Internal deformation of the southeast Levant margin through continued activity of buried mass transport deposits

Abstract

Mass transport deposits (MTDs) are commonly regarded as motionless evidences of past mass wasting events. Three-dimensional seismic surveys acquired offshore central Israel reveal continued long-lasting and even current deformation of >1.5 Myr old MTDs, now buried hundreds of meters beneath and still impacting the seafloor. Faulting and folding of the Messinian-Pliocene unconformity (M), at the base of the studied interval, represent the possible impacts of tectonic and halokinematic deformation. However, an ~200 m thick continuous stratified unit straddles the M and entirely separates the overlaying Plio-Quaternary sedimentary stack from underlying faulting. Overlaying and etched into this stratified unit are headscarp regions of two up to 450 m thick buried MTDs, characterized by distinct combinations of chaotic seismic reflections and typically ~1 km wide detached and rotated blocks. “Crowns” of growth faults emanate upward from these MTD headwalls, truncating and deforming the overburden and offsetting overlaying reflections by tens of meters up to ~100 m below the seafloor. Moreover, asymmetric sagging and faulting of the overburden mimic the layout and flow pattern of the MTDs and rafted blocks within, providing kinematic indications of combined compaction and lateral flow. These observations imply that the MTDs undergo continuous postslumping differential compaction, combined with lateral mobilization. Additional smaller and younger buried MTDs distributed within the overburden are observed to portray similar deformation kinematics. We suggest that the buried MTDs provide deformational foci and pathways for downslope internal collapse of the continental margin at large, offering a new possible mechanism of thin-skinned extension.