Still Yet Another Geologic Time Scale

The Geological Society of America has a hand in the time-scale game: 25 years ago the GSA started publishing a huge landmark series of books on the geology of North America, and a committee settled on a standard time scale to use across the series. Millions of field photos feature the handy GSA scale card, with a bar showing centimeters and inches on one side and the time scale on the other.

In the April GSA Today that just came out today, the 2009 GSA Time Scale is unveiled. In a nutshell, GSA updates the Triassic slightly from the ICS scale; it also keeps the Tertiary and extends the Quaternary back to include the Gelasian Age, betting in advance that the votes will go that way (I think it's a safe bet). An accompanying article lays out the administrivia behind this new scale.

The GSA photo scale card — Geology Guide photo