Poster Title

A terrestrial reconstruction of Gona, Ethiopia before and during the African Humid Period

Grade Level at Time of Presentation

Senior

Major

Earth Science

Minor

Biology

Institution

Murray State University

KY House District #

5

KY Senate District #

1

Department

Earth and Environmental Sciences

Abstract

The African Humid Period (AHP) resulted in more humid conditions across Northern and Eastern Africa from 15 to 5 thousand years ago (ka). This wetter climate affected flora, fauna and the Homo sapiens living in East Africa. The lack of terrestrial paleoenvironmental reconstructions is a problem in East Africa, especially during the AHP, where most are done utilizing lacustrine or marine proxies. In the case of Gona, Ethiopia, terrestrial proxies are desired due to the rich archaeological and fossil concentrations that occur in the area. Paleosols provide more direct, localized reconstructions that provide context for these finds. This study utilizes paleopedology, geochronology, and geochemistry to reconstruct the environment of Gona during the AHP.

We examine paleosols from the Erole and Odele drainages within Gona. The Odele paleosol weathered before the AHP, between the Korina Tuff (<39 ka) and the Kilaitoli Tuff (~25.7 ka). The Erole paleosol is above the Kilaitoli Tuff and immediately above a calibrated 14C age of 12 ka. These paleosols formed in floodplains of tributaries that flowed into the nearby Awash River. Strain calculations show more volumetric collapse at Erole (-39 ± 8 %) than at Odele (-5 ± 4 %). The open-system mass-transfer coefficient, tau, shows average losses of 25 ± 13 % SiO2 and 71 ± 6 % CaO at Erole, which are greater than losses of 8 ± 4 % SiO2 and 7 ± 3 % CaO at Odele. These calculations suggest more weathering and dissolution of minerals during the AHP, as well as more bioturbation. The results of this paleosol comparison are consistent with wetter conditions during the AHP that facilitated the development of grasslands along tributary valleys.

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A terrestrial reconstruction of Gona, Ethiopia before and during the African Humid Period

The African Humid Period (AHP) resulted in more humid conditions across Northern and Eastern Africa from 15 to 5 thousand years ago (ka). This wetter climate affected flora, fauna and the Homo sapiens living in East Africa. The lack of terrestrial paleoenvironmental reconstructions is a problem in East Africa, especially during the AHP, where most are done utilizing lacustrine or marine proxies. In the case of Gona, Ethiopia, terrestrial proxies are desired due to the rich archaeological and fossil concentrations that occur in the area. Paleosols provide more direct, localized reconstructions that provide context for these finds. This study utilizes paleopedology, geochronology, and geochemistry to reconstruct the environment of Gona during the AHP.

We examine paleosols from the Erole and Odele drainages within Gona. The Odele paleosol weathered before the AHP, between the Korina Tuff (<39 >ka) and the Kilaitoli Tuff (~25.7 ka). The Erole paleosol is above the Kilaitoli Tuff and immediately above a calibrated 14C age of 12 ka. These paleosols formed in floodplains of tributaries that flowed into the nearby Awash River. Strain calculations show more volumetric collapse at Erole (-39 ± 8 %) than at Odele (-5 ± 4 %). The open-system mass-transfer coefficient, tau, shows average losses of 25 ± 13 % SiO2 and 71 ± 6 % CaO at Erole, which are greater than losses of 8 ± 4 % SiO2 and 7 ± 3 % CaO at Odele. These calculations suggest more weathering and dissolution of minerals during the AHP, as well as more bioturbation. The results of this paleosol comparison are consistent with wetter conditions during the AHP that facilitated the development of grasslands along tributary valleys.