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Paper No. 3
Presentation Time: 9:30 AM

COMPARATIVE PROVENANCE APPROACHES FOR CONSTRAINING TRENDS IN EXHUMATION, SEDIMENT DISPERSAL, AND PALEOGEOGRAPHY FROM UPPER PALEOZOIC STRATA OF THE FAREWELL TERRANE, SW ALASKA


HAMPTON, Brian A.1, KOROLESKI, Kraig J.1 and MALKOWSKI, Matthew A.2, (1)Dept. of Geological Sciences, New Mexico State University, P.O. Box 30001, Las Cruces, NM 88003-8001, (2)Dept. of Geological & Environmental Sciences, Stanford University, 450 Serra Mall, Bldg 320, Stanford, CA 94301-2115, bhampton@nmsu.edu

The Farewell terrane is located in the northernmost part of the North American Cordillera in SW Alaska and is defined by (1) Neoproterozoic-Devonian carbonate and clastic strata of the Nixon Fork subterrane, (2) Cambrian-Devonian clastic and carbonate strata of the Dillinger subterrane, and (3) Devonian-Jurassic(?) clastic strata of the Mystic subterrane. Although it is generally accepted that the Farewell terrane has Siberian origins, it is unclear whether the younger parts of the Farewell share paleogeographic links with the Arctic margin. Presented here are new sandstone modal composition trends, U-Pb detrital geochronology, and Hf isotopic analyses from upper Paleozoic synorogenic strata of the Dillinger and Mystic subterranes, all of which outcrop along the western margin of the Alaska Range.

U-Pb detrital zircon age spectra from Silurian-Devonian strata of the Dillinger subterrane show primary peak ages between 425-450 Ma and secondary peak ages between 550-700 Ma. Paleozoic-Neoproterozoic detrital zircons exhibit both enriched (-1 to -15) and depleted (+2 to +14) epsilon Hf values. Modal composition trends reveal pervasive occurrences of mono- and polycrystalline quartz (~46%) and subordinate occurrences of chert, plagioclase, and lithic metamorphic and volcanic fragments. Overall, provenance trends reflect strong contributions from recycled orogen source areas that likely included both enriched and depleted mantle reservoirs.

U-Pb detrital age spectra from Devonian-Permian strata of the Mystic subterrane show primary peak ages between 280-310, 330-375, and 415-460 Ma and secondary peak ages between 1820-1980 Ma. Pennsylvanian-Permian detrital zircons exhibit depleted epsilon Hf values (+2 to +14) whereas Devonian-Mississippian zircons have enriched signatures (epsilon Hf values between -5 and -35). Ordovician-Silurian zircons exhibit both enriched (-5 to -25) and depleted (+5 to +14) epsilon Hf values. Compositional trends show a relative abundance of lithic volcanic fragments (~65%) and subordinate occurrences of chert and lithic sedimentary fragments. Overall, provenance trends reflect contributions from arc source areas that included enriched and depleted mantle reservoirs.

Session No. 56

T190. The Life and Death of Mobile Belts along the North American Cordillera: Advances in Understanding the Long- Term Construction of Continental Margins (Posters)
Sunday, 27 October 2013: 9:00 AM-6:30 PM
Hall D (Colorado Convention Center)
Geological Society of America Abstracts with Programs. Vol. 45, No. 7, p.165
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