Calcareous nannofossils from the Gurpi Formation (Lower Santonian-Maastrichtian), faulted Zagros range, western Shiraz, Iran

Abstract

The Gurpi section in western Shiraz, faulted Zagros range of southwestern Iran, contains one of the most complete Early Santonian to Late Maastrichtian sequences. The lack of a good fundamental paleontological study is a strong motivation for investigating calcareous nannofossils in southwestern Iran. The Gurpi Formation is mainly made up of grey shale. As a result of this study, 23 genera and 47 species of nannofossils have been identified for the first time. This confirms the existence of biozones CC14–CC26, which suggests the age of Early Santonian to Late Maastrichtian. All Early Santonian to Late Maastrichtian calcareous nannofossil biozones from CC14 (equivalent to the Micula decussate Zone) to CC26 (equivalent to the Nephrolithus frequens Zone) are discussed. Additionally, the zonal subdivision of this section based on calcareous nannofossils, is correlated with planktonic foraminiferal zones (Dicarinella asymetrica Zone to Abathomphalus mayaroensis Zone). We can also learn about the predominant conditions of the studied sedimentary basin that was in fact a part of the Neotethys basin with the existence of index species of calcareous nannofossils indicating a warm climate and high depths of the basin in low latitudes.