Home – Home – Jornals – Russian Geology and Geophysics 2006 number 7

The scheme of regionalization of the northern Siberian craton has principally been amended. It is proven that the succession of structural elements distinguished in the north is the same as in the south: oceanic block, pericratonic trough, and belt of intracratonic basins. Each of these structures can be, in turn, divided into several structure-facies zones. As in the south, three main stages of development have been established in the Neoproterozoic of the above structural elements, which correspond to the Mayanian, Baikalian, and Vendian.
The most considerable modifications are made in dating of the earlier established stratigraphic divisions. It is proven that the Debengda and Lower Yusmastakh Formations of the northern Siberian Platform correspond to the Kerpylian. The carbonate marker characterized by fossils of the Lakhanda Horizon plays an extremely important role in all structural elements of the northern Siberian craton. It comprises the Upper Yusmastakh, Khaipakh, Neleger, Sietachan, and somewhat more complicated Udzha Formations of the belt of intracratonic depressions; Chernaya Rechka and coeval Medvezh'ya Formations of the pericratonic trough, as well as the Kolosov and Kan'yon Formations of Taimyr. These modifications were promoted by a revision of biostratigraphy of many taxa of stromatolites and microfossils in the adjacent regions of Siberia. The microphytoliths of the Kalanchevo Complex cannot be used to determine the Baikalian and Vendian ages for the Medvezh'ya and Kolosov Formations. Thus, it was proven that the Baikalian is completely missing from northern Siberia. We argue that this is not due to the pre-Vendian erosion. Most likely, sedimentation was interrupted throughout the area by pre-Baikalian tectonic events.
The age of the oceanic volcanosedimentary and volcanogenic deposits in the Chukchi-Borzov and Zhdanov structure-facies zones is essentially refined. It is proven that they correspond to the Mayanian alone. An argument is that the wide fields made up of the island-arc volcanogenic complexes of this age are cut by narrow tabular bodies of ophiolites related to the pre-Baikalian rifting. As a result, we have corroborated the conclusion by V.E. Khain that there are two main borders of the Taimyr evolution: Grenvillian (1100 Ma) and Early Baikalian (850 Ma). We have shown that two principal events characterize the northern platform in the Neoproterozoic: formation of the supercontinent Rodinia in the Mayanian and the beginning of its breakup in the Baikalian. In the Vendian, after a large gap the superimposed troughs initiated as early as the Baikalian continued to develop.