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BDP-96, Academician Ridge
The second BDP site (Leg II) was on the Academician
Ridge, where during the winter of 1995–1996 two bore-
holes BDP-96-1 (300 m) and BDP-96-2 (100 m) were
drilled at the location 53741b48n N and 108721b06n E
in a water depth of 321 m (Fig. 1). The recovered core
in the borehole BDP-96-1 was 200 m.
The BDP-96 boreholes were drilled in the central
axial part of the underwater Academician Ridge. The
marginal parts of this elevated block are above the
level of Lake Baikal: Olkhon Island to the southwest
and the Ushkanie Islands to the northeast (Fig. 1). The
central part of the Ridge has a sediment cover approxi-
mately 1000–1500 m thick. Towards the margins of the
Ridge the sediment thickness decreases dramatically,
and the islands on both boundaries of the Academician
Ridge are the outcrops of the Proterozoic basement.
The lithology of the BDP-96 boreholes is remark-
ably uniform: the whole section consists of fine bio-
genic ooze and terrigenous clay. The content of diatom
material varies from 1 to 80% sediment volume, the
clay fraction from 5 to 90%, and the silt with sand
content is within the range of 1–40% (Fig. 4). Silt and
sand are generally dispersed or found in the form of
small lens-shaped inclusions. The colour of the sedi-
ments in general is dark olive grey, and the clay inter-
vals have a brighter grey colour. Similar to the upper
section of the BDP-93 cores, the sections of BDP-96
cores have a rhythmic structure due to alternations of
diatomaceous ooze and fine clay layers. This type of
alternating deposition is also reflected in the physical
properties of the sediments, for instance, in the water
content, which also fluctuates in a regular fashion.
Diatomaceous ooze is characterised by high water
content (50–55%) and low density (1.3–1.5 g/cm3
),
whereas terrigenous clays are more dense (1.6–1.7 g/
cm3