Information on geologic units in the United States including their names, age, extent, and publications that describe each unit.
The Geologic Names Lexicon (GEOLEX) is a catalog of the named geologic units in the United States. It contains information on unit names that were published in the various editions of the U.S. Geological Survey's Lexicon of Geologic Names. The database contains information on over 16,000 geologic units state geological surveys and the USGS. GEOLEX provides information on the original and current description of the unit, the type locality, geologic age, geographic extent, variations in geologic name usage, and publications that have described the unit.