4.2.2 Eonothem (Eonotem)
4.2.2.1 The eonothem is the highest-ranking chronostratigraphical unit. The Phanerozoic Eonothem (fanerozoikum) is comprised of three erathems, the Palaeozoic, Mesozoic and Cenozoic Erathems (paleozoikum, mesozoikum, kenozoikum). Older rocks have generally been assigned to the Precambrian Eonothem, but the IUGS Subcommission on Precambrian Stratigraphy has recently proposed the erection of two eonothems for the Precambrian, the Archaean (arkeikum) and Proterozoic (proterozoikum). The division of time corresponding to an eonothem is an eon, and this is given the same name as the corresponding eonothem.