BIOSTRATIGRAPHY OF BOLIVINOIDES AND NEOFLABELLINA BENTHIC FORAMINIFERA IN THE UPPER CRETACEOUS SHIRANISH FORMATION, KURDISTAN REGION, NE IRAQ
The Shiranish Formation contains diversified assemblages of both benthic and planktic foraminifera. Previous works on planktic foraminiferal biostratigraphy suggests that the formation was deposited in the Late Campanian – Early Maastrichtian time indicated by Globotruncana aegyptiaca, Gansserina Gansseri and Contusotruncana Contusa biozones. This work is focused on two benthic foraminifers (Bolivinoides and Neoflabellina) which are globally important in Upper Cretaceous biostratigraphic correlations. The present study is based on 235 samples collected from two different sections in the Kurdistan Region of Iraq which are Azmer (144 m) and Dokan (260 m) in thicknesses. Both areas represent nearly complete Late Cretaceous outcrops of the Shiranish Formation. Six different species of Bolivinoides and three different species of Neoflabellina benthic foraminifera are recorded and illustrated and their biostratigraphical importance are also discussed. The Bolivinoides are represented by B. decoratus, B. delicatula, B. draco, B. laevigatus, B. miliaris and B. pustulata. Moreover, the Neoflabellina are represented by N. numismalis, N. permutata and N. rugosa. The present results are compatible with the Late Cretaceous global distribution of Bolivinoides and Neoflabellina benthic foraminifera, which are commonly used for biostratigraphic correlations. The group of benthic faunas identified in the present work suggests that the Shiranish Formation is mostly deposited in outer shelf to slope environments with a shallowing-up succession recorded in the Earliest Maastrichtian.