Lemieux et al 2011 devonian d zr peel

Detrital zircon geochronology and provenance ofDevono-Mississippian strata in the northernCanadian Cordilleran miogeocline1,2

Yvon Lemieux, Thomas Hadlari, and Antonio Simonetti

Abstract: U–Pb ages have been determined on detrital zircons from the Upper Devonian Imperial Formation and UpperDevonian – Lower Carboniferous Tuttle Formation of the northern Canadian Cordilleran miogeocline using laser ablation –multicollector – inductively coupled plasma – mass spectrometry. The results provide insights into mid-Paleozoic sedimentdispersal in, and paleogeography of, the northern Canadian Cordillera. The Imperial Formation yielded a wide range of de-trital zircon dates; one sample yielded dominant peaks at 1130, 1660, and 1860 Ma, with smaller mid-Paleozoic(*430 Ma), Neoproterozoic, and Archean populations. The easternmost Imperial Formation sample yielded predominantlylate Neoproterozoic – Cambrian zircons between 500 and 700 Ma, with lesser Mesoproterozoic and older populations. Theage spectra suggest that the samples were largely derived from an extensive region of northwestern Laurentia, including theCanadian Shield, igneous and sedimentary provinces of Canada’s Arctic Islands, and possibly the northern Yukon. The pres-ence of late Neoproterozoic – Cambrian zircon, absent from the Laurentian magmatic record, indicate that a number ofgrains were likely derived from an exotic source region, possibly including Baltica, Siberia, or Arctic Alaska – Chukotka. Incontrast, zircon grains from the Tuttle Formation show a well-defined middle Paleoproterozoic population with dominantrelative probability peaks between 1850 and 1950 Ma. Additional populations in the Tuttle Formation are mid-Paleozoic(*430 Ma), Mesoproterozoic (1000–1600 Ma), and earlier Paleoproterozoic and Archean ages (>2000 Ma). These data lendsupport to the hypothesis that the influx of sediments of northerly derivation that supplied the northern miogeocline in LateDevonian time underwent an abrupt shift to a source of predominantly Laurentian affinity by the Mississippian.

Resume : Des ages U–Pb ont ete determines par spectrometrie de masse a plasma inductif avec multicollecteur apres abla-tion au laser sur des zircons detritiques provenant de la Formation Imperial (Devonien superieur) et de la Formation Tuttle(Devonien – Carbonifere inferieur) du miogeoclinal de la Cordillere canadienne septentrionale. Les resultats fournissent desapercus de la dispersion des sediments au Paleozoıque moyen et de la paleogeographie de la Cordillere canadienne septen-trionale. La Formation Imperial a donne une grande plage de dates sur des zircons detritiques; un echantillon a donne despics dominants a 1130, 1660 et 1860 Ma ainsi que des populations moindres datant du Paleozoıque moyen (*430 Ma), duNeoproterozoıque et de l’Archeen. L’echantillon le plus a l’est de la Formation Imperial a donne des zircons datant surtoutdu Neoproterozoıque tardif – Cambrien, soit entre 500 et 700 Ma, avec des populations moindres datant du Mesoprotero-zoıque et plus anciennes. Les plages d’ages suggerent que les echantillons proviennent surtout d’une region extensive dansle nord-ouest de la Laurentie, incluant le Bouclier canadien, les provinces ignees et sedimentaires des ıles de l’Arctique ca-nadien et possiblement du nord du Yukon. La presence de zircons datant du Neoproterozoıque tardif – Cambrien, lesquelssont absents des donnees magmatiques laurentiennes, indique qu’un certain nombre de grains proviennent sans doute d’uneregion source exotique, possiblement de Baltica, de la Siberie ou du terrane Arctic Alaska – Chukotka. Cependant, les zir-cons provenant de la Formation Tuttle montrent une population bien definie du Paleoproterozoıque moyen avec des pics deprobabilite relative entre 1850 et 1950 Ma. D’autres populations dans la Formation Tuttle datent du Paleozoıque moyen(*430 Ma), du Mesoproterozoıque (1000–1600 Ma) ainsi que du Paleoproterozoıque inferieur et de l’Archeen (>2000 Ma).Ces donnees supportent l’hypothese que l’influx de sediments provenant du Nord qui a fourni le miogeoclinal septentrionalau Devonien tardif a subi un changement abrupt vers une source d’affinite surtout laurentienne vers le Mississippien.

[Traduit par la Redaction]

Received 23 November 2009. Accepted 26 May 2010. Published on the NRC Research Press Web site at cjes.nrc.ca on 9 February 2011.

Paper handled by Associate Editor W.J. Davis.

Y. Lemieux and T. Hadlari.3,4 Northwest Territories Geoscience Office, Box 1500, 4601-B, 52 Avenue, Yellowknife, NT X1A 2R3,Canada.A. Simonetti.5 Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G2E3, Canada.

1This article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.2Northwest Territories Geoscience Office Contribution 0047. Geological Survey of Canada Contribution 20100432.3Corresponding author (e-mail: [email protected]).4Present address: Geological Survey of Canada, 3303, 33rd St. NW, Calgary, AB T2L 2A7, Canada.5Present address: 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556.

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Can. J. Earth Sci. 48: 515–541 (2011) doi:10.1139/E10-056 Published by NRC Research Press

IntroductionDespite an increasing number of U–Pb geochronology and

Nd isotopic studies that provided new perspectives on re-gional patterns of sediment dispersal in northwestern Canadaand adjacent Arctic region in Paleozoic time (e.g., McNicollet al. 1995; Garzione et al. 1997; Gehrels et al. 1999; Patch-ett et al. 1999; Miller et al. 2006), the tectonic setting andpaleogeography during deposition of the Devono-Mississip-pian succession in the northern Canadian Cordilleran mio-geocline is not well understood.

Prior to the late Devonian, the northern Cordilleran mar-gin was dominated by an extensive shallow-water carbonateplatform thickening markedly westward toward a fine-grained basinal succession (e.g., Fritz et al. 1991). The plat-form was flanked to the east by the Laurentian PrecambrianShield, which provided most of the sediment for the clasticdeposits (Gordey et al. 1991). By the late Devonian, an in-flux of fine siliciclastic sediment blanketed the northernshelf and platform, marking a profound change in depositio-nal regime and tectonic setting along the Cordilleran margin(Morrow and Geldsetzer 1988). In northern Yukon andNorthwest Territories, the Middle Devonian to Early Car-boniferous Imperial Assemblage, including the Hare Indian,Canol, Imperial, Tuttle, and Ford Lake formations, was in-terpreted by Gordey et al. (1991) to have been derived froman uplifted region in northern Yukon. On the basis of Ndisotopic constraints, Garzione et al. (1997) and Patchett etal. (1999) argued that the Imperial Assemblage was likelyderived from Ordovician to Early Carboniferous orogenicsystems in Greenland and the Canadian Arctic, as proposedby Embry and Klovan (1976). More recently, detailed sedi-mentology of the Upper Devonian Imperial Formation andTuttle Formation (Hadlari et al. 2009) indicated derivationfrom a northeastern and eastern source region.

Paleozoic sediment dispersal in the northern Cordilleracan be better constrained with detrital zircon geochronologydata. Few U–Pb detrital zircon studies have been carried outin strata of the miogeocline in the northern Canadian Cordil-lera (e.g., Beranek et al. 2010). In this paper, we presentnew U–Pb detrital zircon dates obtained using laser ablation– multicollector – inductively coupled plasma – mass spec-trometry (LA–MC–ICP–MS) from the Upper Devonian Im-perial Formation and Upper Devonian – LowerCarboniferous Tuttle Formation exposed in the northernMackenzie Mountains (Figs. 1, 2). The purpose of the studyis to constrain the provenance of sandstones within thesetwo units to better understand regional patterns of mid-Pale-ozoic sediment dispersal in the northern Cordillera and todraw conclusions regarding paleogeography of northernLaurentia. As our data indicate, the zircons from the Impe-rial and Tuttle formations were likely derived from an ex-tensive region of northern Laurentia, including thenorthwestern Canadian Shield, provinces of Canada’s ArcticIslands, and Greenland.

Geological settingThe study area lies along the northern margin of the

Mackenzie Mountains and encompasses the southern PeelPlateau and Plain (Peel Region) of the northern InteriorPlains (Figs. 2); it occupies a region where imbricated and

folded miogeoclinal strata are exposed at the mountain front.The area preserves a relatively complete Cambrian to Dev-onian, rift to post-rift passive-margin succession that lieswith a pronounced unconformity on a thick succession ofProterozoic sedimentary rock (Fig. 3; Aitken et al. 1982). Awedge of Cretaceous siliciclastic strata, interpreted to havebeen deposited in a foreland basin setting, overlies the Pale-ozoic succession.

In Cambrian to Middle Devonian time, the northern Cana-dian Cordilleran miogeocline was a continental marginmarked by deposition of extensive carbonate platform andminor associated siliciclastic rocks (Mackenzie Platform;Fritz et al. 1991), and, to the west, deeper water siliciclasticand minor carbonate succession (Fig. 3; Pugh 1983). Detritalzircon ages from Cambrian sandstone in east-central Alaskasuggest provenance largely from regions of the CanadianShield (Gehrels et al. 1999).

In the late Devonian, passive-margin sedimentation wasinterrupted by a major change in tectono-sedimentologicalelements with uplift of clastic sourcelands north and west ofthe platform and influx of thick wedges of coarse and fineclastic sediments (Pugh 1983; Gordey et al. 1991). TheUpper Devonian Imperial Formation (Bassett 1961), mark-ing the transition from carbonate to sand-grade siliciclasticdeposition in the northern miogeocline (e.g., Gordey et al.1991), includes a thick sequence of marine shale, siltstone,and very fine- to fine-grained sandstone that overlies blacksiliceous shale of the Canol Formation. Within the studyarea, the Imperial Formation has been interpreted as Fras-nian–Famennian shelf sandstones and basinal turbidites withan eastward or northeastward sediment source inferred fromoutcrop studies (Braman and Hills 1992), and as a west- tosouthwestward-prograding submarine slope and fan complex(Hadlari et al. 2009). To the north and west, the ImperialFormation is composed of turbidites interpreted to havebeen derived largely from northern source regions (Gordeyet al. 1991; Braman and Hills 1992). Seventeen single zircondates from the Imperial Formation in northwestern Yukon(C. Garzione, G. Ross, J. Patchett, and G. Gehrels unpub-lished data, discussed in Gehrels et al. 1999) indicated adominance of >1.8 Ga detritus, consistent with derivationfrom Canadian Shield sources, with a subordinate populationof mid-Paleozoic (400–450 Ma) grains. Single zircon grainsfrom a Late Devonian sandstone-bearing unit in east-centralAlaska yielded chiefly 430 Ma, Paleoproterozoic (>1.8 Ga),and Archean grains, consistent with an influx of detritus, inpart, from Laurentian source regions (Gehrels et al. 1999).Similar results have been reported from Devonian to Car-boniferous sandstones of northeastern Yukon Territory (Be-ranek et al. 2010).

