Russian Journal of Earth Sciences
Vol. 4, No. 5, October 2002
Vendian foreland basin of the Siberian cratonic margin:
Paleopangean accretionary phases
J. K. Sovetov
Abstract
Vendian, chiefly clastic sedimentation on the southwest of the Siberian craton is
discussed under the tenet of a foreland basin that came into being in the Vendian epoch at the
margin of the Siberian continent (craton) due to its collision with island arcs and
microcontinents. The Vendian foreland basin of the Siberian cratonic margin, over 3000 km in
length, was formed in the Early and Late Vendian. To use a paleotectonic framework, the
terrestrial and marine deposition in point took place in the Yenisei-Baikal belt of foredeeps
and in its coeval Baikit-Nepa belt of forebulges in the cratonic interior.
Vendian age of molasse and the foreland basin is proved by new data: (1) tillites
reported from the base of the Oselkovaya Group (Marnya Formation) of the Sayan foredeep
and (2) the find of a Metazoa mollusk biota. The tillite-bearing horizon occurs at the base of
the "lower marine assemblage" and, using cyclic sequences and carbonate sedimentary
marker systems, it is traceable on the Yenisei Ridge, in Cisbaikalia, and in the cratonic
interior. Sedimentologic data and the vector of clastic transport suggest that the ice cap was
located on the Siberian craton, and the Siberian glacial horizon is correlatable to the global
Laplandian horizon of the Vendian
[Chumakov, 1978].
The foreland basin passed three evolutionary phases: (1) initial accretionary, (2) glacial
(pre-collisional), and (3) collisional. Based on sedimentologic data, each phase falls
into several evolutionary stages, each stage reflecting an erosion pulse and redeposition of
clastic sediments. During the accretionary and collisional phases, changes in sedimentary
systems were associated with tectonic activity and, indirectly, with eustatic sea-level
oscillations. During the glacial phase, deposition of third-order cyclic sequences was chiefly
controlled by eustatic changes of the level of the world ocean, forced by growth and melting
of ice caps. The synchroneity and interplay of climatic and tectonic events in the Vendian on
most continents and microcontinents can be explained by a model for the Paleopangean
supercontinent accretion in the Vendian.