Structural geology of the Gogebic Range, Penokean orogen northern Michigan and Wisconsin
- Western Illinois Univ., Macomb, IL (United States). Dept. of Geology Geological Survey, Macomb, IL (United States)
- Univ. of Wisconsin, Oshkosh, WI (United States). Dept. of Geology Geological Survey, Oshkosh, WI (United States)
The Gogebic Iron Range extends for some 100 km from near Clam Lake, northwestern Wisconsin to Lake Gogebic, westernmost northern Michigan. It consists of an allochthonous package of Early Proterozoic (EP) strata sandwiched between Archean basement rocks on the south and unconformably overlying Middle Proterozoic (MP) Keweenawan strata on the north. Volcanic rocks occur at either end of the Gogebic range, but the central part of the range consists mainly of monoclinically north-dipping sedimentary strata. Initial phases of Penokean deformation detached Early Proterozoic strata from underlying Archean basement and created northverging, bedding-parallel shears in the monoclinal sequence. Exposures of mylonitized rocks at several places along the length of the district demonstrate the allochthonous nature of EP strata. The main zones of detachment are the shaly portions of the Sunday Quartzite and Palms Formation. Bedding and the shear zones were next deformed into northeast and northwest-plunging folds, most prominently at the east and west ends of the range respectively. Subsequent deformation involved faulting of both the Archean and EP strata. During formation and closure of the MP Midcontinent Rift, the Pre-Keweenawan strata were tilted steeply northward along listric thrusts (Cannon et al, 1993), resulting in a northwestern-oriented, strike-parallel, cross-sectional view of the Pre-Keweenan crust.
- OSTI ID:
- 6906291
- Report Number(s):
- CONF-9404217-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 26:5; Conference: 27. annual conference of the North-Central Section of the Geological Society of America (GSA), Kalamazoo, MI (United States), 28-29 Apr 1994; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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