Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains: Northern Great Lake states and central Mississippi Valley states, the Great Lakes, and southern Ontario (80°31ʹ to 93° west longitude)

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This map portrays the thickness and character of sediments in the glaciated part of the United States between 80°31' and 93° West longitude, including part of southern Ontario. It is one of a series of four maps presenting a regional synthesis and interpretation of available geologic data for the continentally glaciated United States east of the Rocky Mountains (see fig. 1 below). The numerous references (approximately 850) used to compile these maps, the majority of the acknowledgments, and a further explanation of the maps are contained in Soller (1992). Showing both the thickness and character of unconsolidated deposits, this map is in essence a three-dimensional view of the outermost layer of the Earth. Because the character of sediments is depicted on this map without implications regarding geologic time or events, the map complements regional maps that emphasize geologic events, such as the Glacial map of the United States east of the Rocky Mountains (Rint, 1959) and the geologic atlas of the United States (for example, Lineback and others, 1983). This map has three data components: the surface distribution of sediments, the total thickness of sediments, and the distribution of significant buried units. The sediments shown in this map series are glacial or glacially related deposits (including overlying Holocene sediments). Of limited extent and not shown are areas of colluvium not derived from glacial deposits; as used on these maps, the term Quaternary sediment does not include this type of colluvium. Subsurface information is not available for most of the mapped area, and, therefore, the depiction of buried units is uneven. Where buried units are shown, the complex geologic settings in which they occur are greatly simplified because of the small scale of this map series. Population growth and the resulting increase in demand for agricultural production, construction materials, land development, waste-disposal sites, and ground-water resources have created a growing need for three-dimensional geologic maps that can be directly applied to hydrologic, environmental, and landuse problems. Such maps depict the texture of surface and subsurface geologic materials, commonly to a specified depth or geologic contact. The glaciated region of the United States depicted in this map series has a particular need for three-dimensional geologic mapping. Approximately 40 percent of the U.S. population resides within the mapped area, which is less than one-quarter the size of the conterminous United States. The region also contains a major portion of the nation's agricultural and industrial capacity. This map series is a regional overview of the three-dimensional distribution of sediments for a large area and is intended to supplement the more detailed work on which it is based. I hope that this series of maps will generate interest in more detailed three-dimensional mapping of these, and other, deposits. Particularly in populated areas, detailed mapping is vital to the site-specific planning and assessment of the effects of human activities at and beneath the land surface. In contrast, regional maps such as the four maps of this series serve to place local, detailed mapping in context, to permit the extrapolation of data into unmapped areas, and to depict large-scale, regional geologic features and patterns that are beyond the scope of detailed local mapping. This series of maps is also a regional planning document that can assist in setting priorities for areas in need of more detailed mapping; subsequent detailed mapping should then be incorporated into an updated regional map. Geologic mapping is an iterative process, and the maps of this series should be considered as only an initial regional view of the glaciated sedimentary framework east of the Rocky Mountains.