Biostratigraphy and Chronostratigraphy of Late Jurassic – Early Cretaceous in Selected Areas in Kurdistan Region, Northern Iraq

Abstract

The biostratigraphy and chronostratigraphy of Late Jurassic–Early Cretaceous (Tithonian–Aptian) successions at three outcrops in the Kurdistan Region, northern and northeastern Iraq (Amadia, Gara, and Barsarin sections) are studied depending on ammonite, planktic, and benthic foraminiferal contents. The studied formations: Chia Gara, Sarmord, and Qamchuqa, are recorded in all studied localities, while Garagu and Balambo formations are exposed at some studied localities. Age determination of the Chia Gara Formation relied on the ammonite fauna. The ammonites investigated are the major assemblage fauna of the Durangites Zone, which corresponds to the Late Tithonian. The detailed planktic foraminiferal investigation in Balambo Formation permits the recognition of five well-defined zones, these are Favusella hoterivica Interval Zone, Hedbergella sigali Interval Zone, Globigerinelloides ferreolensis Interval Zone, Globigerinelloides blowi Interval Zone, and Globigerinelloides algeriana Taxon Range Zone (part), which reveal a Late Valanginian to Late Aptian age. The stratigraphic distribution of the benthic foraminifera shows three zones, these are Everticyclammina kelleri Assemblage Zone, Pseudocyclammina lituus Assemblage Zone, and Palorbitolina lenticularis Taxon Range Zone, the 1st and 2nd zones were recognized in the Sarmord Formation at Amadia section, which extends in age from late Valanginian to Hauterivian. While the 3rd zone is recorded from Qamchuqa Formation at the Gara section representing the Early Aptian age.