Quaternary units in makhteshim, Negev Desert: Similarities and peculiarities

The relief structure of all the makhteshim located in the Negev Desert is very similar and represented by sequences of alluvial terraces and pediments. Many of these sequences consist of terraces and pediments having the same relative heights, similar sedimentology, and the same numerical ages in all the makhteshim. But the number of these landforms is different: it is lowest in Makhtesh Ramon, where the two highest terraces and pediment surfaces are absent, and is highest in Makhtesh Hatira. The differences in the morphostratigraphy of the makhteshim can be explained by the different intensity and direction of tectonic movements in the northern and central segments of the Negev during the Miocene-Pliocene. The high position of the makhteshim in relation to their base level in the Dead Sea. which was established in the Late Miocene or the Pliocene, exposed them to a continuous, ongoing erosion regime. However, climatic fluctuations during the Pleistocene were the main factor that determined the similar morphostratigraphy of fluvial terraces and pediments in the makhteshim. It is suggested that even minor climatic fluctuations within climatic phases (both pluvial and interpluvial) in a sensitive desert region can induce a major change in the reaction of the fluvial systems.