Early to late Pleistocene 10Be exposure ages of abandoned surfaces in the Negev desert reveal the regional drainage evolution history and its relationship with the subsidence of the western margin of the Dead Sea Rift. The dated desert paved surfaces have developed over originally westward-flowing rivers, which were abandoned by early Pleistocene and whose relicts are now progressively tilted towards the rift axis. The slow and non-destructive subsidence coupled with extreme hyperaridity enabled the preservation of these ancient surfaces along some of the main water divides in the Negev, nearly irrespective of their distance from the rift axis. Constraints on the tilting history are obtained from analyzing the spatial pattern of the exposure ages, suggesting subsidence rates as low as 120-300 m Ma-1 in the southern Arava Valley since the late Pliocene. It is shown that the transition from the Pliocene to current drainage pattern occurred over a short period during the early Pleistocene, and that the governing fluvial response that followed the delineation of current basins is represented by a continuous spectrum of ages of inset terraces.
Bibliographical noteFunding Information:
This work would not be possible without the insightful discussions with Ezra Zilberman, a field trip with Hanan Ginat and Bruce Harrison, and the extensive reviews by Yehouda Enzel and Zvi Garfunkel. We thank the editor and two anonymous reviewers for significantly improving this manuscript. BG is greatly indebted to Itay Nudel, Shalev Siman-Tov and Rotem Golan for field assistance, Nadia Teutsch for performing the ICP-OES analysis, Ramon Arrowsmith for encouragement and Dad for mathematical advice. This research was funded by ISF grant 188/06 and the Lady Davis Foundation .
- Dead Sea Rift
- cosmogenic isotopes (Be)
- desert pavement
- drainage reversal
- subsidence rate