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Reconstruction of an early Paleozoic continental margin based on the nature of protoliths in the Nome Complex, Seward Peninsula, Alaska

By
Alison B. Till
Alison B. Till
U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA
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Julie A. Dumoulin
Julie A. Dumoulin
U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA
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Robert A. Ayuso
Robert A. Ayuso
U.S. Geological Survey, National Center, Reston, Virginia 20192, USA
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John N. Aleinikoff
John N. Aleinikoff
U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, USA
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Jeffrey M. Amato
Jeffrey M. Amato
New Mexico State University, Las Cruces, New Mexico 88003, USA
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John F. Slack
John F. Slack
U.S. Geological Survey, National Center, Reston, Virginia 20192, USA
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W.C. Pat Shanks, III
W.C. Pat Shanks, III
U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, USA
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Published:
July 01, 2014

The Nome Complex is a large metamorphic unit that sits along the southern boundary of the Arctic Alaska–Chukotka terrane, the largest of several microcontinental fragments of uncertain origin located between the Siberian and Laurentian cratons. The Arctic Alaska–Chukotka terrane moved into its present position during the Mesozoic; its Mesozoic and older movements are central to reconstruction of Arctic tectonic history. Accurate representation of the Arctic Alaska–Chukotka terrane in reconstructions of Late Proterozoic and early Paleozoic paleogeography is hampered by the paucity of information available. Most of the Late Proterozoic to Paleozoic rocks in the Alaska–Chukotka terrane were penetratively deformed and recrystallized during the Mesozoic deformational events; primary features and relationships have been obliterated, and age control is sparse.

We use a variety of geochemical, geochronologic, paleontologic, and geologic tools to read through penetrative deformation and reconstruct the protolith sequence of part of the Arctic Alaska–Chukotka terrane, the Nome Complex. We confirm that the protoliths of the Nome Complex were part of the same Late Proterozoic to Devonian continental margin as weakly deformed rocks in the southern and central part of the terrane, the Brooks Range. We show that the protoliths of the Nome Complex represent a carbonate platform (and related rocks) that underwent incipient rifting, probably during the Ordovician, and that the carbonate platform was overrun by an influx of siliciclastic detritus during the Devonian. During early phases of the transition to siliciclastic deposition, restricted basins formed that were the site of sedimentary exhalative base-metal sulfide deposition. Finally, we propose that most of the basement on which the largely Paleozoic sedimentary protolith was deposited was subducted during the Mesozoic.

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GSA Special Papers

Reconstruction of a Late Proterozoic to Devonian Continental Margin Sequence, Northern Alaska, Its Paleogeographic Significance, and Contained Base-Metal Sulfide Deposits

Julie A. Dumoulin
Julie A. Dumoulin
U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA
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Alison B. Till
Alison B. Till
U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA
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Geological Society of America
Volume
506
ISBN print:
9780813725062
Publication date:
July 01, 2014

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