PALEOSOLS IN ARID LANDS. POLYCYCLIC PEDOGENESIS ON THE MESSAK PLATEAU (FEZZAN - LIBYAN SAHARA)

The Messak Sattafet is a wide plateau cut in Cretaceous sandstone, interpreted as relict of a Tertiary peneplain, heavily affected by fluvial dissection and aeolian deflation. Notwithstanding this, discontinuous soil bodies are locally persevered below the stony desert pavement. The paleosols represented by these pedological remains were generated by soil forming processes as clay illuviation, rubification, gilgai microrelief formation, which acted during different periods of the Quaternary and were interrupted by several erosional phases and episodes of aeolian input. Radiocarbon and U/Th datings and archaeological material content allow to date the soil forming phases (in a wet environment) and alternating desertification periods since the Middle Pleistocene up to the Holocene. Relationships between paleopedogenesis and climatic changes is assessed on the base of field evidence, routine analyses and micromorphology.