Iraqi Bulletin of Geology and Mining

The exposure of the Paleocene sequence (Akashat Formation) in the Rutbah area is distributed in a relatively thin N – S strip extending from north of the Ga'ara depression down to the Iraqi – Saudi Arabian international border, and it is roughly 40 – 50 m thick, truncated east of the Ga'ara depression. The Paleocene sequence, in its exposures north and west of Rutbah area, is phosphatic. The biostratigraphy and depositional environment of the surface exposure of the sequence and that of borehole sections to the west of the exposure areas is studied in some detail in this work. The Paleocene sequence is conformably overlain by the Eocene sequence throughout the exposed and subsurface sections (except in the eastern side of the Ga'ara depression). The underlying sequence belongs to the Late Cretaceous with a hiatus of variable durations. South of Rutbah – Amman highway the break is relatively shorter than that in the Akashat area, especially along the western and northern rims of the Ga'ara depression. In boreholes to the west, the Paleocene sequence increases in thickness, the break with the underlying Late Cretaceous sequence may be negligible or missing. The following planktonic zones are recorded from subsurface and surface sections:
1- Marozovella valasconsis Zone, Late Paleocene (Thanatain)
2- Marozovella angulata Zone, Middle Paleocene (Selandian)
3- Globoconusa daubgergensis Zone, Early Paleocene (Danian)

Calcareous Nannofossils are studied from the Shiranish Formation in Ajeel well No. (10), 30 Km North East of Tikrit City, the study covers the depth interval (1350 – 1500) m, which is investigated to identify calcareous nannofossils species. Based on twenty-five identified calacareous nannofossils belonging to eleven genera, three biozones are identified which reflect outer shelf and basinal environments in the studied section. These are from older to younger: Uniplanarius trifidus Range Zone (CC22) (Part), Tranolithus phacelosus Interval Biozone (CC23) and Reinhardites levis Interval Biozone (CC24) (Part). These biozones are correlated with other calcareous nannofossils biozones from regional view which led to conclude that the age of the studied section is Late Campanian to Early Maastrichtian.

Paleontological study is used to determine Paleocene/ Eocene boundary as principal step to investigate the Paleocene Eocene Thermal Maximum (PETM) characteristics, and to extrapolate the global warming event in three separate sections of Paleogene marine sedimentary rocks in the Sinjar, Dhouk and the Shaqlawa area, in Sinjar, Dohuk and Shaqlawa areas, North and Northeastern Iraq. Shape, size, decline and abundance of the foraminiferal species and generic diversity of photoautotrophic (oligotrophic conditions) in the Aaliji and Kolosh formations respond to the PETM environmental conditions, as well as to the extinction events in deep marine sections with general decrease in larger foraminifera, followed by abundance stage in shallow marine sections. The paleontological and sedimentological, characteristics within the Aaliji and Kolosh formations represent records of PETM- associated events which is obviously distinguished in shallow marine environments exactly at the Dohuk section compared to deep marine environment at the Shaqlawa section.

The Faiha and Sindibad oilfields are located in the northeastern part of the Basrah Governorate, south Iraq. More than 50 thin sections of limestone samples, collected from wells penetrating the Mishrif and Yamama formations in these oilfields, are examined in this work. Several microfacies are identified in the formations studied; four main facies and seven subfacies are found in the Yamama Formation and three main Formation. The main microfacies include lime mudstone, wackestone, packstone and grainstone. They were deposited in various marine sedimentary systems of open marine, foreslope, reef and lagoonal environments. Benthonic foraminifera, Mollusk shells, echinoids, and algae, are the fossils identified in the Mishrif and Yamama formations. Dolomite and calcite are the main minerals in the studied samples. Petrographic examinations revealed that diagenesis varied in intensity from microfacies to another. Dissolution and neomorphism (recrystallization) have created and controlled the development of porosity. The dominant pore types are vuggy, interparticles, intraparticles, channel and moldic. Whereas, cementation, micritization, and compaction processes have had destructive effects, by reducing porosity and permeability that led to reducing reservoir quality. Other processes, such as dolomitization and authigenic minerals (pyrite) do not have strong effects on the reservoir quality. The depositional basin model shows that the Yamama Formation was deposited in the ramp carbonate environment, whereas, the Mishrif Formation was deposited in the rimmed carbonate shelf environment.

The clastic sediments on both sides of the Rawanduz River Valley were investigated for glacial signs. The Rawanduz River, one of the major tributaries of the Greater Zab River, its source area is located in the high ridges of the mountains on the Iraqi – Iranian border. The topography map (1: 25 000) was utilized to determine the best locations for glacial landforms and features. Elevation data was retrieved from the electronic maps of the Maplog. The study was based on field observations, erosional landforms indication and sedimentological analysis, including field visual determination of roundness and sphericity of gravel. The occurrence of glacio-alluvial sediments (tills), terraces more than 10 meters above the present river level, and erosional features of glacial origin indicate that the drainage area of the Rawanduz River, from its source to its conjunction with the Greater Zab River near Bekhma Village, experienced variable rates of glacial activities during the Pleistocene Epoch.

The Zagros Fold and Thrust Belt in Iraq contain host prolific hydrocarbons and recently, significant oil reservoirs have been discovered in the Jurassic carbonate rocks. The current work focuses on Water and Hydrocarbon Saturation in the carbonate rocks of the Sargelu Formation (Middle Jurassic) based on a set of conventional Wireline logs which are: Gamma-ray, Neutron porosity, Bulk Density, three sonic types, all Resistivity, photoelectric, uranium, thorium, and potassium. The Wireline log shows that the Sargelu Formation can be divided into five units based on lithology. These units were derived from different cross plots. The computation of petrophysical properties of this carbonate reservoir is complex due to several washouts and heterogeneities, caused by the exposure of shale which is strongly influencing the reservoir saturation. The Wireline log shows that the average Water saturation in the carbonates of the Sargelu Formation is 20%, with an irreducible Water saturation of 0.2% and an average Hydrocarbon saturation of 30%. Whereas, the water resistivity is 0.03 ohm.m and the Mud filtration resistivity is 0.17 ohm.m.

The Basrah City and surrounding areas are reported to be seriously contaminated by emissions of oil industry and power plants. Magnetic measurements are carried out in this study for ninety surface soil samples from the Shu’aiba area near the Basrah City, southern Iraq. Detailed magnetic concentration parameters are measured to characterize the potentially polluted areas and explore their sources. These parameters include magnetic susceptibility (χ), frequency dependent-susceptibility (κfd%), Anhysteretic Remanent Magnetization (χARM), Saturated Isothermal Remanent Magnetization (IRM) and temperature-dependent susceptibility. The results indicate that the magnetic minerals assemblage in the surface soil is heavily influenced by relatively high concentration of ferro(i)magnetic minerals, such as magnetite. The anhysteretic remanent magnetization (χARM) and Saturated Isothermal Remanent Magnetization (SIRM) are significantly correlated with magnetic susceptibility (R2= 0.94) and (R2= 0.88) respectively, indicating a high contribution of ferro(i)magnetic minerals. This means that the magnetic mineral contents (such as magnetite and hematite) are enriched in the soil samples leading to increase in their magnetic properties which suggest contamination from fly ash produced by burning fossil fuel in the area.