Original paper

Early Eocene marine planktonic record of the East Urals margin (Sverdlovsk region): biostratigraphy and paleoenvironments

Oreshkina, T. V.; Aleksandrova, G. N.; Kozlova, G. E.

Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 234 Heft 1-3 (2004), p. 201 - 222

36 references

published: Dec 22, 2004

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ArtNo. ESP155023400005, Price: 29.00 €

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We have carried out an integrated study of siliceous planktonic groups (diatoms, silicoflagellates, radiolarians) and marine palynomorphs from the ca. 30 m thick Lower Eocene Irbit Formation on the eastern slope of the Urals. We have established the succession of regional diatom zones: (i) Moisseevia (= Coscinodiscus) uralensis/Hemiaulus proteus, (ii) Coscinodiscus payeri, Pyxilla gracilis; regional radiolarian zones: (i) Petalospyris foveolata, (ii) Petalospyris fiscella, (iii) Petalospyris aphorma-Heliodiscus lentis, (iv) Heliodiscus inca; dinocyst zones: (i) Deflandrea oebisfeldensis and (ii) Wetzeliella meckelfeldensis Zones of Northern Europe (Heilmann-Clausen & Costa 1989), corresponding to the NP10-NP12 biochrons. The changes in the ecological structure of planktonic assemblages and depositional cycles enabled us to recognize 5 phases in the evolution of the basin: phase 1 - abnormal neritic environments with increased continental run-off, freshwater influx, and water stratification, evidently corresponding to post-CIE time; phase 2 - start of the transgression, invigoration of circulation within the basin; phases 3 and 4 - increase of coastal upwelling and predominance of siliceous over organic-walled plankton due to the development of well oxygenated conditions; phase 5 corresponds to the onset of a new transgressive event.


Die Untersuchung der kieselschaligen planktonischen Mikrofossilien (Diatomeen und Radiolarien) sowie der marinen Palynomorphen (hauptsächlich Dinozysten) in der untereozänen Irbit-Formation des Ostabhanges des Urals gestattet detaillierte Zonierungen und eine Rekonstruktion der Ablagerungsbedingungen.


siliceoussilicoflagellatesevolutionmarine palynomorphs