Structural Analyses and Oblique Negative Inversion Tectonics of Gara Baran, Part of Baikher Anticline, Kurdistan Region/ Iraq

The anomalous case of Gara Baran which is a part of a very long Baikher Anticline, is carried out using high-resolution structural analyses such as Fold Geometry, Harmonic (Fourier) analysis, Vertical Investigation of fold style, and Formation Thickness analysis. The Geometrical analysis of three traverses reveals that it is an asymmetrical anticline with average dips of the northeastern and southwestern limb (26o) and (22o) respectively and verging towards the northeast. The Fourier analysis exposes that the shape of the northeastern limb is more developed than the southwestern one. Moreover, the shape of the northeastern limb becomes less developed towards the northwest, whereas the shape of the southwestern limb becomes developed in the same direction. The Vertical Investigations analysis shows that the fold is asymmetrical and verging towards the northeast from Cretaceous to Middle Eocene, except the folding of Pila Spi Fm. which is verging towards the southwest. The fold axis and axial plane are rotated anticlockwise from the Cretaceous to the Paleogene. The dips of bedding planes are reduced towards the younger formation where the interlimb angle increases in the same direction. Formations thickness study shows that Gara Baran is influenced by negative tectonics inversion; which suffered reverse displacement during the Cretaceous to Early Eocene followed by a normal movement during the Middle to the Late Eocene due to the effect of suture listric fault. Fourier and Geometric analyses confirm that the listric fault reduces its effect towards the northwest, so this inversion can be called Oblique Negative Inversion tectonics.