Thick-Skinned, South-Verging Backthrusting in the Felch and Calumet Troughs Areaof the Penokean Oregon, Northern Michigan (Chapter L). Contribution to Precambrian Geology of Lake Superior Region

摘要

In the report the authors point out that although the Bush Lake fault is a majornorth-verging structure, consistent with the overall sense of northward tectonic transport of the Penokean orogen in northern Michigan and adjacent Wisconsin, the structures in the Felch and Calumet troughs area are south-verging. The south-verging structures, which deform Archean basement as well as rocks of the Early Proterozoic Marquette Range Supergroup, are interpreted as out-of-sequence backthrusts and backfolds that developed to accommodate abrupt changes in crustal thickness along the continental margin caused by thrusting. The authors' study did nt confirm the existence of an inverted Early Proterozoic stratigraphy throughout the area of the Felch and Calumet troughs.