Quaternary Geology of Michigan, W. R. Farrand, 1982.  Also call "Glacial' or "Surficial" by some geologists.  This map shows what is fond at the surface.  Access this file using the following link:
http://www.michigan.gov/documents/deq/1982_Quaternary_Geology_Map_301467_7.pdf

Bedrock Geology Map, Colored map of the aerial extent of geologic formations.  This shows the patter of the bedrock that is under the glacial sands, gravels and clays that blanket Michigan.  Access this file using the following link:
http://www.michigan.gov/documents/deq/1987_Bedrock_Geology_Map_301466_7.pdf

Geologic Cross Section and Generalized bedrock Geology Map.  Access this file using the following link:
http://www.michigan.gov/documents/deq/Bedrock_and_cross_section_301678_7.pdf

Oil and Gas Map, A map showing the distribution of Oil & Gas wells in the state.  Access thi file using the following link:
http://www.michigan.gov/documents/deq/deq-ogs-gimdl-GGMOG05_310107_7.PDF  

Michigan Coal Reserves, J. Kalliokoski, E. J. Welch, 1976, Coal, Southern Peninsula, geologic maps.  Access this file using the following link:
http://www.michigan.gov/documents/deq/GIMDL-COAL-MAPS-USBM76_307761_7.pdf  

Many more reference materials are available as part of the Digital Geology Library.  Access the catalog using the following link:
http://www.michigan.gov/documents/deq/GIMDL-Catalog-2010-01-20_307979_7.pdf