**2. Stratigraphic review**

Previous studies described the Kolosh formation at the type section in the Kolosh village in Koi-Sanjaq area, NE Iraq. [8] were firstly described as the Paleocene-Lower Eocene deposits in the high-folded zone. Buday [4] said that the formation was composed of 400 m thick blue shales and green sandstones. The above upper 174 m is of Sinjar limestone formation underlying with 140 m thick of intertonguing Sinjar and Kolosh formations. In Derbendikhan area, a section of 1000 m thick was described by Ref. [9], including many conglomerate beds with mudstones, siltstones, argillaceous, and detrital limestone interbeds. The Kolosh formation is encountered in several oil fields of northern Iraq [3, 4]. The formation was deposited in a relatively narrow rapid sinking basin trending NW-SE and was superimposed on platform margins and separated from the geosyncline by uplifted emerged and eroded lines [3, 4, 9]. No turbidite and graded bedding signs were suggested by Ref. [4], which diminished to an open sea calcareous sequence.

Previous paleontological studies ascertained the middle Paleocene age [10]. According to Ref. [11], the lower contact in the type locality is unconformable and transgressive. However, the authors [4] ascertained conformable upper contact with Paleocene-Lower Eocene limestone. The firstly discovery of olivine/pyroxene-rich sandstones of the Kolosh formation in the Badelyan locality was carried out by the study of Ref. [2].
