Archean

The Archean Eon (n, also spelled Archaean; formerly Archaeozoic k, also spelled Archeozoic or Archæozoic) is a geologic eon before the Proterozoic Eon, before 2.5 Ga (billion years), or {Ma|2500}. ==Classification issues== Instead of being based on stratigraphy as all other geological ages are, the beginning of the Archean eon is defined chronome...
Found on http://en.wikipedia.org/wiki/Archean

Archean

[adj] - (geology) used of the earliest known rocks 2. [n] - the time prior to 2,500 million years ago
Found on http://www.webdictionary.co.uk/definition.php?query=Archean

archean

archaean adjective used of the earliest known rocks
Found on https://www.encyclo.co.uk/local/20974

Archean

An eon of geologic time extending from about 3.9 billion years to 2.5 billion years ago.
Found on https://www.encyclo.co.uk/local/22327

Archean

Geologic eon that occurred from 2500 to 3800 million years ago. During this time period, the first single-celled prokaryote organisms evolved and developed.
Found on http://www.physicalgeography.net/physgeoglos/a.html

Archean

The oldest rocks of the Precambrian era, older than about 2,500 million years.
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