T111 The Context of Our Origins: Geological Studies of Old World Fossil Primate and Hominin Sites

Monday, 26 September 2016
8:00 AM - 12:00 PM
Room 401

THE MENENGAI TUFF: A 36 KA WIDESPREAD TEPHRA AND ITS CHRONOLOGICAL RELEVANCE TO LATE PLEISTOCENE HUMAN EVOLUTION IN EAST AFRICA

Paper number: T111-15
Program: Technical Sessions
Time: 11:25 AM – 11:40 AM

Authors

Abstract

The East African Rift preserves the world’s richest Middle and Late Pleistocene (~780 –12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites though tephrostratigraphy, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera forming eruption of Menengai Crater in Kenya and 40Ar/39Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 585 glass shards from 39 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over > 115,000 km2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker for resolving Late Pleistocene chronology relevant to paleoclimatic, archaeological and paleontological records of human evolution.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-278770

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