Late Eocene to early Miocene climate and vegetation of Bulgaria

Hygromesophytic forests without arctotertiary floristic elements still played the major role in the zonal vegetation in the late Eocene. No significant change in vegetation cover at the Eocene/Oligocene transition is apparent, and hygrophytic to hygromesophytic palaeocoenoses and oak-laurel forests dominated the palaeovegetation. Mesophytic to mesoxerophytic communities became important in the early Oligocene, along with the decrease of hydrophytic to hygromesophytic formations. A similar picture is obtained for the late Oligocene, but deciduous arctotertiary elements then reached a higher proportion for the first time. The climatic evolution is more or less consistent with the observed vegetation changes. Warm-temperate conditions persisted throughout this time span, but they show a cooling trend in the late Oligocene, most probably an imprint of global climatic cooling at that time. With respect to changing palaeogeographical patterns, the regressive trend during the early Oligocene is contemporaneous with a slight decrease in annual precipitation. Xerophytic phytocoenoses are reported from most of the sites, but climatic data supporting the existence of such associations are reconstructed only for the Bourgas and Borovets floras. In all the other floras, the majority of taxa indicate that no really dry season existed.