ABSTRACT
Optical dating of variably pedogenically-altered, unconformity-bounded sand-sheets from the Selima Sand-sheet, Eastern Sahara indicate numerous periods of Latest Quaternary aeolian sediment accumulation within this flat-lying hyperarid region, punctuated by phases of pluvial lake and wadi deposition. Key Late Pleistocene and Holocene sand-sheet depositional phases occurred c. 15–20 and c. 3–4 ka. The pluvial period following the emplacement of the 15–20 ka sand-sheet resulted in complete obliteration of primary sedimentary structures and the development of a cohesive, mixed coarse sand and granule-dominated deposit which exhibits incipient prismatic soil structural development. Primary sedimentary structures, including planar and ripple laminations have not been destroyed within the c. 3–4 ka and younger sand-sheets. A distinction between bedded, slightly cohesive sand-sheet sediments and entirely uncohesive sediments is used as a basis to distinguish between latest Holocene and contemporary sand-sheet units. The age estimated presented for the sand-sheets indicate rates of accretion of between 1 and 12 cm.ka-1.
