Geologic map of the Colombo Quadrangle of the Moon

Relative ages of structures and geologic units have been determined from intersection and apparent overlap relations and from morphologic freshness reflecting degree of preservation. The fivefold crater-age sequence is based on the classification of Shoemaker and Hackman (1962), and corresponds broadly to a modified classification of Pohn and Offield (1970) and Offield (1971). Rock units in the quadrangle are provisionally correlated with time-stratigraphic units first described in and near the Imbrium basin (Shoemaker, 1962 a, b; Shoemaker and Hackman, 1962, Shoemaker and others, 1963) and subsequently recognized elsewhere on the near side of the Moon (McCauley, 1967; Wilhelms, 1970; Wilhelms and McCauley, 1971).