Comments on the GSSP for the basal Emsian stage boundary: the need for its redefinition

Abstract

The redefinition of the lower boundary of a traditional stage by means of a GSSP must be adapted as closely as practicable to the traditional boundary level because divergence between the original sense of the stage concept and name and the new GSSP creates confusing nomenclature. The present GSSP for the lower boundary of the Emsian Stage in the Zinzilban section (Kitab Reserve, SE Uzbekistan) is too low in the section to fulfill this requirement. Accordingly, a redefinition of the boundary of the lower Emsian by the International Subcommission on Devonian Stratigraphy (SDS) and the IUGS Commission on Stratigraphy is necessary. A new GSSP must be defined at a higher level and this could be done in strata of the present stratotype area. The stratigraphic correlation of the traditional Lower Emsian boundary and the GSSP is based on Mauro-Ibero-Armorican and Rheno-Ardennan benthic and pelagic faunas.