Paleoproterozoic

The Paleoproterozoic (k; also Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoic occurring between {Ma|Paleoproterozoic|Mesoproterozoic}. This is when the continents first stabilized. Paleontological evidence on the Earth`s rotational history suggests that ~1.8 billion years ago, there were about 450 days in a ye....
Found on http://en.wikipedia.org/wiki/Paleoproterozoic

paleoproterozoic

An era (2500 to 1600 mya) with four periods: Siderian, Rhyacian, Orosirian, and Statherian.
Found on http://www.scientificpsychic.com/etc/geology-glossary.html
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