The results of palynological study of the reference section of upper Paleogene and Neogene deposits of the Kulunda Plain, exposed by borehole 2 (settlement Ozeryanka, Novosibirsk Oblast) are presented. In the Tavda Formation, a dinoflagellate cysts assemblage of late Priabonian age and a palynoassemblage with Quercus gracilis–Q. graciliformis of the late Eocene were identified. Nine palynoassemblages have been identified from continental Oligocene and Neogene deposits: Carya spackmania–Carpinus perfectus–Tilia of the beginning of the second half of early Oligocene; Betula–Corylus–Pinus s/g Haploxylon of the second half of early Oligocene; Juglans sieboldianiformis–Pterocarya stenopteroides–Fagus of the end of the early Oligocene, possibly the beginning of the late Oligocene; Castanea–Quercus–Myrica of late Oligocene; Pinus s/g Haploxylon–Abietinieaepollenites sellowiiformis–Cupressaceae of early Miocene, presumably the end of late Oligocene; Alnus–Ulmus–Polypodiales of early–middle Miocene; Betula–Quercus–Ulmus of middle Miocene and Alnus–Polypodiales–Sigmopollis of middle–late Miocene; Betula–Artemisia–Amaranthaceae of late Miocene. Layers with freshwater dinocysts Pseudokomewuia sp. 1 were found at the top of the Zhuravka Formation. The deposition environment in the late Eocene, Oligocene and Miocene in the south of the West Siberian Plain has been reconstructed. The marine transgression in the Priabonian extended to the north of the modern Kulunda Plain. The first half of the Early Oligocene in the region experienced a hiatus. After a significant cooling at the Eocene–Oligocene boundary, climatic conditions again became warm and humid as evidenced by the distribution the growth of mesophytic coniferous-broadleaf forests with hickory. In the second half of the early Oligocene, the climate became colder and more humid, and the proportion of elements of the Arcto-Tertiary flora increased in plant communities. During the end of the early Oligocene and the late Oligocene, the climate became warmer, and broadleaf trees dominated the forests. At the end of the late Oligocene, the climate again became more humid, but remained warm, and pine forests predominated in phytocenoses, with the participation of ancestral forms of modern Cathaya. The cooling at the turn of the late Oligocene–early Miocene led to the predominance of conifers in forests; in the early Miocene, the proportion of small-leaved tree species increased sharply, and the participation of pine trees decreased. In the middle Miocene, the climate remained quite warm, but drier, and cypress trees disappeared from the plant communities. In the late Miocene, open plant communities are formed.