Research Paper

GEOSPHERE Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia GEOSPHERE; v. 14, no. 1 William Matthews, Bernard Guest, and Lauren Madronich Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada doi:10.1130/GES01544.1

11 figures; 1 table; 1 supplemental file ABSTRACT 1963; Bond and Kominz, 1984; Lickorish and Simony, 1995; Fedo and Cooper, 2001), and are exposed along the length of the Cordillera from Mexico to the CORRESPONDENCE: [email protected] Late Neoproterozoic to Cambrian sandstone units are common in west- Northwest Territories of northern Canada (Stewart et al., 2001; Hadlari et al., ern Laurentia and record initial transgression of the craton after the for- 2012). These strata record the initial transgression of the Laurentian craton CITATION: Matthews, W., Guest, B., and Madronich, mation of the western passive margin during the latest Neoproterozoic to following the onset of thermal subsidence (Bond and Kominz, 1984; Bond et L., 2018, Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia: Geosphere, v. 14, earliest Cambrian. Detrital zircon measurements from 42 latest Neopro- al., 1984, 1985; Levy and Christie-Blick, 1991; Yonkee et al., 2014) and cover an no. 1, p. 243–264, doi:10.1130/GES01544.1. terozoic to Cambrian basal Sauk sequences and five older Neoproterozoic important period in the evolution of complex life (Marshall, 2006). sandstone samples from a region extending from the Mexico–United States The widespread occurrence of sandstone facies suitable for detrital zircon Science Editor: Shanaka de Silva border to central British Columbia, Canada, are combined with previous re- geochronology, and the relatively limited time span of their deposition, make Associate Editor: Christopher J. Spencer sults to characterize sediment source areas and dispersal systems. Detrital them ideally suited for understanding variations in provenance of Lauren- zircon populations in Neoproterozoic and Cambrian sedimentary rocks are tia-derived detritus along the mobile Cordilleran margin. These variations pro- Recieved 13 April 2017 Revison received 28 July 2017 divided into six facies based on a statistical comparison using multidimen- vide useful constraints on the paleogeographic position of displaced crustal Accepted 20 November 2017 sional scaling. Detrital zircon facies are found in unique geographical regions fragments in the Cordillera and contribute to a fuller understanding of large- Published online 20 December 2017 reflecting proximity to the major tectonic provinces of Laurentia. Samples scale early Paleozoic sediment dispersal patterns in Laurentia. from northern regions are dominated by Archean and Paleoproterozoic zir- Previous studies of Neoproterozoic to Cambrian deposits in western cons derived from Archean tectonic provinces and the orogenic belts that Laurentia have been sub-regional in extent (e.g., Stewart et al., 2001; Am- record the assembly of the Laurentian craton. More southerly sample loca- ato and Mack, 2012) or incorporated only a small number of widely spaced tions show an increase in detrital zircons derived from younger Paleopro- samples (Gehrels et al., 1995; Gehrels and Pecha, 2014). These studies reveal terozoic orogenic belts and early Mesoproterozoic intrusive suites. Detrital that latest Neoproterozoic to Cambrian rocks exhibit significant geographic zircons from Grenville-aged sources are common in the south. The Transcon- variation in detrital zircon populations, reflecting proximity to the major tec- tinental Arch, a feature interpreted to have controlled large-scale sediment tonic provinces of Laurentia. However, the wide sample spacing in previous dispersal patterns in the mid- to late Cambrian, likely played a major role in studies and a lack of samples along the Canadian segment of the Cordillera isolating the southern and northern signatures. Our data set can be used to and from the thin cratonal successions exposed in Laramide structures to the test tectonic models for the Cordilleran orogen that invoke Jurassic or Cre- east has limited the usefulness of these variations in continent-scale paleo- taceous collision of a ribbon continent as the driving mechanism for orogen- geographic reconstructions. esis. Cambrian rocks of the Cassiar-Antler platform juxtaposed with North Here we report new detrital zircon results from Neoproterozoic and Cam- OLD 6 2 G America during the hypothetical ribbon continent collision show the same brian sandstones in a ~1 × 10 km region extending from the southern United geographic distribution of detrital zircon facies as similar-aged rocks from States to central British Columbia, Canada (Fig. 1). These data are integrated autochthonous and parautochthonous locations on the Laurentian margin. with previous studies to investigate large-scale provenance patterns in west- The concordance of detrital zircon facies across the proposed suture is a ern Laurentia during the Cambrian. These results provide a baseline with OPEN ACCESS negative result for models that predict large dextral displacements, on the which to compare Laurentia-derived detrital zircon populations in displaced order of 2000 km, across the suture. terranes. As a first application of this new data set, we evaluate tectonic mod- els for the Cordillera that involve the Cretaceous collision of composite ribbon continents as the driving force for Cretaceous orogenesis (SAYBIA of Johnston INTRODUCTION [2008], and Rubia of Hildebrand [2009]). To do this, we compare detrital zircon populations of samples from autochthonous and parautochthonous loca- This paper is published under the terms of the Laterally persistent latest Neoproterozoic to Cambrian sandstone units tions known to be deposited on the western margin of Laurentia with those CC‑BY-NC license. mark the base of the western Laurentian passive margin succession (Sloss, interpreted by some to have been deposited on the ribbon continent.

© 2017 The Authors

GEOSPHERE | Volume 14 | Number 1 Matthews et al. | Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia 243 Research Paper

SAMPLED UNITS

Neoproterozoic to Cambrian strata are common along the western mar- gin of Laurentia, and include latest Neoproterozoic to Cambrian sandstones that form the base of the Sauk sequence (Sloss, 1963). These sandstones are referred to as basal Sauk sandstones in this paper. Forty-two samples of basal Sauk sandstones were collected at 26 locations (Figs. 1 and 2). See Table 1 for details of the sampled units, ages, and locations. Detailed descriptions of the sampled formations and locations are included in the Supplemental Informa- tion1. The western units, which are latest Neoproterozoic to middle Cambrian in age and were deposited on Mesoproterozoic to Neoproterozoic sedimentary successions, were sampled from allochthonous thrust sheets within the Rocky Mountains and Sevier fold-and-thrust belts or from structures associated with Basin and Range extension. To the east, basal Sauk sandstones, which are middle to late Cambrian in age and rest unconformably above ca. 1.1 Ga to ca. 2.7 Ga crystalline rocks of the Laurentian craton, were collected from autoch- thonous to parautochthonous units involved in Laramide, Rocky Mountains, and Sevier deformation. These new data were integrated with published data from 36 basal Sauk sandstones (Table 1). For consistency with the ribbon continent models for the Cordillera be- ing tested here, basal Sauk sequence sandstones are divided into two major groups. Western samples deposited on thick Mesoproterozoic and Neopro- terozoic sedimentary successions are part of the Cassiar (Canada and northern United States) or Antler platforms (United States). Eastern samples deposited Supplemental Information: Latest Neoproterozoic to Cambrian on thin Neoproterozoic deposits or directly on crystalline rocks of Laurentia detrital zircon facies of Western Laurentia are part of the North American platform. Classifications for each sample are William Matthews, Bernard Guest, and Lauren Madronich given in Table 1, and the significance of the platform interpretation is dis- Supplementary Methods for Dang of Crystalline Rocks

Samples were collected and zircon separated by the methods outlined in the methods secon of the cussed below. To facilitate provenance interpretations, five sandstone samples main paper. Unlike the detrital samples, zircon from crystalline rocks were hand-picked to be free of inclusions, inherited cores and fractures. Up to 25 grains were arranged on double-sided tape and cast in were collected from older Neoproterozoic formations that underlie basal Sauk epoxy. Mounts were finished and data acquired using the same methods described for the detrital samples. Ages presented below are 206Pb/238U for ages <1500 Ma and 207Pb/206Pb for ages >1500 sequence sandstones in some of the western locations. These samples were Ma. Uncertaines are quoted at 2σ and include all sources of uncertainty propagated as per Horstwood et al. (2017). collected to ascertain the importance of local recycling of detrital zircon popu- Sample Locaon Details for Samples Collected in this Study lations from older sedimentary successions during Sauk transgression. Sam- Sample 1: Yanks Peak near McBride, Brish Columbia (046-WMBC)

The Yanks Peak exposed in a mine site adjacent to the Yellowhead Highway near the juncon with the ple locations for older Neoproterozoic samples are given in Table 1 and their Figure 1. Locations for Cambrian samples from this study (yellow outlines, red text) and previ- Walker Creek service road. The Yanks Peak is fine-grained, planar to trough cross-laminated, purple- ously published work (black outlines), western North America. Outlines of areas affected by Se- yellow weathering and bedded at the decimeter scale with interbeds of phyllite. Fresh surfaces are relationship to the overlying basal Sauk sequence sandstones are outlined in creamy or purplish grey. Quartz filled veins are common and abundant pyrite and other sulphides vier–Rocky Mountain and Laramide deformation and the Basin and Range province are shown. disseminated throughout the rocks and within veins. The sample is from the south side of the quarry. the Supplemental Information. Symbol shapes and colors indicate sampled formations. Province and state abbreviations: AB— Sample 2, 3: Upper part of McNaughton Formaon, lower part of McNaughton Formaon, Cinnamon Alberta; AZ—Arizona; BC—British Columbia; CA—California; CO—Colorado; ID—Idaho; MT— Ridge (Mt. Robson), Brish Columbia (056-WMBC, 057-WMBC)

The McNaughton Formaon is exposed on the steeply dipping to overturned west limb of Mt. Robson Montana; NM—New Mexico; NV—Nevada; SO—Sonora; UT—Utah; WY—Wyoming. syncline along the flanks of Cinnamon Ridge. At this locaon the McNaughton overlies argillite and mudstone of the Miee Formaon and is overlain by carbonates of the Mural Formaon. Sample 056 is METHODS a well bedded sandstone from the upper part of the McNaughton. Sample 057 is a medium-grained well bedded sandstone from the lower McNaughton.

