- Siderian
The Siderian (IPAEng|saɪˈdɪəriən, _el. sideros, meaning "iron") is the first
geologic period in thePaleoproterozoic Era and lasted from 2500 Ma to 2300 Ma (million years ago). Instead of being based onstratigraphy , these dates are defined chronometrically.Abundance of
banded iron formation s (BIFs) peaked early this period. BIFs were formed as anaerobicalgae produced wasteoxygen that combined withiron , formingmagnetite (Fe3O4, aniron oxide ). This process cleared iron from the oceans, presumably turning greenish seas clear. Eventually, without an oxygen sink in the oceans, the process created the oxygen-rich atmosphere of today. This event is known as theOxygen Catastrophe .The
Huronian glaciation began in the Siderian 2400 Ma and ended in the lateRhyacian 2100 Ma.References
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