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General Information Product 141

Divisions of Geologic Time (Bookmark)

By U.S. Geological Survey

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This bookmark presents information that is widely sought by educators and students. This bookmark is adapted from the more detailed U.S. Geological Survey Fact Sheet 2018–3054, “Divisions of Geologic Time,” prepared by the U.S. Geological Survey Geologic Names Committee in cooperation with the Association of American State Geologists. The fact sheet and the bookmark contain names of geologic time periods and boundary age estimates ratified by the International Commission on Stratigraphy in 2018.

First posted May 3, 2012

Revised March 27, 2020

For additional information, contact:

Youth & Education in Science (YES)
U.S. Geological Survey
National Center, Mail Stop 911
12201 Sunrise Valley Drive
Reston, VA 20192

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Suggested citation:

U.S. Geological Survey, 2016, Divisions of geologic time (ver. 2.0, March 2020): U.S. Geological Survey General Information Product 141, a bookmark,

ISSN 2332-3531 (print)

ISSN 2332–354X (online)

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Page Last Modified: Friday, March 27, 2020, 01:20:16 PM