PALAIOS, 2011, v. 26, p. 779–789

Research Article

DOI: 10.2110/palo.2011.p11-006r

DETRITAL RECORD OF UPPER TRIASSIC REEFS IN THE OLDS FERRY TERRANE, BLUEMOUNTAINS PROVINCE, NORTHEASTERN OREGON, UNITED STATES

TODD A. LAMASKIN,1* GEORGE D. STANLEY, JR.,2 ANDREW H. CARUTHERS,3 and MEGAN R. ROSENBLATT 2

1Department of Geography and Geology, University of North Carolina at Wilmington, 601 South College Road, Wilmington, North Carolina 28403-5944, USA,

lamaskint@uncw.edu; 2Department of Geosciences, University of Montana, 32 Campus Drive #1296, Missoula, Montana 59812-1296, USA, george.stanley@umontana.

edu, megan.rosenblatt@umontana.edu; 3Department of Earth and Ocean Science, University of British Columbia, 6339 Stores Road, Vancouver, B.C., Canada, V6T 1Z4,

acaruthe@eos.ubc.ca

ABSTRACT

We report a coral-sponge dominated reef lithofacies in detrital boulders ofcarbonate-clast conglomerate from the Olds Ferry terrane, BlueMountains Province, Willow Spring locality, northeastern Oregon. Thisdiscovery constitutes the first report of Triassic reefal lithofacies from theOlds Ferry terrane. Corals at the site include a high-growing, dendroid-phaceloid species that acted as a framework or sediment baffle, and a low-growing, cerioid, encrusting coral and a sponge that acted as sedimentbinders. The co-occurrence of coral taxa in the Wallowa intraoceanic arcand Olds Ferry pericratonic arc terranes suggests that during the LateTriassic, these regions were in proximity to one another. With this report,Upper Triassic carbonate rocks are known from all of the major terranesof the Blue Mountains Province and a Tethyan affinity is established forthe fauna of the Olds Ferry terrane. We suggest that the source of thisLate Triassic coral-sponge reef fauna in the upper member of theHuntington Formation was intrabasinal and that the source rocks are nolonger exposed in the region. Numerous possible regional source areas forthese detrital limestone clasts rule out the need to call upon an exoticterrane source area.

INTRODUCTION

The Late Triassic is generally considered to be a time of extensivecarbonate deposition worldwide, especially in the former Tethys regionof central Europe where extensive reef complexes are well known. TheNorian Stage, in particular, records one of the greatest reef bloomssince the Permian (Flugel, 2002). Many of these early Mesozoic reefcomplexes are thousands of meters thick and contain evidence ofextensive and vigorous reef building; the organisms that constitute theframework range from the northern Calcareous Alps to the southeast-ern Pamirs. As summarized by Flugel (2002), the reef constituents arechiefly calcified algae, foraminifers, microproblematica, calcifiedsponges, scleractinian corals, hydrozoans, and mollusks. Upper Triassiccoral and sponge-rich faunas also appear to have formed aroundvolcanic seamounts(?) and arcs in the ancient Panthalassic Ocean.Many of these faunas yield a predominance of Tethyan-type organismsand are now incorporated into the terrane collage of western NorthAmerica (Blodgett and Stanley, 2008).

Tethyan reef-type faunas are present in North America from centralAlaska to Sonora, Mexico as coral and sponge-rich complexes. LateCarnian–Rhaetian examples from North America, however, are bestgenerally described as beds, lenses, or biostromes, as only a few sitesproduce true reef lithofacies or structures comparable to those presentin the Eurasian Tethys (Stanley and Senowbari-Daryan, 1986; Stanley,1988; Flugel, 2002; Stanley, 2003, 2006). Late Triassic reefs most akinto those of the Tethys are present in the Stikine terrane of the CanadianYukon (Reid and Templeman-Kluit, 1987; Yarnell et al., 1999), the

Quesnel terrane of central British Columbia, Canada (Stanley andNelson, 1996), and the Wallowa terrane of northeastern Oregon,United States (Stanley and Senowbari-Daryan, 1986; Stanley et al.,2008). Many of the reef builders of these Upper Triassic depositsrepresent the same species as those in the Eurasian Tethys. Thedispersal and paleogeography of the fossil biota have been the subjectof considerable discussion in the literature (e.g., Newton, 1988; Smithand Westermann, 1990).

Here, we report the first discovery of a coral-sponge dominated reeflithofacies in detrital boulders of a carbonate-clast conglomerate fromthe Olds Ferry terrane, Blue Mountains Province, northeastern Oregon.With this finding, Upper Triassic carbonate rocks are now known fromall of the major terranes of the Blue Mountains Province and a Tethyanaffinity is established for the fauna of the Olds Ferry terrane.

