Fault and salt tectonics in the southern Dead Sea basin

Abstract

The sedimentary fill of the southern Dead Sea basin contains large amounts of salt and halokinetic features. In this study, the relationship between these halokinetic features and major faults was investigated. The basis for the interpretation was seismic reflection profiles from the southern Dead Sea basin. The seismic profiles were used to construct a series of two-way time structural maps and two-way time isochore maps for the various reflectors and sedimentary sequences in the area; such maps are published for the first time in the Dead Sea basin. Electrical and geophysical logs from wells in the area were used to relate the mapped reflectors and sequences with geological units. The seismic profiles give evidence to the largest subsidence that had occurred during the late Pliocene and that the amount of subsidence was much larger in the deeper part of the basin than in the median block. This difference in subsidence is partly a result of salt withdrawal. There are two ways to explain the present day structures of the southern Dead Sea basin. Either (1) basement faulting took place before salt deposition or (2) basement faulting took place during or after salt deposition. In this research, a combination of the two is favored. In particular the influence of the movement on the longitudinal fault separating the deeper part of the basin from the median block (Sedom fault) on salt flow is outlined. The much larger offset on the Sedom Fault in the northern part of the area is thought to be the reason for salt piercing only in this part of the area. It is also suggested that the Sedom Fault has experienced strike–slip movements and not only vertical movements. A ridge, the Neot Hakikar Ridge, is shown to divide the southern basin into two sub-basins. The presence of this ridge and the salt tectonics triggered motion on a listric fault (Amazyahu Fault) in the early Pleistocene. The listric curvature of the Amazyahu Fault induced antithetic faulting recognized in the Pleistocene sediments. Earlier studies have suggested that the depocenter migrated to the north. The isochore maps, however, show that locally the depocenter shifted to the southeast. This shift is probably caused by the movement along the Amazyahu Fault and the withdrawal of salt. A much larger amount of salt than previously thought is identified and it is suggested that salt reaches as far south as the Iddan Fault.