OSCILLATIONS IN MONSOON STRENGTH RECORDED IN THE DIATOM RECORD OF PALEOLAKE HADAR FROM THE PLIOCENE HADAR FORMATION, NORTHERN AWASH VALLEY, ETHIOPIA

A paleoecological reconstruction of the lacustrine sequences from the Pliocene Hadar Formation reveals multiple oscillations in monsoon strength captured in the diatom fossil record at a high sample resolution. A quantitative limnological examination of the diatom fossil record of Paleolake Hadar was conducted as part of the Hominin sites and Paleolakes Drilling Project. The Hadar formation represents a critical point of early hominin evolution, temporally near the demise of Australopithicus afarensis and rise of Homo habilis. Samples from drill cores were exhumed at continuous two-centimeter increments throughout the lacustrine sequences of the Hadar Formation. A qualitative analysis of the diatom assemblage reveals fluctuations in the geochemical conditions and stratification history of Paleolake Hadar that are likely to have been controlled by monsoon climate variability. The new insight provided by diatom-based limnology reconstruction of the Hadar Formation provides critical improvements towards understanding the context of human origins in East Africa.