Magnetochronology of Early Pleistocene lacustrine sedimentation in the hyperarid Negev Desert, southern Israel: Implications for the initial out-of-Africa dispersal of Homo

Abstract:

The Negev Desert in southern Israel hosts a number of early Pleistocene lacustrine and palustrine sedimentary sequences that attest for past wetter conditions in what today constitutes one of the driest deserts on Earth. These sequences are of special importance because the Negev Desert forms part of the only continental bridge (Sinai peninsula) that enabled initial out-of-Africa expansion of our genus Homo. Yet, the paleoclimatic significance of these sequences still remains unknown, mainly due to their uncertain age. Here we present a magnetostratigraphic study of one of these sedimentary sequences, the Kuntila Lake sediments, which was carried out at the 30 m-thick Kuntila Gate section in the southern Negev. Magnetostratigraphic measurements enable the recognition of a normal (N1) and a reverse (R1) polarity zones in the lower and upper halves, respectively, of the Kuntila Gate section. Correlation of N1 to the Olduvai Subchron (1.778 and 1.945 Ma) appears as the most likely option in view of previously published ¹⁰Be ages derived for the uppermost part of the Kuntila Member in nearby sections. The large errors associated with these ages, however, suggest that correlation of N1 to Subchron C2An.1n (2.582-3.032 Ma) is also possible. Although speculative, the presence of three lacustrine/palustrine-alluvial sequences within the Kuntila Gate section relative to the position of the N1/R1 boundary appear to support this latter option. Notwithstanding the fact that our results do not fully resolve the age of the Arava Formation, they unequivocally relate the Kuntila Lake sediments with a long period of enhanced climatic variability because the tops of both subchrons are associated with 400 kyr eccentricity maxima. The inferred wetter conditions in the Negev Desert concurred, regardless of the age correlation, with periods of lake expansion in East Africa and clusters of short-lived expansions of the savannah throughout much of the Sahara. This would have biogeographically connected Africa and Eurasia, greening the path for the initial out-of-Africa dispersal of Homo. In the talk we will further discuss the implications of this and future studies in order to better determine the timing, extent and significance of the biogeographic connection upon which the chronology of the first African dispersal of our genus hinges on.