The upper Bajocian-Lower Bathonian of Pechora River basin and Boreal-Tethyan correlation

Distribution of ammonites in the Bajocian-Bathonian boundary beds of the Izhma River basin is considered. A new scheme of zonal subdivisions suggested for the Pechora basin includes the Arctocephalites arcticus Zone of the upper Bajocian and the Arctocephalites greenlandicus-Arcticoceras ishmae Zone of the lower Bathonian. The Dreshchanka Formation age (late Bajocian-early Bathonian) and the commencement time of the Boreal sea transgression (Late Bajocian) are specified. Correlation of the Bajocian-Bathonian boundary strata of the northern Caucasus, central and northern Russia with stratigraphic scales of Western Europe and East Greenland are discussed. New infrazonal subdivisions, i.e., the faunal horizons, are described. As is shown, the parkinsoni-zigzag zonal boundary accepted to be the Bajocian-Bathonian boundary in standard scale corresponds to boundaries separating the michalskii and besnosovi zones in the Lower Volga region and the arcticus and greenlandicus zones in the Boreal areas.