Sample 4, 5: Gog Group (undifferenated), north of Whirlpool Point, Alberta (043-WMAB, 044-WMAB) Zircon was extracted by the standard mineral separation procedures of finish on the final mount. This preparation procedure ensures consistent laser crushing, water table, heavy liquids, and magnetic separation. A representa- focus between grains. tive fraction of the zircon-rich separate was then dump-mounted into a round Isotopic data were acquired on an Agilent 7700 quadrupole inductively cou- 1Supplemental Information. Detailed descriptions of the sampled formations and locations; and all la- 25.4 mm plastic form and cast in epoxy. To avoid biasing the detrital zircon pled plasma–mass spectrometer (ICP-MS) coupled to a Resonetics RESOchron ser settings, dwell times for each measured mass, populations, no selection of zircons by physical characteristics was undertaken. 193 nm excimer laser ablation system. Ablation occurred within a Laurin Tech- gas flow rates, and ICP-MS settings. Please visit Mounts were ground using 5 and 3 µm silicon carbide abrasive films and nic M-50 dual volume ablation cell. For details of the ablation cell performance http://doi​ .org​ /10​ ​.1130/GES01544​ ​.S1 or the full-text article on www.gsapubs.org to view the Supple- then polished using 1 µm diamond film. Grinding and polishing were done and the laser ablation system, see Müller et al. (2009). All laser settings, dwell mental Information. by hand using low-pile polyester films mounted on glass to ensure a very flat times for each measured mass, gas flow rates, and ICP-MS settings can be

GEOSPHERE | Volume 14 | Number 1 Matthews et al. | Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia 244 Research Paper

Figure 2. Stratigraphic charts for select sample locations. Sam- pled basal Sauk sequence units are highlighted in yellow; older Neoproterozoic units sampled in this study are highlighted in orange. Black thrust symbol within the stratigraphic sections indicates that the section is carried in a thrust sheet. Bold red thrust symbol marks the approximate location of the bound- ary between samples from the Cassiar-Antler platform (west) and North American platform (east); see text for discussion. References are given in Roman numerals and are listed in the Supplemental Information (footnote 1). Sample numbers, for- mations, and province and state abbreviations for symbols are the same as in Figure 1.

GEOSPHERE | Volume 14 | Number 1 Matthews et al. | Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia 245 Research Paper

TABLE 1. DETAILS OF DETRITAL ZIRCON SAMPLE LOCATIONS AND FORMATIONS, WESTERN NORTH AMERICA Sample Latitude Longitude number Sample ID Formation Location ReferenceAge n Platform (°N) (°W) Latest Neoproterozoic to Cambrian (basal Sauk sequence) samples 1 046-WMBC Yanks Peak McBride, BC This study Early Cambrian 108Cassiar 53.66523 120.91633 2 056-WMBC McNaughton Cinnamon Ridge, BC This study Early Cambrian 97 Cassiar 53.06713 119.18772 3 057-WMBC McNaughton Cinnamon Ridge, BC This study Early Cambrian 76 Cassiar 53.05859 119.20824 4 043-WMAB GogWhirlpool Point, AB This study Early Cambrian 118North American 52.01875 116.46310 5 044-WMAB GogWhirlpool Point, AB This study Early Cambrian 105North American 52.01716 116.46548 6 045-WMAB Fort Mountain Cirque Lake,ABThis study Early Cambrian 113North American 51.81518 116.64120 7 042-WMAB Jasper Cirque Lake,ABThis study Latest Neoproterozoic 85 North American 51.81437 116.64161 8 041-WMAB Jasper Cirque Lake,ABThis study Latest Neoproterozoic 105North American 51.81389 116.63727 9 049-WMBC Hamill lower quartziteDogtooth Ranges, BC This study Latest Neoproterozoic 93 Cassiar 51.42162 117.25327 10 051-WMBC Hamill middle Dogtooth Ranges, BC This study Latest Neoproterozoic 95 Cassiar 51.41929 117.25577 11 050-WMBC Hamill upper quartziteDogtooth Ranges, BC This study Early Cambrian 120Cassiar 51.41830 117.25696 12 040-WMAB GogHelena Ridge, AB This study Early Cambrian 89 North American 51.29818 115.89925 13 Hamill; SBC Hamill Purcell Mountains, BC Gehrels and Pecha, 2014Early Cambrian 130Cassiar 50.47222 116.92500 14 061-WMBC Hamill upper Blockhead Mountain, BC This study Early Cambrian 89 Cassiar 50.32346 116.60627 15 062-WMBC Hamill middle Blockhead Mountain, BC This study Latest Neoproterozoic 82 Cassiar 50.32235 116.60182 16 060-WMBC Hamill lowerBlockhead Mountain, BC This study Latest Neoproterozoic 82 Cassiar 50.31949 116.59492 17 059-WMBC Hamill lowerBlockhead Mountain, BC This study Latest Neoproterozoic 79 Cassiar 50.31878 116.58719 18 052-WMAB Flathead Windsor Mountain, AB This study Middle Cambrian (?)85North American(?)49.30644 114.23995 19 055-WMBC Quartzite Range Kootenay Pass, BC This study Early Cambrian 90 Cassiar 49.06382 117.06351 20 053-WMBC Three SistersKootenay Pass, BC This study Latest Neoproterozoic 88 Cassiar 49.06382 117.06351 21 054-WMBC Three SistersKootenay Pass, BC This study Latest Neoproterozoic 98 Cassiar 49.06382 117.06351 22 LakeviewGold Creek Lakeview Turnoff, ID Lewis et al., 2010Cambrian82North American(?)47.97650 116.42100 23 001-WMMT Flathead Little Belt Mountains, MT This study Middle Cambrian (?)101 North American 46.87713 110.67869 24 039-WMMT Flathead Big Belt Mountains, MT This study Middle Cambrian (?)96Cassiar 46.71205 111.77454 25 006-WMWYFlathead Cody, WY This study Middle Cambrian (?)109 North American 44.50928 109.17177 26 FH0108 Flathead, upper Cody, WY May et al., 2013 Middle Cambrian (?)38North American 44.50900 109.17100 27 FH01-10 Flathead, lowerCody, WY May et al., 2013 Middle Cambrian (?)63North American 44.50900 109.17200 28 009-WMWYFlathead Rattlesnake Hills, WY This study Middle Cambrian (?)91North American 42.83940 107.38141 29 09JK08 Gibbson Jack Pocatello, ID Yo nkee et al., 2014 Early Cambrian 73 Antler42.80106 112.25502 30 05Z08 Camelback Mountain Pocatello, ID Yo nkee et al., 2014 Early Cambrian 74 Antler41.98094 111.71825 31 038-WMUT Geertsen Canyon High Creek, UT This study Early Cambrian 85 Antler41.97708 111.72058 32 Osgood; NV Osgood Mountain North of Osgood Mountain, NV Gehrels and Pecha, 2014Early Cambrian or late 186Antler41.97333 117.43500 Neoproterozoic 33 011-WMWY Flathead Rawlins, WY This study Middle Cambrian (?)100 North American 41.79334 107.26045 34 010-WMWYFlathead Rawlins, WY This study Middle Cambrian (?)96North American 41.79281 107.26136 35 66CD10Geertsen Canyon Huntsville, UT Yo nkee et al., 2014 Early Cambrian 69 Antler41.33188 111.69032 36 20AY11Geertsen Canyon Huntsville, UT Yo nkee et al., 2014 Early Cambrian 88 Antler41.27356 111.66310 37 Geerston; UT Geertsen Canyon Huntsville, UT Gehrels and Pecha, 2014Early Cambrian 183Antler41.26500 111.67833 38 17AY11Tintic Ogden Canyon, UT Yo nkee et al., 2014 Early Cambrian 83 North American 41.23830 111.91243 39 035-WMUT Tintic Ogden Canyon, UT This study Early Cambrian 109North American 41.23806 111.91428 40 GC-03-COM Osgood Mountain Osgood Mountain, NV Linde et al., 2014 Latest Neoproterozoic 75 Antler41.14041 117.36997 41 SP-01-COM Osgood Mountain Osgood Mountain, NV Linde et al., 2014 Latest Neoproterozoic 84 Antler41.08272 117.43157 42 GOL-01_COM Osgood Mountain Osgood Mountain, NV Linde et al., 2014 Early Cambrian 80 Antler40.93638 117.44720 43 20CD10Tintic Provo, UT Yo nkee et al., 2014 Early Cambrian 85 North American 40.22621 111.61707 44 J8709I Prospect Mountain Deep Creek Yo nkee et al., 2014 Early Cambrian 52 Antler39.63316 108.03864 45 014-WMCO Sawatch Hanging Lake, CO This study Middle–late Cambrian 133North American 39.59551 107.18396 46 013-WMCO Sawatch Hanging Lake, CO This study Middle–late Cambrian 105North American 39.59550 107.18381 47 034-WMUT Tintic Pavant thrust, UT This study Early Cambrian 105Antler38.92960 112.22259 48 018-WMCO Sawatch Manitou Springs, CO This study Middle–late Cambrian 95 North American 38.86979 104.92523 49 017-WMCO Sawatch Manitou Springs, CO This study Middle–late Cambrian 133North American 38.86889 104.92553 (continued)

