Downloaded from geology.gsapubs.org on October 2, 2010

Geology

Paleogeographic implications of non−North American sediment in the Mesoproterozoic upper Belt Supergroup and Lemhi Group, and , USA

Eric D. Stewart, Paul K. Link, C. Mark Fanning, Carol D. Frost and Michael McCurry

Geology 2010;38;927-930 doi: 10.1130/G31194.1

Email alerting services click www.gsapubs.org/cgi/alerts to receive free e-mail alerts when new articles cite this article Subscribe click www.gsapubs.org/subscriptions/ to subscribe to Geology Permission request click http://www.geosociety.org/pubs/copyrt.htm#gsa to contact GSA Copyright not claimed on content prepared wholly by U.S. government employees within scope of their employment. Individual scientists are hereby granted permission, without fees or further requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and science. This file may not be posted to any Web site, but authors may post the abstracts only of their articles on their own or their organization's Web site providing the posting includes a reference to the article's full citation. GSA provides this and other forums for the presentation of diverse opinions and positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political viewpoint. Opinions presented in this publication do not reflect official positions of the Society.

Notes

© 2010 Geological Society of America Downloaded from geology.gsapubs.org on October 2, 2010 Paleogeographic implications of non–North American sediment in the Mesoproterozoic upper Belt Supergroup and Lemhi Group, Idaho and Montana, USA

Eric D. Stewart1*, Paul K. Link1, C. Mark Fanning2, Carol D. Frost3, and Michael McCurry1 1Department of Geosciences, Idaho State University, Pocatello, Idaho 83209, USA 2Research School of Earth Sciences, Australian National University, Canberra, ACT 5000, Australia 3Department of Geology, University of Wyoming, Laramie, Wyoming 82071, USA

ABSTRACT ington and Idaho (Doughty et al., 1998), but A non–North American provenance for the lower Belt Supergroup of North America has is otherwise absent in western (Ross been used to support various pre-Rodinian paleogeographic reconstructions. Unlike the lower and Villeneuve, 2003). The presence of signifi - Belt Supergroup, most upper Belt Supergroup provenance studies have inferred Lau- cant 1570–1590 Ma detrital zircons in the Belt rentian sediment sources. We test this hypothesis by analyzing U-Pb and Lu-Hf isotopes on Supergroup, combined with an inferred west- detrital zircons, and whole-rock Nd isotopes from the Missoula (upper Belt Supergroup) and ern provenance from paleocurrents (Cressman, Lemhi Groups, and comparing to possible Laurentian sources. Detrital zircons from 11 sand- 1989), suggests that the continent off Lauren- stones analyzed show dominant ages between 1680 and 1820 Ma. These zircons are predomi- tia’s western margin included crystalline rocks nantly magmatic in paragenesis. Belt Supergroup–aged (1400–1470 Ma) and 2400–2700 Ma of that age. The 1570–1590 Ma magmatic populations represent minor components. Lu-Hf isotopic analyses for 1675–1780 Ma Missoula rocks in South Australia (Goodge et al., 2008) Group and Lemhi Group detrital zircons range from εHf(i) +9 to –12 and +8 and –7, respec- and north Queensland (Sears and Price, 2003; tively. Belt Supergroup–aged grains from the Bonner Formation, Missoula Group, have εHf(i) Blewett et al., 1998) support various Lauren- values between +5 and –9, exceeding coeval ranges from the Mojave and Yavapai terranes tian connections with Australia. [εHf(i) between +5 and 0]. Whole-rock Nd isotopes from Lemhi Group yield a range The bulk of the Missoula Group was depos- in εNd(1400) between +1.1 and –5.9. Immature feldspathic sediment, nearly unimodal detrital ited between 1454 ± 9 and 1401 ± 6 Ma (Evans zircon spectra, and dissimilar Belt Supergroup–aged zircon Hf signatures suggest that distal et al., 2000). Previous provenance studies using portions of the Yavapai and Mojave terranes intruded by A-type magmas were not the source detrital zircon and monazite found dominate for the Missoula and Lemhi Groups. Instead, a slightly modifi ed Mesoproterozoic proto- ages between 1640 and 1860 Ma (Ross et al., SWEAT (southwestern and East Antarctica) model can best account for the 1991; Ross and Villeneuve, 2003). These ages sedimentologic and isotopic characteristics of the Missoula and Lemhi Groups. An alternative are common in the Mojave and Yavapai prov- model with a source from southeastern Siberia and the Okhotsk Massif is less preferred. inces of the southwestern United States. Prov- enance ages combined with northeast-directed INTRODUCTION 1470 Ma (Sears et al., 1998; Evans et al., 2000), paleofl ow (Winston, 1986) led most workers to Reconstructions of the early Neoproterozoic contain 1570–1590 Ma detrital zircon popula- infer a southwest Laurentian source for the Mis- remain contentious tions (Ross and Villeneuve, 2003; Link et al., soula Group, as contrasted with a non-Lauren- (e.g., see Li et al., 2008). Models involving 2007). This age is found in felsic intrusive tian, 1570–1590 Ma source for the Lower Belt western Laurentia commonly invoke the cre- rocks of the Priest River Complex of Wash- (Ross and Villeneuve, 2003). ation of a late Paleoproterozoic proto-Rodinia that persisted until Rodinia breakup (e.g., Missoula Group Australia Figure 1. Paleogeographic

