Bedrock geologic map of the Greenwood quadrangle, Marquette County, Michigan

The Marquette Iron Range is presently ( 1973) the second largest iron mining district in the United States. Commercial iron deposits, now mostly concentrating-grade ore, are in the Negaunee Iron-formation, which is part of a thick sequence of metasedimentary rocks of Precambrian X age. These rocks are preserved in the west-trending Marquette synclinorium, and are flanked to the north and south by older Precambrian W crystalline rocks (fig. 1). The Greenwood quadrangle includes part of· the central Marquette Range and part of the Precambrian W rocks south of the range. No mines are active in the quadrangle, but appreciable quantities of iron-formation may be future concentrating-grade iron ore reserves.