Biostratigraphy and paleoecology of the Anah formation (Upper Oligocene) in the Sangaw Area, Sulaimania Governorate, Kurdistan Region, NE Iraq

Biostratigraphy and paleoecology of the Anah Formation are investigated for the first time in the Sangaw area, Sulaimania Governorate, Northeastern Iraq. Forty species of larger foraminifera and skeletal fragments of brachiopod, coral, pelycepods (bivalves), gastropods, bryozoan and algae shell, are described in seven samples collected from one section near the Pungala village. Based on the distribution of the larger benthic foraminifera and other skeletal grains, two assemblage biozones of Upper Oligocene (Chattian) age have been recognized. During the Chattian, the carbonate deposits of the Anah Formation in the studied section are mostly composed of coralline red algae and large flat benthic foraminifera. The biotic associations identified in this study suggest that the carbonate sedimentation of the Anah Formation thrived in tropical to subtropical waters under oligotrophic to mesotrophic middle ramp environment with normal seawater salinity to a higher salinity inner ramp setting and at water depths that ranged from 40 to 80 m.