Article

Middle-Late radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate (Wallowa terrane, Oregon, U.S.A.)

KHALIL, Hany, et al.

Abstract

New radiolarian data from the polymict Excelsior Gulch conglomerate (Wallowa terrane, Blue Mountains Province, Oregon, USA)allow narrowing the age of the chert components. Chert clasts sampled at three distinct localities yielded radiolarians that have Middle to Late Triassic ranges. Individual taxon ranges allow for the distinction of four continuous substages: early Ladinian (presence of Triassocampe nishimurae and T. postdeweveri), middle Ladinian (with Pseudotriassocampe hungarica), late Ladinian (presence of Muelleritortis cochleata and Tritortis kretaensis), and early Carnian (with the co-occurrence of species such as Muelleritortis spp. ex. gr. M. cochleata, Tritortis dispiralis, ?Corum delgado and Triassocingula perornatum). The reworked chert clasts represent Middle to Late Triassic Panthalassan open ocean sediments that have not been described in the Blue Mountains Province.

Reference

KHALIL, Hany, et al. Middle-Late Triassic radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate (Wallowa terrane, Oregon, U.S.A.). Revue de Paléobiologie, 2020, vol. 39, no. 2, p. 565-579

DOI : 10.5281/zenodo.4465568

Available at: http://archive-ouverte.unige.ch/unige:148434

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Revue de Paléobiologie, Genève (décembre 2020) 39 (2): 565-579 ISSN 0253-6730

Middle-Late Triassic radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate (Wallowa terrane, Oregon, U.S.A.)

Hany Khalil1,2, Peter O. Baumgartner3, Tetsuji Onoue4, Nicolò Del Piero2, George Stanley Jr.5, Sylvain Rigaud6 & Rossana Martini2

1 Department of Geology, Alexandria University, Moharam Bey, 21511 Alexandria, Egypt. E-mail: geo.hmk@gmail. com, [email protected] 2 Department of Earth Sciences, University of Geneva, 13 rue des Maraîchers, CH-1205 Genève, Switzerland. E-mail: [email protected], [email protected] 3 Institute of Earth Sciences, University of Lausanne, Bâtiment Géopolis, CH-1015 Lausanne, Switzerland. E-mail: [email protected] 4 Department of Earth and Environmental Sciences, Kumamoto University, Kumamoto, 860-8555 Japan. E-mail: [email protected] 5 Department of Geosciences CHCB 302, 32 Campus Drive #1296, Missoula, MT 59812 USA. E-mail: george.stanley@ umontana.edu 6 Asian School of the Environment, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459. E-mail: [email protected]

Abstract New radiolarian data from the polymict Excelsior Gulch conglomerate (Wallowa terrane, Blue Mountains Province, Oregon, USA) allow narrowing the age of the chert components. Chert clasts sampled at three distinct localities yielded radiolarians that have Middle to Late Triassic ranges. Individual taxon ranges allow for the distinction of four continuous substages: early Ladinian (presence of Triassocampe nishimurae and T. postdeweveri), middle Ladinian (with Pseudotriassocampe hungarica), late Ladinian (presence of Muelleritortis cochleata and Tritortis kretaensis), and early Carnian (with the co-occurrence of species such as Muelleritortis spp. ex. gr. M. cochleata, Tritortis dispiralis, ?Corum delgado and Triassocingula perornatum). The reworked chert clasts represent Middle to Late Triassic Panthalassan open ocean sediments that have not been described in the Blue Mountains Province.

Keywords Excelsior Gulch conglomerate, Wallowa terrane, Blue Mountains Province, reworked Middle-Late Triassic Radiolaria.

1. Introduction important part of the tectonic and stratigraphic history of the Wallowa terrane. It is notably suspected to be a The Excelsior Gulch conglomerate is the youngest dated key unit to link terranes of the Blue Mountains Province sedimentary unit of the southern Wallowa Mountains, and to better constrain their geodynamic evolution Oregon (Follo, 1986, 1992, 1994). The unit records an (e.g., Follo, 1992). Many aspects of this conglomerate, unusual composition of polymictic conglomerate mainly however, remain a matter of conjecture since both its age consisting of limestone, volcanic and volcaniclastic and source, or sources, are uncertain. rocks, and radiolarian cherts. All observed rock types The conglomerate of the Excelsior Gulch unit, in the commonly form rounded clasts, evidencing that a fluvial southern Wallowa Mountains, were first investigated at transport took place prior to their deposition on the top the top of a ridge, east of Excelsior Gulch, where they of deep-basin argillites of the Hurwal Formation (Follo, directly overlie deep-water basinal sediments of the 1986, 1992). As radiolarian cherts are not found in Hurwal Formation (Follo, 1986). Hurwal sedimentary other parts of the Wallowa terrane, this conglomeratic rocks, with a total thickness of 400-500 m in the southern unit is regarded allochthonous and thought to record an Wallowa (Follo, 1986), are mainly formed by dark grey

Submitted October 2017, accepted May 2020 Editorial handling: L. Cavin DOI: 10.5281/zenodo.4465568 566 H. Khalil et al.

