FLYSCH – MOLASSE SEDIMENTS OF THE PALEOGENE FORELAND BASIN OF NORTH ARABIA, SHIRANISH AREA, NORTH IRAQ

Abstract

The Paleogene clastic strata of northern part of Iraq are represented by the Kolosh Formation (Paleocene – Early Eocene) and the Gercus Formation (Middle – Late Eocene). Detailed investigations of these strata at Shiranish area of north Iraq including stratigraphic association, lithofacies type, petrographic investigation, and mineralogical analysis of heavies and clay fractions disclose the geological aspects and the nature of the Paleogene Foreland Basin, which is developed along the north – northeastern margin of the Arabian Plate.Analysis of lithofacies association of the Kolosh sediments shows that it represents a distal turbidite facies of an unattached submarine fan complex that is developed far from feeding channel systems. The Gercus lithofacies is characterized by predominant continental section with a possibility of shallow marine influence near the bottom of the section.The petrographic analysis of sandstones from both units shows the predominancy of lith-arenite type with significant occurrence of feldspar, igneous and metamorphic rock fragments in Gercus samples. Petrofacies analyses of these sandstones show that the Kolosh sandstones were derived from “Recycled Orogen” province, and developed as a part of the foreland system. The Gercus sandstones show similar tendency with clear effect of arc-volcanicity. Heavy and clay minerals analysis show assemblages, which support similar interpretation. The sediments of Kolosh and Gercus formations are believed to represent the flysch – molasse facies of the distal part of the Paleogene Foreland Basin, which is developed in North Iraq as result of the advancing Bitlis Nappes onto the northern Arabian margin.