Carboniferous ammonoid genozones

Abstract

Abstract Considerable progress has been made by international teams in refining the traditional ammonoid zonation that remains the backbone of Carboniferous stratigraphy. The Carboniferous ammonoid genozones, with a few gaps, are now recognized throughout the entire system in most successions worldwide. Refined collecting and documentation of occurrences in Western Europe, North Africa, the Urals, China and North America aimed to establish the first evolutionary occurrences, and facilitated correlation with foraminiferal and conodont scales for most of the Carboniferous. From ten to eleven ammonoid genozones are now recognized in the Mississippian, and eight to nine genozones in the Pennsylvanian. Of these, the established lower boundaries of the subsystems are reasonably well correlated with the ammonoid zonation, whereas correlations with the ratified foraminiferal-based lower boundary of the Visean and other stage boundaries, currently under discussion, need further research. Future success in the ammonoid geochronology will also depend on accurate identification and re-illustration of the type material, including material described by pioneers of ammonoid biostratigraphy.