The Callovian and Upper Jurassic section in the Tyumenskaya superdeep borehole SD-6 (West Siberia) drilled with almost continuous recovery of core (about 200 m) and characterized by rich assemblages of microfossils is a unique object for development and improvement of Jurassic regional biostratigraphic schemes of West Siberia based on microfossils. This paper presents results of micropaleontological and palynological researches (foraminifers, microforaminifers, ostracodes, cysts of dinoflagellates, acritarchs, prasinophytes as borehole as spores and pollen grains of terrestrial plants) and bio- and lithostratigraphic features of the uppermost Middle and Upper Jurassic part of the reference section from the Tyumenskaya superdeep borehole. The Vasyugan, Georgiev, and Bazhenov Formations are described in detail, taking into consideration their micropaleontological and palynological characteristics. The strucural features of sand productive beds of J20 and J1 groups in the Vasyugan Formation and J10 group at the base of the Georgiev Formation are discussed. Comprehensive lithostratigraphic analysis of Callovian-Upper Jurassic part of the section SD-6 and biostratigraphic data allow us to localize the boundaries of some formations, subformations, and beds in this borehole. The stratigraphic and lateral distribution of Callovian and Upper Jurassic formations has characterized and their thickness in the Urengoi district and adjacent territories has been estimated.

Analysis of stratigraphical distribution of microfossil species allows close zoning of reference section SD-6 which is the most complete Jurassic succession in northern West Siberia. The Jurassic regional-scale foraminiferan biostrata (f-zones), some of them being proposed for West Siberia for the first time. Also for the first time, an almost continuous sequence of dinocyst-based biostrata (dinozones) for Callovian-Middle Volgian has been established in a single section. It may form the basis for the development of Jurassic zonal dinocyst scale for West Siberia.

Distinctive features of microbenthos communities and microphytoplankton associations reflecting biofacies have been studied. The pattern of distribution of microbenthic communities and microphytoplankton associations depending on changes of transgressive-regressive events and paleoenvironments in the Callovian-Late Jurassic have been established.

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