MAIN TYPE REFERENCE SEQUENCES OF THE EARLY PRECAMBRIAN IN THE U.S.S.R

Abstract

The Early Precambrian of the U.S.S.R. in the time span∼3500-1650m.y. ago (Archaean and Early Proterozoic) is characterized by typical supracrustal sequences of the Baltic Shield in Europe and the Aldan Shield in Asia. In the former the Belomorian and Lopian Supergroups are referred to as the type sequences of the Archaean. The type sequences of the Early Proterozoic are represented by the Karelian and Ladogan Supergroups. In the Aldan Shield Archaean-type sequences are known as the Aldan Supergroup and Olondo (Subgan) Group. The Oudukan and Akitkan (Oulkan) Groups are considered to represent Early Proterozoic type sequences. All these supracrustal sequences provide a basis for the older Precambrian chrono- and lithostratigraphic units in the U.S.S.R.