Sears and Price, 2003; Goodge et al., 2001) 5 km Garnet Range 2a reconstruction, modifi ed to explain the lack of Grenville-aged belts in McNamara Hearne Province from Goodge et al. (2008). (>2.5 Ga) southwestern Laurentia. Different reconstruc- Bonner (1b) Tie points: 1a—Proposed Mt. Shields (1b, 1c) Gawler Antarctic and Lauren- Shepard Craton 2b tions place East Antarctica (Moores, 1991; Snowslip (1b) tian ca. 1.7 Ga crystalline

0 km Goodge et al., 2008), Australia (Blewett et Priest River Medicine Hat sources for Missoula (1b, Lemhi Group Terre Complex (2.6–3.3 Ga) 1c) and Lemhi Group (1c, al., 1998), south China (Li et al., 2008), and Adelie >2.5 Ga–1.58 Ga 15 km Swauger (1d) 1d, 1e, 1f) samples. 2a— Siberia (Sears and Price, 2003) off the western s King George Great Fall V Land 1b c Zone 1590 Ma Gawler Range Vol- margin of Laurentia during deposition of the Tectoni Gunsight (1c, 1d) 1e 1c canics. 2b—1580 Ma felsic Belt Supergroup. 10 km 1f 1d augen gneiss (Doughty et Apple Creek The Mesoproterozoic Belt Supergroup (Pur- 1a al., 1998) from Priest River cell Supergroup in ) is a 15–20-km-thick 5 km Complex. Figure is compiled Big Creek (1d, 1e)** Grouse Wyoming C from Goodge et al. (2008), package of largely siliciclastic strata extending Block k. Craton West Fork (1d) 1a Inyo Creek (1d, 1f)* (>2.5 Ga) (>2.5 Ga) Winston (1986), Foster et al. from southwest Montana (United States) to 0 km Victoria (2006), Bennett and DePaolo Northern boundary East Antarctica Land southern (Canada) (Fig. 1; 1a (1987), and Fanning et al. of 1.47–1.37 Ga Santaquin Complex Harrison et al., 1974). The Belt Supergroup, Laurentian A-type (1988). *1f is from Yellow- composed of the Lower Belt, Ravalli, Piegan, granites jacket Formation, correlated Belt to Inyo Creek Formation, and Missoula Groups, has played an important Yavapai Supergroup Mojave and West Fork Formation (1.84–1.7 Ga) (1.8–1.7 Ga) part in the proto-Rodinia debate. The lowest Lemhi Group and (Winston et al., 1999). **1e is correlatives

three groups, deposited between ca. 1454 and km 00 from Hoodoo , cor- 1.59–1.58 Ga 4 magmatism Mazatzal related to Big Creek Forma- (1.6–1.7 Ga) *E-mail: [email protected]. tion (Winston et al., 1999).

