Geologic map of the near side of the Moon

Abstract

RATIONALE, METHODS, AND FORMATthe Moon and produced a workable nearside stratigraphy (Shoemaker and Hackman, 1962; McCauley, 1967b; Wilhelms, 1970b).Prior to the Lunar Orbiters, telescopic resolution limitations dictated emphasis on the grosser aspects of lunar geology: the structures and ejecta blankets associated with the multiringed basins, the major craters, and the stratigraphic relations between the generally younger maria and older terrae.The main products of the telescopic work were 36 1:1 ,000,000-scale geologic quadrangle maps (those marked "T" in table 1) and a 1 :5,000,000-scale preliminary map of the region 32°N.to 32°S.and 70°E.to 70°W.(Wilhelms, Trask, and Keith, 1965).Before the systematic program began, Hackman and Mason (1961) produced a set of three nearside maps at a scale of 1:3,800,000 from telescopic data; these maps emphasized the geology, physiography and ray-crater distribution.The chief purpose of the 1 :5,000,000-scale map is to summarize the current state of lunar geologic knowledge as developed from the U.S. Geological Survey's systematic lunar mapping program, which began in 1960.Like terrestrial synoptic maps it provides a stratigraphic framework to be used for developing new theory and for determining the regional significance of surface exploration results.The geologic summary which accompanies the map gives the major genetic and historical conclusions which stem from the work.The map explanation provides the descriptive details that led to these conclusions.This pamphlet discusses the rationale methods, and nomenclature of lunar stratigraphy: specifically for those interested in why and how the map was produced.The work is based both on results of the telescopic mapping program and on data from the unmanned lunar exploration program, particularly the regional coverage of Lunar Orbiter IV 1 The early telescopic studies established the geologic heterogeneity of 1 U.s e f u I .c .oII e c t ions of photographs from a II Orbtter ~tsstons, accompanied by geologically oriented explanatiOns, appear in Lowman ( 1969) and Kosofsky and El-Baz (1970).