Shiranish formation has been divided into two microfacies units: 1-Marly biowacke stone facies 2-Biogenic pack stone facies These microfacies reflected marine deep shelf margin in the upper part of the formation, the lower part was deeper. 238 slides were investigated depending on Mineralogical, compositional and Biological processes, which reflect deep shelf margin at upper part of the formation, but at the lower part open sea environment. The age of the formation is estimated depending on the recognized biostratigraphic zone using the index fossils to be Upper- Middle Maestrichtian.

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 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

A detailed systematic study of calcareous nannofossils was carried out for the Jaddala Formation in (Aj-10) well, Central Iraq. Seventy one species belong to twenty four genera of calcareous nannofossils were identified including sixty two of them were previously named and nine species were identified for the first time and they would not be given names until more information is obtained in the future to support this identification.
It is a recorded of five biostratigraphic zone, which suggested the age of the Jaddala Formation to be of early to late Eocene. The recorded biozone includes the following: Reticulofenestra dictyoda (Deflandre in Deflandre & Fert, 1954) Stradner & Edwards, 1968 Partial Range Biozone (CNE 5); Discoa

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 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

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

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.

     Yamama Formation is the most important and widespread Lower Cretaceous Formation in Iraq. Yamama Formation in the Luhais well-12 and Rifaee well-1 are composed of dolomitized in some places and foraminifera and algae bearing limestone, 19 genera and species of foraminifera, 10 genera and species of algae. Two biozones were distinguished Pseudochrysalidina arabica Range zone and Pseudocyclammina lituus Range zone. The age of the formation was determined as Berriasian – Valanginian according to these biozones of Foraminifera. In this study, bryozoa, Gastropoda and Pelecypoda are recorded but less than Foraminifera.

Late Paleocene –Early Eocene algae and benthic foraminifera were identified
from the Sinjar Formation that crop out in three selected section from northern
Iraq. The selected sections: (Derbandikhan ,Qara dagh, Wara Mali has been
measured in the field and closely sampled to undertake details. A number of (131)
samples were collected illustrating all the lithological changes along the sections,
The limestone in the studied section is rich in algae and large benthic foraminifera,
The investigation of the thin sections allowed us to identify the (47 ) species of
foraminifera and (34) species of algae , Five biozones were distinguished for algae
which are :a- Amphiroa iraquensis range zone ,b- Trinocladus perplexus