© 2010 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. GEOLOGY,Geology, October October 2010; 2010 v. 38; no. 10; p. 927–930; doi: 10.1130/G31194.1; 5 fi gures; Data Repository item 2010257. 927 Downloaded from geology.gsapubs.org on October 2, 2010

The Lemhi Group is an ~15-km-thick pack- (2008). For the Gunsight and Mount Shields Hf isotopes from Missoula Group detrital zir- age of largely siliciclastic Mesoproterozoic samples, new grain mounts were prepared from cons dated between 1675 and 1780 Ma yield a strata found in east-central Idaho (Fig. 1; Rup- another aliquot of the same zircon separate ana- wide range in initial ratios, εHf(i) between +9 pel, 1975). Detrital zircon age spectra from the lyzed previously in Arizona. Additional detri- and −12 (Fig. 3). The εHf(i) values for 1675– Lemhi Group match those of the Missoula Group tal zircon SHRIMP U-Pb ages and Hf isotope 1780 Ma detrital zircons from the Lemhi Group (Link et al., 2007). Detrital zircons (Link et al., ratios were determined for the Bonner Forma- are similar, ranging between +8 and −7. An 2007) and crosscutting intrusions (Doughty and tion and an additional sample of the Mount isotopically heterogeneous source is inferred, Chamberlain, 1996) bracket Lemhi Group depo- Shields Formation (both location 1b in Fig. 1). ranging from Paleoproterozoic depleted mantle sition between 1454 ± 9 Ma and 1370 Ma. Cathodoluminescence (CL) images were used (highest values) to recycled basement It is widely recognized that Lu-Hf isotope to identify magmatically zoned zircon grains (lowest values), and/or mixtures thereof. ratios on dated detrital zircons can be used as a between 1675 and 1780 Ma and younger than Initial Hf isotope values for Belt Super- geochemical tracer in provenance studies (e.g., 1470 Ma for the Lu-Hf analysis. Hf analysis group–aged zircons of the Bonner Formation, see Kinny and Maas, 2003). For this reason, was also conducted on dated SHRIMP spots Missoula Group, yield εHf(i) values between Lu-Hf isotopic analyses were made on dated from two detrital zircon samples from Link et +5 and −9. This range is far greater than the Paleoproterozoic and Mesoproterozoic detrital al. (2007; 13PL01—Yellowjacket Formation +7–0 εHf(i) range for A-type magmatic zircons zircons from the Missoula and Lemhi Groups. and 02RL888—Hoodoo Quartzite). from southwest and central Laurentia (Goodge Values for Mesoproterozoic grains are com- Sm-Nd analyses on samples from and Vervoort, 2006) (Fig. 3). While three of pared with those of A-type granites from south- the Lemhi Group and correlative strata plus one eight Belt Supergroup–aged Bonner Formation west Laurentia (Goodge and Vervoort, 2006). argillite sample from the Missoula Group were zircons overlap with the εHf(i) range reported A comparison is reasonable because volumi- performed at the University of Wyoming fol- by Goodge and Vervoort (2006), the other fi ve nous A-type magmas began intruding much lowing protocols described in Frost et al. (2006). have signifi cantly enriched εHf(i) values, indi- of the Mojave and Yavapai terranes (Fig. 1) For data tables (U-Pb, Lu-Hf, and Sm-Nd) and cating derivation from signifi cantly older crust. ca. 1475 Ma, ~20 m.y. prior to the beginning of Universal Transverse Mercator sample loca- Southwest Laurentian A-type granites also Missoula Group deposition, and ~75 m.y. prior tions, see the Data Repository. have high zircon fertility (Dickinson, 2008). to Bonner Formation deposition. We also com- Thus the very small number of 1400–1470 Ma pare new whole-rock Nd isotope values from RESULTS AND DISCUSSION zircon grains in the Missoula and Lemhi fi ne-grained Lemhi Group strata to possible LA-MC-ICP-MS and SHRIMP U-Pb detri- Groups, combined with different εHf(i) ranges, southwest Laurentian sources (e.g., Bennett and tal zircon age spectra from 980 zircon grains suggests that the sediment in the Missoula and DePaolo, 1987). in 11 samples from the