干旱区生态环境知识资源中心

The interdunal areas in the Nizzana linear sand dune held contain both sandy and silty sediments. A series of trenches was excavated across the interdunal corridor exposing stacked sequences of silty and sandy units which are locally restricted to palaeodepressions, The silty units contain fining upward sequences and are interpreted as overbank deposits from the Nahal Nizzana. Thermoluminescence dating and identification of buried palaeosols indicates that the silt and clay layers were deposited over a period of several thousands of years in the late Pleistocene. The sands between the silt layers have been fluvially reworked and are not primary aeolian deposits. The stacked sequences of fluvial deposits indicate that the palaeodepressions persisted in the landscape for a significant time attesting to longterm stability of the interdunal areas. It also suggests that the linear dunes themselves have not moved laterally during this time despite climatic changes and devegetation. Since the end of the late Pleistocene the Nahal Nizzana has downcut and overbank deposition no longer occurs within the interdunal corridors, The playa deposits today are positive relief features indicating that topographic inversion has occurred and that the interdunal areas are geomorphically active.