East of Arctic Red River (see Fig. 2 for location), Impe-rial Formation is unconformably overlain by wedge of Cre-taceous clastic sediments deposited in a foreland basinsetting (Aitken et al. 1982); west of Arctic Red River, how-ever, the Imperial Formation is conformably overlain by theUpper Devonian – Lower Carboniferous Tuttle Formation, athick succession of alternating conglomerate, coarse- to fine-grained sandstone, siltstone, and shale. The contact with theImperial Formation is interpreted as a facies boundary and,therefore, is diachronous (Pugh 1983). Hills and Braman(1978) and Braman and Hills (1992) interpreted the Tuttle

516 Can. J. Earth Sci. Vol. 48, 2011

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Formation as a southward-advancing turbidite succession. Incontrast, Pugh (1983) viewed the unit as a deltaic depositio-nal system and interpreted the shale-out to the west as indi-cating southwest-prograding deposition despite a progressivesouthward decrease in grain size and trend to better sorting.By the mid-Mississippian, marine clastic and carbonate dep-osition with sediment derivation from the craton to the eastwas re-established (Gordey et al. 1991).

The sub-Cretaceous unconformity marks a hiatus in thesedimentary record as Late Carboniferous to Jurassic strataare absent from the northern Interior Plains. The end of con-tinental margin sedimentation and beginning of widespreadcompressional deformation in the northern Cordillera inMesozoic time (e.g., Berman et al. 2007) influenced the de-velopment of foreland basins adjacent to the mountain front(Dixon 1999). Clastic sedimentation in the northern Interior

Fig. 1. Tectonic assemblage map of Yukon Territory, Northwest Territories and Nunavut showing location of study area and Fig. 2. Geol-ogy after Wheeler et al. (1996), paleocurrent data from Embry and Klovan (1976) and Hadlari et al. (2009).

Lemieux et al. 517


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Plains in the Late Cretaceous was controlled largely by, andderived from, the active Cordillera to the south and west(Dixon 1999).

U–Pb geochronology

Sample description and analytical proceduresThis study presents U–Pb geochronological results for

four samples from the Devono-Mississippian clastic succes-sion in the Peel Region, two from the Imperial Formation(samples 07TH33B and 07WZ020A), and two from the Tut-tle Formation (samples 07WZ019A and 06YHL046B); theirgeographic locations are shown in Fig. 2 and given inTable 1.

Sample 07TH33B was collected at the type section of Im-perial Formation (Fig. 2). Located near the eastern erosionaledge of Imperial Formation, the type section preserves theoldest strata of Imperial Formation, which were depositedas a shallow shelf-like accumulation of sediment that pro-graded southwestward into a generally westward-deepeningbasin (Hadlari et al. 2009). The sampled interval consists offine-grained cross-stratified sandstone from the locally de-veloped shallow-marine facies.

West of Imperial River, the Imperial Formation is inter-preted as a succession of submarine fan and slope sand-stones and shales exceeding 500 m in thickness that, basedupon paleocurrent and seismic data, are interpreted to havebeen deposited by a system that prograded in a west-south-west direction (Hadlari et al. 2009). Tuttle Formation is gen-erally Famennian to Tournasian in age (Allen et al. 2009),overlies the Imperial Formation, is partly defined by me-dium sand and coarser grain sizes, and represents a rejuve-nation of sand-grade siliciclastic input to the basin from thenortheast (Hadlari et al. 2009). Based upon the depositionalsystem, the three remaining samples are significantlyyounger than 07TH33B because they are located over100 km west of Imperial River. Considering their mutualproximity, we have placed the three western samples in or-der by the stratigraphic level that was sampled within thecombined Imperial–Tuttle formation section. Sample07WZ020A, a massive fine-grained sandstone, was collecteda few metres above the Canol–Imperial contact along a trib-utary of the Snake River near the western edge of the studyarea. From the middle part of the section, sample06YHL046B was collected from a *150 m high bluff ofconspicuously hard and massive, medium- to coarse-grained,quartz-rich sandstone sharply overlying shale and siltstonewest of Cranswick River (Fig. 4). Although the bluff wasmapped as Imperial Formation by Norris (1982), the grainsize is clearly atypical of Imperial Formation, and is inter-preted here as part of Tuttle Formation. Sample 07WZ019Ais conglomerate of Tuttle Formation from the top of the Im-perial–Tuttle section at Flyaway Creek; the section exposesa thin interval, *50 m thick, of sandstone and conglomerateoverlying *600 m in thickness of Imperial Formation (Ha-dlari et al. 2009). The entire sample of quartz clast conglom-erate with sandstone matrix was crushed for analysis.

Each sample yielded euhedral to anhedral, colourless topink or yellow, generally well-rounded zircons consistentwith a detrital origin. Samples from the Tuttle Formationwere sufficiently coarse grained to yield abundant zircons

large enough (i.e., > 40 mm across, see as follows) for laserablation analyses. In contrast, the much finer grained Impe-rial samples yielded a smaller fraction of zircons that weresufficiently large for analysis. Selected grains were, asmuch as possible, free of fractures, inclusions, and altera-tion. U–Pb geochronology of zircons was conducted byLA–MC–ICP–MS at the Radiogenic Isotope Facility at theUniversity of Alberta, Edmonton, Alberta, using analyticalprocedures described by Simonetti et al. (2005). The analy-ses involved ablation of zircons using a 40 mm diameter la-ser spot size for 30 s. A ‘‘standard-sample-standard’’ methodwas used to correct instrumental drift during a single laserablation session and involved analysis of an internal stand-ard after every 12 unknown grains; this protocol was devel-oped for provenance studies focusing on the dating of alarge number of detrital zircon grains (Simonetti et al.2005) The collector configuration allows for the simultane-ous measurement of ion signals ranging in mass from 238Uto 203Tl. Periodically, a 30 s blank measurement was per-formed, which included correction for the 204Hg contribu-tion; ion-counter bias was also determined using a mixedsolution of Pb and Tl. Common Pb correction was appliedusing an initial Pb composition taken from Stacey andKramers (1975).

Results of U–Pb analysisThe results are presented in Table 1 (with uncertainties at

the 2s level) and shown in relative age–probability diagrams(from Ludwig 2003) in Fig. 5. The diagrams present the sumof all ages from a sample as a normal distribution based onthe age and uncertainty of each analysis, the areas undereach curve are equal. Interpretations for <1000 Ma grainsare based on 206Pb/238U ages, which yield more precise re-sults given the low concentration of 207Pb in younger zir-cons. For grains >1000 Ma, analyses are based on 207Pb/206Pb ages. To reduce the effect of discordance, possibly re-sulting from isotopic disturbance and (or) inheritance, analy-ses that are >5% discordant or >5% reverse discordant(italics in Table 1) have been excluded from further consid-eration.

A total of 67 zircons were analyzed from sample07TH33B (Imperial Formation), of which 54 were consid-ered (Fig. 5; Table 1). A significant number of zirconsyielded age clusters between 380 and 711 Ma (n = 26),with peaks evident at 390, 555, and 670 Ma. Twenty-fivezircons yielded Proterozoic dates, with the most dominantpeaks at 1100, 1350, 1670, and 1950 Ma; only one zirconfalls in the interval 2100–2500 Ma. Three Archean zirconswere documented (i.e., 2625, 2796, and 2820 Ma).

Ninety-one zircons extracted from the westernmost sam-ple of the Imperial Formation (07WZ020A) were analyzed,of which 61 are within 5% of the concordia. This samplehas a dominant zircon age population (n = 46) between*1000 and 2100 Ma, with major peaks at 1130, 1660, and1860 Ma, and subordinate age groups at 1300–1550, 1730–1800, 1900–2100 Ma. The sample also includes (i) fourlower Paleozoic zircons at 424, 432, 438, and 505 Ma; (ii)four Neoproterozoic grains at 570, 597, 645, and 855 Ma;and (iii) seven Archean zircons between 2614 and 2806 Ma.There is a gap between 2100 and 2600 Ma.

Ninety-one zircon were analyzed from sample



06YHL046B (Tuttle Formation); 18 zircon have not beenconsidered further. A 440 Ma Silurian-age peak is evident,represented by seven grains between 428 and 444 Ma. Thesample yielded 45 grains between *1800 and 2800 Ma,with dominant age peaks at 1860 and 2780 Ma, and subordi-nate age groups between *2000 and 2700 Ma. Twenty zir-cons fall in the intervals 1038–1366 Ma (n = 13), 1494–

1512 Ma (n = 2), and 1597–1731 Ma (n = 5). One grainyielded a Neoproterozoic date (940 Ma).

A total of 112 zircons were analyzed from sample07WZ019A (Tuttle Formation), of which 99 were consid-ered. A 1937 Ma Paleoproterozoic age peak is evident inthe zircon population, with 50 grains falling in the interval1792–2000 Ma; a subordinate age cluster occurs at 430 Ma,

Fig. 4. (a) Field photograph showing the contact between the Imperial Formation and overlying Tuttle Formation in the Cranswick Riverarea. The bluff (in the middle ground) was mapped as Imperial Formation by Norris (1982). View to northeast; field of view in middleground is *4 km. (b) Close-up of approximate contact (dashed line) between the Imperial and Tuttle formations. Geologist for scale. SeeFig. 2 for location of photographs.

Lemieux et al. 521


Table 1. U–Pb data of detrital zircons.

