Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12136/2126
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Title: Paleosol-based evidence of dynamic Middle to Late Pleistocene climates and environmental change at Gona, Ethiopia
Authors: Takashita-Bynum, Kevin K.
Stinchcomb, Gary E.
White, Marie N.
Beasley, Madeline R.
Rogers, Michael J.
Semaw, Sileshi
Issue Date: 2020
Publisher: American Geophysical Union
Citation: AGU Fall Meeting, 2020
Abstract: What drove dispersals of Homo sapiens out of Africa? Reconstructing the Critical Zones (CZs) in which our early ancestors interacted with over time is an essential step toward addressing this question. The well-preserved fossil soils, or paleosols found in the sedimentary record at Gona, Ethiopia, contain a geochemical archive of our past environments, alongside one of the most comprehensive East African records of hominin-related archaeology and a well-constrained chronostratigraphic record. Ten paleosol profiles near hominin fossil and artifact sites that range in age from 380 to 11 ka were analyzed to reconstruct the paleo-CZs of Gona. These ten fine-grained paleosols weathered mixed alluvium and had vertic features. δ13C values (-2.40 to -7.77 +/- 0.16 ‰) derived from pedogenic soil carbonate are consistent with previous studies that show that paleo-Vertisols with this range of isotopic values at Gona likely developed within an open floodplain, dominated by riparian grassland. The constant landscape position provides this study with some control, allowing us to track changes in climate, organisms, and duration of soil formation over time. Characterization of these paleosols revealed two distinct paleosol types (i.e., pedotypes): Alsa (“Moon” in the Afar language) and Ayro (“Sun” in Afar). Alsa paleosols were darker colored with mean soil organic carbon (SOC) of 0.92 wt. %; whereas, Ayro paleosols were lighter and had lower mean SOC of 0.14 wt. %. Mass-balance geochemistry of total soil P, an essential plant nutrient, shows an average of >100 % gain in the darker Alsa paleosols compared to the lighter Ayro paleosols. Total Ca loss was greater in the Alsa (-66 %) than Ayro (-42 %), whereas total Mg loss was minimal in the Alsa (0 %), and Ayro showed Mg gain (27 %). Consistent with Ca loss, mean inorganic carbon of the <2 mm fraction is lower in Alsa (0.22 wt. %) than Ayro (0.63 wt. %). Overall, these data infer that the Alsa paleosol was more productive, experiencing more biogeochemical cycling of plant nutrients. Additionally, paleo-rainfall estimates and age-modeling suggest that the Alsa paleosols weathered under wetter climates during known pluvials. This record of Middle to Late Pleistocene floodplain CZs at Gona provides evidence of climate-influenced changes on land occupied by early humans.
Description: Ponencia presentada en: American Geophysical Union, Fall Meeting Online: 1-17 december, 2020
URI: http://hdl.handle.net/20.500.12136/2126
Editor version: https://agu.confex.com/agu/fm20/meetingapp.cgi/Paper/738289
Type: Presentation
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Appears in Collections:Congresos, encuentros científicos y estancias de investigación

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