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The Rhyacian (pronounced /raɪˈeɪsiən/, Greek: Ρυαξ (rhyax), meaning "stream of lava") is the second geologic period in the Paleoproterozoic Era and lasted from 2300 Ma to 2050 Ma (million years ago).[1] Instead of being based on stratigraphy, these dates are defined chronometrically.[2]

The Bushveld Complex and other similar intrusions formed during this period.[2]

The Huronian glaciation period ended in late Rhyacian 2100 Ma.[1][2]

The first known eukaryotes began to evolve in the Rhyacian period. The multicellular Francevillian Group Fossils, at 2.1-Gyr-old are from the Rhyacian period.[3]


1. ^ a b "Rhyacian Period". GeoWhen Database. http://www.stratigraphy.org/geowhen/stages/Rhyacian.html. Retrieved January 5, 2006.
2. ^ a b c James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale" ([dead link] – Scholar search). Lethaia 37: 183–199. doi:10.1080/00241160410006492. http://www.stratigraphy.org/precambrian/Ogg_2003.pdf.
3. ^ El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E.; Bekker, Andrey; Macchiarelli, Reberto (July 2010). "Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago". Nature 466 (7302): 100-104. doi:10.1038/nature09166. PMID 11931142.

Geologic time scale

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