The United States is an extremely large area with a variety of geological landforms and units from various geologic ages; the country contains some of the earliest rocks found on Earth. The most comprehensive summary of its geology is the “Geology of North America” series, published from 1986 to 1998 by the Geological Society of America (GSA) to celebrate its centennial.[1] It consists of forty separately titled volumes plus a series of maps and cross-sections showing the subsurface geology across the United States, Mexico, Canada, and Greenland. It also includes six field guides describing the geology of significant sites in North America. The society continues to publish field guides about the geology of areas throughout the United States in conjunction with its annual and regional meetings.
About the same time that the Geological Society of America started publishing its series, the American Geophysical Union, another geoscience organization in the United States, published a series of 136 books, 28th International Geological Congress Field Trip Guidebooks, for the meeting held in Washington, DC. These guidebooks summarize the geology of significant geological sites in North America, serving as useful starting points for interested audiences.
People looking for information on the geology of the United States in a single volume have several options. William Frazier and David Schwimmer’s Regional Stratigraphy of North America describes the rock layers, layering, age, and environment of the deposition of rocks throughout North America. It summarizes knowledge of North American stratigraphy at the time it was published and includes twenty-nine pages of references. Two early works, Nevin Fenneman’s Physiography of Eastern United States and Physiography of Western United States, describe major surface features of the United States and their relationship to geology. Although plate tectonics has changed the interpretation of how these features formed, Fenneman’s block diagrams and descriptions and the references he cites are still useful starting points for students and researchers seeking information on early work about an area. Joseph DiPietro’s Landscape Evolution in the United States: An Introduction to the Geography, Geology, and Natural History provides a more current interpretation of the subject.
Some areas of the United States have glacial and periglacial deposits covering the underlying bedrock (deposits beneath the surface materials)—somewhat like frosting on a layer cake—although the underlying rock layers may not be flat. The Quaternary of the United States, edited by H. Wright and David Frey, summarizes what was known about U.S. Quaternary deposits at the time of its publication. The Quaternary Period in the United States by Alan Gillespie, Stephen Porter, and Brian Atwater contains summary articles on glacial and periglacial deposits and the Quaternary climate record and vegetation history of the country. Quaternary Glaciations: Extent and Chronology, Part II: North America, edited by Jurgen Ehlers and Philip Gibbard, updates Wright and Frey’s work with current information on Quaternary deposits in many areas of the United States.
[1] A full list of the titles in the “Geology of North America” series is available at the University of Texas Walter Geology Library website, Research Guides section, http://lib.utexas.edu/geo/fieldguides/dnagguide.html.
People seeking information on state and local geology should start with their state geological survey; these are linked from the Association of American State Geologists website. State survey websites contain information on publications describing the geology of localities or entire states, including some digitized and digital publications. They may also provide information on other publications about their state’s geology.
The USGS National Geologic Lexicon Database: GEOLEX, developed by the U.S. National Cooperative Geologic Mapping Program, Association of American State Geologists, and U.S. Geological Survey, can be used to find information on all named geologic units in the United States, including their age and extent, and citations to publications containing the original descriptions and subsequent changes to each unit.
Two sites are useful for finding field trip guidebooks. The Virtual Field Trip Guides: United States and Canada, developed by the Walter Geology Library at the University of Texas at Austin, contains links to digital and digitized field trip guidebooks; the Geologic Guidebooks of North America database, compiled by the Geoscience Information Society, is an index to field trip guidebooks.
