re: I don't recall...
The articles I read only mentioned in general terms how sulfur and sulfur dioxide related to local volcanism would've acidified the waters:
http://www.spacedaily.com/news/mars-mers-04zzzzx-printready.html
http://www.spacedaily.com/news/mars-mers-04zzzzx-printready.html
The analogy has also been made to the Rio Tinto region of Spain:
http://mars.astrobio.net/cgi-bin/mpdf.cgi?sid=271&ext=.pdf
http://mars.astrobio.net/cgi-bin/mpdf.cgi?sid=271&ext=.pdf
http://www.nasa.gov/centers/ames/news/releases/2003/03images/tinto/tinto.html
http://www.nasa.gov/centers/ames/news/releases/2003/03images/tinto/tinto.html
