Trends,transitions, and events in cryptozoic history and their calibration: apropos recommendations by the subcommission on precambrian stratigraphy

Here I examine the semifinal recommendations of the Subcommission on Precambrian Stratigraphy of the International Union of Geological Sciences (Plumb and James). Although stratigraphy is the subject, the stated objective is ‘subdivision of geologic time’. From that the Subcommission derives a potentially workable set of eons, eras, and Proterozoic systems, arbitrarily separated by radiometric numbers seen as having the virtues of objectivity and stability. The time-transgressive transitions that actually separate the broad succession of prevailing stratigraphic and historical modes thereby become fixed, globally synchronous ‘boundaries’ by decree. What kind of stratigraphy is that?Apart from its essential role in calibration, what does geochronometry have to do with stratigraphy and historical geology? How do practices proposed reconcile with those heretofore applied? Given radiometric ‘boundaries’, are the numbers chosen the most appropriate? Just how is the system recommended to become ‘useful…to working geologists’?Such reflections lead me to conclude that the proposed ‘geochronometric subdivision’ is mistaken in principle, confining in application, and self-contradictory — particularly as concerns the grossly discordant but historically illuminating transition from the mantle-dominated Archean Eon to continent-dominated Proterozoic history. Such matters are the foci of this brief paper.