Table 1 Lunar geological timescale currently used
Time-stratigraphic/geochronologic units | Geological Events | Age (b.y.) | |
|---|---|---|---|
Copernican (Cp) | Craters with preserved ray system were formed | 0.0~0.8 | |
Eratosthenian (Er) | Young craters with ray system subdued were formed; Small-scale basalts filled in basins and craters | 0.8~3.16 | |
Imbrian (Im) | Late Imbrian | Large-scale basalts filled in basins and craters | 3.16~3.80 |
Early Imbrian | Three basins including Imbrium, Orientale, and Schrodinger were formed | 3.80~3.85 | |
Nectarian (Nc) | Twelve basin-scale impacts happened, with the start from the Nectaris basin | 3.85~3.92 | |
Pre-Nectarian (PNc) | Thirty basin-forming impacts happened, with the start from the South-Pole Aitken (SPA) basin | 3.92~4.2(?) | |
Crystallization of the magma ocean, solidified to form the anorthosite crust | 4.2(?)~4.56 | ||