I have a couple of diagrams that given the basics of the bedrock geology of the central Twin Cities. One covers all of the formations exposed as bedrock within MNRRA, and the other focuses on the St. Paul–Minneapolis bluffs (note that thicknesses and rock types differ elsewhere). They are based on a combination of information in Mossler and Tipping (2000), Mossler (2008, 2013), personal observations, and recommendations from the Minnesota Geological Survey. The patterns and symbols come from the USGS's standards (http://pubs.usgs.gov/tm/2006/11A02/), except for the little fossil cartoons, which came from photos run through a comic filter. They're admittedly schematic (my disconformities are nothing to write home about, and I just used arbitrary widths for susceptibility to erosion, with more resistant rock types sticking out farther), and I'm open to suggestions. I prepared them for MNRRA, so if you want to use them elsewhere, you should credit the park.
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| The bedrock units visible along the Mississippi from Minneapolis to Hastings. The disconformities (wavy lines) don't literally look like that. They represent episodes of erosion between the deposition of formations, and can be anything from a gentle beveling to deep paleochannels. |
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| St. Paul–Minneapolis bedrock units, focused on the upper St. Peter–lower Decorah section found at the top of the bluffs. |
Mossler, J. H. 2008. Paleozoic stratigraphic nomenclature for Minnesota. Minnesota Geological Survey, St. Paul, MN. Report of Investigations 65.
Mossler, J. H. 2013. Bedrock geology of the Twin Cities ten-county metropolitan area, Minnesota. Minnesota Geological Survey, St. Paul, MN. Miscellaneous Map Series 194. Scale 1:125,000.
Mossler, J. H., and R. G. Tipping. 2000. Bedrock geology and structure of the seven-county Twin Cities metropolitan area, Minnesota. Minnesota Geological Survey, St. Paul, MN. Miscellaneous Map Series 104. Scale 1:125,000.
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