ALBERT

Description: Pollen analysis of two cores from the bottom of the Adriatic sea (Adr. 309, -929 m, 41°49.1' N, 17°11.4' E and Adr. 353, -1207 m, 42°07.2' N, 17°38.0' E) has shown that a period with high Pinus and Artemisia values and an intermediate one with much Pinus, but little or almost no Artemisia pollen was followed by a period with a dominance of thermophilous deciduous trees, among them mediterrenean species. These changes of the pollen flora reflect the change from an open, but not treeless vegetation of late Würmian age (= last glacial period) to a postglacial forest vegetation (intermediate and final phases). This dating is essentially the same as the one given by van Straaten (1966) when studying the mollusc fauna of the same cores. A comparison of the marine pollen spectra with same-age continental ones allows to estimate the effect of the different ability of each pollen type to flotate in salt water, of reworking of pollen by erosion, turbidity currents and benthonic animals, and of the samples preparation method (flotation with ZnCl2-solution) on the pollen content of marine samples. Mesozoic sporomorphs and earlypleistocene pollen has been found only occasionally. Larger quantities of probably reworked pollen were stated in samples from glacial age pollen zones and turbidites only. Pollen frequency was greater in turbidites than in normal sediment. Turbidites also contain more pollen of thermophilous taxa. Pinus is apparently overrepresented in all samples, and flotation with ZnCl2-solution may cause an underrepresentation of certain pollen types (e.g. of Juniperus and Gramineae). Ash layer 5 has been sedimented at a time when fundamental changes of the vegetation were taking place, and thus can serve as a guide horizon. Pollen analysis of marine sediments can very well detect the basic lines of vegetation development of vast areas. It is, however, not qualified for the study of detail problems of vegetation history.