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Abstract With this paper we present a first attempt to
combine the direct results on lithology, composition
and age dating in the boreholes BDP-93, BDP-96 and
BDP-97 with geological and seismic data from the areas
where those sections were drilled. The sedimentary
environments represented by the BDP boreholes are
markedly different and possess characteristic litholog-
ical features. The results of the deep drilling provide
the essential means for testing numerous age models
used in geological reconstructions of the Lake Baikal
rifting dynamics. Neither the basin-wide unconformity
interpreted from seismic data, nor the interpreted
change from shallow-water to deep-water facies at the
boundary of the seismic stratigraphic complexes were
found in the BDP-96 boreholes on Academician Ridge.
Also, lithology does not support the proposed recon-
structions of intense lake level fluctuations and trans-
gressions during the Pliocene at Academician Ridge.
The continuous deep-water hemipelagic sedimentation
at Academician Ridge has existed for the past 5 Ma.
The beginning of an intense rifting phase of the
Neobaikalian sub-stage and related drastic changes in
sedimentation processes were interpreted on seismic
sections as the basin-wide unconformity B10. Different
age estimates for this boundary ranged from Late Plio-
cene (3.5 Ma) to Plio-Pleistocene boundary. As shown
by BDP-96 borehole, B10 is associated with a litholog-
ical change from diatomaceous ooze to dense silty clay
and not with an erosional contact. The new age for this
boundary in BDP-96 is approximately 2.5 Ma. This new
age constraint suggests that the upper sedimentary
strata of Northern Baikal (1.5–1.7 km thick) have
formed during the past 2.5 Ma with average sedimenta-
tion rates of 60–70 cm/ka. The BDP-93 boreholes at
Buguldeika suggest that uplift in Primorsky Range took
place prior to 1.07–1.31 Ma, a date which exceeds the
age of previous geological models.

Key words Rifting stages 7 Lake Baikal 7
Sedimentary environments 7 Lithology
Introduction
The objective of the Lake Baikal Drilling Project
(BDP) initiated in 1989 was to reconstruct environ-
mental and climatic changes in Inner Asia based on
studies of bottom sediments of the lake. The main
emphasis of the project has been palaeoclimate, and a
large number of publications of BDP are devoted to
the development of palaeoclimate proxies and age-
dating methods in the sedimentary record of Lake
Baikal and to reveal the signals of climatic change
(Bezrukova et al. 1991; Edgington et al. 1991, 1996;
Pampura et al. 1993, 1996; Peck et al. 1994; BDP
Members 1995, 1997a, 1997b, 1998; Colman et al. 1995,
1996b; Williams et al. 1997).
In conjunction with the development of palaeocli-
mate proxies of the Pleistocene and upper Cenozoic a
wealth of seismic data was collected in Lake Baikal by
Russian, American, Belgian and other international
teams. These data became essential for selecting the
drilling sites of BDP. The results of seismic studies
allowed previous models of rifting in Lake Baikal to be
evaluated in terms of age, subsidence rates and succes-
sion of tectonic events (Hutchinson et al. 1992a, 1992b,
1993; Zonenshain et al. 1992; Kazmin and Golmshtok
1996; Colman et al. 1996a; Moore et al. 1997; Scholz
and Hutchinson, this volume).
In this paper we make a first attempt to combine the
esults of the three drilling seasons with seismic data of
orresponding areas. We consider lithology and age-
ating results of the boreholes BDP-93, BDP-96 and
DP-97 with seismic cross-sections and their interpre-
ations. The boreholes are representative of different
edimentary environments: they were drilled in the
rea influenced by Selenga River, on the underwater
opographic high of Academician Ridge not influenced
y fluvial sedimentation, and on the bottom of the deep
outhern Basin of Lake Baikal.