Miocene vegetation and climate dynamics in Eastern and Central Paratethys (Southeastern Europe)

From the Cretaceous to modern time the earth's climate system has changed repeatedly from a greenhouse to an icehouse. The Miocene appeared as the last warm episode in earth history, prior to the establishment of large Northern Hemisphere ice sheets. Furthermore, the Miocene was characterized by both, large-scale marine transgressions and pronounced episodes of regressions, e.g. opening and closure of marine corridors as well as appearance and disappearance of lakes and swamps. The sea-level changes and instability of the climate system strongly influenced not only marine ecosystems but also the terrestrial biota. To throw new light on the Miocene evolution of European ecosystems and climate dynamics, we compared plant assemblages from southeastern Europe. Palaeogeographically this area is a transitional belt between Tethyan and Paratethyan realms, and it thus constitutes a crucial geographical position when one tries to comprehend the exchange pathways of various floristic elements, appearance and evolution of steppe vegetation, interaction between forest and steppe vegetation, and of course the corresponding climates influencing the vegetation dynamics. Both macro- and microfloristic plant associations were considered in our analysis. Large palaeofloristic and palaeocoenotic transformations occurred during the Miocene. The Early to Middle Miocene flora is rich and diverse in thermophilous elements, which formed polydominant mesophytic to hygromesophytic forests. Early Miocene climate was warm and humid with mean annual temperatures mainly above 16 degrees C and annual rainfalls over 1000 mm. The Middle Miocene was the warmest period of the whole Miocene, with annual temperatures ranging from 17 degrees C to 19 degrees C and winter temperatures from 7 degrees C to 12.5 degrees C. Climatic changes after the Miocene climatic optimum caused changes in floristic composition and vegetation structure. The vegetation shows a decreasing trend in abundance of palaeotropic and thermophilous elements, reduction of macrothermic elements, and disappearance of evergreen laurel forests. Together with these changes is a corresponding increase in the role of arctotertiary species in plant communities, and they became dominants in mesophytic forests. The available data indicate that major vegetation changes occur in the late Miocene. This period is characterized by more diverse climatic conditions, which were directed by global climatic changes and probably complicated by regional palaeogeographic reorganizations and tectonic processes. Slight cooling and some drying is recorded for the beginning of the Late Miocene, followed by fluctuations of palaeoclimate parameters observed which display cycling change of humid/dryer and warmer/cooler conditions. Our study provides a new insights on the Miocene vegetation and climate dynamics and evolution in Southeastern Europe. (C) 2010 Elsevier B.V. All rights reserved.