GEOLOGIC SETTING

The Blue Mountains Province is an amalgamated assemblage ofaccreted Paleozoic–Mesozoic volcanic arcs, sedimentary basins, sub-duction melange complexes, and post-tectonic stitching plutons (Fig. 1;Brooks and Vallier, 1978; Silberling et al., 1984; Vallier, 1995). Fourmajor terranes have been recognized in this region: the Wallowa, Baker,Olds Ferry, and Izee (Vallier, 1995; Fig. 1). These four terranesrepresent two late Paleozoic–early Mesozoic volcanic island-arcassemblages (Wallowa intraoceanic and Olds Ferry pericratonic arcterranes; Vallier, 1995; LaMaskin et al., 2008), a Paleozoic–earlyMesozoic subduction-accretionary complex (Baker terrane; Jones et al.,1976; Brooks and Vallier, 1978; Dickinson and Thayer, 1978; Coward,1983; Schwartz et al., 2010), and a Triassic–Jurassic clastic sedimentarysuccession (Izee terrane; Silberling et al., 1984). Mudrock geochemistryand detrital zircon U-Pb geochronology suggest that the Wallowaterrane was an intraoceanic island arc, whereas the Olds Ferry terranewas an island arc fringing the North American craton (LaMaskin et al.,2008, 2009, 2011). Note that the Baker, Olds Ferry, and Izee terranesare not all fault bounded with respect to one another and do notnecessarily have origins wholly distinct from one another. Thus, tovarying degrees, the Baker, Olds Ferry, and Izee terranes of the BlueMountains are genetically related and represent portions of a westernNorth American arc-trench complex (Dorsey and LaMaskin, 2007,2008; Dickinson, 2008; LaMaskin et al., 2008, 2011; Schwartz et al.,2010).

The spatial relationship between the Olds Ferry and the Wallowaterranes as well as the timing of their amalgamation remains unclear.The Wallowa, Baker, and Olds Ferry terranes were either amalgamatedoffshore during the Late Triassic–Early Jurassic before being accretedto the margin of North America during the Jurassic–Cretaceous(Dorsey and LaMaskin, 2007; LaMaskin et al., 2011), or amalgamationoccurred during the Late Jurassic prior to Cretaceous accretion to thecontinent (Dickinson, 1979; Ave Lallemant, 1995; Schwartz et al.,2011). Rocks of the Blue Mountains Province are overthrust in the* Corresponding author.

Copyright G 2011, SEPM (Society for Sedimentary Geology) 0883-1351/11/0026-0779/$3.00

northeast by high-grade metamorphic rocks of the Salmon River Belt(Lund and Snee, 1988; Manduca et al., 1992, 1993; Selverstone et al.,1992; Lund, 2004; Gray and Oldow, 2005; Lund et al., 2008). TheSalmon River Belt is bounded on the east by the western Idaho shearzone (Fig. 1), a complex structural boundary with the Laurentiancontinental margin (McLelland et al., 2000; Giorgis et al., 2005, 2008).

The Wallowa terrane contains a thick sequence of clastic andvolcanic rocks representing Permian–Jurassic island-arc volcanism(Vallier, 1977, 1995; Tumpane and Schmitz, 2009). In the southernWallowa Mountains, the Upper Triassic (Carnian–Norian) MartinBridge Formation includes Tethyan-type reefs in the Summit Pointmember (Summit Point reefs; Stanley and Senowbari-Daryan, 1986;Stanley et al., 2008). The Martin Bridge Formation grades bothlaterally and upward into deep-marine clastic rocks of the UpperTriassic–Lower Jurassic (Norian–Pliensbachian) Hurwal Formation.

In the eastern portions of the Baker accretionary-subductioncomplex, extensive outcrops of strongly recrystallized carbonate arepresent (Prostka, 1967; Brooks et al., 1976). This unit, the NelsonMarble, is found in association with quartz phyllite, metasandstone,and metaconglomerate, and contains Middle–Late Triassic conodontfaunas (Morris and Wardlaw, 1986; Ashley, 1995). Recent investiga-tions suggest that the Nelson Marble may be an olistostromal body (A.Snoke, personal communication, 2010).

