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, all of which were previously recorded from Iraq and adjacent regions. The occurrence of these species leads to conclude a continental shelf environment, while they are typical of inner shelf-outer shelf depth.

A Detailed Calcareous nannofossil study conducted on the Bekhme Formation that is cropped out at the Southern limb of the Bekhere anticline, eastern ward of the Dohuk city near Bajlur village, northern Iraq. The Bekhme Formation is composed of marly limestone, Organic limestone and fossiliferous limestone. The nannopaleontological classification of these calcareous nannofossils led us to determine thirty-four genus/species belonging to nine families. The nannobiostratigraphic analysis suggested three calcareous nannofossils biozones from oldest to youngest are: (1) Quadrum sissinghii Interval Zone; (2) Quadrum trifidum Interval Zone; (3) Tranolithus phacelosus Interval Zone. These biozones suggest that the studied section from the Bekhme Formation is the Middle to Late Campanian, and it refers to temperature fluctuations which considered as possible warm time period at subtropical areas.

A detail paleoenvironmental study of ostracods fauna to investigated the paleoenvironment of Khurmala Formation for two section Northern Iraq; the first (Hjran section) lies near Shaqlawa city, and the second (Dohuk section) lies near Dohuk city. Based on ostracods study conclude that Khurmala Formation were deposited in shelf environment, about (30 -200) meter in depth.