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 Periods, was characterized by volcanism, producing basalt flows of the maria an varied materials on the terrae. The final and longest stage, extending through the greater part of the Eratosthenian Period and the whole of the Copernican, was one of reduced geologic activity. Major modifications of the geologic structure by large impacts of volcanism occurring only locally, although changes by small-scale impact and mass wasting affected the entire surface. The Descartes region, in the central highlands of the Moon about 500 km southeast of the center of the lunar disk, is dominated by features of the middle stage and contains an exceptionally favorable site for their study.