The Olds Ferry terrane represents a Middle Triassic–Lower Jurassicpericratonic volcanic arc succession that is distinct from the Wallowaintraoceanic arc terrane (LaMaskin et al., 2008; Tumpane et al., 2008).Rocks of the Olds Ferry terrane (Fig. 2) include hypabyssal andextrusive volcanic rocks and interbedded volcaniclastic rocks of theHuntington Formation, which contains the Late Triassic detrital coral-sponge reef fauna presented in this paper (Brooks, 1979). The informallower member of the Huntington Formation includes volcanic flowscomposed of monolithologic mafic volcanic breccia, pillowed green-stone, andesite porphyry, and minor rhyolite and rhyodacite (Brooksand Vallier, 1978; Brooks, 1979; Charvet et al., 1990; Tumpane, 2010).A thin-bedded, deep-water limestone unit has previously been describedfrom the lower Huntington Formation; however, no in situ reefs or reef-

FIGURE 1—Regional geologic map of Blue Mountains Province (northwestern

United States) showing distribution of terranes. OR 5 Oregon; ID 5 Idaho; WA 5

Washington state. Modified from Dickinson (1979), Mann and Vallier (1989), and

Gray and Oldow (2005).

FIGURE 2—Mesozoic chronostratigraphy of the Huntington, Oregon region. Modified from LaMaskin (2008).

780 LAMASKIN ET AL. PALAIOS

like facies have been reported (Brooks, 1979; LaMaskin, 2008).Ammonite and bivalve age assignments indicate that this unit spansthe upper Carnian–lower Norian (Brooks, 1979; LaMaskin, 2008).High precision U-Pb ages on zircons from volcanic rocks of the lowermember of the Huntington Formation are Late Triassic, ca. 221–220 Ma (late Carnian; Ogg et al., 2008; Walker and Geissman, 2009;Tumpane, 2010).

The informal upper member of the Huntington Formation includeslaminated shale and thin- to medium-bedded sandstone turbiditesinterlayered with thick-bedded, cobble-to-boulder conglomerate andabundant thick-bedded rhyolite, and rhyodacite porphyry. Highprecision U-Pb zircon ages from rhyolite in the upper portion indicatean Early Jurassic crystallization-depositional age of ca. 188–187 Ma(early Pliensbachian; Ogg et al., 2008; Walker and Geissman, 2009;Tumpane, 2010).

DESCRIPTION

Locality Information

We have recovered a Late Triassic coral-sponge reef fauna from athick-bedded cobble-to-boulder conglomerate in the informal uppermember of the Huntington Formation (Olds Ferry terrane) at a localityherein named Willow Spring (Figs. 3–4, 5A; 44u249530N, 117u149400W).The site is ,15 kms north of the town of Huntington, Oregon on theSnake River. The conglomerate exposures discussed here are within theupper Huntington Formation, stratigraphically below the dated

Pliensbachian tuff units of Tumpane (2010), and are thus LowerJurassic. The fauna is preserved in reworked (i.e., detrital) limestoneclasts that are present within a steep, east-dipping, ,100-m-thicksuccession of conglomerate and sandstone, interbedded with rhyoliteand rhyodacite volcanic-flow deposits. Clasts range from pebble sizedto .1.5 m and are composed of rhyolite, rhyodacite porphyry, basalt,andesite, and limestone. Trace numbers of mudstone-argillite clasts arealso present; additional clast types have not been identified. Lithicframework grains in sandstone that is interbedded with the WillowSpring conglomerate are restricted to a range of volcaniclastic mafic-to-silicic compositions and textures. Specimens are reposited at theUniversity of Montana Paleontology Center, Missoula, Montana;Locality ID# MI 8839.

Carbonate Lithofacies Types

Detrital carbonate clasts found at Willow Spring vary fromfossiliferous limestone to mixed fossiliferous limestone-volcaniclasticlithologies (Fig. 5B). Three distinct lithofacies types are recognized inthe clasts comprising Upper Triassic reef facies (Table 1). On the basisof grain type, texture, and fossil content, they are classified according toDunham (1962, 1970) and supplemented by Embry and Klovan (1971)as: (1) coral boundstone-framestone lithofacies, (2) crinoid packstone-grainstone lithofacies, and (3) spongiomorph-algal grainstone lithofa-cies.

Coral Boundstone-Framestone Lithofacies.—This lithofacies, consist-ing of fine- to coarse-grained, light-gray to pink detrital limestoneclasts, is the dominant carbonate clast lithology at the site (Figs. 5C–E;6F). The fauna, recognized in thin sections and polished samples fromthese clasts (Table 2), includes a high-growing, dendroid-phaceloid

FIGURE 3—Geologic map of the Huntington, Oregon area. Modified from Juras

(1973) and Brooks (1979).