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TABLE 1. DETAILS OF DETRITAL ZIRCON SAMPLE LOCATIONS AND FORMATIONS, WESTERN NORTH AMERICA (continued) Sample Latitude Longitude number Sample ID Formation Location ReferenceAge n Platform (°N) (°W) Latest Neoproterozoic to Cambrian (basal Sauk sequence) samples 50 033-WMUT Prospect Mountain San Francisco Mountains, UT This study Early Cambrian 113 Antler 38.81746 113.02569 51 34CD10Prospect Mountain San Francisco Mountains, UT Yonkee et al., 2014 Early Cambrian 84 Antler 38.77122 113.02155 52 032-WMUT Prospect Mountain San Francisco Mountains, UT This study Early Cambrian 94 Antler 38.70032 113.11366 53 35CD10Prospect Mountain San Francisco Mountains, UT Yonkee et al., 2014 Early Cambrian 74 Antler 38.69937 113.12048 54 85NVCL-3B Wood Canyon Caliente, NV Howard et al., 2015 Early Cambrian 91 Antler 37.86313 114.65166 55 020-WMCO Ignacio Durango, CO This study Late Cambrian– 109 North American 37.65320 107.80457 Ordovician 56 83WMAM-4CampitoWhite Mountains, CA Howard et al., 2015 Early Cambrian 56 Antler 37.62644 118.30722 57 027-WMNV Wood Canyon Spring Mountains, NV This study Early Cambrian 110 Antler 36.33990 115.90942 58 026-WMNV Wood Canyon Spring Mountains, NV This study Early Cambrian 109 Antler 36.33882 115.90216 59 029-WMNV Tapeats Frenchman Mountains, NV This study Early Cambrian (?) 105 North American 36.19790 115.00861 60 Tap2; AZ Tapeats Grand Canyon, AZ Gehrels et al., 2011 Early Cambrian 105 North American 36.19388 111.79877 61 Tap; AZ Tapeats Grand Canyon, AZ Gehrels et al., 2011 Early Cambrian 84 North American 36.08863 112.11747 62 WC; CA Wood Canyon CA Gehrels and Pecha, 2014 Early Cambrian 191 Antler 35.77500 115.72833 63 025-WMCAWood Canyon Marble Mountains, CA This study Early Cambrian 132 North American 34.53678 115.48240 64 WC2: CA Wood Canyon San Bernardino Mountains, CA Gehrels and Pecha, 2014 Early Cambrian 175 Antler 34.31150 116.83667 65 023-WMAZ Tapeats East Verde River, AZ This study Early Cambrian (?) 106 North American 34.30099 111.35810 66 09MS1 Bliss Mud Springs, NM Amato and Mack, 2012 Late Cambrian 59 North American 33.15067 107.30360 67 06SA-10 Bliss San Andres Mountains, NM Amato and Mack, 2012 Late Cambrian 71 North American 32.84989 106.57985 68 09SL2 Bliss San Lorenzo, NM Amato and Mack, 2012 Late Cambrian 78 North American 32.80189 107.94833 69 09SL1 Bliss San Lorenzo, NM Amato and Mack, 2012 Late Cambrian 52 North American 32.80149 107.94791 70 022-WMNM Bliss Silver City, NM This study Late Cambrian 92 North American 32.79763 108.33943 71 04SASC2 Bliss San Andres Mountains, NM Amato and Mack, 2012 Late Cambrian 84 North American 32.62664 106.52881 72 04SASC6 Bliss San Andres Mountains, NM Amato and Mack, 2012 Late Cambrian 98 North American 32.62664 106.52881 73 07SD3aBliss San Diego Mountains, NM Amato and Mack, 2012 Late Cambrian 60 North American 32.59870 106.97160 74 07SD3cBliss San Diego Mountains, NM Amato and Mack, 2012 Late Cambrian 83 North American 32.59870 106.97160 75 10BM215 Bliss Burro Mountains, NM Amato and Mack, 2012 Late Cambrian 51 North American 32.44915 108.25591 76 10BM216 Bliss Burro Mountains, NM Amato and Mack, 2012 Late Cambrian 72 North American 32.44770 108.25759 77 11LHM03Bliss Little Hatchet Mountains, NM Amato and Mack, 2012 Late Cambrian 54 North American 32.14667 107.65306 78 Prov; SO ProveedoraSonora, MX Gehrels and Pecha, 2014 Middle Cambrian 114 Unknown 29.20000 109.91333 Neoproterozoic samples N1 048-WMBC Horsethief Creek Dogtooth Ranges, BC This study Neoproterozoic95Cassiar 51.42294 117.24850 N2 HTC; SBC Horsethief Creek Purcell Mountains, BC Gehrels and Pecha, 2014 Neoproterozoic 153 Cassiar 50.59306 116.73333 N3 058-WMBC Horsethief Creek Blockhead Mountain, BC This study Neoproterozoic95Cassiar 50.32255 116.58048 N4 04Z08 Mutual Pocatello, ID Yonkee et al., 2014 Neoproterozoic80Cassiar 41.97965 111.71942 N5 03Z08 Mutual Pocatello, ID Yonkee et al., 2014 Neoproterozoic85Cassiar 41.97997 111.72085 N6 037-WMUT Mutual High Creek, UT This study Neoproterozoic 110 Cassiar 41.97727 111.73662 N7 Mutual; NV Mutual Huntsville, UT Gehrels and Pecha, 2014 Neoproterozoic 203 Cassiar 41.26580 111.68167 N8 59CD10Mutual Huntsville, UT Yonkee et al., 2014 Neoproterozoic65Cassiar 41.33005 111.69249 N9 031-WMUT Mutual San Francisco Mountains, UT This study Neoproterozoic 105 Cassiar 38.69550 113.12093 N10 36CD10Mutual San Francisco Mountains, UT Yonkee et al., 2014 Neoproterozoic56Cassiar 38.69627 113.12033 N11 028-WMNV Stirling Spring Mountains, NV This study Neoproterozoic 113 Cassiar 36.33941 115.91938 N12 NR9 Stirling Nopah Range, CA Schoenborn et al., 2012 Neoproterozoic62Cassiar 36.03697 116.08130 Note: Platform refers to the sampled unit belonging to either the North American or Cassiar-Antler Platform (see text for discussion).Province, state and country abbreviations: AB—Alberta; AZ—Arizona; BC— British Columbia; CA—California; CO—Colorado; ID—Idaho; MT—Montana; MX – Mexico; NM—New Mexico; NV—Nevada; SO—Sonora; UT—Utah; WY—Wyoming.

GEOSPHERE | Volume 14 | Number 1 Matthews et al. | Latest Neoproterozoic to Cambrian detrital zircon facies of western Laurentia 247 Research Paper

found in the Supplemental Information (footnote 1). A laser energy of 1.5 J/cm2 quadrature to data-point uncertainties. Average uncertainty (2σ), including all and beam diameters of 30 µm and 40 µm were employed. random and systematic components, increased from ~2% for measurements The measurement method employed a sample-bracketing strategy with yielding Archean dates to ~3% for measurements yielding Cambrian dates. measurements of the calibration reference material, Temora 2 (Black et al., Results of measurement of the five validation reference materials vali- 2004), run every 10 unknowns, or roughly every 10 min. Temora 2 is relatively date the measurement method. The mean absolute offset and mean offset of young (417 Ma), and as such, contains little 207Pb. Low 207Pb beam intensity can 206Pb/238U ages determined by laser ablation–ICP-MS (LA-ICP-MS) in this study lead to greater uncertainty in correction for instrumental mass fractionation of and their accepted isotope dilution–thermal ionization mass spectrometry (ID- lead isotopes due to the low precision of the measured 207Pb/206Pb ratio of the TIMS) ages is 0.6% and -0.05%, respectively. The mean 206Pb/238U ages for all calibration reference. To avoid this, two sequential ablations of the calibration validation reference materials fall within 0.8% of their accepted age. The offset reference were employed between each set of 10 unknowns. Three validation of the 207Pb/206Pb age of validation reference materials FC1 (Paces and Miller, reference materials with ages between 1065.4 Ma and 2679.8 Ma were mea- 1993) and 1242 is -0.2% and 0.1%, respectively. sured in each measurement session to validate the results and to assess ran- Numerous authors have noted that 206Pb/238U dates yield, on average, lower dom and systematic uncertainties. Each measurement began with a 15 s gas uncertainties for younger dates, whereas 207Pb/206Pb dates yield lower uncer- blank acquired with the laser off. This was followed by a 30 s ablation and a tainties for older dates (Gehrels et al., 2008; Spencer et al., 2016; Matthews and 5 s delay to record washout back to background. For each sample, 120–140 Guest, 2016). Spencer et al. (2016) noted that for a large number of measure- unknowns were measured. ments, the optimum cutoff between the 206Pb/238U and 207Pb/206Pb isotopic sys- Data reduction was handled in the commercially available Iolite software tem was 1500 Ma, and we adopt that cutoff here. Dates used for plotting and in package (version 2.5) (Paton et al., 2010) and a custom Microsoft Excel Visual the discussion are 206Pb/238U for dates <1500 Ma, and 207Pb/206Pb for dates >1500 Basic for Applications (VBA) macro (ARS4.0; operation of macro outlined in Ma. Dates were filtered for outliers using the probability of concordance calcu- Matthews and Guest, 2016). Background subtraction and correction of raw lated by the concordia age function in Isoplot software (version 4.15) (Ludwig, isotopic ratios for laser-induced elemental fractionation, instrumental mass 1998, 2012). Measurements with <1% probability of concordance were elim- fractionation, and drift in the sensitivity of the ICP-MS was performed in Io- inated from the data set. Final data are presented as normalized probability lite. Final isotopic ratios and their associated standard deviations of the mean density functions calculated using a VBA macro. and error correlations were exported from Iolite to Excel where the final un- Multidimensional scaling (MDS) is used to aid in visualizing the statisti- certainty propagation was performed and ages were calculated. No common cal differences between the large number of samples included in this study lead correction was attempted. Instead, interrogation of the time-resolved 204Pb and to more objectively group samples exhibiting similar detrital zircon pop- signal intensity and calculated 207Pb/206Pb ages was used to eliminate measure- ulations into facies (see discussion below; Vermeesch, 2013; Spencer and ments, or portions of measurements, contaminated by common lead as per Kirkland, 2016). In this study, the maximum difference between the cumu- the procedure outlined by Matthews and Guest (2016). lative probability density functions for each pair of samples—the D statistic Uncertainty propagation was aligned with the community-derived best of the Kolmogorov-Smirnov test—is used to quantify the dissimilarity of the practices reported in Horstwood et al. (2016). Standard deviation of the mean samples. The D statistic is measured between each pair of samples to cre- was calculated as the standard deviation of all isotopic ratios for an analysis di- ate a matrix of dissimilarity. The MDS approach then plots the samples on a vided by the square root of the number of mass sweeps. Random uncertainties Euclidean plane while attempting to honor the differences between samples for the isotopic ratios for each datum were calculated using the suite of vali- in the dissimilarity matrix. As such, the distance between samples in the MDS dation reference materials. Excess variance in the 206Pb/238U ratio of validation plot is roughly equal to the dissimilarity between the samples based on the D reference material 91500 (Wiedenbeck et al., 1995) was added in quadrature to statistic, and samples containing similar detrital zircon populations will plot in each datum. Excess variance in 207Pb/206Pb ratios was calculated for each datum the same region. based on 207Pb beam intensity and a session-specific calibration curve between The addition of normally distributed unimodal synthetic populations has 207Pb beam intensity and excess variance in the validation reference materials, been shown to aid in visualizing the differences between samples on an MDS as per the methods described by Matthews and Guest (2016). plot (Spencer and Kirkland, 2016). Here, five synthetic populations with ages Systematic uncertainties were added to data-point uncertainties and to drawn from the major populations found in Cambrian rocks of western Lau- weighted averages as follows. Long-term excess variance in the 206Pb/238U and rentia (2700, 1780, 1650, 1430, and 1100 Ma) were plotted with the Cambrian 207Pb/206Pb ratios was determined by comparing these ratios for all measure- and Neoproterozoic samples on a single non-metric MDS “map” using the ments of reference materials 91500 and 1242 (Mortensen and Card, 1993) from IsoplotR software from Vermeesch (2013). all analytical sessions in this study (33 sessions over 1 yr). Long-term excess The grouping of samples into detrital zircon facies assumes that the relative variance in both ratios was ~1%. Long-term excess variance, ratio uncertainty proportions of detrital zircon populations measured in a sample are represen- in the primary reference, and uncertainty in the decay constant were added in tative of the parent rock. Pullen et al. (2014) demonstrated that low-n (where n

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Figure 3. Probability density function for all new Neoproterozoic and Cambrian samples reported here. Dates are 206Pb/238U for dates <1500 Ma, and 207Pb/206Pb for dates >1500 Ma. Samples with <1% probability of concordance were filtered from the data set. N is the number of samples; n is the num- ber of measurements. Colored regions correspond to major crystalline provenances of the Laurentian craton; the age of important modes is given (in Ma).

