Microfacies analysis and sequence stratigraphy of Eocene-Miocene succession at Karbala-Najaf-Samawa Area South West Iraq

Other Title(s)

تحليل السحنات المجهرية و طباقية تتابع الايوسين-مايوسين في (كربلاء-النجف-السماوة)‎، جنوب غرب العراق

Dissertant

Shadhar, Diya Khurbat

Thesis advisor

Hassun, Lamis Sadiq

Comitee Members

Ismail, RafahTariq
al-Jumayli, Sad Salih
al-Shaykhali, Sad Sami Jasim

University

University of Baghdad

Faculty

College of Science

Department

Geology Department

University Country

Iraq

Degree

Master

Degree Date

2011

English Abstract

The Eocene – Miocene succession in the southwest desert of Iraq revealed the presence of the Dammam , Euphrates and Nfayil Formations .

Two hundred and thirty nine of thin sections from three boreholes and two outcrops have undergone detailed petrographic identification and used to build both stratigraphic and diagenetic models .

Microfacies characteristics of the whole successions showed the presence of skeletal and non-skeletal grains within the Nfayil and Euphrates Formations.

Only skeletal grains are observed in the Dammam formation .

Details gained from textural and faunal properties helped in the designation of microfacies zones leading to environmental subdivisions for a suggested ramp .For the Nfayil formation : peritidal , shoal , restricted , and deep marine environments .

For the Euphrates formation : restricted , shoal , open marine , and deep marine environments .For the Dammam formation : peritidal , restricted , shoal , and open marine environments.

Generally the diagenetic model of the three sections showed two dolomitization episodes .

The first dolomitized the lower part of the Dammam Formation , by a subtidal model , considering the crystal sizes and the maintenance of the original textures of deposition .

The top of the Dammam Formation probably persisted longer in the mixing zone due to high stand conditions at the end of the Eocene until the second episode of dolomitization .

For the Euphrates and Nfayil Formations .

The absence of dolomite is due to the fast rising sea – level after the Oligocene break ( above basal conglomerate) .

Silicification sometimes accompanied the dolomitization .

Neomorphism in addition to different types of cement , in the Dammam Formation occurred at Karbala and Samawa sections , suggesting an active freshwater zone of diagenesis due to the rising sea level .

For the Euphrates and Nfayil Formations , neomorphism and cement occurred too.

Dedolomitization may be due to the presence of many aquifers known in the Dammam Formation at Najaf and Samawa sections.

6 Five 3rd order cycles were designed for the Dammam succession at Samawa section, minor fluctuations during the four cycle divided it into two 4th order ones .

At Najaf section another cycle was recognized .

At Karbala section , the first two cycles may not be encountered .

Cycles represented episodes of sea-level rises( represented by shallow open marine and deep marine facies) followed still stand represented by shoal facies .

An (SB1) boundary occurs between the Euphrates Formation and the Dammam Formation .

It is a basal conglomerate , with different thicknesses : 0.8 meter at Karbala section , 4.0 meter at Najaf and Samawa sections.

During sea-level rise after the Oligocene , three 3rd order cycles were designed for the three sections .These cycle are different in their symmetry , thickness and stacking pattern from one section to the other .

This may be attributed to local changes in tectonic subsidence which have affected the velocity of relative sea-level rise .

In the current study the Miogypsina sp.(index fossil of the Euphrates Formation) is found above the olive green marl unite of the lower part of the Nfayil Formation

Main Subjects

Earth Sciences, Water and Environment

No. of Pages

98

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-608482