ALUMNI NEWSLETTER - Earth Sciences - University of Minnesota

New State Bedrock Geologic MapThe Minnesota Geological Survey (MGS) has released a newState Bedrock Geologic Map. It is only the 8th such state-widedepiction of bedrock geology to be published in the 141 yearssince inception of the MGS in 1872. Creation of the map “stoodon the shoulders” of prior iterations to present new results from adecade of work by scientists from the MGS and other institutions.The map conveys a new level of insight into the rocks that formour landscape, that record evolution of the earth’s crust, and thatsupply much of our water and mineral resources. The state-widegeologic map serves several important functions. First, it representsa status report of our current understanding of the State’sgeology. Secondly, it provides a broad context within which tointerpret detailed maps where they exist. And finally, it providesa jumping off point to direct future scientific and resource evaluations.The map was constructed by six geologists and a numberof GIS staff over a period of 3 years. Funding was provided bythe Minnesota Legislature, administered by the Minerals CoordinatingCommittee, and by the State Special Appropriation tothe MGS. Crucial to the new level of detail was comprehensiveinformation compiled in the state water well database, andsurveys based on rock magnetism and density. Both data setsallow geologists to image the crust beneath younger layers of rockand sediment. Because detailed maps of all parts of Minnesotahave not yet been published, this compilation presents the mostaccurate depiction available for some areas of the state. Computerfiles that accompany the map allow the user to lift off youngerlayers of rock to reveal what is inferred to lie beneath, which adds30% more geologic interpretation than on previous iterations.Corresponding GIS data tables permit attribute searches based onage, terrane, and lithologic and nomenclatural subdivisions. Ancillaryfiles, published as MGS Open-File Report OF10-02, includenew state-wide databases and maps of outcrops, bedrock topography,depth to bedrock, and geochronologic data.The map reference number is S-21, a part of the MinnesotaGeological Survey’s State Map Series. It can be viewed on theMGS web site (www.mngs.umn.edu), and prints (size: 4 feet X 5feet) can be ordered there as well. A companion map, S-22, is adigital-only and print-on-demand version showing Precambriangeology. For more information, contact:Map Sales Department of the Minnesota GeologicalSurvey; 612-627-4780, ext. 238Mark Jirsa, Geologist and lead compiler of the maps,Minnesota Geological Survey, College of Science andEngineering, University of Minnesota, 612-627-4780,ext 208 or jirsa001@umn.edu.Original 1872 geological map of Minnesota by N.H. Winchell (left) contrasted with the 2011 bedrock geology map (S-21) on right.Alumni NewsletterPage 13