Nectarian

The Nectarian is a lunar geologic period and corresponding rock-stratigraphic system dating roughly from 3.92 to 3.85 billion years ago. It is marked by the formation of major lunar impact basins.

Lunar geologic timescale: The framework that divides lunar history into intervals based on rock relationships and major geological events. The Nectarian is one interval in this broader chronology.
Nectaris basin: A large lunar impact basin whose formation anchors the name and stratigraphic context of the Nectarian. Its formation is the defining event behind the period’s name.
Serenitatis basin: A large impact basin on the Moon’s near side, partly covered by younger volcanic plains. Its structure and deposits provide a prominent example of basin-forming activity near this interval.
Pre-Nectarian: The earliest lunar geologic period, preceding the Nectarian and extending back to the Moon’s formation. It covers older crust and impact structures beneath Nectarian units.
Lunar basin: A large depression on the Moon, usually formed by a major impact and often ringed by concentric structures. Basin formation supplies the impact-based marker used to define Nectarian boundaries.
Imbrium basin: A vast lunar impact basin formed near the end of the Nectarian, around the beginning of the Imbrian period. Its ejecta blanket the older Nectarian surface and mark a major chronological transition.
Crisium basin: A circular lunar impact basin on the northeastern near side, filled largely by younger mare basalt. Its basin and ejecta belong to the population used to characterize Nectarian terrain.
Imbrian: A lunar geologic period following the Nectarian, associated with major basin formation and extensive mare volcanism. The Imbrian begins after the Nectarian and includes deposits that cover its terrain.
Lunar stratigraphy: The study and classification of the Moon’s rock layers and geological units. Nectarian units are identified through their relative positions and basin relationships.
Nectarian system: The lunar rock-stratigraphic system corresponding to the Nectarian period. It names the rocks and surface units assigned to this interval.

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