Abstract
Abstract. Arctic paleoenvironmental archives serve as sensitive recorders of past climate change. Lake El'gygytgyn (Far East Russian Arctic) is a high-latitude crater impact lake that contains a continuous sediment record influenced by neither glaciation nor glacial erosion since the time of impact 3.58 Ma ago. Prior research on sediments collected from Lake El'gygytgyn suggest times of permanent ice cover and anoxia corresponding to global glacial intervals, during which the sediments are laminated and are characterized by the co-occurrence of high total organic carbon, microscopic magnetite grains that show etching and dissolution, and negative excursions in bulk sediment organic matter carbon isotope (δ13C) values. Here we investigate the abundance and carbon isotopic composition of lipid biomarkers recovered from Lake El'gygytgyn sediments spanning marine isotope stages 1–3 to identify key sources of organic matter (OM) to lake sediments, to establish which OM sources drive the negative δ13C excursion exhibited by bulk sediment OM, and to explore if there are molecular and isotopic signatures of anoxia in the lake during glaciation. We find that during marine isotope stages 1–3, direct evidence for water column anoxia is lacking. A ~4‰ negative excursion in bulk sediment δ13C values during the Local Last Glacial Maximum (LLGM) is accompanied by more protracted, higher magnitude negative excursions in n-alkanoic acid and n-alkanol δ13C values that begin 20 kyr in advance of the LLGM. In contrast, n-alkanes and the C30 n-alkanoic acid do not exhibit a negative δ13C excursion at this time. Our results indicate that the C24, C26 and C28 n-alkanoic acids do not derive entirely from terrestrial OM sources, while the C30 n-alkanoic acid at Lake El'gygytgyn is a robust indicator of terrestrial OM contributions. Overall, our results strongly support the presence of a nutrient-poor water column, which is mostly isolated from atmospheric carbon dioxide during glaciation at Lake El'gygytgyn.
Highlights
Arctic lakes provide evidence of climate-sensitive environmental changes in terrestrial and aquatic ecosystems through accumulated sediment, which partially documents conditions of life and erosion within theSlaokleidbasEina. rAtrhctic regions are important recorders of past climate because summer temperatures in these regions hover near freezing
total organic carbon (TOC) concentrations in LZ1029 are similar to those reported for core PG1351 (Melles et al, 2007) throughout much of the record from modern through marine isotope stages (MIS) 3, with highest TOC concentrations found in a narrow range of sediments corresponding to the Local Last Glacial Maximum (LLGM)
Our results indicate that terrestrial organic matter (OM) is the main OM source to Lake El’gygytgyn throughout the past ∼ 60 kyr, which is consistent with the continuous accumulation of pollen in Lake El’gygytgyn sediments throughout this record (Lozhkin et al, 2007) and similar to findings from other Siberian lakes (Ouellette, 2003; Rodgers, 2005)
Summary
Arctic lakes provide evidence of climate-sensitive environmental changes in terrestrial and aquatic ecosystems through accumulated sediment, which partially documents conditions of life and erosion within theSlaokleidbasEina. rAtrhctic regions are important recorders of past climate because summer temperatures in these regions hover near freezing. Arctic lakes provide evidence of climate-sensitive environmental changes in terrestrial and aquatic ecosystems through accumulated sediment, which partially documents conditions of life and erosion within theSlaokleidbasEina. Lake El’gygytgyn (67◦30 N, 172◦05 E; Fig. 1) is a 12-kmwide, 175-m-deep craTtehr iempCacrt ylaokesdpathedetroe3.58 ± 0.04 Ma (Layer, 2000) that contains a continuous record of sedimentation (Brigham-Grette et al, 2007; Gebhardt et al, 2006). Like much of Beringia, the crater and surrounding region have not been glaciated or subject to glacial erosion since impact (Brigham-Grette et al, 2004). Unlike many Arctic lakes that contain discontinuous, glacially disturbed sediment archives, Lake El’gygytgyn provides a long-term, continuous record of climate and ecosystem change in the high Arctic from Pliocene to the present. Prior to deep drilling in 2009, several short pilot cores were collected to gain initial insights into
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