Mesoproterozoic Mis- Lemhi Groups was not sourced from portions soula and Lemhi Groups, sampled over tens of of the Mojave and Yavapai terranes intruded by METHODS kilometers of stratigraphy and over hundreds A-type magmas. These zircons may have come Detrital zircons were separated from samples of square kilometers, reveal dominant ages from rift-related magmatism in the Belt basin of fi ne- and medium-grained . For- between 1680 and 1820 Ma. The zircons are (Evans et al., 2000). mations sampled and their locations are shown predominantly zoned igneous grains as deter- Whole-rock Nd results show signifi cant in Figure 1. Zircons from nine samples (see mined by CL images. Belt Supergroup–aged scatter (Fig. 4), paralleling Hf results. The Table DR2 in the GSA Data Repository1) were (ca. 1400–1470 Ma) grains represent only 4% of Gunsight and West Fork Formation samples analyzed by a laser ablation–multicollector all grains, and 2400–2700 Ma zircons represent vary signifi cantly (Gunsight εNd [1400 Ma] inductively coupled plasma–mass spectrometer only 7%. A consistent age distribution is found of +1.1; West Fork εNd [1400 Ma] of −5.9), (LA-MC-ICP-MS) at the University of Ari- in every formation sampled and a combined his- despite indistinguishable detrital zircon spec- zona using techniques outlined in Gehrels et al. togram is given in Figure 2 (for individual spec- tra. The range in εNd is far greater than is (2008). Samples from the Gunsight Formation tra, see the Data Repository). recorded in the Mojave and Yavapai provinces (49ES08; location 1c in Fig. 1) and the Mount (Fig. 4; Bennett and DePaolo, 1987) except for Shields Formation (37ES08; location 1c in a small portion of the southern Mojave terrane ε Fig. 1) were reanalyzed on the sensitive high- 200 Qt near Death Valley, California, that includes Nd Relative probability resolution ion microprobe (SHRIMP RG) at 180 (1400) as low as −9.1 (recalculated to 1400 Ma the Australian National University. SHRIMP 160 from Ramo and Calzia, 1998). Despite the low analytical methods were described by Williams 140 Nd values, Death Valley is an unlikely source 120 (1998). SHRIMP data were reduced using the C E for the West Fork Formation. A 500 grain point 100 Frequency I B SQUID Excel macro (Ludwig, 2001) and all 80 count of the West Fork revealed slightly >60% isotope plots prepared using Isoplot/Ex 3.00 60 feldspar (Fig. 2), suggesting a much more (Ludwig, 2003). The SHRIMP analysis pits are 40 F L proximal source. In the northern Mojave ter- ~1–2 µm depth × 20 µm diameter, enabling LA- 20 rane, the Santaquin Complex of central Utah ε MC-ICP-MS Lu-Hf analyses to be carried out 1300 1500 1700 1900 2100 2300 2500 2700 2900 3100 3300 (Fig. 1) has signifi cantly more juvenile Nd on exactly the same location used for the age Age (Ma) (1400 Ma) values, ranging from +3.8 to −2.5 determinations. The LA-MC-ICP-MS meth- (recalculated from Nelson et al., 2002). Figure 2. Composite detrital zircon U-Pb age ods used are similar to those in Munizaga et al. spectrum for 980 zircons from 11 samples of Our new bulk-rock Nd and zircon Hf iso- topic data from Missoula Group and Lemhi Missoula and Lemhi Groups. Inset is quartztotal- 1GSA Data Repository item 2010257, sample feldspar-lithic (Qt-F-L) ternary plot for Mis- Group strata suggest dominant sediment deri- locations; U-Pb, Lu-Hf, and Sm-Nd data; and point soula Group and Lemhi Group detrital zircon vation from an isotopically heterogeneous count results, is available online at www.geosociety samples. For point count data, see the Data .org/pubs/ft2010.htm, or on request from editing@ Repository (see footnote 1). B—West Fork 1680–1820 Ma source, in accord with Ross et geosociety.org or Documents Secretary, GSA, P.O. Formation; C—Big Creek Formation; E—Gun- al. (1991). This source is likely to have been Box 9140, Boulder, CO 80301, USA. sight Formation; I—Mount Shields Formation. proximal: arkosic conglomerates of the Bonner

