Grassland development reconstructions were based on the study of some soil profiles, located in different part of the islands from different floristic district (Figure 1). The study of the sections include pollen analysis, radiocarbon dating and tephrostratigraphy. The samples for the pollen analysis was treated with the standard KOH and acetolysis method, pollen grains were concentrated by means of the heavy-liquid flotation method . Three pollen sums were calculated: total arboreal pollen, total nonarboreal pollen, and total spores. The percent of each taxon is calculated for these groups. 14C dates were produced by liquid scintillation counting in the Geological Institute, RAS, Moscow (Table). The samples were treated with standard acid and alkali solutions. The calibrations of 14C dates were made using the calibration program OxCal 3.9 [8, 45].
In paleoreconstructions we used non calibrated 14C yr for more a correct correlation with the available paleogeographical data collected in surrounding regions. The correlation of ash layers is based on 14C dates from under- and overlying deposits, on refractive indices and morphology of volcanic glass shards, and on mineral composition and chemical composition of volcanic glass (V.G. Khlopin's Radium Institute, St. Petersburg).
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