Depositional Environments in the Eastern Paratethys during the Final Middle Miocene Transgression (Kura Basin, Eastern G
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sitional Environments in the Eastern Paratethys during the Final Middle Miocene Transgression (Kura Basin, Eastern Georgia) Yu. V. Rostovtsevaa, b, * a
Geological Faculty, Lomonosov Moscow State University, Moscow, 119991 Russia bGeophysical Center, Russian Academy of Sciences, Moscow, 119296 Russia *e-mail: [email protected] Received February 12, 2020; revised April 16, 2020; accepted June 17, 2020
Abstract—The mineral composition and depositional environments of the Konkian in eastern Georgia (Kura trough, eastern Paratethys) corresponding to the Kosovian (13.65–12.829 Ma) in the Central Paratethys and the final Middle Miocene marine transgression in Paratethys are considered. Jurassic and Cretaceous volcanic rocks of the Lesser Caucasus (Adzhar–Trialet and Artvin–Bolnisi zones) were identified as the main provenances for the terrigenous material. Eight lithofacies types distinguished for the studied rocks characterize depositional environments with significant wave or submarine-fluvial influence. The change of depositional environment was controlled by the phases of transgression, as well as by the progradation and lateral migration of the prodelta. The development of depositional environment corresponds to the Konkian stratigraphic beds and reflects the main stages of the final Middle Miocene transgression in the Eastern Paratethys. Keywords: depositional environments, Konkian regional stage, Middle Miocene, Eastern Paratethys DOI: 10.1134/S0024490220060061
INTRODUCTION Drastic changes of the depositional environment in the Eastern Paratethys took place during both its isolation from open seawater and the development of large-scale transgressions providing a revival of the connection of Paratethys basins with the Mediterranean basin and World Ocean. Comprehensive study of the transgressive stage beds is important, because it allows the interregional correlations and synchronization of stagewise sedimentation. In the Central Paratethys, the last large Middle Miocene marine transgression was represented by the late Badenian seawater input in the Kosovian (13.65–12.829 Ma) (Hohenegger et al., 2012, 2014) leading to termination of the Badenian salinity crisis. This event is represented in the Eastern Paratethys by the Konkian transgression (Hilgen et al., 2012) that promoted favorable conditions for the habitat of marine communities, which replaced the Karaganian basin environment with unstable water salinity and endemic mollusk fauna. Deposits of the Kosovian and Konkian regional stages are overlain by the Sarmatian sequences deposited in a spacious basin extending from the Alps to the Aral Sea and having only episodic connection with the open seawater. Despite a long-term study of the Middle Miocene Konkian rocks in the Eastern Paratethys, issues related to their stratigraphic subdivision remain debatable so far. According to (Nevesskaya et al., 2004), the Kon-
kian regional stage is subdivided into the Sartaganian and Veseljanian beds. The Sartaganian beds are characterized by a diverse assemblage of polyhal
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