIW΄ (for calculation of the chemical weathering), ICV Index (to determine the maturity source), and SiO2versus Al2O3 + K2O + Na2O diagram for these sediments show a poor weathering and dry climatic condition during their deposition which is supported by the high percentage of calcareous cement and frequency of the rock fragments. The results of this study suggest a sedimentlogical framework for the proximal part of Zagros Basin and the Miocene syn-depositional processes.

Keywords

کتابنگاری
اشراقی، ص. ع.، روشن‎روان، ج. و سبزه‎ای، م.، 1378- نقشه یکصدهزارم قطروئیه، تهران: سازمان زمین­شناسی و اکتشافات معدنی کشور.
اشراقی، ص. ع.، روشن‎روان، ج.، علایی مهابادی، س. و سبزه‎ای، م.، 1375- نقشه یکصد هزارم نیریز، تهران: سازمان زمین­شناسی و اکتشافات معدنی کشور.
آفرین، م.، بومری، م.، محبوبی، ا. وگرگیج، م. ن.، 1392- ژئوشیمى گلسنگ‎ها و ماسه‎سنگ‎هاى میوسن پسین- پلئیستوسن گستره ساحلى چابهار: با نگرشى بر سنگ منشأ و جایگاه زمین‌ساختى. فصلنامه زمین‌شناسی ایران، 25، صص. 65 تا 80.
بایت‎گل، آ. و حسینى برزى، م.، 1390- ژئوشیمى عناصر اصلى نهشته­هاى سیلیسى آوارى سازند شیرگشت، بلوک کلمرد، ایران مرکزى براى تعیین برخاستگاه زمین ساختى و هوازدگى سنگ منشأ. فصلنامه علوم زمین، 79، صص. 101 تا 112.
روشن‎روان، ج. و اشراقی، ص. ع.، 1373- نقشه یکصد هزارم چاهک، تهران: سازمان زمین­شناسی و اکتشافات معدنی کشور.
 
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