The Penokean orogeny was a collision between three crustal terranes: a mafic volcanic arc sandwiched between continental terranes to the north and south. The northern suture is the Niagara Fault (no connection whatever to the Silurian Niagara Escarpment) and the southern is the Eau Pleine Shear Zone. The continental terranes underthrust the volcanic arc and outliers of arc rocks occur beyond both sutures. there may be additional thrust faults but the very poor exposure of both faults in most places leaves many details unresolved.
Created 11 Sep 1997, Last Update 04 April 2013
Not an official UW Green Bay site