Geologic Time and Symbol Standards

It may interest you that there is a newly minted geologic time scale and implied color scheme recently released by the USGS and the AASG:

http://pubs.usgs.gov/fs/2007/3015/

Also note that there is a comprehensive document outlining a digital cartographic standard for geologic map symbolization:

http://ngmdb.usgs.gov/fgdc_gds/

At NBMG and other agencies, the implied color scheme in the timescale is largely unworkable in detailed maps of Tertiary and Quaternary deposits.

As for the symbology, this is an obvious standard for all geologic mappers and agencies to adopt.