Date of Award


Document Type

Open Access Master's Report

Degree Name

Master of Science in Geology (MS)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

James DeGraff

Committee Member 1

William Rose

Committee Member 2

Chad Deering

Committee Member 3

Jeremy Shannon


The Keweenaw Fault (KF) has been interpreted as a rift-bounding normal fault along the southern margin of the Midcontinent Rift System; later inverted into a reverse fault by a tectonic compression event. The fault trends NNE to NE for most of its trace but curves clockwise to ESE along the Bête Grise Bay area in Michigan’s Keweenaw Peninsula. U.S. Geological Survey maps depict the KF along Bête Grise Bay as a continuous thrust that follows a sinuous contact between Portage Lake Volcanics (PLV) and Jacobsville Sandstone (JS). New fieldwork reveals a left-stepping en echelon system of ESE-trending faults connected by ENE trending faults. SE-dipping PLV layers are interpreted as the south flank of an anticlinal structure along the shoreline south of Bare Bluff. Three PLV-JS contacts previously mapped as being faulted are now interpreted as unconformities. Fault slip indicators recorded on 34 fault surfaces show that overall movement on the fault system in this area has a ratio of strike slip to dip slip of 2:1. Field relationships indicate that PLV units were deformed by faulting and folding prior to JS deposition, with lesser deformation occurring after JS deposition.

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