RECONSTRUCTING ENVIRONMENTS OF HOMININ OCCUPATION, WESTERN DESERT, EGYPT, THROUGH SEDIMENTOLOGIC AND GEOCHEMICAL ANALYSES OF PLEISTOCENE LACUSTRINE, PALUDAL, AND SPRING DEPOSITS

During Pleistocene humid phases the oases of Dakhleh and Kharga, Western Desert, Egypt, would have been attractive places to hominin migrants through North Africa. Enhanced availability of surface water during these humid phases is demonstrated by fluvial, lacustrine, paludal, and spring sediments preserved within the oasis depressions. Groundwater-derived deposits occur both along the escarpment flanks and within the oasis depressions; the chemical composition and sedimentary facies of these spring deposits vary significantly with geomorphic setting. Along the oasis floors, isolated ironstone spring mounds indicate locations of discharge from the Nubian Aquifer, whereas spring carbonate strata along the escarpment flanks record spring flow sourced in a higher elevation carbonate aquifer. Extensive Pleistocene lacustrine/paludal sediments occur in Dakhleh, but not in Kharga Oasis; the Dakhleh deposits suggest that much of the oasis depression was at times covered by wetland, with some regions of deeper water. Faunal material recovered from Dakhleh paleolake sediments is consistent with a savanna environment. Mineralogy, petrology, elemental chemistry, and, in the case of the spring and lacustrine carbonates, isotopic geochemistry of these sediments provide information regarding depositional environments and climatic setting. Earlier (ESA) and Middle Stone Age (MSA) lithic artifacts have been found in association with spring and lacustrine sediments in both oases; however, most archaeological materials are found as surface lags, complicating but not preventing an understanding of landscape use during the Pleistocene. Geochronological constraints on the timing of humid phases based on U/Th dating of spring carbonates suggest that spring activity along the oasis margins occurred frequently throughout the period from 100-200 ka, and less so from 200-400 ka and after 100 ka.