THE GEOZOIC: AN INFORMAL SUPEREON AND A TERMINOLOGICAL CONVENIENCE

The term “Geozoic” is proposed as a new informal geochronologic/chronostratigraphic unit defined by the time interval of existence of life on our planet. The lower boundary of this unit is defined biostratigraphically by the oldest direct evidence for presence of life on Earth. The upper boundary is the present time (life is still around on our planet). The term Geozoic is chronostratigraphically synonymous with the expression “the entire fossil record” and geochronologically synonymous with the expression “the entire documented history of life.” Geozoic encompasses multiple eons (i.e., most of the Archean, the entire Proterozoic, and all of the Phanerozoic) and merits a geochronological rank of informal supereon. The time from the formation of the Earth until the oldest direct evidence of life (i.e., the Hadean and the early Archean) can be referred to as “Pregeozoic,” thus dividing the earth’s history into two informal supereons. Geozoic, defined by one of the most important events in the history of our planet (i.e., the appearance of life), reflects a more fundamental subdivision than the currently accepted and widely used informal supereons that split the Earth’s history into two time intervals of “non-visible” (Precambrian/Cryptozoic) and “visible” (Phanerozoic) life. The terms “Geozoic” and “Pregeozoic” are convenient because they represent an expedient way to refer to the geological processes, patterns, and records that correspond to the interval of time during which life must have existed on our planet. Because the origin of life must predate the oldest fossilized records of life, the Geozoic supereon represents the most conservative estimate of the biosphere’s existence time.