Magnetostratigraphic results from impact crater Lake El'gygytgyn, northeastern Siberia: a 300 kyr long high-resolution terrestrial palaeoclimatic record from the Arctic

Abstract

Summary A 12.7 m long sedimentary record recovered from Lake El'gygytgyn, located in a meteorite impact crater created 3.6 Ma in Late Cretaceous igneous rocks on Chukotka Peninsula, northeast Siberia, has been analysed for its palaeo‐ and rock‐magnetic properties. Continuous high resolution (1 mm) measurements of magnetic susceptibility yielded successions of pronounced lows and highs. Analyses of the rock‐magnetic properties by low and high temperature runs of magnetic susceptibility, determination of hysteresis parameters as well as IRM acquisition experiments, yielded a dominance of PSD (pseudo‐single domain) magnetite in intervals of high magnetic susceptibility, whereas, due to selective magnetite dissolution associated with anoxic Lake water and/or pore water conditions during times of enhanced deposition of organic matter, haematite dominates within low susceptibility intervals in terms of mass percentage. Here however, magnetic properties are still dominated by magnetite. Five AMS (accelerator mass spectromentry) 14C ages, eight IRSL (infrared stimulated luminescense) ages together with preliminary pollen data suggest that variations in magnetite content reflect climatic variability of the last ∼300 ka with low (high) susceptibilities representing cold (warm) climates. This pattern, caused by a complex system of deposition, preservation or decomposition of organic matter and/or magnetic minerals, in turn can be correlated in detail to global climate archives such as the oxygen isotope records from Greenland ice cores and marine sediments, respectively. Thus, the sedimentary sequence recovered from Lake El'gygytgyn represents the longest continuous terrestrial climate record now available from the Arctic.

Applying SAR-IRSL methodology for dating fine-grained sediments from Lake El’gygytgyn, north-eastern Siberia

“…2), recovered in 1998, was deduced from tuning regional insolation with magnetic susceptibility, biogenic silica, total organic carbon and TiO 2 values in the sediments (Nowaczyk et al, in press; Melles et al, in press). It is confirmed by pollen analyses, AMS radiocarbon and MAAD polymineral fine-grain IRSL dating (Nowaczyk et al, 2002;Nowaczyk et al, in press;Forman et al, in press).…”

A 350 ka record of climate change from Lake El'gygytgyn, Far East Russian Arctic: refining the pattern of climate modes by means of cluster analysis

“…Weathering of the rocks is largely controlled by the presence or absence of permafrost . Fluvial transport and sedimentation is limited to summer periods when air temperatures are above 0 • C and the ice cover on the lake is disintegrating (Nolan and Brigham-Grette, 2002). During expeditions in 1998 and 2003, designed as pilot studies for the ICDP-drilling of Lake El'gygytgyn, two long sediment cores, PG1351 and Lz1024, were recovered from the lake centre at a water depth of 175 m (Fig.…”

“…The sediment consists of alternations of brownish and greenish nonlaminated and laminated greyish silt and clay; including some turbidites with thicknesses of up to 45 cm (Juschus et al, 2009). Former investigations on core PG1351 (Nowaczyk et al, 2002Melles et al, 2007;Minyuk et al, 2007) revealed that anoxic and laminated conditions primarily occur during periods of perennial ice cover and oxic and nonlaminated conditions occur when open water controls mixing of the water body during summer times . In intervals with prevailing anoxic conditions reductive dissolution of magnetite was observed whereas organic matter is well preserved.…”

“…The magnetic susceptibility was measured on the split halves of the cores in 1 mm steps with a Bartington MS2E/1 spotreading sensor integrated in an automated core logging system (Nowaczyk et al, 2002). Magnetic susceptibility (κ LF ) of discrete samples (20 × 20 × 15 mm) was measured nearly continuously, taken along the z axis of the core halves with an AGICO kappabridge KLY-3S.…”

“…2), considering also OSL dating from core PG1351 (Nowaczyk et al, 2002Forman et al, 2007) and Lz1024 (Juschus et al, 2007). This method was also applied to the core composite from ICDP Site 5011-1 (Nowazcyk et al, 2013).…”