to brown argillites, possibly intercalated with calcareous zone) through the middle Norian (M. columbianus zone) siltstone and limestone along with volcanic tuffs (Follo, in North America and north-eastern Asia (McRoberts, 1986). They contain abundant fossils and display sedi­ 1993, 1997, 2011). A middle Norian age range would mentary structures like cross bedding, convolute bedding, be in accordance with new data from U-Pb analyses of channel scours and fills with some rip-up clasts. detrital zircons of lower middle Norian age (ca. 215 Ma) Follo (1986, 1992) designated the Excelsior Gulch (Massoll & LaMaskin, 2016). conglomerate as a separate stratigraphic unit and regarded This paper provides new radiolarian data from chert the depositional conditions as deep. Absence of visible clasts of the Excelsior Gulch conglomerate. signs of reworking or unconformity led Follo to describe these (elsewhere erosive) levels as conformable, on the top of deep basinal sedimentary rocks of the Hurwal 2. Geological settings Formation. Follo reported a well-preserved Halobia sp. cf. H. cordillerana and the belemnoid Aulacoceras sp. The Blue Mountains Province (Fig. 1) extends from from beds above the first chert-rich pebbly sandstones. He central Oregon north-eastward into Idaho as a part used these occurrences to date the base of the Excelsior of the Columbia embayment. It is composed of four Gulch conglomerate as early Norian. However, this age tectonostratigraphic terranes (Brooks & Vallier, 1978; assignment is no longer valid, because H. cordillerana Dickinson & Thayer, 1978). From the most outboard is now known to range from the lower Norian (S. kerri position with regard to the North American Craton, these

Fig. 1: Fig. 1.1: Location of the Blue Mountains Province in NW USA. WA, Washington State; OR, Oregon State; ID, Idaho State. Fig. 1.2: Regional geologic map of the Blue Mountains Province. JM, Juniper Mountain; H, Huntington; BC, Baker City; JD, John Day; IM, Ironside Mountain; CMC, Canyon Mountain Complex; DB, Dixie Butte; MI, Mitchell Inlier; BMQ, Black Marble Quarry; BMB, Bald Mountain Batholith; WB, Wallowa Batholith; CH, Coon Hollow; CM, Cuddy Mountains; IB, Idaho Batholith; SC, Sparta Complex; O, Oxbow; SDM, Seven Devils Mountains; PL, Pittsburg Landing; MH, Mountain Home; MCQ, Mission Creek Quarry. Modified from LaMaskin et al. (2011). Rectangle indicates location of Fig. 2. Radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate 567

