Thursday, July 22, 2010

USGS releases new geologic time scale

The USGS has released an upated "Divisions of Geologic Time" produced by
the USGS Geologic Names Committee and the Association of American State Geologists (AASG), which represents an update containing the unit names and boundary age estimates ratified by the International Commission on Stratigraphy (ICS).

The fact sheet states that scientists should note that other published time scales may be used, provided that these are specified and referenced (for example, Palmer, 1983; Harland and others, 1990; Haq and Eysinga, 1998; Gradstein and others, 2004; Ogg and others, 2008).

USGS FS 2010-3059: Divisions of Geologic Time - Major Chronostratigraphic and Geochronologic Units

This fact sheet is a modification of USGS Fact Sheet 2007–3015 by the U.S. Geological Survey Geologic Names Committee.


  1. Anonymous3:56 PM

    Randy forwarded this comment:

    It's a shame this is already out of date. I'm not sure why they didn't incorporate the revisions of Walker & Geismann (2009). For example, we've known that the base of the Late Triassic is older than 228 Ma for four years - see Furin et al. (2006).

    Furin, S., Preto, N., Rigo, M., Roghi, G., Gianolla, P., Crowley, J.L., and Bowring, S.A., 2006, High-precision U-Pb zircon age from the Triassic of Italy: implications for the Triassic time scale and the Carnian origin of calcareous nannoplankton and dinosaurs: Geology, v. 34, p. 1009-1012.

    Walker, J.D., and Geissman, J.W., 2009, GSA geologic time scale: GSA Today, v. 19, p. 60-61.

  2. Anonymous11:55 AM

    I need a timeline on The Triassic time period.