BIOSTRATIGRAPHIC ANALYSIS OF THE OLIGOCENE-EARLY MIOCENE SUCCESSIONS FROM SULAIMANI AREA, KURDISTAN REGION, IRAQ

Fadhil Lawa

doi:10.46717/igj.53.2d.2ms-2020-10-24

Abstract

Three sections (Darzila, Hazar Kani and Basara) of the Oligocene –Early Miocene successions from Sulaimani area, Kurdistan region-NE Iraq, were measured and studied in order to interpret the biostratigraphic zonations at the Low and High Folded Thrust zones boundary, Low Folded Thrust zone, which are integrated with strontium stratigraphic dating. Accordingly, five biozones have been identified and they are:1- Nummulites vascus- Nummulites intermedius- Nummulites fichteli Assemblage Zone (Shallow Benthic Zone, SBZ 22A) represents the Rupelian age, 2- Lepidocyclina dilatata- Nummulites vascus - Nummulites fichteli Assemblage Zone (SBZ 22B-Early Chattian), 3- Praerhapydionina delicata- Archaias kirkukensis Assemblage Zone (SBZ23) representing the Late Chattian age, 4- Austrotrillina howchini- Peneroplis evolutus Assemblage Zone (SBZ24), almost point to the Aquitanian age and finally 5- Austrotrillina asmariensis- Dendritina rangi Assemblage Zone (equivalent to SBZ25) representing the Burdigalian age. Based on the distribution of the larger foraminifera and strontium stratigraphic dating, the Baba Formation is of Early to Late Oligocene age (Rupelian- Early Chattian), while the Bajawan Formation is of Chattian age, in addition to that, the Anah Formation is of Early Miocene age (Aquitanian) and the Jeribe Formation is of Burdigalian age. It is worthy to mention that the Oligocene-Miocene boundary has been identified in the studied area as well as, the gap duration between different formations of the Kirkuk Group, and the gap durations due to the absences of Serikagni, Euphrates and Dhiban formations.

Highlights

This study clarifies the biostratigraphic framework of the Oligocene and Miocene age rock units represented by the Kirkuk Group and the Jeribe Formation, based on large benthic foraminifera, as well as Strontium (Sr dating) isotope data
The strontium isotope analysis and their corresponding ages point to interval time ranging between 20.37 Ma to 20.80Ma and this represents Aquitanian age, which extends from 23.03Ma to 20.44Ma (Table.3 and Fig. 5).the recognized Anah Formation almost represents the upper part of the proper Anah Formation and corresponds to the - Austrotrillina howchini- Peneroplis evolutus Assemblage Zone (SBZ24), which almost point to the Aquitanian age
The Oligocene (Chattian) and Miocene (Aquitanian) boundary can be placed between them (Bajawan and Anah) with gap interval extending from 23.67 Ma to 20.37 Ma and the gap duration about 3.30 Ma

Summary

Introduction

This study clarifies the biostratigraphic framework of the Oligocene and Miocene age rock units represented by the Kirkuk Group and the Jeribe Formation, based on large benthic foraminifera, as well as Strontium (Sr dating) isotope data. The main aim of this research is to document the biostratigraphic zones, especially from large benthic foraminifera assemblages of the Kirkuk Group, members and the Jeribe Formation relationships, as well as dating them based on Sr isotope results, by measurement of the 87Sr/86Sr ratio, and comparison of the recognized assemblages with coeval assemblages from Iraq and Iran. Another target is the determination of the Oligocene-Miocene boundary and the gap duration between them in the studied area.

Objectives

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Results

Conclusion