On the Problem of Nonmarine Cretaceous Strata Correlation in the Northeast Russia: The Conditions of Florogenesis in Volcanic Areas

Resumo

The majority of fossil floras from Cretaceous volcanogenic rocks of Northeast Russia considerably differ in taxonomy from the coeval paleofloras of coastal lowlands. In order to explain the peculiarities of their formation, we used the data on the modern vegetation dynamics for volcanic plateaus of Central Kamchatka. It is shown that there was virtually no erosion where paleofloras of the Okhotsk-Chukotka volcanogenic belt, represented in the burials, existed; however, volcanogenic material, suitable for burials to form, was supplied in abundance. After massive eruptions, inner parts of the vast volcanic zone appeared to be isolated from sources of diaspores. Vegetation cover in these areas was restored mainly owing to the pool of local taxa; i.e., it was supported as a diasporic subclimax. The absence of concurrent angiosperms favored the long-term preservation of ancient taxa in these paleofloras and the appearance of new taxa on their basis.