Chronostratigraphic grounds for the decision against formalizing an Anthropocene Epoch

The Anthropocene is widely discussed across the Earth sciences, yet its status as a potential formal epoch of the Geological Time Scale remains contested. In 2024, the International Commission on Stratigraphy (ICS) declined the proposal to establish a mid-twentieth-century boundary anchored in artificial radionuclide fallout. Despite extensive discussion, few analyses have evaluated this outcome against the operational requirements of chronostratigraphy. This paper examines the scientific basis of the decision in light of the formal criteria applied to epochal definition. We review the conceptual foundations of chronostratigraphy, summarize the structure of the Anthropocene dossier submitted by the Anthropocene Working Group, and assess the stratigraphic reasoning applied during ICS evaluation. We develop a dual-register framework that distinguishes the systemic domain of Earth-system transformation from the stratigraphic domain of boundary definition, and use it to assess whether mid-twentieth-century anthropogenic signals meet ICS chronostratigraphic requirements for Epoch ratification. On this basis, we argue that the submission does not demonstrate cross-archive operational correlatability under ICS criteria. In the proposal, radionuclide horizons display variable stratigraphic expression across depositional systems; auxiliary markers are proxy-specific; even when widely detectable (e.g., SCPs), auxiliary markers function primarily as supporting indicators because their expression is archive-dependent and does not, by itself, fix an operationally equivalent boundary level across settings; and the Crawford Lake candidate, although exceptionally resolved, is defined in a lacustrine varved succession, complicating operational correlatability across heterogeneous archives. These findings indicate that systemic change does not, by itself, establish an operationally correlatable boundary. The Anthropocene remains a useful framework for describing Earth-system change, but under ICS criteria the proposed boundary is not shown to meet Epoch ratification requirements. • The rejection of the Anthropocene Epoch is evaluated within a chronostratigraphic framework. • A dual-register framework separating systemic and chronostratigraphic domains is developed. • Mid-20th-century radionuclide fallout lacks stratigraphic uniformity. • Crawford Lake is high-resolution but environmentally unrepresentative as a GSSP candidate. • The Anthropocene remains an Earth-system descriptor rather than a formal epoch.