Recent studies allow refinement of the principal Vendian stratigraphic standard of the Russian platform. The Vendian, which was established 20 years ago as the youngest sedimentary complex of the upper Precambrian of the Russian platform, is significant in correlation of upper Precambrian rocks on a wide scale. Peculiar geologic features of the Vendian, its structural and stratigraphic position, and its stratigraphic boundaries and subdivisions are in many respects comparable with upper Precambrian rocks of other regions and continents. The Vendian is also significant in determination of the position of a main glacial formation, in recording the earliest appearance of an Ediacaran-type fauna and in the relation of this fauna with a paleontologic succession of the oldest P ecambrian, and in isotopic-age characteristics. All these features are of more universal importance than are facies characteristics of the formations composing the Vendian (and its equivalents); thus, the Vendian of the Russian platform has rapidly become a most significant time-stratigraphic standard.

Although the Vendian is represented by terrigenous deposits on the Russian platform and by carbonate and carbonate-terrigenous deposits on the Siberian platform, it undoubtedly represents an important, separate stage in the geologic history of the earth. At the transition from the Vendian to the Cambrian, an important biologic change took place which resulted in the appearance of skeletal-building properties of organic parts of animals. The significance of such a succession is worldwide. It is concluded that the Vendian represents the beginning of the Phanerozoic--not the close of the Cryptozoic--and is more closely related to the Paleozoic, though formally it is not included in that era.