is the number of single-grain measurements conducted per sample) subsets tion incorporating all of the new samples reveals five major populations of de- of a large detrital zircon data set poorly reproduce the relative proportions of trital zircon: (1) Archean to early Neoproterozoic (3.5–2.4 Ga; mode 2.7 Ga); (2) components of the zircon population. To reduce the likelihood of drawing spu- Paleoproterozoic (2.0–1.6 Ga; mode 1.8 Ga); (3) early Mesoproterozoic (1.5–1.3 rious correlations between samples, we limit our comparison to data sets with Ga; mode 1.4 Ga); (4) late Mesoproterozoic (1.3–1.0 Ga; modes 1.2 and 1.1 Ga); an average of 100 measurements per sample. While this strategy precludes and (5) Neoproterozoic to Cambrian (0.8–0.5 Ga; various modes between 0.8 the integration of some commonly cited detrital zircon data sets (e.g., Stewart and 0.5 Ga) (Fig. 3). Important geographical variations in the presence, ab- et al., 2001; average 22 measurements per sample), it minimizes the effect of sence, and relative proportions of these five major populations are discussed sampling variability on our analysis. below and used to understand Cambrian provenance patterns and to test tec- In this study, we combine our new data with previously published data tonic models for the Cordillera. for Cambrian and Neoproterozoic samples (Table 1). All previously measured samples were acquired by LA-ICP-MS. Results from previous work are reported here using the same concordance filtering criteria applied to our new data and CRYSTALLINE PROVENANCE OF DETRITAL ZIRCON the same 1500 Ma cutoff between 206Pb/238U and 207Pb/206Pb dates. The level of reported uncertainties varies between the different data sets The physical and chemical durability of zircon enables it to survive multiple integrated in this study. In some cases, only random uncertainties associated weathering, transport, deposition, and burial cycles. As such, provenance in- with the standard deviation of the mean for the individual data points were terpretations must consider derivation from not only the crystalline rocks from reported (“analytical uncertainties”). In other studies, random and systematic which the zircons ultimately derive, but also potential recycling from older sed- components of uncertainty were reported, although it was not always clear imentary successions (Dickinson et al., 2009; Hadlari et al., 2015). what systematic components were included. We used all the reported compo- The vast majority of detrital zircon in basal Sauk sequence sandstones nents of uncertainty, random and systematic, to plot these data in our figures. ultimately derive from crystalline sources within the Laurentian craton (Fig. 3). A broad distribution of Archean to Paleoproterozoic (>2.4 Ga) dates are consistent with ultimate sources in cratonic cores that form the oldest rocks RESULTS of the Laurentian craton (Hoffman, 1988). The broad high in the probability density function in the late Paleoproterozoic (mode 1.78 Ga), which includes Uranium-lead measurements of detrital zircons from basal Sauk and older grains between 2.0 and 1.6 Ga, derive from a collage of Proterozoic orogenic Neoproterozoic sandstones yielded 4743 dates that passed our concordance provinces and their associated accreted terranes that record the assembly of filter. Complete isotopic data for measurements reported here can be found in the Laurentian craton. Zircon grains yielding dates between 2.4 Ga and 1.8 Ga the Supplemental Information (footnote 1). A single probability density func- derive from Proterozoic orogenic belts and the associated accreted terranes

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Figure 4. Nonmetric multidimensional scaling plot of the detrital zircon age spectra of select Cambrian samples from southwestern Laurentia and of five unimodal synthetic populations. Plot is based on the D statistic of the Kolmogorov-Smirnov test, and this is the value of the axes; see text for discussion. Samples that plot close to one another contain similar detrital zircon populations. Detrital zircon data are divided into six facies (A, B, C, D, E, F) based on this plot, geological information, and visual inspection of the samples’ probability density functions. Samples from this study are shown with red text. Dashed black line indicates the boundary between samples that contain >3% Archean grains and those that contain <3% Archean grains. Dashed grey line indicates the boundary between samples that exhibit A1 and A2 detrital zircon facies. White squares containing letters in the MDS map are used to identify the following samples: Y—Yanks Peak; Q—Quartzite Range; T—Three Sisters; G—Gold Creek. Black arrow at sample 59 indicates its reassignment to facies E; see text for discussion. See Figure 1 for province and state abbreviations appearing in the symbol explanation.

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et al., 2005), “signatures” (e.g., Hadlari et al., 2012; Benyon et al., 2014), “types” (e.g., Dumitru et al., 2015, 2016), or “facies” (e.g., LaMaskin, 2012). Here we refer to these patterns as detrital zircon facies, as we feel this termi- nology is a natural complement to the concept of depositional facies used by sedimentologists. To provide a framework for the discussion of provenance patterns in western Laurentia, samples are divided into detrital zircon facies based on similarities in the age and relative proportions of their major zircon popu- lations. Rather than relying solely on the visual comparison of detrital zir- con populations, a statistical approach involving MDS was employed. All 42 Cambrian and five Neoproterozoic samples reported here were combined with previously published results from 36 Cambrian and seven Neoprotero- zoic samples to create a single MDS plot (Figs. 4 and 5). Probability density functions for all samples, grouped according to the MDS plot, are provided (Figs. 6 and 7). Detrital zircon populations were divided into six detrital zircon facies based mainly on groupings of the samples in the MDS plot, but also incor- porating the known geographic distribution of the samples and formations studied (Fig. 4). Visual inspection of probability density functions was used Figure 5. Nonmetric multidimensional scaling plot of the detrital zircon age spectra of select in some cases to draw boundaries between samples with subtle but signifi- Neoproterozoic samples from southwestern Laurentia. Samples from this study are shown with cant differences in their detrital zircon population (e.g., samples 38 and 15). red text. See Figure 4 for a complete description of how the detrital zircon facies were defined. See Figure 1 for province and state abbreviations appearing in the symbol explanation. Facies A was divided into two subfacies, A1 and A2, based on the presence of Mesoproterozoic, Neoproterozoic, and Cambrian zircon populations in the latter. Removing these components from facies A2 samples would result in that stitch together the Archean cratonic cores. Grains yielding dates between A1 signatures. 1.8 Ga to 1.68 Ga may derive from the Yavapai province of southern Laurentia Detrital zircon facies are not restricted to single formations, with each or post-orogenic magmatic bodies (e.g., the Swift Current anorogenic prov- facies found in samples from at least three to as many as six formations. In ince). Grains yielding dates between 1.7 Ga and 1.6 Ga may derive from the general, detrital zircon facies correspond to discrete geographical regions of Mazatzal province immediately south of the Yavapai. A prominent Mesopro- western Laurentia, with some overlap. Samples containing Archean grains terozoic mode at 1.43 Ga indicates derivation from extensive A-type plutons plot on the left of the MDS map nearer the 2700 Ma synthetic population; a that intrude the Yavapai and Mazatzal provinces throughout southern and dashed line demarcating the boundary between samples that contain greater southeastern Laurentia (Anderson and Bender, 1989). Zircon grains yielding than and less than 3% Archean detritus is provided as a reference (Fig. 4). dates between 1.3 Ga and 1.0 Ga ultimately derive from the Grenville province, Samples with increasing proportions of Grenville detritus plot toward the which records the final assembly of the supercontinent Rodinia and is found bottom right of the map near the 1100 Ma synthetic population. Samples that in Texas (southern United States) and along the southeastern margin of Lau- plot in the top right of the map contain variable mixtures of late Paleoprotero- rentia. Neoproterozoic and early Cambrian detrital zircons derive from mag- zoic and Mesoproterozoic grains as evidenced by their proximity to the 1650 matism associated with crustal thinning during deposition of the Windermere Ma and 1430 Ma synthetic populations. Samples that plot in the top left of the Supergroup and the formation of the western Laurentian passive margin in the map contain prominent Paleoproterozoic populations and cluster near the latest Neoproterozoic to Cambrian. 1780 Ma synthetic population. Samples that plot in the middle of the diagram represent mixtures of these five major components. Detrital zircon facies A1 and A2 are found in formations in the central and IDENTIFICATION OF DETRITAL ZIRCON FACIES northern portions of the study area, including the Yanks Peak, McNaughton, Gog, Hamill, Quartzite Range, Three Sisters, Gold Creek, Flathead, Geertsen Large bodies of genetically related rock commonly exhibit reproducible Canyon, and Horsethief Creek formations (Fig. 8). A1 and A2 detrital zircon detrital zircon distributions due to similarities in the rock’s source regions facies are characterized by Archean to early Paleoproterozoic (3.0–2.4 Ga) and mixing and homogenization of sediments in the depositional system. populations and a dominant late Paleoproterozoic population between 1.9 These reproducible patterns have been referred to as “barcodes” (e.g., Link and 1.7 Ga, with a mode of ca. 1.8 Ga (Fig. 6, groups A1 and A2; Fig. 7, group

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Figure 6. Normalized probability density functions for select Cambrian samples of southwestern Laurentia. Samples with numbers in red are from this study. Dates are 206Pb/238U for dates <1500 Ma, and 207Pb/206Pb for dates >1500 Ma. Samples with <1% probability of concordance were filtered from the data set. Curve fill color corresponds to the sampled unit (Pk.—Peak; R.—Range; Cr.—Creek; S.—Sisters). Probability density functions are normalized for each detrital zircon facies (A1, A2, B, C, D, E, F). Outliers are samples that did not fall within a facies defined using the mul- tidimensional scaling plot (see Fig. 4). A line at 1.8 Ga is provided as a visual reference for the age of the Paleoproterozoic population discussed in the text. Data sources and details of the sample locations are provided in Table 1. Geologic time scale abbreviations: MC—Mesozoic–Cenozoic; Pal.—Paleozoic; Neopr.—Neoproterozoic; Mesopr.—Mesoproterozoic; Paleoprot.—Paleoproterozoic; NA—Neoarchean; MA—Mesoarchean; PA—Paleoarchean.