FIGURE 4—Detailed geologic map of conglomerate outcrop area. Additional

unpublished mapping by R. Dorsey, T. LaMaskin, and P. Wright (ca. 2007). Jw 5

Jurassic Weatherby Formation; Trhl 5 Triassic Huntington Formation, informal

lower member; Trhu 5 Triassic Huntington Formation, informal upper member; Qls

5 Quaternary landslide deposits.

PALAIOS DETRITAL RECORD OF UPPER TRIASSIC REEF FACIES 781

(branching) coral, Paracuifia sp., which acted as a framework orsediment baffle, and to a lesser extent, Kuhnastraea cowichanensis

(Clapp and Shimer), a low-growing, cerioid, encrusting coral (Fig. 7A–E). These typical colonial reef corals are found in association with thebranching reef sponge taxon, Spongiomorpha ramosa (Frech) (Fig. 7F).Together, these organisms produced at least a 10–50-cm-high bios-

tromal framework (height estimates limited by clast size). Thecarbonate sand matrix is dominated by skeletal allochems consistingof echinoderm (crinoid and echinoid) and mollusk (bivalves andgastropods) fragments with lesser intraclastic peloidal material. Thiswell-rounded skeletal-peloidal debris suggests abundant abrasion andreworking of detrital carbonate material.

FIGURE 5—Representative outcrop and exposure images. A) Exposures of limestone-clast conglomerates on ridge above Snake River near Huntington, Oregon. Dashed lines

indicate approximate bedding. Jw 5 Jurassic Weatherby Formation; Trh 5 Triassic Huntington Formation. B) Typical exposure of detrital reef facies showing two large

limestone boulders encased in volcaniclastic matrix. C) Dark, detrital silt-filled voids and associated coral bafflestone textures. D) Coarse cement-filled voids. E) Coralline

boundstone composed almost exclusively of low-relief, encrusting corals; hammer head ,15 cm long. F) Crinoid packstone grainstone.

782 LAMASKIN ET AL. PALAIOS

Characteristic reef-void fillings are observed in many of the clasts,including both detrital silt and coarse cement fillings (Figs. 5C–D).Detrital silt-filled voids are large areas (,3–15 cm) containing red-pink,hematitic quartz, feldspar, and carbonate sand that display well-developed depositional lamination and other geopetal features. Theseinfilled voids are interpreted as post-depositional infilling of inter-reefvoid spaces. Coarse cement-filled voids are smaller areas (,0.5–4 cm)filled with a meniscus-rim cement of medium crystalline calcite sparthat grades inward to coarsely crystalline calcite spar (Fig. 5D).

Crinoid Packstone-Grainstone Lithofacies.—Subordinate detritalclasts at the locality are composed of well-sorted and well-roundedcrinoid packstone-grainstone (Figs. 5B, 6A–B). The assignment ofcrinoid ossicles to ‘‘Pentacrinus,’’ a typical Triassic–Jurassic form, ismade only on the fragments of columnals. Lesser amounts offoraminifers, fragments of calcareous algae, and molluscan skeletaldebris also are present. This crinoid packstone-grainstone facies isinterpreted to represent a shallow-water, subtidal back-reef or fore-reefshoal (Lehrmann et al., 1998; Chablais et al., 2009; Flugel andMunnecke, 2010). The dominance of well-rounded crinoid ossicles and,to a lesser extent, other well-rounded skeletal grains is indicative ofredeposition and transport in a high-energy setting.

Spongiomorph-Algal Grainstone Lithofacies.—Other clasts in theWillow Spring conglomerate consist of a spongiomorph-algal grain-stone (Figs. 6C–E), characterized as a fine-grained, light-gray limestonecontaining encrusting platy green algae and the late Triassic Spongio-morpha ramosa, traditionally regarded as a hydrozoan but alsointerpreted as a sponge or coral (Ezzoubair and Gautret, 1993;Roniewicz, 2011). Allochems associated with this facies include well-sorted and well-rounded intraclasts of S. ramosa, molluscan andechinoderm fragments, and unidentified calcified algae. The dominanceof spongiomorphs and calcified algae, paired with echinoderm andmolluscan debris, suggests a high energy shallow-subtidal, back-reefenvironment (Flugel and Munnecke, 2010).

DISCUSSION

Triassic Reef-Building Organisms in the Olds Ferry Terrane

This study marks the first discovery of Upper Triassic reefallithofacies and reef-building fossils in the Olds Ferry terrane.Kuhnastraea cowichanensis was first described from Rhaetian rockson Vancouver Island by Clapp and Shimer (1911) and later fromAlaska by Caruthers and Stanley (2008). The spongiomorph, S. ramosa,is a well-known Norian–Rhaetian reef builder that is widely distributedacross the Tethys and western North America (Smith, 1927; Stanleyand Whalen, 1989; Flugel, 2002; Caruthers and Stanley, 2008). Both ofthese taxa are previously known from the Martin Bridge Formation ofthe Wallowa terrane (Stanley and Whalen, 1989) and also aredistributed in Upper Triassic carbonate rocks of Wrangellia and the

Alexander terrane, Alaska (Caruthers and Stanley, 2008). Thebranching coral Paracuifia sp. is closely related to P. magnifica,previously identified from the Pamir Mountains (Melnikova, 2001).This genus also was identified from the Alexander terrane (Caruthersand Stanley, 2008); however, the specimen present at the Willow Springlocality appears to be a new taxon. The low diversity of corals mayreflect incomplete sampling and limited availability of material forstudy.

