Sequence stratigraphy and formalization of the Middle

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Precambrian Research 236 (2013) 65– 84

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Precambrian Research

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equence stratigraphy and formalization of the Middle Uintaountain Group (Neoproterozoic), central Uinta Mountains, Utah:

closer look at the western Laurentian Seaway at ca. 750 Ma

sther M. Kingsbury-Stewarta,∗, Shannon L. Osterhouta,1, Paul K. Linka, Carol M. Dehlerb

Department of Geosciences, M.S. 8072, Idaho State University, Pocatello, ID 83209, United StatesDepartment of Geology, 4505 Old Main Hill, Utah State University, Logan, UT 83422, United States

r t i c l e i n f o

rticle history:eceived 3 November 2012eceived in revised form 18 June 2013ccepted 20 June 2013vailable online 19 July 2013

eywords:eoproterozoicinta Mountain Groupodiniaaurentiaequence stratigraphyetrital zircon

a b s t r a c t

The mid-Neoproterozoic (ca. 750 Ma) Uinta Mountain Group (UMG), northeast Utah, USA, records trans-gressions of an epicontinental sea at least 150 million years before inception of the Laurentian westernpassive margin. This work refines middle UMG stratigraphy by formalizing three lithostratigraphicformations and interpreting a sequence stratigraphic framework in the central part of the Uinta Moun-tains. Middle UMG marine and fluvial-deltaic facies associations comprise eight depositional sequenceswithin a kilometer-thick upward-fining composite sequence. These depositional sequences form oneprogradational–aggradational (“lowstand”) sequence set (PASS) and one aggradational–progradational(“highstand”) sequence set (APSS). Depositional sequences were deposited within a tide- and wave-affected epicontinental seaway that received sediment from a south-flowing fluvial system proximallysourced in the Neoarchean southern Wyoming Province to the north and from a separate system of major,west-flowing trans-Laurentian rivers distally sourced in the Grenville orogen, the mid-continent graniteprovince, and the Yavapai and Mazatzal provinces to the south and east.

Middle UMG fluvial-marine paleogeography strengthens the genetic link with the coeval Big Cotton-wood and Little Willow formations (Utah), the Chuar Group (Arizona), and upper Pahrump Supergroup(California), which collectively indicate a ca. 770–740 Ma epicontinental seaway existed across much ofwestern Laurentia before 700 Ma rifting and 600 Ma formation of the Cordilleran passive margin. Long-term marine transgression onto continental Laurentia was likely caused by supercontinent breakup,particularly rifting of the Tarim and South China blocks from the remainder of Rodinia. Poorly con-
strained autocyclic drivers (delta lobe switching, channel avulsion) and allocyclic drivers (climaticfluctuations, local tectonism) controlled higher frequency depositional cycles superimposed on this long-term transgression. Western Laurentia thus records prolonged (750–600 Ma) episodic basin formation,mafic volcanism, and faulting before establishment of a continental terrace after 600 Ma. The Neopro-terozoic western Laurentian epicontinental seaway can be used as a tie-point with other continents tohelp constrain the original continental configuration of Rodinia.
Published by Elsevier B.V.

. Introduction

The pioneering Powell, King, and Hayden geological surveys ofhe mid 1800s first documented the Precambrian Uinta Mountain

∗ Corresponding author at: Wisconsin Geologic and Natural History Survey, Madi-on, WI, United States. Tel.: +1 608 263 3201; fax: +1 608 262 8086.

E-mail addresses: [email protected] (E.M. Kingsbury-Stewart),[email protected] (S.L. Osterhout), [email protected] (P.K. Link),[email protected] (C.M. Dehler).

1 Currently with Pioneer Natural Resources, Denver, CO. Research completedhile at Idaho State University.

301-9268/$ – see front matter. Published by Elsevier B.V.ttp://dx.doi.org/10.1016/j.precamres.2013.06.015

Group2 (UMG), northeast Utah, USA (Fig. 1), making these rocksamong the longest recognized stratigraphic units in North Amer-ica (Powell, 1876; Emmons, 1877). Despite its superb exposure,UMG stratigraphy (and therefore paleogeography) is only grosslyresolved, due to remote location, great thickness, lithologic repe-tition and related lack of marker units or other regional timelines.Over 2 km of the middle part of the UMG are exposed in the area of
Kings Peak, Mount Powell, and Red Castle on the crest of the UintaMountain anticline (Figs. 1 and 2; Bryant, 1992). Lateral and ver-tical facies relationships and stratal geometries define a hierarchy
2 Uinta Mountain Group (UMG).

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66 E.M. Kingsbury-Stewart et al. / Precambrian Research 236 (2013) 65– 84

Fig. 1. (A) Regional geologic map of Uinta Mountains, showing Kings Peak andMount Powell quadrangles, and localities mentioned in the text. Modified afterHaddox et al. (2005). (B) Simplified geologic map of north-central Uinta Mountains inthe area of the Kings Peak and Mount Powell quadrangles. Boxes locate stratigraphicsections shown in Fig. 5. Triangles locate major mountain peaks. Zuc = Red Castle For-mation; Zuda = Dead Horse Pass and Mount Agassiz formations; Zuh = formation ofHPO

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Fig. 2. Photopanel of the east wall of the Henry’s Fork drainage above Dollar Lakeshowing stratal geometry and stratigraphic units. The box shows the zoomed-in

ades Pass. Base from D. Sprinkel, Utah Geological Survey, unpublished, with Kingseak and Mount Powell quadrangles simplified from our mapping (Kingsbury, 2008;sterhout, 2011).

f marine and marine through fluvial-deltaic successions that arexposed, often in three dimensions, above tree line along later-lly continuous (km-scale) cirque walls along the crest of the Uintaountains (Figs. 1 and 2). These exposures are only found in the

emote parts of the range and offer insight into the more detailedature of the UMG strata, therefore enhancing paleoenvironmentalnd paleogeographic understanding of the UMG.

Our goal is to integrate several independent observations fromhe middle UMG in the middle part of the Uinta Mountain rangencluding detrital zircon age spectra, lithofacies and facies associ-tions, vertical stacking patterns, and stratal architecture exposedn outcrop to resolve the lithostratigraphy and sequence stratig-aphy of the middle UMG. Specifically, we (1) formalize threeeologic units (the Red Castle, Dead Horse Pass and Mount Agassizormations) to facilitate stratigraphic understanding of the Neo-roterozoic section in the Uinta Mountains; (2) characterize UMGtratigraphy in terms of a hierarchy of accommodation-successionsensu Neal and Abreu, 2009); and (3) integrate these new data intohe regional understanding of the Neoproterozoic paleogeographyf western Laurentia.

. Geologic setting

The upper Precambrian (Neoproterozoic, Cryogenian) Uintaountain Group contains up to 7 km of mainly red-colored

andstone and mudrock, and is only exposed in the Uinta Moun-ains of northern Utah (Hansen, 1965;Fig. 1). Previous workersave suggested deposition in an intracratonic half-graben withn east-west-trending northern margin (Hansen, 1965; Ball and

area. The arrow points towards south. DS = Depositional sequence. Zuc: Red CastleFormation; Zud: Dead Horse Pass Fm.; Zuma: Mount Agassiz Fm.

Farmer, 1998; Condie et al., 2001; Dehler et al., 2010). The activenorthern margin of the half-graben was bounded by reactivatedstructures along or south of the southern edge of the ArcheanWyoming Province (Sears et al., 1982; Bryant and Nichols, 1988;Stone, 1993; Nelson et al., 2002, 2011). Neoproterozoic normalfaulting accompanied UMG deposition (Brehm, 2008; Kingsbury,2008; Rybczynski, 2009). Paleomagnetic studies suggest a near-equatorial paleolatitude (Weil et al., 2004, 2006).

Latest Neoproterozoic to early Cambrian normal faulting tiltedand uplifted the UMG prior to deposition of Paleozoic strata (Stone,1993; Bryant, 1992). Extensional structures within the UMG basinwere inverted during Paleozoic contractional events, for examplethe late Pennsylvanian – early Permian Ancestral Rocky Moun-tains orogeny (Stone, 1993). Structural inversion and growth ofthe modern Uinta Mountains culminated in the Late Cretaceous tomid-Cenozoic Laramide orogeny (Bradley, 1995; DeCelles, 2004).

The UMG unconformably overlies Paleoproterozoic metamor-phic rocks along the northeastern edge of the Uinta Mountains(Hansen, 1965; Sears et al., 1982), but the base is not exposed inthe west (e.g., Wallace, 1972). Cambrian or Mississippian strataunconformably overlie the UMG (Hansen, 1965).

