Should Unit-Stratotypes and Astrochronozones be formally defined? A dual proposal (including postscriptum)

The Global Stratotype Section and Point (GSSP) approach to define stage boundaries leaves the unit or body of the stage undefined. At the same time, previous arguments against the use of unit-stratotypes have been invalidated for the younger Cenozoic part of the geological record through the revolutionary advance in integrated high-resolution stratigraphy and astronomical dating. Combined, these provide unprecedented age control and ensure continuity of sedimentary successions, at least within the time scales of the calibrated astronomical-forced climate oscillations, and offer the possibility to introduce amended unit-stratotypes for global stages. Here we propose that such unit-stratotypes should comprise the entire stage in an astronomically age calibrated deep-marine succession, preferably but not necessarily containing the GSSP. Furthermore, cycles used for the tuning can be formally defined as chronozones, i.e. chronostratigraphic units of either unspecified rank or of a smaller scale than the stage, and independent of the standard hierarchy in global chronostratigraphy. In this way, the standard Geological Time Scale and Global Chronostratigraphic Scale can be brought in line with the progress in integrated high-resolution stratigraphy and astronomical dating. However, the more fundamental formal definition of unit-stratotypes does not depend on the formalization of astrochonozones, and both issues should be separately considered and voted upon.