Paleocene and Eocene floras of Russia and adjacent regions: Climatic conditions of their development

Climatic changes in the western and central regions of Russian Eurasia in the Paleocene and in the first half of the Eocene were caused by the dynamics and rearrangement of the systems of marine seaways: the longitudinal one, which connected the Arctic Basin with marginal seas of the Northern Peri-Tethys, and the latitudinal one, which connected the latter seas with the Atlantic. As these systems were progressively reduced, the climate in the middle latitudes changed from paratropical to a subtropical monsoon climate with a moist summer, and later to a climate with a moist winter, and, in the Late Eocene, to a humid climate without any marked seasonal variation in precipitation. The type of flora changed in agreement with these changes. In the Paleogene, cold currents constantly influenced the climate of the Northwestern Pacific rim and facilitated the development of a warm-temperate mesophilic flora.