THE JURASSIC-CRETACEOUS BOUNDARY IN THE BOREAL REALM (BIOSTRATIGRAPHY AND BOREAL-TETHYAN CORRELATION)

Abstract

A systematic analysis of the detailed biostratigraphy of Jurassic-Cretaceous boundary beds in principal regions of Russia is used to ground the correlation model of these deposits. The interregional correlations with respective strata in Europe and America demonstrate the range incompatibility of the terminal Jurassic stages accepted in the Boreal and Tethyan stratigraphic schemes, and suggest that the upper Volgian Substage should be considered part of the Cretaceous System. This means that the Jurassic-Cretaceous boundary in the Boreal Realm ought to be revised and to correspond, in our opinion, to the boundary between the lower and upper Volgian substages. The last level approaches, or is even identical to the accredited position of the Jurassic-Cretaceous boundary between the Tithonian and Berriasian stages.