Home – Home – Jornals – Russian Geology and Geophysics 2005 number 5

Callovian and Late Jurassic zonal biostratigraphy and evolution of foraminifers in West Siberia have received better constraints from the foraminiferal taxonomy in newly studied sections and from revised earlier data. The evolution stages of foraminifers, each beginning at the onset of a Boreal transgression, were inferred from species diversity within zones and from changes in their coeval assemblages in different geographic regions of West Siberia. The boundaries between stages are marked by migration of generic and specific taxa into the West Siberian sea. Taxonomic diversity was used as an additional criterion in division and correlation of sections. Generic variations within the studied time span were associated with dramatic abiotic events which were apparently controlled by eustatic transgressions and regressions. Invasion of species- and genus-ranked migrants into the West Siberian Sea marks the borderlines between the stages. The peaks and dips of taxonomic diversity curves for the studied benthos assemblages show good correlation among different regions of West Siberia and with their counterparts in the Russian Platform and northern Central Siberia.