In order to evaluate potential source areas for these limestone clasts itis necessary to understand the known distribution of coral taxa fromthe North American Cordillera, especially from terranes that arethought to have been in close paleogeographic proximity to the OldsFerry terrane. A recent compilation of Late Triassic coral data showsseveral taxa that are common throughout the Tethys Ocean and theNorth American Cordillera and therefore interpreted to be cosmopol-itan in nature (Caruthers and Stanley, 2008, table 2). Genera such asDistichophyllia, Retiophyllia, Gablonzeria, Kuhnastraea, Crassistella,Meandrostylis, and Astraeomorpha are generally diverse at the specieslevel and widespread in terrane localities from southern Alaska toMexico. They are also common in localities comprising the Wallowa,Alexander, and Wrangellia terranes, as well as an isolated locality nearLewiston, Idaho, which is suspected to be part of the Wallowa terrane(Stanley and Whalen, 1989; Nutzel and Erwin, 2004; Caruthers andStanley, 2008); however, the latter site does not contain Kuhnastraea orCrassistella (Squires, 1956; Caruthers and Stanley, 2008). Of the above-mentioned cosmopolitan genera, the new fauna from the Olds Ferryterrane contains only Kuhnastraea and is therefore somewhat prob-lematic. If the source area for these eroded limestone clasts was one ofthe well-known terrane sources (i.e., Wallowa, Alexander, andWrangellia terranes), then the fauna would most probably contain ahigher diversity of cosmopolitan genera, but again, limited samplingand exposure of the Willow Creek locality may have affected diversity.

Paracuifia has previously been identified only from the Alexanderand northern Wrangellia terranes; its presence in the Olds Ferry terraneis compelling because it may suggest either a paleobiogeographic tie tothese terranes or a broadening of the geographic distribution of thistaxon. Because there does not seem to be a strong influence of othercosmopolitan or endemic coral genera within the Olds Ferry terrane, awider geographic distribution of Paracuifia may be indicated.

Reef-Clast Source Area

The distinctive limestone-clast conglomerate of Willow Spring wasdeposited during the Early Jurassic, prior to ca. 188–187 Ma (Tumpane,2010), and thus represents reworking of older, Upper Triassic reefdeposits. Regionally, we know of two possible source areas of UpperTriassic reefal limestone and suggest a third possibility: (1) reefs in theWallowa intraoceanic arc terrane (Stanley and Senowbari-Daryan,1986; Stanley et al., 2008), (2) marble currently exposed in the Baker

TABLE 1—Descriptions of lithofacies in limestone clasts from the upper Huntington Formation.

Lithofacies Predominant biota Subordinate biota Fossil taxa Sedimentary structures and textures

Environmental

interpretation

Coral boundstone-

bafflestone

Colonial corals including

dendroid-phaceloid and

cerioid morphologies, and

sponges

Fragmental algae, crinoids,

echinoids, bivalves, and

gastropods

Paracuifia sp., Kuhnastraea

cowichanensis,

Spongiomorpha ramosa

Detrital silt filled voids (,3–15 cm)

containing red-pink, hematitic

quartz, feldspar, and carbonate

sand. Coarse cement-filled voids

are (,0.5–4 cm). Well-rounded

skeletal grains

Shallow subtidal,

high-energy reef

setting

Crinoid packstone-

grainstone

Crinoid occicles Foraminifers, fragmental

calcareous algae and

molluscan debris

‘‘Pentacrinus’’ Well-rounded skeletal grains Shallow subtidal, high

energy back-reef or

fore-reef shoals

Spongiomorph-algal

grainstone

Spongiomorphs, algae Fragmental calcareous

encrusting platy green

algae and molluscan debris

Spongiomorpha ramosa Well-rounded skeletal grains,

rounded intraclasts of

Spongiomorpha ramosa

Shallow-subtidal, high

energy back-reef

PALAIOS DETRITAL RECORD OF UPPER TRIASSIC REEF FACIES 783

terrane subduction-accretionary complex (Prostka, 1967; Morris andWardlaw, 1986), and (3) reefs associated with the Olds Ferrypericratonic arc terrane that are no longer exposed in the region.

