Palynostratigraphy and Deposition Environment of the Late Paleogene and Neogene Deposits of the Kulunda Plain of Western Siberia

The results of palynological study of the reference section of upper Paleogene and Neogene deposits of the Kulunda Plain exposed by borehole 2 (village of Ozeryanka, Novosibirsk oblast) are reported. In the Tavda Formation, a dinoflagellate cyst assemblage of the late Priabonian age and a Late Eocene palynoassemblage with the Quercus gracilis–Q. graciliformis have been identified. Nine palynoassemblages have been identified from the continental Oligocene and Neogene deposits: Carya spackmania–Carpinus perfectus–Tilia of the beginning of the second half of the Early Oligocene; Betula–Corylus–Pinus s/g Haploxylon of the second half of the 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 the Late Oligocene; Pinus s/g Haploxylon–Abietineaepollenites sellowiiformis–Cupressaceae of the Early Miocene, presumably the end of Late Oligocene; Alnus–Ulmus–Polypodiales of the Early–Middle Miocene; Betula–Quercus–Ulmus of the Middle Miocene and Alnus–Polypodiales–Sigmopollis of the Middle–Late Miocene; and Betula–Artemisia–Amaranthaceae of the Late Miocene. Layers with freshwater dinocysts Pseudokomewuia sp. 1 have been 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 significant cooling at the Eocene–Oligocene boundary, the climatic conditions became warm and humid again, as evidenced by the distribution of mesophytic coniferous-broadleaf forests with hickory. In the second half of the Early Oligocene, the climate became colder and more humid, and the content 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 forests. At the very end of the late Oligocene, the climate became more humid again, but remained warm, and pine forests dominated 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 dominance of conifers in forests; in the Early Miocene, the content 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, the open plant communities were formed.