The quartzose and arkosic UMG has been interpreted as asand-dominated, fluvial (Sanderson, 1978, 1984; Condie et al.,2001); fluvial-marine (Wallace and Crittenden, 1969; Wallace,1972; Dehler et al., 2010), or fluvial-lacustrine (Link, 1993; Winstonand Link, 1993) system within an elongate basin that opened to the
west and south (e.g. Hansen, 1965; Wallace and Crittenden, 1969;Dehler et al., 2010). The UMG contains three, km-thick, upward-fining composite sequences (depositional sequences of Dehler et al.,2010; Fig. 3). The lower composite sequence is only exposed in the

E.M. Kingsbury-Stewart et al. / Precambrian Research 236 (2013) 65– 84 67

Fig. 3. Generalized stratigraphic columns from the eastern and western UintaMountains. Composite sequence boundaries divide the Uinta Mountain Groupinto three major composite sequences. Abbreviations: CS, composite sequence;CSB, composite sequence boundary; CTS, composite transgressive surface; Deadhs.,Deadhorse Pass Formation; lower RC, lower member of the Red Castle Formation;middle RC, middle member of the Red Castle Formation; Moosehorn, formation ofMoosehorn Lake; Mt. Ag., Mount Agassiz Formation; Mt. W., Mount Watson Forma-tD

eatTzoaeowo2nMtPoomtitDw

Fig. 4. Simplified stratigraphic columns of Kings Peak and Mount Powell quad-

2005). We here adopt and formalize the Red Castle, Dead Horse

ion; upper RC, upper member of the Red Castle Formation. Figure modified fromehler et al. (2010).

astern part of the range, some 100–160 km southeast of the studyrea, and includes the conglomeratic Jesse Ewing Canyon Forma-ion and the informal formations of Diamond Breaks and Outlawrail (De Grey, 2005; De Grey and Dehler, 2005). One detrital-ircon sample from the Outlaw Trail unit contains four zircons (outf ∼128 total grains) with ages of 726 ± 56; 721 ± 54; 804 ± 46;nd 801 ± 52 Ma (see data repository of Dehler et al., 2010). Dehlert al. (2010) report these grains to be within analytic uncertaintyf each other with a concordia age of 766 ± 4.8 Ma (mean square ofeighted deviates is 0.66), which is the best (and only) constraint

n the maximum age of the entire Group (Fig. 3; Dehler et al., 2007,010). Other ca. 800 Ma detrital zircons have been found in smallumbers in the Jesse Ewing Canyon Formation and the formation ofoosehorn Lake (Dehler et al., 2010; Fig. 3). Composite sequence

wo, the focus of this paper, includes the Red Castle, Dead Horseass, and Mount Agassiz formations, which make up the high spinef central part of the range (Figs. 3 and 4), the informal formationf Moosehorn Lake (not exposed in the study area), and the infor-al formation of Crouse Canyon in the east. Composite sequence

hree includes the informal formation of Hades Pass and the overly-ng Red Pine Shale, which contains microfossil assemblages similar
o those found in the Chuar Group in the Grand Canyon (Fig. 3;ehler et al., 2007). Correlation of the UMG with the Chuar Group,hich contains an ash bed with an age of 742 ± 6 Ma (Karlstrom
rangles showing formally defined Red Castle, Dead Horse Pass, and Mount Agassizformations and sequence stratigraphic terminology used in this paper.

et al., 2000) provides a young age-bound for the upper compositesequence (Dehler et al., 2001a).

The UMG has long been thought to be correlative with the partlytidal Big Cottonwood Formation (Wallace and Crittenden, 1969;Crittenden and Wallace, 1973; Link, 1993; Chan et al., 1994; Ehlerset al., 1997; Ehlers and Chan, 1999; Dehler et al., 2001b, 2010;Link and Christie-Blick, 2011) and has recently been shown to alsobe correlative with the metamorphosed Little Willow Formation(Spencer et al., 2012) in the Wasatch Range of northern UT. Neo-proterozoic ages (750–850 Ma) from detrital zircons in the LittleWillow Formation and similar detrital zircon age populations fromthe Little Willow and Big Cottonwood formations of the WasatchRange support this correlation (Spencer et al., 2012).

3. Formalization of units

Previous work in the UMG (Wallace and Crittenden, 1969;Wallace, 1972; Sanderson, 1978) established informal stratigraphicunits (i.e. “formation of Red Castle”) that were not formallydefined to the specifications of the North American StratigraphicCode (North American Commission on Stratigraphic Nomenclature,

Pass, and Mount Agassiz formations (Tables 1 and 2, Data Reposi-tory Appendices 1 and 2). These formal units are used in geologicmaps of the western UMG, including the Salt Lake 1◦ by 2◦,


Table 1Table showing the development of the stratigraphic nomenclature for the western Uinta Mountain Group. Each column represents a publication (bold text) that first informallynamed or formalized a lithostratigraphic unit in the western UMG. The units that each publication discusses, whether first informally or formally defined or simply adoptedfrom previous studies, are listed in the column under the publication. Formalization of an informal unit by a subsequent study is indicated by the name change from ‘formationof. . .’ to ‘. . . Formation’. For example, Sanderson (1978) formalized the Mount Watson Formation, which was first informally defined by Wallace (1972) and Crittenden andWallace (1973). The relationship between lithostratigraphic and sequence stratigraphic units is also shown.

Williams (1953) Wallace (1972), andCrittenden and Wallace(1973)

Sanderson (1978) This study Sequence stratigraphichierarchy* ,+ see Figs. 3–5

Red Pine Shale Red Pine Shale Red Pine Shale Red Pine Shale Composite sequence 3formation of Hades Pass formation of Hades Pass formation of Hades Pass formation of Hades Pass Composite sequence 3

formation of MountWatson

Mount Watson Formation Mount Watson Formation Composite sequence 2

formation of MountAgassiz

Mount Watson Formation Mount Agassiz Formation Composite sequence 2

Depositional sequences 6-8formation of Dead HorsePass

Mount Watson Formation Dead Horse Pass Formation Composite sequence 2

Depositional sequences 4–5formation of MoosehornLake

formation of MoosehornLake


Composite sequence 2

Uinta Mountain Groupundivided



formation of Red Castle formation of Red Castle Red Castle Formation(upper member)


Depositional sequences 3–6Red Castle Formation(middle member)


Depositional sequence 3Red Castle Formation(lower member)


includes Island Lakequartzite tongues

Depositional sequences 1–2

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* sensu Neal and Abreu (2009).+ Composite sequences revised from Depositional sequences of Dehler et al. (201

ings Peak 7.5′, and Mount Powell 7.5′ quadrangles (Bryant, 1992;ingsbury, 2008; Osterhout, 2011, respectively). Reference sectionsre shown in Fig. 5 and described in Appendices 1 and 2 in theata Repository. We did not formalize the formation of Hades Passecause it is not fully exposed within the study area. Sequencetratigraphic surfaces and geometries referenced in this section areormally presented under section 5.

.1. Red Castle Formation

The Red Castle Formation is subdivided into three informalembers and contains at least 735 m of reddish, conglomeratic,

eldspathic arenite and subordinate siltstone. The lower memberontains at least 150 m of arkosic sandstone (up to 50% k-feldspar)nd several meters-thick, tabular quartz arenite interbeds that wenformally name the Island Lake quartzite tongues (Figs. 4 and 5).he base is not exposed. The middle member contains at least75 m of tabular-bedded arkosic sandstone and sparse quartzrenite interbeds. The upper member contains at least 350 m ofpward-coarsening mudstone through lenticular-bedded arkosicandstone. The upper member of the Red Castle Formation under-oes a facies change to the east, grading into finer-grainedediments of the Dead Horse Pass and Mount Agassiz formationsFig. 5). In the west an erosive contact separates tabular-bedded,rkosic arenite (tabular arkose lithofacies, see Section 5.1, Table 3,ig. 5) of the upper member from lenticular-bedded sub-arkosico quartz arenite (lenticular quartzose lithofacies, see Section 5.1,able 3, Fig. 5) of the overlying formation of Hades Pass.

.2. Dead Horse Pass Formation

The Dead Horse Pass Formation contains at least 150 m ofpward-coarsening mudstone, through tabular-bedded quartz

arenite. The basal contact of the Dead Horse Pass Formation andthe equivalent upper member, Red Castle Formation is a map-pable stratigraphic discontinuity (composite transgressive surface1, see Section 5, Fig. 5) that separates fine-grained strata above,from coarse-grained, angular, poorly sorted arkosic sandstone,below.

3.3. Mount Agassiz Formation

The Mount Agassiz Formation (159 m) overlies the Dead HorsePass Formation, contains upward-coarsening mudstone throughtabular quartz arenite, and is generally finer-grained than theunderlying Dead Horse Pass Formation. The basal contact is a strataldiscontinuity (SBe; Fig. 5, see Section 5, Sequence Stratigraphy)overlain by a distinctive, red- weathering siltstone at its type local-ity (Table 2). The Mount Agassiz Formation undergoes a facieschange, grading westward into red, coarser- grained, feldspathicsandstone and siltstone of the upper part of the upper member,Red Castle Formation. The top of the Mount Agassiz Formation andthe upper member, Red Castle Formation is a regionally mappable,stratal discontinuity (composite sequence boundary 3, Fig. 5, seeSection 5) that incises underling strata and is overlain by coarse-grained, pebbly, lenticular-bedded quartzose sandstone of the baseof the formation of Hades Pass.

4. Detrital zircons

To determine the provenance of the middle UMG, we obtainedLaser Ablation Inductively Coupled Plasma Mass Spectrometer (LA-
ICP MS) detrital zircon data from five new samples from diverselithofacies (described in detail below under Section 5) in the centralUinta Mountains (Supplementary Table S1). New samples includetwo from the Island Lake quartzite tongue of the lower member,


Table 2Formalization of units.