Wallowa Terrane Source.—The Upper Triassic Summit Pointmember reef facies of the Wallowa terrane contains two coral taxaalso found in the Willow Spring conglomerate, K. cowichanensis and S.

ramosa. If the Willow Spring limestone clasts were eroded from theSummit Point reef, it would indicate proximity of the Wallowa andOlds Ferry terranes by the early Jurassic. This scenario supports

evidence for late Triassic–early Jurassic collision of the Wallowa andOlds Ferry terranes (i.e., Dorsey and LaMaskin, 2007) and is incontrast to models of late Jurassic collision between the two island arcterranes (i.e., Dickinson, 1979, 2004; Ave Lallemant, 1995; Schwartz etal., 2011).

Reef facies and fossils of the Summit Point member type also occur inmiddle Norian to Pliensbachian clastic turbidites (Excelsior Gulchmember of the Hurwal Formation) of the Wallowa terrane, where theyoccur in conglomerate-breccia clasts along with volcanic and chert

FIGURE 6—Photomicrographs of carbonate lithofacies types. A–B) Crinoid grainstone-packstone. C–E) Spongiomorph-algal grainstone. F) Coral boundstone-bafflestone.

784 LAMASKIN ET AL. PALAIOS

clasts (Flugel et al., 1989; Follo, 1992, 1994). Ongoing research byRosenblatt and Stanley suggests that this material was reworkedsubaerially from the Summit Point reefs and redeposited.

It is also possible that reef deposits of Wallowa affinity became asource area for detritus only after they were tectonically incorporatedinto the northern margin of the Baker terrane. This margin has beeninterpreted as a .25-km-wide zone that includes metamorphosedUpper Triassic rocks of possible Wallowa terrane affinity infaulted withrocks of the Baker terrane (Schwartz et al., 2010). In this scenario,Upper Triassic reefs would have been tectonically transferred from anoffshore, intraoceanic arc (Wallowa terrane) to a subduction-accre-tionary complex (Baker terrane) following Upper Triassic depositionand subsequently uplifted, eroded, and deposited into a pericratonic arcsuccession (Olds Ferry terrane) in the early Jurassic.

Baker Terrane Source.—These clasts may be derived from UpperTriassic carbonate rocks of the Nelson Marble, currently exposed in theBaker terrane subduction-accretionary complex. Conodonts recoveredfrom exposures of the marble and probable equivalents includeNeogondolella navicula, N. polygnathiformis, and Xaniognathus sp.,suggesting a range of middle–late Triassic (Morris and Wardlaw, 1986).The marbles are strongly recrystallized as a result of late Jurassicdeformation (Ave Lallement, 1995) and abundant local quartz dioriteintrusions (Prostka, 1967), and macrofossil identification has not beenpossible to date. Derivation of these clasts from the Nelson Marblewould indicate proximity of the Baker subduction-accretionarycomplex and the Olds Ferry pericratonic arc by early Jurassic time.This paleogeographic interpretation is supported by numerous studiesand reinforces the concept that portions of the Baker terrane representforearc crust and the accretionary prism to the Olds Ferry terrane (e.g.,Dickinson, 1979; Ave Lallemant, 1995; Vallier, 1995; Dorsey andLaMaskin, 2007; Schwartz et al., 2010).

If the Nelson Marble is itself an olistostromal body, it may beintrabasinal with respect to the Baker terrane subduction-accretionarycomplex, or extrabasinal, having a Wallowa-terrane provenance. Thissuggests, in turn, that the detrital coral fauna of Willow Springdescribed here may be a multicyclic deposit. In this scenario, the firstcycle is represented by olistostromal sliding of carbonate megaclasts ofWallowa- or Baker-terrane affinity into a marine basin floored byBaker terrane subduction-accretionary complex rocks. The second cycle

involves post-Norian, pre-Pliensbachian uplift and erosion (,10 myrduration) of the Baker terrane-floored basin and subsequent depositionof the Willow Spring carbonate conglomerate in a marine forearc basinfloored by pericratonic arc rocks of the Olds Ferry terrane.

Olds Ferry Terrane Source.—Willow Spring limestone clasts may bewholly intrabasinal, eroded from Upper Triassic reefal limestone that isnot currently exposed in the Olds Ferry terrane. Exposures of thin-bedded, Upper Triassic deep-water limestones are locally present, buthave been interpreted to represent a heterozoan faunal assemblage (i.e.,non-tropical-type deposition represented by fragmental allochems ofechinoderms and mollusks; LaMaskin, 2008). These observations andinterpretations suggest that typical reef deposition did not occur in theOlds Ferry pericratonic arc region during the late Triassic andtherefore, a source area within the Olds Ferry terrane is not supported.

