The Fold Style Variations of Baikher Anticline - Northern Iraq

Abstract

The changes in fold style of Baikher Anticline were obtained by determining the fold shape, the values of interlimb angle and the degree of cylindricity in four cross-sectional traverses. The fold shape was calculated mathematically using the Fourier analysis method whereas the Ramsay and Huber classification method was applied for deciphering the cylindricity of the fold and the Pi-diagrams for determining the values of interlimb angle in each traverse. The axial changes of the fold style revealed that the area that is occupied by Baikher Anticline was divided structurally into four segments according to their trend and vergence besides their comparison laterally with the related faults. Data analysis revealed that Baikher Anticline is double plunging, asymmetrical, open to gentle and cylindrical in the four segments, whereas the fold vergence and shape differ from a segment to another. Baikher Anticline is verged southwestwards in the first and third segments, northeastwards in the second segment and northwards in the forth one. The analyses revealed that the fold shape ranges from chevron to box shape from traverse to another. The anticline related faults fall into two categories. The first is a set of strike-slip type which influenced the fold trend whereas the second is listric faults that affected the fold vergence. Vertical investigations of fold style were also carried out in the second and third traverses. The second traverse proved the Middle Eocene reactivation of the foreland listric fault, whereas unexpected vergences showed in the third one.