Fold geometry and kinematics of inversion tectonics for Kosrat anticline, northeastern Iraq

摘要

The Kosrat anticline structure in the northeastern part of Iraq has been studied from structural and tectonic points of view. The anticline was described and classified according to the field measurements. The southwestern limb is steeper and shorter than the northeastern one which makes it an asymmetrical double-plunged anticline verging towards the southwest. The folding kinematics model was based on the changing of the competency of the formations to have a flexural slip fold that is controlled by the compositions of the layers and the primary response of each rock unit to the deformation. Structural and tectonic history of the anticline was interpreted according to the study of faults that have been reactivated. The deduction of the reactivation was through the comparison between the thicknesses of the geologic formations in both limbs of the anticline. Parts that differ in lithology and show deformation or crushing zones in different levels were observed as a footwall shortcut and used to indicate inversion. Thin sections analysis for rock samples in extension fractures showed evidence of a faulting mechanism represented by the deformed crystals to give a clue of being inverted faults in the Kosrat anticline.