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 ...

NH copy Purchased from the Cullman Endowment. V. 1. The chronostratigraphic scale / F.M. Gradstein and J.G. Ogg -- Biochronology / F.M. Gradstein -- Cyclostratigraphy and astrochronology / L.A. Hinnov ...

A new analysis of rocks thought to be at least 2.5 billion years old helps clarify the chemical history of Earth's mantle -- the geologic layer beneath the planet's crust. The findings hone scientists ...