T214 Lakes of the World Through Time and Space — Archives of Climate, Paleoenvironments, Ecosystems, Geohazards, and Economic Resources

Tuesday, 24 September 2024
1:30 PM - 5:30 PM
213B

A LATE GLACIAL AND HOLOCENE PALEOCLIMATE RECORD FROM AFRICA’S LARGEST AFRO ALPINE ECOSYSTEM: BALE MOUNTAINS SOUTH EASTERN ETHIOPIA

Paper number: T214-4
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Understanding past climate variabilities and their influence on hydrological dynamics is paramount in successfully forecasting and mitigating future climate challenges. Afro alpine ecosystems offer pristine climate archives mainly due to their remoteness from modern anthropogenic influences. The Bale Mountains of the Southeastern Ethiopian Highlands are the largest and most contagious afro-alpine ecosystem in Africa. The mountain ranges are close to the East African Rift, home to a number of early hominin sites. The juxtaposition of rift and alpine systems and complex climate dynamics offers a unique perspective on understanding pre-industrial climate-human interaction.

During a 2017 field campaign, we retrieved a 4.8-meter core from the Central Lake (4020 meters above sea level) in the Bale Mountains. Using 12 radiocarbon dates, we reconstructed a 17 thousand-year sedimentary history. Here, we present the preliminary findings of our multi-proxy investigation on this archive. We conducted compound specific stable isotope analysis on sugar and lipid biomarkers (δ18Osugar and δ2Hn-alkane) to infer the past hydrological history. We also analyzed branched glycerol dialkyl glycerol tetraether (brGDGT) lipids to reconstruct changes in temperature and lake water chemistry.

Despite the difference in the source (sugar biomarker primarily autochthonous and n-alkane biomarkers primarily allochthonous), both stable isotope records show a similar pattern, which suggests the common climatic influence. BrGDGT-based temperature reconstructions indicate a temperature shift from late Glacial to Holocene (average MAAT 3.8 to 9 0C,respectively) that largely resembles orbital forced summer insolation. Comparison with neighboring low-altitude terrestrial and marine climate archives show similar responses to major climatic phases such as the Younger Drays and the African Humid Period, suggesting climatic teleconnection.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-400499

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