ON THE POSITION OF THE BOUNDARY BETWEEN THE MOSCOVIAN AND KASIMOVIAN GLOBAL STAGES OF THE CARBONIFEROUS IN THE DONETS BASIN

Abstract

Detailed new data on paleontology and stratigraphy were obtained in the process of fulfilling the tasks of the International Carboniferous Subcommission on definition of the scopes of the Moscovian and Kasimovian global stages and the precise position of the boundary between them. The analysis of these data has shown that the position of this boundary in the type  area and in the other regions needs the revision. Recently the investigation of the conodonts from the Moscovian–Kasimovian boundary deposits in the Donets Basin revealed that the boundary between the Moscovian and Kasimovian stages in the official Ukrainian Carboniferous Stratigraphic Scheme does not correspond to this boundary in the type area of these stages in the  Moscow Basin. To correct this situation the lower boundary of the Kasimovian in the Ukrainian Scheme must be downgraded by two conodont zones — Swadelina subexcelsa and Sw. makhlinae. To update this boundary in the type area to fulfill the task of the Carboniferous Subcommission four conodont species were proposed as potential index-species for the definition of the boundary between the Moscovian and Kasimovian global stages. These conodont species are as follows Sw. subexcelsa,  Idiognathodus sagittalis, I. turbatus and I. heckeli. One of these species, which is selected, will be used as a marker of the  studied boundary. None of these species is officially selected as a marker. If Sw. subexcelsa will be selected, the position of  the Moscovian–Kasimovian boundary will remain at the present position. In this case this boundary in the Donets Basin has to be downgraded by two conodont zones. If one of three Idiognathodus will be selected, this boundary in the type area will be   upgraded by one and a half regional substage. In the Donets Basin it will be upgraded by less than a cycle. Keywords: Carboniferous, stratigraphy, conodonts, extinction event, index-­species.