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Title: Fluvial response to Quaternary hydroclimate in eastern Africa: Evidence from Gona, Afar, Ethiopia
Authors: Stinchcomb, Gary E.
Quade, Jay
Levin, Naomi E.
Iverson, Nels
Dunbar, Nelia
McIntosh, William
Arnold, Lee J.
Demuro, Martina
Duval, Mathieu
Grün, Rainer
Zhao, Jian-xin
White, Marie
Hynek, Scott A.
Brown, Francis H.
Rogers, Michael J.
Semaw, Sileshi
Keywords: Ethiopian rift;Fluvial aggradation;Fluvial incision;Paleosol;Radiocarbon;pIR-IRSL;U-series;Electron spin resonance;Tephrochronology;Homo sapiens
Issue Date: Jun-2023
Publisher: Elsevier
Citation: Quaternary Science Reviews, 2023, 309, 108083
Abstract: The Busidima Formation in the Afar region, Ethiopia, spans the Quaternary and records the cultural evolution of the genus Homo. Yet, the Middle Pleistocene to Holocene fluvial environments in which early humans lived are undersampled in eastern Africa. This paper examines the stratigraphy, geochronology and paleoenvironments of the newly designated Odele Member of the uppermost Busidima Formation (<152 thousand years ago (ka)), which has received little attention despite representing a critical period in the evolution of early Homo sapiens and its migration out of Africa. The Odele Member is 40–50 m thick and is dated using tephrochronology, radiometric, luminescence, and electron spin resonance techniques. The member spans 151 to 7 ka, defined at the base by the widespread Waidedo Vitric Tuff (WAVT, 151 ± 16 ka modeled age and 95.4% credible interval - C.I.). There are two prominent erosional unconformities in the Odele Member, a lower one after the WAVT deposition with a modeled 95.4% C.I. range of 124–97 ka; and an upper one involving widespread alluvial fan incision commencing between 21.7 and 12.9 ka. The uppermost Odele Member also contains black, organic-rich mats, redox features, reed casts, and freshwater gastropods marking wetter conditions during the terminal Pleistocene and Early Holocene. A black, fine-grained relict soil coeval with the Halalalee paleosol bounds the top of the Odele Member and has mollic and vertic properties, weathering since ∼12 ka. These incision events and prominent paleosol development near/at the top of the Busidima Formation document Middle to Late Pleistocene Awash River incision to its present-day course. Paleo-rainfall estimates suggest that the Early Holocene-age Halalalee paleosol weathered under a climate with mean annual rainfall 10–15% higher than today. A compilation of radiocarbon ages from aquatic gastropods, carbonized wood and charcoal from the upper Odele Member shows wetter and possibly more vegetated conditions during late marine isotope stage (MIS) 3 and the African Humid Period (AHP) that are tightly coupled with precession-driven summer insolation maxima. These key findings suggest that periods of incision, aggregation, and landscape stability in the Odele Member have an orbital precession pacing. The Odele Member revises upward the age of the Busidima Formation to 7 ka, showing that it spans into the Holocene and now includes Middle and Later Stone Age archaeological traditions.
ISSN: 0277-3791
DOI: 10.1016/j.quascirev.2023.108083
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Type: Article
Appears in Collections:Arqueología
Datación por Resonancia Paramagnética Electrónica
Geocronología y Geología

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