Ivan Kalugin

Reconstruction of annual air temperatures for three thousand years in Altai region by lithological and geochemical indicators in Teletskoe Lake sediments

Limnological studies show that the variation of climate conditions over the catchment area of the lake are reflected in the composition and structure of bottom sediments, allowing one to use the measurable physicochemical characteristics of the sediments for the reconstruction of paleoclimate conditions. The mountain lakes of Siberia were not subjected to any significant anthropogenic pollution over the last 100‐150 years, which is the period of instrumental measurements. Thus, the geochemical composition of the upper layers of the sediments may be correctly calibrated by present-day weather data. Teletskoe Lake is a suitable object for these studies because here, in recent years, a continuous sequence of bottom sediments was studied, the steady correlation of the sediment composition and properties to the weather survey data was established, the procedures of high-resolution analyses were elaborated, and the annual climate variations were reconstructed for the last 800 years [1, 2]. Bottom sediments in Teletskoe Lake are constituted by carbonate-free terrigenous silty clays of low content of allochthonous organic detritus (1.14% of the total carbon) and of biogenic silica (2.5%). The sediment formation represents the weather conditions well because the matter supply to the basin coincides in mass to its deposition for a year [2]. The column of bottom sediments 190 cm length was taken out in 2006 with a gravity tube from the isolated underwater Ridge of Sofia Lepneva, which reaches from the bottom of 200‐250 m depth to a depth of 90 m at the site of the 51°44.99 ′ N, 87°37.414 ′ E coordinates. In the same place, using a box corer, a block of undisturbed sediments 14 × 14 × 20 cm in dimensions was taken. The block upper layers were used to create the age model. As the input data for the reconstruction, we used the time series of lithological and geochemical parameters and annual temperatures for AD 1840‐1996 from the Barnaul weather station. The measurement points were converted into the time scale on the basis of the estimates of the sediment accumulation rate by isotope dating: the peak of the 137 Cs content related to 1963; the logarithmic distribution of 210 Pb to the depth of 48 mm; and the radiocarbon age of the reference layer was 1105. To calculate the mass (dry) rate, the correction for water content was applied using the values of X-ray density calibrated by the water of content. The obtained value of the average linear rate of dry matter accumulation equal to 0.30 mm per year was used to create the time scale. The composition and physical properties of the sediments were studied by common procedures with discrete sub-sampling of 0.5 cm, and the continuous sequences were analyzed at the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, by means of X-ray fluorescence using the synchrotron radiation. With the equipment and procedures from [1, 3], blocks of dimensions 170 × 15 × 7 mm were scanned in steps of 100 µ m. The concentrations of over 20 elements characterized by the terrigenous and organogenous components of the sediment were deter

Carotenoids of phototrophic organisms in bottom sediments of meromictic Lake Shira (Siberia, Russia) as an indicator of past stratification.

228 Photosynthetic pigments (chlorophylls and caro tenoids) buried in bottom sediments of water bodies are traces of phototrophic organisms that dwelled in these water bodies in the past [1–3]. In the course of sedimentation, the pigments come to bottom sedi ments from the photic zone together with dead cells, pallets of zooplankton, plant remnants, etc. and remain preserved during hundreds and thousands of years due to the absence of light and oxygen, and low temperatures [1]. Therefore, the profile and quantita tive composition of the pigments in the bottom sedi ment layers may serve as indicators of the species com position of the biomass and the amount of pho totrophic organism production in the corresponding periods of the history of the given water body. In turn, changes in the species composition and production characteristics are indicators of changes in the living conditions of phototrophic organisms.

Anomalies of bromine in the estuarine sediments as a signal of floods associated with typhoons

X-ray fluorescence scanning with synchrotron radiation was performed to study sediment core records of floods in Amur Bay, Sea of Japan. Interlayers of 3–8 mm with abnormally low bromine content were formed by the Razdolnaya River discharge to the central part of the bay during extreme floods, accompanied by severe storms at sea. Such conditions in the region are typical for periods of deep tropical cyclones (typhoons), to which the distinguished interlayers were compared on the timescale. This approach was made possible thanks to the high rate of sedimentation in the bay (3–5 mm/a) and low bioturbation of sediments under anoxic conditions.

Reconstruction of the conditions of Late Holocene sedimentation by integrated analysis of a core of the bottom sediments from the Chukchi Sea

Integrated studies were performed on bottom sediments collected in the Chukchi Sea in the northern part of the Gerald Canyon 150 km northeast from Wrangel Island. The recent sedimentation rate amounted to 0.9 mm/year by 210Pb at the sampling site. The concentrations of biogenic components (SiO2bio, Сorg, Ntot, and Br) were minimum at the lower part of the core, where an increase of Thalassiosira antarctica antarctica, probably results from low biological productivity during the Maunder Minimum. The increased concentrations of biogenic components, as well as the decreased values of magnetic susceptibility and X-ray density, in the upper part of the core (1–2 cm) correspond to the last decade of recent of global warming.

