Stenian

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.