Isotopic ratios Apparent ages (Ma)

Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

Sample 07TH33B (UTM ZONE 9N, N7221831, E553690)1 217352 Infinite 0.4578 0.012 0.0607 0.002 0.96 380 15 383 10 368 25 –3.12 266037 29559.7 0.4382 0.008 0.0585 0.001 0.92 366 13 369 7 370 32 0.83 97534 Infinite 0.4601 0.006 0.0600 0.001 0.93 376 12 384 5 393 27 4.34 141527 Infinite 0.4855 0.010 0.0629 0.001 0.91 393 14 402 8 409 34 3.85 105463 Infinite 0.4873 0.009 0.0629 0.001 0.90 393 13 403 7 409 34 3.86 116583 Infinite 0.4960 0.012 0.0644 0.001 0.95 402 15 409 10 413 27 2.67 87935 Infinite 0.4998 0.014 0.0649 0.002 0.91 405 15 412 11 416 37 2.68 57814 Infinite 0.5677 0.013 0.0724 0.002 0.94 451 16 457 10 422 29 -6.89 57549 Infinite 0.5629 0.011 0.0716 0.001 0.93 446 15 453 9 425 29 –4.810 191304 Infinite 0.5751 0.009 0.0734 0.001 0.95 457 15 461 7 451 23 –1.211 204407 Infinite 0.4615 0.013 0.0582 0.002 0.95 365 15 385 11 476 29 23.412 325769 Infinite 0.6521 0.015 0.0809 0.002 0.95 501 19 510 12 518 26 3.313 61741 Infinite 0.7202 0.019 0.0883 0.002 0.96 545 22 551 15 521 26 –4.614 193746 Infinite 0.7096 0.016 0.0863 0.002 0.94 533 20 544 12 556 29 4.015 109660 Infinite 0.7400 0.016 0.0897 0.002 0.96 554 20 562 12 559 24 1.016 202468 Infinite 0.7514 0.022 0.0907 0.003 0.97 560 24 569 17 564 24 0.817 340492 Infinite 0.7230 0.014 0.0878 0.002 0.93 542 19 552 11 567 28 4.318 141712 4571.37 0.6721 0.039 0.0810 0.004 0.92 502 30 522 30 575 57 12.719 134699 33674.67 0.7638 0.021 0.0917 0.002 0.94 565 22 576 16 584 29 3.320 296319 Infinite 0.7744 0.014 0.0931 0.002 0.95 574 20 582 10 593 24 3.221 229189 Infinite 0.7777 0.017 0.0931 0.002 0.95 574 21 584 13 596 25 3.622 278753 25341.2 0.6959 0.020 0.0830 0.002 0.93 514 20 536 15 605 32 15.023 417489 Infinite 0.7199 0.016 0.0863 0.002 0.96 534 20 551 12 606 23 11.924 365918 Infinite 0.9035 0.017 0.1043 0.002 0.94 640 22 654 12 670 25 4.525 203291 Infinite 0.8012 0.020 0.0918 0.002 0.93 566 21 598 15 670 30 15.526 100302 Infinite 0.9362 0.022 0.1071 0.002 0.94 656 24 671 16 675 29 2.827 273595 Infinite 0.9270 0.025 0.1091 0.003 0.96 667 27 666 18 677 23 1.428 188263 Infinite 0.9401 0.020 0.1078 0.002 0.95 660 24 673 14 679 25 2.829 227461 10831.45 0.9981 0.052 0.1146 0.005 0.91 699 39 703 37 684 54 –2.230 278435 Infinite 0.9515 0.017 0.1096 0.002 0.96 670 23 679 12 698 22 4.031 312369 Infinite 0.8629 0.033 0.0991 0.004 0.97 609 30 632 24 702 24 13.232 165271 Infinite 0.9856 0.026 0.1107 0.003 0.96 677 27 696 18 707 24 4.333 217427 Infinite 1.0312 0.015 0.1166 0.001 0.91 711 23 720 11 717 29 0.934 227825 28478.1 0.9579 0.023 0.1031 0.002 0.94 633 24 682 16 819 28 22.835 71442 Infinite 1.6142 0.031 0.1607 0.003 0.93 961 33 976 19 953 27 –0.836 102579 Infinite 1.9582 0.060 0.1866 0.006 0.97 1103 47 1101 34 1059 21 –4.237 725341 Infinite 1.4684 0.041 0.1403 0.004 0.93 846 33 917 26 1084 31 21.938 259436 Infinite 1.9815 0.037 0.1867 0.003 0.95 1103 39 1109 21 1095 22 –0.839 198957 Infinite 1.9575 0.051 0.1833 0.005 0.96 1085 43 1101 28 1097 21 1.1

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Table 1 (continued).


Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

40 802664 21693.62 1.9697 0.045 0.1865 0.004 0.93 1102 40 1105 25 1106 28 0.341 224638 1936.534 1.8174 0.064 0.1809 0.006 0.92 1072 47 1052 37 1118 36 4.142 1011788 2007.516 2.4696 0.224 0.2155 0.019 0.98 1258 119 1263 114 1272 33 1.143 243064 Infinite 2.1622 0.178 0.1784 0.014 0.97 1058 91 1169 96 1330 38 20.444 607082 530.203 2.5457 0.133 0.2178 0.010 0.91 1270 71 1285 67 1333 49 4.745 522574 Infinite 2.6736 0.083 0.2244 0.007 0.97 1305 56 1321 41 1341 20 2.646 1073922 Infinite 2.6708 0.062 0.2241 0.005 0.96 1304 49 1320 31 1345 20 3.147 114935 Infinite 2.8172 0.049 0.2294 0.004 0.93 1332 45 1360 24 1374 25 3.148 385586 16764.6 2.7961 0.049 0.2198 0.003 0.91 1281 42 1355 24 1452 27 11.849 1398896 Infinite 3.3621 0.044 0.2658 0.003 0.95 1519 50 1496 20 1487 19 –2.150 1668858 Infinite 2.6855 0.035 0.1994 0.002 0.93 1172 38 1324 17 1555 22 24.651 505990 Infinite 4.3155 0.105 0.3056 0.007 0.97 1719 66 1696 41 1659 19 –3.652 1627787 Infinite 3.9893 0.076 0.2831 0.005 0.96 1607 57 1632 31 1670 19 3.853 630839 Infinite 4.2327 0.086 0.2952 0.006 0.96 1668 60 1680 34 1688 19 1.254 488924 Infinite 4.6379 0.339 0.3078 0.021 0.94 1730 129 1756 128 1727 51 –0.255 840928 Infinite 4.6572 0.069 0.3100 0.005 0.95 1741 58 1760 26 1779 19 2.156 200124 939.5515 5.5286 0.415 0.3341 0.025 0.97 1858 148 1905 143 1893 33 1.857 481859 Infinite 5.7437 0.120 0.3505 0.007 0.96 1937 71 1938 40 1929 19 –0.458 673729 2029.306 5.7164 0.107 0.3497 0.006 0.95 1933 68 1934 36 1935 20 0.159 933238 Infinite 5.6258 0.080 0.3369 0.005 0.95 1872 62 1920 27 1968 18 4.960 966251 Infinite 6.2317 0.095 0.3725 0.006 0.95 2041 69 2009 31 1976 18 –3.361 1716228 17693.07 6.2476 0.108 0.3704 0.006 0.94 2031 69 2011 35 2011 22 –1.062 883413 Infinite 5.9951 0.114 0.3495 0.007 0.96 1932 68 1975 37 2021 18 4.463 322605 1097.296 7.6982 0.196 0.3990 0.010 0.95 2164 83 2196 56 2206 22 1.964 1093494 Infinite 11.6411 0.170 0.4771 0.007 0.95 2515 84 2576 38 2625 17 4.265 1548221 30964.42 14.8244 0.277 0.5507 0.010 0.96 2828 100 2804 52 2796 17 –1.166 390767 Infinite 15.4936 0.348 0.5625 0.013 0.96 2877 108 2846 64 2820 17 –2.067 3034842 35704 10.4927 0.353 0.3826 0.013 0.97 2089 94 2479 83 2832 17 26.2

Sample 07WZ020A (UTM Zone 9N, N7277599, E308503)1 126733 Infinite 0.5336 0.015 0.0693 0.002 0.96 432 18 434 12 420 25 –2.82 340726 Infinite 0.5227 0.008 0.0679 0.001 0.95 424 14 427 6 441 23 3.93 259160 Infinite 0.5501 0.011 0.0703 0.001 0.96 438 16 445 9 454 24 3.64 297800 Infinite 0.4928 0.007 0.0623 0.001 0.94 390 13 407 6 483 24 19.35 699418 Infinite 0.4709 0.012 0.0584 0.001 0.94 366 14 392 10 516 30 29.16 357235 238.9533 0.6515 0.083 0.0815 0.010 0.97 505 64 509 65 525 70 3.87 371429 Infinite 0.5386 0.013 0.0664 0.002 0.94 414 16 437 10 529 28 21.78 256729 Infinite 0.7658 0.016 0.0925 0.002 0.96 570 21 577 12 582 24 1.99 109026 Infinite 0.8092 0.018 0.0970 0.002 0.94 597 22 602 13 587 28 –1.610 433467 Infinite 0.6441 0.012 0.0775 0.001 0.96 481 17 505 9 595 23 19.211 181581 Infinite 0.9039 0.011 0.1052 0.001 0.95 645 21 654 8 656 23 1.7

Lemieux

etal.

523

Publishedby

NR

CR

esearchPress



Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

12 1016871 3697.711 1.3405 0.048 0.1418 0.005 0.96 855 39 863 31 887 26 3.613 158487 Infinite 1.6375 0.030 0.1613 0.003 0.95 964 34 985 18 996 22 3.214 753417 39653.5 1.7187 0.044 0.1676 0.004 0.96 999 39 1016 26 1044 23 4.315 972131 Infinite 1.8740 0.032 0.1789 0.003 0.96 1061 37 1072 18 1091 20 2.716 555233 Infinite 1.8900 0.064 0.1790 0.006 0.96 1061 47 1078 36 1097 25 3.317 1298874 4071.706 1.8714 0.132 0.1781 0.012 0.94 1056 76 1071 75 1101 53 4.118 202173 Infinite 2.0020 0.037 0.1871 0.003 0.94 1106 38 1116 21 1115 24 0.819 334811 Infinite 2.0319 0.042 0.1902 0.004 0.96 1122 41 1126 23 1115 21 –0.620 85633 Infinite 2.0206 0.036 0.1856 0.003 0.93 1097 37 1122 20 1130 25 2.921 433460 Infinite 2.0282 0.043 0.1890 0.004 0.96 1116 41 1125 24 1134 21 1.622 135092 Infinite 2.0534 0.056 0.1873 0.005 0.95 1107 44 1133 31 1154 25 4.123 393360 19668 2.1728 0.042 0.1995 0.003 0.92 1173 40 1172 23 1161 28 –1.024 158101 Infinite 2.2812 0.022 0.2067 0.001 0.93 1211 37 1206 11 1166 24 –3.925 457060 Infinite 1.6001 0.087 0.1451 0.008 0.97 874 54 970 53 1168 27 25.226 1110968 Infinite 1.6735 0.014 0.1527 0.001 0.94 916 28 999 8 1185 21 22.727 1177595 Infinite 2.1699 0.054 0.1985 0.005 0.97 1167 45 1171 29 1185 20 1.528 260928 Infinite 2.2472 0.063 0.2032 0.006 0.96 1192 49 1196 33 1186 22 –0.529 1078929 Infinite 2.3740 0.104 0.2117 0.009 0.97 1238 64 1235 54 1228 27 –0.830 166663 Infinite 2.3208 0.038 0.2022 0.003 0.95 1187 40 1219 20 1237 22 4.031 241826 Infinite 2.3165 0.064 0.2031 0.006 0.97 1192 48 1217 34 1243 21 4.132 393935 Infinite 2.2663 0.169 0.1945 0.013 0.92 1146 86 1202 90 1279 62 10.433 376764 1638.1 2.3487 0.076 0.1995 0.006 0.94 1173 50 1227 40 1304 30 10.034 395046 Infinite 2.5778 0.049 0.2173 0.004 0.94 1268 44 1294 25 1330 24 4.735 127330 Infinite 2.8597 0.065 0.2341 0.005 0.94 1356 50 1371 31 1366 24 0.836 236473 Infinite 2.5301 0.068 0.2065 0.005 0.96 1210 48 1281 34 1383 23 12.537 230817 Infinite 3.0753 0.044 0.2455 0.003 0.94 1415 47 1427 21 1402 21 –0.938 344399 Infinite 2.9715 0.050 0.2393 0.004 0.94 1383 47 1400 24 1411 22 2.039 441807 14726.89 3.2392 0.066 0.2544 0.004 0.91 1461 50 1467 30 1465 29 0.340 147977 Infinite 3.2981 0.066 0.2546 0.004 0.91 1462 50 1481 30 1474 28 0.841 669286 Infinite 3.3311 0.059 0.2585 0.005 0.95 1482 51 1488 26 1505 20 1.542 1296589 Infinite 3.4601 0.056 0.2636 0.004 0.96 1508 51 1518 24 1533 19 1.643 491753 1576.13 3.0343 0.278 0.2285 0.019 0.92 1327 118 1416 130 1548 73 14.344 131575 Infinite 4.1502 0.081 0.2915 0.006 0.95 1649 59 1664 32 1649 20 0.045 228486 337.4977 4.3403 0.233 0.3062 0.015 0.94 1722 101 1701 91 1653 38 –4.246 321559 Infinite 3.9912 0.130 0.2809 0.009 0.97 1596 71 1632 53 1660 19 3.947 1031062 Infinite 4.0686 0.081 0.2883 0.006 0.96 1633 59 1648 33 1664 19 1.948 528558 Infinite 4.3359 0.084 0.3050 0.006 0.96 1716 61 1700 33 1669 19 –2.849 590211 Infinite 3.0786 0.314 0.2133 0.022 0.99 1246 132 1427 146 1684 30 26.050 600365 Infinite 4.3516 0.116 0.3040 0.008 0.97 1711 69 1703 45 1701 19 –0.651 593925 Infinite 3.8213 0.069 0.2633 0.005 0.96 1507 53 1597 29 1710 19 11.9

