M.A. Phedorin

A 1‐Myr record of paleoclimates from Lake Khubsugul, Mongolia

The ancient Lake Khubsugul in North Mongolia is situated at the far reach of moisture from the North Atlantic into continental Asia [Kuznetsova, 1978]. It is remote from the Pacific Ocean and shielded from the China Sea and the Indian Ocean by high mountains. Information on the paleoclimates in this territory is scarce and sometimes controversial. In winter of 2003, due to a joint project (Khubsugul Drilling Project or KDP) of the Siberian Branch of the Russian Academy of Sciences and the Academy of Sciences of Mongolia, a 53-m drilling core (KDP-1) of sediments of Lake Khubsugul was obtained. This article describes the first results of paleomagnetic and geochemical studies of this core, which was found to span the time interval of the last 1.05 Myr. The data suggest that global climate oscillations manifested themselves in repeated desiccation and filling of the lake due to changes in humidity.

Synchrotron radiation X-ray fluorescence analysis of VEPP-3 of the bottom sediments of Lake Baikal to perform a paleoclimatic reconstruction

Abstract Data on the element composition of 107 samples collected by drilling down to a depth of 11 m on the bottom of the Academican Ridge, Lake Baikal, are reported. Some experimental aspects of SRXFA on VEPP-3 appropriate for Baikal sediments are also described. The procedure of energy scanning was used to correct the data on RbMo concentrations in samples with significant U contents. A variant of geochemical paleoclimatic interpretation of these data has been carried out using additional U, Th/U and biogenic silica distribution. “Warm” and “cold” periods of climate with the corresponding mean contents of elements have been distinguished. The greater contents of almost all the elements during “cold” periods as compared to “warm” ones are observed. Compared to terrigeneous mud from the Central Depression of Lake Baikal, the total element contents of St. 15 are also elevated.

SR-XFA as a method of choice in the search of signals of changing palaeoclimates in the sediments of Lake Baikal, compared to INAA and ICP-MS

Abstract Sediments of Lake Baikal obtained on top of the underwater Akademichesky Ridge for reconstruction of the palaeoclimates of Holocene and Upper Pleistocene were subjected to elemental analysis with three methods: (i) synchrotron radiation X-ray fluorescent analysis (SR-XFA); (ii) instrumental neutron activation analysis (INAA); (iii) induction-coupled plasma mass-spectrometry (ICP-MS). Comparison of the results obtained is accompanied by statistical tests and shows that, due to its high sensitivity, simplicity, and non-destructive nature, SR-XFA can be recommended as a method of choice in the search of geochemical signals of changing palaeoclimates.

SRXFA OF ELEMENT COMPOSITION OF BOTTOM SEDIMENTS FROM TELETSKOYE LAKE

Abstract Samples of bottom sedimentary material of drilling column 02a from Teletskoye Lake were investigated by synchrotron radiation X-ray fluorescence analysis (SRXFA). Geochemically important elements (Zn, As, Fe, Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Pr, Nd) were determined. Results reveal the difference between sedimental layers associated with rhythmic layer-by-layer oscillation of mineral composition and grain size. A conclusion is drawn about the ability of using of the international geologic standard BIL-1 in studying sediments of Teletskoye Lake by means of a reference sample method in SRXFA.