Is there any sort of database that provides the locations of exposures of certain geologic groups or formations?

I ask because I have read that halite occurs in the Michigan Basin, and specifically occurs in beds of the Salina Formation (Silurian) and the Detroit River Group (Devonian). I would love to find a source (preferably a map) that provides locations where these features (or really, halite) are at or near the surface.


  • 1
    $\begingroup$ USGS geological maps: mrdata.usgs.gov/geology $\endgroup$
    – stevej
    Nov 6, 2014 at 2:07
  • $\begingroup$ @stevej Do you know of a feature where I can search for particular features? I think maybe I can load the shapefile in ArcMap and look in the attribute table for what I want, but I'm curious if there is an easier way. $\endgroup$ Nov 7, 2014 at 0:57
  • $\begingroup$ Hi Alex, I'd say downloading the data and loading into ArcMap/QGIS/whatever would be the easiest way to go. Online GIS mapping tools are generally not very powerful, unfortunately. $\endgroup$
    – stevej
    Nov 7, 2014 at 2:22
  • $\begingroup$ Also this book might contain useful maps: rock.geosociety.org/Store/detail.aspx?id=FLD031 $\endgroup$
    – stevej
    Nov 7, 2014 at 2:24

2 Answers 2


You may also find localised geological guides, such as the Roadside Geology series.

http://geology.com/store/roadside-geology.shtml has a listing. While I have not used them, I have seen them crop up fairly often as a nice option when looking for interesting geology in more general terms, including for some outcrops.

(I would have made this a comment, rather than an answer, but have no rep yet.)


Macrostrat is (or in fact will be) what you are looking for I think.
This database is still in development and is apparently only available through the website as a beta so far. It only seems to cover the US, Australia and New Zealand to this date but you can search for specific formations.

From your example, here is a screenshot of the result I had while looking for surface outcrops of halite:

US halite

or when looking for the Salina Group (the blue dots are cross-reference from the Paleobiology Database, if I understood correctly):

enter image description here

As they say on the front page, so far, the functionalities are very limited.


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