Oligocene key section of South part of Eastern European Platform (North Ergeny)

The section of well 768, depth 362 m, which opened the Eocene and Maikopian deposits is comprehensively studied and can serve as a reference one for both the Northern Ergeny and the entire northern part of Paratethys. The data on lithology, mollusks, and benthic foraminifera made it possible to break up the Oligocene part of the Maikop Group into formations and subformations: Tsimlyansk, Solenovian and Kalmyk parts, compare them with neighboring and distant parts of Parathethys, with a regostage scale, restore basic sedimentation conditions. Based on nannoplankton and dinocyst composition, these units were compared with the global zonal scale (Gradstein et al., 2012), and according to the spore-pollen data, the evolution of the climate of the Parathethys northern margin was restored. The phytoplankton, foraminiferal and paleomagnetic data show a strong reduction of the section in the Eocene part, where only negatively magnetized fragments of the Keresta, Kuma and Belaya Glina formations separated by unconformity surfaces were distinguished. In the lower Oligocene part we saw the full set of biotic and paleomagnetic zones. The lower part of the Solenovian formation (50 m) is rarely complete, unlike most of the Ciscaucasian sections. The Kalmyk formation in this section is probably incomplete and responds only to the first half of the Chattian.