For 40 years, beginning in 1882, the Lake Superior Division of the USGS in Madison, Wisconsin documented the geology of the Lake Superior area. The division primarily worked in Wisconsin, Minnesota, Michigan’s Upper Peninsula, and Ontario. Over the course of its work, the division produced a number of publications on the region’s Precambrian geology. R.D. Irving, the first director, did pioneering work in the field of microscopic
petrography and was the first to use thin sections in a large-scale survey.
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