Conodonts from Moscovian–Kasimovian Boundary Interval in the Type and Reference Sections, Moscow Basin, Russia

Abstract

The GSSP for the Kasimovian Stage has not been fixed or defined. Several conodont species: Swadelina subexcelsa (Alekseev et Goreva, 2001), Idiognathodus turbatus (Rosscoe et Barrick, 2009) or Idiognathodus sagittalis (Kozitskaya, 1978) and Idiognathodus heckeli (Rosscoe et Barrick, 2013) were proposed and discussed by the Task Group as potential index taxa for the boundary definition. This paper describes the distribution of all potential conodont markers and refines the levels of their appearance in the key sections in the type region of the Kasimovian, considering revision of the previously obtained and new data. The traditional lower boundary of the Kasimovian Stage in the Moscow Basin coincides with the level of FAD of the conodont Swadelina subexcelsa. This species could be traced across large distances, including different continents and could be proposed as a good marker for the Moscovian-Kasimovian boundary. The first occurrences of other species as Idiognathodus sagittalis, I. turbatus and I. heckeli are fixed at the base of the middle member of the Neverovo Formation of the Khamovnikian Substage, i.e. much higher than the base of the Kasimovian that was established for the Carboniferous of Russia. The levels of the appearance of this species have a high potential for the global correlation, but it is not good solution for the definition of the Global Kasimovian Boundary.