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Geochemical Constraints on the Provenance of Pre-Mississippian Sedimentary Rocks in the North Slope Subterrane of Yukon and Alaska

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Geochemical Constraints on the Provenance of Pre-Mississippian Sedimentary Rocks in the North Slope Subterrane of Yukon and Alaska The Geological Society of America Special Paper 541 Geochemical constraints on the provenance of pre-Mississippian sedimentary rocks in the North Slope subterrane of Yukon and Alaska Lyle L. Nelson Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA Justin V. Strauss Department of Earth Sciences, Dartmouth College, HB6105 Fairchild Hall, Hanover, New Hampshire 03755, USA Peter W. Crockford Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA Grant M. Cox Centre for Tectonics, Resources and Exploration (TraX), Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia Benjamin G. Johnson Department of Geology and Geography, West Virginia University, 98 Beechurst Avenue, Morgantown, West Virginia 26506, USA William Ward Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, Iowa 52242, USA Maurice Colpron Yukon Geological Survey, P.O. Box 2703 (K-14), Whitehorse, Yukon, Y1A 2C6, Canada William C. McClelland Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, Iowa 52242, USA Francis A. Macdonald Department of Earth Science, University of California, Santa Barbara, 1006 Webb Hall, Santa Barbara, California 93106, USA Nelson, L.L., Strauss, J.V., Crockford, P.W., Cox, G.M., Johnson, B.G., Ward, W., Colpron, M., McClelland, W.C, and Macdonald, F.A., 2018, Geochemical con- straints on the provenance of pre-Mississippian sedimentary rocks in the North Slope subterrane of Yukon and Alaska, in Piepjohn, K., Strauss, J.V., Reinhardt, L., and McClelland, W.C., eds., Circum-Arctic Structural Events: Tectonic Evolution of the Arctic Margins and Trans-Arctic Links with Adjacent Orogens: Geologi- cal Society of America Special Paper 541, p. 1–20, https://doi.org/10.1130/2018.2541(24). © 2018 The Geological Society of America. All rights reserved. For permission to copy, contact [email protected]. 1 Downloaded from https://pubs.geoscienceworld.org/books/chapter-pdf/4554404/spe541-24.pdf by GSA Content on 17 November 2018 2 Nelson et al. ABSTRACT The North Slope subterrane of Arctic Alaska extends from the northeastern Brooks Range of Alaska into adjacent Yukon, Canada, and includes a pre- Mississippian deep- water sedimentary succession that has been historically correlated with units exposed in the Selwyn basin of northwestern Laurentia. Sedimentary provenance data, includ- ing Sm-Nd isotopes and major and trace element geochemistry, provide detailed geo- chemical characterization of the regional pre- Mississippian strata of the North Slope subterrane. Combined with paleontological and geochronological age constraints, these new data record a marked shift in provenance in the Ordovician–Devonian(?) Clarence River Group, evidently linked to an infl ux of juvenile, arc-derived material. The timing and nature of this provenance change are consistent with early Paleozoic tectonic reconstructions of the Arctic margin that restore the North Slope subter- rane to northeastern Laurentia (present coordinates), proximal to the Appalachian- Caledonian orogenic belt. Such a restoration requires signifi cant post-Early Devonian sinistral strike-slip displacement to later incorporate the North Slope subterrane into the composite Arctic Alaska terrane. INTRODUCTION remain particularly enigmatic (e.g., Miller et al., 2006), posing an outstanding barrier to accurate tectonic reconstructions of the The North American Cordillera contains numerous exotic Arctic (Fig. 1A). The Arctic Alaska terrane was once thought to crustal fragments with uncertain origins and displacement his- represent a single contiguous Neoproterozoic−Paleozoic terrane tories that were accreted to autochthonous western Laurentia (e.g., Blodgett et al., 2002; Dumoulin et al., 2002; Miller et al., throughout the late Paleozoic and Mesozoic (Fig. 1A; e.g., Coney 2006), but it has recently been shown to represent a composite of et al., 1980; Silberling et al., 1994; Colpron and Nelson, 2009). In multiple subterranes that likely have distinct pre-Devonian tec- the northernmost Cordillera, the origin and subsequent tectonic tonic histories (Fig. 1B; e.g., Strauss et al., 2013; Amato et al., evolution of Arctic Alaska and Chukotka (northeastern Siberia) 2015; Johnson et al., 2016). Neoproterozoic to early Paleozoic B GREENLAND A 162°W 141°W Beaufort Sea Franklinian basin North Slope beneath NE Brooks (Patchett et al., 1999) 69°N Range PearyaPearya Doonerak Fig. 2 Ba in B Fenster USA 67°N CAN EllesmereE Island n i Arctic Alaskan subterranes g r North Slope Angayucham a m Hammond Cover n Figure 1. Generalized study location maps ia De Long Mountains n 200 km li showing: (A) distribution of paleo-Arctic ter- Endicott Mountains k Chukchi n a ranes and Laurentian basins in the northern Coldfoot Devonian r Study Area Borderland F ChukchiSlate Sea Creek Canadaplutons Cordillera (after Colpron and Nelson, 2011; Basin VictoriaV Johnson et al., 2016), and (B) subterranes of B Island Arctic Alaska (after Strauss et al., 2013). Stars Chukotka indicate study areas. 