Climatic and environmental changes in the Yana Highlands of north‐eastern Siberia over the last c. 57 000 years, derived from a sediment core from Lake Emanda

Abstract

The sediment succession of Lake Emanda in the Yana Highlands was investigated to reconstruct the regional late Quaternary climate and environmental history. Hydro‐acoustic data obtained during a field campaign in 2017 show laminated sediments in the north‐western and deepest (up to ̃15 m) part of the lake, where a ̃6‐m‐long sediment core (Co1412) was retrieved. The sediment core was studied with a multi‐proxy approach including sedimentological and geochemical analyses. The chronology of Co1412 is based on 14C AMS dating on plant fragments from the upper 4.65 m and by extrapolation suggests a basal age of c. 57 cal. ka BP. Pronounced changes in the proxy data indicate that early Marine Isotope Stage (MIS) 3 was characterized by unstable environmental conditions associated with short‐term temperature and/or precipitation variations. This interval was followed by progressively colder and likely drier conditions during mid‐MIS 3. A lake‐level decline between 32.0 and 19.1 cal. ka BP was presumably related to increased continentality and dry conditions peaking during the Last Glacial Maximum (LGM). A subsequent rise in lake level could accordingly have been the result of increased rainfall, probably in combination with seasonally high meltwater input. A milder or wetter Lateglacial climate increased lake productivity and vegetation growth, the latter stabilizing the catchment and reducing clastic input into the lake. The Bølling‐Allerød warming, Younger Dryas cooling and Holocene Thermal Maximum (HTM) are indicated by distinct changes in the environment around Lake Emanda. Unstable, but similar‐to‐present‐day climatic and environmental conditions have persisted since c. 5 cal. ka BP. The results emphasize the highly continental setting of the study site and therefore suggest that the climate at Lake Emanda was predominantly controlled by changes in summer insolation, global sea level, and the extent of ice sheets over Eurasia, which influenced atmospheric circulation patterns.

Comment on bg-2021-39

“…The timing of this phase agrees well with the timing of warm and humid environments interpreted during the early Holocene recorded at Lake Emanda, central Yakutia (11.5-9.0 cal. ka BP) and coincides with the maximum in local solar insolation (Baumer et al, 2020;Berger & Loutre 1991). Moreover, this finding is consistent with palynological 540 records from Lake Ilirney and from a Holocene short core from Lake Rauchuagytgyn which show evidence for a Holocene thermal maximum ca.…”

“…This is supported by low pollen concentrations recorded within the Lake Ilirney pollen record and the persistence of Poaceae and Artemisia during the late glacial that 510 signify persistently cold conditions and low catchment pollen productivity (Andreev et al, accepted). Based on the similarities between the lakes and their catchments, their proximity, and a lack of macrophytes at both sites, a similar interpretation can be postulated for Lake Rauchuagytgyn (Sifeddine et al, 2011 interface that could have enhanced degradation of organic matter (Baumer et al, 2020;Fritz et al, 2018). This 515 could be indicative of a gradually increasing summer open water season with more intensive mixing of the water column through wind and also through enhanced fluvial inflow during progressive late glacial climate amelioration (Baumer et al, 2020).…”

“…Organic material arriving at the sedimentwater interface was likely preserved by low oxygen conditions. This is recorded by low and stable values of the XRF-derived Mn/Fe ratio that well represents the redox conditions at the sediment-water interface (Baumer et al, 2020;Biskaborn et al, 2019;Fritz et al, 2018;Heinecke et al, 2017;Naeher et al, 2013).…”

“…of K/Ti is used as proxy for clay input and weathering (Arnaud et al, 2012;Cuven et al, 2010;Kilian et al, 2013;Marshall et al, 2011). Zr/K is used as a grain-size proxy and Mn/Fe for redox conditions (Baumer et al, 2020;Cuven et al, 2010). Br/Al is utilized alongside Br as a proxy for productivity (Lenz et al, 2020).…”

“…ka BP. Low K/Ti values during the early Holocene that subsequently persist throughout the mid-late Holocene may reflect increased chemical relative to 535 physical weathering due to the leaching of K from clastic material entering the lake by enhanced catchment pedogenic processes that influenced OCAR values (Baumer et al, 2020;D´Arcy & Carignan, 1997). The timing of this phase agrees well with the timing of warm and humid environments interpreted during the early Holocene recorded at Lake Emanda, central Yakutia (11.5-9.0 cal.…”