third and last period of the Mesoproterozoic era

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]


  1. "Organic geochemical study of mineralization in the Keweenawan Nonesuch Formation at White Pine, Michigan" (PDF). University of Michigan. Retrieved 25 May 2013.