Calcareous nannofossils bioevent throughout the Cretaceous -Tertiary boundary in kh-4 well, Northern Iraq

The specified systematic study of calcareous nannofossils was carried out on successions of Shiranish and Aaliji Formations. Four Samples have taken from (Kh-4) well, between (2600-2630) m, Northern Iraq. Twenty-five species were identified. According to the identified taxa, two biostratigraphic biozones were determined, from oldest to youngest:   
1- Rienhardtites lives Interval Biozone (CC24) Part.  
2- Fasciculithus tympaniformis Interval Biozone (CP4) Part.  
Based on the above biozones, the age of the upper part of the Shiranish Formation was defined with Early Maastrichtian because of missing the CC25 and CC26 Biozones, and the lower part of Aaliji Formation that concludes the age of Middle Paleocene because of missing the CP1, CP2 and CP3 Biozones.