928 GEOLOGY, October 2010 Downloaded from geology.gsapubs.org on October 2, 2010

20.00 Bonner Formation, 20.00 1708 ± 10 Ma 1716 ± 17 Ma Missoula Group, ε εHf(i) = +0.7 Figure 3. Hf(i) versus 15.00 εHf(i) = +5.7 12ES08 15.00 37ES08 0.1 U-Pb age for Missoula 37ES08 Mount Shields Formation, Depleted Mantle Evolution mm Group and Lemhi Group 10.00 0.25 mm Missoula Group, 11ES08 10.00 zircons. Paleoprotero- Mount Shields Formation, Laurentian A-type granites 1432 ± 16 Ma (Goodge et al., 2008) zoic Missoula and Lemhi 5.00 0.25 mm Missoula Group 5.00 εHf(i) = –7.8 Group zircons are plotted 37ES08 on left, and Mesoprotero- Hf(i) Hf(i) ε 0.00 Gunsight Formation, ε 0.00 zoic zircons from Bon- Lemhi Group, 49ES08 0.1 mm ner Formation (Missoula -5.00 Hoodoo Quartzite, -5.00 Group) are plotted on 02RL888 1429 ± 12 Ma right, relative to A-type εHf(i) = –7.0 -10.00 Yellowjacket Formation, -10.00 magmatic zircons from 13PL01 southwest and central -15.00 -15.00 Laurentia (Goodge and 1650 1675 1700 1725 1750 1775 1800 1300 1400 1500 1600 Vervoort, 2006). U-Pb age (Ma) U-Pb age (Ma)

