Stratigraphy and geochemistry of Jurassic formations in selected sections-North Iraq

Other Title(s)

طباقية و جيوكيميائية تكوينات الجوراسي في مقاطع مختارة-شمال العراق

Dissertant

al-Badri, Abid Mahdi Salih

Thesis advisor

al-Rawi, Dhia Y.

Comitee Members

al-Shahwan, Muwaffaq F.
Tammar Agha, Mazin Y.
Nasir, Madhit A.
Ali, Abd Allah A.
al-Dabbas, Mutazz Abd al-Sattar Muhammad

University

University of Baghdad

Faculty

College of Science

Department

Geology Department

University Country

Iraq

Degree

Ph.D.

Degree Date

2012

English Abstract

Two Jurassic sections have been studied within Duhok Governorate, in Kurdistan north of Iraq, in terms of lithostratigraphy, microfacies, diagenesis, mineralogy, trace elements, stable isotopes, and petroleum potential.

The study covered six formations, which are: Sarki, Sehkaniyan, Sargelu, Naokelekan, Barsarin, and Chia Gara.

The lithological study shows that three formations are mainly carbonates (dolomite and limestone), namely: Sarki, Sehkaniyan, and Barsarin.

The other three Formations: Sargelu, Naokelekan, and Chia Gara are mainly formed of organic carbonaceous calcareous mudrocks with some carbonates.

The dolomite mineral forms most of Sarki, Sehkaniyan, and parts of Sargelu and Barsarin Formations in section-II (Banik).

The calcite forms most of Sargelu, Naokelekan, Barsarin and Chia Gara Formations.

The lithologies, microfacies analysis, and geochemical data identified the depositional environments for each Formation as deep open marine for Sargelu and Chia Gara formations, shallow restricted marine for Sarki Formation, salty swamps or marshes, tidal flats, and hypersaline restricted lagoons for Naokelekan Formation, whilethe shallow open and restricted marine are the depositional settings for Sehkaniyan and Barsarin formations.

The oxygen stable isotopes (18O) data are used for the determination of paleoclimate changes and related sea-level fluctuations.

The peaks of the negative (δ 18O) values indicate warm climate during Sarki time, and more warming during Sehkaniyan time.

The stability of negative value of (δ 18O) through Middle – Upper Jurassic indicates the continuity of the warm climate.

There are no clear changes in (δ 18O) values in Jurassic youngest formations.

The carbon (13C) isotope is used for sea-level fluctuations diagnostics.

The peaks of positive (δ 13C) values indicate fall/rise turnaround points (or lowstand sealevel) as at the boundary between Baluti and Sarki formations.

On the contrary, the negative peak values indicate rise/fall inversion points which indicate flooding surfaces as at the boundaries of Sarki / Sehkaniyan and Sehkaniyan / Sargelu formations.

The results of element analysis for Mg ratio shows close correlation between Mg contents and the presence of early diagenesis processes (dolomitization & dedolomitization), where its ratio increases in dolomitized zones in both sections.

The Fe and Mn contents increases in deep open marine conditions (the depositional settings of Sargelu and Chia Gara formations), but the highest values for Fe and Mn are found in the depositional environments are more closed to positive continental lands, the main source for Fe and Mn, (as in Naokelekan Formation).

The palaeosalinity is estimated from strontium values (Sr).

The Sr proportions in marine environments are influence by degree of salinity, and the impact of early diagenesis processes (dolomitization) as in dolomitized parts of Sargelu Formation of Banik section.

In general, the Sr shows increase in its values in deep open marine environments as in Sargelu and Chia Gara formations, and hypersaline restricted lagoons, tidal flats, and salty stagnant swamps conditions as in Naokelekan Formation.

Low Sr ratios are found in Sarki, Sehkaniyan, and Barsarin formations indicated marine conditions with low salinity relative to depositional environments of other mentioned formations.

In order to determine the petroleum potential for the studied formations, the total organic carbon (TOC) computed and Rock- Eval pyrolysis have been done for (100) samples.

The results show the following: - Sargelu and Naokelekan Formations can be classified as excellent, while the Chia Gara formation classified as very good in term of hydrocarbon generations and petroleum potentiality.

- Sarki, Sehkaniyan, and Barsarin formations are classified as poor in their hydrocarbon generations and petroleum potentiality.

- The organic matters are thermally mature and located within the oil zone in Sehkaniyan, Sargelu, Naokelekan, Barsarin, and Chia Gara formations, but it is overmature and within gas zone in Sarki Formation.

- The kerogen type-II and type-III are found in Sarki, Sehkaniyan, and Barsarin formations.

- The kerogen type-II are founds in Sargelu, Naokelekan, and Chia Gara formations, with some kerogen type-I.

- The migrated hydrocarbons are not observed in studied formations.

Main Subjects

Earth Sciences, Water and Environment

Topics

• Iraq
• Dihok
• Kurdistan
• Sediments
• Marine sediments

No. of Pages

162

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-608639