A Late Holocene δ18O paleoclimate record from the afro-alpine Lake Garba Guracha, Bale Mountains Ethiopia: implications for human occupation/abandonment

Abstract

The Late Holocene, being a period when human footprint in paleoenvironmental archives became increasingly apparent, records important information about how early humans adapted to ever changing climatic conditions. Garba Guracha is an afro-alpine cirque lake located in the Bale Mountains National Park in the southeastern highlands of Ethiopia. The reconstructed age depth model with a time resolution of 10 years/cm makes it one of the best climate archives in the highlands of Eastern Africa. A total of 15.5 meter core recording 16 ka of sedimentation was retrieved from the lake. Previous works done on the archive include: (i) establishing the age-depth model and determination of sedimentation rates using bulk sedimentary organic matter, bulk n-alkane and charcoal 14C ages (Bittner et al. 2020); (ii) multi-proxy paleoenvironment reconstruction using charcoal, diatoms, biomarkers, and stable isotopes (Bittner et al., 2022; Gil-Romera et al., 2019). Results from these works show a strong variability for the late Holocene that represents the termination of the African Humid Period (AHP) and increased fire intensity. This study focuses on the topmost sedimentary succession of the core representing the late Holocene (~5 ka to present) and implements δ18Osugar extracted from organic matter derived sugar biomarkers in high resolution (every 4 cm). The δ18Osugar record can be used for reconstructing the lake evaporation history. Furthermore, combing these new data with other data obtained from n-alkane, charcoal and archaeological studies will shade light on a possible climate human interactions in high alpine ecosystem.ReferencesBittner, L., Bliedtner, M., Grady, D., Gil-Romera, G., Martin-Jones, C., Lemma, B., Mekonnen, B., et al., 2020. Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications. Journal of Paleolimnology 64, 293–314.Bittner, L., Gil-Romera, G., Grady, D., Lamb, H., Lorenz, E., Weiner, M., Zech, M. (2022). The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms. Quaternary Research, 105, 23-36.Gil-Romera, G., Adolf, C., Benito Blas, M., Bittner, L., Johansson, M.M.U., Grady, D.D.A., Lamb, H.H.F., et al., 2019. Long-term fire resilience of the Ericaceous Belt, Bale Mountains, Ethiopia. Biology Letters 15, 20190357.