Definition and GSSP Selection for the Moscovian Stage (middle Pennsylvanian, Carboniferous): State of the Art

The Moscovian Stage was originally named in the Moscow Basin, Russia, in 1890 and was formally incorporated into the International Chronostratigraphic Chart as a global Carboniferous stage at the beginning of this century. However, its basal boundary has yet to be formally defined, and no Global Boundary Stratotype Section and Point (GSSP) has been established. Since 2002, the “Task Group to establish a GSSP close to the existing Bashkirian–Moscovian boundary” has evaluated numerous conodont and fusulinid taxa as potential biostratigraphic markers. At present, the First Appearance Datum (FAD) of the conodont Diplognathodusellesmerensis Bender within the D. benderi–D. ellesmerensis lineage and the FAD of Declinognathodusdonetzianus Nemirovskaya within the De. marginodosus–De. donetzianus lineage are considered the most promising events for recognizing the Bashkirian–Moscovian boundary and facilitating global correlation. The Naqing section in South China and the Basu section in the southern Urals, Russia, are currently the leading candidate sections for the Moscovian GSSP. Based on current understanding, both Diplognathodus ellesmerensis and Declinognathodus donetzianus are easily identifiable, are phylogenetically constrained, and occur close to the traditional Bashkirian–Moscovian boundary in its type area. Declinognathodus donetzianus has been documented in Western and Eastern Europe, as well as North and South America, but has never been reported from Asia. In contrast, D. ellesmerensis has a much wider geographic distribution, having been found in Western and Eastern Europe, North and South America, North Africa, and East Asia. Therefore, D. ellesmerensis meets the requirements for a boundary marker in a part of the geological column where international correlation is very difficult. Nevertheless, a formal decision on the Moscovian Stage boundary marker is still required from the Subcommission on Carboniferous Stratigraphy. In 2026, a new task group will be convened with the aim of finalizing the GSSP for the base of the global Moscovian Stage. This task group will evaluate the available multidisciplinary stratigraphic data, biostratigraphy, chemostratigraphy, and cyclostratigraphy, among others, to assess potential boundary criteria and develop a consensus proposal for the primary marker. The task group will also review the candidate sections, working toward a formal proposal for establishing the GSSP of the Moscovian Stage that can be submitted to the relevant international bodies for consideration. The task group expects to complete the selection of the primary boundary marker and submit the proposal for the Moscovian GSSP in 2027 and 2029, respectively.