The Siderian Period ( /saɪˈdɪəri.ən, sɪ-/; Ancient Greek: σίδηρος, romanized: sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from 2500 Ma to 2300 Ma. Instead of being based on stratigraphy, these dates are defined chronometrically.
| Siderian | ||
|---|---|---|
 A reconstruction of the Earth's continents during the middle Siderian, circa 2.4 Ga.[citation needed] | ||
 A Siderian banded iron formation in Dales Gorge, Western Australia | ||
 Artist's impression of the Earth during the Huronian glaciation, starting from mid-Siderian | ||
| Chronology | ||
Events of the Siderian Period. Axis scale: millions of years ago. | ||
Gradstein et al.
Gradstein et al.
The deposition of banded iron formations peaked early in this period. These iron rich formations were formed as anaerobic cyanobacteria produced waste oxygen that combined with iron, forming magnetite (Fe3O4, an iron oxide). This process removed iron from the Earth's oceans, presumably turning greenish seas clear. Eventually, with no remaining iron in the oceans to serve as an oxygen sink, the process allowed the buildup of an oxygen-rich atmosphere. This second, follow-on event is known as the oxygen catastrophe, which, some geologists believe triggered the Huronian glaciation.[2][3]
Since the time period from 2420 Ma to 2250 Ma is well-defined by the lower edge of iron-deposition layers, an alternative period named the Oxygenian, based on stratigraphy instead of chronometry, was suggested in 2012 in a geological timescale review.[4]
References
- "Siderian Period". GeoWhen Database. Retrieved May 24, 2015.
- "The Siderian". Dinosaurfact.net. Retrieved May 24, 2015.