A descriptive article can be downloaded here.
Havoc Hole is a small but very interesting site with a long geological history (see the article which can be downloaded from the link above ). It lies a little to the north of Dumbarton Rock and a visit to it can easily be combined with visits to the Rock and also to Ardmore Point which is just north of Cardross. Descriptive leaflets for these sites can also be downloaded from their respective pages.
In addition to the material linked above, Strathclyde Geoconservation Group members have created a short information sheet about this site to help introduce accessible local geology to a wider audience.