Diatom flora and silicoflagellates of the Oligocene-Miocene deposits of the Apsheron region of Azerbaijan (Yashma section)

A comprehensive study of diatom algae from the Oligocene–Miocene Maykop deposits of the Yashma section, located in the South Caspian region, has been conducted for the first time. The main objectives of the work were to determine the species composition of the microflora, perform stratigraphic interpretation, and reconstruct paleoenvironmental conditions based on micropaleontological data. More than 20 samples were collected and processed using standard methods, including acid cleaning, slide preparation, and examination by light and scanning electron microscopy. The composition and preservation state of the microflora made it possible to reconstruct the paleoenvironmental conditions. For the first time, the presence of silicoflagellates was also established, indicating marine and warm depositional conditions.Specific paleoecological conclusions were obtained for the sections: in Yashma, a transition was revealed from freshwater fauna to subtropical marine fauna with high productivity in the Late Miocene. The obtained data refine the stratigraphy of the region, demonstrate fluctuations in the water level and salinity of the Eastern Paratethys basin, and highlight the diagnostic value of diatoms.