Lunar geologic timescale

The lunar geologic timescale divides the history of Earth's Moon into six generally recognized geologic periods:

Copernician Period : -1100 MY to present
Eratosthenian Period : -3200 MY to -1100 MY
Upper Imbrian Epoch : -3800 MY to -3200 MY
Lower Imbrian Epoch : -3850 MY to -3800 MY
Nectarian Epoch : -3920 MY to -3850 MY
Pre-Nectarian Epoch: -4550 MY to -3920 MY

The values for these dates remain in some dispute, as the divisions are based on the dates when various significant lunar geological events occurred and it is difficult to pinpoint them exactly.

In many lunar highland regions, planetologists cannot currently distinguish between Nectarian and Pre-Nectarian materials. These deposits are called Pre-Imbrian age materials, which encompasses both time periods.

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text:Copernician from:-1100 till:0
text:Eratosthenian from:-3200 till:-1100
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text:Lower~Imbrian from:-3850 till:-3800 shift:(0,25)
text:Nectarian from:-3920 till:-3850 shift:(0,5)
from:start till:-3920 text:Pre-Nectarian

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