Geometric Analysis of the Khwelen Anticline from the Western Zagros Fold Thrust Belt in Kurdistan Region, NE Iraq

Khwelen Anticline is one of three en echelon anticlines (Ashdagh, Qarawais, and Khwelen) within the low Folded-Thrust Zone, part of the NW segment of the Zagros Fold-Thrust Belt in the Garmian district of the Iraqi Kurdistan Region. The anticline is close to the high-folded thrust zone - low folded thrust zone boundary. It is on the same trend as the Chamchamal anticline. The exposed rocks unit in the anticline range in age from the early Oligocene to the late Miocene, represented by five geological formations. The Kirkuk group and Jeribe Formation cropped out (in deep valleys) at the eroded core of the anticline. The Fatha Formation, as a carapace, forms the main geometric body shape of the anticline. While the Injana Formation is located at the two neighbouring synclines. The field observation along the three traverses perpendicular to the structure with the aid of remote sensing data, in addition to the geometrical analysis of the anticline, shows that the Khwelen anticline is asymmetrical, and single-plunged, ~10 km long and 5 km wide, open box fold with NW-SE trend. Its SW limb is steeper and more deformed than the NE limb. An oblique strike-slip fault (transverse fault) cuts the anticline at its maximum wavelength. This fault separates the Khwelen anticline from the Qarawais anticline at SE. This study reveals that the anticline is a fault propagation fold developed above the thrust fault, starting from the detachment level at the base of the Jurassic series or in the Triassic.