Filamentous Cyanobacteria from the Vendian Deposits of the Nepa Regional Stage of Interior Areas of the Siberian Platfor
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mentous Cyanobacteria from the Vendian Deposits of the Nepa Regional Stage of Interior Areas of the Siberian Platform E. Yu. Golubkovaa, * and B. B. Kochnevb, c aInstitute
of Precambrian Geology and Geochronology, Russian Academy of Sciences, St. Petersburg, 199034 Russia Institute of Petroleum-Gas Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia cNovosibirsk State University, Novosibirsk, 630090 Russia *e-mail: [email protected]
bTrofimuk
Received November 1, 2018; revised August 23, 2019; accepted September 3, 2019
Abstract—The morphological diversity and stratigraphic distribution of filamentous microfossils in the Vendian deposits of the Nepa Regional Stage of the interior of the Siberian Platform were analyzed. Hormogonian cyanobacteria of five genera (Nepia gen. nov., Talakania, Oscillatoriopsis, Obruchevella, and Siphonophycus) were identified in the composition of the Nepa biota. A monographic study was carried out, and a reproductive life cycle of the novel oscillatorian cyanobacterium Nepia calycina Golubkova, gen. et sp. nov. was reconstructed. The species Talakania obscura Kolosov, emend. was assigned to the polytrichomic cyanobacteria that are similar to the present-day genera Schizothrix and Microcoleus. Keywords: microfossils, cyanobacteria, Vendian, Eastern Siberia DOI: 10.1134/S0031030120050068
INTRODUCTION Despite a long history of research on organicwalled microfossils, the position of most taxa from the Upper Precambrian has not been defined in the taxonomy of the present-day organisms. The current situation is explained by the incomplete and often poor preservation of the paleontological material, which significantly complicates paleobiological studies. Therefore, new data are of great scientific importance, since they allow us to determine the taxonomic position of some Vendian microfossils, which were previously assigned to the formal subgroup of filamentous algae. In this study, we analyzed the taxonomic diversity, morphological structure, and occurrence of filamentous algae isolated as a result of the chemical dissolution of the Vendian terrigenous deposits of the Nepa-Botuoba, Prepatom, and Syugdzhera districts of East Siberia (Fig. 1). BRIEF GEOLOGICAL REVIEW AND STRATIGRAPHIC DISTRIBUTION OF FILAMENTOUS ALGAE Intensive micropaleontological studies of the Vendian deposits of the Nepa Regional Stage in the Siberian Platform interior areas have revealed taxonomically heterogeneous assemblages of microfossils containing filamentous algae (Pyatiletov, 1980; Kolosov, 1983, 1984, 2014; Kolosova, 1991; Golubkova et al.,
2010; Nagovitsin and Kochnev, 2015; Stanevich et al., 2015). The most general approximation suggests that the Upper Precambrian sedimentary cover of the studied region is composed of Lower and Upper Vendian terrigenous sequences of the Vilyuchan and Nepa Regional Stages, which are overlain by the Upper Vendian carbonate and evaporite deposits of the Tira and Danilov Regional Stages in the upper part of the section (Stratigraf
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