Nectarian. The Nectarian Period of the lunar geologic timescale runs from 3920 million years ago to 3850 million years ago.
It is the period during which the Nectaris Basin and other major basins were formed by large impact events. Ejecta from Nectaris forms the upper part of the densely cratered terrain found in lunar highlands. Millions of years before present Relationship to Earth's geologic time scale References Basin Groups. Basin Groups refers to 9 subdivisions of the lunar Pre-Nectarian geologic period.
It is the second era of the Hadean Definition The motivation for creating the Basin Groups subdivisions was to place 30 pre-Nectarian impact basins into 9 relative age groups. The relative age of the first basin in each group is based on crater densities and superposition relationships, whereas the other basins are included based on weaker grounds. Basin Group 1 has no official age for its base, and the boundary between Basin Group 9 and the Nectarian period is defined by the formation of the Nectaris impact basin. Timeline of the Precambrian.