524C

an.J.

Earth

Sci.

Vol.

48,2011

Publishedby

NR

CR

esearchPress



Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

52 728551 3223.678 4.3360 0.792 0.2943 0.053 0.99 1663 306 1700 310 1747 41 4.853 386808 16817.72 4.6421 0.095 0.3115 0.006 0.93 1748 62 1757 36 1748 24 0.054 624037 Infinite 4.6055 0.058 0.3077 0.004 0.95 1729 56 1750 22 1766 19 2.155 2324654 36899.3 4.0873 0.067 0.2723 0.004 0.95 1553 53 1652 27 1793 20 13.456 775421 2959.62 4.6605 0.150 0.3029 0.010 0.97 1706 75 1760 57 1825 20 6.557 456978 Infinite 4.2560 0.077 0.2740 0.005 0.96 1561 55 1685 31 1832 18 14.858 1267941 4103.37 3.6877 0.111 0.2384 0.007 0.95 1378 57 1569 47 1841 23 25.259 640904 Infinite 5.2003 0.111 0.3332 0.007 0.96 1854 68 1853 39 1848 18 –0.360 842510 Infinite 5.0816 0.084 0.3242 0.005 0.96 1810 62 1833 30 1854 18 2.461 449007 Infinite 5.2542 0.072 0.3332 0.005 0.95 1854 61 1861 26 1860 18 0.362 178341 Infinite 5.5673 0.102 0.3465 0.006 0.96 1918 67 1911 35 1870 19 –2.663 462742 Infinite 5.1635 0.121 0.3234 0.007 0.93 1807 66 1847 43 1875 26 3.764 2906290 10416.8 3.8769 0.187 0.2447 0.012 0.98 1411 80 1609 78 1892 18 25.465 878581 2670.46 4.1829 0.112 0.2585 0.006 0.93 1482 57 1671 45 1913 27 22.566 1133511 4048.255 5.6088 0.427 0.3423 0.023 0.90 1898 141 1917 146 1919 64 1.167 954093 Infinite 5.7962 0.078 0.3545 0.005 0.95 1956 64 1946 26 1931 18 –1.368 125954 Infinite 5.7371 0.118 0.3456 0.007 0.95 1914 68 1937 40 1934 21 1.069 276151 Infinite 5.8263 0.112 0.3524 0.007 0.96 1946 69 1950 37 1937 19 –0.570 661599 2584.37 4.8255 0.262 0.2931 0.014 0.91 1657 95 1789 97 1964 46 15.671 641871 Infinite 4.9901 0.230 0.2908 0.013 0.98 1646 90 1818 84 2005 19 17.972 628332 Infinite 6.2959 0.131 0.3659 0.008 0.96 2010 73 2018 42 2022 18 0.673 1454081 Infinite 5.8633 0.124 0.3421 0.007 0.96 1897 69 1956 41 2026 19 6.474 569035 Infinite 6.8134 0.148 0.3905 0.008 0.96 2125 79 2087 45 2041 18 –4.175 540218 13505.46 6.4420 0.141 0.3624 0.007 0.93 1994 72 2038 45 2072 24 3.876 2375359 Infinite 5.9257 0.104 0.3289 0.006 0.96 1833 64 1965 35 2117 18 13.477 763478 21813.7 7.6396 0.276 0.3721 0.013 0.97 2039 95 2190 79 2330 19 12.578 261215 4213.14 7.7344 0.778 0.3480 0.034 0.97 1925 197 2201 221 2442 42 21.279 1196610 10978.1 8.7709 0.263 0.3711 0.011 0.95 2035 85 2314 69 2576 21 21.080 1757086 Infinite 10.8700 0.261 0.4452 0.011 0.97 2374 91 2512 60 2607 17 9.081 593333 7510.545 12.4287 0.219 0.5121 0.007 0.90 2666 88 2637 46 2614 25 –2.082 662851 12747.13 12.1365 0.259 0.5015 0.010 0.95 2620 95 2615 56 2616 20 –0.283 416360 Infinite 12.9122 0.260 0.5159 0.010 0.96 2682 97 2673 54 2657 17 –0.984 252375 Infinite 13.1744 0.276 0.5171 0.011 0.96 2687 98 2692 56 2676 17 –0.485 208645 Infinite 11.6138 0.424 0.4548 0.016 0.97 2416 114 2574 94 2678 18 9.886 1148347 Infinite 7.6352 0.513 0.3010 0.020 0.99 1696 124 2189 147 2685 20 36.887 1089764 6263.011 13.2524 0.216 0.5143 0.008 0.96 2675 91 2698 44 2720 17 1.788 808986 3595.492 13.2011 0.297 0.5020 0.011 0.96 2622 98 2694 61 2743 18 4.489 2297798 10687.43 14.0788 0.229 0.5194 0.008 0.95 2697 92 2755 45 2806 17 3.990 2196173 Infinite 11.3921 0.208 0.4155 0.008 0.96 2240 78 2556 47 2827 17 20.791 2605994 Infinite 14.3094 0.171 0.5033 0.006 0.94 2628 84 2770 33 2886 18 8.9

Lemieux

etal.

525

Publishedby

NR

CR

esearchPress



Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

Sample 06YHL046B (UTM Zone 9N, N7272396, E343816)1 306103 21864.5 0.4471 0.011 0.0586 0.001 0.90 367 13 375 9 412 38 10.82 143296 Infinite 0.5353 0.013 0.0686 0.002 0.96 428 16 435 11 439 25 2.63 267931 Infinite 0.5415 0.008 0.0698 0.001 0.95 435 15 439 7 449 24 3.14 269063 Infinite 0.5246 0.009 0.0667 0.001 0.95 416 14 428 7 450 23 7.55 305544 25462.04 0.5388 0.011 0.0690 0.001 0.91 430 15 438 9 452 33 4.86 191005 Infinite 0.5527 0.010 0.0706 0.001 0.95 440 15 447 8 452 24 2.87 117843 Infinite 0.5512 0.010 0.0696 0.001 0.94 434 15 446 8 453 27 4.38 87963 Infinite 0.5519 0.008 0.0697 0.001 0.94 435 14 446 6 457 24 4.99 273721 Infinite 0.5580 0.010 0.0712 0.001 0.94 444 15 450 8 461 27 3.810 244012 Infinite 0.5268 0.010 0.0673 0.001 0.96 420 15 430 8 464 23 9.411 157050 6828.25 0.5478 0.008 0.0693 0.001 0.94 432 14 444 7 476 25 9.312 250449 Infinite 0.5569 0.012 0.0701 0.001 0.96 437 16 450 9 488 23 10.513 90322 Infinite 0.5830 0.009 0.0726 0.001 0.94 452 15 466 8 488 26 7.414 75488 Infinite 0.5878 0.009 0.0735 0.001 0.93 457 15 469 7 489 27 6.515 258727 Infinite 0.5517 0.014 0.0694 0.002 0.94 433 17 446 11 489 29 11.616 540430 24565 0.4523 0.009 0.0569 0.001 0.91 357 12 379 8 505 33 29.317 667919 Infinite 0.5657 0.017 0.0701 0.002 0.97 437 19 455 14 514 23 15.018 61977 Infinite 0.5407 0.008 0.0656 0.001 0.91 410 13 439 6 553 30 25.919 667782 897.556 1.2921 0.107 0.1382 0.011 0.97 835 72 842 70 946 40 11.720 554178 Infinite 1.5739 0.027 0.1571 0.003 0.96 940 32 960 16 987 21 4.721 1153240 31168.66 1.7696 0.026 0.1748 0.002 0.93 1038 34 1034 15 1045 24 0.722 53008 Infinite 1.9203 0.040 0.1822 0.004 0.95 1079 39 1088 23 1067 24 –1.223 827576 Infinite 1.9780 0.036 0.1875 0.003 0.96 1108 39 1108 20 1106 20 –0.224 48901 Infinite 2.1117 0.041 0.1952 0.004 0.94 1149 40 1153 23 1106 25 –3.925 276073 21236.4 1.8961 0.045 0.1767 0.004 0.93 1049 39 1080 26 1121 28 6.426 493272 Infinite 2.0163 0.038 0.1879 0.003 0.96 1110 39 1121 21 1138 21 2.427 385501 Infinite 2.1941 0.027 0.2006 0.002 0.95 1179 38 1179 15 1168 20 –0.928 391950 23055.89 2.1692 0.031 0.1970 0.002 0.92 1159 37 1171 17 1178 26 1.629 862341 16908.65 2.1118 0.040 0.1932 0.003 0.90 1139 38 1153 22 1181 30 3.630 329913 Infinite 2.2349 0.035 0.2006 0.003 0.95 1179 40 1192 19 1198 21 1.631 1542492 23022.28 2.2253 0.039 0.2020 0.003 0.93 1186 40 1189 21 1215 26 2.432 963785 19669.07 2.3924 0.042 0.2128 0.003 0.92 1244 41 1240 22 1243 27 –0.133 183429 Infinite 2.5816 0.025 0.2189 0.002 0.93 1276 40 1295 13 1302 22 2.034 805537 44752.06 2.6900 0.056 0.2234 0.005 0.96 1300 47 1326 28 1366 21 4.935 387711 Infinite 2.9232 0.053 0.2292 0.004 0.95 1330 46 1388 25 1468 20 9.436 184140 Infinite 3.3213 0.085 0.2559 0.006 0.93 1469 56 1486 38 1494 27 1.737 582297 Infinite 3.4728 0.046 0.2661 0.003 0.95 1521 50 1521 20 1512 20 –0.638 283821 Infinite 3.1801 0.065 0.2393 0.005 0.95 1383 50 1452 30 1525 21 9.339 98480 Infinite 3.8013 0.085 0.2746 0.006 0.95 1564 58 1593 35 1597 22 2.0

526C

an.J.

