The Stenian (from Greek stenos, "narrow") is the final geologic period in the Mesoproterozoic Era and lasted from 1200 Ma to 1000 Ma (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically. Name derives from narrow polymetamorphic belts formed over this period. The supercontinent Rodinia assembled during the Stenian.… (More on Stenian)