NORTH-EASTERN SHARED RESEARCH FACILITIES OF NEISRI FEB RAS: EQUIPMENT AND DIRECTIONS OF RESEARCH

The activity of the North-Eastern Shared Research Facilities of the Shilo North-East Interdisciplinary Scientific Research Institute, Far Eastern Branch of the Russian Academy of Sciences (NEISRI FEB RAS) is aimed at conducting analytical studies of rocks, minerals, ores, soils, lake and sea sediments, water bodies using various methods: optical microscopy, X-ray microanalysis, X-ray fluorescence analysis, quantitative emission spectral analysis, atomic absorption spectrometry, isotope geochronology, paleomagnetism and petromagnetism. The results of mineralogical, geochemical, petrophysical, isotope-geochronological (including radiocarbon) and palynological studies have been published in national and international scientific journals

Pliocene to Pleistocene climate and environmental history of Lake El\u27gygytgyn, Far East Russian Arctic, based on high-resolution inorganic geochemistry data

The 3.6 Ma sediment record of Lake El\u27gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. 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 overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial-interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2-0.6 Ma. This clearly demonstrates the sensitivity of the Lake El\u27gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn / Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. 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 a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial-interglacial sequence eight so-called super-interglacials occur. Their exceptionally warm conditions are reflected by extreme Si / Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity

СЕВЕРО-ВОСТОЧНЫЙ ЦЕНТР КОЛЛЕКТИВНОГО ПОЛЬЗОВАНИЯ СВКНИИ ДВО РАН: АППАРАТУРА И НАПРАВЛЕНИЯ ИССЛЕДОВАНИЙ

The activity of the North-Eastern Shared Research Facilities of the Shilo North-East Interdisciplinary Scientific Research Institute, Far Eastern Branch of the Russian Academy of Sciences (NEISRI FEB RAS) is aimed at conducting analytical studies of rocks, minerals, ores, soils, lake and sea sediments, water bodies using various methods: optical microscopy, X-ray microanalysis, X-ray fluorescence analysis, quantitative emission spectral analysis, atomic absorption spectrometry, isotope geochronology, paleomagnetism and petromagnetism. The results of mineralogical, geochemical, petrophysical, isotope-geochronological (including radiocarbon) and palynological studies have been published in national and international scientific journals.Деятельность центра направлена на проведение аналитических исследований горных пород, минералов, руд, почв, озерных и морских осадков, водных объектов с использованием различных методов: оптической микроскопии, рентгеноспектрального микроанализа, рентгенофлюоресцентного анализа, эмиссионного количественного спектрального анализа, атомно-абсорбционной спектрометрии, изотопной геохронологии, палеомагнетизма и петромагнетизма. Полученные результаты минералого-геохимических, петрофизических, изотопно-геохронологических, радиоуглеродных и палинологических исследований опубликованы в отечественных и зарубежных научных журналах.

Inorganic geochemistry data from Lake El'gygytgyn sediments: marine isotope stages 6–11

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

High-temperature thermomagnetic properties of vivianite nodules, Lake El'gygytgyn, Northeast Russia

Vivianite, a hydrated iron phosphate, is abundant in sediments of Lake El'gygytgyn, located in the Anadyr Mountains of central Chukotka, northeastern Russia (67&deg;30&prime; N, 172&deg;05&prime; E). Magnetic measurements, including mass-specific low-field AC magnetic susceptibility, field-dependent magnetic susceptibility, hysteresis parameters, temperature dependence of the induced magnetization, as well as susceptibility in different heating media, provide ample information on vivianite nodules. Electron microprobe analyses, electron microscopy and energy dispersive spectroscopy were used to identify diagnostic minerals. Vivianite nodules are abundant in both sediments of cold (anoxic) and warm (oxic) stages. Magnetic susceptibility of the nodules varies from 0.78 × 10^&minus;6 m³ kg⁻¹ to 1.72 × 10^&minus;6 m³ kg⁻¹ (average = 1.05 × 10^&minus;6 m³ kg⁻¹) and is higher than the susceptibility of sediments from the cold intervals. Magnetic properties of vivianite are due to the respective product of oxidation as well as sediment and mineral inclusions. Three types of curves for high-temperature dependent susceptibility of vivianite indicate different degrees of oxidation and inclusions in the nodules. Vivianite acts as a reductant and reduces hematite to magnetite and masks the goethite–hematite transition during heating. Heating vivianite and sulfur mixtures stimulates the formation of monoclinic pyrrhotite. An additive of arsenic inhibits the formation of magnetite prior to its Curie temperature. Heating selective vivianite and pyrite mixtures leads to formation of several different minerals &ndash; magnetite, monoclinic pyrrhotite, and hexagonal pyrrhotite, and makes it difficult to interpret the thermomagnetic curves

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

The 3.6Ma sediment record of Lake El'gygytgyn/NE Russia, Far East Russian Arctic, represents the longest continuous climate archive of the terrestrial Arctic. Its elemental composition as determined by X-ray fluorescence scanning exhibits significant changes since the mid-Pliocene caused by climate-driven variations in primary production, postdepositional diagenetic processes, and lake circulation as well as weathering processes in its catchment. 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 overprinted by intensified detrital input from the catchment, visible in maxima of clastic-related proxies, such as K. In addition, calcite formation in the early lake history points to enhanced Ca flux into the lake caused by intensified weathering in the catchment. A lack of calcite deposition after ca. 3.3 Ma is linked to the development of permafrost in the region triggered by cooling in the mid-Pliocene. After ca. 3.0 Ma the elemental data suggest a gradual transition to Pleistocene-style glacial-interglacial cyclicity. In the early Pleistocene, the cyclicity was first dominated by variations on the 41 kyr obliquity band but experienced a change to a 100 kyr eccentricity dominance during the middle Pleistocene transition (MPT) at ca. 1.2-0.6 Ma. This clearly demonstrates the sensitivity of the Lake El'gygytgyn record to orbital forcing. A successive decrease of the baseline levels of the redox-sensitive Mn/Fe ratio and magnetic susceptibility between 2.3 and 1.8 Ma reflects an overall change in the bottom-water oxygenation due to an intensified occurrence of pervasive glacial episodes in the early Pleistocene. 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 a regional cooling in the North Pacific and the western Beringian landmass and/or changes in the continentality. Further increases in total organic carbon and total nitrogen content after ca. 1.6 Ma are attributed to reduced organic matter decay in the sediment during prolonged anoxic periods. This points to more extensive periods of perennial ice coverage, and thus, to a progressive shifts towards more intense peak glacial periods. In the course of the Pleistocene glacial-interglacial sequence eight so-called super-interglacials occur. Their exceptionally warm conditions are reflected by extreme Si/Ti peaks accompanied by lows in Ti, K, and Fe, thus indicating extraordinary high lake productivity