Source: Wikipedia, the free encyclopedia.
2050 – 1800 Ma
Stratigraphic unitSystem
Time span formalityFormal
Lower boundary definitionDefined chronometrically
Lower GSSA ratified1991[1]
Upper boundary definitionDefined chronometrically
Upper GSSA ratified1991[1]

The Orosirian Period (

Mya to 1800 Mya (million years ago).[2] Instead of being based on stratigraphy, these dates are defined chronometrically

Vredefort impact structure is believed to have formed in this period

The later half of the period was an episode of intensive orogeny on virtually all continents.

Two of the largest known impact events on Earth occurred during the Orosirian. Early in the period, 2023 Mya, a large asteroid collision created the Vredefort impact structure. The event that created the Sudbury Basin structure occurred near the end of the period, 1850 Mya.

For the time period from about 2060 to 1780 Mya, an alternative period based on stratigraphy rather than chronometry, named the Columbian, was suggested in the geological timescale review 2012 edited by Gradstein et al.,



The supercontinent Columbia formed at the end of this period.


  • "Orosirian Period". GeoWhen Database. Retrieved July 8, 2011.
  • James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia. 37 (2): 183–199. .