terranes are: (i) the Wallowa intraoceanic arc terrane Formation (Follo, 1992). They were informally named the (e.g., Vallier, 1977; Walker, 1986); (ii) the Baker terrane, Excelsior Gulch conglomerate in the southern Wallowa a subduction-accretion complex (Brooks & Vallier, Mountains (Follo, 1986) and the Deadman Lake breccia 1978; Coward, 1983); (iii) the Triassic to clastic in the northern Wallowa Mountains (Nolf, 1966). sedimentary succession of the Izee terrane (Silberling The Excelsior Gulch conglomerate has been regarded as et al., 1984), which originally rested depositionally a member of the Hurwal Formation (Follo, 1986). It is an on the Baker terrane (Brooks, 1979; Dickinson, 1979; 80-100 m thick sequence of polymict pebbly sandstones Silberling et al., 1984; Tumpane, 2010); and (iv) the to clast-supported, poorly sorted conglomerate, with Olds Ferry pericratonic arc terrane, which represents the abundant rounded reef-type limestone, argillites and most inboard position of the province (Brooks & Vallier, rounded to subrounded volcanic clasts, along with less 1978; Brooks, 1979). These terranes are discontinuously abundant clasts of coarse-grained intrusive rocks (e.g., exposed, as erosional inliers and intruded by a Late quartzite), metamorphic rocks (e.g., greenstones) and Mesozoic plutonic complex (e.g., Walker, 1977; Orr et radiolarian-bearing cherts (Flügel et al., 1989; Follo, al., 1992). Numerous studies consider that terranes of the 1992). This conglomerate were mapped in isolated Blue Mountains were first located outboard of the area outcrops (e.g., Excelsior Gulch, Red Gulch, Sanger that forms today NW Nevada (Dorsey & LaMaskin, 2007; Gulch, O’Brien and East Eagle Creek) throughout the LaMaskin et al., 2011) with a N-S orientation during the southern Wallowa Mountains (Lundblad, 1985; Follo, Triassic and Jurassic, and later rotated 60° clockwise 1986). Other chert-rich, minor localities of possible (Wilson & Cox, 1980). The rotation was in relation to Excelsior Gulch affinity (limestone-rich conglomerate), late right lateral strike slip faulting, which were reported along Goose Creek, Larkspur Creek, and would have led to a displacement of about 400 km of the Paddy Creek (Rigaud, 2012) but these cherts are probably Blue Mountains Province, into its present position (see reworked (diagenetic) nodular cherts. It was stated Wilson & Cox, 1980; Housen & Dorsey, 2005; Housen, that the sub-rounding of some clasts, including highly 2007). resistant rock types, such as cherts and quartzite, along The stratigraphic succession of the Wallowa terrane rests with a decrease of the clast size and bedding thickness on a igneous and volcanic basement. It starts by in a northward direction, makes the nearby Baker terrane extensive Triassic volcanic and volcaniclastic rocks of a likely emerging source for the derivation of Excelsior the Seven Devils Group (e.g., Vallier et al., 1977; Vallier Gulch conglomerate (Blome et al., 1986; Follo, 1986, & Batiza, 1978; Kays et al., 2006). Its upper part has 1992). Later studies suggested a derivation of the been informally named the Lower Sedimentary Series in limestone clasts from isolated? Wallowa patch reefs the southern Wallowa Mountains (Prostka, 1963; Brooks growing on the shallow slope or shelf edge (Rosenblatt, & Vallier, 1978). These volcanoclastic rocks are overlain 2010; Rigaud, 2012). Since no other (originally bedded) by Upper Triassic (Upper Carnian - ?Lower/Middle radiolarian cherts have been observed in the Wallowa Norian) carbonate rocks of the Martin Bridge Formation terrane (Follo, 1986, 1992, 1994), at least the radiolarian (Ross, 1938; Follo, 1986, 1992; Khalil et al., 2018). The chert clasts in the Excelsior Gulch conglomerate are transition between the two formations is unclear due to regarded as allochthonous (Follo 1986, 1992). The poor exposure, as well as unsatisfactory paleontological Deadman Lake breccia has been described in detail by and sedimentological resolution, and probable structural Nolf (1966), and markedly differs from the Excelsior complications (Laudon, 1956; Nolf, 1966; Follo, 1986). Gulch conglomerate in lacking bedding and in being The abrupt facies changes in the southern Wallowa formed by less competent clasts and matrix. No cherts Mountains, encompassing shales, marls, organic-rich or igneous rocks have been recovered from this matrix- carbonates, and coarser-grained gravity flow limestone supported mega-breccia. In the Northern Wallowa breccias and other slope-related deposits, suggest a Mountains, Nolf (1966) studied limestone clasts at BC deeper depositional environment (?slope or basinal) Creek, where he reported some horizons marked by small than in the Northern Wallowa Mountains (Stanley, 1979; cherty nodules and rare limestone clasts, but lacking Follo, 1986). The sequence grades vertically, and possibly cherts originating from bedded radiolarian cherts like laterally, into a deep-water starved facies made of thick, the ones in Excelsior Gulch. The Baker terrane is the predominantly mudstone (or argillite due to low grade nearest source that comprises all rock types found in the metamorphism) deposits of the Upper Triassic-Lower Excelsior Gulch conglomerate, including bedded cherts, Jurassic Hurwal Formation, which is locally covered by limestone and altered greenstones (Brooks & Vallier, conglomerate of the Excelsior Gulch unit (Nolf, 1966; 1978; Follo, 1986; Dorsey & LaMaskin, 2007). Follo, 1986, 1992).

3. STUDIED LOCALITIES 2.1. The Excelsior Gulch conglomerate The Excelsior Gulch unit crops out in three major In the Wallowa terrane, two distinctive conglomeratic localities of the southern Wallowa Mountains: Excelsior units disrupt the otherwise rather homogeneous Hurwal Gulch, Red Gulch and O’Brien Gulch (Fig. 2), all 568 H. Khalil et al.

Fig. 2: Fig. 2.1: Location map of the studied localities in which conglomeratic rocks (Excelsior Gulch unit) crop out in the southern Wallowa Mountains (rectangles, enlarged below). In bold with black squares the main fossiliferous localities, of northern and southern Wallowa Mountains, and of lower part of Hells Canyon (Oregon State, NW U.S.A.), are also reported (modified from Follo, 1994). Fig. 2.2: Excelsior Gulch. Fig. 2.3: Red Gulch. Fig. 2.4: O’Brien. Radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate 569

