الملخص

On the basis of the biocontents, lithological features and analysis of the microfacies, an attempt is made to establish the nature of paleoecology and depositional environments of some Upper Cretaceous formations from northwest and middle Iraq ,of which the successions are represented by the formations from the oldest to the youngest are Khasib, Tanuma, Sa'di, Mushorah, Hartha and Shiranish.A wide spectrum of environmental types distributed between deep and shallow marine environments. The implication of paleoecological interpretations for different Ostrscode species and other fossils recorded in the studied sections highlights the strong correlation between the environmental parameters in particular the depths and the lifestyle of these organisms including specific morphologies and faunal abundance.In addition to that from palaeocological point view the identified biocontents represent a southern shelf tythes fauna.