DETERMINING AGES OF ALLUVIAL SURFACES IN HYPERARID REGIONS BY THE LUMINESCENCE METHODS

Age dating of geomorphic surfaces in mid latitudes is hampered by the limited applicability of conventional dating methods. We propose the luminescence dating methods as regular dating techniques for arid and especially hyperarid regions. We used luminescence for dating aggradational geomorphic surfaces such as alluvial fans and terraces in five drainage basins in the hyperarid Negev and Judea deserts, Israel. The surfaces were sampled from beneath the gypsic horizon at a depth of 0.3-0.7 m, below which sand grains do not penetrate, and dated using a variety of techniques on the extracted quartz and alkali feldspar. Depositional ages for the surfaces range from Middle Pleistocene (> 300,000 years) to mid-Holocene (5,000 years). In all five basins the ages are in stratigraphic order and agree well with relative age estimates based on soil chronosequences and on limited independent age control. Ages for individual surfaces cluster within ±10-20% and it is possible to distinguish between surfaces with ages differing by more than 20%. Thus in hyperarid areas the luminescence methods can be used as "surface age dating" of the last deposition that constructed the surface of the geomorphic landform.