An analysis of the evolutionary distribution of diatoms in the outcrops of the Late Cenozoic shows that, upon reaching the level of the Annensky Horizon (Gelazian stage), the extinct species disappear almost completely. A predominance of the alluvial type of sedimentogenesis and reduction in the lake basins areas are clearly registered for deposits of the diatom zone Aulacoseira praegranulata var. praeislandica f. praeislandica. A cooling in the Late Pliocene with the pronounced temperature minimum at the level about 2,58 million years is fairly bright reflected in the ecological structures of diatomic associations (upper complex): the benthic arcto- and north-boreal flora predominates. Of that time, a total absence of the pollen of the broad-leaved species is also characteristic and paleo-landscapes become close to the Eopleistocene ones. From this moment on, the coexistence and expansion of the polar ice sheets begin (transition of planet from the “Green house” mode to the “Ice house” mode) which determine the formation of the modern climatic system of the Earth which emphasizes the globality of the palaeoclimatic event. From the lithological point of view, the bottom of the red rocks strata of the Annensky Horizon corresponding to the Gelazian stage bottom (2,58 million years) coincides with this boundary in the southern Primorye. The age changes of the Quarter boundary to this chronostratigrahic level is well founded.
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