GSA Connects 2021 in Portland, Oregon

Paper No. 143-7
Presentation Time: 9:40 AM


JONES III, Jamey, U.S. Geological Survey, Alaska Science Center, Anchorage, AK 99508, HOLM-DENOMA, Chris, U.S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center, Denver Federal Center, Denver, CO 80225, BRADLEY, Dwight, U.S. Geological Survey, 4210 University Drive, Anchorage, AK 99508 and O'SULLIVAN, Paul, GeoSep Services, GeoSep Services Inc., 1521 Pine Cone Road, Moscow, ID 83843

New geologic mapping and detrital zircon geochronology help to define age and provenance patterns of Mesozoic siliciclastic strata from the Manley basin in eastern interior Alaska that provide essential constraints on the assembly of accreted terranes in the northwestern Cordillera. Successions including the Wolverine quartzite and Wilber Creek/Minto units were deposited on pericratonic terranes such as Yukon-Tanana, Farewell/Livengood, and Ruby outboard of the northwestern Laurentia margin. The successions presently define a complex suture zone between the pericratonic terranes that has accommodated hundreds of km of shortening and strike-slip translation. On the northwestern side of the basin, the Late Jurassic–Early Cretaceous Wolverine quartzite appears restricted to the Ruby and (or) Livengood terranes. Circa 159–131 Ma maximum depositional ages from the quartz-rich Wolverine confirm limited fossil ages, and diverse older age populations suggest recycling of the Ruby and (or) Farewell terranes. To the southeast, the Lower Cretaceous Wilber Creek and Upper Cretaceous Minto units are less compositionally and texturally mature and have prominent ca. 200–150 Ma zircon age populations suggesting Yukon-Tanana terrane igneous sources. The successions and associated pericratonic terranes are all presently interleaved in folded and faulted panels that also contain slivers of other allochthonous terranes. Distinct provenance on either side of the Manley basin suggests that major shortening began in the Late Cretaceous and was likely completed prior to ca. 60 Ma plutonism that cross-cuts all of the deformed successions. Subsequent strike-slip displacement along major structures such as the Tintina and Victoria Creek faults continued to modify the terrane and suture zone geometries. Continuing work on the provenance and structural evolution of the siliciclastic successions will help further refine tectonic models for accretionary orogenesis at the apex of the Cordillera.