Conversely, it is believed that a wide range of factors can restrictgrowth of photozoan carbonates and lead to deposition of a heterozoancool-water community in a regionally warm-water setting (Westphal etal., 2010). These factors may include both global-regional factors (e.g.,elevated trophic conditions, oceanographic instability, increasednutrient load from runoff, or cold-water intrusion in upwelling zones)and more local factors (e.g., high water energies or geographicalisolation; Whalen, 1995; James, 1997; Parrish et al., 2001, Pomar et al.,2004; Westphal et al., 2010). Thus, it is possible that during the lateTriassic, both heterozoan- and photozoan-favoring conditions existedin the Olds Ferry terrane. If so, then both the in situ Upper Triassicdeep-water limestone (LaMaskin, 2008) and the Upper Triassic detritallimestone clasts in the upper member of the Huntington Formationrepresent deposits of Olds Ferry affinity.

The observation that non-limestone clast and framework grain typesappear to be restricted to rhyolite, rhyodacite porphyry, and basalt toandesite is suggestive of an intrabasinal, local source; these rock typesare interbedded locally with the conglomerate deposits and are presentin the lower and upper Huntington Formation. All of the observeddetritus in the Willow Spring conglomerate, except for the UpperTriassic reefal lithofacies, can be accounted for locally (Brooks andVallier, 1978; Brooks, 1979; Charvet et al., 1990; Tumpane, 2010). Thelack of other recycled Wallowa terrane or Baker terrane detritus (e.g.,quartzose metasedimentary, radiolarian chert) in associated sandstonesor conglomerate matrix is strong evidence for an intrabasinal origin.

TABLE 2—Cross-reference of late Triassic reef taxa between major western North American terranes.

Species

Blue Mountains Wrangelia

Alexander Tethys Stratigraphic range and North American locationsOlds Ferry Wallowa S N

Paracuifia sp. 3 Huntington Formation, Olds Ferry terrane, Oregon

P. smithi n. sp. 3 Early Norian, Gravina Island, Alaska (Caruthers and Stanley, 2008)

P. jennieae n. sp. 3 Early Norian, Cornwallis Limestone, Keku Strait, southeastern Alaska;

Chitistone Formation, Wrangell Mountains (Caruthers and Stanley, 2008)

P. anomala n. sp. 3 Early Norian, Nehenta Formation, Gravina Island, southeastern Alaska

(Caruthers and Stanley, 2008)

Kuhnastraea

cowichanensis

3 3 3 3 3 Early Norian–Rhaetian; Vancouver Island, Canada; Gravina Island, Keku Strait,

Wrangell Mountains, Alaska; Hells Canyon, Oregon (Smith, 1927;

Montanaro-Gallitelli et al., 1979; Melnikova and Bychkov, 1986; Stanley and

Whalen, 1989; Caruthers and Stanley, 2008)

K. decussata 3 3 3 3 3 Rhaetian, Vancouver Island, Canada; Northern Calcareous Alps; Norian,

Gravina Island, Keku Strait, Wrangell Mountains, Iliamna Lake, Peninsula,

Alaska; Hells Canyon, Oregon; Shasta County, California; Pilot Mountains,

Nevada (Roniewicz, 1989; Stanley and Whalen, 1989; Caruthers and Stanley,

2008)

K. incrassata 3 3 3 Rhaetian, Vancouver Island, Canada; Norian–Rhaetian; early Norian, Hells

Canyon, Oregon (Roniewicz, 1989; Stanley and Whalen, 1989; Caruthers and

Stanley, 2008)

Spongiomorpha

ramosa

3 3 3 3 3 3 Early Norian–Rhaetian, Long Creek, Alaska; Cedar Creek, Shasta County,

California; Brock Mountain, California, Hosselkus Limestone Formation;

Martin Bridge Formation, Hells Canyon, Oregon (Smith, 1927; Stanley and

Whalen, 1989; Stanley and Yarnell, 2003; Caruthers and Stanley, 2008)

PALAIOS DETRITAL RECORD OF UPPER TRIASSIC REEF FACIES 785

The first and second scenarios above require that any sedimenttransport and deposition system carrying detrital limestone clastseroded from the uplifted Wallowa intraoceanic arc or Baker terranesubduction-accretionary complex would include detrital grains andclasts representative of other Wallowa or Baker terrane lithologies.Detrital grains and clasts of quartzose metasedimentary lithologies andradiolarian chert are absent from the Willow Spring location. Based onthis key observation, we suggest that the source of late Triassic coral-sponge reef faunas in the upper member of the Huntington Formation(Lower Jurassic) was intrabasinal and that the source rocks are nolonger exposed in the region. This interpretation suggests that duringthe late Triassic, conditions were favorable for deposition of reefal