Earth

Sci.

Vol.

48,2011

Publishedby

NR

CR

esearchPress



Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

40 534604 Infinite 4.1880 0.070 0.2967 0.005 0.96 1675 57 1672 28 1650 19 –1.541 774143 3351.27 4.0421 0.059 0.2841 0.004 0.95 1612 54 1643 24 1679 19 4.042 271748 Infinite 4.2425 0.065 0.2948 0.004 0.95 1665 56 1682 26 1683 19 1.143 1049121 2149.839 4.4244 0.111 0.3093 0.008 0.96 1737 68 1717 43 1731 20 –0.444 1083148 16924.2 5.2375 0.104 0.3449 0.006 0.93 1910 67 1859 37 1807 24 -5.745 345860 Infinite 5.1241 0.078 0.3283 0.005 0.95 1830 61 1840 28 1837 19 0.446 87174 Infinite 5.0542 0.081 0.3175 0.005 0.94 1777 60 1828 29 1844 21 3.647 908076 Infinite 4.8886 0.093 0.3145 0.006 0.96 1763 62 1800 34 1848 19 4.648 160593 Infinite 5.1285 0.074 0.3232 0.005 0.95 1806 60 1841 27 1850 19 2.449 158205 Infinite 5.2452 0.144 0.3314 0.009 0.96 1845 74 1860 51 1855 21 0.550 217662 Infinite 5.1917 0.104 0.3269 0.006 0.96 1823 65 1851 37 1855 19 1.751 286154 Infinite 5.1969 0.118 0.3299 0.007 0.96 1838 69 1852 42 1858 19 1.152 908503 Infinite 5.1060 0.101 0.3245 0.006 0.96 1812 65 1837 36 1881 18 3.753 380632 Infinite 5.2275 0.092 0.3266 0.006 0.96 1822 63 1857 33 1882 18 3.254 547020 30390.02 5.4287 0.102 0.3397 0.006 0.95 1885 66 1889 36 1884 20 0.055 418269 Infinite 5.1815 0.097 0.3247 0.006 0.96 1813 64 1850 35 1886 19 3.956 547155 Infinite 5.3779 0.100 0.3358 0.006 0.96 1867 66 1881 35 1887 18 1.157 383706 Infinite 5.2456 0.106 0.3247 0.006 0.93 1813 64 1860 37 1899 24 4.558 823007 39190.81 5.5397 0.101 0.3455 0.006 0.95 1913 67 1907 35 1905 19 –0.459 227125 Infinite 5.7988 0.144 0.3527 0.009 0.97 1948 76 1946 48 1927 18 –1.160 415084 29648.85 5.5268 0.086 0.3346 0.005 0.95 1860 62 1905 30 1937 20 3.961 863196 Infinite 5.4964 0.070 0.3343 0.004 0.95 1859 61 1900 24 1943 18 4.362 568320 33430.6 5.6318 0.112 0.3386 0.006 0.95 1880 67 1921 38 1945 21 3.363 301989 Infinite 5.9578 0.228 0.3544 0.013 0.94 1956 91 1970 75 1981 30 1.364 1654832 7576.821 5.9299 0.170 0.3536 0.010 0.97 1952 81 1966 56 1989 18 1.965 134120 Infinite 6.3813 0.096 0.3660 0.005 0.95 2011 67 2030 30 2014 20 0.266 453298 11928.89 6.4458 0.162 0.3719 0.009 0.93 2038 77 2039 51 2028 26 –0.567 213612 Infinite 6.2961 0.073 0.3578 0.004 0.95 1972 63 2018 23 2042 18 3.468 340590 Infinite 6.9231 0.087 0.3816 0.005 0.95 2084 68 2102 27 2103 18 0.969 169094 Infinite 7.2633 0.110 0.3982 0.006 0.95 2161 72 2144 32 2108 18 –2.570 254999 1432.578 7.0782 0.224 0.3826 0.011 0.92 2088 86 2121 67 2132 31 2.171 288084 10288.7 7.7350 0.149 0.4007 0.006 0.91 2172 74 2201 42 2218 25 2.172 243308 Infinite 8.2218 0.117 0.4142 0.005 0.92 2234 72 2256 32 2259 22 1.173 713263 3114.684 7.9414 0.163 0.4009 0.007 0.91 2173 75 2224 46 2274 26 4.474 297895 Infinite 9.1338 0.172 0.4395 0.008 0.96 2349 83 2351 44 2334 18 –0.675 627237 36896.29 8.9794 0.166 0.4289 0.008 0.95 2301 81 2336 43 2369 18 2.976 588155 Infinite 9.5616 0.116 0.4463 0.005 0.95 2379 77 2393 29 2396 17 0.777 744871 Infinite 9.5427 0.175 0.4456 0.008 0.96 2376 83 2392 44 2404 17 1.278 688756 Infinite 10.3881 0.132 0.4568 0.006 0.95 2426 79 2470 31 2500 17 3.079 315734 Infinite 11.5054 0.202 0.4803 0.008 0.96 2529 88 2565 45 2578 17 1.9

Lemieux

etal.

527

Publishedby

NR

CR

esearchPress



Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

80 1051667 11308.25 11.6350 0.191 0.4878 0.007 0.93 2561 85 2575 42 2597 21 1.481 364050 18202.49 12.1285 0.247 0.4954 0.010 0.95 2594 93 2614 53 2625 19 1.282 669068 Infinite 12.8725 0.298 0.5058 0.012 0.96 2639 100 2670 62 2692 17 2.083 266386 15669.75 13.5506 0.232 0.5139 0.008 0.95 2673 91 2719 47 2732 0 2.184 1157294 23618.24 13.5933 0.215 0.5159 0.008 0.95 2682 90 2722 43 2763 17 2.985 726324 Infinite 5.7927 0.047 0.3488 0.003 0.95 1929 60 1945 16 2763 17 30.286 224223 Infinite 14.1944 0.243 0.5260 0.009 0.95 2725 94 2763 47 2766 17 1.587 1081708 Infinite 13.7710 0.280 0.5164 0.010 0.96 2684 97 2734 56 2772 16 3.288 291226 32358.45 15.2514 0.227 0.5606 0.008 0.95 2869 96 2831 42 2791 17 –2.889 784822 Infinite 14.0101 0.221 0.5179 0.008 0.95 2690 91 2750 43 2796 17 3.890 221940 11681.04 14.6259 0.276 0.5342 0.009 0.94 2759 96 2791 53 2804 20 1.691 661730 16967.4 13.2108 0.382 0.4874 0.014 0.96 2559 106 2695 78 2814 18 9.1

Sample 07WZ019A (UTM Zone 9N, N7264442, E359044)1 236069 Infinite 0.5339 0.012 0.0686 0.001 0.93 427 16 434 10 411 31 –4.12 158894 Infinite 0.5413 0.007 0.0691 0.001 0.94 431 14 439 6 449 25 4.23 169361 24194.49 0.5446 0.013 0.0699 0.001 0.91 436 16 441 10 450 35 3.24 219902 Infinite 0.5603 0.012 0.0711 0.002 0.96 443 16 452 10 483 23 8.25 138225 Infinite 0.5987 0.010 0.0752 0.001 0.94 468 16 476 8 499 25 6.26 43200 Infinite 0.8074 0.017 0.0953 0.002 0.90 587 20 601 13 587 35 0.07 762022 Infinite 0.8569 0.015 0.1016 0.002 0.96 624 22 628 11 649 22 3.98 488809 Infinite 1.9039 0.040 0.1810 0.004 0.94 1072 39 1082 23 1076 25 0.49 361175 Infinite 2.1540 0.040 0.1969 0.004 0.96 1159 41 1166 21 1148 21 –1.010 1622331 Infinite 1.9717 0.036 0.1832 0.003 0.96 1084 38 1106 20 1155 20 6.111 1164812 Infinite 2.0176 0.025 0.1867 0.002 0.95 1103 36 1121 14 1157 20 4.712 189339 Infinite 2.1414 0.053 0.1949 0.005 0.96 1148 45 1162 29 1161 21 1.113 534112 Infinite 2.1332 0.052 0.1954 0.005 0.96 1151 44 1160 28 1176 20 2.114 1087331 Infinite 2.1283 0.024 0.1927 0.002 0.95 1136 36 1158 13 1199 20 5.215 579976 Infinite 2.2720 0.035 0.2043 0.003 0.95 1198 40 1204 18 1206 20 0.616 238926 Infinite 2.5542 0.058 0.2188 0.005 0.96 1276 48 1288 29 1283 21 0.617 731780 27102.97 2.8115 0.059 0.2357 0.005 0.94 1364 49 1359 28 1353 23 –0.918 197573 Infinite 2.9058 0.072 0.2386 0.006 0.96 1380 53 1383 34 1371 20 –0.619 319831 Infinite 2.9654 0.057 0.2380 0.004 0.96 1376 49 1399 27 1421 20 3.120 1763546 37522.25 3.1919 0.044 0.2504 0.003 0.94 1441 47 1455 20 1458 21 1.221 1165661 Infinite 3.1639 0.049 0.2447 0.004 0.95 1411 48 1448 22 1500 20 5.922 326466 Infinite 4.0963 0.070 0.2877 0.005 0.95 1630 56 1654 28 1657 19 1.623 269106 Infinite 4.3279 0.078 0.3014 0.005 0.96 1698 59 1699 31 1667 19 –1.924 1083663 4496.527 4.3773 0.093 0.3020 0.006 0.96 1701 62 1708 36 1728 20 1.525 1087129 4496 4.3773 0.093 0.3020 0.006 0.96 1701 62 1708 36 1728 20 1.526 1867953 8633 4.4188 0.083 0.3006 0.006 0.96 1694 60 1716 32 1752 19 3.327 552668 21256.46 4.5575 0.070 0.3063 0.004 0.93 1722 57 1742 27 1753 22 1.8

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Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

