Kinematics and geometry of normal faults at the margins of pull-apart basins: An example from the Dead Sea Basin

Abstract

The parameters controlling the geometrical and kinematical evolution of a normal fault system along the margins of a subsiding pull-apart basin are studied using the case of the Dead Sea Basin. The Western margins of the basin consist of sub-parallel normal faults and basinward tilted blocks that evolved in a layered sedimentary sequence. The faults exhibit narrow domains of fault damage, characterized by mechanical degradation of the surrounding rock materials. The slip surfaces display oblique-normal abrasive striations and waviness. Measurements of normal-to-slip fault surface roughness at more than eight orders of length-scale magnitudes, combined with directly obtained fault dips and slip orientations, suggest that at length-scales higher than ~102 m the dominant geometry of the faults change from generally wavy with multiscale undulations to a characteristic zigzag pattern with two distinct sets. We utilize the numerical, discrete elements, DDA method to explain the structural evolution of the margins. Our results suggest that the sedimentary cover deforms as a coherent system of uniformly sized blocks, exhibiting flexure in the western margins and gravitational collapse eastward into the subsiding basin, predominantly in tilted blocks mode. These conditions explain many of the observed structures in the field, including the extensional belt and the stepped basinward block-tilting of the sedimentary cover. Comparing the wide deformation belt on the western margins of the basin to the much narrower deformation zone on the eastern margins suggests that the existence of a thick sedimentary cover and its initial structure control the width of the margins and the general mode of structural deformation.