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Geochronology Advances in geochronological science
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https://doi.org/10.5194/gchron-2019-18
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2019-18
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 Jan 2020

Submitted as: research article | 20 Jan 2020

Review status
A revised version of this preprint is currently under review for the journal GChron.

Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Lake Chatyr Kol (Kyrgyz Republic)

Julia Kalanke1, Jens Mingram1, Stefan Lauterbach2, Ryskul Usubaliev3, and Achim Brauer1,4 Julia Kalanke et al.
  • 1GFZ German Research Centre for Geosciences, Section 'Climate Dynamics and Landscape Evolution', Potsdam, Germany
  • 2University of Kiel, Leibniz Laboratory for Radiometric Dating and Stable Isotope Research, Kiel, Germany
  • 3Central Asian Institute for Applied Geoscience, Bishkek, Kyrgyzstan
  • 4University of Potsdam, Institute of Geoscience, Potsdam, Germany

Abstract. A finely laminated lake sediment record with a basal age of 11,619 ± 603 years BP was retrieved from Lake Chatyr Kol (Kyrgyz Republic). Microfacies analysis reveals the presence of seasonal laminae (varves) from the sediment basis to ~ 360 ± 40 years BP. The Chatvd19 floating varve chronology covers the time span from 360 ± 40 years BP to the base and relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ± 5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs γ-spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed uncertainty of 10 %. Six varve types were distinguished, are described in detail and show a changing predominance of clastic-organic, clastic-calcitic or -aragonitic, calcitic-clastic, organic-clastic and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to 1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to 2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains and Ruppia maritima seeds reveal reservoir ages with a clear decreasing trend up core from ~ 6,150 years in the early Holocene, to ~ 3,000 years in the mid-Holocene, to ~ 1,000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

Julia Kalanke et al.

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Julia Kalanke et al.

Julia Kalanke et al.

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Latest update: 01 Apr 2020
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Short summary
Our study presents the first seasonally laminated (varved) sediment record covering almost the entire Holocene in high-mountainous arid Central Asia. The established floating varve chronology is confirmed by two terrestrial radiocarbon dates, whereby aquatic radiocarbon dates reveal decreasing reservoir ages up core. Changes in seasonal deposition characteristics are attributed to changes in runoff and precipitation and/or to evaporative summer conditions.
Our study presents the first seasonally laminated (varved) sediment record covering almost the...
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