2011 GSA Annual Meeting in Minneapolis (912 October 2011)
402 Wednesday, 5 October 2011
10:00 AM-9:00 PM, Hilton Minneapolis: 11th Street Lobby

Structural Geology of the Subprovince Boundaries in the Archean Superior Province of Northern Minnesota and Adjacent Ontario

Primary Leader: Basil Tikoff
Leader(s): Robert L. Bauer, Dyanna M. Czeck, Peter Hudleston
Field Trip Description: The geometric, kinematic, and deformational features along the subprovince boundaries of the Archean Superior Province are keys to understanding the tectonic amalgamation of the province. This fieldtrip will visit some spectacular structural geology along two of the subprovince boundaries Wabigoon/Quetico & Quetico/Vermilion - of the Superior Craton. These boundaries separate the relatively high-grade gneisses of the Quetico Belt from typical low-grade granite-greenstone terranes to its north (Wabigoon) and south (Wawa). Both boundaries are characterized by different styles of transpressional deformation. This was the first place where transpression was recognized in Archean rocks, and one of the first regions of any age where vertical lineations and strike-slip shear indicators were recognized. The area provides excellent examples of phenomena noted worldwide in greenstone belts including deformation with recumbent folds lacking significant tectonic fabric and extensive panels of sedimentary rocks with steep dips and modest internal deformation. We will visit many classic outcrops including folded and boudinaged dikes, complexly folded banded iron formation, deformed turbidites with contrasting deformation in adjacent layers, deformed pillow basalts, anastomosing shear zones, and late stage brittle structures. In particular, we will visit a variety of strain magnitudes within the polymictic Seine conglomerate. We will tour the ductile-brittle Vermilion fault, a shear zone with vertical lineations and strike-slip shear indicators. We will visit outcrops of the Wakemup Bay tonalite, which was intruded into the hinge of a fold and subsequently offset along the fault. We will see evidence for regional variations in strain from strongly flattening to constrictional.
Field Trip will span: 4 days
Sponsor(s): Structural Geology and Tectonics Division of GSA (we assume this fieldtrip will be sponsored, but don't have official notification yet)

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