Of or of the previous of this two divisions of Precambrian time, from roughly 3.8 to 2.5 billion years back, noted by an atmosphere with little free oxygen, the formation of the very first rocks and oceans, plus the growth of unicellular life. See dining table at geologic time.
Of or relating to the oldest known stones, those of Precambrian Eon, which can be predominantly igneous in composition.
of or concerning the earliest recognised rocks formed through the Precambrian Eon
The Archean Eon. Also called Archeozoic.
the time from 3,800 million many years to 2,500 million years back; planet's crust created; unicellular organisms are first kinds of life