Map of Surficial Deposits and Materials in the Eastern and Central United States (East of 102° West Longitude)

This map depicts the aerial distribution of surficial geologic deposits and other materials that accumulated or formed during the last two or more million years. That period includes all activities of the human species. These materials are at the surface of the Earth and make up the ground on which we walk, the dirt in which we dig foundations, and the soil in which we grow crops. The map is based on 31 published maps in the U.S. Geological Survey’s Quaternary Geologic Atlas of the United States (U.S. Geological Survey Miscellaneous Investigations Series I–1420). It was compiled at 1:1,000,000 scale, to be viewed as a digital map at a nominal scale of 1:2,000,000, and to be printed as a conventional paper map at 1:2,500,000 scale.

Each 1:1,000,000 4° x 6° quadrangle map in the atlas was simplified. Because the quadrangles of the atlas were compiled and printed in different projections and on different bases, the projections and bases were converted to a common one for publication. First, the source geology had to be recompiled to match the digital base on which the map was to be printed. The GIS file of streams and water bodies from the National Atlas of the United States was clipped into 4° x 6° quadrangles to match the original maps and converted to the projections of the original maps. The geology was then compiled on these drainage bases.

The new, hand-drafted compilations of the geology were scanned, vectorized with the LT4X computer program, and converted into ArcInfo coverages. Polygons and lines were attributed, and map data for the individual quadrangles was unprojected to geographic coordinates, appended to one another, and edgematched. Selected shorelines, lakes, and rivers were added from the hydrographic coverage. The geology was reconciled along the borders of the adjacent quadrangles, and the entire map was converted to the Lambert azimuthal equal area projection.

The map layout was produced by importing ArcInfo shapefiles for the geologic database and planimetric base into Adobe Illustrator through the plug-in Avenza MAPublisher. The map sheet is accompanied by a 46-page pamphlet of detailed map unit descriptions. The database is available as ArcInfo export files and ArcView shapefiles here.