Biostratigraphy of the Bajocian-Bathonian boundary interval in northern Siberia: new data on belemnites from the Yuryung-Tumus peninsula

摘要

This paper presents a refined belemnite based biostratigraphy for the Bajocian-Bathonian transition in the Yuryung-Tumus peninsula (northern Siberia, Russia). A revision of the Siberian belemnite zonation is proposed. Herein two new belemnite biostratigraphic units are introduced: the Paramegateuthis subishmensis Zone (upper part of the Lower Bajocian) and the Paramegateuthis ishmensis Zone (Lower-Middle Bathonian boundary interval). Paramegateuthis subishmensis STOYANOVA-VERGILOVA, recorded for the first time in Siberia and previously only known from Bulgaria (Sub-Mediterranean domain), provides evidence for correlation of both the Boreal Boreiocephalites borealis and Cranocephalites gracilis ammonite zones with the standard Stephanoceras humphriesianum Zone. The new biostratigraphic data also result in an improved correlation based on belemnites for the Lower-Middle Bathonian of the Boreal (Siberia, North European Russia) and Subboreal (Central Russia) regions.