Место издания: Florence , Год издания: 2004

Jurassic deposits are wide-spread in the Arctic. The Jurassic is almost entirely represented by terrigenous sediments over this vast territory. The Upper Jurassic is one of the main targets for oil and gas production in the West Siberia, Northern Alaska and Canadian Arctic. The study of the Upper Jurassic from the outcrops and numerous wells in the northern regions of Siberia characterized by numerous ammonites allows the precise determination of the boundary between foraminiferal assemblages according to the ammonite zonation. During the past several years Upper Jurassic zonation of Siberia based on foraminifers has been improved, detailed and correlated with the Boreal ammonite standard. Concurrent-range zones, biozones, ecozones or complex parallel phylozones have been used to develop foraminiferal zonation. At the same time, zones of narrow and wide ranges, characterized by different foraminiferal assemblages in various facies, have been defined. Micropalaeontological study of numerous Upper Jurassic sections of Northern Alaska, allows establishing the succession of foraminiferal zones similar to Siberian one. Therefore the stratigraphic analysis of foraminiferal assemblages provides the reliable definition of the stratigraphic range of sandy reservoirs of Kingak Formation. The studying the microfossils of Arctic Canada Canadian micropalaeontologists revealed the significant similarity of taxonomical composition of Upper Jurassic foraminifers of Canadian Arctic and Western Siberia. Upper Jurassic foraminifers of Frantz Josef Land and Svalbard were studied by Russian and Norwegian micropalaeontologists for a long period. The published data on layerwise stratigraphic distribution of Upper Jurassic foraminifers allow to follow here some Siberian foraminiferal zones. The foraminiferal assemblages of northern regions of North-West of Pechora basin are rather specific. They comprise both Siberian and southern elements that result in alternation of local and Siberian assemblages in foraminiferal succession of this region. Thus, Upper Jurassic foraminiferal zonations developed from northern regions of Siberia sections is traced over the whole Arctic basin. Therefore Upper Jurassic zonations based on foraminifers established for northern Siberia can be considered as an Arctic zonal standard. Moreover, a number of marker-levels, based on microfossils have been traced which allow us to correlate Arctic and European microfossil zonations of Upper Jurassic age.