Abstract
Abstract. Geochemical analyses were performed on sediments recovered by deep drilling at Lake El'gygytgyn in central Chukotka, northeastern Russia (67°30' N; 172°05' E). Major and rare element concentrations were determined using X-ray fluorescence spectroscopy (XRF) on the < 250 μm fraction from 617 samples dated to ca. 440 and 125 ka, which approximates marine isotope stages (MIS) 11 to 6. The inorganic geochemistry indicates significant variations in elemental composition between glaciations and interglaciations. Interglacial sediments are characterized by high contents of SiO2, Na2O, CaO, K2O, and Sr and are depleted in Al2O3, Fe2O3, TiO2, and MgO. An extreme SiO2 enrichment during MIS 11.3 and 9.3 was caused by an enhanced flux of biogenic silica (BSi). The geochemical structure of MIS 11 shows similar characteristics as seen in MIS 11 records from Lake Baikal (southeastern Siberia) and Antarctic ice cores, thereby arguing for the influence of global forcings on these records. High sediment content of TiO2, Fe2O3, MgO, Al2O3, LOI, Ni, Cr, and Zr typifies glacial stages, with the most marked increases during MIS 7.4 and 6.6. Reducing conditions during glacial times are indicated by peaks in the Fe2O3 content and coinciding low Fe2O3/MnO ratios. This conclusion also is supported by P2O5 and MnO enrichment, indicating an increased abundance of authigenic, fine-grained vivianite. Elemental ratios (CIA, CIW, PIA, and Rb/Sr) indicate that glacial sediments are depleted in mobile elements, like Na, Ca, K and Sr. This depletion was caused by changes in the sedimentation regime and thus reflects environmental changes.
Highlights
Lake El’gygytgyn (67◦30 N, 172◦05 E) was drilled to recover 318 m of lacustrine sediment, providing the first continuous record of past climate change in the terrestrial Arctic spanning the last 3.6 Ma (Melles et al, 2011, 2012; BrighamGrette et al, 2013; Nowaczyk et al, 2013)
The geochemical characteristics of lacustrine sediments depend on many factors, including the (1) chemical composition of the provenance; (2) physical and chemical weathering processes in the catchment; (3) tectonic and eolian activity; (4) sorting during sediment transport and sedimentation; and (5) post-depositional diagenetic changes (e.g., Fralick and Kronberg, 1997)
The second PC axis explains an additional 24 % of the variability and is characterized by positive loadings of Ba, K, Rb, Zr, Na2O, CaO, magnetic susceptibility (MS), and Sr. It is negatively correlated with P2O5, MnO, and loss on ignition (LOI). These results indicate the presence of three main data groups
Summary
Lake El’gygytgyn (67◦30 N, 172◦05 E) was drilled to recover 318 m of lacustrine sediment, providing the first continuous record of past climate change in the terrestrial Arctic spanning the last 3.6 Ma (Melles et al, 2011, 2012; BrighamGrette et al, 2013; Nowaczyk et al, 2013). We focus on the geochemical characterization of sediments from the upper part of ICDP core 5011-1, spanning MIS 6 to MIS 11. This interval encompasses great climatic variations from the maximum temperatures of the “super” interglacials (MIS 11 and MIS 9) to the extreme cold of MIS 6 and MIS 8 (Melles et al, 2012; Matrosova, 2009; Lozhkin et al, 2013)
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