Definitions for "Proterozoic"
Keywords:  precambrian, eon, ago, era, geologic
The second of two eons in the Precambrian period, lasting from 2500 to 570 Ma. It is preceded by the Archean eon and followed by the Phanerozoic eon, and is comprised of the Early (2500-1600 Ma), Middle (1600-900 Ma), and Late (900-570 Ma) eras. It is characterized by the earliest forms of life on earth.
Rocks formed between 2,500 and 600 million years ago.
The later part of Precambrian time (2500-590 million years ago).