Original paper

The Position and Correlation of the Boundary between the Proposed Mississippian/Pennsylvanian Subsystems

Higgins, Alan C.

Abstract

Two important changes are seen in the conodont sequence of the Namurian. One occurs at the base of the Chokierian Stage (H1) where the genus Declinognathodus appears and the other at the base of the Kinderscoutian Stage (R1) where the genus Idiognathoides makes its first appearance. The appearance of Declinognathodus may also coincide with the disappearance of the important genus Gnathodus particularly in basin fades environments, but in some parts of the world there is an overlap in their ranges. Of the two events the earlier one, at the base of the Chokierian Stage, is the more important, and it is suggested that the base of the Chokierian should be chosen as the boundary between the proposed Mississippian/Pennsylvanian subsystems rather than the base of the Kinderscoutian as suggested by BOUROZ et al. (1978).