Abstract:
Ten spore-and-pollen assemblages and nine phytoplankton assemblages (dinocysts, green algae, acritarchs) are distinguished in upper Sarmatian-lower Kimmerian deposits of the reference section situated in the Zheleznyi Rog area of the Black Sea region. Palynological spectra of two types (forest and forest-steppe) were found to alternate throughout the section. Their composition and structure reflect climatic fluctuations, primarily the humidity changes. During humid phases, conifer (Pinus, Taxodiaceae) and mixed broad-leaved (Carya, Ulmus, Quercus) forests dominated, whereas xerophilous herbaceous-fruticose vegetation (Chenopodiaceae, Artemisia, Gramineae) prevailed during the more arid phases. A temperature decrease, most considerable in the studied stratigraphic interval, is recorded in the early Kimmerian that is evident from the increased percentage of Sphagnum spores and Betula and Ericaceae pollen in the spectra. The decrease did not exceed however thermal parameters characteristic of the warm-temperature climate and did not change it. Most significant changes in assemblages of the organic-walled phytoplankton are distinguished at two levels: in the lowermost and uppermost Pontian. The Pontian assemblage of organic-walled phytoplankton taxa Galeacysta etrusca, "Gonyaulax digitalis," Spiniferites bentorii and peculiar Impagidinium, is found to appear 8-10 m above the top of coupled diatomite layer, along which most geologists draw the boundary between the Maeotian and Pontian in the section. The assemblage is correlative with the dinocyst association from an upper part of the Messinian deposits in Italy (Lago Mare facies). In addition to taxa mentioned above, new forms, which are tentatively referred to the Komewuia genus, appear in the organic-walled phytoplankton assemblage of the upper Pontian and lower Kimmerian deposits. Data on salinity changes in paleobasins are discussed as well.
