Let's go back in time to approximately 1.8 billion years. Mountains towering over the future Wisconsin landscape and volcanoes spewing lava and ash. That is the setting for the Utley Rhyolite. This excerpt from Gene LeBarge states, "The Utley Rhyolite is one of ten isolated knobs of Precambrian igneous rocks (mainly rhyolites) that protrude through the Paleozoic cover in southeastern Wisconsin. The inliers extend from Berlin southwestward to the Baraboo area. The rhyolites stood as prominent hills on the Precambrian surface, and were rocky islands in the lower Paleozoic seas for nearly a hundred million years
Smith (1974, 1975, in press) has shown that the various rhyolites in southern Wisconsin formed from ash-flow deposits and chemically are genetically related. Author : Gene L. LaBerge"
https://wgnhs.wisc.edu/pubshare/OUT-GL01.pdf
Special thanks to Dan Posthuma for allowing our club to explore the quarry.
