Relationship between the anisotropy of magnetic susceptibility and development of the Haymana Anticline, Central Anatolia (Turkey)

Authors: MURAT ÖZKAPTAN, ERHAN GÜLYÜZ

Abstract: Integrated structural and anisotropy of magnetic susceptibility (AMS) analyses were carried out on the Campanian- Maastrichtian shale-mudstone dominated sedimentary sequences (Haymana Formation) cropping out within the doubly plunging Haymana Anticline in Central Anatolia (Turkey). In order to understand the relationship between the development of magnetofabrics and the tectonic processes, six sites from different parts of the anticline were sampled and analyzed. AMS lineations from 634 cylindrical samples and structural data were collected in the field. The results show very high correlation with the structural trend of the region and indicate that the maximum susceptibility vector (k₁) is almost parallel to the Haymana Anticline fold axis (~E-W) and the trace of the Dereköy Thrust Fault, which is the basin-bounding fault at the northern margin of the Haymana Basin. In order to assess the relationship between shortening ratios and obtained AMS vectors, a number of balanced cross-sections are constructed along five traverses almost perpendicular to the axis of the anticline. Results from both the AMS and the balanced cross-sections yielded similar shortening ratios (~18%-32%) that decrease towards the eastern closure of the anticline from its culmination. In a regional sense, we related these results to compressional/transpressional deformation that formed during the Eocene to Early Miocene period. Differential shortening ratios calculated from AMS and restored balanced cross-sections indicate that the shortening is associated with the transcurrent tectonics, possibly in relation with rotational convergence of the Pontides and the Taurides and/or the oblique indentation of the Kırşehir Block into the Pontides during or subsequent to the collision.

Keywords: Anisotropy of magnetic susceptibility, compressional tectonic, balanced cross-section, Haymana Basin, Central Turkey

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