of which were examined for their radiolarian cherts 3.3. O’Brien locality content. The sedimentological features of these outcrops are discussed here, based on field observations (e.g., The O’Brien locality crops out between O’Brien Creek composition and lithology of the clasts and matrix) and and Bradley Creek, near the U.S. forest service road on previous studies (Follo, 1986, 1992). 407 (Fig. 2.4) (45’01’’10ºN, 117’22’’35.7ºW). Three different units have been observed there, all noticeably metamorphosed: the Hurwal Formation at the base, 3.1. Excelsior Gulch type locality followed by Excelsior Gulch conglomerate and limestone (almost marble) breccias. Vegetation cover is too dense to This is Follo’s “type locality” of the Excelsior Gulch continuously follow the contact between these lithologies conglomerate (Fig. 3.1), selected for its great thickness but locally, the contact between the conglomerate and the and clear stratigraphic relationships with the underlying argillites and the conglomerate and the marble (Fig. 3.10: Hurwal Formation (Follo, 1986) (Fig. 3.2). This note that limestone-marble beds are 3-4 m thickness and conglomerate crop out near the confluence of Dixie dip at a subvertical 85° SSW angle) can be observed or Creek and Eagle Creek (45’00’’03.5ºN, 117’25’’28ºW), dug out. The Excelsior Gulch conglomerate dips 60° SSW. at an elevation range of 1280-1400 m. The conglomerate Graded bedding and scours (Fig. 3.11) in the Excelsior dips at a high angle above shales and calcareous argillites Gulch conglomerate allowed us to define the way-up of the Hurwal Formation. The ridge-top, formed by and place the conglomerate in erosional contact above volcanic rocks of the Columbia River Basalt, is marked the argillites of the Hurwal Formation and the limestone by an angular unconformity. Bedding sequences were breccia. Radiolarian cherts are scarce compared to other observed in this locality with beds up to several meters localities (Fig. 3.12). Topographically below the Excelsior in thickness (Fig. 3.3). The rocks are more resistant to Gulch conglomerate, but stratigraphically above, it lays weathering than surrounding lithologies and show a a 5-7 m interval of sandstones alternating with shales. To continuous succession of abundant volcanic gravels the west and northwest, the area is completely covered by and boulders (Fig. 3.4). More or less abundant and a thick soil and by vegetation. fossiliferous limestone clasts, and less abundant other rock types (e.g., quartzite, subordinate marls), set in a fine conglomeratic matrix also occur (Fig. 3.5). Translucent 4. MATERIALS AND METHODS blue to grey chert fragments are present but rare. They show moderate radiolarian preservation compared to More than 40 radiolarian-bearing chert clasts were other localities of Excelsior Gulch conglomerate. Clasts carefully selected in the above-mentioned localities. are recrystallized, poorly sorted, sub-rounded, and larger The clasts were processed by locality as three composite than those observed at O’Brien locality. samples. Radiolarians were extracted by the appropriate hydrofluoric acid method illustrated in Dumitrica (1970). 193 radiolarian specimens were recovered from the 3.2. Red Gulch locality chert samples using the methodology of Baumgartner The Red Gulch locality is located near Goose Creek et al. (1981), then studied in detail, measured and (Fig. 2.3) (44’56’’58.6ºN, 117’23’’37.7ºW). It is the photographed. outcrop of the Excelsior Gulch unit currently located closest to the Baker terrane, which lies to the South. The stratigraphic characteristics of the section are 5. RADIOLARIAN BIOSTRATIGRAPHY similar to that of the Excelsior Gulch type section (see Rosenblatt, 2010 for details). Frequent, 0.5-0.7 m Many Panthalassan oceanic terranes accreted onto sized conglomeratic blocks are observed all over the western North America have been successfully dated locality, with beds thickness also reaching few meters (Jones & Muchey, 1986; Blome et al., 1986; Cordey (Fig. 3.7). The clasts are moderately sorted, rounded to & Schiarizza, 1993) using extraction methods for subangular, set in a groundmass of a finer conglomerate. radiolarians from ribbon-bedded radiolarite rocks Their composition is the same as in the Excelsior Gulch (Dumitrica, 1970; Pessagno & Newport, 1972). It also locality, but it is obvious that limestone clasts are more has become evident that sedimentation of radiolarian abundant there. Flügel et al. (1989) mentioned that the ribbon bedded cherts (i.e., chert/shale couplets) were limestone clasts are Norian in age based on corals and dominant in low and middle paleo-latitude oceanic areas other reef biota (Figs 3.8, 3.9). Sampled chert fragments throughout the to early Late Cretaceous show the best radiolarian preservation, probably due to period (Cordey, 1998; Baumgartner, 2013). Our oceanic a greater distance from the Wallowa batholith and other radiolarite assemblages, from different chert clasts, were contact bodies responsible for contact metamorphism in too rare and poorly preserved to allow us for a detailed the area. analysis of each clast. Accordingly, our interpretation relies on the biostratigarphic range of each taxon recorded 570 H. Khalil et al.

Fig. 3: Field photographs of Excelsior Gulch unit (southern Wallowa Mountains, Oregon). Fig. 3.1: Excelsior Gulch type locality. Fig. 3.2: Conglomerate at Excelsior Gulch type locality overlying argillites of the Hurwal Fm. Fig. 3.3: Bedding in conglomerate at Excelsior Gulch type locality. Fig. 3.4: Large conglomerate blocks at Excelsior Gulch type locality. Fig. 3.5: Different clasts with matrix within the conglomerate blocks at Excelsior Gulch type locality. Fig. 3.6: Deadman Lake breccia outcrop east of Frances Lake, majority made of argillites (blocks and matrix). Fig. 3.7: Beds at Red Gulch locality. Fig. 3.8, 3.9: Fossiliferous limestone blocks at Red Gulch locality. Fig. 3.10: Picture showing the erosive contact above the limestone breccia at O’Brien locality. Fig. 3.11: Erosive surface within the conglomerate at O’Brien locality. Fig. 3.12: Conglomeratic level at O’Brien locality. Radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate 571

