Algae as indicators of a biogeographical zonation in the early carboniferous of the Urals,Siberia and Northeast Russia

Summary Algal assemblages of the Urals and Siberia belong to two biogeographical belts: The equatorial Mediterranean and the Siberian belt. They differ in the composition of their agla floras. The end of the Famennian and the beginning of the tournaisian were indicated by smaller differences due to short-term connections of the basins which lie in different climatic belts. The development of the microfloras of the Urals and Siberias during the late Tournaisian exhibits two different trends. These differences were intensified during the Visean and reached their climax in the Serpukhovian. In general, redalgae, especially Stacheinaceae, were predominant in the late Carboniferous basins of the Urals. The Visean and Serpukhovian algae of Siberia comprising usually more than 20 genera (e.g.Calcifolium, Fasciella, Ungdarella) were widely distributed in the Urals as well as in other provinces of the Mediterranean belt. The biogeographical zonation based on the study of algal floras confirms the existence of an Eurasian realm in the Mediterranean belt and several Siberian provinces as well as an intermediate Taimyr-Chukotkian area, which had already been postulated from earlier foraminiferal studies. All of these provinces exhibit distinct features in the development of their algal associations, e.g. the Kolyma-Omolon province is characterized by its predominance of green algae, while in the Altai-Sayan and the Verkhoyansk provinces red algae prevail. These characteristic trends can be observed over rather long stretches of time.