The current study depends on lithofacies analysis of Kolosh Formation at Tigran region in north-eastern Iraq. Depending on the physical criteria as grain size, color, texture, and etc., the formation is divided to five lithofacies: pebbly sandstone, coarse sandstone, graded sandstone, mudstone and shale lithofacies. Several sedimentary cycles and depositional regimes were fixed in the studied section represent by high energy regime as pebbly sandstone and medium to low regime as mudstone and shale lithofacies. Based on the data of lithofacies which compared with hypothetical model of the common turbidity deposits, the formation was deposited in submarine fans environments. The secondary depositional environments of the study section are divided into channel and inner fan environments. The Kolosh Formation in northern Iraq was deposited in an active margin basin when the northeast Arabian Plate collided with the Eurasian plate at the final stages of Neo-Tethys closing, which has resulted in large uplifts and subsidence episodes due to eustatic rises and falls.

The mineralogical study using X-ray diffraction (XRD) supported by scanning electron microscopic (SEM) examination and energy-dispersive spectroscopy (EDS) on the claystone of the Kolosh Formation from northern Iraq was conducted to Shows the provenance history of rocks. Chlorite, montmorillonite, illite, palygorskite, and kaolinite were recorded in different amounts in the study area. The association of montmorillonite and chlorite in the claystone of the Kolosh Formation (Paleocene) refers to the marine environment. Chlorite and montmorillonite are the common minerals in the Kolosh Formation with less common of illite, kaolinite and palygorskite. These clay minerals are of authigenic, detrital and diagenetically origin, which are controlled mainly by the source rocks, paleoclimatic conditions and the burial diagenesis. The clay minerals assemblages refer to be derived mainly from Fe-Mg rich with minor Si-Al rich silicate minerals, which are very common in the ophiolites associated with the basic igneous rocks. These rocks composed the major lithological units in the Zagros Thrust Belt of NE Iraq.