Geologic map of the Rheita Quadrangle of the Moon

Photographs returned by unmanned Lunar Orbiters have contributed greatly to the current lunar geologic mapping program. This is particularly true for quadrangles near the limbs, such as Rheita in the southeast earthside quadrant. The new data and revised interpretations amend the geologic framework established by earlier workers (Shoemaker (1962) and Shoemaker and Hackman (1962) applied basic stratigraphic principles to set up a lunar time scale; McCauly (1967) summarized changes made in he next five years of study; Wilhelms (1970) compiled all the telescopic refinements and additions to the original framework). Detailed studies of crater morphologies from Lunar Orbiter photographs (Pohn and Offield, 1970) permit the placement of most craters within the time-stratigraphic systems (Offield and Pohn, 1970: Offield, 1971). Other advances in understanding lunar processes included establishing the sequence of formation and features of large, multiringed basins (McCauly, 1968; Stuart-Alexander and Howard, 1970) and criteria for distinguishing between impacts and possible volcanic craters (McCauly,1968).