HR: 17:45h
AN: GP44A-08    [Abstracts]
TI: Detrital Zircon U-Pb Ages From Northern Alaska and Northern Canada: Implications for Opening of the Canada Basin
AU: * Moore, T E
EM: tmoore@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, MS 969, Menlo Park, CA 94025 United States
AU: Miller, E L
EM: miller@pangea.stanford.edu
AF: Geological and Environmental Sciences, Stanford University, Stanford, CA 940305 United States
AU: Embry, A
EM: AEmbry@NRCan.gc.ca
AF: Geological Survey of Canada, 3303 33rd St., NW, Calgary, Alb T2L 2A7 Canada
AU: Aleinikoff, J N
EM: aleinikoff@usgs.gov
AF: U.S. Geological Survey, P.O Box 25046, MS 963, Denver, CO 80225 United States
AU: Gehrels, G E
EM: ggehrels@geo.arizona.edu
AF: Department of Geosciences, University of Arizona, Tucson, AZ 85721-0077 United States
AB: Detrital zircons from five Paleozoic and Mesozoic sandstones from the Brooks Range and North Slope of Alaska, and two Triassic sandstones from the Sverdrup Basin in northern Canada were dated using SHRIMP and laser ablation ICPMS geochronology. In Alaska, dated samples from allochthonous strata of the Brooks Range include the northern and southern lithofacies of the Devonian and(or) Mississippian Kanayut Conglomerate near the Trans-Alaska Pipeline and the Valanginian Tingmerkpuk Sandstone in the western Brooks Range. Also dated are zircons from autochthonous strata of the North Slope foreland, including the Lower Triassic Ivishak Sandstone in the Sadlerochit Mountains and a Hauterivian sandstone from the Jurassic and Lower Cretaceous Kingak Shale in the Tunalik well. In Canada, dated samples are from the Lower Triassic Bjorne Formation and the Upper Triassic Pat Bay Formation on the southeastern and northern margins of the Sverdrup Basin, respectively. The two Valanginian samples from Alaska and the Bjorne Formation in Canada yielded generally similar results dominated by 1.0 to 2.0 Ga zircons, with lower Paleozoic (especially 420 to 450 Ma) and less abundant Archean zircons. Samples from the Triassic Ivishak and Pat Bay Formations also are similar, but are dominated by 530 to 570 Ma zircons with less abundant older zircons. The two samples of Kanayut Conglomerate, in contrast, are dominated by 430 to 400 Ma zircons and yielded only minor amounts of Proterozoic zircons. The similarities between the Sverdrup Basin and northern Alaska samples suggest they were derived from similar source areas and lend support to models that call for opening of the Canada Basin by counterclockwise rotation of northern Alaska and Chukotka in the Early Cretaceous. Moreover, the Alaskan samples, all derived from generally northerly source areas, may indicate that unroofing in the source area progressed from strata rich in 450 to 400 Ma zircons in the Devonian to rocks yielding abundant Proterozoic and Archean zircons in the Early Cretaceous deposits. This pattern is consistent with the unroofing sequence interpreted from Nd isotopic data from the Sverdrup Basin by Patchett and others (2004, J. Geology, p. 39 to 57), who concluded that detritus from 450 to 350 Ma tectonism in the Caledonian and Ellesmerian orogens covered Arctic Canada until it was progressively removed in the Mesozoic.
DE: 9315 Arctic region
DE: 8110 Continental tectonics--general (0905)
DE: 8157 Plate motions--past (3040)
DE: 3675 Sedimentary petrology
DE: 1035 Geochronology
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting