Archean to Anthropocene: Field Guides to the Geology of the Mid-Continent of North America
This volume of 25 field guides plus one paper on field instruction was prepared in conjunction with the 2011 GSA Annual Meeting in Minneapolis, Minnesota. The diverse slate of field trips spans a geologically broad range of topics, including the Precambrian geology of the southern Canadian Shield; the economic geology of the Lake Superior region; Phanerozoic strata in Minnesota, Wisconsin, Iowa, and North Dakota; glacial geology; hydrogeology and limnology; undergraduate and K12 geoscience field education; archaeological investigations in the upper Mississippi River valley; and geology by bicycle.
Classic Precambrian geology of northeast Minnesota
Published:January 01, 2011
Mark A. Jirsa, John C. Green, 2011. "Classic Precambrian geology of northeast Minnesota", Archean to Anthropocene: Field Guides to the Geology of the Mid-Continent of North America, James D. Miller, George J. Hudak, Chad Wittkop, Patrick I. McLaughlin
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This field trip is an overview of Precambrian terranes in northeastern Minnesota using some of the most illustrative and accessible exposures—the term "classic" refers to the fact that many were the basis for earliest geologic study of the Precambrian and continue to be exemplary. The geology is presented in the context of major orogenic, rifting, and meteorite impact events during evolution of the North American continent. The Archean rocks are the products of three periods of orogenesis: the ca. 2695 Ma Shebandowanian orogeny that created major folds and thrust stacks; the ca. 2680 Ma Minnesotan orogeny that produced regional transpressive fabrics, folds, and metamorphism to greenschist-amphibolite grade; and a third event that produced localized faulting and folding of earlier structures and fabrics. The Sheban-dowanian may represent collision of the Wawa subprovince with the composite Superior superterrane to the north. The Minnesotan can be attributed to oblique collision of the Minnesota River Valley subprovince with the Superior superterrane. Structures bounding major components of the Superior Province are locally inferred to be thrust faults that formed during terrane assembly. Their vergence and offset histories are derived from seismic surveys in Minnesota and extrapolation from Lithoprobe and NATMAP transects in adjacent Canada. The Paleoproterozoic rocks are the products of three orogenic and rifting events, reflecting continued continental growth at Geons 18, 17, and 16. Mesoproterozoic rocks result from Geon 11 continental rifting, producing volcanic and sedimentary rocks of the Keweenawan Supergroup and plutonic rocks of the Midcontinent Rift Intrusive Supersuite.