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Michigan Geologic Map

Geologic Maps of the 50 United States

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Michigan's bedrock is not very widely exposed, so you should take this bedrock map with a grain of salt. (more below)
Michigan's rocks

Created by Andrew Alden from the U.S. Geological Survey's Geologic Map of the United States, 1974, by Philip King and Helen Beikman (fair use policy)

Click the map for a larger version
Much of Michigan is covered with glacial drift—ground-up Canadian rocks bulldozed onto Michigan and much of the rest of the northern United States by several Ice Age continental glaciers, like the ones that rest on Antarctica and Greenland today. Those glaciers also excavated and filled the Great Lakes that today make Michigan two peninsulas.

Beneath that blanket of sediment, the Lower Peninsula is a geologic basin, the Michigan Basin, that has been occupied by shallow seas for most of the last 500 million years as it slowly warped downward under the weight of its sediments. The central part filled in last, its shale and limestone dating from the Late Jurassic Period around 155 million years ago. Its outer rim exposes successively older rocks going back to the Cambrian (540 million years ago) and beyond on the Upper Peninsula.

The rest of the Upper Peninsula is a cratonic upland of very ancient rocks from as long ago as Archean times, nearly 3 billion years ago. These rocks include the iron formations that have supported the American steel industry for many decades and continue to be the nation's second-largest producer of iron ore. See a gallery of Michigan geological attractions.

I have prepared two other versions of the Michigan geologic map. The first version (2000x2400 pixels, 360 KB) has each named formation shown along with a key. The other, more aesthetically pleasing, is a scan of the state's 1968 map showing the rock units denoted by time instead of name, and it also includes the surrounding geography and avoids the floating-in-space effect. That's here in a 1200x1550 pixel version (840 KB)and a 2100x2700 pixel version (2 MB), because I can't bear to waste a good scan.

More about Michigan Geology

More Michigan resources on About.com:
About Detroit
Michigan Maps
Michigan Geography, State Symbols & Facts
Michigan National Parks
Michigan State Parks
Michigan Campgrounds
Michigan Scenic Roads

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