A revised chronology for Pleistocene paleolakes and Middle Stone Age – Middle Paleolithic cultural activity at Bîr Tirfawi – Bîr Sahara in the Egyptian Sahara

Abstract

At Bîr Tirfawi and Bîr Sahara in the now hyperarid Egyptian Sahara, relict lake deposits located in adjacent deflation basins near 22°54′57.58″N 28°50′19.54″E preserve evidence of different hydroclimate conditions that enabled cultural activities during the Middle Stone Age – Middle Paleolithic (MSA-MP). Single aliquot regeneration optically stimulated luminescence (SAR-OSL) dating techniques were applied to sediment samples with archaeological contexts to generate a more precise geochronology for the groundwater-supported lakes and prehistoric activities in the region. New age determinations on nine samples collected from Bîr Sahara East and Bîr Tirfawi are presented for the five paleolake phases originally described by the excavation team. The new analyses yielded dates that are more precise, and refine the original geochronology for water availability at this location. The determinations suggest that some of the originally defined lake phases are temporally indistinct. SAR-OSL dates of the West 2 and West 3 lake phases defined at Bîr Sahara East overlap in time, and are contemporaneous with the Grey 3 phase at Bîr Tirfawi, at around 102 ka. The refined age for the Grey 1 phase at Bîr Tirfawi dates to 135 ± 21.6 ka, and two dates for the Post-Lake phase at Bîr Sahara center around 41 ka. A probability distribution plot (pdf) of all nine of the analytical results resolves the chronology of groundwater-supported paleolakes and prehistoric activities in the region around 41 ka (MIS 3), 80 ka (MIS 5a), 102 (MIS 5c-d), and 115 ka (MIS 5d-e). Precise dates for the sediments at these archaeological sites are important for several lines of multidisciplinary inquiry, including the role of Middle-Late Pleistocene climate on landscape change and water availability, variations in material culture and the adaptations in populations of anatomically modern humans (AMH) in the Sahara. Research in the Bîr Sahara – Bîr Tirfawi region is particularly interesting because the sites are within the modern hyperarid core of NE Africa, and are not located along the coasts or major waterway corridors “Out of Africa” like the Nile Valley. Semi-permanent paleolakes and long-lived spring-fed oases located in the modern arid belt west of the River Nile between Egypt and Sudan were crucial biomes for sustaining the lifeways and dispersal of Homo throughout the Quaternary. However, the importance and the role of such ecosystems dispersed across the North African landscape is somewhat underestimated in existing hypotheses that aim to describe hominin adaptation and dispersals.