at the 3 studied localities. It is important to notice that (ii) At Red Gulch, the co-occurrence of Muelleritortis individual taxon ranges are quite homogeneous amongst cochleata (late Ladinian), several species the 3 localities (Table 1). They indicate, for the majority belonging to Tritortis, including T. kretaensis (late of taxa, a middle-late Ladinian to early Carnian (late late Ladinian), T. dispiralis (late Ladinian-early Middle to early Late Triassic) age. A few taxa indicate Carnian) and Corum (?) delgado (early-middle reworking of older, early Ladinian, material. Carnian) indicate reworking of at least late Ladinian Since most of the specimens are poorly to moderately to early Carnian radiolarites. On the other hand, the preserved, the determined taxa are assigned to genera and presence of Pseudotriassocampe hungarica point to in many cases questionably to species (see systematics the reworking of strictly middle Ladinian material and Pl. I): while the occurrence of Triassocampe nishimurae (i) At the Excelsior Gulch locality, we recovered several and T. postdeweveri point to the reworking of older, specimens of Muelleritortis spp. ex gr. M. cochleata strictly early Ladinian radiolarites. As a whole, that would argue for a late Ladinian-early Carnian the assemblage points to the reworking of early age, but specimens of Pseudotriassocampe sp. Ladinian to early Carnian radiolarites. However, additionally point to reworking of undifferentiated additional reworking of older and younger material middle Anisian-middle Ladinian material. The cannot be fully excluded due to the presence of wider range taxa Triassocampe spp. (late Anisian- long range taxa such as Pararuesticyrtium illyricum Ladinian, according to Thassanapak et al., 2011) (late Anisian-early Ladinian), ?Pseudostylosphaera and Annulotriassocampe sp. (middle Anisian- sp. cf. P. longispinosa (Anisian-early Ladinian), middle Norian) have also been recovered from that Pylostephanidium sp. (late Anisian-middle Car­ locality. nian), Pseudostylosphaera nazarovi (late Ladinian-­

Table 1: Ranges of radiolarian taxa, according to the literature cited under systematics, occurring in the three studied localities: Excelsior Gulch, Red Gulch and O’Brien. Note that 5 taxa have a narrow range (one substage: T. nishimurae; T. postdeweveri; P. hungarica; M. cochleata; T. kretaensis) and that two taxa have their FO in the early Carnian [C. (?) Delgado; T. perornatua].

Localities

Anisian Ladinian Carnian Norian Taxon

Excelsior Gulch Gulch Red O’Brien E M L E M L E M L E M L ?Pseudostylosphaera sp. cf. P. longispinosa Pseudotriassocampe sp. Pararuesticyrtium sp. Annulotriassocampe sp. Pylostephanidium sp. Pararuesticyrtium illyricum Pseudostylosphaera nazarovi Triassocampe spp. Triassocampe nishimurae Triassocampe postdeweveri Multimonilis sp. Pseudotriassocampe hungarica Muelleritortis cochleata Tritortis kretaensis Muelleritortis spp. ex. gr. M. cochleata Tritortis dispiralis Corum (?) delgado Triassocingula perornatua 572 H. Khalil et al.

middle Carnian), Multimonilis sp. (Ladinian-middle Range: Anisian to early Ladinian (Thassanapak et al., Norian), and Triassocingula perornata (Carnian- 2011). Norian). (iii) At O’Brien, the chert samples show, besides sponge Subfamily Muelleritortiinae Kozur, 1988 spicules, only one inner mold of a Pararuesticyrtium Pl. I, figs 7-9 sp. indicating a middle Anisian to early Norian age. Remarks: Here we include untwisted hexacarinate spines that have a secondary, narrow and short median 6. SYSTEMATICS groove on the wedges of the divided ridges. Range: Ladinian to early Carnian (O’Dogherty et al., Class Radiolaria Müller, 1858 2009). Subclass Polycystina Ehrenberg, 1838 [emend. Riedel, 1967] Genus Muelleritortis Kozur, 1988 Order Entactinaria Kozur & Mostler, 1982 Family Eptingiidae Dumitrica, 1978 Muelleritortis spp. ex gr. M. cochleata (Nakaseko & Genus Pylostephanidium sp. Dumitrica, 1978 Nishimura, 1979) Pl. I, fig. 1 Pl. I, figs 10-19