Name Red Castle Formation

Name derivation Type area located near the Red Castle; Smiths Fork basin; Mount Powell quadrangleCategory & rank lithostratigraphic FormationType area Head of Smiths Fork basin, near the Red Castle (Wallace, 1972). The type location for the Island Lake quartzite tongue is Island

Lake in the Mount Powell quadrangle (12T0550780 4518713 elev. 10854).Unit & boundary reference section - W. and NW of the Red Castle

- UTM 12 T 0544630 4516405; 12 T 0543704 4516517; 12 T 0542704 4519264- Lower boundary: unexposed- Upper boundary: erosive surface (CSB 3) separating the Red Castle Formation (below) and formation of Hades Pass (above).- W. boundary: gradational into the Mount Watson Formation- E. boundary: gradational contact with the Dead Horse Pass and Mount Agassiz formations

Lower boundary reference location Unexposed lower boundaryUnit description Divided into 3 informal members: (1) lower member: meters-thick interbeds of arkose and quartz arenite. Arkose is red to

purple, texturally and compositionally immature and organized in decimeter-thick, lenticular beds with erosive, concavebases that pinch into sharp, planar top surfaces rarely capped by cm-thick, planar laminated, sandy siltstone. Quartz arenite iseither (a) purple to tan, well to subrounded, well sorted, medium- to coarse-grained, quartz to subarkosic with lesser siltysandstone and sandy siltstone and organized in tabular to broadly lenticular or sigmoidal beds; or (b) purple to tanfine-grained sandstone that fines upward into siltstone and occasionally is capped by cm-thick shale. The base of the lowermember is not exposed. The top of the member is sharp (erosive) to gradational into the middle member. The contact isplaced (when not eroded away) at the first laterally continuous red, silty shale between lenticular arkosic and tabular arkosicarenite; (2) middle member: arkose and rare fine-grained interbeds. Arkose is laterally continuous (100s of meters), tabular,upward-fining, texturally and compositionally immature, 10 to 50cm-thick, red to purple arkose/gray silt couplets with sharpupper and basal contacts. Mud rip-up clasts and occasional 0.5 to 1 cm scale euhedral feldspar clasts are common, especiallyat the base of couplets. Fine-grained interbeds are laterally continuous (10s to 100s of meters), decimeter- to meters-thick,black to green, laminated clay-shale to siltstone and lesser fine-grained, wavy-laminated sandstone and a low diversity fossilassemblage of acritarchs Leiosphaeridia sp. and organic filaments or black to tan, fine-grained, parallel and wavy laminated orhummocky cross stratified sandstone and siltstone with lesser clay-shale.The upper contact of the middle member is sharp toerosional with the upper member. The contact is placed between tabular arkoisc arenite beds and the first purple maturequartz arenite or dark green interbedded fine-grained sandstone and sandy siltstone; (3) upper member: similar to middlemember except fine-grained interbeds are thicker and more common.

Dimensions Greater than 720 m (Wallace, 1972), greater than 735 m at reference sectionGeologic age Neoproterozoic (∼740–770 Ma, Dehler et al., 2010)Correlations The Red Castle Formation may pass into the Mount Watson Formation (W. Uinta Mountain Group)

Name Dead Horse Pass Formation Mount Agassiz Formation

Name derivation Dead Horse Pass, between the Blacks Fork and Rock Creekbasin, W. Uinta Mountains, Explorer Peak quadrangle

Mount Agassiz, a prominent peak at the head of the east fork ofthe Duchesne River, W. Uinta Mountains, Hayden Peakquadrangle

Category/rank Lithostratigraphic Formation Lithostratigraphic FormationType area 1.5 km south of Dead Horse Pass, head of Rock Creek

(Wallace, 1972)Range crest between the Duchesne and Uinta Rivers (Wallace,1972)

Unit & boundary reference section - S. flank, Gilbert Peak (UTM 12 T 0554681/4519960 NAD27)

- S. flank, Gilbert Peak (UTM: 12 T 0554681/4519960 NAD 27)

- Lower boundary: erosive surface (CTS1, see Fig. 5) - Lower boundary: sharp/erosive surface (SB e)- Upper boundary: sharp/erosive surface (SB e, see Fig. 5) - Upper boundary: sharp/erosive surface (CSB 3, see Fig. 5)

below fm. Hades Pass- W. boundary: gradational into upper member, Red CastleFm.

- W. boundary: gradational into upper mbr., Red Castle Fm.

- E. boundary: faulted contact with overlying fm. of HadesPass (?)

- E. boundary: faulted contact with overlying fm. of Hades Pass(?)

Lower boundary reference location - Erosive/sharp surface (CTS1) between Red Castle Fm.(below) and Dead Horse Pass Fm. (above).

- Erosive surface (SB e) between Dead Horse Pass Fm. (below)and distinctive red, subfeldspathic fine-grained sandy siltstone(above).

- E. wall, Henry’s Fork drainage above Dollar Lake (UTM:12 T 0553278/4520439 (NAD 27)

- E. wall, Henry’s Fork basin at Dollar Lake (UTM: 12 T0553278/4520439 NAD 27)- E. wall, Kings Peak (UTM: 12 T 0553635/4513968 NAD 27)

Unit description Decameter-thick upward-coarsening fine-grained tosandstone couplets. Fine-grained rocks are laterallycontinuous (10s to 100s of meters), meters- to rarelydecameters-thick, black to green, laminated clay-shale tosiltstone and lesser fine-grained, wavy-laminatedsandstone and a low diversity fossil assemblage ofacritarchs Leiosphaeridia sp. and organic filaments; or redto black to tan, fine-grained, parallel and wavy laminatedor hummocky cross stratified sandstone and siltstone withlesser clay-shale. Sandstone is either (a) purple to tan, wellto subrounded, well sorted, medium- to coarse-grained,quartz to subarkosic with lesser silty sandstone and sandysiltstone and organized in tabular to broadly lenticular orsigmoidal beds; or (b) interbedded, decimeter-thick graylaminated shale and black, pink, or tan fine-grainedsandstone that fines upward into siltstone and rarely iscapped by cm-thick shale. Refer to Appendix A for acomplete stratigraphic column of the Dead Horse Pass Fm.at the reference section (S. flank, Gilbert Peak).

Decameter-thick upward-coarsening couplets similar to theDead Horse Pass Fm. The Mount Agassiz Fm. is distinguishedfrom the Dead Horse Pass Fm. by the thicker and morecommon presence of interbedded, decimeter-thick graylaminated shale and black, pink, or tan fine-grained sandstonethat fines upward into siltstone and rarely is capped bycm-thick shale. The Mount Agassiz is also typically lighterbeige to white in color.


Table 2 (Continued )

Name Dead Horse Pass Formation Mount Agassiz Formation

Refer to Appendix A for a complete stratigraphic column of theMt. Agassiz Fm. at the reference section (s. flank, Gilbert Peak).

Dimensions 340 m to 490 m thick at type area (Wallace, 1972) 310 m to 460 m thick in the type area (Wallace, 1972)153 m thick at unit reference section (Kingsbury, 2008;refer to Appendix A for a complete stratigraphic column atthe reference section, s. flank, Gilbert Peak)

165 m thick at unit reference section (Kingsbury, 2008; refer toAppendix A for a complete stratigraphic column at thereference section, s. flank, Gilbert Peak)

Geologic age Neoproterozoic (∼740 - 770 Ma, Dehler et al., 2010) Neoproterozoic (∼740 - 770 Ma, Dehler et al., 2010)Correlations - Red Castle Fm. (W. Uinta Mountain Group) - Red Castle Fm. (W. Uinta Mountain Group)

- The Dead Horse Pass Fm grades into the Red Castle Fm. atthe head of the Henrys Fork basin, near the boundary

gles.

- The Mount Agassiz Fm. grades into the Red Castle Fm. at thehead of the Henrys Fork basin, near the boundary between the

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ed Castle Formation (tabular quartzose lithofacies, Figs. 5 and 6end g); one from the lower member, Red Castle Formation (lentic-lar arkose lithofacies, Fig. 6f); one from the middle member,ed Castle Formation (tabular arkose lithofacies, Fig. 6d); and one

rom the upper member, Red Castle Formation (siltstone lithofa-ies, Fig. 6b). The five new samples are displayed together in Fig. 6ith two previously reported Sensitive High Resolution Ion Micro-robe (SHRIMP) data sets from the lowermost Dead Horse Passormation (siltstone lithofacies, Fig. 6c) and the formation of Hadesass (lenticular quartzose lithofacies, Fig. 6a) (data in Dehler et al.,010).

.1. Methods

The detrital zircon mineral separates were produced from sev-ral kg of fine- and medium-grained sandstone. A heavy mineraloncentrate was prepared from the total rock using standard crus-ing, washing, heavy liquid (Sp. Gr. 2.96 and 3.3), and paramagneticrocedures (Williams, 1998).

U-Pb geochronology was conducted in 2010 and 2011 by laserblation multicollector inductively coupled plasma mass spectrom-try (LA-MC-ICPMS) (Gehrels et al., 2006, 2008, 2011). One hundredandom zircon grains from each sample were ablated with a New

ave UP193HE Excimer laser using a spot diameter of 30 �m. Alleasurements were made in static mode, using Faraday detectors.

ach analysis consisted of one 15-second integration on peaks withhe laser off (for backgrounds), 15 one-second integrations with theaser firing, and a 30 second delay to purge the previous samplend prepare for the next analysis. The ablation pit was ∼15 �m inepth.

For each analysis, the errors in determining 206Pb/238U and06Pb/204Pb result in a measurement error of ∼1–2% (at 2-igma level) in the 206Pb/238U age. The errors in measurement of06Pb/207Pb and 206Pb/204Pb also result in ∼1–2% (at 2-sigma level)ncertainty in age for grains that are > 1.0 Ga, but are substantially

arger for younger grains due to low intensity of the 207Pb signal.he 206Pb/238Pb age is used for grains (sparse in the present study)ess than 1000 Ma. Common Pb correction was accomplished bysing Hg-corrected Pb and assuming an initial Pb composition fromtacey and Kramers (1975).

Inter-element fractionation of Pb/U is generally ∼5%, whereaspparent fractionation of Pb isotopes is generally < 0.2%. In-runnalysis of fragments of a large zircon crystal (every fifth mea-urement) with known age of 563.5 ± 3.2 Ma (2-sigma error) wassed to correct for this fractionation. The uncertainty resultingrom the calibration correction is generally 1–2% (2-sigma) for both06Pb/207Pb and 206Pb/238U ages.

