الملخص

Ostracode biostratigaphy were investigated in detail from three formations (Shiranish, Hartha and Mushorah ) in subsurface sections of four boreholes Northwest and centre of Iraq. On the basis of the ostracode species distribution, the studied formations were divided into four ostracode biozones as follows: Biozone 1: Cytherella IRC 22 Interval zone. (Early Campanian). Biozone 2: Occultocythereis elongata Interval zone. (Late Campanian). Biozone 3: Krithe sp. M 1113 Interval zone. (Early Maastrichtian). Biozone 4: Holcopocythere bassiporosa Interval zone. (Late Maastrichtian). Depending on the above biozones correlated with other previous works from Iraq and the Middle East regions the following ages were proposed for the studied formations: Shiranish Formation: Late Campanian - Maastrichtian. Hartha Formation: Late Campanian - Early Maastrichtian. Mushorah Formation: Early Campanian.