THE U.S. GEOLOGIC NAMES LEXICON (GEOLEX) –FROM HANDWRITTEN INDEX CARDS TO THE INTERNET; ONE HUNDRED YEARS OF PROGRESS AND CONSISTENCY

In the late 1800's, the U.S. Geological Survey, under the leadership of Director John Wesley Powell, began a systematic mapping program that produced the Geologic Atlas of the United States folios. Recognizing the need for a consistent set of geologic maps, he formed committees to develop standards for cartography, principles of rock and sediment classification and nomenclature, and a geological time scale. Essential to these standards and to the Atlas series was a catalog of geologic names of the U.S.

The catalog of geologic names remains essential to this day, both to the science and to preparation of the U.S. National Geologic Map Database (NGMDB, http://ngmdb.usgs.gov), which is a collaborative project managed by the USGS and the Association of American State Geologists as mandated by Congress.

GEOLEX contains ~16,000 geologic units, and provides original and revised definitions, type localities, geologic ages, geographic extent, variations in geologic name usage, and publication synopses. Information has been compiled mostly from formal reports and maps published since the mid-1800's, emphasizing outcrop-level descriptions, age determinations, and relationships to other geologic units. These reports are quite varied in nature, and the publishers range from local societies to state and national agencies. For each report, the stratigraphic interpretations are considered valid if the guidelines of the North American Stratigraphic Code are followed. This raises a challenge, to balance the varied stratigraphic interpretations in these reports with the need to provide a standard definition for each geologic unit.

For a century, the U.S. Geologic Names Committee (GNC) has assisted geologists in their efforts to define and clarify the nation's stratigraphy. GNC activities have been recorded in a few publications, but there remains a large collection of unpublished notes which are used on a regular basis to maintain GEOLEX. We are scanning these notes, to facilitate their use in GEOLEX and to make them publicly accessible.

To increase the utility of scientific reports, maps, and GNC notes cited in GEOLEX, we are associating them with spatial data in the NGMDB (e.g., the footprint of a map publication, or the digital map data), to provide our users with the descriptions in their geographic context.