Geomorphological Map of the Tadrart Acacus Massif and the Erg Uan Kasa (Libyan Central Sahara)

摘要

Here we present a geomorphological map of the Tadrart Acacus Massif and Erg Uan Kasa (SW Libya, central Sahara). The geomorphological mapping of the area was carried out by means of satellite imagery analysis followed by detailed control of units in the field. The Tadrart Acacus is a sandstone massif delimited to the West by a high scarp and cut by a dendritic fossil drainage network of W-E-oriented wadis. The massif has been shaped since the Tertiary by etchplanation and solutional processes; the latter is demonstrated by the ruiniform landscape and the high number of caves and rock shelters that dot the vertical cliffs of the wadis. To the East, the Tadrart Acacus merges below a complex system of sand ridges that form the Erg Uan Kasa. The large interdune corridors of the sand sea are dotted by lake sediments, which formed during the Pleistocene interglacials and the African Humid Period of the Holocene, when piezometric lakes were sustained by intense monsoonal rainfall. Geomorphological investigation demonstrates that the extant landscape originated thanks to the overlap of surface processes triggered by divergent (humid/arid) environmental conditions.