1 1 Paleo-Arctic realm terranes 1 1 Arctic 1 YYukon block Laurentian off-shelf margin Alaska 1 1 1 Laurentian on-shelf margin Bering Sea 1 1 Selwyn North Slope subterrane basinBasin Farewell Limit of Cordilleran deformation 500 km Alexander Downloaded from https://pubs.geoscienceworld.org/books/chapter-pdf/4554404/spe541-24.pdf by GSA Content on 17 November 2018 Geochemistry of pre-Mississippian sedimentary rocks in the North Slope of Yukon and Alaska 3 strata, faunal assemblages, and detrital zircon data suggest that Early to Middle Ordovician due to the arrival of peri- Laurentian the southwestern portions of the Arctic Alaska terrane (e.g., and exotic island arcs (e.g., Hiscott, 1978; Hurst et al., 1983; Hammond subterrane; Fig. 1B) are exotic to Laurentia (Moore Surlyk and Hurst, 1984; Botsford, 1988; Andersen and Sam- et al., 1997; Dumoulin et al., 2002; Miller et al., 2011; Till et son, 1995; Macdonald et al., 2017). The early Paleozoic tectonic al., 2014a, 2014b; Hoiland et al., 2017; Strauss et al., 2017). In history of the northern margin of Laurentia is less constrained, contrast, the northeastern part of Arctic Alaska, the North Slope but an Ordovician change in provenance from cratonic base- subterrane, has strong ties to Laurentia, based on stratigraphic ment sources to arc-derived juvenile siliciclastic material has relationships and distinctly Laurentian faunas and detrital zircon been documented (e.g., Trettin et al., 1991; Patchett et al., 1999). populations (Strauss et al., 2013, this volume, Chapters 22 and Critically, early Paleozoic arc-derived sediments do not appear 23; McClelland et al., 2015; Lane et al., 2016; Johnson et al., to have reached northwestern Laurentia until the Middle(?) 2016, this volume; Colpron et al., this volume). However, there Devonian–Early Mississippian, when the Ellesmerian clastic remains controversy regarding where along the Laurentian mar- wedge delivered recycled components of juvenile material to the gin the North Slope subterrane originated and when it attained passive margin (Boghossian et al., 1996; Garzione et al., 1997; its current position (e.g., Lane et al., 2016; Johnson et al., 2016). Beranek et al., 2010; Lemieux et al., 2011). In this study, we pres- Some studies maintain that pre-Mississippian strata of the ent new sedimentary geochemical data, specifi cally major and North Slope were deposited in-situ along the Neoproterozoic− trace element analyses coupled with Sm-Nd isotopes, in order to Early Devonian passive margin of the Yukon block of north- characterize the provenance of the pre-Mississippian sedimen- western Laurentia (e.g., Lane, 1991, 1997, 1998; Moore et al., tary succession of the North Slope subterrane and test possible 1994; Cecile et al., 1999; Beranek et al., 2010; Lane and Gehrels, links to northwestern or northeastern Laurentia. 2014; Lane et al., 2016), while others argue for deposition of these strata near the Franklinian basin of northeastern Laurentia GEOLOGICAL SETTING with subsequent translation prior to the opening of the Amerasian basin of the Arctic Ocean (Fig. 1A; e.g., Sweeney, 1982; Oldow North Slope Subterrane et al., 1987; Strauss et al., 2013; Cox et al., 2015; Johnson et al., 2016). Specifi cally, paleogeographic links between the North In the northeastern salient of the Brooks Range, the North Slope subterrane and northeastern Laurentia have been supported Slope subterrane is composed of three distinct sedimentary suc- with biogeographic data and by relating detrital zircon popula- cessions: the pre-Mississippian Franklinian sequence, the Upper tions to sources in the Caledonian orogenic belt (Dumoulin et Devonian−Cretaceous Ellesmerian sequence, and the Jurassic− al., 2000; Strauss et al., 2013, this volume, Chapters 22 and 23; Cenozoic Brookian sequence (Fig. 2A; Lerand, 1973; Moore et Johnson et al., 2016, this volume; Colpron et al., this volume). al., 1994). The Franklinian sequence is characterized by a pen- Owing to the distinct tectonic and sedimentation histories of the etrative fabric that is absent from the younger successions, and it northeastern and northwestern margins of Laurentia during the is locally intruded by Late Devonian plutons (Moore et al., 1994). early Paleozoic, these two competing paleogeographic
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