24-5 Mesozoic detrital zircon Hafnium data from the Kandik and Manley Basins discern Arctic island arc from Yukon-Tanana orogenic provenance during northern Cordillera assembly

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records, Part I

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The Kandik and Manley Basins of east-central Alaska lie near the intersection of Arctic, North American, and Intermontane Terranes and thus contain sediments that may encode evolving tectonic configurations during the assembly of the northern Cordillera. Detrital zircon U-Pb (DZ) data from Kandik Basin Neocomian (145-130 Ma) quartzites and arenites are dominated by 0.9-2.0 Ga and ~2.7 Ga Laurentian grains that suggest derivation from cratonic provenance areas. In contrast, the Kandik Basin Aptian-Albian (125-100 Ma) Kathul Greywacke contains volcaniclastic deepwater deposits with an influx of 150-230 Ma DZ grains that signify a major change in provenance. To the west and across the Tintina fault, the Manley Basin exhibits a similar upsection shift to 150-230 Ma DZ grains that occurs during the transition from early Cretaceous quartzites to the deepwater Wilber Creek unit.

The 150-230 Ma DZ grains have two potential source areas based solely on age. The grains may be derived from widespread syncollisional magmatism to the southeast that records Triassic–Jurassic accretion of the Yukon-Tanana terrane with the North American margin, followed by Cretaceous extension. Alternatively, the grains may be derived from a hypothesized Triassic-Jurassic oceanic island arc to the northwest that collided with the Arctic margin during the Jurassic-Cretaceous Brookian Orogeny. Recent zircon Hafnium isotope data suggest that the Arctic island arc source has juvenile eHf of +11 to +16 based on igneous clasts and DZ data in the eastern Yukon-Koyukuk Basin, whereas the Yukon-Tanana collisional orogenic source has more evolved eHf of -22 to +6 based on igneous bedrock data.

New eHf data from Kandik Basin Kathul Greywacke 150-230 Ma DZ grains are dominated by juvenile eHf of +10 to +17 that provides compelling evidence for an island arc source. In contrast, eHf from the Manley Basin Wilber Creek 150-230 Ma DZ grains vary spatially from predominantly juvenile eHf of +9 to +17 in the western basin, to more evolved eHf of -15 to +5 in the eastern basin, suggesting a west-east transition from island arc to collisional orogen source. Notably, map restoration based on alignment of the juvenile island arc eHf provenance in the western Manley Basin and western Kandik Basin suggests >400 km of dextral strike-slip offset along the Cenozoic Tintina-Victoria Creek fault system, comparable to several independent strike-slip estimates.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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