STRATIGRAPHIC POSITION AND INTEGRATED CHARACTERISTIC OF THE UPPER VENDIAN NEMAKIT-DALDYNIAN STAGE
V.V. Marusin
1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences,Novosibirsk, Russia
2Novosibirsk State University,Novosibirsk, Russia
Keywords: Vendian, Cambrian, General Stratigraphic Scale of Russia, International Chronostratigraphic Chart, small skeletal fossils, trace fossils, chemostratigraphy, Siberian Platform
Abstract
Nemakit-Daldynian Stage was originally introduced as a regional stage, embracing the lowermost Cambrian strata with the oldest small skeletal fossils, for the Anabar Uplift sections in the 1960s. In subsequent years, it became widespread in the works of Soviet researchers as the terminal Vendian or basal Cambrian stage or regional stage. Almost at the same time, the concept of the Manykaian Stage appeared which is close in its volume and geological meaning to the Nemakit-Daldynian Stage. Although this unit plays a crucial role for our understanding of the chronology of biotic turnovers at the Vendian–Cambrian transition, its status, age, and correlation with the Manykai Stage and units of the International Chronostratigraphic Chart (ICC) remain unclear. This research reveals a historical background revisits the stratigraphic volume and age of the Nemakit-Daldynian Stage. The integrated biostratographic, stable isotope and geochronological data shows this unit belongs to the Upper Vendian and spans the interval from the first appearance of unequivocal anabaritids (~539 Ma) to the first appearance of the Tommotian small skeletal fossils (~530 Ma). In this interpretation, the Nemakit-Daldynian Stage corresponds to the Fortunian Stage of the Cambrian System in the ICC. The base of this unit is coeval to the base of the Rovno Regional Stage of Baltica.
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