Biostratigraphy of the Balambo Formation (Lower Cretaceous ) in Jebel Azmer – Sulaimaniya Area, Northeastern Iraq

Abstract

The Balambo Formation (Lower Cretaceous), exposed on Jebel Azmer in Sulaimaniya area northeastern Iraq, consists mainly of well bedded hard limestone. Outcrop of 224 m of the upper part of the Balambo Formation are well exposed on the surface with a steeply dipping angle. Planktonic foraminifera represent the major microfossil assemblage of the Balambo Formation. Nineteen cosmopolitan planktonic foraminiferal species were recorded from 92 samples. The identified planktonic foraminifera are of typical Tethyan character. Biostratigraphically the exposed part of the Balambo Formation is defined by four zones and two subzones, these are in ascending chronological order: Ticinella primula Zone, Biticinella breggiensis Zone which is divided into two subzones (Ticinella praeticinensis and Rotalipora subticinensis Subzones), Rotalipora ticinensis Zone and Rotalipora appenninica Zone. Accordingly the age of the Balambo Formation in Jebel Azmer is Middle–Late Albian. The presence of a major hiatus at the end of the Rotalipora appenninica Zone delineates the upper boundary of the formation in the studied section.