Stenian
| Stenian | |||||||||||||
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Paleoglobe of Earth during the late Stenian, c. 1040 Ma | |||||||||||||
| Chronology | |||||||||||||
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| Etymology | |||||||||||||
| Name formality | Formal | ||||||||||||
| Usage information | |||||||||||||
| Celestial body | Earth | ||||||||||||
| Regional usage | Global (ICS) | ||||||||||||
| Time scale(s) used | ICS Time Scale | ||||||||||||
| Definition | |||||||||||||
| Chronological unit | Period | ||||||||||||
| Stratigraphic unit | System | ||||||||||||
| Time span formality | Formal | ||||||||||||
| Lower boundary definition | Defined chronometrically | ||||||||||||
| Lower GSSA ratified | 1990 | ||||||||||||
| Upper boundary definition | Defined chronometrically | ||||||||||||
| Upper GSSA ratified | 1990 | ||||||||||||
The Stenian Period (/ˈstiːni.ən/ STEE-nee-ən, from Ancient Greek: στενός, romanized: stenós, meaning "narrow") is the final geologic period in the Mesoproterozoic Era and lasted from 1200 Mya to 1000 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically. The name derives from narrow polymetamorphic belts formed over this period. It is preceded by the Ectasian Period and followed by the Neoproterozoic era and the Tonian period.
The supercontinent Rodinia assembled during the Stenian. It would last into the Tonian period before breaking up in the Cryogenian.
This period includes the formation of the Keweenawan Rift at about 1100 Mya.
Fossils of the oldest known sexually reproducing organism, Bangiomorpha pubescens, first appeared in the Stenian.