Neoproterozoic glaciation on a carbonate platform margin in Arctic Alaska and the origin of the North Slope subterrane

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Neoproterozoic glaciation on a carbonate platform margin in Arctic Alaska and the origin of the North Slope subterrane

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Title: Neoproterozoic glaciation on a carbonate platform margin in Arctic Alaska and the origin of the North Slope subterrane
Author: Macdonald, Francis Alexander; McClelland, William C.; Schrag, Daniel P.; Macdonald, Winston P.

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Citation: Macdonald, Francis A., William C. McClelland, Daniel P. Schrag, and Winston P. Macdonald. 2009. “Neoproterozoic Glaciation on a Carbonate Platform Margin in Arctic Alaska and the Origin of the North Slope Subterrane.” Geological Society of America Bulletin 121 (3-4) (February 5): 448–473. doi:10.1130/b26401.1.
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Abstract: The rotation model for the opening of the Canada Basin of the Arctic Ocean predicts stratigraphic links between the Alaskan North Slope and the Canadian Arctic islands. The Katakturuk Dolomite is a 2080-m-thick Neo protero zoic carbonate succession exposed in the northeastern Brooks Range of Arctic Alaska. These strata have previously been correlated with the pre– 723 Ma Shaler Supergroup of the Amundson Basin. Herein we report new composite δ13C profi les and detrital zircon ages that test this connection. We go further and use stratigraphic markers and a compilation of δ13C chemostratigraphy from around the world, tied to U-Pb ages, to derive an age model for deposition of the Katakturuk Dolomite. In particular, we report the identifi cation of ca. 760 Ma detrital zircons in strata underlying the Katakturuk Dolomite. Moreover, a diamictite present at the base of the Katakturuk Dolomite is capped by a dark-colored limestone with peculiar roll-up structures. Chemostratigraphy and lithostratigraphy suggest this is an earlyCryogenian glacial diamictite-cap carbonate couplet and that deposition of the Katakturuk Dolomite spanned much of the late Neoproterozoic. Approximately 500 m above the diamictite, a micropeloidal dolomite, with idiosyncratic textures that are characteristic of basal Ediacaran cap carbonates, such as tubestone stromatolites, giant wave ripples, and decameters of pseudo morphosed former aragonite crystal fans, rests on a silicifi ed surface. Chemostratigraphic correlations also indicate a large increase in sedimentation rate in the upper ~1 km of the Katakturuk Dolomite and in the overlying lower Nanook Limestone. We suggest that the accompanying increase in accommodation space, along with the presence of two low-angle unconformities within these strata, are the product of late Ediacaran rifting along the southern margin of the North Slope subterrane. There are no strata present in the Amundson Basin that are potentially correlative with the late Neoproterozoic Katakturuk Dolomite, as the Cambrian Saline River Formation rests on the ca. 723 Ma Natkusiak Formation. Detrital zircon geochronology, chemostratigraphic correlations, and the style of sedimentation are inconsistent with both a Canadian Arctic origin of the North Slope subterrane and a simple rotation model for the origin of the Arctic Ocean. If the rotation model is to be retained, the exotic North Slope subterrane must have accreted to northwest Laurentia in the Early to Middle Devonian.
Published Version: doi:10.1130/B26401.1
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