EGU2020-7304, updated on 10 Jan 2022
EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Revisiting Lake Garba Guracha, high altitude lake in the Bale Mountains, Ethiopia: reconstructing Late Glacial – Holocene lake level history using δ2H/δ18O biomarker analyses

Lucas Bittner1,2, Marcel Bliedtner3, Dai Grady4, Graciela Gil-Romera5,6, Catherine Martin-Jones7,8, Bruk Lemma2, Henry F. Lamb4, Cindy De Jonge9, Hanno Meyer10, Bruno Glaser2, and Michael Zech1
Lucas Bittner et al.
  • 1Heisenberg Chair of Physical Geography with focus on paleoenvironmental research, Institute of Geography, Technical University of Dresden, Dresden, Germany (
  • 2Institute of Agronomy and Nutritional Sciences, Soil Biogeochemistry, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany
  • 3Department of Physical Geography, Institute of Geography, Friedrich-Schiller-University Jena, Jena, Germany
  • 4Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK
  • 5Department of Ecology, Philipps-Marburg University, Marburg, Germany
  • 6Department of Geo-environmental Processes and Global Change, Pyrenean Institute of Ecology, CSIC, Zaragoza, Spain
  • 7Department of Geography, University of Cambridge, Cambridge CB2 3EN, UK
  • 8Limnology Unit, Department of Biology, Ghent University, B-9000 Gent, Belgium
  • 9Geological Institute, Department of Earth Sciences, ETH Swiss Federal Institute of Technology, 8092 Zurich, Switzerland
  • 10Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany

Our knowledge of East African paleoclimate is largely based on marine core and paleolimnological reconstructions. Accordingly, more humid climatic conditions such as the African Humid Period (AHP) are usually associated with summer insolation-driven increased monsoonal precipitation and the movement of the Congo Air Boundary.

In order to contribute to this discussion and to reconstruct the paleoclimate of the afro-alpine Bale Mountains, Ethiopia, within the DFG Research Unit 2358 ‘The Mountain Exile Hypothesis: How humans benefited from and re-shaped African high-altitude ecosystems during Quaternary climate changes’ we re-cored Lake Garba Guracha. This site represents one of the best dated Late Glacial - Holocene continuous, high altitude (3950 m asl) paleoenvironmental archives in East Africa.
We investigated sugar and lipid biomarkers and their compound-specific stable oxygen and hydrogen isotopic composition (δ18Osugar and δ2Hn-alkane) to infer past hydrological patterns. The δ18Osugar record reflects lake water and can thus be used to reconstruct lake evaporation history.

Our results suggest that a virtually permanent lake overflow existed from about 10 to 7 cal. ka BP, whereas the period from about 7 to 5 cal. ka BP is characterised by increased lake evaporation. We present initial results of δ18Odiatom analyses and organic geochemical and XRF data that document dominant minerogenic input during the Late Glacial and increased input of almost exclusively aquatic organic matter from 11 cal. ka BP on. Reconstructed mean annual temperatures (n=20, -2.2 to 2.5°C), inferred from brGDGT-based proxies, indicate that colder conditions prevailed in the high-altitude Bale Mountain ecosystem during the Younger Dryas.

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