The data were reduced using the Isoplot Excel Macro of Ludwig2003). The number of grains shown on the plots of Fig. 6 rep-esents only analyses less than 10% discordant and 5% reverseiscordant. The detrital zircon age peaks were picked directly from

Kings Peak and Mount Powell quadrangles.

the probability-density curve, and ages of populations were gener-alized visually. The number of zircons analyzed is shown on eachplot. Most (over 97%) grains are less than 10% discordant.

4.2. Observations and interpretations

We recognize two provenance signatures in the detrital zirconage spectra. One provenance signature is characterized by mixedProterozoic and Archean age components. The other provenancesignature is characterized by a dominant Neoarchean peak. Thesepatterns are consistent with previous UMG provenance studies(Mueller et al., 2007; Dehler et al., 2010).

Four of the new detrital zircon samples and both of the pre-viously reported samples (Dehler et al., 2010) have the mixedprovenance signature. The lowest exposed quartz sandstone of theIsland Lake tongue (2SL10, Fig. 6g) has large zircon age peaks at1035 and 1070 Ma, within a broad distribution from 950 to 1170Ma that makes up 75% of the sample. There is a small peak (10%)at 1620 Ma and scattered older Paleoproterozoic and Neoarcheangrains. The overlying arkosic sandstone (3SL10, Fig. 6f) also hasmixed detrital zircon ages, with peaks at 1075 and 1190 Ma. Grains1025–1200 Ma make up 42% of the sample. Grains between 1400and 1900 Ma make a scattered distribution. The only older peak isat 2630 Ma. The overlying quartzose Island Lake tongue (27PL08,Fig. 6e) has age-peaks at 1090 and 1200 Ma, with 58% of the grainsbetween 1000 and 1200 Ma. There is a prominent grouping (23% ofthe grains) at 1360–1400 Ma and scattered Paleoproterozoic andArchean grains. Sandy siltstone of the upper member, Red Cas-tle Formation (5SL10, Fig. 8b) has a wide grain-age distribution,with peaks at 1090 and 1190 Ma, within a grouping from 1000 to1200 Ma that includes 47% of the grains. There are also age-peaksat 1255 and 1890 Ma, within a distributed set of grains as old at2700 Ma. The stratigraphically highest sample is shown in Fig. 6aand is from the formation of Hades Pass (31PL06, SHRIMP data).This sample has distributed Proterozoic grain ages with 30% of thegrains from 1000 to 1200 Ma and small Archean peaks at 2560 and2625 Ma.

Two of the detrital zircon samples have mainly Archean pro-venance signatures. A fine-grained arkosic sandstone in the middlemember of the Red Castle Formation (22SL10; Fig. 6d) has a uni-modal Archean age peak at 2630 Ma, with 100% of the grainsbetween 2560 and 2720 Ma. The fine-grained, feldspathic arenite ofthe Deadhorse Pass Formation (36PL06, SHRIMP, Fig. 6c) is compa-rable, with scattered Proterozoic grains and a strong Archean peakat 2620 Ma. Archean grains make up 66% of the non-discordantgrains.

In general, the provenance of the observed Proterozoic age-
peaks are interpreted as follows: 1000–1200 Ma populations areGrenvillean, e.g. Mueller et al. (2007); 1340–1430 Ma grains werederived from A-type mid-continent granites (Anderson, 1989);1650–1890 Ma Paleoproterozoic grains were derived from the


Table 3Summary of formations, lithofacies, and facies associations.

Formation LithofaciesAssociation

Lithology/grain size Bedding and structures Interpretation

Lithofacies

Upper mbr., RedCastle Fm.; DeadHorse Pass Fm.;Mount AgassizFm.

Offshore to lower shoreface marine

Mudstone Black to green, fissile,clay-shale to siltstone; rarefine-grained sandstone;low diversity fossilassemblage of acritarchsLeiosphaeridia sp. andorganic filaments

Laterally continuous (10s–100s m); parallel laminated shale;wavy laminated sandstone

offshore, belowand near stormwave base.

Siltstone Black to tan fine-grainedsandstone and interbeddedsiltstone, lesser clay-shale

Laterally continuous (>100s m); parallel and wavy laminations(Fig. 7D), hummocky cross stratification (Fig. 7A)

Lower shorefacenear storm wavebase;offshore-transitionzone

Island Lake tonguesof lower mbr.,Red Castle Fm.;Dead Horse PassFm.; MountAgassiz Fm.

Upper shoreface and nearshore marine

Tabular quartzose Well to sub-rounded, wellsorted, medium tocoarse-grained, quartz tosub-arkosic arenite; lesserfine-grained sandstone andsiltstone; occasional shalecaps

Laterally continuous (>100’s m); tabular to broadly lenticularbeds; occasional decameter-scale foresets (Fig. 7C); currentand wave ripples; mudcracks; planar-tabular and troughcross-beds; soft sediment deformation associated withlenticular beds; occasionally massive. Gross upward-finingtrend (>100 m) from Dead Horse Pass to Mt. Agassiz Fms.:Fine-grained interbeds increase upsection; decimeter-thickfine-grained sandstone with mud-chips, current ripples, andlesser flaser bedding (Fig. 7E) and shale interbeds fine upwardinto siltstone with occasional shale caps. West-directed(Mount Agassiz Fm.) and southeast directed (Island Laketongue) paleocurrents (Fig. 5).

Upper shorefacemarine/nearshoreand possiblyestuarine

Lower (excludingthe Island Lakequartzitetongues), middleand upper mbrs.,Red Castle Fm.

Deltaic

Tabular Arkose Red, angular to subangular,poorly sorted, coarse-grained feldspathic areniteto feldspar-rich pebbleconglomerate withinterbedded siltstone andsilty sandstone.

Laterally continuous (>100s m), tabular, upward-finingsand/siltstone couplets (10-50cm-thick scale), with sharpupper and basal contacts; current ripples truncated at regularintervals by reactivation surfaces and often overlain by muddrapes; whole preservation of cm-scale dunes; climbingripples; mud rip-up clasts; soft sediment deformation;occasional 0.5 to 1cm-scale, euhedral feldspar clastsconcentrated along bed bases; bidirectionalnorth/south-directed paleoflow (Fig. 5); interbedded with thesiltstone lithofacies; decrease in siltstone lithofacies interbedsfrom east to west of study area (fig. 5)

braid bars on abroad, flat,well-developedtidally-influencedbraid-delta

Lenticular arkose similar to tabular arkosewith lesser textural andcompositional maturity;reworked quartz areniteclasts

Amalgamated, sub-meter to meter-thick lenticular beds witherosive, concave bases that pinch into sharp, planar uppersurfaces (channel forms) and are rarely capped by cm-thick,planar laminated, sandy siltstone (Fig. 7J). Lenticular beds fineupward from granual-bearing very coarse-grained sandstoneto medium-grained, cross-bedded sandstone and contain mudrip-up clasts and 0.5 to 1 cm, euhedral feldspar clasts. Thelenticular arkose lithofacies repeatedly overlies the tabularquartzose lithofacies across an erosive lower contact (Fig. 7F).Siltstone clasts from the tabular quartzose lithofacies arereworked into the bases of lenticular arkose beds.

braid bars of atidally influencedbraid-delta

Lowermost fm. ofHades Pass

Fluvial

Lenticularquartzose

Red, sub-angular to wellrounded, poorly to wellsorted, medium- tocoarse-grained quartz tofeldspathic arenite andlesser siltstone

Amalgamated, decimeter-thick lenticular beds with erosive,concave bases that pinch into sharp, planar top surfaces(channel forms) often capped by cm-thick, planar-laminatedsandy siltstone (Fig. 7L); internally massive beds or troughcrossbeded,; abundant cm-scale steeply inclined (∼30◦ - 40◦),wedge-shaped accretion surfaces; current ripples; softsediment deformation; slump folds; abundant secondaryalteration; southeast-directed paleoflow (Fig. 5). Transitionsinto the lenticular arkose lithofacies to the west.

Braided fluvial


Fig. 5. Measured stratigraphic sections including paleocurrents and sequence stratigraphic interpretation for the Red Castle, Dead Horse Pass and Mount Agassiz formations.M s ands eableq pendi

YsweL

t

easured sections are reference sections for the newly formalized Dead Horse Pashown on measured sections. A transgressive surface and sequence boundaries, tracuadrangles. Descriptions of measured sections can be found in Data Repository Ap

avapai-Mazatzal Provinces (Karlstrom and Bowring, 1993. Con-istent with Dehler et al. (2010) and Spencer et al. (2012),e interpret that these Proterozoic components were deliv-

red by transcontinental rivers from southern and/or easternaurentia.

In contrast, we interpret the two mainly Archean age distribu-ions (Fig. 6c and d) to have been derived from a south-flowing

Mount Agassiz formations. Sequence stratigraphic terminology used in the text is on cliff walls over several kilometers, serve as lines of correlation between the twoces 1 & 2.

fluvial system draining the Neoarchean southern WyomingProvince (Wallace, 1972; Mueller et al., 2007). The southernWyoming Province is characterized by detrital zircon age spectra
(age peaks at 2627, 2681, and 2727 Ma, see Fig. 2 of Shufeldt et al.,2010) that very closely match the Neoarchean ages we report (agepeaks at 2560, 2625, 2620, 2630, and a cluster around 2700 Ma).Furthermore, these two samples with the highest percentage of


Fig. 6. Probability-frequency plots for seven detrital zircon samples representing the exposed stratigraphic section in the Uinta Mountain Group from the north-centralU t the bp hroug

Nfe(ttt

inta Mountains. Plots are arranged stratigraphically with the oldest (letter g) arobability-density curve. Plots a and c are from Dehler et al. (2010). Plots b and d t

eoarchean grains are also the most arkosic, as would be expectedrom north-derived fluvial systems draining the proximal south-rn Wyoming craton, where Neoarchean granites are extensive
Mueller and Frost, 2006). Although Neoarchean detrital grains inhe Paleoproterozoic Vishnu Schist of the Grand Canyon are thoughto be sourced from the Mojave Province (Shufeldt et al., 2010),he ages from the Vishnu span Neoarchean to Paleoproterozoic (as
ottom of the diagram. Selected age-peaks are shown and generalized from theh g contain new data presented in this paper (Supplementary data Table S1).

young as 2.2 Ga), and do not form the clean 2.6 and 2.7 Ga peakspresent in the arkosic Uinta Mountain Group.

