Geologic map of the Ptolemaeus Quadrangle of the moon

The application of stratigraphic and structural principles to geologic mapping of the Moon from telescopic photographs has been discussed by Shoemaker (1962) and Shoemaker and Hackman (1962). Major geologic units are recognized by regional topographic and albedo differences. Pictures returned by Ranger, Surveyor, and Lunar Orbiter spacecraft show that a fragmental regolith, presumably produced by repeated impact and mass wasting, has formed on all but the very youngest of these units. In the Ptolemaeus quadrangle, ages assigned to the rock units are tentative and correlations with the major lunar time-stratigraphic units whose type localites are in vicinity of Mare Imbrium are uncertain. Materials of each crater are together considered an informally named formation. Craters smaller than 3 km are not shown on the map, except for those that are satellitic, brightly rayed, or part of a chain. Approximate numerical albedo values (Pohn and Widley, 1966) corresponding to the qualitative terms used here are as follows: low, 1.10 to 0.12; intermediate, 0.12 to 0.14; high, 0.14 to 0.16; very high, greater than 0.16. Eclipse thermal data are from Saare, Shorthill, and Fulmer (1966). Detailed studies of the Alphonsus area, based on Ranger IX, appeared in a report by HeacocK and others (1966). A geologic map od the crater Alphonsus and environs was prepared by Carr (1966).