Remarks: The figured, poorly preserved Pylostepha­ Remarks: The specimens are poorly preserved. nidium sp. is characterized by a subtriangular test. However, in Pl. I, figs 15, 18 we can notice subquadratic The three, needle-shaped spines marking the terminal to quadratic cortical shell with one sinistrally-twisted, ends of the test are only partially preserved, and pore three-sided spine, and traces of other (up to 3) spines configuration cannot be confidently described due to in cross-like arrangement. This form resembles poor preservation. Muelleritortis cochleata (Nakaseko & Nishimura, 1979), Range: Late Anisian to middle Carnian (Dumitrica et al., which possesses four spines. In Pl. I, figs 16, 17 only 2010). one sinistrally-twisted, three-sided spine is sufficiently preserved, in Pl. I, figs 10-14 two spines are missing, Family Hexapylomellidae Kozur & Mostler, 1981 there is no indication for the other spines, which casts Subfamily Hindeospaerinae Kozur & Mostler, 1981 doubt on its assignment to the genus Muelleritortis. Genus Pseudostylosphaera Kozur & Mostler, 1981 Range: Late Ladinian and basal early Carnian (Bragin, 2011). Pseudostylosphaera nazarovi Kozur & Mostler, 1979 Muelleritortis cochleata (Nakaseko Pl. I, figs 2, 3 & Nishimura, 1979) Pl. I, fig. 20 Remarks: In our material only one of the two spines that characterize Pseudostylosphaera nazarovi is preserved. 1979. Emiluvia (?) cochleata Nakaseko & Nishimura, p. 70, pl. The base of the other, broken spine is visible in specimen 3, figs 2-4, 6. 4.2. 1988. Muelleritortis cochleata cochleata (Nakaseko & Nishi- Range: Late Ladinian to middle Carnian (Tekin, 1999). mura).– Kozur, p. 53, pl. l, figs 1-8; pl. 2, figs 1, 2; pl. 3, fig. 1. ?Pseudostylosphaera sp. cf. P. longispinosa 1988. Muelleritortis cochleata koeveskalensis Kozur, pp. Kozur & Mostler, 1981 53-54, pl. 3, fig. 3. Pl. I, figs 4-6 1988. Muelleritortis cochleata tumidospina Kozur, p. 54, pl. 3, fig. 2. 1996. Muelleritortis cochleata (Nakaseko & Nishimura).– 1981. Pseudostylosphaera longispinosa Kozur & Mostler, Kozur & Mostler, p. 86, pl. 1, figs 6, 7, 9, 10; pl. 2, figs.1, p. 32, pl. 1, fig. 6. 4, 8; pl. 3, figs 1, 3. 1999. Pseudostylosphaera longispinosa Kozur & Mostler.– Tekin, p. 129, pl. 25, fig. 14. 2011. Pseudostylosphaera longispinosa Kozur & Mostler.– Remarks: The degree of preservation does not allow Thassanapak et al., p. 195, fig. 6T. further identification (subspecies level) but the four spines are clearly visible. Remarks: The specimen of Fig. 4.5 differs slightly Range: Late Ladinian (Budurovignathus mungoensis from Pseudostylosphaera longispinosa in that the spines conodont zone). M. cochleata Zone (Tekin, 1999). are almost of the same length as the outer shell. The specimen in Pl. I, fig.4 is poorly preserved and only Genus Tritortis Kozur, 1988 because of the shape of its spine, it is tentatively assigned to ?Pseudostylosphaera sp. cf. P. longispinosa. Range: Kozur (1988) discriminated two species within Tritortis: the middle Longobardian Tritortis balatonica Radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate 573

Kozur (1988), and Tritortis kretaensis (Kozur & Krahl, abdominal segments are separated from each other by 1984). The latter species was subdivided into two very deep, unperforated constrictions. subspecies: T. kretaensis kretaensis and T. kretaensis Range: Middle Anisian to early Norian (O’Dogherty et subcylindrica Kozur (1988). The morphological al., 2009). differences between these subspecies are rather gradual, but different stratigraphic ranges support their Pararuesticyrtium illyricum (Kozur & Mostler, 1981) discrimination. T. kretaensis kretaensis begins only in Pl. I, fig. 30 the late Longobardian (uppermost Ladinian), whereas T. kretaensis dispiralis begins in the upper part of the 1981. Triassocampe illyrica Kozur & Mostler, p. 98, pl. 15, middle Longobardian (Kozur & Mostler, 1996). fig. 2.

Tritortis kretaensis (Kozur & Krahl, 1984) Range: late Anisian to early Ladinian (Kozur & Mostler, Pl. I, figs 21, 22 1994).

1984. Sarla ? kretaensis Kozur & Krahl, pp. 401-403, figs 1, Genus Pseudotriassocampe sp. Kozur & Mostler, 1994 3-4. Pl. I, fig. 31 1988. Tritortis kretaensis (Kozur & Krahl) – Kozur, p. 98, pl. 4, figs 3-6, 8. Range: Middle Anisian to middle Ladinian (Kozur & Remarks: Poorly preserved specimens, rather in­ Mostler, 1994; O’Dogherty et al., 2009). complete. Two equatorial spines with vigorously twisted edges can be noticed, there was a third one at a same level, Pseudotriassocampe hungarica but it has been broken, probably during the preparation. Kozur & Mostler, 1994 Outer layer with high pore frames and large polygonal or Pl. I, fig. 32 rounded pores and nodes on the vertices (can be noticed in Pl. I, fig. 21). This arrangement and shape characterize 1994. Pseudotriassocampe hungarica Kozur & Mostler, Tritortis kretaensis, but the preservation is not good p. 137, pl. 42, figs 1, 5, 6. enough for subspecific identification. Range: Late Longobardian (late late Ladinian) (Kozur Range: Fasanian (middle Ladinian) (Kozur & Mostler, & Krahl, 1984). 1994).

