eonothem
rank of chronostratigraphic unit representing the totality of rock strata laid down during a certain eon of the geologic time scale
Proterozoic
third eon of the geological timescale, last eon of the Precambrian Supereon
Phanerozoic
fourth and current eonothem and eon of the geological timescale
Hadean
first eon of the geological timescale, beginning with the formation of the Earth about 4.567 billion years ago
Archean
second eon of the geologic timescale, spanning from around 4.031 to 2.5 billion years ago