Large-scale submarine rotational slumps and growth faults in the Eastern Mediterranean

Abstract

Submarine slumps with areas of 1000 km 2 and more disturb the continental margin of Israel and nearby areas. In them the Plio-Quaternary silty-clayey sediments, up to 1.5–2 km thick, are broken by shore-parallel growth faults into 5–10 blocks which are generally rotated and tilted landward. The faults flatten downward and become rooted in ridges formed by deformation of the underlying mobile Messinian evaporite-bearing series. Deformation is thin-skinned and does not visibly extend to deeper levels. Slumping occurred only where a sufficiently thick overburden accumulated over a sufficiently well developed mobile substrate. Then gravitational instability developed and led to basinward sliding of the continental margin sediments over the Messinian series which acted as a lubricant and a level of decollement. The mobility of this series is probably caused by overpressured shale beds that are confined between the impervious evaporites. This mechanism explains all the features of the slumps. Hitherto, faults directly related to the slumps of the Eastern Mediterranean were not identified, but since the region is tectonically active it is not possible to exclude the possibility that basinward sliding was triggered either by motion of minor underlying faults or by seismic shaking. However, it seems that even if this were the case, slumping could be triggered only because the continental margin was anyhow gravitationally unstable or close to such a state. Therefore, the gravitational instability was the main factor that controlled the deformation of the Pliocene—Quaternary sediments. The slumps of the Eastern Mediterranean resemble large-scale slumps that are known from other passive continental margins in the world.