Late Quaternary displacement rate of Dead Sea western marginal fault

We analyzed the structure of a fault zone and the age of deformed and displaced sedimentary units to identify recent faulting episodes and reconstruct the rate of young tectonic movements along the western margin fault of the Dead Sea Basin (DSB).

The DSB, one of the most tectonically active areas in the Levant, developed within a step-over zone between two strike-slip segments of the Dead Sea Transform fault. Its margins are bordered by normal and strike-slip faults, forming a pull-apart basin. During the Quaternary, several saline and hypersaline lakes formed within the basin, leading to the deposition of evaporites, including aragonite, gypsum, and halite. Normal fault scarps generate cliffs with elevations of 350–500 m, exposing striated surfaces and fault damage zones along in the western border of the basin. These faults cut through foothill conglomerates, which were cemented by aragonite deposits during periods of high lake levels. Newly formed fault scarps located below the lake level were quickly covered by aragonite cement. Some of these cements, along with stromatolites, were subsequently displaced and striated during newer faulting episodes.

We conducted 15 U-series age determinations on conglomerate cements and aragonite mineralization covering at least five individual fault scarps that displaced upper Pleistocene sediments. The fault scarps exposed in an outcrop of fault zone approximately 30 m wide. The ages of deformed deposits on these fault segment vary between 120 to 263 kyr for the oldest sample, to 18–21 kyr for the youngest one, with several adjacent fault segments being 83 to 51 kyr old. Additionally, conglomerates on a slope yields ages of 141–144 kyr.

Variations in cement ages along different fault surfaces indicate that each fault surface represents a discrete earthquake. By correlating the sedimentary sequence, we determined that the vertical displacement component of 14.5 m between these faults occurred between 83 kyr and 18 kyr before present. This corresponds to surface ruptures of ~1 m per individual earthquake, with an integrated vertical displacement rate of ~0.22 mm/yr.

Previous works in this fault zone suggested that activity since ~6.5 Myr while the entire stratigraphic separation in this area is 0.5-1 km. We therefore conclude that the fault is probably active without changing its location in the last millions of years while the recent subsidence rate is similar, or slightly higher than the integrated rates of 0.07-0.18 mm/yr.