Tritortis dispiralis (Bragin, 1986) Genus Annulotriassocampe sp. Kozur Pl. I, figs 24-28 in Kozur & Mostler, 1994 Pl. I, figs 33, 34 1986. Sarla dispiralis Bragin, p. 67, pl. 1, fig. 12. 1988. Tritortis kretaensis subcylindrica Kozur, pp. 98-99, Remarks: The specimen in Pl. I, Fig. 33 characterized pl. 4, figs 6, 8. by a long test with eight post-abdominal segments. 1991. Sarla dispiralis Bragin, pars.– Bragin, p. 79, pl. 4, Cephalis dome-shaped, smooth and may be poreless. fig. 11; pl. 5, fig. 8. Thorax, abdomen and rest of the segments inverse 1996. Tritortis kretaensis dispiralis (Bragin).– Kozur & Most- subtrapezoidal in outline, yet, the poor preservation of the ler, p. 91, pl. 3, fig. 11. specimen concealed the pores configuration. It resembles Remarks: One of the 3 spines is missing in the present Annulotriassocampe in its cylindrical, slightly, medially material. Originally, two spines are twisted and the third inflated test. The specimen in Pl. I, fig. 34 resembles is untwisted and somehow longer than the twisted ones. the previous form, but differs from it by having a more The distal ends are rounded, blunt or shortly pointed, conical test. with a short terminal spine. Range: Middle Anisian to middle Norian (O’Dogherty Range: Late middle Longobardian (late Ladinian) to et al., 2009). early Cordevolian (early Carnian) (Kozur & Mostler, 1996). Genus Triassocampe spp. Dumitrica, Kozur & Mostler, 1980 Order Nassellaria Ehrenberg, 1875 Pl. I, figs 36-41 Family Ruesticyrtiidae Kozur & Mostler, 1979 Genus Pararuesticyrtium sp. Kozur & Mock Remarks: The specimens recovered from our samples in Kozur & Mostler, 1981 lack an apical horn. Collar structure almost indistinct Pl. I, fig. 29 outside. Generally, the pores begin with the third segment in Triassocampe scalaris but they are barely noticed in Remarks: Cephalis small hemi-ellipsoidal, unperforated. our material due to high recrystallization. In Pl. I, figs 35, Thorax is not preserved. The abdomen and post- 40 the test is multicyrtid, consisting of 7-10 segments. 574 H. Khalil et al.

The cephalothorax is dome-shaped, smooth, almost Range: Fasanian (early Ladinian) (Kozur & Mostler, lacking pores. The abdomen is subcylindrical, smooth, 1996). without pores. Range: Middle-Upper Triassic (early Anisian to early Undetermined triassocampid Norian) (O’Dogherty et al., 2009); Middle Triassic (late Pl. I, fig. 45 Anisian to Ladinian) (Thassanapak et al., 2011), we consider this range in Tab. 1. Family Canoptidae Pessagno in Pessagno et al., 1979 Genus Multimonilis sp. Yeh, 1989 Triassocampe nishimurae Kozur & Mostler, 1996 Pl. I, fig. 46 Pl. I, fig. 42 Remarks: The specimen recovered from our samples 1994. Triassocampe nishimurai Kozur & Mostler, p. 144, pl. lack an apical horn. Collar structure almost indistinct 45, figs 4, 9-11. outside, however relicts of 5-6 postabdominal segments can be noticed. Pores are small and randomly scattered. Remak: This species should be spelled nishimurae, Range: Ladinian to middle Norian (O’Dogherty et al., since it is dedicated to Akiko Nishimura who is a woman. 2009). Range: Fasanian (early Ladinian) (Kozur & Mostler, 1996). Family Pseudodictyomitridae Pessagno, 1977 Genus Triassocingula Kozur & Mock in Kozur & Triassocampe postdeweveri Kozur & Mostler, 1994 Mostler, 1981 Pl. I, figs 43-44 Triassocingula perornatua (Blome, 1984) 1994. Triassocampe postdeweveri Kozur & Mostler, p. 144, Pl. I, fig. 35 pl. 42, figs 16, 17. 1984. Casteum perornatum Blome, p. 84, pl. 14, figs 4, 9, 12, Remarks: Cephalis small hemiellipsoidal, unperforate. 14, 18; pl. 17, fig. 14 Thorax is not preserved. Abdomen and postabdominal segments separated from each other by deep unperforated Range: Early Carnian to middle late Norian (Tekin, constrictions. 1999).

Plate I

Scanning electron microphotographs of Middle/Upper Triassic radiolarian taxa from the Excelsior Gulch conglomerate, southern Wallowa Mountains (Khalil, 2016). Figs. 1, 4-9, 13-14, 18-30, 32, 35, 38-44, 46-47: Red Gulch locality. Figs. 2, 3, 10-12, 15, 17, 31, 33-34, 36-37, 45: Excelsior Gulch type locality. Fig. 29: O’Brien locality. Figs 1-28: Scale bar a; figs 29-47: Scale bar b or scale bar c.

Fig. 1: Pylostephanidium sp.; Figs 2, 3: Pseudostylosphaera nazarovi; Figs 4-6: ?Pseudostylosphaera spp. cf. P. longispinosa; Figs 7-9: Muelleritortiinae gen. et sp. Indet.; Figs 10-19: Muelleritortis spp. ex gr. M. cochleata; Fig. 20: Muelleritortis cochleata; Figs 21-23: Tritortis kretaensis; Figs 24-28: Tritortis dispiralis; Fig. 29: Pararuesticyrtium sp. (scale bar b); Fig. 30: Pararuesticyrtium illyricum (scale bar c); Fig. 31: Pseudotriassocampe sp. (scale bar c); Fig. 32: Pseudotriassocampe hungarica (scale bar c); Figs 33, 34: Annulotriassocampe sp. (scale bar b); Fig. 35: Triassocingula perornatua (scale bar c); Figs 36-41: Triassocampe spp. (scale bar b); Fig. 42: Triassocampe nishimurae (scale bar c); Figs 43, 44: Triassocampe postdeweveri (scale bar c); Fig. 45: undeterminable triassocampid (scale bar b); Fig. 46: Multimonilis sp. (scale bar c); Fig. 47: Corum (?) delgado (scale bar c). Plate I 576 H. Khalil et al.

