Late Miocene Palaeoclimate and Ecosystem Dynamics in Southwestern Bulgaria − A Study Based on Pollen Data from the Gotse-Delchev Basin

Authors: DIMITER A. IVANOV, TORSTEN UTESCHER, A. RAHMAN ASHRAF, VOLKER MOSBRUGGER, VLADIMIR BOZUKOV, NADEZHDA DJORGOVA, EVGENIA SLAVOMIROVA

Abstract: A profile 63 m thick in the Late Miocene in the Gotse-Dechev Basin (SW Bulgaria) was sampled for pollen analysis in the Kanina opencast mine. The exposed sequence comprises a basal unit with brown coal-clay cycles and clayey/siliciclastic cover layers partly representing a lacustrine facies. A total of 60 pollen samples were analysed, but quantitative data are confined to 30 polleniferous samples. The palynological analysis carried out provides data about the composition and structure of the fossil vegetation. The main vegetation type was a mixed mesophytic forest dominated by Carya, Fagus, Betula, Quercus, and Ulmus. Accessory elements included Magnolia, Corylopsis, Liquidambar, Eucommia, Zelkova, Ulmus, Pterocarya, Juglans, Engelhardia, Platycarya, Symplocos, Araliaceae, Vitaceae, Hedera, Cornus, and Ilex. Mid- and high-altitude vegetation elements Tsuga, Abies, Keteleeria, Cathaya, Picea, Cedrus are also present. Swamp vegetation with high proportion of Alnus, and minor percentages of Taxodiaceae, Cyrillaceae, Myrica, Planera, some Poaceae, Cyperaceae, and some ferns also existed. Species of Platanus, Alnus, Pterocarya, Salix, Staphylea, and Liquidambar played important roles in the riparian vegetation. The aquatic vegetation consists of Butomus, Potamogeton, Menyanthes, Sparganium, Typha and Cyperaceae. Herbaceous palaeocoenoses had a limited distribution. The climatic data reconstructed by the Coexistence Approach indicate mean annual temperatures of ca. 15.6-17.1°C. For mean annual precipitation intervals from 1096 to 1347 mm are most common. The narrowest coexistence intervals for the mean of the coldest month are 5 to 7.5°C. Summer temperatures were mainly between 24.7 and 26.4°C. The curve obtained for the means of summer temperatures illustrates some cyclic changes, partly also observed for other temperature parameters. The dynamics of the reconstructed data indicate that the climatic changes were probably cyclical. However, the presence of several unconformities in the sampled section does not allow an unambiguous interpretation of these data.

Keywords: Late Miocene, Bulgaria, Southeast Europe, palynology, vegetation, climate, Coexistence Approach

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