New detrital zircon U-Pb data from the Farewell terrane of interior Alaska illuminate its early provenance evolution and connections with other Alaskan terranes. Five samples come from Neoproterozoic units in the central Farewell terrane. Basal “ferruginous beds” and the overlying Windy Fork Formation have prominent detrital zircon age populations between 2000 and 1800 Ma, with the Windy Fork Formation also having major age peaks between 700 and 600 Ma. Younger (Lone Formation) samples yield grains mainly between 750 and 550 Ma, with fewer older Proterozoic grains. Eleven samples come from deep-water early Paleozoic rocks (southeastern Farewell terrane). Ordovician sandstone (Post River Formation) has a major age population at ca. 490 Ma and subordinate 785–550 Ma populations that overlap age peaks in the Lone Formation. Turbidites in the overlying Terra Cotta Mountains Sandstone (Silurian) yield distinctly different spectra, with major ca. 450–420 Ma age populations and numerous grains between 2000 and 900 Ma. Devonian Barren Ridge Limestone samples have spectra like those of the Terra Cotta Mountains Sandstone, plus some Early Devonian grains. The Silurian shift in detrital zircon age spectra coincides with a major influx of siliciclastic sediment suggestive of a tectonic (collisional?) event involving the Farewell terrane. Neoproterozoic through Devonian successions in the Arctic Alaska–Chukotka and Alexander terranes show a similar up-section shift in detrital zircon spectra, supporting links between these terranes and the Farewell terrane during the early Paleozoic. Detrital zircon ages from the White Mountains and Livengood terranes, adjacent to the northern Farewell terrane, include major early Paleozoic populations that overlap those seen in partly coeval Farewell strata.
Neoproterozoic–early Paleozoic provenance evolution of sedimentary rocks in and adjacent to the Farewell terrane (interior Alaska)
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Julie A. Dumoulin, James V. Jones, Dwight C. Bradley, Alison B. Till, Stephen E. Box, Paul O’Sullivan; Neoproterozoic–early Paleozoic provenance evolution of sedimentary rocks in and adjacent to the Farewell terrane (interior Alaska). Geosphere doi: https://doi.org/10.1130/GES01470.1
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