HR: 09:15h
AN: T11E-06    [Abstracts]
TI: Chemo- and litho-stratigraphy of the Neoproterozoic Katakturuk Dolomite, northeastern Brooks Range, Alaska, and implications for the origin of the Arctic Alaska-Chukotka Plate
AU: * Macdonald, F A
EM: fmacdon@fas.harvard.edu
AF: Harvard University Department of Earth & Planetary Sciences, 20 Oxford St., Cambridge, MA 02138, United States
AU: Schrag, D P
EM: schrag@eps.harvard.edu
AF: Harvard University Department of Earth & Planetary Sciences, 20 Oxford St., Cambridge, MA 02138, United States
AB: The Katakturk Dolomite is a 2.2 km thick Neoproterozoic carbonate succession exposed in the northeastern Brooks Range of Alaska. A diamictite at the base of the Katakturuk is capped by a black limestone with peculiar roll-up structures. Carbon-isotope chemo-stratigraphy suggests this is a Sturtian-age glacial deposit. Approximately 500 meters above the diamictite, textures characteristic of a basal Ediacaran cap carbonate, such as tubestone stromatolites, giant wave ripples, and decameters of pseudomorphosed former aragonite crystal fans rest on a silicified surface. This basal Ediacaran cap carbonate (herein refered to as the Nularuvik cap carbonate) is followed by an additional 1.7 km of unfossiliferous, Ediacaran-age shallow water dolomites. The ca. 580 Ma Gaskiers glaciation is tentatively correlated with a major exposure surface of vadose pisoids, approximately 500 meters above the Nularvik cap carbonate. This surface is capped by another aragonite crystal fan horizon that harbors depleted carbon isotope values (- 4.5 per mil). Deposition of the Katakturuk ceases before the ca. 555 Ma Shuram-Wonoka negative carbon-isotope anomaly. The Nanook Limestone rests unconformably on the Kataktruk Dolomite and begins deposition in the Botomian with on-lap from the south. The age and style of Neoproterozoic carbonate sedimentation on the Arctic Alaska-Chukotka Plate (AACP) are both inconsistent with a Laurentian origin of the AACP and with the simple "windshield wiper" model for the opening of the Arctic Ocean. We suggest instead that the Katakturuk Dolomite was deposited as the AACP shared a margin either with Siberia or a peri-Siberian terrane. In our model the AACP rifted away in the Early Cambrian, accommodating the deposition of the Nanook Limestone, whereupon it traveled alone throughout much of the Early Paleozoic. In the Late Silurian-Early Devonian, the AACP experienced a northern extension of the Caledonian orogeny. The AACP arrived at its present position by way of Late Paleozoic-Mesozoic synstral shearing along the Canadian Arctic margin. This model is consistent with detrital zircon geochronology, biogeographic affinities of Paleozoic fauna, the geological record of both Arctic Canada and Alaska, and the morphology of the Arctic Ocean.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1165 Sedimentary geochronology
DE: 8157 Plate motions: past (3040)
DE: 9315 Arctic region (0718, 4207)
DE: 9619 Precambrian
SC: Tectonophysics [T]
MN: 2007 Fall Meeting