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Figure 7. Normalized probability density functions for select Neoproterozoic samples of western Laurentia. Samples with numbers in red are from this study. Dates are 206Pb/238U for dates <1500 Ma, and 207Pb/206Pb for dates >1500 Ma. Samples with <1% probability of concordance were filtered from the data set. Curve fill color corresponds to the sampled unit. Probability density Figure 8. Map showing the geographic extent of detrital zircon facies defined by multidimen- functions are normalized for each detrital zircon facies (A1, B, C). A line at 1.8 Ga provided is sional scaling; also shown are the major tectonic provinces of North America (modified after provided as a visual reference for the age of the Paleoproterozoic population discussed in the Whitmeyer and Karlstrom, 2007; Grouse Creek Block based on Gaschnig et al., 2013). Abbrevia- text. Data sources and details of the sample locations are provided in Table 1. Geologic time tions: SCA—Swift Current anorogenic province; ECG—Elves Creek gneiss. Bold red line depicts scale abbreviations: MC—Mesozoic–Cenozoic; Pal.—Paleozoic; Neopr.—Neoproterozoic; Me- the approximate location of the geological features that constitute the Transcontinental Arch sopr.—Mesoproterozoic; Paleoprot.—Paleoproterozoic; NA—Neoarchean; MA—Mesoarchean; (TCA; modified after Carlson, 1999). Also shown are summary probability density functions for PA—Paleoarchean. each of the six facies, highlighting prominent modes in their detrital zircon populations; curve fills correspond to the major tectonic provinces of North America depicted in the map. Dates are 206Pb/238U for dates <1500 Ma, and 207Pb/206Pb for dates >1500 Ma. Samples with <1% probability of concordance were filtered from the data set. N is the number of samples; n is the number A1). Minor early Mesoproterozoic 1.5–1.3 Ga populations are found in the of measurements. A reference line at 1.8 Ga is provided as a visual reference. Geologic time southernmost A1 samples and the majority of A2 samples. Facies A2 is dif- scale abbreviations: MC—Mesozoic–Cenozoic; Pal.—Paleozoic; Neopr.—Neoproterozoic; Me- sopr.—Mesoproterozoic; Paleoprot.—Paleoproterozoic; NA—Neoarchean; MA—Mesoarchean; ferentiated from A1 based on the occurrence of significant populations of ca. PA—Paleoarchean. 1.4 Ga and Neoproterozoic to Cambrian zircons. Geographically, A2 samples are found in the west and generally overlie A1 samples. Facies B is found in samples from the Tintic, Osgood Mountain, and Stirling characterized by an Archean (mainly 3.0–2.5 Ga) population, subequal late Pa- formations of northern Utah, southern California, and Nevada (United States) leoproterozoic 1.9–1.6 Ga (mode ca. 1.8 Ga) and early Mesoproterozoic 1.5–1.3 (Figs. 5, 8). This facies is characterized by an Archean to early Paleoprotero- Ga (modes at 1.42 and 1.36 Ga) populations, and a dominant late Mesopro- zoic (mainly 3.0–2.4 Ga) population, subequal late Paleoproterozoic 1.9–1.7 terozoic ca. 1.2 to ca. 1.0 Ga (modes at 1.2 and 1.1 Ga) population (Figs. 6 and Ga (mode ca. 1.8 Ga) and early Mesoproterozoic 1.5–1.3 Ga (mode ca. 1.4 Ga) 7, group C). populations, and a small late Mesoproterozoic 1.3–1.0 Ga (mode ca. 1.1 Ga) Facies D is found in samples from the Flathead, Sawatch, Prospect Moun- population (Figs. 6 and 7, group B). tain, Ignacio, and Tapeats formations of Wyoming, Utah, Colorado, and Ar- Facies C is found in samples from the Osgood Mountain, Tintic, Prospect izona (United States) (Fig. 8). These samples are characterized by nearly bi- Mountain, Proveedora, and Mutual formations of Utah, southern Idaho, and modal detrital zircon populations dominated by late Paleoproterozoic 1.8–1.6 Nevada (United States) and northern Mexico (Figs. 5, 8). These samples are Ga (mode ca. 1.7 Ga) and narrow early Mesoproterozoic (mode ca. 1.4 Ga)

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populations (Fig. 6, group D). The relative abundances of the Paleoprotero- the occurrence of two distinct Paleoproterozoic detrital zircon populations is zoic and Mesoproterozoic populations vary, but are subequal in most sam- widespread, and their origin is discussed below. ples. Archean grains are scarce, representing <1% of the zircons analyzed. The provenance of zircons that compose the older >1.8 Ga population is Minor late Mesoproterozoic 1.3–1.0 Ga populations are found in the some straightforward. Zircons with ages >1.8 Ga could derive from relatively prox- samples (Fig. 6, group D, samples 44, 53, and 60). imal Paleoproterozoic arcs and orogenic belts, such as the Taltson or Rimbey Facies E is found in one sample from the Flathead Sandstone of south- arcs which record the assembly of the Laurentian craton and are interpreted in ernmost Wyoming and the Tapeats, Wood Canyon, and Bliss formations of the subsurface of Alberta (Canada) based on borehole penetrations and geo- Nevada, Arizona, California, and New Mexico (United States) (Fig. 8). These physical measurements (Fig. 8; Ross et al., 1991). Alternatively, these grains samples are characterized by late Paleoproterozoic 1.8–1.6 Ga (mode <1.7 could derive from the Trans-Hudson province to the east where these ages are Ga), early Mesoproterozoic 1.5–1.3 Ga (mode 1.4 Ga), and prominent late Me- common (Ross et al., 1991; Hoffman, 1988). soproterozoic 1.3–1.0 Ga (mode 1.2 Ga) populations (Fig. 6, group E). The origin of the younger <1.8 Ga Paleoproterozoic zircons is more diffi- Facies F is found in samples from the Wood Canyon and Campito Forma- cult to determine. The younger components could derive from the 1.8–1.7 Ga tions of California and Nevada and two samples from the Bliss Sandstone Yavapai province to the south (Fig. 8), which was exposed until at least the of southern New Mexico (Fig. 8). These samples are dominated by a single middle Cambrian (May et al., 2013). Magmatism in the Yavapai province was narrow mode at ca. 1.1 Ga. Scattered dates between 1.5 and 1.2 Ga are pres- continuous between 1.78 and 1.71 Ga with a magmatic peak at 1.74 Ga (Bick- ent in most samples (Fig. 6, group F). Two samples (76 and 77) of the Bliss ford et al., 2008). As such, the timing of magmatism in the Yavapai province Sandstone contain abundant zircons that yield dates near 0.5 Ga. is a poor fit to the northern Cambrian rocks. Grains younger than 1.75 Ga are not common in facies A1 and A2 samples, and the mode of the <1.8 Ga zircon population from Cambrian rocks is older (1.78 Ga). Furthermore, the Yavapai PROVENANCE INTERPRETATION OF DETRITAL ZIRCON FACIES province was extensively intruded by ca. 1.4 Ga A-type granites (Anderson and Bender, 1989) that provide abundant zircons to Cambrian sedimentary The provenance of Cambrian and Neoproterozoic the detrital zircon facies rocks in that region (e.g., samples from facies D). If the <1.8 Ga population of described above can be used to constrain large-scale sediment source areas Paleoproterozoic grains was derived from the Yavapai province, then a com- and dispersal systems active during the Cambrian throughout western Lauren- mensurate population of Mesoproterozoic zircons would be expected. Minor tia. Here we focus on large-scale patterns of sediment dispersal, and as such, Mesoproterozoic populations are found in some samples (e.g., Fig. 6, group important small-scale variations in the provenance of individual samples may A1, samples 1, 2, 17, 28, 29, 31, 35), but are largely absent in most. Also, paleo- not be addressed. flow directions in the Cambrian are dominantly west directed (Mountjoy and Aitken, 1963; Young, 1979; Devlin and Bond, 1988), inconsistent with derivation from the Yavapai province. For these reasons we find it unlikely that ca. 1.78 Ga Facies A1 and A2 zircons in Cambrian rocks were sourced from the Yavapai province. The Little Belt arc is another possible source area for these grains (Fig. Provenance interpretations for Archean components of the northern fa- 8). Magmatism in the Little Belt arc is interpreted to record Paleoproterozoic cies, A1 and A2, are relatively straightforward. Archean components in these convergence between the Hearne and Wyoming cratons (Mueller et al., 2002). samples likely derive ultimately from Laurentian Archean provinces, such as Harms et al. (2004) used evidence of deformation and metamorphism in base- the Hearne, Superior, Wyoming, and Medicine Hat blocks that were exposed ment inliers in western Montana and Idaho (United States) to suggest that to the east prior to Cambrian transgression (Fig. 8) (Hoffman, 1988; Whit- convergence between the cratons culminated in the 1.78–1.72 Ga Big Sky oro- meyer and Karlstrom, 2007). gen. If arc magmatism was continuous until collision at 1.78 Ga, then parts of The provenance of Paleoproterozoic zircon populations is more compli- the Little Belt arc may be young enough to provide the <1.8 Ga components cated. Overall, Paleoproterozoic grains from A1 and A2 samples yield a mode observed in Cambrian detrital zircon populations. However, the only exposed of 1.78 Ga (Fig. 8, groups A1 and A2). However, the asymmetry of the peak in portions of the Little Belt arc yield zircon crystallization ages of ca. 1.86 Ga many A1 and A2 probability density functions suggests that a smaller pop- (Mueller et al., 2002), and no evidence of major magmatism <1.8 Ga has been ulation of older zircons is present and is not well resolved in our data set. found. As such, the importance of the Little Belt arc as a source area in the Inspection of the individual probability density functions reveals that several Cambrian remains unclear. A1 samples show two modes in their Paleoproterozoic populations (e.g., Fig. The <1.8 Ga zircons could derive from the ca. 1.77 Ga Swift Current anoro- 6, group A1, samples 7, 8, 16, 22, 27 and 35), an older peak at ca. 1.84 Ga and genic province (Collerson et al., 1988). The Swift Current anorogenic province a younger peak at 1.78 Ga. Paleoproterozoic populations in facies A2 also was originally described based on borehole intersections in the subsurface show two modes at 1.84 and 1.78 Ga (Fig. 8, group A2). Our data suggest that near Swift Current, Saskatchewan (Canada) (Fig. 8) and may be related to more

