--> Abstract: Pre-opening Paleogeography of the CA Basin Margins: Insights from Detrital Zircon Geochronology, by Eric Gottlieb; #90177 (2013)

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Pre-opening Paleogeography of the CA Basin Margins: Insights from Detrital Zircon Geochronology

Eric Gottlieb

The counterclockwise rotation of Arctic Alaska (AA) relative to the Canadian Arctic (CA) margin is a popular plate kinematic model for Mesozoic opening of the CA Basin. Both the AA and CA margins share a long (>150 m.y.) history of passive-margin deposition and were affected by breakup unconformities associated with the opening of the basin. The rotation model implies that prior to the rift opening, basins on the CA and AA margins had sediment sources along a high that paralleled the trend of both margins. Northerly-derived Permian-Middle Jurassic strata in the Sverdrup Basin were derived from Crockerland- a landmass that previously flanked the CA margin. In the North Slope basin of AA, carbonate and northerly-derived clastic strata of the Mississippian to Triassic Ellesmerian Sequence progressively onlapped the Barrow Arch, incrementally burying pre-Mississippian rocks from south to north, and requiring sediment input from a similarly cryptic upland source to the north. We test the rotation model hypothesis by analyzing the detrital zircon (DZ) populations from eight subsurface stratigraphic intervals in National Petroleum Reserve, Alaska and four outcrop exposures in the northeastern Brooks Range. The oldest sample, a fluvial sandstone of the Mississippian Kekiktuk Formation is dominated by ~373 Ma zircons and is interpreted to be locally derived from plutons and argillite beneath the pre-Mississippian unconformity. During the northward onlap of the Lisburne carbonate platform across this unconformity, a change in sediment source region is inferred based on a significant decrease in the percentage of Paleozoic zircons in stratigraphically higher samples. DZ populations of Lisburne and younger samples are statistically similar along strike of the North Slope basin and through time, and exhibit a trend of younger samples containing proportionately less Devonian-age grains than the older samples. A comparison of our results with DZ data from the CA Islands (Anfinson et al., GSAB, 2011) suggests that post-Kekiktuk strata we analyzed were likely sourced from uplifted Devonian clastic wedge strata that were lateral equivalents of the mapped Middle-Late Devonian strata of the Franklinian Basin of the CA. These results support the rotational model (e.g., Embry, Marine Geol., 1990) whereby the Beaufort margin of AA is conjugate to part of the CA margin and that some amount of Laurentian-affinity crust was likely once positioned between the two margins and later thinned and buried by the opening of the basin.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013