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

Published version
Peer-reviewed

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Authors

Bliedtner, M 
Grady, D 
Gil-Romera, G 
Martin-Jones, C 

Abstract

jats:titleAbstract</jats:title>jats:pPrevious 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 jats:sup210</jats:sup>Pb dating and radiocarbon dating of bulk sedimentary organic matter, bulk jats:italicn</jats:italic>-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 jats:italicn</jats:italic>-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 jats:italicn</jats:italic>-alkane-based Pjats:subaq</jats:sub> proxy, TOC/N ratios, δjats:sup13</jats:sup>C 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.</jats:p>

Description

Keywords

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

Journal Title

Journal of Paleolimnology

Conference Name

Journal ISSN

0921-2728
1573-0417

Volume Title

64

Publisher

Springer Science and Business Media LLC
Sponsorship
Deutsche Forschungsgemeinschaft (DFG ZE 844/10-1)