Deposits of the Lake Superior region

This digital map portrays the bedrock geology of the states of
Michigan, Wisconsin, and Minnesota taken from the most recent
published regional compilations. Some minor modifications and
generalizations have been made from the published maps. Information
on mineral deposits of the three states is from the U.S. Geological
Survey's Mineral Resource Data System (MRDS).
Version 3.0 supercedes the original report released in 1997. It
differs from the original map in having expanded attribute
information assigned to geologic units and updated shoreline and
state boundaries. The new attributes allow expanded capabilities
for producing derivative maps for attributes including stratigraphy,
lithology, and tectonic settings. The new shoreline and state
bounaries offer greater geographic accuracy than the originally
published version.