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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 1,243 records · Page 69Linked to original sources
USGS1994

Quaternary geologic map of the Dallas 4° x 6° quadrangle, United States

The Quaternary Geologic Map of the Dallas 4° x 6° Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the Earth. They make up the ground on which we walk, the dirt in which we dig foundations, and the soil in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

Texas↗
USGS1974

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.

Michigan↗