Pliocene to Pleistocene climate and environmental history of Lake El'gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data

Abstract

The 3.6 Ma sediment record of Lake El'gygytgyn, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition monitored by X-ray fluorescence scanning exhibits significant changes since the Mid-Pliocene caused by climate driven variations in the primary production, postsedimentary diagenetic processes, and current activity in the lake as well as weathering processes in its catchment. <br><br> During the Mid to Late Pliocene, warmer and wetter climatic conditions are reflected by elevated Si / Ti ratios, indicating enhanced diatom production in the lake. Prior to 3.3 Ma, this signal is highly masked by intensified detrital input from the catchment, visible in maxima of clastic-related proxies such as the K concentration. In addition, calcite formation in the early lake history points to enhanced nutrient flux into the lake caused by intensified weathering in its catchment. Its termination at ca. 3.3 Ma is supposed to be linked to the development of permafrost in the region triggered by a first cooling in the Mid-Pliocene. <br><br> After ca. 3.0 Ma the elemental data suggest a gradual transition to Quaternary-style glacial / interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 ka obliquity band but experienced a change to a 100 ka eccentricity dominance after the Middle Pleistocene Transition at ca. 1.2 to 0.7 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. <br><br> A successive decrease of the baseline-levels of the redox-sensitive Mn / Fe ratio and magnetic susceptibility between 2.3 to 1.8 Ma reflects an overall change in the bottom water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Quaternary. The coincidence with major changes in the North Pacific and Bering Sea paleoceanography at ca. 1.8 Ma implies that the change in lake hydrology was caused by regional cooling and/or changes in the ocean-land moisture transport. Further rising TOC and TN values after ca. 1.6 Ma are attributed to a progressive intensification of the glacial intensity. <br><br> In the course of the Quaternary glacial/interglacial sequence eight so-called "super-interglacials" occur. Their exceptional warm conditions are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating an extraordinary high lake productivity

Detailed insight into Arctic climatic variability during MIS 11c at Lake El'gygytgyn, NE Russia

“…XRF scanning was performed at 2 mm resolution using an integration time of 10 s per measurement. Details of the scanning and data correction are given in Melles et al (2012) and Wennrich et al (2013). For a better comprehensibility, in the following, the Mn/Fe ratio is presented as the ratio of Mn to Fe integrals multiplied by a factor of 1000.…”

Mass movement deposits in the 3.6 Ma sediment record of Lake El'gygytgyn, Far East Russian Arctic

“…Subsequently the elemental composition was measured and radiographs were obtained on the core halves with an ITRAX core scanner (Cox Analytics) in resolutions of 2 mm and 200 µm, respectively, and gamma-ray density measurements were performed at Alfred Wegener Institute in Bremerhaven, Germany, with an MSCL core logger (Geotek Ltd.). For a more detailed description of the drilling operations and core processing, see Melles et al (2011Melles et al ( , 2012, Francke et al (2013), Gebhardt et al (2013) or Wennrich et al (2013b).…”

“…Additionally, the internal structure of the majority of the turbidites does not suggest formation by hyperpycnal flows, where the deposit would have a basal coarsening upward unit overlain by a fining upward unit (Mulder et al, 2003). In the deep lake basin, the accumulated sediments are fine grained Wennrich et al, 2013a), suggesting that the coarser grained mass movements, in particular debrites, but also grain flows and turbidites, originate from shallow water depths, where such sediments are found (Juschus et al, 2011). The large alluvial fan and its subaqueous prologation in the western and northern lake catchment provide coarser grained sediments into the lake basin (Schwamborn et al, 2012;Fedorov et al, 2013) and delta collapses account for some of the mass movements encountered at the lake center.…”

Modern sedimentation patterns in Lake El'gygytgyn, NE Russia, derived from surface sediment and inlet streams samples

“…1) and pilot core PG1351 in the central part of Lake El'gygytgyn, Ti, Fe 2 O 3 , but also Cr and Ni typically are enriched during cold stages Wennrich et al, 2013). Such sediments are usually characterized by low coarse silt to fine sand but higher clay and fine silt contents .…”

“…K, Na, or Sr) might be used in sediment cores of Lake El'gygytgyn as indicators for coarser grain sizes (e.g. Wennrich et al, 2013).…”