Frac Sand Production in the Midwest

Surface exposures of frac sand source units in the upper Midwest. Shown are the St. Peter Sandstone (green); the Cambrian, undivided (lavender) that includes the Jordan, Wonewoc, and Mount Simon Formations; the Jordan Formation in Iowa and its equivalent Trempealeau Formation in Michigan (red), the Wonewoc Formation in Iowa and its equivalent Munising Formation in Michigan (pink); and the Mount Simon Formation in narrow outcrops in extreme northeastern Iowa (orange).