Geochronology and glass geochemistry of major pleistocene eruptions in the Main Ethiopian Rift: Towards a regional tephrostratigraphy

Céline M. Vidal, Karen Fontijn, Christine S. Lane, Asfawossen Asrat, Dan Barfod, Emma L. Tomlinson, Alma Piermattei, William Hutchison, Amdemichael Zafu Tadesse, Gezahegn Yirgu, Alan Deino, Yves Moussallam, Paul Mohr, Frances Williams, Tamsin A. Mather, David M. Pyle, Clive Oppenheimer

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

The Main Ethiopian Rift (MER) is renowned as a focus of investigations into human origins. It is also the site of many large volcanic calderas, whose eruptions have spanned the timeframe of speciation, cultural innovation, and dispersal of our species. Yet, despite their significance for dating human fossils and cultural materials, the timing and geochemical signatures of some of the largest eruptions have remained poorly constrained at best. Here, through a programme of field surveys, geochemical analysis and 40Ar/39Ar dating, we report the ages of MER ignimbrites and link them to widespread tephra layers found in sequences of archaeological and paleoenvironmental significance. We date major eruptions of Fentale (76 ± 18 ka), Shala (ca. 145–155 ka), Kone (184 ± 42 ka and ca. 200 ± 12 ka) and Gedemsa (251 ± 47 ka) volcanoes, and correlate a suite of regionally important tephra horizons. Geochemical analysis highlights the predominantly peralkaline rhyolitic melt compositions (7.5–12 wt% Na2O + K2O, 70–76 wt% SiO2) across the central MER and remarkable similarity in incompatible trace element ratios, limiting the correlation of deposits via glass composition alone. However, by integrating stratigraphic and geochronological evidence from proximal deposits, lake sediment cores and distal outcrops at archaeological sites, we have traced ash layers associated with the ca. 177 ka Corbetti, ca. 145–155 ka Shala and ca. 108 ka Bora-Baricha-Tullu-Moye eruptions across southern Ethiopia. In addition to strengthening the tephrochronological framework that supports paleoenvironmental and archaeological work in the region, our findings have wider implications for evaluating the hypothesis of a middle Pleistocene ‘ignimbrite flare-up’ in the MER, and for evaluating the impacts of these great eruptions on landscapes, hydrology, and human ecology.

Original languageEnglish (US)
Article number107601
JournalQuaternary Science Reviews
Volume290
DOIs
StatePublished - Aug 15 2022

Bibliographical note

Funding Information:
This study was supported by the Leverhulme Trust grant 2016–21 (Nature and impacts of Middle Pleistocene volcanism in the Ethiopian Rift). KF was supported by the UK's Natural Environment Research Council (NERC) grant NE/L013932/1 (RiftVolc: The Past, Present and Future of Rift Volcanism in the Main Ethiopian Rift), a Boise Fund grant from the Department of Zoology, University of Oxford , and acknowledges Fonds de Recherche Scientifique – FNRS MIS grant F.4515.20 . Tephra work on the Chew Bahir cores in the Cambridge Tephra Lab by AA, AP and CL was made possible by NERC grant NE/K014560/1 and we acknowledge Prof Henry Lamb, Prof Frank Schaebitz, Prof Andy Cohen, Prof Martin Trauth and Dr Verena Foerster who, with AA, retrieved and facilitated access to the Chew Bahir core. The sample material from Chew Bahir core used in this project was provided by the National Lacustrine Core Facility (LacCore) where the cores are archived. We further thank Dr Victoria Cullen and Dr Victoria Smith for assistance with tephra analyses and Prof Henry Lamb, Prof Frank Schaebitz and Dr Verena Foerster for assistance with fieldwork at Konso. Ar–Ar dating was supported by grants NIGFSC IP-1683-1116 and IP-1680-1116. The iCRAG lab is supported by SFI 13/RC/2092. We acknowledge the local and regional authorities in Ethiopia for facilitating fieldwork, and the School of Earth Sciences of Addis Ababa University for facilitating sample export. We are very grateful for the professional logistical support provided by Ethioder and their drivers, and for field assistance by Alex in Omo-Kibish, Demelash in Konso, and Keri McNamara, Ermias Filfilu Gebru and Firawalin Dessalegn across the MER. We also thank Dr Iris Buisman and Dr Jason Day from the Department of Earth Sciences of the University of Cambridge for their help and support with sample preparation and microprobe analyses.

Funding Information:
This study was supported by the Leverhulme Trust grant 2016–21 (Nature and impacts of Middle Pleistocene volcanism in the Ethiopian Rift). KF was supported by the UK's Natural Environment Research Council (NERC) grant NE/L013932/1 (RiftVolc: The Past, Present and Future of Rift Volcanism in the Main Ethiopian Rift), a Boise Fund grant from the Department of Zoology, University of Oxford, and acknowledges Fonds de Recherche Scientifique – FNRS MIS grant F.4515.20. Tephra work on the Chew Bahir cores in the Cambridge Tephra Lab by AA, AP and CL was made possible by NERC grant NE/K014560/1 and we acknowledge Prof Henry Lamb, Prof Frank Schaebitz, Prof Andy Cohen, Prof Martin Trauth and Dr Verena Foerster who, with AA, retrieved and facilitated access to the Chew Bahir core. The sample material from Chew Bahir core used in this project was provided by the National Lacustrine Core Facility (LacCore) where the cores are archived. We further thank Dr Victoria Cullen and Dr Victoria Smith for assistance with tephra analyses and Prof Henry Lamb, Prof Frank Schaebitz and Dr Verena Foerster for assistance with fieldwork at Konso. Ar–Ar dating was supported by grants NIGFSC IP-1683-1116 and IP-1680-1116. The iCRAG lab is supported by SFI 13/RC/2092. We acknowledge the local and regional authorities in Ethiopia for facilitating fieldwork, and the School of Earth Sciences of Addis Ababa University for facilitating sample export. We are very grateful for the professional logistical support provided by Ethioder and their drivers, and for field assistance by Alex in Omo-Kibish, Demelash in Konso, and Keri McNamara, Ermias Filfilu Gebru and Firawalin Dessalegn across the MER. We also thank Dr Iris Buisman and Dr Jason Day from the Department of Earth Sciences of the University of Cambridge for their help and support with sample preparation and microprobe analyses.

Publisher Copyright:
© 2022 The Authors

Keywords

  • Caldera-forming eruption
  • East African Rift
  • Explosive volcanism
  • Ignimbrite
  • Late quaternary
  • Pleistocene
  • Tephrochronology
  • Tephrostratigraphy

Continental Scientific Drilling Facility tags

  • HSPDP-CHB

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