Oligocenian foraminifera of Western Siberia and other regions. Problem of the Latdorfien stage

The sharp different in lithology and microfauna between Nurolskaya and Tavdinskaya suites of Western Siberia have been explained the interruption in sedimentation. This interruption may be created by action of the Alpien tectonic movement. The quartz-siliceous of foraminiferal shells in Nurolskaya suite have been changed on calcareous ones in Tavdinskaya suite. Radiolaria have absent not only in this suite of Western Siberia but in the different stratons of Northern Europe. On the base of characteristic foraminiferal species the age of Tavdinskaya suite was dated as Rupelian one. The uppermost layers of Nurolskaya suite have included single and less diversity Foraminifera. They have been remained from distraction in single depressions of Western Siberia. These layers may be offer to the beginning of Latdorfien stage. Upper layers of Latdorphien stage have taken out from Oligocenian section. On the base of foraminiferal species Tavdinskaya suite correspond to Rupelian stage of Middle Oligocenian. The Foraminifera from Tavdinskaya suite are the same as ones in many other regions: Europe, Atlantic Ocean, USA and other regions. Lower Oligocenian (Latdorfien stage) including zone or layers with characteristic foraminifera has been observed in Middle, South Europe, Crimea and Middle Asia. Nevertheless Latdorfien stage was excluded from Comman Stratigraphic Scheme. In Tavdinskaya Suite of Western Siberia in jeneral secretic - calcareous Foraminifera spread as Cibicidoides pseudoungerianus, Evolutononian Assemblage [Podobina, 1998, 2009]. This Assemblage includes characteristic Bentic and Plantonic species. Among them are Cibicidoides pseudoungerianus (Cushman), Nonionellina oligocenica (Cushman et Mc Glamary), N. ovata Brotzen, Evolutononium decoratum (Cushman et Mc Glamary), Cribroelphidium perrarum Uschakova, C. parainvolutum Uschakova, Elphidiella vegrandia Uschakova, E. nitida Podobina, E. cosmica Uschakova. Among of planktonic species are Paragloborotalia postcretacea (Mjatliuk), P. anguliofficinalis (Blow), Turborotalia perfecta Podobina, Globigerina ouachitaensis Howe et Wallace gnaucki Blow et Banner, G. angustiumbilicata Bolli, G. ampliapertura Bolli, G. senilis Bandy, G. prasaepis Blow, G. officinalis Subbotina praesentata Podobina [Podobina, 1998]. Foraminifera from stratotipe of Rupelian stage have been studied from specimens of Belgium quarries. Author have took part in field excursion (Symposium on Paleogene, August, 25-30, 2003 years, t. Leven, Belgium). Foraminifera Assemblage has been established by auther in stratotype of Rupelian Stage (near town Boom). Common and characteristic in West Siberian and Belgium species are Cibicidoides pseudoungerianus (Cushman), Evolutononion decoratum (Cushman et Mc Glamary), Nonionelina oligocenica (Cushman et Mc Glamary) and species from Globigerina genera. Among them auther have defined Globigerina ouachitaensis Howe et Wallace, G. juvenilis (Bolli), G. officinalis Subbotina praesentata Podobina, G. amliapertura Bolli. Elphidium and Bulimina have not been established in Belgium Assemblage [Podobina, 2009]. Many of Planktonic species of Middle Oligocenian know in the same deposits, except Belgium, in Poland, Prekarpatie, Trinidad, South Atlantic Ocean and Western Siberia. The findings of Globigerina ampliapertura Bolli in Tavdinskaya suite of Western Siberia have big impotence, because have been included in known Middle Oligocenian zone. This species in Tavdinskaya suite shows on the presence of such zone of Middle Oligocenian (Rupelian Stage). West Siberian Cibicidoides pseudoungerianus, Evolutononion decoratum Zone correspond to age of Belgien Rupelian one. Also this West Siberian zone correspond to Rupelian Globigerina ampliapertura one of Trinidad, Atlantic Ocean and other Regions.

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