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Within the framework of the Baikal Drilling Project (BDP), a 192 m long sediment core (BDP-96-1) was recovered from the Academician Ridge, a submerged topographic high between the North and Central Basins of Lake Baikal. Sedimentological, clay mineralogical and geochemical investigations were carried out on the core interval between 90 and 124 m depth, corresponding to ca. 2.4–3.4 Ma. The aim was to reconstruct the climatic and tectonic history of the continental region during the intensification of Northern Hemisphere glaciation in Late Pliocene time. A major climate change occurred in the Lake Baikal area at about 2.65 Ma. Enhanced physical weathering in the catchment, mirrored in the illite to smectite ratio, and temporarily reduced bioproduction in the lake, reflected by the diatom abundance, evidence a change towards a colder and more arid climate, probably associated with an intensification of the Siberian High.
Two boreholes, one to a depth of 300 m, and the other to a depth of 100 m below sediment surface were drilled at 53°41´48´´N-108°21´06´´E. The core was collected down to 200m in the first borehole, and totally in the second one. Yield of the cores was more than 95%. Sediments consist of terrigenic and biogenic silts. All along the section, clay layers alternate with layers of diatomaceous silt. Studies of the section revealed that sediments accumulated under deep water during all the period of their deposition; no hiatuses or unconformities were found. Studies done in Russia, USA, Japan and Germany gave results that are consistent with each other. Correlation of magnetic properties with the palaeomagnetic scale revealed that the age of sediment at 200 m is 5 My. Mean sediment accumulation rate was constant and equaled 4 cm per 1 ky, Rhythmic structure of the sediments consisting of layers of diatom-barren clays and diatomaceous silts is due to cyclic changes of cold and warm climates.
Lake Baikal, in south-central Siberia, has been the focus of an international effort (the Baikal Drilling Project; BDP) to obtain continuous long cores (upwards of 100 m) from this unique rift-valley lake and to interpret the paleoclimatic history from various proxy data. As part of this effort, the clay minerals were examined by two research teams. A consistent clay-mineral assemblage, containing illite, interstratified illite-smectite, chlorite, and kaolinite as the major minerals, characterizes much of the modern sediments. The relative abundance of these minerals changes with depth in both short piston cores from various parts of the lake and in 100-m-long cores taken from the distal toe of the Selenga Delta (BDP-93).
Major and trace elements in the 100 m drilling core samples from Lake Baikal have been determined by ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry) and INAA (instrumental neutron activation analysis). In this paper, vertical distribution profiles of the determined elements are presented. Raw analytical values will be presented elsewhere. Vertical distribution patterns for Ti, Al, Fe, Mn, Ca and Pare shown in Fig.1. In the bottom surface sample (=the uppermost part of the core), the concentration of Al, Ti, Fe and Ca are relatively low and that of P is relatively high. It may indicate that relative large volume of biogenic organic substances are included in the bottom surface sample. In addition, it seems that the Mn contents are relatively low and its deviation is rather small between 60 m and 90 m from the bottom.
We made magnetic measurement of 32 cubic specimens of sub-bottom sediments of Lake Baikal. These are part of the sub-samples for palaeomagnetic investigations obtained from the sediment cores from hole 1 of Baikal Drilling Project (BDP). This hole was drilled to the depth of about 100 m below the lake bottom. Our samples are almost evenly spaced with the average interval of 2 m in the drilled section. The sedimentation rate at the drilling site on the Buguldeika has been estimated relatively low. Our prime interest was therefore to investigate whether or not the BDP-1 cores penetrate the Brunhes/Matuyama boundary dated at 0.78 Ma (Shackleton et al.,1990). Initially, we measured natural remanent magnetization (NRM) of all the specimens, using a flux-gate spinner magnetometer (Natsuhara Giken, SMD-88). The intensity of NRM ranges between 2.2x10^-3 to 70.7x10^-3 A/m, which is sufficiently higher than the background noise level of our spinner magnetometer.