Lower Vendian microfossil assemblages of East Siberia: Significance for solving regional stratigraphic problems |
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Authors: | E Yu Golubkova E G Raevskaya A B Kuznetsov |
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Institution: | 1.Institute of Precambrian Geology and Geochronology,Russian Academy of Sciences (IGGD RAN),St. Petersburg,Russia;2.Federal State Agency,Scientific-Industrial Enterprise “Geologorazvedka”,St. Petersburg,Russia |
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Abstract: | Both published and original data are used for the analysis of the stratigraphic position and taxonomic characteristics for
acanthomorphic microfossils of the Pertatataka type in Lower Vendian sediments of the central and southeastern Siberian Platform
and its surrounding structures. Four taxonomically different microbiotas are distinguished in sections of the Nepa-Botuoba,
Fore-Patom; Syugdzher, Anabar, Zhuya-Lena, and Berezovo lithotectonic zones: two diverse (Nepa and Ura) and two impoverished
(Otradnino and Torga) each including diagnostic Early Vendian taxa. Beyond the Siberian Platform, genera and species characterizing
these microbiotas occur in single assemblages and represent diagnostic taxa of the second (Tc-Sr-Vl) and third (Ti-Cg-Mp)
zones of the acritarch scale proposed by Australian geologists as a biostratigraphic basis for subdividing the Ediacarian
of the Standard stratigraphic scale (SSS). In the Russian General stratigraphic scale, the distribution of Pertatataka acritarchs
corresponds to the Lower Vendian. The appearance and mass development of acanthomorphic microorganisms represents a global
biological event, which should be taken into consideration as a biostratigraphic criterion for defining the Vendian System.
For substantiating age, the following species among diagnostic Lower Vendian forms of East Siberia should be used: Appendisphaera grandis, “Appendisphaera” tabifica, A. tenuis, Ceratosphaeridium glaberosum, Dicrospinosphaera virgata, Multifronsphaeridium
pelorium, “Polygonium” cratum, Tanarium conoideum, Variomargosphaeridium litoschum, and Talakania obscura. These taxa are readily recognizable, morphologically stable, and characterized by their wide lateral distribution and relatively
narrow stratigraphic range. Their occurrence in the upper part of the Dal’nyaya Taiga Group of the Baikal-Patom region indicates
that host sediments should be attributed to the Lower Vendian, not the Upper Riphean as is currently accepted. |
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