The effect of the inherited Miocene extensional geometries during the inversion of the Sarajevo Basin, Bosnia & Herzegovina

Abstract

The effect of inherited basin structure and rheological stratification of a basin fill on the deformation created by inversion is a topic which has not received a lot of attention. Therefore we studied the Sarajevo-Zenica basin, a late Oligocene – Miocene endemic intramontane basin, situated in the Dinarides mountains of Bosnia and Herzegovina. To establish how inherited basin properties, structural and rheological, exerted control on the inversion deformation. We carried out structural and lithological mapping to examine the basins pre-inversion evolution and analyse its effect on the inversion. Two deformation events affected the basin before inversion. It was initiated as a foredeep basin during late Oligocene - Miocene during a phase of compression, and opened further during a phase of extension associated with the opening of the Pannonian basin in the Early – Middle Miocene. The basin was inverted obliquely to its NW-SE structural trend, in the Late Miocene by a N-S oriented compression, which is generated by the convergence of the Adriatic plate into the Dinarides. Inversion created a large E-W striking thrust through the centre of the basin which connects to a detachment in the Bosnian Flysch. Folds striking E-W to NW-SE were formed. Due to the oblique angle of inversion the thrust sheet moved over oblique ramps inherited from the NW-SE trending normal fault blocks created during extension. Tear faults were formed to accommodate for the hanging wall slipping over these oblique ramps. Lateral movement along these tear faults rotated some E-W striking structures in the hanging wall to a N-S orientation. The deposition of coarse competent lithologies along the SW basin margin which transition into finer incompetent lithologies towards the NE basin margin created a rheological stratification of the basin. Where the basin fill was more competent the inherited structure exerted a stronger control in the inversion deformation, while inversion deformation in areas with incompetent lithologies was much less controlled by the inherited structures.