The Stenian is the last geological period in the Mesoproterozoic . It began 1.2 billion years ago, and ended at 1 billion years ago. Before it was the Ectasian . It is followed by the Tonian .

The supercontinent Rodinia began forming in this period. Fossils of the first known sexually-reproducing eukaryotes are found at the end of the previous period in the Hunting Formation on Somerset Island , Nunavut , Canada .

This period includes the Keweenawan Age at about 1100 mya. ^[1]

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