Andrey Darin

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.

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.

Natural periodic processes and climate variability in the Northern Hemisphere

Decomposition of five different paleoclimatic reconstructions of regional and hemispheric scale into different frequency periodic components has been performed for the extratropical zone of the Northern Hemisphere using spectral analysis methods (Hilbert–Huang transformation, wavelet transform, Fourier transform). The presence of ~1000, ~500, ~350, and ~200-year quasi-cyclic periodicities has been established, which determines climatic variability over the last 2–4 millennia. The presence of similar cyclicities, manifested in climatic and other geological processes, has been noted by many researchers and has been explained, as a rule, by changes in solar insolation. Thus, there is every reason to believe that the revealed quasi-periodic components in the climate variability of the extratropical zone of the Northern Hemisphere are natural, conditioned by natural cyclical phenomena and can serve as a basis for long-term predictive climatic constructions.

Complex use of the geochemical features of bottom deposits and pollen records for paleoclimate reconstructions (with lake Teletskoe, Altai Republic, as an example)

The delayed response of taiga and steppe biomes to climate changes has been detected with Lake Teletskoe as an example. A paleoreconstruction has been made on the basis of the integral use of geochemical features of bottom sediments and pollen records. It showed 100-year mean temperatures to a time depth of 4000 years with the isolation of the assumed boundaries of climate reconstructions in the 14th and 4th centuries B.C. and the 13th and 20th centuries A.D. A comparison of the temperature reconstruction for Lake Teletskoe with the temperature chronologies for the Northern Hemisphere and northeastern Europe has been carried out.

Geochemical signal of seasonality in annually laminated organic- carbonate sediments in Shira lake(Khakasia)

1 Introduction The most valuable for the task of climate reconstruction are the time series with an annual resolution,which allows to reveal natural periodicity and pass to the search for mechanisms of regional and global climatic changes.Bottom sediments of lakes are one of the best climate archives in addition to tree ring series,ice cores etc.

Lake Shira Level Changes in Late Holocene

1 Introduction Meromictic Shira Lake is a good represfor detail climate modeling due to its locainformation and annually laminated bottomsediment column of 155 cm in length wahammer corer in the deepest(24 m)central in 2009.2 Sample Preparations and Measuring