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| Divisions of Lunar geologic time : |
| Pre-Nectarian - Nectarian - Lower Imbrian - Upper Imbrian - Eratosthenian - Copernican |
The Pre-Nectarian Period of the lunar geologic timescale runs from 4172 million years ago (the time of the initial formation of the Moon) to 3920 million years ago, when the Nectaris Basin was formed by a large impact. The lunar geologic timescale (or selenologic timescale) divides the history of Earth 's moon into five generally recognized geologic periods the Copernican The Nectarian Period of the Lunar geologic timescale runs from 3920 million years ago to 3850 million years ago In the Lunar geologic timescale, the Lower Imbrian epoch occurred between 3850 million years ago to about 3800 million years ago In the Lunar geologic timescale, the Upper Imbrian epoch occurred between 3800 million years ago to about 3200 million years ago The Eratosthenian period in the Lunar geologic timescale runs from 3200 million years ago to 1100 million years ago The Copernican Period in the Lunar geologic timescale runs from approximately 1100 million years ago to the present day The lunar geologic timescale (or selenologic timescale) divides the history of Earth 's moon into five generally recognized geologic periods the Copernican The Sea of Nectar ( Mare Nectaris) is a small Lunar mare or sea (a volcanic lava plain noticeably darker than the rest of the Moon 's surface located It is followed by the Nectarian period. The Nectarian Period of the Lunar geologic timescale runs from 3920 million years ago to 3850 million years ago Pre-Nectarian rocks are rare in the lunar sample suite; they are mostly composed of lunar highlands material which have been heavily churned, brecciated, and thermally affected by subsequent impacts, particularly during the Late Heavy Bombardment that marks the approximate beginning of the Nectarian Period. The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a period of time approximately 3800 to 4100 million years ago ( mya The Nectarian Period of the Lunar geologic timescale runs from 3920 million years ago to 3850 million years ago The primary Pre-Nectarian lunar highland material is dominated by the rock type anorthosite, which suggests that the early stage of lunar crustal formation occurred via mineral crystallization of a global magma ocean. Anorthosite (æˈnɔrθəsaɪt/ /ə- is a Phaneritic, Intrusive Igneous rock characterized by a predominance of Plagioclase Feldspar Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet This geologic period has been informally subdivided into the Cryptic and Basin Groups 1-9,[1] but these divisions are not used on any geologic maps. 
Relationship to Earth's geologic time scale
Since little or no geological evidence on Earth exists from the time spanned by the Pre-Nectarian period of the Moon, the Pre-Nectarian has been used as a guide by at least one notable scientific work[2] to subdivide the unofficial terrestrial Hadean eon. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The Hadean (ˈheɪdiən is the geologic eon before the Archean. In particular, it is sometimes found that the Hadean eon is subdivided into the Cryptic era, Basin Groups 1-9, Nectarian and Lower Imbrian, though the first two of these lunar divisions are informal and collectively make up the Pre-Nectarian. The Cryptic era is an informal term that refers to the earliest geologic evolution of the Earth and Moon. Basin Groups refers to 9 informal subdivisions of the lunar Pre-Nectarian geologic period. The Nectarian Period of the Lunar geologic timescale runs from 3920 million years ago to 3850 million years ago In the Lunar geologic timescale, the Lower Imbrian epoch occurred between 3850 million years ago to about 3800 million years ago
References
- ^ Don Wilhelms (1987). Geologic History of the Moon. U. S. Geological Survey Professional Paper 1348.
- ^ W. Harland, R. Armstrong, A. Cox, L. Craig, A. Smith, D. Smith (1990). A Geologic time scale 1989. Cambridge University Press.
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