Base of Neoproterozoic Steniano Ectasian Period 狭带纪 stenij Precambrian Supereon Neoproterozoic Era steniano Steniën Mesoproterozoic Era Sten Sten Sten Sten younger bound -1000 Ma Geologic Time Scale (2019) ステニアン紀 Esteniense Base of Stenian Stenis Stenien a2.1.2.1 older bound -1200 Ma stenium stenium Proterozoic Eon Tonian Period steni Stenian Stenian Period Stenium Stenium Sténien Стен