USGS and AASG Unveil A Geologic Time Scale and Color Scheme for Use in Creating Geologic Maps

Reston, VA - The U.S. Geological Survey (USGS) and the Association of American State Geologists (AASG) announced that they have developed an updated geologic time scale and color scheme for use in creating geologic maps of the United States.

Geologic maps show the rock types at the Earth’s surface and help unravel the history of the Earth. They can help inform land-use decisions such as how planners should design buildings, canals, roads, and drainage of farmland. They can help locate earthquake faults and show where landslides are likely to occur to help plan for safer communities. They can help predict where resources such as oil, gas, and coal exist for resource development.

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“There is now a national standard for producing geologic maps and communicating the ages of geologic formations in the United States,” said USGS scientist Randy Orndorff. “Geologic maps are important tools for policy makers, planners and the general public, and having a streamlined way to create geologic maps helps make them a credible and viable resource for land-use and environmental planning as well as economic development.”

Geologists from the USGS, state geological surveys, academia and other organizations have sought a consistent time scale to be used in communicating the ages of geologic units in the United States. Many international debates have occurred over names and boundaries of units, and various time scales have been used by the geoscience community. To help remedy differences, the USGS and the AASG developed “Divisions of Geologic Time-Major Chronostratigraphic and Geochronologic Units.”

“AASG considered the development of a national standard time scale to be of critical importance to geologists around the country engaged in the production of geologic maps,” said Alabama State Geologist Nick Tew, who represented the AASG in development of the updated geologic time scale. “The AASG was happy to work with our colleagues at USGS in development of the updated time scale.”

USGS provides science for a changing world. For more information, visit the USGS Web site. You can also listen to or download a USGS podcast featuring Mr. Orndorff discussing how you can discover what’s beneath your feet by using geologic maps at the USGS CoreCast Web site.