Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • L. Bittner - , Heisenberg Chair of Physical Geography with a Focus on Paleoenvironmental Research, Martin Luther University Halle-Wittenberg (Author)
  • M. Bliedtner - , Friedrich Schiller University Jena (Author)
  • D. Grady - , Aberystwyth University (Author)
  • G. Gil-Romera - , Aberystwyth University, Spanish National Research Council (CSIC) (Author)
  • C. Martin-Jones - , University of Cambridge, Ghent University (Author)
  • B. Lemma - , Martin Luther University Halle-Wittenberg (Author)
  • B. Mekonnen - , Martin Luther University Halle-Wittenberg, University of Bayreuth (Author)
  • H. F. Lamb - , Aberystwyth University (Author)
  • H. Yang - , University College London (Author)
  • B. Glaser - , Martin Luther University Halle-Wittenberg (Author)
  • S. Szidat - , University of Bern (Author)
  • G. Salazar - , University of Bern (Author)
  • N. L. Rose - , University College London (Author)
  • L. Opgenoorth - , University of Marburg (Author)
  • G. Miehe - , University of Marburg (Author)
  • W. Zech - , University of Bayreuth (Author)
  • M. Zech - , Heisenberg Chair of Physical Geography with a Focus on Paleoenvironmental Research (Author)

Abstract

Previous paleolimnological studies demonstrated that the sediments of Garba Guracha, situated at 3950 m asl in the afro-alpine zone of the Bale Mountains of Ethiopia, provide a complete Late Glacial and Holocene paleoclimate and environmental archive. We revisited Garba Guracha in order to retrieve new sediment cores and to apply new environmental proxies, e.g. charcoal, diatoms, biomarkers, and stable isotopes. Our chronology is established using 210Pb dating and radiocarbon dating of bulk sedimentary organic matter, bulk n-alkanes, and charcoal. Although bedrock was not reached during coring, basal ages confirm that sedimentation started at the earliest ~ 16 cal kyr BP. The absence of a systematic age offset for the n-alkanes suggests that “pre-aging” is not a prominent issue in this lake, which is characterised by a very small afro-alpine catchment. X-ray fluorescence scans and total organic carbon contents show a prominent transition from minerogenic to organic-rich sediments around 11 cal kyr BP coinciding with the Holocene onset. While an unambiguous terrestrial versus aquatic source identification seems challenging, the n-alkane-based Paq proxy, TOC/N ratios, δ13C values, and the sugar biomarker patterns suggest a predominantly autochthonous organic matter source. Supraregional climate events, such as the African Humid Period, the Younger Dryas (YD), a 6.5 cal kyr BP short drying event, and the 4.2 cal kyr BP transition to overall drier climate are recorded in our archive. The Garba Guracha record suggests that northern hemisphere forcings played a role in the Eastern African highland paleoclimate.

Details

Original languageEnglish
Pages (from-to)293-314
Number of pages22
JournalJournal of Paleolimnology
Volume64
Issue number3
Publication statusPublished - 1 Oct 2020
Peer-reviewedYes

External IDs

ORCID /0000-0002-9586-0390/work/170107066

Keywords

Keywords

  • Afro-alpine, Biomarkers, Paleolimnology, Radiocarbon dating, Sedimentation rate, XRF scanning

Library keywords