Lower Jurassic and Aalenian deposits are widespread in the Arctic Basin and in northwestern Europe. The succession of Lower Jurassic lithologic units is very similar throughout the Arctic regions. The Lower Toarcian is represented by dark-gray, organic-rich mudstones and often bituminous mudstones developed uniformly over the whole area. All deposits contain rich assemblages of foraminifers, ostracods and palynomorphs, as well as less abundant ammonites and bivalves, providing a mean for correlation of the lithologic units. The established Jurassic zonal subdivisions have been studied in all areas of the Arctic Basin using original material as well as published data. Thus, the Jurassic zonal subdivision of northern Siberia, based on ammonites, bivalves, foraminifers and ostracods, may be considered as the Boreal Zonal Standard. The analysis of biotic and abiotic events as well as the geographic distribution of microbenthos result in the definition of biogeographic realms and provinces based on foraminifer and ostracode data for the Early Jurassic and Aalenian. The differentiation of microbenthos associations is based on the multivariate analysis of characteristic taxa. The configurations of the boundaries between provinces and realms, based on the geographic distribution of the different groups of benthos, changed during geological time.
High resolution stratigraphy of the Lower Jurassic and Aalenian of Arctic regions as the basis for detailed palaeobiogeographic reconstructions