Abstract

The Neruokpuk Formation is a Neoproterozoic and Cambrian turbiditic succession in northwesternmost Yukon (Canada) and northeastern Alaska (USA), part of a latest Proterozoic to Early Devonian slope and basin succession that is correlated in detail with strata in Selwyn Basin of the northern Canadian Cordillera. It includes quartz-lithic sandstone, locally containing altered detrital feldspar and muscovite indicating that a metamorphic source contributed detritus to the unit. The muscovite yields disturbed Ar-Ar spectra suggesting ages of 1800–1900 Ma. Detrital zircon distributions are dominated by 1800–2000 Ma grains with subsidiary populations of 1000–1600 Ma, 2300–2500 Ma and 2600–2800 Ma grains, consistent with a hybrid provenance dominated by a Laurentian cratonic source. Additional populations are derived from recycled Mackenzie Mountains and possibly Wernecke Supergroups. Integrating the geochronology with the regional stratigraphic setting, structural history, and geochemistry leads to the conclusion that the Neruokpuk Formation was deposited near its present location as part of the autochthonous northwest Laurentian continental margin. Therefore, the eastern part of Arctic Alaska, underlain by the Neruokpuk Formation, has a history that is distinct from the allochthonous western part(s) of the Arctic Alaska terrane. However, the rest of Arctic Alaska is structurally and stratigraphically linked to the eastern part by Late Devonian time.

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