A case for formalizing subseries (subepochs) of the Cenozoic Era

Subseries/subepochs (e.g., Lower/Early Eocene, Upper/Late Pleistocene) have yet to be formally defined despite their wide use in the Cenozoic literature. This has led to concerns about the stability of their definition and uncertainty over their status that has led to inconsistencies in capitalization. To address these issues, we propose for the Cenozoic that subseries/subepochs be defined formally by reference to Global Boundary Stratotype Sections and Points and ratified in the same way as for other formal chronostratigraphic units. Formalization of subseries/subepochs for the Cenozoic will respect their deep historical roots, recognise their chronostratigraphic nature, stabilize their definition, ensure consistency in application, embrace their de-facto use as formal terms within the Paleogene, Neogene and especially Quaternary communities, and resolve the question of capitalization: an upper-case initial letter without exception.