INSET: USGS IMAP 748: Geologic maps of the Descartes region of the Moon Apollo 16 pre-mission maps

The evolution of the Moon’s surface shows three successive stages (Hartmann, 1970). The earliest, from the beginning of the decipherable record to the Imbrian Period, was dominated by frequent large-scale impacts which produced overlapping and interfering craters and giant multi-ringed basin with ejecta blankets. The second stage, extending through most of the Imbrian to early Eratosthenian Period