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widespread Paleoproterozoic magmatism in the Hearne province (Peterson et difficult. Neoproterozoic to Cambrian zircon populations were likely recycled al., 2015). Zircon crystallization ages of 1779 ± 3 Ma and 1820 ± 1 Ma for gran- from older Windermere deposits, with the exception of Cambrian grains, some ites in the otherwise Archean Loverna block of the Hearne craton in south- of which may have been syndepositional. eastern Alberta, and interpretations of aeromagnetic data, suggest that the Swift Current anorogenic province may be widespread in southeastern Alberta (Ross et al., 1991). Facies B Farther east in Minnesota and Wisconsin (United States), post-orogenic granitoids that intrude the Penokean terrane yield ages between 1.80 Ga and Samples exhibiting facies B detrital zircon populations are found in Utah, 1.75 Ga (mode at 1.77 Ga) that overlap with <1.8 Ga zircon populations in facies southern Idaho, and northern Nevada (Fig. 8). Geographic overlap exists be- A1 and A2 basal Sauk sequence sandstones (Holm et al., 2005). Derivation tween facies B samples and those of facies A, C, and D, likely reflecting the of basal Sauk sequence Paleoproterozoic zircon populations from this region complexity of source areas and abundant recycling of older sedimentary suc- would require transport of <1.8 Ga zircon populations across the predomi- cessions in this area. nantly >1.8 Ga Trans-Hudson orogen. The absence of prominent >1.8 Ga pop- Archean zircons are found in all facies B samples (Fig. 6, group B). Crystal- ulations in some samples (e.g., samples 22, 25, 27 and 35) and the dominance line sources for Archean zircons include the Grouse Creek block of northeast- of <1.8 Ga populations in most A1 and A2 samples favors derivation from a ern Nevada and southern Idaho, and the Wyoming province to the east (Fig. 8) source area west of the Trans-Hudson, but we cannot rule out derivation from (Whitmeyer and Karlstrom, 2007). Alternatively, Archean zircons could be re- the mid-continent region. cycled from older Neoproterozoic successions, such as the Mutual Formation We interpret that <1.8 Ga Paleoproterozoic zircons in facies A1 and A2 Cam- which underlies many of the Cambrian facies B sample locations and contains brian samples most likely derive from the Swift Current anorogenic province Archean grains (Fig. 7, group C; see discussion below). to the east. The widespread occurrence of these grains in Cambrian samples Facies B detrital zircon populations are characterized by prominent Paleo- suggests that the Swift Current anorogenic province may be more extensive proterozoic zircon populations with a mode ca. 1.8 Ga (Fig. 8). As in facies A1 than originally mapped by Collerson et al. (1988). Hafnium isotopic evidence and A2, zircons with ages >1.8 Ga could derive from juvenile arcs and orogenic could further constrain the provenance of ˂1.8 Ga zircons. Source areas in belts associated with assembly of the Laurentian craton. Proximal sources for the Little Belt arc, Rimbey arc, parts of the Trans-Hudson orogen, or post-oro- these grains would include orogenic belts associated with the amalgamation genic plutons in the Penokean terrane would likely exhibit juvenile signatures, of Mojavia and the Grouse Creek block (Fig. 8). Unlike our interpretation for whereas Nd isotopic data requires that the Swift Current anorogenic province facies A1 and A2, younger Paleoproterozoic zircons (<1.8 Ga) in facies B likely formed by melting of older Archean crust (Collerson et al., 1988). derive from the Yavapai province to the east. This interpretation is supported Neoproterozoic to Cambrian detrital zircon populations in facies A2 sam- by an abundance of early Mesoproterozoic grains, consistent with deriva- ples are related to rifting of western Laurentia to form the Neoproterozoic tion from A-type granites that intrude the Yavapai province (Anderson and Windermere basin and ultimately the western Laurentian passive margin in Bender, 1989). the Cambrian. Evidence of Neoproterozoic to Cambrian magmatism of various Late Mesoproterozoic populations are found in all facies B samples and ages has been described along the length of the orogen (Colpron et al., 2002, are composed of a wide range of ages between 1.25 and 1.0 Ga with a mode and references therein). Proterozoic populations were likely eroded from older ca. 1.11 Ga (Fig. 8). This broad distribution of ages is distinct from that of fa- sedimentary and volcanic sequences, whereas Cambrian magmatism may cies E samples, which are dominated by ca. 1.2 Ga zircons derived from local have been syndepositional (e.g., Colpron et al., 2002). plutonic sources in southern New Mexico (Amato and Mack, 2012), and from In summary, detrital zircon populations from groups A1 and A2 derive that of facies F samples, which are nearly unimodal at ca. 1.1 Ga (Fig. 8, group mainly from Laurentian crystalline sources to the east (Fig. 9, A1/A2), consis- B versus E and F). The range of late Mesoproterozoic ages in facies B samples tent with paleoflow measurements that are dominantly west directed (Mount- is similar to that found in the Neoproterozoic Uinta Mountain Group of north- joy and Aitken, 1963; Young, 1979; Devlin and Bond, 1988). The predominance eastern Utah (Mueller et al., 2007; Dehler et al., 2010; Kingsbury-Stewart et al., of <1.8 Ga grains in Cambrian rocks suggests that the Swift Current anorogenic 2013) and to late Mesoproterozoic zircon populations in the Mutual Formation province may be more widespread than previously mapped, and was likely a (Fig. 7, group C) that underlies many of the facies B samples. Much of the sed- significant source of sediment in the Cambrian. The similarity between Cam- iment in the Uinta Mountain Group is interpreted to derive from Grenville-age brian A1 and A2 signatures and those of the underlying Neoproterozoic sam- (1.3–1.0 Ga) plutonic rocks exposed in the southern Grenville orogen. The Uinta ples (Fig. 7, group A1) suggests little change in provenance during much of the basin is one of a number of Neoproterozoic basins that received detritus from late Neoproterozoic and into the early Cambrian. Furthermore, the similarity the eroding Grenville orogen in the Neoproterozoic, an event referred to as between Neoproterozoic and Cambrian rocks makes evaluating the impor- the “Grenville flood” (Rainbird et al., 1997; Mueller et al., 2007). The similarity tance of local recycling of Neoproterozoic sedimentary rocks in the Cambrian between Mesoproterozoic detrital zircon populations of the Mutual Formation

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Figure 9. Summary provenance interpretations for the six detrital zircon facies discussed in the text; also shown are the major tectonic provinces of North America (modified after Whitmeyer and Karlstrom, 2007; Grouse Creek Block based on Gaschnig et al., 2013). Symbols used for sample lo- cations are the same as those used in Figure 1. Bold red line depicts the approximate location of the geological features that constitute the Trans- continental Arch (modified after Carlson, 1999); black arrows indicate inter- preted sediment pathways.

and the Uinta Mountains Group suggests that they shared a similar source, and samples (ca. 1.11 Ga), and could not have supplied the broad range of late Me- that both ultimately derive from the Grenville orogen (Yonkee et al., 2014). soproterozoic ages found in them. Furthermore, the lack of late Mesoproterozoic If Grenville detritus in the Mutual Formation was derived from the southern grains in facies D samples, some of which were deposited directly atop the Pikes Grenville orogen, was this also true for Grenville detritus in Cambrian rocks? Peak Granite (Fig. 6, group D, samples 48 and 49), suggests that the Pikes Peak Yonkee et al. (2014) interpreted lower Cambrian strata in western Utah to de- Granite was not a significant sediment source at this time. We speculate that rive from the region of the Transcontinental Arch, a northeast-southwest–aligned Grenville detritus in facies B samples was derived from local recycling of older basement high that runs roughly down the middle of the Laurentian craton that sedimentary successions rich in these components. was onlapped during Sauk transgression (Sloss, 1963, 1988; see Carlson [1999] The geographic and temporal distribution of Cambrian samples containing for an excellent discussion; Fig. 8). However, late Mesoproterozoic plutons in Col- Grenville detritus supports this interpretation. In north-central Utah, facies A, orado, such as the ca. 1.09 Ga Pikes Peak Granite (Schärer and Allègre, 1982), B, C, and D rocks are found in close proximity, commonly occurring at the are younger than the mode of the late Mesoproterozoic population in facies B same locality (Fig. 8). Evidence for crustal thinning in the lower Cambrian in

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western Utah (Yonkee et al., 2014) could explain rapid changes in detrital zircon imal sources within the Yavapai and Mazatzal provinces (Fig. 8). The Paleop- facies. Extensional faulting would have allowed the Cambrian sedimentary sys- roterozoic zircon population has a peak age of ca. 1.7 Ga and likely includes tem intermittent access to older Neoproterozoic rocks rich in Mesoproterozoic contributions from both the underlying Yavapai province and the Mazatzal zircons. Furthermore, rapid changes in paleodrainage patterns in an evolving rift province to the south. The near absence of >1.8 Ga and Archean grains indi- landscape could explain similarly rapid temporal and geographic variability in cates that little detritus was derived from the Wyoming craton to the north or detrital zircon facies in this region (Cawood et al., 2012). Facies B detrital zircon Paleoproterozoic arcs and orogens to the northeast and west. populations likely derive from mixing of detritus from Archean and Paleopro- Mesoproterozoic populations likely derive from A-type plutons that ex- terozoic crystalline source areas to the east, such as the Wyoming and Yavapai tensively intrude the Yavapai and Mazatzal provinces (Fig. 8; Anderson and provinces, with late Mesoproterozoic grains recycled from older sedimentary Bender, 1989). The peak age (1.43 Ga) is similar to the mode in the distribution successions (Fig. 9B). of ages for early Mesoproterozoic plutons in Laurentia (Goodge and Vervoort, 2006). Small variations in the mode of the Mesoproterozoic population likely reflect subtle differences in the ages of early Mesoproterozoic plutons in the Facies C sediment source areas of the samples (Fig. 6, group D). Minor late Mesoproterozoic populations yield a mode of ca. 1.06 Ga and Facies C detrital zircon populations are similar to those of facies B, except overlap in age with the Grenville orogen in the south and east of Laurentia that the proportions of Paleoproterozoic and Mesoproterozoic zircon populations (1.3–1.0 Ga; Fig. 8). Alternatively, these grains could derive from the Pikes Peak differ and the age of the Paleoproterozoic mode is more variable (Fig. 6, group Granite, upon which samples 48 and 49 were deposited. The similarity be- B versus C; Fig. 8). Facies B detrital zircon populations are dominated by late Pa- tween the mode of the late Mesoproterozoic population (ca. 1.06 Ga) and that leoproterozoic zircons (1.9–1.6 Ga; 42% of dates) with lesser proportions of early of the Pikes Peak Granite (ca. 1.09 Ga) suggests that local sourcing of these (1.6–1.3 Ga; 26%) and late (1.3–1.0 Ga; 13%) Mesoproterozoic zircons. In contrast, minor components is likely. facies C detrital zircon populations are dominated by late Mesoproterozoic zir- We interpret that Cambrian detrital zircons of facies D were derived from cons (47%) with lesser proportions of late Paleoproterozoic (20%) and early Me- relatively local sources within the Yavapai and Mazatzal provinces (Fig. 9D). soproterozoic grains (22%). The lack of Archean and >1.8 Ga zircon populations suggests that little detritus We interpret facies C zircon populations to derive from the same source areas was derived from the Wyoming craton to the north in the middle to late Cam- as facies B (described above). Of the eleven samples that exhibit facies C detrital brian, consistent with paleoflow measurements that suggest transport domi- zircon populations, seven are from the Neoproterozoic Mutual Formation of Utah nantly to the west (Stewart et al., 2001, and references therein). The origin of and southern Idaho (Fig. 7, group C). As discussed previously, sediment of the late Mesoproterozoic populations is difficult to determine due to their relative Mutual Formation was likely derived from the Grenville orogen, while Cambrian scarcity, but they could derive from local sources such as the Pikes Peak Gran- facies C samples in Utah likely derive from local recycling of the Mutual For- ite within the Yavapai province. mation or from the Uinta Mountain Group, which contain similar detrital zircon populations (Fig. 7, group C). Variability in the age of the Paleoproterozoic mode in facies C samples may reflect variable contributions from the Yavapai province Facies E to the east and older 1.8–1.9 Ga arcs in western Utah and Nevada. The Proveedora Formation of northern Mexico also exhibits a facies C detri- Facies E detrital zircon populations are found in two geographically iso- tal zircon population. Overall, detrital zircon populations in the Proveedora are lated regions. The majority of facies E samples are found at the south end of similar to facies E samples from the Bliss Sandstone in southern New Mexico the studied area, mainly in samples of the late Cambrian Bliss Sandstone of except that the mode of the late Mesoproterozoic population in the Proveedora southwestern New Mexico (Amato and Mack, 2012), our Tapeats Sandstone (ca. 1.1 Ga) is younger than that in the Bliss to the north (ca. 1.2 Ga). We interpret samples from southern Nevada and central Arizona, and one sample of the the Proveedora sandstone to derive from the same source regions as facies E Wood Canyon Formation in southern California (Fig. 8). Sample 59 from the samples (discussed below), with local input of ca. 1.1 Ga grains from intrusions Tapeats Sandstone in southern Nevada was grouped with facies D samples of this age found in northern Mexico (Iriondo et al., 2004) (Fig. 9C). based on the MDS plot (Fig. 4). We have chosen to group it with facies E sam- ples for our provenance interpretation due to the similarity in the age of its Paleoproterozoic mode to other facies E samples and the occurrence of a large Facies D population of Phanerozoic grains in sample 59 that are uncommon in facies D samples (Fig. 6, group D).One sample of the Flathead Sandstone collected Facies D detrital zircon populations are characterized by bimodal Paleopro- in southern Wyoming also exhibits facies E detrital zircon populations (Fig. 6, terozoic and Mesoproterozoic zircon populations and mainly derive from prox- group E, sample 33). Provenance interpretations for these two distinct regions

