Lower Imbrian

In the Lunar geologic timescale, the Lower Imbrian epoch occurred between 3850 million years ago to about 3800 million years ago. It overlaps the end of the Late Heavy Bombardment of the inner solar system. The impact which created the huge Mare Imbrium basin occurred at the start of the epoch. The other large basins that dominate the lunar nearside (such as Crisium, Tranquilitatis, Serenitatis, Fecunditatis, and Procellarum) were also formed in this period. These basins filled with basalt mostly during the subsequent Upper Imbrian epoch. The Lower Imbrian was preceded by the Nectarian.

Relationship to Earth's geologic time scale

Since little or no geological evidence on Earth exists from the time spanned by the Lower Imbrian period of the Moon, the Early (or Lower) Imbrian has been used by at least one notable scientific work [cite book | title = A Geologic time scale 1989 | publisher = Cambridge University Press | year = 1990 | last = W. Harland, R. Armstrong, A. Cox, L. Craig, A. Smith, D. Smith] as an unofficial subdivision of the terrestrial Hadean eon.

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