ESR DATING QUATERNARY SPRING ACTIVITY AND ASSOCIATED HOMINID ARTEFACTS AT KHARGA OASIS

Today, the hyperarid Kharga Oasis, Egypt, receives ~ 0.7 mm/y precipitation, but suffers > 2 m/y of evaporation, ensuring it lacks naturally occurring standing water. Yet, Pleistocene hominins visited small lakes and ponds that dotted the edge of the nearby Libyan Plateau. Pleistocene tufas deposited by springs that fed these ponds and lakes house Paleolithic artefacts. Freshwater molluscs in intercalated tufas and lacustrine silts indicate abundant potable water to support hominins, a diverse fauna, and locally lush vegetation. Dating these tufas pinpoints the pluvial events that led to high watertables, enhanced spring activity, and thereby, enabled hominin occupation in, and potentially migration through, the Western Desert. At Wadi el Midauwara, a tufa mound complex covering ~ 25 km² has grown as tufa, dammed small ponds, and lakes from 1-5 m² to 1.5 km² in area that trapped calcareous lacustrine silt. Developed Oldowan, Acheulean, MSA, Khargan, Levalloiso-Mousterian, Aterian, Epipaleolithic, and Neolithic artefacts, as well as chert nodules, dot the gravel lags flooring the small basins and blowouts within the tufa mound complex. Since electron spin resonance (ESR) can date aragonite molluscs ranging from 5 ka to 2 Ma with 5-10% precision, >30 Melanoides tuberculata samples from Midauwara were dated with standard ESR. Although more accurate modelling for the time-averaged cosmic dose rate would improve their accuracy, the preliminary ESR analyses suggest that freshwater and snails existed at Midauwara, Egypt, during at least four different periods: Oxygen Isotope Stage (OIS) 1-2, OIS 5, OIS 6c, OIS 7, and in the early Pleistocene before the Olduvai Subchron. In the Earliest Pleistocene or Latest Pliocene, at 2.0 ± 0.3 Ma, abundant water existed to enable the first hominin migration out of Africa via the Western Desert.