Seventy three species of calcareous nannofossils are recorded from the studied section of Tanjero Formation at Azmer anticline, Sulimaniya, Northern Iraq. The studied section reveals four  biozones arranged in an ascending order  from oldest to youngest as follows; Tranolithus phacelosus Interval Biozone (CC23) Part, Rienhardtites lives Interval  Biozone (CC24), Arkhangelskilla cymbiformis Interval Biozone (CC25), and Nephrolithus frequens Rang Biozone (CC26) Part. These biozones are correlated with other calcareous nannofossil biozones of both local and regional sections, leading to conclude a possible age of  Late Campanian- Maastrichtian.

Seventeen samples of Hartha Formation in Balad (1) well, central Iraq, are studied on the basis of stratigraphic ranges of the recorded calcareous nannofossils for twenty species belonging to twelve genera. The studied section reveals three biozones arranged from oldest to youngest as follows; (1) Calculites ovalis Interval Biozone (CC19), (2) Ceratolithoides aculeus Interval  Biozone (CC20), (3) Quadrum  sissinghii Interval Biozone (CC21). These Biozones are correlated with other calcareous nannofossils biozones from both local and regional sections, leading to conclude the age of the Middle Campanian.

Rerecorded eighteen ostracode species that belong to eleven genera are identified,

    The Paleocene-Eocene Thermal Maximum (PETM) event, which represented a sudden and abnormal rise in temperature during the early Cenozoic Era, is regarded as one of the most important global geologic phenomena. Two important index microfossils (nannoplankton and Ostracoda) were utilised to understand and predict the paleoenvironment and describe the changes during this period. The basis of the study was 12 cutting samples taken from Aaliji and the lower part of Jaddala formations of a subsurface section of (Ba-8) borehole in central Iraq. Some geophysical data were used to determine the upper and lower contacts of the Aaliji Formation and define the shale rate in the studied formations. The micropaleontologic investigation reveals

Shiranish formation has been divided into two microfacies units: 1 - Many biowackestone facies and 2 - maly packstone using planktonic foraminifera and other carbonate components in the rock cutting and core slides. Microfacies reflect marin deep shelf margin in the lower part of the formation, the upper part was deeper. The thickness of the formation is determined, depending on addition to the presence of echinoderm framents debris and spines. This is in disagreement with the 195 ft thickness reported by the Oil Exploration Company The age of the formation is estimated depending on the recognized biostratigraphic zone using the index fossils to be Upper - Middle Mastrichtion.

The Mauddud Formation was one of the important and widespread Lower Cretaceous period formations in Iraq. It has been studied in three wells (EB. 55, EB. 58, and EB. 59) within the East Baghdad Oil Field, Baghdad, central Iraq. 280 thin sections were studied by microscope to determine fauna, the formation composed of limestone and dolomitized limestone in some parts which tends to be marl in some parts, forty species and genus of benthic foraminifera have been identified beside algae and other fossils, three biozones have been identified in the range which is: Orbitolina qatarica range zone (Late Albian), Orbitolina sefini range zone (Late Albian – Early Cenomanian) and Orbitolina concava range zone (Early Cenomanian), The age of

The Quantitative high-resolution planktonic foraminiferal analysis of the subsurface section in three selected wells in the Ajeel Oil Field (Aj-8, Aj-12, and Aj-15) in Tikrit Governorate, Central Iraq has revealed that Shiranish Formation deposited in Late Campanian- Latest Maastrichtian age. This formation consists mainly of marly and marly limestone yielding diverse planktonic foraminiferal assemblages and calcareous benthic foraminifera, with a total of 46 species that belong to 23 genera, Three zones and four subzones, which cover the Late Campanian to the Latest Maastrichtian, were identified based on the recorded planktonic foraminifera and their ranges. They are as follows:1. Globotruncana aegyptiaca Zone that dated to be Lat

The study includes biostratigraphy of the Lower Sarmord Formation in well Kirkuk-No-109. North of Iraq, two biozones had been distinguished as follow:
1- Choffatella decipiens SCHLUMBRGER Zone.
2- Orbitolina discoidea GARS Zone.
The age of Formation in this study is determanid as Lower Cretaceous (Hauterivian-early Aptian).
Keyword: Lower Sarmord, Formation well Kirkuk-109, Choffatella decipiens and Orbitolina discoidea, Lower Cretaceous

   Calcareous nannofossils were documented from the upper part of the Cretaceous Balambo Formation in northern Iraq with the aim of determining an evidence for the Oceanic Anoxic Event. A detailed investigation of the calcareous nannofossils led to the identification of twenty-four species. Regarding these data, Discolithus litterarius (Górka, 1957) was identified at the studied interval with the age of Early Aptian.

   Early Aptian assemblages are dominated by nannoconids that drop sharply within the D. litterarius nannofossil zone, which may be related to the nannoconid crisis recorded in the Early Aptian in the other parts of the world. This event is coincided by a decrease in CaCO_3<

The Yamama Formation was studied in three wells (Fh-1, Fh-2, and Fh-3) within Faihaa oil field, south Iraq. Thin sections were studied by using the polarizing microscope examination in order to determine microfossils and biozone. Thirty-five species of benthic foraminifera were recognized, including four index species. In addition,  twelve species of calcareous green algae were recognized, including  two index species. Other fossils that were recognized in Yamama Formation include Gastropoda, Bryozoa, Coral, Rudist, and Pelecypoda.

Six biozones were observed, which are Charentia cuvillieri sp. (Range Zone of Berriasian age), Psudochryalidina infracretacea

   This study aims to determine the petrophysical characteristics of the three wells in the Kifl Oilfield, central Iraq. The well logs were used to characterize hydrocarbon reservoirs to assess the hydrocarbon prospectivity, designate hydrocarbon and water-bearing zones, and determine the Nahr Umr Formation's petrophysical parameters. The Nahr Umr reservoir mainly consists of sandstone at the bottom and has an upper shale zone containing a small proportion of oil. The geophysical logs data from three oil wells include gamma-ray, resistivity, neutron, density, acoustic, and spontaneous potential logs. A gamma-ray log was employed for lithology differentiation, and a resistivity log was used to determine the response of distinct zones