Twenty Samples of Shiranish Formation from the well (K-306), Kirkuk area, northern Iraq, are collected and studied on the basis of stratigraphic ranges of the recorded calcareous nannofossils. Eighty-nine species in the studied section reveals five biozones arranged from oldest to youngest as follows: 1.Quadrum trifidum Interval Biozone (CC22) Part 2.Tranolithus phacelosus Interval Biozone (CC23) 3.Rienhardtites lives Interval Biozone (CC24) 4. Arkhangelskilla cymbiformis Interval Biozone (CC25) 5. Nephrolithus frequens Rang Biozone (CC26) PartThese Biozones are correlated with other calcareous nannofossils biozones, from both local and regional sections, leading to conclude the age of Campanian-Maastrichtian.

Eight samples of Shiranish Formation were obtained from Balad well No. 8, (northern Baghdad) central Iraq. Details investigated carried out identify calcareous nannofossils, where identified sixteen species; eleven descried from other region and five left under open name because of lack of material or rare of samples, On the basis of stratigraphic distribution of the species, two biozones proposed these are : 2-Reinhardites levis Interval Biozone(CC24) 1-Tranolithus phacelosus Interval Biozone(CC23b)The proposed biozones correlated with others calcareous nannofossils biozones from regional schemes led to conclusion that the age of Shiranish Formation in studied section Early Maastrichtian.

Fifteen samples from the lower part of Shiranish Formation, Sinjar anticline, northwest Iraq, are investigated in order to identify calcareous nannofossils species of which twelve species are recorded as follow; one species of holococcoliths, seven are heterococcoliths and four are nannolith. On the basis of the above assemblages two biozones are proposed from oldest (at bottom) to youngest (at top):The above biozones are correlated with other calcareous nannofossils biozones from regional view led to conclude that the section is late Campanian in age.

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); Discoaster sublodoensis Bramlette and Sullivan, 1961 Interval biozone (CNE 6-7); Nannotetrina cristata (Martini, 1958) Perch-Nielsen, 1971 Interval biozone (CNE 8); Nannotetrina alata (Martini in Martini & Stradner, 1960) Haq and Lohmann, 1976 Interval biozone (CNE 9); Chiasmolithus gigas Bramlette & Sullivan, 1961Range Biozone (CNE 10-11).

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.

The Kometan Formation is widely distributed in the northern (Kurdistan region) and central Iraq. The studied area is located near the Dokan Dam, about 58 km., to the Northwest of the Sulaymaniyah city, Northeastern Iraq. The Kometan Formation is exposed on the southwest flank of the Sarah anticline. The formation consists of limestone and dolomitic limestone, which have cherts nodules throughout the formation. The Gulneri Formation is recorded below the Kometan Formation with unconformable contact, while at the top is bounded by the Shiranish Formation unconformably too. Three microfacies are identified, these are lime mudstone, planktic foraminiferal lime wackestone-packstone, keeld planktonic foraminiferal lime wackestone-packstone microfacies. All the sedimentary and fossil evidence refer that the sedimentary environment of the formation is the outer shelf to upper bathyal at the lower and upper parts of formation and its extension to the middle bathyal in the middle part of the formation. Based on the stratigraphic ranges of the recorded Calcareous nannofossils biozones, the age of the Kometan Formation at Dokan area is Late Turonian-Early Campanian.

Fifteen samples of limestone, marls and, clay from the Fat'ha Formation are obtained from the location of Bashiqa village, Bashiqa anticline, Northeastern Iraq. A detailed investigation is carried out, during which twenty-four species of calcareous nannofossils identified, twenty- one are descried from other regions while three are left under an open name because of lack of material or insufficient samples. Besides, seventeen species of Ostracoda fossils were picked and diagnosed, including two subspecies, belonging to ten genera, and four subgenera. The recorded calcareous nannofossil assemblages include two biozones which are from the lower to the upper part of the section: (1)  Helicosphaera ampliaperta Interval  Biozone  (CNM6); (2)  Discoaster signus Interval Biozone (CNM7). These biozones are correlated with other calcareous nannofossils biozones from both local and regional sections that lead to conclude the age of the Middle Miocene(Burdigalian to Laghian). The paleoenvironment of the Fat'ha Formation was determined through the use of the environmental evidence of the Ostracoda fossils, which indicated oscillating periods which vary from normal salinity to brackish and saline environments, with shallow lagoonal environment and sometimes deep lagoonal environment that do not exceed the margin of shelf zone.

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 CaCO3 content and higher content of the Total Organic Carbon (TOC).