Paleoproterozoic

Paleoproterozoic
Paleoproterozoic
	Paleoproterozoic stromatolites
Chronology
−2500 — – −2400 — – −2300 — – −2200 — – −2100 — – −2000 — – −1900 — – −1800 — – −1700 — – −1600 — –	P ; r ; o ; t ; e ; r ; o ; z ; o ; i ; c A Neoarchean P; a; l; a; e; o; p; r; o; t; e; r; o; z; o; i; c Mesoproterozoic Siderian Rhyacian Orosirian Statherian
	An approximate timescale of key Paleoproterozoic events.; Vertical axis scale: Millions of years ago
Proposed redefinition(s)	2420–1780 Ma; Gradstein et al., 2012;
Proposed subdivisions	Oxygenian 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;
Etymology
Name formality	Formal
Alternate spelling(s)	Palaeoproterozoic
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Era
Stratigraphic unit	Erathem
Time span formality	Formal
Lower boundary definition	Defined Chronometrically
Lower GSSA ratified	1991
Upper boundary definition	Defined Chronometrically
Upper GSSA ratified	1991

The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoic eon, 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.