5. Sequence stratigraphy

We use 1:24,000 field mapping of the Mount Powell andKings Peak 7.5 min quadrangles, lithofacies and facies associations,

7 recam

vnstNswps

oactot

FcrfpsbfiHwiatMaFmaF(atcPHT

4 E.M. Kingsbury-Stewart et al. / P

ertical stacking patterns, stratal geometries, and stratal termi-ations (onlap, downlap, and truncation) to identify a sequencetratigraphic hierarchy comprising eight depositional sequenceshat stack to form one nearly complete composite sequence (sensueal and Abreu, 2009). Lithofacies, vertical stacking patterns, and

tratal geometries are displayed in spectacular, panoramic cirqueall exposures and documented in Figs. 2, 7–10. Vertical forestep-ing and backstepping facies relationships observed in measuredection are exhibited in Fig. 5.

We interpret a sequence stratigraphic framework in termsf a hierarchy of accommodation-succession following Nealnd Abreu (2009). We interpret lithofacies and facies asso-
iations, vertical staking patterns, and stratal geometries anderminations using the accommodation succession terminologyf Neal and Abreu (2009) because this terminology describeshe hierarchy of sedimentary units based entirely on geometry
ig. 7. Photographs of facies associations (2 pages). (A–F) offshore to lower shoreface maross-stratification in fine-grained sandstone, offshore to lower shoreface marine lithofaidge northwest of Dollar Lake, Henry’s Fork Basin. (B) Fine-grained sandstone to siltstoneacies association. Fine-grained sandstone to siltstone interbeds have an erosive upper conresent below such sandstone beds. Hammer for scale; Mount Agassiz Formation northhoreface sandbar (chenier of Wallace, 1972), tabular quartzose lithofacies upper shorefaelow north face of Kings Peak, Kings Peak quadrangle, Mount Agassiz Formation. (D) Latene-grained silty sandstone and interbedded dark mudstone, siltstone lithofacies, offshoorse Pass Formation, north-south-trending ridge northwest of Dollar Lake, Henry’s Foravy-laminated silty sandstone and siltstone, tabular quartzose lithofacies, upper shorefa

s 15 cm high. Outcrop along south wall of Milk Lake ridge, Painters Basin, central Kings

rkose lithofacies, deltaic facies association (below) and tabular quartzose lithofacies, uppongue of lower Red Castle Formation). Note the dramatic contrast between the immatu

ap board, 12 in. high, for scale. Outcrop located along creek just west of the Red Castggradational bedding geometry, tabular arkose lithofacies, deltaic facies association, midork river near Dollar Lake (within Fig. 2 photopanel). (H) Trough-cross bedding within

iddle Red Castle Formation. Note recessive intervals (finer-grained fraction) between talong the north-west wall of Henry’s Fork basin. (I) Mud draped reactivation surface (bormation. Pencil for scale. Outcrop located along the eastern edge of Henry’s Fork basinblack arrows) and internal crossbedding, lenticular arkose lithofacies, deltaic facies assocccretion surfaces in middle of photo. Outcrop located in the western Mount Powell quadrabular arkose lithofacies, deltaic facies association, upper Red Castle Formation. Note muoarse-grained arkose, and mud-draped foresets (dark colored inclined laminae). Hammeeak quadrangle. (L) Channel forms with poorly developed accretion surfaces and thin silades Pass). Field book and hammer for scale. Outcrop located along the east-trending clarail Rider Pass, Kings Peak quadrangle.

brian Research 236 (2013) 65– 84

without any implied relationship between systems tracts andthe shelf edge or sea level. The terms ‘highstand’ and ‘low-stand’ imply a relationship between systems tracts and the sealevel curve, which is unresolved for the Neoproterozoic, whilethe terms ‘APD’ (aggradation–progradation–degradation) and ‘PA’(progradation–aggradation) objectively describe the surfaces andstratal geometries that make up the physical rock record. Further-more, use of accommodation-succession terminology allows us todescribe a hierarchy of higher-frequency depositional sequencesnested within a lower-frequency sequence while avoiding defin-ing stratigraphic cycle order in the absence of high-frequency agecontrol. The hierarchical framework of Neal and Abreu (2009)
is, from small-scale to large-scale: parasequence, systems tracts,depositional sequence, sequence set, composite sequence, com-posite sequence set, and megasequence. We document a sequencestratigraphic hierarchy for the middle UMG consisting of system
rine and shoreface and nearshore marine lithofacies associations: (A) Hummockycies association. Pen for scale; Dead Horse Pass Formation, north-south-trending

interbeds within the tabular quartzose lithofacies, upper shoreface and nearshoretact and are overlain by medium-grained sandstone. Desiccation cracks are locally

of Gunsight Pass. (C) Decameter-scale, southward prograding inclined foresets ofce and nearshore facies association. Circled bush is about 2 m long. Ledge outcroprally continuous tabular to swaley bedding, with occasional hummocks (Fig. 7A) in

re to lower shoreface marine lithofacies association. Hammer for scale; basal Deadk Basin. (E) Current rippled and flaser bedded sandstone overlain by parallel- andce and nearshore marine facies association, Mount Agassiz Formation. Field of viewPeak quadrangle. (F) Sharp contact (sequence boundary b) between the lenticularer shoreface and nearshore marine facies association (above: Island Lake quartzitere, coarse-grained, arkose and the mature, well-sorted red-colored quartz arenite.le. (G–L): deltaic and fluvial facies associations (G) Rhythmically stacked, tabular,dle Red Castle Formation. Cliff-wall outcrop is ∼305 m high. Located east of Henry’scrudely tabular medium beds, tabular arkose lithofacies, deltaic facies association,bular beds. Dog is ∼35 cm tall. Ledge outcrop below the east flank of Mount Powelllack arrow), tabular arkose lithofacies, deltaic facies association, upper Red Castle

north of Gunsight Pass. (J) Lenticular to wedgeform beds with accretion surfacesiation, lower Red Castle Formation. 1.5 m Jacob Staff (circled) for scale. Note lateralangle south of Island Lake. (K) Intimately associated fine- and coarse-grained units,d rip-up clast in upper left corner (with arrow), cm-scale interbedded siltstone andr for scale. Outcrop located above Dollar Lake, east wall of Henry’s Fork Basin, Kingsty interbeds, lenticular quartzose lithofacies, fluvial facies association (formation ofw-like ridge that separates Painter Basin (north) from Atwood Basin (south), along


(conti

tt

5

btCtdts

t

Fig. 7.

racts that stack to form depositional sequences that in turn stacko form a partial composite sequence (Fig. 5).

.1. Lithofacies and facies associations

We broadly identify six lithofacies and four facies associationsased on characteristic lithology/grain size, sedimentary struc-ures, bed geometry, and detrital zircon signatures within the Redastle, Dead Horse Pass, Mount Agassiz and Hades Pass forma-ions. We present photographs of representative lithofacies in Fig. 7,etailed lithofacies observations in Table 3, and interpretations in
he text, below, under the sub-header ‘interpretations’ within aeparate subsection for each facies association.
Lithofacies are resolved on a meter to tens-of-meter scale withhe goal of capturing the lateral and vertical facies changes through

nued ).

hundreds of meters of strata (Fig. 5). Interpreted lithofacies associ-ations include offshore to lower shoreface marine, upper shorefaceand nearshore marine, deltaic, and fluvial. These depositional envi-ronments are generally similar to those proposed by Wallace(1972).

Unlike similar studies in Phanerozoic strata, the depositionalenvironment of Precambrian strata is difficult to determine due toan absence of diagnostic trace and body fossils. The increased ambi-guity of paleoenvironmental interpretation of Proterozoic rockspresents a unique challenge, offset in the UMG by spectacularpreservation of sedimentary structures. We rely on these sed-
imentary structures, facies architecture, the nature of contacts,and lateral-vertical facies changes to interpret depositional envi-ronment. We recognize the particular ambiguity of fine-graineddeposits, which can lack physical sedimentological information.

7 recam

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5(

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FMsH


.1.1. Offshore to lower shoreface marine facies associationmudstone and siltstone lithofacies)

Observations: Refer to Table 3.Interpretation: The mudstone and the siltstone lithofacies

Fig. 7a and d) record the most distal marine environments inhe middle UMG. Decimeter- to meter-thick accumulations ofarallel-laminated black to green clay-shale (mudstone lithofa-ies) record a low-energy environment mainly below storm wavease. Centimeter-thick, fine-grained, wavy-laminated sandstoneeds represent storm-derived fluxes of coarser-grained materialeposited near storm wave base (Fig. 7d). Fine-grained sandstonend siltstone with hummocky cross stratification and plane bedssiltstone lithofacies, Fig. 7a) record deposition above storm wavease in the offshore-transition zone of a wave-affected shorelineDumas et al., 2005; Dumas and Arnott, 2006; Dalrymple and Choi,007). Microfossils in the mudstone lithofacies (unpublished data,ingsbury, 2008) are similar to those found in other fine-grainedMG sediments (Dehler et al., 2005) and are interpreted to indicateeposition below a shallow chemocline in an intracratonic seaway,imilar to the Black Sea today (Nagy and Porter, 2005; Nagy et al.,009).