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will be discussed separately due to subtle but important differences in their late Cambrian. Significant differences in the provenance of the Tapeats in the detrital zircon populations. Grand Canyon and the Tapeats in central Arizona and southern Nevada are Detrital zircon populations in the southern geographic occurrence of facies consistent with the presence of the arch during the middle to late Cambrian. E show significant variability, reflecting the importance of local source areas Facies E detrital zircon populations were derived from a mixture of sources (Fig. 6, group E) (Amato and Mack, 2012). Facies E is dominated by a younger in the Mazatzal and southern Yavapai provinces combined with locally derived Paleoproterozoic zircon population (mode <1.7 Ga), reflecting increased input detritus from Mesoproterozoic and Paleozoic intrusive rocks in southwestern of detritus from the Mazatzal province relative to facies D. Mesoproterozoic zir- New Mexico (Fig. 9E). The importance of farther-traveled detritus from Gren- cons derive from A-type anorogenic granites that are common in New Mexico ville sources to the east cannot be ruled out. We suggest that a late Cambrian (Fig. 8; Amato and Mack, 2012; Amato et al., 2011). sediment delivery pathway skirted the southern limit of the Transcontinental Late Mesoproterozoic zircon populations are a major component of many Arch, delivering sediment as far as southern Nevada and California (Fig. 9E). facies E samples. The mode of the late Mesoproterozoic population (ca. 1.2 Ga) The northern geographic occurrence of facies E is enigmatic. To the north, is similar to the age of plutons in western Texas and southern New Mexico Cambrian sandstones exhibit facies A1 and A2 zircon populations, character- (Bickford et al., 2000; Rӓmö et al., 2003; Amato and Mack, 2012; Howard et al., ized by abundant Archean and Paleoproterozoic (mode ca. 1.8 Ga) and minimal 2015), but also overlaps with widespread Grenville plutonism in the east and Mesoproterozoic zircons (e.g., Fig. 6, group A1, samples 25, 27, and 28). This southeast of the United States. Sources of late Mesoproterozoic grains to the contrasts strongly with the southern Wyoming facies E sample, which exhibits north, such as the Pikes Peak Granite, are younger (ca. 1.09 Ga) and unlikely to younger Paleoproterozoic populations (mode <1.7 Ga), prominent populations have contributed to facies E samples. of Mesoproterozoic grains, and abundant late Mesoproterozoic ca. 1.1 Ga zir- Middle Cambrian zircons are abundant in a number of western facies E cons (Fig. 6, group E, sample 33). However, the facies E sample from the north- samples (Fig. 6, group E, samples 59 and 65). Amato and Mack (2012) used pa- ern geographic region is not dissimilar to facies D samples of central Colorado leocurrent measurements and the geographic extent of Bliss Sandstone sam- (Fig. 6, group D, samples 45, 46, 48 and 49). Facies D samples are characterized ples containing Cambrian zircons to demonstrate that these zircons derived by a similar Paleoproterozoic zircon population (mode ca. 1.7 Ga) and promi- from the 510 ± 5 Ma Florida Mountains granite. Our samples of the Tapeats nent Mesoproterozoic population, but lack significant Mesoproterozoic grains. Sandstone from central Arizona and southern Nevada (Fig. 4, group E, sam- The occurrence of late Mesoproterozoic ages and the relatively young mode ples 59 and 65) also contain abundant middle Cambrian detrital zircons that of the dominant Mesoproterozoic zircon population in this sample (mode of overlap in age with the Florida Mountains granite. Eight measurements from 1.38 Ga versus ca. 1.43 Ga in facies D) likely resulted in its inclusion in facies E our sample in central Arizona and seven measurements from southern Nevada rather than facies D in the MDS plot (Fig. 4). We interpret the northern occur- yield concordant ages of 502.8 ± 8.1 Ma and 504.8 ± 8.2 Ma (206Pb/238U dates; rence of facies E sample to result from local sourcing of younger Mesoprotero- 2σ including all sources of random and systematic uncertainty), respectively zoic A-type granites and detritus from the Pikes Peak Granite (Fig. 9E). (Figs. 8, 10). These ages are the same, within uncertainty, as the age of Florida Mountains granite and could indicate that Florida Mountains granite–derived detritus reached as far west as southern Nevada in the late Cambrian. This Facies F finding is consistent with paleocurrent data that indicate generally east-to- west transport at this time (Stewart et al., 2001; Amato and Mack, 2012). Facies F samples are distinct amongst Cambrian detrital zircon popula- Other components of the detrital zircon signature support a connection be- tions of western Laurentia. Facies F detrital zircon populations are character- tween the Tapeats Sandstone of central Arizona and southern Nevada with the ized by a unimodal age distribution with a mode ca. 1.1 Ga (Fig. 8) and are Bliss Sandstone of southwestern New Mexico. The modes of the Paleoprotero- found in samples of the Wood Canyon Formation of California and Nevada, the zoic zircon populations in our samples (1.67 Ga) are consistent with derivation Campito Formation of California, and two samples from the Bliss Sandstone predominantly from the Mazatzal province, and are similar to that of the Bliss of southwestern New Mexico. The provenance of the two Bliss Sandstones Sandstone (1.68 Ga; Amato and Mack, 2012). While similar Paleoproterozoic with facies F detrital zircon populations was interpreted by Amato and Mack populations are present in Tapeats Sandstone samples of the Grand Canyon, (2012) to result from local sourcing of ca. 1.1 Ga grains from proximal plutons Arizona (Fig. 6, group D, samples 60 and 61; Gehrels et al., 2011), the mode of in New Mexico. the distribution is older (1.71–1.73 Ga), suggesting greater input from the older The origin of the ca. 1.1 Ga grains in the Wood Canyon and Campito For- Yavapai province. Likewise, Mesoproterozoic populations in the Grand Canyon mations was investigated by Howard et al. (2015) using zircon Hf and whole- samples are younger (ca. 1.1 Ga) and less abundant than those found in the rock Nd isotopic data. Based mainly on Hf isotopic data, they concluded that Bliss and Tapeats from Arizona and Nevada (Amato and Mack, 2012). 1.1 Ga zircons most likely derive from plutons exposed in the Llano uplift of Our results support the interpretation of Amato and Mack (2012) that the Texas, rather than more proximal sources such as the Pikes Peak Granite or Transcontinental Arch formed a significant drainage divide in the middle to similar-age plutons in southern New Mexico and Sonora (Mexico). However,

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Figure 10. Weighted average 206Pb/238U ages for Cambrian grains from samples 59 and 65 of the Tapeats Sand- stone (NV—Nevada; AZ—Arizona); uncertainties are 2σ and include all random and systematic components of uncertainty. Measurement shown in gray was not in- cluded in the weighted average. MSWD—mean square of weighted deviates.

this raises an interesting problem because it requires that sediments transport- This finding supports previous studies that have demonstrated the importance ing major 1.1 Ga zircon populations bypassed the area of Tapeats deposition, of local sedimentary sources of detrital zircon populations during the early part where these ages are not common (Fig. 8; Howard et al., 2015). Maximum dep- of the Sauk transgression (Hadlari et al., 2012; Yonkee et al., 2014). ositional ages from our data set resolve this issue. The occurrence of signifi- cant numbers of ca. 505 Ma grains in the Tapeats Sandstone of central Arizona and Nevada requires that these units be at least 30 m.y. younger than the Wood IMPLICATIONS FOR COLLSIONAL MODELS OF THE Canyon, which is thought to have been deposited in the latest Neoproterozoic CORDILLERAN OROGEN to earliest Cambrian (starting at 548 Ma) (Corsetti and Hagadom, 2000). As such, the distinct detrital zircon signature of the Wood Canyon Formation likely For over 40 yr, most tectonic models for the North American Cordillera represents an earlier phase of sediment delivery that predated the deposition have invoked accretion of terranes onto North America to explain Paleozoic of the facies E Tapeats and Bliss Sandstones. Furthermore, the Neoproterozoic to Cenozoic orogenesis (Dewey and Bird, 1970; Dercourt, 1972; Monger et al., Stirling Formation, which underlies the Wood Canyon in southern Nevada and 1972; Monger, 1997; DeCelles, 2004; Yonkee and Weil, 2015). In these broadly parts of California, is characterized by a facies B detrital zircon population (Fig. accepted models, the Cordilleran orogen is the product of mainly orogen-per- 7, group B; Fig. 8), with diverse Paleoproterozoic and Mesoproterozoic ages. pendicular shortening caused by eastward obduction of terranes from the This suggests that the source area and sediment dispersal systems that sup- subducting plate (e.g., Monger, 1997; Dickinson, 2004; Nelson et al., 2013). De- plied detritus to facies E rocks were not active in the latest Neoproterozoic. As formation of the Cambrian to Triassic platform succession of western Lauren- such, the sedimentary system that supplied facies F detrital zircon populations tia occurred above an east-dipping subduction zone during the Cretaceous to was likely short lived and, based on the limited distribution of facies F deposits, Cenozoic Sevier and Laramide orogenies. This model will be referred to herein aerially restricted (Fig. 9F). as the “general accretionary model”. Despite its broad acceptance, some authors have observed that a num- ber of geological and geophysical observations are difficult to reconcile with SUMMARY OF PROVENANCE INTERPRETATION the general accretionary model for the Cordillera. Most importantly for this discussion: With the possible exception of facies F, detrital zircon populations in basal 1. The presence of two west-facing Paleozoic platform successions along Sauk sequence sandstones are derived from proximal crystalline and sedimen- much of the length of the Cordillera, the Rocky Mountain and Cassiar tary source areas with little evidence of long-distance transport. Where basal platforms in Canada and the Antler and North American platforms in the Sauk sequence sandstones are deposited over older sedimentary successions, United States, that have different geological histories and faunal assem- they may have inherited major components of their detrital zircon populations blages (Johnston and Borel, 2007; Johnston, 2008; Hildebrand, 2009) or be entirely derived from recycling of the older units. The importance of local indicates that they were separated by a broad ocean basin during the recycling is well demonstrated in western Utah, where facies B, C, and D are Paleozoic (Johnston and Borel, 2007; Johnston, 2008). found in close geographic proximity and are interpreted to represent mixing 2. Paleomagnetic constraints on the latitude of many of the terranes that of zircon derived from ultimate crystalline and recycled sedimentary sources. compose the orogen suggest that they were thousands of kilometers to

