Middle Miocene integrated stratigraphy, paleoclimatic and environmental turnover imprints from the Kurdistan Foreland Basin, N. Iraq.

Integrated stratigraphic and sedimentological analysis have been used to reconstruct the paleoclimatic and paleoenvironmental history of the nonmarine siliciclastic deposits of the Injana Formation (Langhian-Serravallian) from the Kurdistan foreland basin (N. Iraq).The transition from marine to nonmarine deposits resulted from the gradual retreat of the Neotethys seaway SE-ward, sea level change, and the rising of the Zagros Fold-Thrust Belt. The last marine foreland deposits (Consist of mixed lagoonal carbonates and evaporites) of the Fatha Formation (Burdigalian) vary from the predominated nonmarine fluvial deposits of the Injana Formation siliciclastic deposits (with predominated sandstone, mudstone, and claystone). Bioevents variations are evident in benthic foraminiferal (Ammonia beccarii, miliolides). The marine mollusca represent by pelecypods and gastropods (i.e.,   Ostrea latimarginata , Ostrea subangulata, Clausinella persica, Clementia sp.,Cardium spp, Acteocina spp, Turbo sp.). The ichnofossil assemblages also shows varation from predominated Planolites, Thalassinoides  to Skolithos   and Scoyenia . The freshwater ostracods (Cytheridella, Penthesilenula) and brackish” water ostracods (i.e., Cyprideis) have been recorded in non -marine sequences while Chrysocythere spp, are predominated in the lagoonal parasequences.  Although Miocene mammals are rarely found in the Kurdistan foreland basin, recently, new terrestrial vertebrate remains were discovered, confirming the transition from marine to nonmarine depositional environments. This transition was associated with climate change from the warmest condition of the middle Miocene climate optimum (MMCO) to a colder condition. In addition, the XRD results indicate that clay mineralogy is changing, as illite-chlorite assemblages are replaced by bentonite-montmorillonite clays. The XRF results indicate the predominance of iron and silica oxides in the nonmarine deposits, whereas calcium, magnesium, sulfur oxides, and alkalis characterize the earlier marine deposits. These new results, in addition to the discovery of terrestrial vertebrate remains and the rise of the Zagros Mountains, show that the middle-late Miocene time was a critical period in shaping the present-day habitat in the NW Zagros belt.