28 138866 12624.2 5.1890 0.136 0.3370 0.008 0.92 1872 71 1851 48 1782 28 -5.129 154462 Infinite 4.9268 0.117 0.3188 0.007 0.96 1784 68 1807 43 1792 20 0.430 317874 Infinite 5.0859 0.097 0.3259 0.006 0.96 1818 64 1834 35 1820 19 0.131 434288 Infinite 4.8797 0.074 0.3147 0.005 0.95 1764 59 1799 27 1821 18 3.232 549866 Infinite 5.1098 0.108 0.3280 0.007 0.96 1829 67 1838 39 1837 18 0.433 1074683 Infinite 4.9281 0.088 0.3189 0.006 0.96 1784 62 1807 32 1842 18 3.134 532559 Infinite 5.1321 0.079 0.3268 0.005 0.95 1823 61 1841 28 1851 18 1.535 486350 Infinite 5.3359 0.133 0.3378 0.008 0.97 1876 73 1875 47 1867 18 –0.536 800934 Infinite 5.2065 0.096 0.3297 0.006 0.96 1837 65 1854 34 1868 19 1.737 521522 Infinite 5.3560 0.100 0.3374 0.006 0.96 1874 66 1878 35 1870 18 –0.238 559878 Infinite 5.2597 0.104 0.3319 0.007 0.96 1847 66 1862 37 1877 18 1.639 504199 Infinite 5.5461 0.111 0.3455 0.007 0.96 1913 69 1908 38 1878 18 –1.940 1003017 Infinite 5.5034 0.116 0.3425 0.007 0.96 1898 70 1901 40 1890 18 –0.541 895742 Infinite 5.3744 0.122 0.3341 0.008 0.96 1858 70 1881 43 1892 18 1.842 500929 25046.47 5.5076 0.122 0.3395 0.007 0.95 1884 70 1902 42 1899 21 0.743 750593 27799.75 5.5746 0.089 0.3432 0.005 0.95 1902 64 1912 31 1906 20 0.244 1060337 4331 5.7025 0.128 0.3561 0.008 0.96 1964 73 1932 43 1909 19 –2.945 699671 46644.7 5.6450 0.111 0.3442 0.007 0.96 1907 68 1923 38 1914 19 0.446 117007 Infinite 5.6858 0.135 0.3462 0.008 0.96 1917 73 1929 46 1915 20 –0.147 1110942 Infinite 5.3918 0.093 0.3325 0.006 0.96 1850 64 1884 32 1915 18 3.448 536381 Infinite 5.7471 0.110 0.3527 0.007 0.96 1947 69 1938 37 1918 18 –1.549 1763494 Infinite 5.3154 0.053 0.3283 0.003 0.95 1830 58 1871 19 1920 18 4.750 601071 Infinite 5.8051 0.144 0.3536 0.009 0.97 1952 76 1947 48 1921 18 –1.651 391738 Infinite 5.8067 0.092 0.3547 0.006 0.95 1957 66 1947 31 1923 18 –1.852 661043 Infinite 5.5558 0.069 0.3388 0.004 0.95 1881 61 1909 24 1929 18 2.553 582311 44793.16 5.4333 0.115 0.3315 0.007 0.96 1845 68 1890 40 1929 19 4.354 989480 Infinite 5.5502 0.089 0.3395 0.005 0.96 1884 64 1908 31 1931 18 2.455 409767 Infinite 5.6852 0.132 0.3470 0.008 0.96 1920 73 1929 45 1932 18 0.656 579405 38627 5.4663 0.076 0.3325 0.004 0.95 1851 61 1895 26 1932 19 4.257 585154 24381.42 5.5893 0.096 0.3405 0.006 0.94 1889 65 1914 33 1933 20 2.258 845458 Infinite 5.5816 0.095 0.3410 0.006 0.96 1891 65 1913 32 1933 18 2.259 488616 Infinite 5.8468 0.097 0.3528 0.005 0.94 1948 66 1953 32 1937 21 –0.660 561851 Infinite 5.7123 0.118 0.3498 0.007 0.96 1934 70 1933 40 1940 19 0.461 738167 Infinite 5.8019 0.085 0.3523 0.005 0.95 1945 65 1947 28 1941 18 –0.262 956282 Infinite 5.5300 0.090 0.3365 0.005 0.96 1870 64 1905 31 1941 18 3.763 624261 11350.2 5.6911 0.231 0.3523 0.014 0.95 1945 96 1930 78 1942 27 –0.264 949801 39575.05 5.7439 0.106 0.3505 0.006 0.95 1937 68 1938 36 1948 19 0.565 1509648 Infinite 5.7635 0.073 0.3527 0.004 0.95 1947 63 1941 25 1950 19 0.166 402045 Infinite 5.8819 0.075 0.3524 0.004 0.94 1946 63 1959 25 1954 19 0.467 388872 Infinite 5.7827 0.118 0.3468 0.007 0.96 1919 69 1944 40 1955 18 1.8

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Grain #

206Pb(cps)

206Pb204Pb

207Pb235U ± (2s)

206Pb238U ± (2s)

Err.corr.

206Pb�238U

±(2s)

207Pb�235U ± (2s)

207Pb�206Pb� ± (2s)

Disc.(%)

68 361914 Infinite 5.9507 0.134 0.3582 0.008 0.96 1974 74 1969 44 1955 18 –0.969 1328626 Infinite 5.6982 0.092 0.3463 0.006 0.96 1917 65 1931 31 1958 18 2.170 1454322 19135.82 5.6395 0.091 0.3416 0.005 0.94 1894 63 1922 31 1959 22 3.371 352352 Infinite 5.7087 0.145 0.3428 0.009 0.97 1900 75 1933 49 1961 18 3.172 1837660 48359.47 5.7008 0.073 0.3451 0.004 0.95 1911 62 1931 25 1963 19 2.673 1593995 31879.9 5.9513 0.060 0.3608 0.003 0.94 1986 62 1969 20 1968 19 –0.974 817904 Infinite 5.9524 0.096 0.3570 0.006 0.96 1968 67 1969 32 1974 18 0.375 1598760 Infinite 5.8846 0.081 0.3537 0.005 0.95 1952 64 1959 27 1981 18 1.476 705124 Infinite 5.9911 0.077 0.3527 0.004 0.95 1948 63 1975 25 1994 18 2.377 1067547 4490 5.9714 0.224 0.3550 0.013 0.98 1959 94 1972 74 1994 19 1.878 521489 37249.21 6.0960 0.081 0.3583 0.004 0.93 1974 63 1990 26 2000 22 1.379 776775 Infinite 5.8919 0.131 0.3449 0.008 0.96 1910 71 1960 44 2010 18 5.080 382391 Infinite 5.9778 0.115 0.3406 0.006 0.96 1889 67 1973 38 2040 19 7.481 313544 Infinite 6.6290 0.104 0.3734 0.006 0.95 2046 69 2063 32 2051 19 0.382 302188 9443.374 6.7424 0.189 0.3745 0.009 0.92 2051 80 2078 58 2078 28 1.383 313566 Infinite 6.6748 0.140 0.3716 0.008 0.95 2037 74 2069 43 2081 20 2.184 260927 Infinite 6.9272 0.194 0.3814 0.010 0.94 2083 83 2102 59 2088 24 0.285 586554 13640.79 6.7869 0.093 0.3762 0.004 0.92 2059 66 2084 29 2120 23 2.986 517437 Infinite 6.9086 0.146 0.3766 0.008 0.96 2060 75 2100 44 2128 19 3.287 211504 Infinite 7.5536 0.170 0.3997 0.009 0.96 2168 81 2179 49 2151 18 –0.888 402300 12190.9 7.2474 0.177 0.3852 0.009 0.94 2100 79 2142 52 2167 24 3.189 1942357 Infinite 6.6772 0.128 0.3543 0.006 0.94 1955 68 2070 40 2184 22 10.590 1052854 Infinite 7.5010 0.180 0.3922 0.009 0.97 2133 82 2173 52 2212 18 3.691 199856 33309.27 8.0738 0.164 0.4063 0.008 0.96 2198 79 2239 45 2250 19 2.392 404980 25311.27 8.0241 0.169 0.4049 0.008 0.95 2192 80 2234 47 2254 19 2.893 344700 Infinite 7.7519 0.144 0.3896 0.007 0.95 2121 74 2203 41 2257 19 6.094 237583 47516.52 8.4847 0.215 0.4131 0.010 0.95 2229 86 2284 58 2303 21 3.295 215540 Infinite 8.5484 0.167 0.4214 0.008 0.94 2267 80 2291 45 2307 21 1.896 412688 8971.482 8.7221 0.186 0.4267 0.008 0.91 2291 80 2309 49 2318 26 1.297 1935088 8562.34 7.9150 0.171 0.3893 0.008 0.96 2120 78 2221 48 2332 19 9.198 560728 Infinite 9.0870 0.199 0.4414 0.010 0.96 2357 87 2347 51 2335 18 –0.999 477989 Infinite 8.7823 0.150 0.4224 0.007 0.95 2271 78 2316 40 2347 18 3.2100 624181 Infinite 8.9060 0.168 0.4243 0.008 0.96 2280 81 2328 44 2360 18 3.4101 380158 47519.8 8.6830 0.208 0.4094 0.010 0.96 2212 85 2305 55 2370 18 6.6102 694627 Infinite 9.2172 0.211 0.4382 0.010 0.96 2343 88 2360 54 2379 18 1.5103 1168349 16004.78 9.1020 0.210 0.4309 0.010 0.95 2310 86 2348 54 2385 20 3.1104 432616 Infinite 9.2924 0.167 0.4286 0.008 0.95 2299 80 2367 43 2411 18 4.6105 385544 Infinite 9.9495 0.315 0.4585 0.014 0.96 2433 104 2430 77 2417 21 –0.7106 2043110 Infinite 9.6659 0.170 0.4431 0.008 0.96 2364 82 2403 42 2444 17 3.2107 1072864 Infinite 9.7237 0.200 0.4452 0.009 0.96 2374 86 2409 50 2448 17 3.0

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represented by three grains between 427 and 436 Ma.Eleven zircons fall in the interval 1076–1458 Ma, whereas22 grains form an age group between 2051 and 2448 Ma.The sample yielded four Archean zircons at 2685, 2714,2761, and 2770 Ma.

Discussion: paleogeographic implication ofresults

The detrital zircons in the Imperial and Tuttle formationswere likely derived from one or more source regions charac-terized by sedimentary and (or) igneous provinces compris-ing largely (i) Paleoproterozoic and Archean (i.e., > 1.6 Ga)zircons, (ii) Mesoproterozoic zircons with abundant ‘‘Gren-ville-aged’’ grains in the 1.0–1.3 Ga interval, and (iii) latePrecambrian and early Paleozoic zircons in the 400–500and 500–700 Ma intervals (Fig. 5). Samples from the Impe-rial Formation show a similar detrital zircon age spectrum;the westernmost sample (07WZ020A; Fig. 2), however, ismarked by a greater proportion of Mesoproterozoic (andolder) grains, whereas the eastern sample 07TH33B (Fig. 2)contains predominantly late Neoproterozoic (and younger)zircons. Here, we cannot rule out the possibility that a minorfraction of a total population was missed because of the rel-atively low number of grains (n £ 61) dated in these samples(e.g., Vermeesch 2004). In contrast, the Tuttle Formationsamples display a more restricted relative probability agedistribution, marked by a strong peak of middle Paleoproter-ozoic ages, with lesser peaks representing Mesoproterozoic,earlier Paleoproterozoic, and Archean ages. From two sam-ples, our Tuttle Formation results are similar to detrital zir-con from five samples of Tuttle Formation collected fromthe Richardson Mountains that have prominent ages of ca.360–390, 1000–1300, and 1800–2000 Ma, with minoramounts of 430–680 Ma (Beranek et al. in press).

