Paleoproterozoic

Proposed redefinition(s)2420–1780 Ma
Gradstein et al., 2012
Proposed subdivisionsOxygenian Period, 2420–2250 Ma

Gradstein et al., 2012
Jatulian/Eukaryian Period, 2250–2060 Ma
Gradstein et al., 2012
Columbian Period, 2060–1780 Ma

Gradstein et al., 2012
EtymologyName formalityFormalAlternate spelling(s)PalaeoproterozoicUsage informationCelestial bodyEarthRegional usageGlobal (ICS)Time scale(s) usedICS Time ScaleDefinitionChronological unitEraStratigraphic unitErathemTime span formalityFormalLower boundary definitionDefined ChronometricallyLower GSSA ratified1990Upper boundary definitionDefined ChronometricallyUpper GSSA ratified1990

The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoiceon, and also the longest era of the Earth's geological history, spanning from 2,500 to 1,600 million years ago (2.5–1.6 Ga). It is further subdivided into four geologic periods, namely the Siderian, Rhyacian, Orosirian and Statherian.

Paleontological evidence suggests that the Earth's rotational rate ~1.8 billion years ago equated to 20-hour days, implying a total of ~450 days per year. It was during this era that the continents first stabilized.