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the south of their current positions during the Late Cretaceous (e.g., Ir- Neoproterozoic successions on which they were deposited. As such, the lack ving et al., 1996). of facies C detrital zircon populations in samples from the North American These and other perceived shortcomings have led some (Johnston and platform is readily explained by a lack of proximal Neoproterozoic rocks with Borel, 2007; Johnston 2008; Hildebrand, 2009) to propose alternative models facies C detrital zircon populations to recycle. for the orogen. In these models, westward subduction of the North American The geographic distribution of detrital zircon facies in rocks of the Cas- plate leads to Jurassic (Johnston, 2008) or Cretaceous (Hildebrand, 2009) col- siar-Antler platform is similar to that of the North American platform, sug- lision of North America with a composite intra-oceanic arc terrane or “ribbon gesting that they shared similar source areas and limiting the north-south continent”. Models involving westward subduction reconcile the presence of offset that has occurred between them (Fig. 11). For example, in the north, two Paleozoic platforms in the western Cordillera. The western platform suc- samples exhibiting A1 and A2 detrital zircon facies are found in both plat- cession, with its distinct geological history, including the presence of thick Me- forms along >1500 km of strike length (Fig. 11, sections U and X). Farther soproterozoic and Neoproterozoic sedimentary successions, and exotic fauna, south, samples of the Antler platform that exhibit facies D detrital zircon pop- is part of the ribbon continent, far traveled, and was juxtaposed with the North ulations are found in west-central Utah at roughly the same latitude as facies American margin during the Mesozoic. Northward translation of the ribbon D samples from the North American platform in Colorado and northern Ar- continent during final accretion to North America is invoked to reconcile the izona (Fig. 11, section Y). Likewise, facies F samples are found in positions paleomagnetic data. These models will be referred to as the “ribbon continent interpreted to be part of the North American platform and to the west in model”, as orogeny in the eastern parts of the Cordillera occurred due to colli- the Antler platform, all within southern California and southernmost Nevada sion of the North American plate with a composite ribbon continent. (Fig. 11, section Z). The general accretionary and ribbon continent models for the Cordillera Could this arrangement be produced by collision of a ribbon continent? make different predictions for the provenance of Cambrian sandstones de- The origin of the ribbon continent is not well constrained. If the crust of the posited on the North American and Cassiar-Antler platforms. In the general ribbon continent were a sliver rifted away from Laurentia in the Cambrian accretionary model, western Neoproterozoic to Cambrian units (McNaugh- (Johnston, 2001), rocks of the Cassiar-Antler platform and the North Ameri- ton, Hamill, Three Sisters, Quartzite Range, Geertsen Canyon, Prospect can platform could have had access to similar-aged source areas and could, Mountain, and Wood Canyon formations), which compose the base of the therefore, exhibit a similar geographic distribution of detrital zircon facies. Paleozoic succession of the Cassiar-Antler platform, represent distal equiv- However, this scenario would require that the ribbon continent had drifted alents of easterly units (Gog, Flathead, Tintic, Sawatch, Ignacio, Bliss, and far enough relative to the Laurentian craton to satisfy the paleomagnetic and Tapeats formations) deposited as part of the North American platform. Al- faunal data sets before being juxtaposed and translated in the Mesozoic to though the western units are somewhat older (latest Neoproterozoic to approximately the same latitude from where it was derived in the Cambrian. early Cambrian) than eastern units (middle to upper Cambrian), the general The geographic continuity of detrital zircon facies between rocks of the Cas- accretionary model predicts that rocks of the Cassiar-Antler platform were siar-Antler and North American platforms is consistent with the general ac- proximal to Laurentia in the Cambrian and, as such, may have had access cretionary model for the orogen and argues against major orogen-parallel to similar provenance areas in Laurentia and therefore may contain similar offset between them. detrital zircon facies. In contrast, the ribbon continent model predicts that deposition of the western units occurred on an isolated landmass (Johnston, 2008; Hildebrand, CONCLUSIONS 2009) and would not necessarily share similar source areas in the Cambrian. Furthermore, the ribbon continent model stipulates that significant late Cre- Detrital zircons populations from Cambrian sandstones of the basal Sauk taceous to Cenozoic dextral translation of western Cassiar-Antler platform sequence are divided into six major facies groups based on statistical compar- relative to North America occurred prior to final docking in the early Cenozoic ison. The geographic extents of the major facies groups are consistent with (e.g., Hildebrand, 2015; Sigloch and Mihalynuk, 2013). As such, Cambrian de- local derivation of sediments from crystalline source areas in western Lauren- trital zircon facies in western units would likely be different from those of the tia, with important local recycling where older sedimentary successions were North American platform to their east. made available for erosion by rifting. Northern rock units are characterized Of the six detrital zircon facies identified in basal Sauk sandstones, five by bimodal detrital zircon populations dominated by Archean and Paleopro- (A, B, D, E, and F) are found in samples from both the Cassiar-Antler and terozoic ages. To the south, Archean zircons become scarce and populations North American platforms, while only one (facies C; Fig. 11) is unique to are dominated by younger Paleoproterozoic zircons derived from the Yavapai basal Sauk sequence rocks of the Antler platform, with no North American and Mazatzal provinces and early Mesoproterozoic zircons derived from the platform equivalent. As discussed previously, basal Sauk sandstones with A-type granites that intrude those provinces. Farther south, Grenville-aged facies C detrital zircon populations likely derive from recycling of the older detritus becomes more prominent, with local Cambrian plutonism providing

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Figure 11. Comparison of detrital zircon populations along four roughly east-west transects from the Cassiar-Antler platform into the North American platform; locations of the sections are shown in the map. The red thrust symbol marks the approximate location of the hypothesized suture (modified after Hildebrand, 2009). Black lines are basal Sauk sequence sandstones; grey lines are older sandstones. Details for all sample locations are given in Table 1. n is the number of measurements in each curve. Sample numbers and formations are given using symbols from Figure 1. Prominent modes are given in Ma; a line at 1.8 Ga is provided as a visual reference for the age of the Paleoproterozoic population.

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Carlson, M.P., 1999, Transcontinental Arch—A pattern formed by rejuvenation of local features useful constraints on sediment delivery pathways around the southern limit across central North America: Tectonophysics, v. 305, p. 225–233, https://doi.org/10.1016/ of the Transcontinental Arch. The east-west continuity of detrital zircon facies S0040-1951(99)00005-0. between rocks of the Cassier-Antler and North American platforms at similar Cawood, P.A., Hawkesworth, C.J., and Dhuime, B., 2012, Detrital zircon record and tectonic setting: Geology, v. 40, p. 875–878, https://doi.org/10.1130/G32945.1. latitudes suggests that no major orogen-parallel offset has occurred between Collerson, K.D., Van Schmus, R.W., Lewry, J.F., and Bickford, M.E., 1988, Buried Precambrian base- them. This observation supports general accretionary models for the North ment in south-central Saskatchewan: Provisional results from Sm-Nd model ages and U-Pb American cordillera and argues against the ribbon continent models. zircon geochronology, in Macdonald, R., ed., Summary of Investigations 1988, Saskatchewan Geological Survey: Saskatchewan Department of Energy and Mines Miscellaneous Report 88 -4, p. 142–150. Colpron, M., Logan, J.M., and Mortensen, J.K., 2002, U-Pb zircon age constraint for late Neopro- ACKNOWLEDGMENTS terozoic rifting and initiation of the lower Paleozoic passive margin of western Laurentia: Canadian Journal of Earth Sciences, v. 39, p. 133–143, https://doi.org/10.1139/e01-069. Measurements were conducted at the Centre for Pure and Applied Tectonics and Thermochronol- Corsetti, F.A., and Hagadom, J.W., 2000, Precambrian-Cambrian transition: Death Valley, United ogy (CPATT) at the University of Calgary, a new LA-ICP-MS thermochronology and geochronology States: Geology, v. 28, p. 299–302, https://doi.org/10.1130/0091-7613(2000)28<299:PTDVUS laboratory funded by the Canadian Foundation for Innovation (CFI project 30696). Charles Hender- >2.0.CO;2. son is thanked for his review of an early version of this manuscript. This manuscript and the inter- DeCelles, P.G., 2004, Late Jurassic to Eocene evolution of the Cordilleran thrust belt and foreland pretations and ideas herein benefitted from discussions with Thomas Hadlari, Margo McMechan, basin system, western U.S.A.: American Journal of Science, v. 304, p. 105–168, https://doi.org/ and Robert Hildebrand. Michael McEchearn and Ewan Webster assisted with the field aspects of 10.2475/ajs.304.2.105. this project. Reviews by Thomas Hadlari, Christopher Spencer, and three anonymous reviewers Dehler, C.M., Fanning, C.M., Link, P.K., Kingsbury, E.M., and Rybczynski, D., 2010, Maximum dep- greatly improved the manuscript. ositional age and provenance of the Uinta Mountain Group and Big Cottonwood Formation, northern Utah: Paleogeography of rifting western Laurentia: Geological Society of America Bulletin, v. 122, p. 1686–1699, https://doi.org/10.1130/B30094.1. Dercourt, J., 1972, The Canadian Cordillera, the Hellenides, and the sea-floor spreading theory: REFERENCES CITED Canadian Journal of Earth Sciences, v. 9, p. 709–743, https://doi.org/10.1139/e72-060. 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