Geology of Minnesota: a centennial volume, Plate 2
Description
Bouguer gravity anomaly map (anomaly related to different densities of rocks in the upper crust, Bouguer anomaly is a corrected difference between an observed gravity measurement and value predicted from a generalized earth model), showing Midcontinent gravity high, scale 1 inch = about 45 miles.
Morey, G.B., Sims, Paul K. (1972). Geology of Minnesota: a centennial volume, Plate 2. Minnesota Geological Survey. https://reflections.mndigital.org/catalog/mgs:1004 (map)