Genus Corum Blome, 1984 early Ladinian to early Carnian open marine succession, with a prevailing late Ladinian age. Early Ladinian Corum (?) delgado Sugiyama, 1997 radiolarian assemblages had never been found in the Pl. I, fig. 47 Blue Mountains Province so that cherts of the Excelsior Gulch conglomerate probably record a missing part of 1997. Corum (?) delgado Sugiyama, p. 151, figs 41.1-2. the sedimentary history of the Blue Mountains Province. 1997. Corum (?) delgado Sugiyama.– Tekin, 1999, p. 152, It is possible that an older part of the same reworked pl. 35, figs 1-2. ocean radiolarite sequence existed elsewhere, but has been subducted. Range: Early to middle Carnian (Tekin, 1999). Dickinson & Thayer (1978) suggested the Baker terrane as a possible source for the olistostromal basal part of the Fields Creek Formation in Izee terrane. Their 7. DISCUSSION assumption was confirmed by Blome (1984), who found cherts containing radiolarian fauna of early Carnian In the literature, radiolarian works suggested that cherts age, similar to those of the Miller Mountain melange. from the Baker terrane can be grouped into four main The olistostromes of the Field Creek Formation and the categories: Excelsior Gulch conglomerate both rework comparable (i) Radiolarian cherts from the Grindstone-Twelve­ but not identical open ocean chert clasts. Our middle mile melange (part of the Grindstone terrane). Ladinian to early Carnian assemblages also record, According to Blome et al. (1986), most cherts or partly record, the same age interval as assemblages are Early Permian to Early Triassic in age. reported from the Elkhorn Ridge Argillite (Baker Cherts samples from near Three Buttes (south terrane). However, radiolarian assemblages from all of Twelvemile Creek) yielded Early Triassic these localities are probably too different from the here- radiolarians (Wardlaw & Jones, 1980; Wardlaw et described radiolarian assemblages to draw conclusions al., 1982). concerning the source of the Wallowa terrane’s Excelsior (ii) Radiolarian cherts from Rail Cabin Argillite, Gulch conglomerate. Limited sampling and limited Vester Formation and Fields Creek Formation exposures of the Excelsior Gulch conglomerate may have (Izee terrane). Well-preserved radiolarian asso­ affected diversity and the high degree of recrystallization ciations indicate Late Triassic (late Carnian?; only rarely allowed specific identification with certainty. early to late middle Norian) and Late Triassic Nevertheless, it is also possible that the investigated chert (early Carnian; early Norian to late middle Norian) elements originated from sufficiently remote part(?s) of respectively (Blome, 1984). the ocean floor. (iii) Radiolarian cherts from the Miller Mountain melange (part of the Baker terrane). Cherts 8. CONCLUSION collected near Vance Creek indicate Middle Triassic (late Ladinian) (Dickinson & Thayer, 1978) and Radiolarian taxa recovered form chert clasts of the Middle Triassic (late Ladinian) or Late Triassic Excelsior Gulch conglomerate indicate the reworking (early Carnian) (Blome, 1984), ages. However, of early Ladinian to early Carnian radiolarites, with a later on, Blome et al. (1986) have assigned these prevailing late Ladinian age. This age partly corresponds radiolarian faunas to the early Carnian because of to the age interval of radiolarian assemblages reported the presence of Gorgansium Pessagno & Blome from the Miller Mountain melange and Elkhorn Ridge (1980). It is important to notice that this genus Argillite (Baker terrane), and the Fields Creek Formation has not been recovered from the Excelsior Gulch (Izee terrane). Additional reworking of older and/ conglomerate. Other cherts, collected near John or younger material cannot be fully excluded (index Day, indicate a Carnian to latest Norian age. radiolarians were found together with long range taxa). (iv) Radiolarian cherts from the Elkhorn Ridge Argillite The reworked chert clasts represent Panthalassan open (which composes most of the Baker terrane in its ocean sediments. The oldest recovered cherts originated eastern part). Blome et al. (1986) evidence two from deposits that have not been found elsewhere in the ages, such as cherts from the southwestern part of Blue Mountains Province. the Baker terrane are Late Triassic (Carnian to latest The deposition of the Excelsior Gulch conglomerate may Norian), whereas those in the northeastern part are represent a regional event related to the final docking of the of both Permian (Leonardian to Guadalupian) and Wallowa terrane against the Baker terrane, as previously Late Triassic age. Nevertheless, an Early Jurassic proposed (Follo, 1992; Vallier, 1995; Dickinson, age cannot be precluded. 1995; Dorsey & LaMaskin, 2007; Vallier et al., 2016). Our study of radiolarians and their ranges (Tab. 1) However, current data on radiolarian assemblages point recovered form chert clasts of the Excelsior Gulch to difficulties in correlating Excelsior’s Gulch cherts with conglomerate indicate the reworking of a substantial, those of the Baker terrane. Radiolarian assemblages from chert clasts of the Excelsior Gulch conglomerate 577

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