.1.2. Upper shoreface and nearshore marine facies associationtabular quartzose lithofacies)

Observations: Refer to Table 3.
Interpretation: The tabular quartzose lithofacies is interpreted to
epresent upper shoreface and nearshore marine deposits withineveral upward-coarsening stratigraphic successions that recordffshore-transition through upper shoreface/nearshore marine

ig. 8. Photopanel of the northwest-facing (Fig. 8A) and north-facing (Fig. 8B) ridges of Gount Agassiz Formations. The box indicates the area of the zoomed-in photos. The arr

hown in the lower photos. DS = Depositional sequence. Zuc: Red Castle Formation; Zud:ades Pass.


deposition. Textural and compositional maturity, cross bedding,mudcrack casts and local scouring into mudstone units below(Fig. 7b) indicate the tabular quartzose lithofacies was depositedunder moderate to high energy, under shallow to subaerial con-ditions, and characterized by significant sediment reworking. Thegross upward-fining trend over greater than 100 m from the DeadHorse Pass to Mount Agassiz formations, flaser beds (Fig. 7e) andoccasional mud cracks suggest a transition up section to depositionwithin a shallow, low-energy environment, perhaps a back barrierlagoon or an estuary, near the bedload convergence zone undermixed marine and fluvial processes (Dalrymple and Choi, 2007).

5.1.3. Vertical facies transition between the offshore to lowershoreface marine facies association and the upper shoreface tonearshore marine facies association

The mudstone and siltstone lithofacies (offshore to lowershoreface marine facies association) and tabular quartzose lithofa-cies (upper shoreface to nearshore marine facies association) formdecameter- thick, upward-coarsening cycles with sharp, often ero-sive upper and lower contacts. The lower contact of each cycle isoverlain by the mudstone or the siltstone lithofacies (Fig. 7a and d,Figs. 2 and 5), which grades into the tabular quartzose lithofacies(Table 3, Figs. 2 and 7c and e).

5.1.4. Deltaic facies association (tabular and lenticular arkose
lithofacies)
Observations: Refer to Table 3. The lateral expression of thedeltaic facies association varies from west to east across the studyarea (Fig. 5). The lenticular arkose lithofacies (Fig. 7f,j) is only

ilbert Peak above Gilbert Lake, the reference section for the Dead Horse Pass andow points to the northwest. Close up of strata, with interpreted stratal geometry

Dead Horse Pass Formation; Zuma: Mount Agassiz Formation.; Zuh: formation of


(conti

eFa(e(dsfiq

rflsetaa

Fig. 8.

xposed in the western study area (Mount Powell quadrangle,ig. 1) and may be present in the subsurface of the eastern studyrea (Kings Peak quadrangle, Fig. 1). The tabular arkose lithofaciesFig. 7g–k) is exposed in both quadrangles. To the west (Mount Pow-ll quadrangle) it is coarser-grained with south-directed paleoflowFigs. 5 and 7h) and locally contains decameter-scale, south-ipping low-angle foresets. Paleoflow is to the north in the easterntudy area. Although mudstone lithofacies interbeds are morerequent up section across the study area, mudstone lithofaciesnterbeds are thickest and most abundant to the east (Kings Peakuadrangle, Fig. 7g).

Interpretation: We interpret the deltaic facies association toepresent a tidally influenced braid-delta fed by a south-flowinguvial system that was transverse to the larger, east-west trendinghallow marine depositional environment. Fig. 11 is a schematic
nvironment of deposition map meant to illustrate facies rela-ionships through time for the middle UMG within the studyrea. Textural and compositional immaturity, detrital zirconsnd sedimentary structures (e.g., climbing ripples and dunes,
nued ).

south-directed paleocurrents, and soft-sediment deformation)suggest a proximal, northern source and rapid deposition ofupward-fining bodies of sediment. Tidal influence is locally sug-gested by bi-directional north- and south-trending paleocurrentsand ubiquitous, intimately associated fine- and coarse-grainedmaterial on a millimeter- (mud-draped foresets, Fig. 7i) todecameter-scale (interlayered mudstone, siltstone, and tabulararkose lithofacies, Fig. 7g), which indicate repeated fluctuationbetween suspension-fallout and bedload movement processes.These strata are comparable to other tidally influenced deposits(e.g., Clifton and Phillips, 1980; Fedo and Cooper, 1990; Dalrymple,1992; Brettle et al., 2002), including the correlative Big CottonwoodFormation (Ehlers and Chan, 1999; Dehler et al., 2010).

Channelforms with internal cross-bedding, common mud rip-up clasts, coarse, euhedral feldspar grains, and occasional siltstone
caps characteristic of the lenticular arkose lithofacies suggest depo-sition of braid bars within braided distributary channels on aproximal delta plain Fig. 11a). Common tabular quartzose litho-facies interbeds record interaction between the braid delta and

7 recam

ts

brodLod

tdqabM(mprrda

Fss


he marine body it opened into and indicate fluctuations betweenhoreface to nearshore marine or fluvial processes (Fig. 11b and c).

Cross-stratification and km-scale, laterally consistent tabulared geometry, overall finer grain size and greater textural matu-ity (as compared to the lenticular arkose lithofacies) characteristicf the tabular arkose lithofacies suggest sheets of subaqueousunes traveling across a broad, well-developed delta plain (Fig. 7g,ong, 1982; Miall, 1984, 1992, 1996; Yoshida, 2000). Interbedsf the offshore marine facies association indicate delta fronteposition.

Proximal delta plain deposits dominated by fluvial processesransition to medial/distal delta plain to delta front depositsominated by tidal processes from the west (Mount Powelluadrangle) to east (Kings Peak quadrangle) across the studyrea (Figs. 1, 5 and 11). Coarser-grained sediment, channelformed geometries, and south-directed paleoflow observed in theount Powell quadrangle record a south-flowing fluvial system

Fig. 11a). Finer-grained sediments, increased frequency of offshorearine facies association interbeds, and primarily north-directed

aleoflow to the east (Kings Peak quadrangle, Figs. 1 and 5)
ecord an eastward transition to a delta front to prodelta envi-onment (Fig. 11c). North-directed paleocurrents record sandeposition during dominant flood tides. Similar flood tide depositsre observed in other ancient and modern deposits (e.g. Clifton
ig. 9. Photopanel of the east-facing wall of Kings Peak above Painter Basin. The box indtratal geometry on the north end of this ridge. (B) shows stratal geometry on the middhown in the lower photos. DS = Depositional sequence. Zuma: Mount Agassiz Formation


and Phillips, 1980; Dalrymple et al., 1992; Dalrymple and Choi,2007).

5.1.5. Fluvial facies association (lenticular quartzose lithofacies)Observations: Refer to Table 3.Interpretation: Following Wallace (1972), the lenticular quart-

zose lithofacies (Fig. 7l) records braided fluvial deposition assuggested from stacked, lenticular-shaped, upward-fining beds,sedimentary structures, and paleoflow. Stacked, lenticular bedgeometries with erosive bases (channel forms) and siltstone capsrecord braid bar deposition (Miall, 1984, 1996). The high sand tosiltstone ratio supports braided fluvial deposition, where overbankdeposits are poorly developed and often cannibalized by braidedriver channels. Braided fluvial systems were likely common in theProterozoic due to decreased bank stability and increased sedimen-tation rates caused by an absence of terrestrial plant life (Long,1982). Fluvial braid plains are identified in other ancient marinethrough tidal estuarine to fluvial depositional systems (e.g., Fedoand Cooper, 1990; Yoshida, 2000). The gradation from lenticular
quartzose to lenticular arkose lithofacies from east (Kings Peakquadrangle) to west (Mount Powell quadrangle) demonstratesthe persistence of the Red Castle river system throughout UMGdeposition.
icates the area of the zoomed-in photos. The arrow points towards north. A showsle southern part of the ridge. Close up of strata, with interpreted stratal geometry; Zuh: formation of Hades Pass.


(conti

5

c1mells

fdit

FsidR

Fig. 9.

.2. Vertical stacking patterns

Eight depositional sequences stack to form one nearly completeomposite sequence within the study area. Depositional sequences

through 3 each shallow upward from upper shoreface/nearshorearine deposits (tabular quartzose lithofacies) to tidally influ-

nced, deltaic distributary braid bars (lenticular and tabular arkoseithofacies). Depositional sequences thicken, and the tabular arkoseithofacies is predominant, up-section and especially within depo-itional sequence 3 (Fig. 5).

Depositional sequences 4 through 6 each shallow upward
rom offshore marine through shoreface/nearshore marine and/oreltaic facies associations. The deltaic facies association is predom-
nant to the west while marine facies associations are predominanto the east. In the Mount Powell quadrangle depositional sequences

ig. 10. Photopanel of cirque at head of Smiths Fork west of the Red Castle. The arrow pohows interpreted stratal geometry. Movement symbols next to arrows indicate onlappinnto and out of the page (to the north or south) and some component of movement aloownlapping to the south (into the page) and west (along the strike of the page to the righed Castle Formation.

nued ).

