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Late Proterozoic-Paleozoic evolution of the Arctic Alaska-Chukotka terrane based on U-Pb igneous and detrital zircon ages; implications for Neoproterozoic paleogeographic reconstructions

Jeffrey M. Amato, Jaime Toro, Elizabeth L. Miller, George E. Gehrels, G. Lang Farmer, Eric S. Gottlieb and Alison B. Till
Late Proterozoic-Paleozoic evolution of the Arctic Alaska-Chukotka terrane based on U-Pb igneous and detrital zircon ages; implications for Neoproterozoic paleogeographic reconstructions
Geological Society of America Bulletin (September 2009) 121 (9-10): 1219-1235

Abstract

The Seward Peninsula of northwestern Alaska is part of the Arctic Alaska-Chukotka terrane, a crustal fragment exotic to western Laurentia with an uncertain origin and pre-Mesozoic evolution. U-Pb zircon geochronology on deformed igneous rocks reveals a previously unknown intermediate-felsic volcanic event at 870 Ma, coeval with rift-related magmatism associated with early breakup of eastern Rodinia. Orthogneiss bodies on Seward Peninsula yielded numerous 680 Ma U-Pb ages. The Arctic Alaska-Chukotka terrane has pre-Neoproterozoic basement based on Mesoproterozoic Nd model ages from both 870 Ma and 680 Ma igneous rocks, and detrital zircon ages between 2.0 and 1.0 Ga in overlying cover rocks. Small-volume magmatism occurred in Devonian time, based on U-Pb dating of granitic rocks. U-Pb dating of detrital zircons in 12 samples of metamorphosed Paleozoic siliciclastic cover rocks to this basement indicates that the dominant zircon age populations in the 934 zircons analyzed are found in the range 700-540 Ma, with prominent peaks at 720-660 Ma, 620-590 Ma, 560-510 Ma, 485 Ma, and 440-400 Ma. Devonian- and Pennsylvanian-age peaks are present in the samples with the youngest detrital zircons. These data show that the Seward Peninsula is exotic to western Laurentia because of the abundance of Neoproterozoic detrital zircons, which are rare or absent in Lower Paleozoic Cordilleran continental shelf rocks. Maximum depositional ages inferred from the youngest detrital age peaks include latest Proterozoic-Early Cambrian, Cambrian, Ordovician, Silurian, Devonian, and Pennsylvanian. These maximum depositional ages overlap with conodont ages reported from fossiliferous carbonate rocks on Seward Peninsula. The distinctive features of the Arctic Alaska-Chukotka terrane include Neoproterozoic felsic magmatic rocks intruding 2.0-1.1 Ga crust overlain by Paleozoic carbonate rocks and Paleozoic siliciclastic rocks with Neoproterozoic detrital zircons. The Neoproterozoic ages are similar to those in the peri-Gondwanan Avalonian-Cadomian arc system, the Timanide orogen of Baltica, and other circum-Arctic terranes that were proximal to Arctic Alaska prior to the opening of the Amerasian basin in the Early Cretaceous. Our Neoproterozoic reconstruction places the Arctic Alaska-Chukotka terrane in a position near Baltica, northeast of Laurentia, in an arc system along strike with the Avalonian-Cadomian arc terranes. Previously published faunal data indicate that Seward Peninsula had Siberian and Laurentian links by Early Ordovician time. The geologic links between the Arctic Alaska-Chukotka terrane and eastern Laurentia, Baltica, peri-Gondwanan arc terranes, and Siberia from the Paleoproterozoic to the Paleozoic help to constrain paleogeographic models from the Neoproterozoic history of Rodinia to the Mesozoic opening of the Arctic basin.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 121
Serial Issue: 9-10
Title: Late Proterozoic-Paleozoic evolution of the Arctic Alaska-Chukotka terrane based on U-Pb igneous and detrital zircon ages; implications for Neoproterozoic paleogeographic reconstructions
Affiliation: New Mexico State University, Department of Geological Sciences, Las Cruces, NM, United States
Pages: 1219-1235
Published: 200909
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 98
Accession Number: 2009-074679
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2009048
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N64°19'60" - N66°34'00", W168°04'60" - W161°19'60"
Secondary Affiliation: West Virginia University, USA, United StatesStanford University, USA, United StatesUniversity of Arizona, USA, United StatesUniversity of Colorado, USA, United StatesU. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200940
Program Name: USGSOPNon-USGS publications with USGS authors
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