Выпуск: 5 , Том: 38 , Год издания: 1997

The paper discusses the data on the uppermost (8 to 14 m) layer of Lake Baikal bottom sediments sampled by tube corers on the crest of the underwater Akademicheskii Ridge at three sites separated by large distances (30 km). The cores were subjected to lithological description, color photography and X-ray fluorography. Samples taken at 10 cm intervals were analyzed for the content of water, opaline silica, organic carbon, total uranium, thorium, molybdenum, and 14 other elements. Quantitative diatom analysis was done at 2-10 cm interval using light microscopy. Scanning electron microscopy was applied to ensure correct identification of some diatom species. Pollen grains and sponge spicules were also identified and counted. A section of one of the cores was subjected to paleomagnetic measurements and a magnetic excursion was found. The three cores perfectly correlate with each other exhibiting cyclic changes in the content of opaline silica and diatom frustules. A new method of U-series dating was applied to the data on the activities isotopes obtained by Egdington at al. (1994); a new interpretation suggests that the age of one of core is ca. 100.000 years. The cores are well correlated with each other in all parameters, which is indicative of quiet continuous sedimentation. The diatom-rich layers in the Baikalian cores seem to correspond to oceanic stages of warm climates (stages 1, 3, 5), while the beds with no diatoms correspond to the stages of global glaciation (stages 2 and 4). The contents of diatoms, biogenic silica, and organic carbon are positively correlated with those of U and Mo. The profile of a total diatom content taken for one of the 2-cm cores indicates that during the time studied drastic short-periodic climatic variations occurred in the Baikal area. The Baikal sedimentation record correlates with the high-resolution record of North Atlantic paleoclimates interpreted by Bond et al. (1993). Typical times of appearance and disappearance of some species of diatoms are rather small(100-500 years). The paleoclimate record documented in sediments of the Akademicheskii Ridge in time resolution satisfies the requirements of international programs.