Carotenoids in bottom sediments of lake Shira as a paleoindicator for reconstruction of Lake States in Khakassiya, Russia

The concentrations of carotenoids buried in the bottom sediments of Lake Shira (Siberia, Khakassiya) have analyzed for the period of the last 2300 years. The bottom sediments were found to contain carotenoids, which are molecular markers of the corresponding groups of Phototrophic organisms. The bottom sediments of Lake Shira were shown to be a promising object for climate reconstructions of the Late Holocene in southern Siberia.

Influence of meteorological conditions on the geochemistry of modern bottom sediments exemplified by deposits of Donguz-Orun Lake, Caucasus

Cores of bottom sediments from epiglacial Donguz-Orun Lake (Cis-Elbrusian, Northern Caucasus) have been studied. Here we present descriptions of the sampling techniques, sample preparation, and analytical procedures by the X-ray fluorescence method. The sedimentation rate, estimated by calculation of peaks of the Rb/Sr ratio as well as employing isotope concentrations of 137Cs and 210Pb in the upper parts of the core, permitted us to assume the annual character of the regularly laminated sediment. A statistically significant correlation between the concentration variations of certain chemical elements and their groups in the sediment against normalized meteorological data from the Terskol meteorological station has been revealed. This makes the studied object applicable for development of high resolution palaeoclimate reconstructions.

Sedimentation rate in Cheko Lake (Evenkia, Siberia): New evidence on the problem of the 1908 Tunguska Event

We estimated the age and sedimentation rate of bottom sediments in Cheko Lake located in southern Evenkia, in the territory of Tunguska Nature Reserve, near the supposed epicenter of the so-called 1908 Tunguska Event. The vertical distributions of 137Cs and 210Pb activity and visually counted varves in the core of lake bottom sediments indicate that Cheko Lake is significantly older than the 1908 Tunguska Event; therefore, the lake basin cannot be a crater or a trace of the explosion as was supposed earlier by some researchers.

The Study Internal Structure of the Annual Layers in Lake Sediments Using Synchrotron Radiation with X-ray Focusing Optics

1 Introduction Annually laminated(varve)sedimentary deposits are considered as one of the most important archives,since they offer precise temporal information(years)in combination with high time resolutions.Bottom sediments of the lakes contain detailed geochemical information on

ANNUAL SEDIMENTARY RECORD FROM LAKE DONGUZ-ORUN (CENTRAL CAUCASUS) CONSTRAINED BY HIGH RESOLUTION SR-XRF ANALYSIS AND ITS POTENTIAL FOR CLIMATE RECONSTRUCTIONS

Bottom sediments of the proglacial Lake Donguz-Orun situated at ~2500 m a.s.l. in the Elbrus Region (Central Caucasus) reveal regular laminae, characteristic of proglacial varved lakes. This is the first laminated sediment sequence recorded in the region. However, visual counting of the layers was restricted due to partial indistinctness of the lamination. In order to confirm the annual sedimentary cyclicity and proceed with annually resolved data, in addition to the visual identification we used high resolution geochemical markers. The upper 160 mm of the sediment core were scanned at 200 µm intervals using synchrotron radiation X-ray fluorescence analysis (SR-XRF). Additional ultrahigh resolution scanning at 30 µm increments was employed for the upper 20 mm of the core. The Rb/Sr and Zr/Rb ratios are interpreted to record annual changes in grain-size. Based on this geochemical assessment, we identified 88 annual layers covering the interval between 1922 and 2010, while visually we have been able to identify between 70 and 100 layers. The correctness of the geochemical results is confirmed by mean accumulation rates assessed by 137Cs and 210Pb dating. Cross-correlation between the ring width of local pine chronology and the layer thickness, identified as a distance between the annual Rb/Sr peaks, allowed for the accurate dating of the uppermost preserved year of the sediment sequence (AD 2010). Annually averaged elemental data were then compared with regional meteorological observations, glacier mass balance and tree-ring chronologies. The comparison revealed notable conformities: content of bromine is positively correlated with annual temperatures (r=0.41, p<0.01), content of terrigenous elements (major elements with the origin in watershed rocks) is positively correlated (up to r=0.44, p<0.01) with annual precipitation. A high statistically significant negative relationship is observed between the concentrations of terrigenous elements and tree-ring width of local pine chronology (up to r=-0.56, p<0.01). Taken together, these data point to a common composite climatic signal in the two independent records (lake sediments and tree rings) and confirm that the laminae represent annual layers (i.e., varves). These findings open opportunities for high resolution multiproxy climate reconstructions 300-350 years long using the longer sediment core and tree-ring records.

Chukchi Sea Ice Conditions for the Last Few Centuries: Reconstruction from Sedimentation Records

For the first time, the reconstruction of variations in the duration over several hundred years was conducted on the basis of models developed by comparing hydrometeorological observations and detailed scanning of the chemical composition of bottom sediments accumulated during the corresponding period. The gauge models for the reconstruction of air temperature and ice cover of the water area for three sites in the northern part of the Chukchi Sea have been developed. During the reconstruction, an insignificant increase in the duration of the ice-free period during the Little Ice Age was established, which does not coincide with the changes in the temperature regime that took place. It is concluded that the dynamics of the inflow of warm Pacific waters through the Bering Strait had the predominant influence on the ice regime of the Chukchi Sea.