The spectrum of Paleoproterozoic and Archean zirconages in the Imperial Formation is marked by dates in the in-tervals 1.8–2.1 and 2.6–2.8 Ga, and a virtual absence ofgrains between 2.1 and 2.6 Ga. The age spectrum of theTuttle Formation, on the other hand, is defined by an overallpredominance of 1.8–2.0 Ga (and older) zircons. These agesmatch well those in basement provinces of the northwesternCanadian Shield (Fig. 6), in particular, the 1845 Ma Ga FortSimpson Arc, 1.84–1.95 Ga Wopmay Orogen, 1.92–2.1 GaTaltson Arc, and >2.5 Ga Slave and Rae provinces (Fig. 6;e.g., Hoffman 1988; Villeneuve et al. 1991, 1993; Bostockand van Breemen 1994; Gehrels and Ross 1998). As demon-strated by the 1.8–2.0 Ga detrital zircon in Mesoproterozoicstrata from the East Greenland Caledonides (Watt et al.2000), the Greenland portion of Laurentia is also a potentialsource for Paleoproterozoic grains within Imperial and Tut-tle formations. Ca. 1.74–1.79 Ga igneous rocks in the west-ern Churchill Province are a potential source for provenanceof the 1.75–1.80 Ga zircons (Hoffman 1988; van Breemen etal. 2005), as are ca. 1.74–1.78 Ga igneous rocks in northernGreenland (e.g., Nutman et al. 2008).

Grains from Imperial Formation between 2.0 and 2.5 Gaare of interest, as they are common in Paleozoic miogeocli-nal strata in the northern Cordillera and the clastic wedge ofthe Arctic Islands, but largely absent in the southern Cordil-lera (e.g., Gehrels et al. 1995; McNicoll et al. 1995; GehrelsT

able

1(c

oncl

uded

).

Isot

opic

ratio

sA

ppar

ent

ages

(Ma)

Gra

in#

206 P

b(c

ps)

206P

b204P

b

207P

b235U

±(2s

)206P

b238U

±(2s

)E

rr.

corr

.206P

b�

238U

± (2s

)207P

b�

235U

±(2s

)207P

b�

206P

b�

±(2s

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isc.

(%)

108

4559

4910

132.

211

.291

70.

177

0.46

610.

006

0.92

2466

8125

4840

2600

225.

110

949

6249

1341

2.13

12.4

471

0.26

30.

4879

0.01

00.

9525

6193

2639

5626

8520

4.6

110

4278

3718

28.3

6313

.117

70.

177

0.50

630.

007

0.95

2641

8626

8836

2714

182.

711

182

9406

Infi

nite

13.7

007

0.25

50.

5158

0.01

00.

9626

8195

2729

5127

6117

2.9

112

1567

79In

fini

te14

.306

30.

252

0.53

240.

009

0.96

2752

9527

7049

2770

170.

6

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nd;

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rr.,

erro

rco

rrec

tion;

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nce;

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Lemieux et al. 531


and Ross 1998; Nelson and Gehrels 2007). They could havebeen sourced from the 2.0–2.4 Ga accreted Hottah, BuffaloHead, and Chinchaga terranes within the Wopmay orogen,the ca. 2.35 Ga Arrowsmith orogen of the Rae domain(Berman et al. 2005), or recycling of Paleoproterozoic strataof the western Churchill Province, in which abundant 1.9–2.4 Ga zircons have been documented (Davis et al. 2005).They could also have been recycled from Neoproterozoicstrata deposited along the northwestern margin (present-daycoordinates) of Laurentia that yielded abundant Paleoproter-ozoic and Archean zircons (Fig. 7; Rainbird et al. 1992,1997). Given the presence of thick early and middle Paleo-zoic strata preserved in the Interior Plains and Arctic Plat-form (e.g., Fritz et al. 1991; Trettin et al. 1991), however, it

is likely that much of the Proterozoic strata remained unex-posed throughout the Late Devonian and Early Carbonifer-ous. Thus, the Paleoproterozoic and Archean zircons in oursamples probably originated from many different provincesof the adjacent northwestern Canadian Shield and likelywent through multiple sedimentary cycles prior to their dep-osition in the Peel Region.

The origin of the Mesoproterozoic zircon in our samplesis unclear. On geochronological and geochemical grounds,Rainbird et al. (1992, 1997) interpreted the 1.0–1.6 Ga zir-con within Neoproterozoic quartzarenites of the Shaler andMackenzie Mountains supergroups in northwestern Canadato have been sourced from the Grenville orogen and trans-ported over 3000 km across the Laurentian craton in exten-

Fig. 5. U–Pb age spectra of single detrital zircon grains for the Imperial and Tuttle formations, northern Mackenzie Mountains. Samples arearranged from oldest at the base to youngest at the top. The grouping between 500 and 700 Ma (grey shading) stands out as it is absentfrom the Laurentian magmatic record. Plot includes all analyses with <5% discordance.



Fig

.6.

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Lemieux et al. 533


sive Neoproterozoic river systems. An alternative possibilityis that these grains were derived from more ‘‘proximal’’sources, as growing evidence suggests that 1.0–1.3 Ga crustwas present along and outboard of the Canadian Cordilleranmargin (e.g., Gehrels and Ross 1998; Ross et al. 2005; Le-mieux et al. 2007; Nelson and Gehrels 2007). Alternatively,McNicoll et al. (1995) documented a number of Mesoproter-ozoic zircon grains (mostly between 1.04 and 1.20 Ga) fromsandstones of the Middle and Upper Devonian clastic wedgein the Arctic Islands, as well as many Paleoproterozoic andArchean zircons (Fig. 8). McNicoll et al. (1995) postulatedthat metamorphic and metasedimentary rocks of the EastGreenland Caledonian orogen provided the best potentialsource of Mesoproterozoic detrital zircon. This hypothesiswas later supported by Patchett et al. (1999) who singledout the Caledonian orogenic belt as the only plausible ulti-mate sediment source for marginal Cambrian to Devonianstrata present in the Franklinian mobile belt of Arctic Can-ada, based on their Nd isotopic signature and known paleo-current directions. Patchett and colleagues further inferredthat following subsequent uplift and erosion of the activeFranklinian belt in Middle and Late Devonian time, as pro-posed by Embry and Klovan (1976), recycled sedimentslargely propagated southwestward from the orogenic system,reaching the northwestern margin of North America and giv-ing rise to the thick Upper Devonian Imperial Assemblage.The occurrence of relatively abundant Grenvillian detritalzircon ages within the Cambrian Portfjeld Formation ofnorthern Greenland (Kirkland et al. 2009), the Scottish Cale-donides (Cawood et al. 2007), and lesser amounts in Sval-

bard (Pettersson et al. 2009) are consistent with thishypothesis. Given the presence, however, of Grenville-ageddetrital zircons in Neoproterozoic and Paleozoic sedimentaryrocks from Greenland and throughout Laurentia, includingthe Cordillera, Canadian Shield, and Arctic Islands, whichmay have been recycled in any number of configurations,these grains provide limited diagnostic provenance informa-tion.

An exposed late Neoproterozoic – Cambrian source is in-dicated by the presence, in the Imperial Formation, of 500–700 Ma detrital zircons (grey shading in Fig. 5). This agerange stands out as it is virtually absent from the mid-Paleo-zoic miogeoclinal record of the North American Cordillera,including in terranes of the mid- to late Paleozoic peri-Lau-rentian realm (Fig. 8; e.g., Gehrels et al. 1995; Gehrels andRoss 1998; Nelson and Gehrels 2007). Gehrels and Dickin-son (1995) dated 500–525 Ma zircons in Triassic miogeocli-nal strata in Nevada and tied their provenance to nearbyplutons in the western United States. There is no known lo-cal source for zircons of this age in the region of our studyarea. One possibility is that these grains were derived fromca. 575 and 570 Ma synrift volcanic rocks that are preservedwithin Neoproterozoic Windermere Supergroup strata fromthe southeastern Canadian Cordillera (Colpron et al. 2002).This hypothesis is unlikely because mafic and alkaline vol-canic rocks are unlikely to yield voluminous zircon, and itwould have required northeasterly and (or) easterly sedimenttransport across the basin, in a general direction opposite toknown paleocurrent data within the Imperial Formation(Gordey et al. 1991; Braman and Hills 1992; Hadlari et al.

Fig. 7. Probability–density diagrams illustrating U–Pb age spectra of single detrital zircon grains for Proterozoic strata of the CanadianArctic Islands and northern Mackenzie Mountains and Interior Plains. The compilation includes data from the Neoproterozoic Shaler Groupand Mackenzie Mountains reported in Rainbird et al. (1992, 1996, 1997) and Villeneuve et al. (1998). Data from the Imperial and Tuttleformations are from this study.



2009). Another alternative is that these grains were derivedfrom the 503 Ma igneous rocks of Pearya Terrane, northernEllesmere Island (Trettin et al. 1987), however, very limitedgeochronological data from Pearya have not recognized520–700 Ma magmatism; a detrital zircon study of rocksfrom Pearya that predate accretion to Laurentia would testthis option.