4 through 6 stack with a gross upward-shallowing trend fromoffshore marine (siltstone lithofacies, upper member, Red CastleFormation) through upper shoreface/nearshore marine (tabularquartzose lithofacies, upper member, Red Castle Formation) totidally influenced deltaic distributary channel bars (tabular arkoselithofacies, upper member, Red Castle Formation). To the west,the increase up-section of the tabular arkose lithofacies is inter-preted to record progradation of a mature, broad, relativelyflat braid plain (Fig. 5). In the Kings Peak quadrangle deposi-tional sequences 4 through 8 each shallow upward from offshoremarine (siltstone and mudstone lithofacies, lowermost Dead Horse
Pass Formation) to upper shoreface/nearshore marine (tabularquartzose lithofacies, Dead Horse Pass and Mount Agassiz for-mations). Depositional sequences 6 through 8 are aggradationallyand possibly progradationally stacked and contain offshore and
ints towards west. Upper photo shows strata without interpretation, lower photog and downlapping at an angle to the cliff face, with some component of movementng the strike of the page (to the east or west). A circled x indicates the strata ist). DS = Depositional sequence; Zucm = middle Red Castle Formation; Zucu = upper


Fig. 11. Schematic reconstruction of depositional environments for the middle Uinta Mountain Group exposed in the study area (Red Castle to Mount Agassiz formationsand the formation of Hades Pass). An east-west-trending shoreline is fed by a south-flowing braided fluvial system and a west-flowing braided fluvial system. The locationand significance of the depositional environments depicted in this figure fluctuated throughout the evolution of the UMG basin, as reflected in the sequence stratigraphicinterpretation presented herein. For example, at the time of deposition of the formation of Hades Pass, the west-flowing fluvial system prograded out across the entire studyarea above composite sequence boundary 2 (see Fig. 5) Lettered rectangles represent the approximate locations of the Mount Powell and Kings Peak quadrangles within thisd A) lowi nd De(

ued

5

stuto

MFMnoacae(

ntboaslstbsmac

tional sequence 4. A maximum flooding surface is likely presentwithin the fine-grained strata that make up the middle part of thesequence. An aggradational–progradational systems tract, (APST;

epositional environment as it evolved through time, during the deposition of the (n the subsurface of the Kings Peak quadrangle); (B) middle Red Castle Formation aD) formation of Hades Pass.

pper shoreface to nearshore marine including fine-grained, lownergy, shallow water, perhaps back-barrier estuarine or lagooneposits.

.3. Stratal geometries, terminations, and surfaces

Significant surfaces are identified by an abrupt facies change,tratal geometries, and stratal terminations (onlap, downlap, andruncation). Sequence boundaries truncate underlying strata withp to several meters of erosional relief, frequently pass laterally intoheir correlative conformities (Catuneanu, 2006) and are frequentlyverlain by onlapping offshore marine facies (Fig. 2).

A composite sequence boundary (CSB 3, contact between theount Agassiz or upper Red Castle and the Hades Pass formations,

ig. 5) can be mapped for tens of kilometers in the central Uintaountains. It is exposed on the east wall of Kings Peak (Fig. 9) and

orthwest of the Red Castle (Fig. 10) where a basinward shift fromffshore and shoreface marine to braided fluvial facies is observedcross the sequence boundary. Composite sequence boundary 3uts out the upper half of depositional sequence 8 at Gilbert Peaknd Milk Lake (Fig. 5e and f). It cuts down section from east to west,liminating depositional sequences 7 and 8 near the Red CastleFig. 5b and c).

We highlight depositional sequence 4 (Fig. 12), exposed on theorthwest flank of Gilbert Peak, to explain how we identify deposi-ional sequences across the study area. Depositional sequence 4 isounded below by an erosive surface that truncates several metersf underlying tabular arkose lithofacies (deltaic facies association)nd is overlain by onlapping strata of the offshore through upperhoreface and nearshore marine lithofacies association (Fig. 2,ower left, Fig. 5e, Fig. 12). Swaley-bedded fine-grained sandstone,iltstone, and interbedded shale are present immediately abovehe basal erosive surface. Interbedded, swaley, hummocky cross-edded, and plane-bedded, fine-grained sandstone, siltstone, and
hale are present above the same stratigraphic horizon several kilo-eters to the west, at Dollar Lake (Fig. 7a and d, Fig. 5d). Quartz
renite of the upper shoreface and nearshore marine facies asso-iation fines upward into several meters of shale and siltstone of

er Red Castle Formation (exposed in the Mount Powell quadrangle, may be presentad Horse Pass Formation; (C) upper Red Castle and Mount Agassiz Formation and

the offshore to lower shoreface facies association (Fig. 5e, Fig. 12).These fine-grained strata in turn coarsen upwards into offlappingquartz arenite of the upper shoreface and nearshore facies asso-ciation. The uppermost quartz arenite strata are truncated by anupper, erosive boundary of depositional sequence 4.

We interpret the lower, erosive boundary of depositionalsequence 4 as a composite transgressive surface (CTS1). Detrital zir-cons in the siltstone lithofacies (offshore to lower shoreface marinefacies association) (Fig. 6c) at the base of depositional sequence4, immediately above CTS1, contain a dominant Archean detritalzircon age peak. The Archean age peak indicates reworking of theunderlying tabular arkose lithofacies and suggests significant scourassociated with marine transgression occurred across CTS 1.

As can be seen in Fig. 12, a retrogradational systems tract(RST, sensu Neal and Abreu, 2009; traditional terminology: trans-gressive systems tract, sensu Mitchum and Van Wagoner, 1991),composed of onlapping offshore through nearshore and shorefacemarine lithofacies, overlies CTS1 and forms the base of deposi-

Fig. 12. Close up view of depositional sequence 4, northwest face of Gilbert Peak,Kings Peak quadrangle. Vertical exaggeration is 30 to 1. The view shown in this figureis enlarged from Fig. 8A.

E.M. Kingsbury-Stewart et al. / Precam

Fig. 13. 770–740 Ma Rodinian paleotectonic reconstruction (after Goodge et al.,2008 and Foster et al., 2006) showing Uinta Mountain Group half-graben extend-ing west to include Big Cottonwood and Little Willow formations. The ChuarGroup and upper Pahrump Group were deposited in the same intracratonic sea-wTT

tdmamtb

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ay. The south-flowing Red Castle River drains Neoarchean Wyoming Province.he west-flowing Laurentian big river drains Proterozoic Yavapai, Mazatzal, andrans-Hudson provinces as well as Grenville orogenic belt.

raditional terminology: highstand systems tract) composed ofownlapping quartz arenite of the upper shoreface and nearshorearine facies association, overlies the maximum flooding surface,

nd forms the upper part of depositional sequence 4. The upper-ost strata of the aggradational–progradational systems tract are

runcated by an erosive surface that forms the upper sequenceoundary of depositional sequence 4.

.4. Sequence stratigraphic interpretation

Depositional sequences stack to form a progradational–ggradational sequence set (PASS, sensu Neal and Abreu, 2009)nd an aggradational–progradational sequence set (APSS). In tradi-ional sequence stratigraphic terminology these would be labeledlowstand” and “highstand” sequence sets (Mitchum and Van

agoner, 1991). Each depositional sequence is comprised of basal, relatively thin, retrogradational systems tract (RST, ortransgressive systems tract”), represented by onlapping fine-rained strata, and an upper, relatively thicker, aggradational–rogradational systems tract (APST), represented by aggradationalo downlapping sandy strata. A composite transgressive surfaceCTS 1, Fig. 5) separates the lower PASS from the upper APSSFigs. 2, 8 and 10). Sequence sets stack to form one nearly com-lete composite sequence (CS2, Figs. 3 and 5) bounded above by aappable composite sequence boundary (CSB3 on Fig. 5).

. Discussion

The Uinta Mountain Group can now be better understood in itsegional paleogeographic context of a mid-Neoproterozoic epicon-inental sea that covered western Laurentia at least 150 millionears before the inception of the Cordilleran passive margin at00–550 Ma (Fig. 13) (Wallace, 1972; Dehler et al., 2010; Linknd Christie-Blick, 2011). The recognition (Dehler et al., 2010; thistudy) of marine (specifically tidal) lithofacies and shallow-marineequence stratigraphic stacking patterns invalidates the interpre-ation of the UMG as a lacustrine system analogous to the cyclic and
ersistently aggradational Belt Supergroup of southwest Montanae.g. Link, 1993; Winston and Link, 1993).
The identification of tidal marine and fluvial-deltaic depo-itional sequences based on physical surfaces, lithofacies, and

brian Research 236 (2013) 65– 84 81

detrital zircon provenance, frames the middle UMG within a pre-dictive stratigraphic hierarchy (sensu Neal and Abreu, 2009). Ourdocumentation of tidal marine and fluvial-deltaic depositionalenvironments is consistent with tidal interpretations for the correl-ative Big Cottonwood Formation of the Wasatch Range (Chan et al.,1994; Ehlers et al., 1997; Ehlers and Chan, 1999) and demonstratesthat this mid-Neoproterozoic (∼770–740 Ma) epicontinental sea-way was connected to the world ocean (Panthalassa). Broadlycoeval marine strata to the south include the Chuar Group of theGrand Canyon and the middle Pahrump Supergroup of the DeathValley area (Fig. 13, Mahon et al., 2012). The existence of a signif-icant Rodinian epicontinental seaway implies the future westernmargin of Laurentia was affected by faulting and long-term (>30 Maduration) subsidence even before it became a west-facing passivemargin.

Sequence Stratigraphy of the Uinta Mountain Group recordsthe interface between this epicontinental sea, local south-draining, coarse-grained fluvial systems, and a major west-drainingtranscontinental river system and reveals potential controlson stratal packages. The eight higher-frequency depositionalsequences may be driven by shorter-term autocyclic and allo-cyclic events, including delta lobe switching, avulsions, climaticfluctuations and local tectonism, whereas the composite sequencerecords the longer-term transgression of the epicontinental sea.Theabsence of well-developed lowstand systems tracts within thestudy area may be explained by a combination of the overall,longer-scale retrogradational trend of the system and the hypoth-esized large lateral extent (tens to hundreds of kilometers) oflithofacies across the broad, low-gradient basin floor of the epi-continental sea. Lowstand systems tracts may have developed inmore distal locations beyond the study area.

