Abstract
Abstract. Microfacies analysis of a sediment record from Chatyr Kol lake (Kyrgyz Republic) reveals the presence of seasonal laminae (varves) from the sediment base dated at 11 619±603 BP (years Before Present) up to ∼360±40 BP. The Chatvd19 floating varve chronology 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 gamma spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed maximum uncertainty of 10 %. Six varve types were distinguished, are described in detail, and show a changing predominance of clastic-organic, clastic-calcitic or clastic-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 reveals reservoir ages with a clear decreasing trend up core from ∼6150 years in the early Holocene, to ∼3000 years in the mid-Holocene, to ∼1000 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.
Highlights
The interplay of the large atmospheric circulation systems in Central Asia (CA), including the Siberian High, the westerlies, and the Indian Monsoon, and their influences on regional climate are still not fully understood
We present the first varved lake sediment record in arid Central Asia that covers almost the entire Holocene
The established floating varve chronology provides independent dating for a setting with scarce material for radiocarbon dating
Summary
The interplay of the large atmospheric circulation systems in Central Asia (CA), including the Siberian High, the westerlies, and the Indian Monsoon, and their influences on regional climate are still not fully understood. Information about Holocene climate variability in CA derives from several types of archives, including tree rings (Esper et al, 2003), speleothems (Fohlmeister et al, 2017; Wolff et al, 2017), ice cores (Aizen, 2004), aeolian deposits (Huayu et al, 2010), and lakes (Heinecke et al, 2017; Lauterbach et al, 2014; Mathis et al, 2014; Rasmussen et al, 2000; Ricketts et al, 2001; Schwarz et al, 2017) None of these lake records have reported annually laminated sediments. Deciphering Holocene climate changes based on limnic records in CA is challenging due to the influences of several factors: (1) chronological uncertainties caused by the scarcity of datable terrestrial plant material at high alti-
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