0.00 mas, and so may have provided some detritus. River Complex (Doughty et al., 1998) with the 1 However, the northern Mojave terrane lacks Gawler Range Volcanics of South Australia -5.00 2 the more evolved spread in Nd isotope values (Fanning et al., 1988). 3 found in the Lemhi Group. Thus, an additional Alternatively, sediment could have come -10.00 source is required. from 1.73–1.70 Ga anorogenic magmas that C melted Archean basement in the Ulkan Com- -15.00 H E F Nd(0) D G B PALEOGEOGRAPHIC IMPLICATIONS plex and Okhotsk Massif (Khudoley et al., ε -20.00 Province 3 A Peucat et al. (1999) reported 2.6 and 2.8 Ga 2007) of Siberia (Sears and Price, 2003) Province 2 inherited zircons, 1.73–1.76 Ga magmatism, (Fig. 5). Sedimentary characteristics suggest- -25.00 Province 1 oic and 1.69 Ga migmatization in Terre Ade- ing a proximal source, combined with a lack lie Land, East Antarctica (Fig. 1). They also of 1.85–2.0 Ga detrital zircons, make the Sibe- Proteroz -30.00 Archean reported εNd values on ca. 1.7 Ga basement rian model less preferred. Furthermore, this 0.080 0.090 0.100 0.110 0.120 0.130 0.140 gneisses that, when recalculated to 1400 Ma, reconstruction is not considered likely due to 147 144 Sm/ Nd range from −3.5 to −7.1. These values are simi- the abrupt truncation of the ca. 1.4 Ga Lauren- Figure 4. εNd(0) versus 147Sm/144Nd for fi ve lar to the more negative εNd values from the tian A-type magmatic belt, and its placement bulk rock samples from Lemhi Group and Lemhi Group. Sediment mixing between the of 1.7 Ga rifting in the Okhotsk Massif (Khu- three samples from Missoula Group. A—Yel- lowjacket Formation, B—West Fork Forma- northern Mojave terrane and basement simi- doley et al., 2007) adjacent to coeval orogen- tion, C—Big Creek Formation, D—type lar to that found in Terre Adelie could account esis in southwest Laurentia. Gunsight Formation (location 1d in Fig. 1), for the spread in εNd values for the Lemhi E—Gunsight Formation (location 1c in and Missoula Groups while maintaining con- Fig. 1), F—Mount Shields Formation, G— sistent detrital zircon spectra. It is likely that Mount Shields Formation from Frost and 1.7 Ga crust extends southward from Terre Winston (1987), H—Snowslip Formation from Siberia

Frost and Winston (1987). Province boundar- Adelie toward southern Victoria Land and the 400 km. 400 ies are from Bennett and DePaolo (1987). central Transantarctic Mountains (Goodge et BP al., 2001). The 1.7 Ga magmatic event in Ant- Anabar UB Province GFTZ arctica may have been part of a larger orogen AZ L Formation from the Pioneer Mountains, south- that included the Gawler craton (Australia) and 2.0–1.8 Ga Orogenic Belt western Montana, contain abundant angular the Mojave terrane (Goodge et al., 2001). This potassium feldspar grains as long as 3 cm. Point large proposed orogenic event with accompa- Aldan Laurentia counts (n = 500) for Missoula Group and Lemhi nying magmatism is a good candidate for the Province Group formations plotted on a -feldspar- extensive magmatic terrane that fed the upper M lithic ternary diagram (Fig. 2) also suggest a Belt Supergroup and Lemhi Group. proximal source; three formations have >50% The paleogeographic fi t of Figure 1 is simi- A feldspar (Gunsight, Big Creek, and Mount lar to the revised SWEAT model of Goodge et Shields) and one formation has >60% feldspar al. (2008), though it shifts the East Antarctic UC OM (West Fork). A nearby Paleoproterozoic mag- and Australian continents southward relative to matic arc developed within Archean crust could Laurentia by several hundred kilometers. It still produce the observed distribution of age, iso- keeps fundamental ties between the Mojave Figure 5. Alternative paleogeographic re- construction modifi ed from Sears and topic, and sedimentologic characteristics. Our province and the central Transantarctic Moun- Price (2003) with possible Belt Supergroup data suggest that the Mojave and Yavapai ter- tains, and the inferred 1370–1475 Ma A-type sediment sources including Okhotsk Massif ranes, at least those portions intruded by 1400– granite belt of Antarctica (Goodge et al., 2008) (OM), Ulkan Complex (UC), and Mojave ter- 1470 Ma magmas, were not responsible for with southwest Laurentia. In addition to pro- rane (M). A—1.47–1.37 Ga Laurentian A-type magmatism; boundary is marked by dashed the bulk of upper Belt Supergroup and Lemhi viding a viable sediment source for the Mis- line; BP—Belt-Purcell Supergroup; L— Group detritus. The northernmost Mojave ter- soula and Lemhi Groups, it has the advantage Lemhi Group; UB—Udzha Basin; AZ—Aekit rane was not intruded by 1400–1470 Ma mag- of linking 1580 Ma magmatism in the Priest zone; GFTZ—Great Falls Tectonic Zone.

