Paleoproterozoic | ||||||
---|---|---|---|---|---|---|
![]() Paleoproterozoic stromatolites | ||||||
Chronology | ||||||
| ||||||
Proposed redefinition(s) | 2420–1780 Ma Gradstein et al., 2012 | |||||
Proposed subdivisions | Oxygenian Period, 2420–2250 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[1] | |||||
Upper boundary definition | Defined Chronometrically | |||||
Upper GSSA ratified | 1991[1] |
The Paleoproterozoic Era[4] (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.[5] It was during this era that the continents first stabilized.[clarification needed]