Soils as a tool for estimating ages of Quaternary fault scarps in a hyperarid environment — the southern Arava valley, the Dead Sea Rift, Israel

Abstract

On the alluvial fan of Nahal Shehoret in the extremely arid region of the Negev desert, Israel, Reg soils developed on stable alluvial surfaces in colluvium along terrace risers and in colluvial units on a complex fault scarp were compared. The degree of soil profile development provided an age estimate of the surface that was faulted, a maximum age estimate of the scarp or terrace riser, and an estimate of the maximum recurrence intervals of faulting events. IRSL dates of the tectonically displaced alluvial surfaces and colluvial units at the same site enabled us to re-evaluate the use of Reg soils for relative dating. The major faulting event started at 34.8 ± 4.3 ka. It displaced a late Pleistocene surface of the Nahal Shehoret alluvial fan dated at 56 ± 10.8 ka. Renewed fluvial activity and deposition of alluvium on the downfaulted block had almost terminated by 13.6 ± 2.3 ka. The scarp was formed during the latest Pleistocene and was followed by smaller faulting events which had only minor effects on the fault scarp morphology. The similarity of age estimates from IRSL dating and the degree of soil development in this environment indicates that soils can be used to date surfaces and colluvial units.