I didn’t know this existed until today, so I’ll give it a little promotion. I was in the midst of building my own in Illustrator by tracing the official 2009 timescale from stratigraphy.org (the PDF has font issues on my computer, apparently).
We’ll see how it works for my 2011 UND Scholarly Forum poster. Wish me luck.
EDIT: Had some problems saving the image as a PDF in Mac OS 10.6.6 (Snow Leopard), but saving as SVG works fine. If a save seems to fail, you need to restart the program and try again. Using version 4.2.5.