Astro-Unit-Stratotypes and Astrochronozones as Formal Chrono-stratigraphic Units in Sync with GSSPs?

The rapid progress in astronomical dating over the last decades has sparked a revolution in the Earth sciences regarding our perception of geological time. The resultant astronomical time scales provide the accuracy, precision and resolution needed to reconstruct Earth history and especially that of climate in detail. Today the age calibration of the standard Cenozoic Geological Time Scale (GTS) is based on astronomical dating and the approach is being rapidly extended into the Mesozoic and even the Paleozoic by focusing in particular on the relatively stable long 405-kyr eccentricity cycle. Yet, despite the major progress in astrochronology, formal chronostratigraphy has remained unchanged with its focus on Global Boundary Stratotype Sections and Points (GSSPs). However, the three key arguments of completeness, correlatability and character that were initially in favor of the GSSP only approach and against the use of unit-stratotypes have all been invalidated by the study of deep marine sediments and the associated advancement in cyclostratigraphy and astrochronology. A proposal to formally define astro-unit-stratotypes (AUS) and astrochronozones in addition to GSSPs is currently being reviewed by the International Commission on Stratigraphy (ICS). Astro-unit-strato-types are optimal stratigraphic sections and/or cores that cover an entire chronostratigraphic unit (generally a stage) in a cyclic succession that is continuous and has been astronomically tuned; the tuning ideally underlies the standard GTS for this specific time interval. In addition, astrochronozones linked in particular to the long 405-kyr eccentricity cycle can be formally defined as fundamental building blocks in chronostratigraphy at a smaller scale,in addition to and independent of the stage. Such astrochronozones are unique in the sense that they do not only carry chronostratigraphic significance and are useful for relative time stratigraphic correlations, but also provide the indispensable accurate and precise high-resolution numerical ages through astronomical dating. Integrating the astro-unit-stratotypes and astrochronozones with the GSSPs solves the fundamental problem of the GSSP-only approach by filling the entire stage at a much higher resolution. This increase in resolution enhances the usefulness of the International Chronostratigraphic Chart (ICC) and associated standard GTS by allowing Earth's history to be reconstructed in unprecedented detail.