In a detrital zircon study of Triassic sandstone from thecircum-Arctic region, Miller et al. (2006) reported domi-nantly 500 to 700 Ma zircon populations in sandstone fromthe Pat Bay and Ivishak formations, northern Axel HeibergIsland and northeastern Alaska, respectively (Fig. 9). On thebasis of facies change (Embry 1991) and the dominance ofMeso- and Paleoproterozoic detrital zircons within the sam-ple, the Pat Bay Formation was inferred by Miller et al.(2006) to have been shed from a proposed landmass termed‘‘Crockerland’’ and situated to the north of the present-daysampling site (see Embry 1992); it is unknown whetherCrockerland was a distinct landmass or part of a larger cra-ton (Siberia?). This proposed landmass, which may lie

buried on the continental shelves of the Arctic Ocean, layoutboard of the Arctic North American margin in mid-Pale-ozoic time, and may have been an important source of sedi-ment for the Sverdrup Basin from the Carboniferous to theJurassic (Embry 1992). Miller et al. (2006) speculated thatthe landmass consisted of igneous and (or) sedimentarysource regions comprising predominantly 500–600 Ma zir-con, with subordinate Ordovician and late Precambrian pop-ulations. In contrast, grains from the Ivishak Formation wereinterpreted to have been derived from late Precambrian plu-tons dated in basement rocks of Arctic Alaska (e.g., Amatoet al. 2009), which were also interpreted to have contributedabundant 540–700 Ma detrital zircon to Paleozoic siliciclas-tic strata of Seward Peninsula (Amato et al. 2009), part ofthe Arctic Alaska – Chukotka terrane. During Paleozoictime, Arctic Alaska – Chukotka had affinities with Siberia(Patrick and McClelland 1995), as demonstrated by 420–490, 520–720, and 900–2000 Ma detrital zircon within Dev-onian to Mississippian strata from Wrangel Island, part ofthe eastern Siberian Shelf (Miller et al. 2010). Largely based

Fig. 8. Probability–density diagrams illustrating U–Pb age spectra of single detrital zircon grains for selected Devonian miogeoclinal strataalong the North American Cordilleran margin. Also included are data from strata of the Devonian clastic wedge of Arctic Canada (McNi-coll et al. 1995). Data for east-central Alaska reported in Gehrels et al. (1999); data for northern British Columbia reported in Gehrels andRoss (1998) and Ross et al. (1993); data for Nevada reported in Gehrels and Dickinson (1995); data for Sonora reported in Gehrels andStewart (1998). The grey shading highlights a range of ages that is absent from the Laurentian magmatic record.

Lemieux et al. 535


on the occurrence of dominant 540–700 Ma zircon in Paleo-zoic strata, Arctic Alaska – Chukotka terrane is interpretedto be exotic to Laurentia in early Paleozoic (Amato et al.2009), and it possibly accreted to northern Laurentia by theDevonian (Lane 2007; Colpron and Nelson 2009). From theperspective of Imperial Formation, the presence of 500–700 Ma zircons in circum-Arctic Triassic strata not onlysuggest an Arctic provenance for these grains within the Im-perial Formation, but that this source was available to north-ern Laurentia as early as the Devonian.

The occurrence of 500–700 Ma zircons, a significantcomponent of the detrital zircon population in the ImperialFormation, provides important insights into patterns of sedi-ment dispersal in the northern Cordillera in Late Devoniantime. Because zircon of these ages are virtually absent fromthe Laurentian magmatic record (e.g., Amato et al. 2009),including basement of the east Greenland Caledonides (e.g.,Watt et al. 2000), it seems clear that a number of zircon inthe Peel Region were derived from an ‘‘exotic’’ source re-gion. Zircons of these ages have been documented in mag-matic provinces on other continents, such as the easternmargin of Baltica (e.g., Willner et al. 2003), northern and

southwestern Siberia (e.g., Gladkochub et al. 2006; Amatoet al. 2009; Pease and Scott 2009), Arctic Alaska – Chu-kotka (e.g., Patrick and McClelland 1995; Johansson et al.2004), and Avalonia (Murphy et al. 2004). Whether sedi-ment from these cratons could reach Laurentia in early and(or) mid-Paleozoic time is very poorly understood (Miller etal. 2006; Lane 2007). Recent early- to mid-Paleozoic globalplate reconstructions (e.g., Scotese 2001; Lawver et al.2002; Golonka et al. 2003) have positioned Baltica and Si-berian cratons in relative proximity to each other, outboardof the northern (present-day coordinates) Laurentian margin.It appears that Baltica and Laurentia shared a complex his-tory of Neoproterozoic and Paleozoic major orogenic andbreak-up events (Torsvik et al. 1996) and formed part ofthe same continent following the Siluro-Devonian Caledo-nian event (e.g., Golonka et al. 2003) and, therefore, mayhave been in position to supply sediment to Laurentia byDevonian time (Fig. 10). The detrital zircon within Imperialand Tuttle formations, however, do not reflect the 980–710 Ma accretionary tectonic events of northern Baltica(e.g., Pease et al. 2008) nor the 980–910 and 830–710 Maigneous activity associated with the Valhalla orogeny of

Fig. 9. Probability–density diagrams illustrating U–Pb age spectra of single detrital zircon grains for Triassic strata of the Canadian ArcticIslands and northern Arctic Alaska terrane. The compilation includes data from the Pat Bay and Ivishak formations reported in Miller et al.(2006) and Villeneuve et al. (1998). The grey shading highlights a range of ages that is absent from the Laurentian magmatic record. Datafor the Imperial and Tuttle formations are also shown (this study).



Scotland, East Greenland, Svalbard, and Norway (Cawoodet al. 2010). We cannot rule out a Baltican source, whichwould have been on the eastern, or opposite, margin of theCaledonides, but we might also expect 980–720 Ma detritalzircon if it were a dominant source. On the present easternmargin of Laurentia, at right angles to all known paleocur-rent directions (Embry and Klovan 1976; Hadlari et al.2009), Avalonian rocks of Cambrian age contain a high pro-portion of ca. 580–680 Ma detrital zircon (Murphy et al.2004). By Early–Middle Devonian time, Avalonia collidedwith southern Baltica and Laurentia during the Acadian or-ogeny (e.g., van Staal et al. 1998); however, Acadian fore-land basin sandstones from New England containpredominantly 420–460 and 1000–1260 Ma detrital zircon,attributed to recycling of the preexisting continental marginrather than a large influx of Avalonian sediment (McLennanet al. 2001). Siberia has a Precambrian history similar toLaurentia (e.g., Rainbird et al. 1998), including ca. 2100–1800 Ma assembly of Archean cratons but ending with a ca.750–700 Ma rift-to-drift transition away from Rodinia (e.g.,Pisarevsky et al. 2008).

In a synthesis of the mid-Paleozoic tectonic evolution ofnorthwestern North America, Lane (2007) documented evi-

dence for progressive docking of an allochthonous landmassto northwestern Laurentia from Silurian through Early Car-boniferous time, and speculated the terrane to include partof the Siberia craton (possibly including Arctic Alaska –Chukotka). If part of Siberia (as, or including, Crockerland)was the ultimate source for the late Neoproterozoic andCambrian zircons in the Imperial Formation, it had to be ex-posed and provide sediments to the northern mainland priorto the Carboniferous. The absence of 500–700 Ma zircons inDevonian strata, albeit from a restricted data set, of the Arc-tic Islands and Cordilleran miogeocline (see earlier in thetext), including the overlying Upper Devonian – Lower Car-boniferous Tuttle Formation (this study) is of interest andmay suggest the source to have supplied a very restricted re-gion of the northern mainland over a limited period of time.Our data, therefore, document a significant shift in prove-nance from a source with ‘‘Siberian’’ affinity to one with apredominantly Laurentian signature, in part supporting theinterpretation of Gordey et al. (1991), who suggested thatby the mid-Mississippian, sedimentary rock of westerly andnortherly derivation had given way to clastic input from theLaurentian craton.

The Devonian, Silurian, and late Ordovician grains popu-

Fig. 10. Middle to Late Devonian paleogeography showing Laurentia, Baltica, and Siberia after Lawver et al. (2002) and Golonka et al.(2003).

Lemieux et al. 537


lating the Imperial and Tuttle formations were likely derivedfrom igneous rocks along the Canada – Alaska Arctic mar-gin (e.g., Gehrels and Ross 1998). The Devonian and LateOrdovician grains could have been derived from (i) 354–406 Ma syntectonic granite to monzodiorite of the northernYukon (Gordey et al. 1991; Lane 1997); (ii) Middle andUpper Devonian plutons of the northern Axel Heiberg andEllesmere islands (Trettin et al. 1987, 1992); and (iii) 454 Mavolcanics of the northern Ellesmere Islands (Trettin et al.1987). As suggested by their occurrence in Imperial andTuttle formations, as well as in Middle and Upper Devon-ian strata of the Arctic Islands, northwest Yukon, and east-central Alaska (e.g., McNicoll et al. 1995; Gehrels et al.1999), ca. 430 Ma grains likely blanketed much of north-western Laurentia as a result of orogenic magmatism alongthe margin of Arctic Alaska and the Canadian Arctic(Gordey et al. 1991; Gehrels and Ross 1998; Gehrels etal. 1999; Lane 2007). Coupled with the presence of 500–700 Ma detrital zircons inferred to have been derived froma source exotic to Laurentia, the lower Paleozoic detritalzircons may even record magmatism of the arc(s), conti-nental or otherwise, that collided with the northern Lauren-tian margin.

In summary, detrital zircons in the Imperial and Tuttleformations were likely derived from an extensive region ofnorthwestern Lauentia, including the northwestern CanadianShield, igneous and sedimentary provinces of Canada’s Arc-tic Islands, and possibly the northern Yukon. Given the highresistance of zircons, we must allow for multiple stages ofrecycling from older sedimentary successions. Ultimatesources for some zircons documented here possibly include(i) the East Greenland Caledonides; (ii) part of the Siberiancraton, which may include Arctic Alaska – Chukotka thatlay outboard of Laurentia in early Paleozoic time; (iii) Bal-tica; and (iv) Precambrian provinces of Laurentia, in partic-ular basement rocks of northern Greenland, the Trans-Hudson Orogen, the western Churchill Province of centralLaurentia, and the Grenville Province of eastern Laurentia.

Conclusions

This study presents detrital zircon analyses from theUpper Devonian Imperial Formation and Upper Devonian –Lower Carboniferous Tuttle Formation, exposed in thenorthern Mackenzie Mountains of the southern Peel Region.The Imperial Formation records records a wide spectrum ofU–Pb ages from late Precambrian and early Paleozoic,Meso- and Paleoproterozoic, and Archean source rocks.This age spectrum favors derivation predominantly fromnorthern Laurentia. The presence of late Precambrian andearly Paleozoic zircons, absent from the Laurentian mag-matic record, suggest provenance from an exotic source re-gion to the north. Possible sources include Baltica, ArcticAlaska – Chukotka, and Siberia.

In contrast, the detrital age spectrum of Tuttle Formationsamples displays a more restricted age distribution consis-tent with derivation ultimately from sources with Laurentianaffinity. These data, therefore, indicate that sediment prove-nance underwent an abrupt shift from an influx of northerlyderived sediments including zircon ages apparently exotic to

Laurentia in Late Devonian time to a source of Laurentianaffinity by Mississippian time.

AcknowledgementsThis work was funded by the Northern Oil and Gas Sci-

ence Research Initiative 2005–2009 of Indian and NorthernAffairs Canada (INAC) through the ‘‘Regional GeoscienceStudies and Petroleum Potential of the Peel Plateau andPlain, NWT and Yukon’’ Project and the INAC Strategic In-vestments in Northern Economic Development Program(SINED). The Radiogenic Isotope Facility (RIF) at the Uni-versity of Alberta is supported by a Natural Sciences andEngineering Research Council of Canada (NSERC) MajorFacility Access grant. Staff at the RIF is thanked for theircollaboration. Robert H. Rainbird reviewed an early versionof the manuscript and offered constructive comments. Wegratefully acknowledge the Associate Editor W.J. Davis andvery helpful reviews by J.M Amato and V. Pease.

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