Sub-series and sub-epochs are informal units and should continue to be omitted from the International Chronostratigraphic Chart

In June 2016 the Paleogene, Neogene, and Quaternary subcommissions (ISPS, SNS, SQS) of the International Commission on Stratigraphy (ICS) voted on whether to formalize sub-series and their geochronologic equivalents, sub-epochs. The vote required a 60 percent majority for the proposal to be forwarded to the ICS for further consideration. That majority was not achieved, albeit by a narrow margin, hence sub-series and sub-epochs are currently to be regarded as informal, and if used should carry a lower case modifier, as in lower Miocene and early Pleistocene. To accompany the vote, those who favoured continuation of informal usage were asked to prepare a short summary of the main arguments in support of their viewpoint, as were the proponents of the formalization case. Although this statement was not originally intended for publication, it is reproduced here at the request of the Former Chair of the ICS, so as to put it on record.