Longer-term Neoproterozoic eustatic sea level rise was likelydriven by breakup of the supercontinent Rodinia (Li et al., 2003,2008; Zhu et al., 2011). Plate reorganization is recognized as a driverfor sea level change: Generation of new, hotter and more buoyant,sea floor material decreases ocean basin volume, causing marinetransgression (Heller et al., 1996). Shorter-term drivers on Neopro-terozoic cyclcity are poorly constrained, although glacioeustacy hasbeen suggested as a control on coeval deposits (Dehler et al., 2001a;Mahon et al., 2012).

Given available geochronology, the most likely candidate todrive long-term eustatic transgression at 770–740 Ma was eastAsian rifting. Basalt and dacite-rhyolite of the Beiyixi volcanicswithin the Tarim block (northwest China) are interpreted as recor-ding continental rift-related magmatism and are dated by U–Pbusing SHRIMP at 755 ± 15 Ma (Xu et al., 2005). Granitoids and maficto ultramafic rocks of the Chengjiang magmatics within the YangtzeCraton (South China) are interpreted as syn-rift magmatics and aredated by U-Pb using SHRIMP with ages ranging from 775 ± 8 to751 ± 10 Ma (Li et al., 2003, see also Lin et al., 2007; Li et al., 2008).This rift episode corresponds with the second of three magmaticpulses recognized in the Tarim block between ca. 790 and 740 Maby Zhu et al. (2011). The youngest magmatic pulse within Tarim was650–615 Ma and suggests that rifting of Rodinia was a long-lastingprocess. A multi-stage rift argument is supported by 705–667 Mavolcanic ages from Idaho and Utah (Keeley et al., 2013; Balgordet al., 2013).

We do not favor the paleocontinental reconstruction of Li et al.(2008), which places South China adjacent to southern Lauren-tia, but we recognize the importance of supercontinental breakupas a driver for transgression of the Chuar-Uinta Mountain Group-Pahrump Group seaway. The generation of new oceanic lithosphere
during supercontinental rifting is recognized as a major forc-ing mechanism for long-term (several millions of years) eustaticsea level change (e.g. Cogne and Humler, 2008; Heller et al.,1996).

8 recam

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We favor the reconstruction of Goodge et al. (2008), whichlaces Antarctica and Australia as the western continents that even-ually rifted from Laurentia (Fig. 13). This reconstruction correlatesistinctive 1400 Ma granites in East Antarctica to similar plutons ofhe mid-continent A-type granites of southern Laurentia. Furthert allows for 1490–1610 Ma detrital zircon grains sourced in theawler Volcanics of South Australia to be deposited in the 1450 Ma

ower Belt Supergroup of Idaho and Montana (Ross and Villeneuve,003; Link et al., 2007). Paleomagnetic studies from the UMG, Chuarroup, and the 720 Ma Franklin Dike Swarm of northern Lauren-

ia indicate an equatorial paleolatitude for the UMG epicontinentalea within this larger paleogeographic setting (Fig. 13) (Weil et al.,004, 2006; Evans and Raub, 2011). The Neoproterozoic westernaurentian epicontinental seaway can be used as a tie-point withther continents to further constrain the original continental con-guration of Rodinia.

In addition to east Asian rifting, rifting in northern Laurentiapresent coordinates) likely also contributed to eustatic sea levelise. Onset of rifting that produced northern Laurentian oceanicrust may have propagated southward, starting in the Canadianordillera at 750 Ma (“zipper-rift”, Eyles and Januszczak, 2004). Thisift phase is closest in space, and overlapping in time, with half-raben subsidence of the UMG basin. Crustal thinning expressed as50 Ma continental rifting in the western Canadian Cordillera mayave been a distal cause for the regional faulting and subsidence ofhe UMG basin. Neoproterozoic anorogenic magmatism is recordedn the mafic Gunbarrel dike swarm event in western Laurentia, asar south as the Teton Range in northwest Wyoming (780.3 ± 1.4–Pb baddeleyite analyses, Harlan et al., 2003). Although the north-rn American Cordillera appears to have rifted at 750 Ma (Colpront al., 2002), there is no evidence of rift-related magmatism southf the Gunbarrel dikes until after 720 Ma (Harlan et al., 2003; Lund,008; Balgord et al., 2013). In the Pocatello Formation of southeast

daho, the age of rift-related mafic and trachytic volcanism is ca.17–685 Ma (Keeley et al., 2013).

Likely controls on the eight higher-frequency depositionalequences are autocyclic (delta avulsion, tidal channel migration)nd allocyclic (episodic tectonism, climate fluctuations). Similar m-cale and 100-m scale shallowing-upward cycles are present withinhe coeval Chuar Group (Grand Canyon; where Dehler et al., 2001anferred a glacioeustatic control), and in the middle Pahrump GroupDeath Valley) (Mahon et al., 2012). A regional understanding of theateral nature (directional thinning; lateral extent) of sequencesnd sequence sets and better time constraints are required tonderstand the relative importance of autocyclic and allocyclicontrols on UMG deposition. Future work on UMG epicontinentaleposits may further constrain Neoproterozoic climate fluctuationsrior to the onset of the first phase (716.5 Ma) of low-latitude Stur-ian glaciations (Macdonald et al., 2010; Keeley et al., 2013).

. Conclusions

Facies and stratal architecture of middle Uinta Mountainroup strata in the central Uinta Mountains indicate offshore andhoreface (lower and upper) and nearshore marine, deltaic, anduvial facies associations organized into depositional sequences.ight depositional sequences are stacked within a lower-frequency,omposite sequence that is composed of a progradational to aggra-ational (PASS; traditional terminology: “lowstand”) sequence setverlain by an aggradational–progradational (APSS; traditional ter-inology: “highstand”) sequence set. This composite sequence is

he middle of three composite depositional sequences in the UMGhat together reflect long-term eustatic sea level rise driven byreakup of the supercontinent Rodinia. Rifting of the Tarim andouth China blocks from Asian parts of Rodinia starting around


780 Ma, and ‘zipper rifting’ of Laurentia starting at ca. 750 Ma,most likely drove long-term eustatic transgression at 770–740 Ma.Drivers for nested depositional sequences 1 through 8 reflect acombination of higher frequency autocyclic and allocyclic con-trols. Further investigation of the lateral correlation of sequencesand sequence sets, and improved time constraints, will clarify theimportance of autocyclic (delta lobe switching, channel avulsion)and allocyclic (regional tectonism, climatic fluctuations) controlson UMG deposition. A refined understanding of controls on UMGhigher-frequency depositional sequences is significant towardsunraveling Neoproterozoic climate fluctuations prior to the onsetof the first phase of low-latitude Sturtian glaciations.

Two detrital-zircon signatures are recognized in the UMG. Onesignature has a well-defined Neoarchean peak, and one signaturehas mixed Proterozoic and Archean age components. Lithofacieswith a Neoarchan detrital zircon signature were transported by alocal south-flowing river system draining the southern Wyomingprovince, or reflect significant transgressive marine ravinementacross a composite transgressive surface (CTS 1) that eroded andreworked deposits from this transverse river system. Lithofa-cies with a mixed detrital zircon signature were transported anddeposited by a major, west-flowing river system with a drainagebasin that included much of Laurentia, or were deposited underdominantly marine processes that mixed and reworked these sed-iments.

Documentation of tidal marine and fluvial-deltaic depositionalsequences within the UMG is consistent with previous tidalinterpretations for the correlative Big Cottonwood Formation ofthe Wasatch Range and requires that this mid-Neoproterozoic(∼770–740 Ma) intracontinental seaway was connected to theworld ocean. Thus, we conclude that continental breakup ofsouthwestern Laurentia was episodic and fitful, starting with for-mation of the Uinta Mountain Group-Big Cottonwood Formationhalf-graben at ∼750 Ma. Mafic volcanism and glacial marine sed-imentation of the Pocatello and Perry Canyon formations lastedfrom 717 to 685 Ma (Fanning and Link, 2004; Keeley et al.,2013). Development of the carbonate passive margin did not occuruntil after 550 Ma (Link and Christie-Blick, 2011; Balgord et al.,2013).

Acknowledgements

This work summarizes the M.S. theses of Kingsbury (2008)and Osterhout (2011). Support for this research was provided bythe U.S. Geological Survey, National Cooperative Geologic Map-ping Program Awards No. 07HQAG0145 and 10HQPA0004, toPaul K. Link; National Science Foundation grant EAR-0819759 toLink and Dehler; the Utah Geological Survey Mapping Division;and the Idaho State University Graduate Student Research andScholarship Committee (FY07-R8). This manuscript benefited fromreview by Jeff Geslin at ExxonMobil Upstream Research Company,Doug Sprinkel at the Utah Geological Survey, and an anony-mous reviewer. The Ashley National Forest and Luke Osterhoutprovided field assistance. Diana Boyack helped greatly with the fig-ures. We also acknowledge the hospitality of George Gehrels andUniversity of Arizona Laserchron Lab for detrital zircon analysesand Mark Schmitz at Boise State University for help with zirconseparations.

Appendix A. Supplementary data

Supplementary material related to this article can be found,in the online version, at http://dx.doi.org/10.1016/j.precamres.2013.06.015.

http://dx.doi.org/10.1016/j.precamres.2013.06.015

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Documents

Sequence stratigraphy and formalization of the Middle