T201 Building Bridges between Modern and Deep-Time Critical Zones (Posters)

Tuesday, 24 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

PHYSICAL AND CHEMICAL ANALYSIS OF PALEOSOLS BEFORE, DURING AND AFTER PERIODS OF ANATOMICALLY MODERN HUMAN MIGRATION AT GONA, ETHIOPIA

Paper number: T201-4
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Environmental change is often inferred to have driven dispersals of Anatomically Modern Humans (AMH) out of Africa, yet the precise landscape context of these migrations remains unclear. Furthermore, fluvial-based archives of paleoenvironment during periods of dispersal are scarce. Gona, an area in northeastern Ethiopia with one of the most continuous records of East African Paleolithic and Neolithic archaeology, contains abundant Middle to Late Pleistocene fluvial deposits interbedded with tephra. This study examines the physical and chemical changes of 11 fossilized soils (paleosols) extracted from Gona’s paleoanthropological sites that range in age from the Middle to the Late Pleistocene (~380-11ka). The paleosols from Gona provide valuable insight into the landscapes in which our earliest direct ancestors interacted, as they are a dynamic biogeochemical archive of weathering, which is related to the surrounding environment at the time of formation. We focus on paleo-Vertisols, or paleosols with vertic features that formed in distal floodplain settings to provide a control on landscape position. Colorimeter results show that the paleosols become darker from the Middle to Late Pleistocene and Early Holocene. We also see an increase in organic carbon (OC) content with notable peaks at 77.5, 50, and 11 ka. CALMAG-based estimates of mean annual precipitation (MAP) range from 405 to 527 mm/yr (+/- 108), with the exception of notable increases at 77.5 (688 mm/yr +/- 108) and 11ka (656 mm/yr +/- 108). These increases in OC and MAP coincide with previously documented episodes of wetter climates - MIS-5a and the African Humid Period. The paleo-Vertisols at Gona record evidence of wetter paleoclimates during certain periods of AMH migration and suggest that this terrestrial fluvial record is a unique source for paleoenvironmental data. This localized terrestrial dataset complements additional regional-scale paleoenvironmental records when interpreting the forcing and responses of Out-of-Africa migrations.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-335724

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.