limestone in all of the terranes of the Blue Mountains Province. Assuch, the presence of Upper Triassic limestone cannot be used to inferlithologic correlation between the terranes of the region (including theSalmon River Belt). Importantly, the potential regional source areasdiscussed above preclude the need to call upon sourcing from other,more exotic terranes of the Cordillera. Furthermore, the absence of keycosmopolitan and endemic genera from the Willow Spring site of theOlds Ferry terrane does not support the Wallowa, Alexander, orWrangellia terranes as being potential sources for the limestone clastsof the upper Huntington Formation. Similarly, the absence ofKuhnastraea from the Lewiston, Idaho locality also argues against thisarea as a potential source. Thus, faunal data suggest that this low-

FIGURE 7—Representative faunal elements. A–B) Kuhnastraea cowichanensis; A) Colony showing corallite arrangement; B) Longitudinal view of septal growth; C–E)

Paracuifia n. sp.; C) Close up of corallite showing lonsdaleiod dissepiments; D) Longitudinal view; E) Colony illustrating varying ontogenetic corallite size; F) Spongiomorpha

ramosa; transverse view illustrating branching character.

786 LAMASKIN ET AL. PALAIOS

diversity coral assemblage from the Olds Ferry pericratonic arc terranewas likely derived locally. In detrital reef deposits, careful analysis ofpossible uplift-and-erosion scenarios, in combination with petrographicobservations, is required to make an accurate determination of clastorigin.

Significance of Discovery

The reefal, coral-sponge fauna described herein indicates a Tethyanaffinity for Upper Triassic rocks of the Olds Ferry terrane. This is inconcurrence with halobiid bivalve and ammonite collections from thethin-bedded, deep-water limestone unit of the Huntington Formation(Brooks, 1979; LaMaskin, 2008). As shown in Table 3, late Triassicfaunas, including reef lithofacies, are preserved in allochthonousterranes throughout the western North American Cordillera. Ourdiscovery at Willow Spring in the Olds Ferry terrane represents a newwestern North American Cordilleran record of Upper Triassic reefdeposits.

Identical taxa (Kuhnastraea cowichanensis and Spongiomorpharamosa) have been found in numerous terranes of the western NorthAmerican Cordillera. The co-occurrence of these taxa in the Wallowaand Olds Ferry terranes suggests that during the late Triassic theseregions may have been in proximity to one another, an interpretationthat supports tectonic models wherein the Wallowa, Baker, and OldsFerry terranes were amalgamated offshore during the late Triassic–early Jurassic (Dorsey and LaMaskin, 2007; LaMaskin et al., 2011).The presence of these taxa in northern and southern Wrangellianlocations (i.e., Alaska and Vancouver Island, British Columbia,respectively) and within the Alexander terrane in southeastern Alaska,however, suggests that these taxa had a cosmopolitan distribution andare not necessarily good indicators of terrane proximity during the lateTriassic.

CONCLUSIONS

1. A late Triassic coral-sponge reef fauna from a thick-bedded,cobble-to-boulder conglomerate in the informal upper member of theLower Jurassic Huntington Formation near Huntington, Oregon,United States, represents the first discovery of reef-building lithofaciesand fossils of this age in the Olds Ferry terrane.

2. Corals at the site include a high-growing, dendroid-phaceloidspecies that acted as either framework or sediment baffles, and a low-growing, cerioid, encrusting coral and a sponge that acted as sediment

binders. Together, these organisms produced at least a 10–50 cm highreef-like or reefal framework.

3. Framework mineralogy of sandstones and clast types in theconglomerate suggest that the source of these Triassic coral-sponge reeffaunas was intrabasinal.

4. The occurrence of the same two coral taxa in the Wallowa andOlds Ferry terranes may support the proximity of these two regions inthe late Triassic, but the presence of these taxa in other Cordilleranterranes suggests that they are probably cosmopolitan and therefore notgood indicators of terrane proximity.

ACKNOWLEDGMENTS

Funding was provided by grants to T.A.L. from the Weimer fund ofSEPM (The Society for Sedimentary Geology), the Geological Societyof America, Sigma Xi, AAPG (American Association of PetroleumGeologists), and the Baldwin Fellowship at the University of Oregon.Assistance with fossil collection was provided by T. Sieber. G.D.S.acknowledges support by the National Science Foundation (EAR-0229795). We thank Editor Edith L. Taylor, Associate Editor WolfgangKiessling, reviewer M. Bernecker, and an anonymous reviewer forimproving the readability and broader applicability of the manuscript.

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ACCEPTED SEPTEMBER 15, 2011

PALAIOS DETRITAL RECORD OF UPPER TRIASSIC REEF FACIES 789