THE BASEMENT OF THE MICHIGAN BASIN

What lies beneath the Michigan basin?  We know that the southeastern "arm" of the midcontinent rift zone swings south through southern Michigan (see below).  But what other rocks were present, before the sedimentation episodes of the Paleozoic began?

The map below may help answer this question.  The rift zone is shown as an area of extrusive rocks (lavas), mafic rocks (dark, rich in iron and heavy minerals) and gneisses.   Other parts of the region are underlain by volcanic rocks and gneisses. 

This material has been compiled for educational use only, and may not be reproduced without permission.  One copy may be printed for personal use.  Please contact Randall Schaetzl (soils@msu.edu) for more information or permissions.