Eolian sand in peridesert northwestern Libya and implications for Late Pleistocene and Holocene Sahara expansions

Abstract

Jebel Gharbi is a semi-arid mountain range on the northern boundary of the Sahara Desert, in northwestern Libya between the Mediterranean coastal plain (the Jefara) and the Tripolitanian Plateau. At Jebel Gharbi, Quaternary strata (dated by means of radiocarbon techniques and archaeological artifacts) consist of two Upper Pleistocene (Oxygen Isotope Stages 4 and 2) eolian sand beds that interfinger with loess, calcrete, alluvium, and colluvium. The deposition of the eolian sand was a consequence of the expansions of the Sahara Desert into the Jebel Gharbi area that took place during arid cold spells. During the latest Pleistocene and late Holocene, the northern margin of the Sahara Desert reached its modern position, and eolian activity was widespread on the Jefara coastal plain and in the valleys of Jebel Gharbi. The Late Pleistocene desert expansions were contemporaneous with the periods of highest sedimentation rate of non-volcanic dust in polar ice cores. The comparison between data on eolian activity in some different places outside of the present boundary of the Sahara Desert suggest that there are differences in the timing of eolian sediment mobilization and the rate of eolian sediment deposition inside and outside the Hadley cell atmospheric circulation zone. The present work confirms the influence of the size of the Hadley cells on atmosphere dust circulation patterns.