GEOLOGY, October 2010 929 Downloaded from geology.gsapubs.org on October 2, 2010

ACKNOWLEDGMENTS Frost, C.D., Barnes, C.G., and Snoke, A.W., 2006, Munizaga, F., Maksaev, V., Fanning, C.M., Giglio, S., This work was supported by National Science Foun- Nd and Sr isotopic data from argillaceous rocks Yaxley, G., and Tassinari, C.C.G., 2008, Late dation grant 08-19884 and U.S. Geological Survey of the Galice Formation and Rattlesnake Creek Paleozoic–Early Triassic magmatism on the EdMap 08-HQAG0042 to Link, and student grants to terrane, Klamath Mountains: Evidence for the western margin of Gondwana: Collahuasi area, Stewart from the Geological Society of America (8836- input of sources, in Snoke, A.W., northern Chile: Gondwana Research, v. 13, 08), the Society of Economic Geologists, the Tobacco and Barnes, C.G., eds., Geological studies in p. 407–427, doi: 10.1016/j.gr.2007.12.005. Root Geological Society, the Belt Association, and the the Klamath Mountains province, California Nelson, S.T., Harris, R.A., Dorais, M.J., Heizler, Idaho State Graduate Research and Scholarship Com- and Oregon: A volume in honor of William P. M., Constenius, K.N., and Barnett, D.E., 2002, mittee. Frost thanks J. Mailloux for technical assistance Irwin: Geological Society of America Special Basement complexes in the Wasatch , with the Nd isotopic analyses. Reviews by M. Pope, D. Paper 410, p. 103–120. Utah, provide new limits on crustal accretion: Coleman, D. Winston, R. Lewis, and several anony- Gehrels, G.E., Valencia, V.A., and Ruiz, J., 2008, En- Geology, v. 30, p. 831–834, doi: 10.1130/0091 mous reviewers improved the manuscript. hanced precision, accuracy, effi ciency, and spatial -7613(2002)030<0831:BCITWF>2.0.CO;2. resolution of U-Pb ages by laser ablation-multi- Peucat, J.J., Menot, R.P., Monnier, O., and Fanning, REFERENCES CITED collector-inductively coupled plasma-mass spec- C.M., 1999, The Terre Adelie basement in the Bennett, V.C., and DePaolo, D.J., 1987, Proterozoic trometry: Geochemistry Geophysics Geosystems, East Antarctica Shield: Geological and isoto- crustal history of the western United States as v. 9, no. 3, Z03017, doi: 10.1029/2007GC001805. pic evidence for a major 1.7 Ga thermal event; determined by neodymium isotope mapping: Goodge, J.W., and Vervoort, J.D., 2006, Origin of comparison with the Gawler Craton in South Geological Society of America Bulletin, v. 99, Mesoproterozoic A-type granites in Laurentia: Australia: Precambrian Research, v. 94, p. 205– p. 674–685, doi: 10.1130/0016-7606(1987)99 Hf isotope evidence: Earth and Planetary Sci- 224, doi: 10.1016/S0301-9268(98)00119-3. <674:PCHOTW>2.0.CO;2. ence Letters, v. 243, p. 711–731, doi: 10.1016/j Ramo, O.T., and Calzia, J.P., 1998, Nd isotopic Blewett, R., Black, L.P., Sun, S.-S., Knutson, J., .epsl.2006.01.040. composition of cratonic rocks in the southern Hutton, L.J., and Bain, J.H., 1998, U-Pb zir- Goodge, J.W., Fanning, C.M., and Bennett, V.C., Death Valley region: Evidence for a substan- con and Sm-Nd geochronology of the Meso- 2001, U-Pb evidence of ~1.7 Ga crustal tec- tial Archean source component in Mojavia: proterozoic of North Queensland; implications tonism during the Nimrod Orogeny in the Geology, v. 26, p. 891–894, doi: 10.1130/0091 for a Rodinian connection with the Belt Su- Transantarctic Mountains, Antarctica: Impli- -7613(1998)026<0891:NICOCR>2.3.CO;2. pergroup of North America: Precambrian Re- cations for Proterozoic plate reconstructions: Ross, G.M., and Villeneuve, M., 2003, Provenance search, v. 89, p. 101–127, doi: 10.1016/S0301 Precambrian Research, v. 112, p. 261–288, doi: of the Mesoproterozoic (1.45 Ga) Belt Basin -9268(98)00030-8. 10.1016/S0301-9268(01)00193-0. (western North America): Another piece in Cressman, E.R., 1989, Reconnaissance stratigraphy Goodge, J.W., Vervoort, J.D., Fanning, C.M., Brecke, the pre-Rodinia paleogeographic puzzle: Geo- of the Prichard Formation (Middle Protero- D.M., Farmer, G.L., Williams, I.S., Myrow, logical Society of America Bulletin, v. 115, zoic) near Plains, Sanders Country, Montana: P.M., and DePaolo, D.J., 2008, A positive test of p. 1191–1217, doi: 10.1130/B25209.1. U.S. Geological Survey Professional Paper East Antarctica–Laurentia juxtaposition within Ross, G.M., Parrish, R.R., and Dudás, F.O., 1991, 1490, 80 p. the Rodinia supercontinent: Science, v. 321, Provenance of the Bonner Formation (Belt Dickinson, W.R., 2008, Impact of differential zircon p. 235–240, doi: 10.1126/science.1159189. Supergroup), Montana: Insights from U-Pb fertility of granitoid basement rocks in North Harrison, J.E., Griggs, A.B., and Wells, J.D., 1974, and Sm-Nd analyses of detrital minerals: Ge- America on age population of detrital zircons Tectonic features of the Precambrian Belt ba- ology, v. 19, p. 340–343, doi: 10.1130/0091 and implications for granite petrogenesis: sin and their infl uence on post-Belt structures: -7613(1991)019<0340:POTBFB>2.3.CO;2. Earth and Planetary Science Letters, v. 275, U.S. Geological Survey Professional Paper Ruppel, E.T., 1975, Precambrian Y sedimentary p. 80–92, doi: 10.1016/j.epsl.2008.08.003. 