Lower Imbrian

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Periods of Lunar geologic time :

Pre-Nectarian - Nectarian - Lower Imbrian - Upper Imbrian - Eratosthenian - Copernician

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 Imbriam was preceded by the Nectarian.

Since all geological evidence of that time on Earth has disappeared, it has been used as an unofficial period of the terrestrial Hadean eon. No doubt similar events have happened on Earth because it is considerably larger and more massive than the Moon.