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Geologic mapping of the Kigluaik gneiss dome on Seward Peninsula, Alaska, was conducted at 1:24,000 scale and compiled with thesis maps and published maps as a colored map covering eight 15″ quadrangles at 1:63,360 scale. The Kigluaik dome consists of an exceptionally well-exposed 15-km-thick structural section of metasedimentary rocks and orthogneisses. A 91 ± 1 Ma upper-amphibolite-to-granulite facies metamorphic event that was syntectonic with gneiss dome fabrics overprints a pre–120 Ma blueschist-to-greenschist facies event. Peak conditions associated with younger metamorphism increase from greenschist facies in the structurally higher rocks of the Nome Group, through biotite, staurolite, sillimanite, and second sillimanite isograds to granulite facies in the rocks of the Kigluaik Group. The high-grade overprint is coeval with mantle-derived magmatism at 90 ± 1 Ma. Mafic magmatism provided heat for metamorphism and induced partial melting, also enabling flow of gneisses. Deformation thinned the crust as the gneiss dome was exhumed, collapsing isograds and juxtaposing rocks that equilibrated at dramatically different structural levels. Lineations in the gneiss dome record a rotation of stretching directions with structural depth. The continuous transition of lineation azimuth and the lack of overprinting relationships indicate orthogonal stretching directions at different structural levels in the gneiss dome during its formation. Based on regional geologic relations, it is likely that the Bering Strait gneiss domes developed within a continental arc that was undergoing extension, probably as the result of rollback of the north-dipping subducting slab along the Pacific margin during Late Cretaceous time.

Additional mapping contributions were made by: Phillip B. Gans, Department of Geological Sciences, University of California at Santa Barbara; Andrew T. Calvert, U.S. Geological Survey, Menlo Park, California; Timothy A. Little, School of Earth Sciences, Victoria University of Wellington, New Zealand; Kimberly A. Hannula, Department of Geology, Fort Lewis College, Durango, Colorado; Jeffrey Lee, Department of Geological Sciences, Central Washington University, Ellensburg, Washington; Charles M. Rubin, Department of Geological Sciences, Central Washington University, Ellensburg, Washington; Jaime Toro, Department of Geology and Geography, West Virginia University, Morgantown, West Virginia; and James E. Wright, Department of Geology, University of Georgia, Athens, Georgia.

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