866, 15 p. rocks in east-central Idaho: U.S. Geological Doughty, P.T., and Chamberlain, K.R., 1996, Khudoley, A.K., Kropachev, A.P., Tkachenko, V.I., Survey Professional Paper 889-A, 23 p. Salmon River Arch revisited: New evidence for Rublev, A.G., Sergeev, S.A., Matukov, D.I., and Sears, J.W., and Price, R.A., 2003, Tightening the Si- 1370 Ma rifting near the end of deposition in Lyahnitskaya, O.Y., 2007, Mesoproterozoic to berian connection to western Laurentia: Geo- the Middle Proterozoic Belt basin: Canadian Neoproterozoic evolution of the Siberian Cra- logical Society of America Bulletin, v. 115, Journal of Earth Sciences, v. 33, p. 1037–1052. ton and adjacent microcontinents: An overview p. 943–953, doi: 10.1130/B25229.1. Doughty, P.T., Price, R.A., and Parrish, R.R., 1998, with constraints for a Laurentian connection, in Sears, J.W., Chamberlain, K.R., and Buckley, S.N., Geology and U-Pb geochronology of Archean Link, P.K., and Lewis, R.S., eds., Proterozoic 1998, Structural and U-Pb geochronological basement and Proterozoic cover in the Priest geology of western North America and Sibe- evidence for 1.47 Ga rifting in the Belt basin, River complex, northwestern United States, and ria: SEPM (Society for Sedimentary Geology) western Montana: Canadian Journal of Earth their implications for Cordilleran structure and Special Publication 86, p. 209–226. Sciences, v. 35, p. 467–475, doi: 10.1139/cjes Precambrian continent reconstructions: Cana- Kinny, P.D., and Maas, R., 2003, Lu-Hf and Sm-Nd -35-4-467. dian Journal of Earth Sciences, v. 35, p. 39–54, isotope systems in zircon: Reviews in Mineral- Williams, I.S., 1998, U-Th-Pb geochronology by ion doi: 10.1139/cjes-35-1-39. ogy and Geochemistry, v. 53, p. 327–341, doi: microprobe, in McKibben, M.A., et al., eds., Evans, K.V., Aleinikoff, J.N., Obradovich, J.D., and 10.2113/0530327. Applications of microanalytical techniques Fanning, C.M., 2000, SHRIMP U-Pb geochro- Li, Z.X., and 16 others, 2008, Assembly, confi gura- to understanding mineralizing processes: Re- nology of volcanic rocks, Belt Supergroup, tion, and break-up history of Rodinia: a synthe- views in Economic Geology, v. 7, p. 1–35. western Montana; evidence for rapid deposi- sis: Precambrian Research, v. 160, p. 179–210, Winston, D., 1986, Sedimentation and tectonics of tion of sedimentary strata: Canadian Journal of doi: 10.1016/j.precamres.2007.04.021. the Middle Proterozoic Belt basin, and their Earth Sciences, v. 37, no. 9, p. 1287–1300, doi: Link, P.K., Fanning, C.M., Lund, K.I., and Aleini- infl uence on compression and 10.1139/cjes-37-9-1287. koff, J.N., 2007, Detrital zircons, correlation extension in western Montana and northern Fanning, C.M., Flint, R.B., Parker, A.J., Ludwig, and provenance of Mesoproterozoic Belt Super- Idaho, in Peterson, J.A., ed., Paleotectonics and K.R., and Blissett, A.H., 1988, Refi ned Pro- group and correlative strata of east-central Idaho sedimentation in the Rocky Mountain region, terozoic evolution of the Gawler Craton, South and southwest Montana, in Link, P.K., and United States: American Association of Petro- Australia, through U-Pb zircon geochronology: Lewis, R.S., eds., Proterozoic geology of west- leum Geologists Memoir 41, p. 87–118. Precambrian Research, v. 40–41, p. 363–386, ern North America and Siberia: SEPM (Society Winston, D., Link, P.K., and Hathaway, N., 1999, The doi: 10.1016/0301-9268(88)90076-9. for Sedimentary Geology) Special Publication Yellowjacket is not the Prichard and other here- Foster, D.A., Mueller, P.A., Mogk, D.W., Wooden, 86, p. 101–128. sies: Belt Supergroup correlations, structure and J.L., and Vogl, J.J., 2006, Proterozoic evolution Ludwig, K.R., 2001, SQUID 1.02, A user’s manual: paleogeography, east-central Idaho, in Hughes, of the western margin of the Wyoming craton: Berkeley, California, Berkeley Geochronology S.S., and Thackray, G.D., eds., Guidebook to Implications for the tectonic and magmatic Center Special Publication 2. the geology of eastern Idaho: Pocatello, Idaho, evolution of the northern Rocky Mountains: Ludwig, K.R., 2003, Isoplot/Ex version 3.0: A geo- Museum of Natural History, p. 3–20. Canadian Journal of Earth Sciences, v. 43, chronological toolkit for Microsoft Excel: p. 1601–1619, doi: 10.1139/E06-052. Berkeley, California, Berkeley Geochronology Frost, C.D., and Winston, D., 1987, Nd isotope sys- Center Special Publication 4. Manuscript received 8 March 2010 tematics from coarse- and fi ne-grained sedi- Moores, E.M., 1991, Southwest U.S.–East Antarctic Revised manuscript received 12 May 2010 ments: Examples from the Middle Proterozoic (SWEAT) connection: A hypothesis: Geology, Manuscript accepted 21 May 2010 Belt-Purcell Supergroup: Journal of Geology, v. 19, p. 425–428, doi: 10.1130/0091-7613( v. 95, p. 309–327, doi: 10.1086/629132. 1991)019<0425:SUSEAS>2.3.CO;2. Printed in USA

930 GEOLOGY, October 2010