ORDOVICIAN MARINE SEDIMENTS OF TYVA, ALTAI-SAYAN FOLDED AREA: BIOSTRATIGRAPHY, FACIES, COMPOSITION AND SPECIFIC OF FAUNAL ASSEMBLAGES AND PALEOGEOGRAPHIC LOCALITY
N.V. Sennikov, O.T. Obut, N.G. Izokh, A.V. Timokhin, I.V. Korovnikov, E.V. Lykova, R.A. Khabibulina
Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Tyva, Ordovician, litho-biostratigraphy, marine sedimentary and volcanic-sedimentary strata
Abstract
New lithological and biostratigraphic data on stratotype and paleontologically representative marine sedimentary sections of the Malinovka Group (Borlug, Tarlyk and Tamzyrin formations) in the Uyuk area of the region; Shemushdak Group (Ayangaty and Adyrtash formations) and Chergaky Group (Alavelyk Formation) in the Khemchik area of the region; Chergaky Group (Alavelyk Formation) in the Alash area of the region; Kargy Formation in the Kargy area of the region are discussed. The materials on the Sistigkhem Group (Uza, Ust’-Khamsary and Kugar formations) in the Sistigkhem area of Tyva are considered. The chronostratigraphic position of the Tarlag-Aksy Horizon has been clarified and the identification of a new Borlug Horizon has been substantiated. It has been found out that outrcops of the Tyva Ordovician marine sediments are currently located in the number of tectonically isolated blocks and are not fragments of a single paleobasin. Based on the analysis of the taxonomic composition of faunal assemblages and ichnofossils, it is suggested that the Tuvinian Alash-Khemchik, Uyuk and Kargy blocks with outcrops of Ordovician marine sediments were paleozoogeographically close to the marine paleobasins of the Gondwana group of continents. At the same time, a low migration potential of their faunal assemblages relatively to the possibilities of communication with coeval communities of the Altai Basin and of that of
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the Siberian Platform and Taimyr was observed. The Tuvinian Sistigkhem block characterized by effusive-sedimentary sequences of the marine genesis was not only at a significant distance from the listed Siberian paleobasins, but was also separately located from the group of Alash-Khemchik, Uyuk and Kargy blocks with Ordovician marine sediments.
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