First report of the Jurassic-Cretaceous boundary (Northwest Europe) Working Group (I.U.G.S. Cretaceous Subcommission)
published: Jul 25, 1975
The Working Group recommends that the lover limit of the Cretaceous System should be drawn at the base of the Riasanites rjasanensis Zone and its equivalents (presumably, e. g. the Fauriella boissieri Zone of southeast France and the Runctonia runctoni Zone of eastern England). Because of the occurrence of both Tethyan and Boreal ammonites at that level in a thick depositional succession in the northern Caucasus and adjoining regions, the most promising area for selection of the limitotype section appears to be the southern USSR.