Sedimentology of aqra formation (upper cretaceous)‎ in selected sections in Kurdistan region-Iraq

Other Title(s)

رسوبية تكوين عقرة (الكريتاسي الأعلى)‎ في مقاطع مختارة في أقليم كردستان-العراق

Dissertant

Zibari, Bihruz Ghayyath Abd Allah

Thesis advisor

Tamar Agha, Mazin Yusuf

Comitee Members

al-Qayyim, Basim Abd al-Khaliq
Aghwan, Thamir Abd al-Razzaq
Abid, Ali Ashur

University

Salahaddin University-Hawler

Faculty

College of Science

Department

Geology Department

University Country

Iraq

Degree

Master

Degree Date

2010

English Abstract

This thesis incorporates a study on the sedimentology of Aqra Formation (Upper Cretaceous) in some selected sections in the Iraqi Kurdistan region.

Eight localities were visited, extending from Dohuk area in the west and Bekhme area in the east.

The formation consists mainly of thick and massive bedded limestone and dolomitic limestone.

Both lower and upper contacts of the Aqra Formation are recognizable, the lower contact with the underlying Bekhme Formation is disco formable by the presence of the hard ground between them that seen in the Baker man section, and the upper contact with the overlying Kolosh Formation is unconformable, by the presence of the intraclastic brecciated limestone and dolomitic limestone that is rich in Lotuses spp.

and rudest fragments.

The petrographic constituents of carbonates of the Aqra Formation show the heterogeneous contents in both detailed studied sections (Aqra and Baker man sections).

By using modified Dunham's classification, seven microfiches were recognized and some of them are further subdivided into more than one submicrofacies Using lithologic, paleontological criteria, and standard microfiches analyses and facies zones of the modified Wilson's model, nine facies associations in the Aqra section and five in the Baker man section were recognized.

Both detailed studied sections of the Aqra Formation had shown that, two regressions and one transgression phase happened during the deposition of the formation.

By comparison between the facies belts of the Aqra Formation with the facies belts of the Great Bahaman Bank, it can be seen that many of the facies aspects between them are similar.

In the other word, pale climate of the Aqra Formation was to some extent is similar to the Bahamas, which is humid to semi humid.

During the Maastrichtian time, Aqra Formation was deposited in neritic shallow water environment along the ridge separating two basins, first in the west-northwest trend that Shiranish Formation deposited and second in east-southeast trend that Tanjero Formation deposited.

Thus, we can conclude that, the formation had deposited in isolated platform.

Aqra Formation is thickening toward the Aqra section and thinning away from the same section.

In conclusion, Aqra section is located in the epicenter of the basin in which Aqra Formation deposited and other studied localities are at the margins of the basin.

There are many of the criteria that are found only in the present study and used to differentiate between the Aqra and Bekhme Formations.

These criteria are : presence of Lotuses ssp.

and Actonel sp., absence of Shiranish Formation, and upper contact with the Kolosh Formation Several digenetic processes had affected the Aqra Formation and through three main stages: eogenetic, mesogenetic, and telogenetic.

Main diagenetic processes are : cementation, neomorphism, dissolution, micritization, dolomitization, silicification, compaction, and stylolitization.

The present study shows that, dolomitized parts of the Aqra Formation are formed by the meteoric-marine mixing zone model.

Aqra Formation passed through many of the diagenetic environments such as : meteoric vadose, meteoric phreatic, marine phreatic, mixing, and burial environments.

Main Subjects

Earth Sciences, Water and Environment

Topics

• Iraq
• Kurdistan(Iraq)
• Sediments

No. of Pages

134

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-311195