Microbiostratigraphy and paleoecology of the Bajwan Formation (Chattian) from the Kirkuk Oil Field (K. 160), Kirkuk area, Northeastern Iraq, are investigated. Thirty-one species from 17 genera of large benthic foraminifera in addition to non-foraminifera fossils such as Gastropods, Bivalves, and Echinoid fragments, Bryozoan, Coral, and Algae are recognized from the studied well. Based on the recognized large benthic foraminifera, it is subdivided into two biozones: Praerhapydionina delicate–Peneroplis evolutus Assemblage zone and Praerhapydionina delicate–Archaias kirkukensis Assemblage zone. Both suggest Late Oligocene (Chattian) age. The recognized biozones were correlated with comparatively well-known biozones from other parts of the Tethys region which showed a good comparison between the biostratigraphic zones established in this study with other studies. The biotic associations identified in this study suggest that this association thrived in tropical-to-subtropical environments, generally found in a restricted to shallower water depth, with normal water salinity environment ranges from 34 to 50‰, under mesotrophic-to-oligotrophic conditions.

研究了伊拉克东北部基尔库克地区基尔库克油田 (K. 160) Bajwan 组 (Chattian) 的微生物地层学和古生态学。从研究井中识别出来自 17 个大型底栖有孔虫属的 31 个物种，以及腹足类、双壳类和海胆类碎片、苔藓虫、珊瑚和藻类等非有孔虫化石。根据公认的大型底栖有孔虫，它被细分为两个生物区：Praerhapydionina crush-Peneroplis evolutus组合区和Praerhapydionina crush-Archaias kirkukensis集合区。两者都表明晚渐新世（Chattian）时代。公认的生物区与特提斯地区其他地区相对知名的生物区相关，这表明本研究中建立的生物地层区与其他研究有很好的比较。本研究中确定的生物关联表明，这种关联在热带至亚热带环境中蓬勃发展，通常发现于浅水深度，在中营养至贫营养条件下，正常水盐度环境范围为 34 至 50‰。