Template talk:Paleozoic Stratigraphy of the Upper Midwest

Ages of Rock Units

There are two sources listed for this template but neither list the date ranges given for the ages of the rock units listed. Which sources were used? I know the lower age of the Decorah Shale is given as 454 ma which must be based on the Deicke K bentonite but there should be references for all dates. Kirkmona (talk) 14:50, 10 March 2009 (UTC)