Paleontological and Lithological Characteristics of the Lower Miocene Stratotype Sections of the Eastern Paratethys (Kartli Depression, Georgia)

• Published in: Stratigraphy and geological correlation 2022-10, Vol.30 (5), p.408-430
• Main Authors: Popov, S. V., Aleksandrova, G. N., Voronina, A. A., Zaporozhets, N. I., Golovina, L. A., Koiava, K. P.
• Format: Article
• Language: English
• Subjects: Alliances; Archaeology; Climate; Composition; Correlation; Earth and Environmental Science; Earth Sciences; Geophysics/Geodesy; Gravel; Historical Geology; Humid climates; Lithology; Miocene; Mollusks; Nannoplankton; Nanoplankton; Ocean basins; Oligocene; Pollen; Sedimentology; Spores; Stratigraphic correlation; Stratigraphy; Structural Geology; Taxa; Water temperature
• ISSN: 0869-5938; 1555-6263
• DOI: 10.1134/S0869593822050057

— In terms of lithology and mollusk composition, the Uplistsikhe Formation is subdivided into two subformations and five members. The Sakaraulian and Kotsakhurian regional stages are characterized by a distinct two-member structure: a coarser sandy–gravel lower part and a finer sandy–silty–clayey upper part. All these divisions are mapped within the Kartli Depression from Gori to Kaspi. On the basis of the dinocyst and nannoplankton compositions in the Uplistsikhe, Nadarbazevi, and Kvakhvreli sections, the stratigraphic units of the Kartli Depression are correlated with the zonal and Mediterranean scales. The Oligocene/Miocene boundary in the Gori–Uplistsikhe section was drawn at the base of the Upper Uplistsikhe Subformation according to the appearance of warm-water mollusks with Cardita caliculata and the disappearance of zonal Oligocene species Sphenolithus cyperoensis (NP25), with the continued presence of Triquetrorhabdulus carinatus (NN1). The study of dinocysts carried out for the first time demonstrates their applicability for stratigraphic correlation of the Early Miocene assemblages in the Kartli Depression. Some Miocene taxa markers such as Chiropteridium galea , Cousteaudinium aubryae , and Trinovantedinium harpagonium make it possible to carry out the correlation with the biozoning of the Central Paratethys, the Danish part of the North Sea, and the Atlantic coast of the United States of America. Taking into account the dinocyst assemblage in the upper part of the Lower Uplistsikhe Subformation–lower part of the Upper Uplistsikhe Subformation, this interval can be dated to the second half of the Chattian–Aquitanian. The Sakaraulian upper part corresponds to zones DN2–DN3 on the scale of the Atlantic coast of the United States and is dated to the second half of the Aquitanian–part of the Burdigalian. Findings of stratigraphically important dinocyst species Cousteaudinium aubryae , Trinovantedinium harpagonium , and Lingulodinium multivirgatum in the Upper Sakaraulian in the Nadarbazevi section make it possible to compare this assemblage with zones DN2–DN3 and to correlate it with zones NN3–NN4 in terms of nannoplankton. The age of this part of the Kotsakhurian is taken as the late Burdigalian–part of the Langhian. The absence of endemic dinocyst taxa, in particular, in the Kotsakhurian, which is considered to be the closing stage of the Eastern Paratethys, suggests the continued connection between the sea and open basins. The obtained spore–pol