ABSTRACT: Chronostratigraphic subdivision of the sedimentary rock record should proceed in a bottom up hierarchical manner with lower units defining the boundaries of stratigraphically higher units. Definition of the base of higher order Cenozoic chronostratigraphic units, however, has proceeded in an inconsistent manner over the past 25 years with procedures including essentially ignoring congruent stages (Rupelian/ Priabonian) in the case of the Oligocene, retrofitting stages to series boundary (base Pleistocene, base Miocene), and lowering a stage boundary (Ypresian) nearly 1 my to denote a series boundary (Eocene). Alone among Cenozoic units the base Pliocene was defined by a GSSP for the Zanclean Stage. The inability of INQUA and the Neogene Subcommission to agree on a suitable placement/category for the Quaternary in the Cenozoic chronostratigraphic hierarchy and the stubborn insistence on the part of the former that the chronostratigraphically defined base/GSSP Pleistocene (1.8 Ma) and the climatostratigraphically-defined base Quaternary be moved in tandem to the base of the Gelasian Stage at 2.6 Ma suggests that perhaps it is time to disengage the two groups and remove the Quaternary from the chronostratigraphic hierarchy and allow INQUA (and the community of Quaternary geologists) to function independently of the IGC.

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