Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

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Palaeogeography, Palaeoclimatology, Palaeoecology

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13 Carbon isotope (δ Ccarb) stratigraphy of the Lower–Middle Ordovician (Tremadocian–Darriwilian) in the Great Basin, western United States: Implications for global correlation

Cole T. Edwards ⁎, Matthew R. Saltzman

School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory, 125 South Oval Mall, Columbus, OH 43210, USA article info abstract

13 Article history: New stable carbon isotope data (δ Ccarb)fromLower–Middle Ordovician (Tremadocian to Darriwilian) carbon- Received 7 September 2013 ate mudstone and wackestone rocks of the Pogonip Group are presented from two sections in the Great Basin Received in revised form 30 December 2013 region (USA) — Shingle Pass (east-central Nevada) and the Ibex area (western Utah). The Pogonip Group is a suc- Accepted 5 February 2014 cession of mixed carbonate and siliciclastic rocks that accumulated on a carbonate ramp under normal marine Available online 13 February 2014 conditions during the Late Cambrian (Furongian) to Middle Ordovician (Darriwilian). The Shingle Pass and Keywords: Ibex area sections have been previously studied for their conodont biostratigraphy and contain a North Carbon isotopes American Midcontinent conodont fauna that range from the Cordylodus intermedius Zone (uppermost Cambrian) 13 Ordovician to the Phragmodus polonicus Zone (Darriwilian). The δ C trend has four distinct characteristics recognized Chemostratigraphy in both Great Basin sections: 1) a drop in δ13Cfrom+1‰ at the base of the Ordovician (Tremadocian) Carbon cycling to −0.7‰,2)a1to2‰ positive δ13C shift in the uppermost Rossodus manitouensis Zone during the late Great Basin Tremadocian, 3) a gradual δ13C increase from −2‰ to ca. 0‰ during the end of the Early Ordovician (Floian), fi Great Ordovician Biodiversi cation Event and 4) a steady δ13Cdecreasefrom0‰ to −4to−5‰ during Middle Ordovician (Dapingian–Darriwilian). (GOBE) In the Lower Ordovician, δ13C trends reported here from the Great Basin are not consistent with a causal mechanism involving sea level change and the migration of isotopically distinct water bodies. Instead, these Lower Ordovician isotope data most likely reflect primary seawater chemistry and changes in δ13C on a global scale. This interpretation is supported by the excellent correlation of δ13C in the Lower Ordovician to other δ13C trends reported from the sections in the Argentine Precordillera (La Silla and San Juan formations) and in western Newfoundland (St. George and Table Head groups). These correlations using δ13C are consistent with published biostratigraphic data and provide an integrated and high-resolution chemo-biostratigraphic frame- work for the Lower Ordovician sedimentary record of the Laurentian margin. The Middle Ordovician portion of the δ13C curves in the Great Basin represented by the Kanosh and Lehman formations shows significant isotopic depletion relative to the section in Argentina. Thus, although there is some indication that minima and maxima in the Middle Ordovician curves can be correlated, the Great Basin sections show clear evidence of overprinting by local variables related to both diagenesis (dolomitization) and platform restriction. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Cramer et al., 2011; Munnecke et al., 2011; Bergström et al., 2012; Calner et al., 2012). These δ13C excursions may allow for refinement of Stable carbon isotopes (δ13C) have been widely used to better un- biostratigraphic correlations between strata that were deposited in dif- derstand changes in global carbon cycling and organic carbon burial in ferent tectonic basins. However, the use of δ13C stratigraphy for global the geologic past (e.g. Kump and Arthur, 1999). In addition, numerous correlation can be problematic during time periods such as the Lower studies have focused on positive carbon isotope excursions present to Middle Ordovician in which the magnitude of the δ13C variability is throughout Lower Paleozoic strata and their utility in global correlations relatively small (Buggisch et al., 2003; Saltzman, 2005; Bergström (Brenchley et al., 1994; Saltzman et al., 1998; Finney et al., 1999; Kump et al., 2009; Munnecke et al., 2011). The problem with the use of these et al., 1999; Saltzman et al., 2000; Bergström et al., 2006; Kaljo et al., small magnitude or high frequency changes in δ13C for correlation is 2007; Ainsaar et al., 2010; Cramer et al., 2010; Young et al., 2010; that they cannot be assumed to be worldwide events because the global carbon cycle is only one of several variables that may affect δ13Cinma- rine carbonates. Specifically, recent studies have examined whether ⁎ Corresponding author. δ13 E-mail addresses: [email protected] (C.T. Edwards), [email protected] some C excursions are a result of differential exchange of isotopically (M.R. Saltzman). distinct local water bodies or diagenetic effects overprinting the original

http://dx.doi.org/10.1016/j.palaeo.2014.02.005 0031-0182 © 2014 Elsevier B.V. All rights reserved. 2 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 signal imparted by global changes in the δ13C of the oceanic dissolved of well-preserved carbonate rocks that are more than 1 km thick and inorganic carbon (DIC) reservoir (Holmden et al., 1998; Immenhauser have been previously studied for conodont biostratigraphy (Ethington et al., 2002, 2003; Fanton and Holmden, 2007; Immenhauser et al., and Clark, 1981; Sweet and Tolbert, 1997). The Ibex area in particular 2008; Metzger and Fike, 2013). is one of the most intensively studied Lower Ordovician sections in In particular, the role of sea level change in producing local δ13C the world for its paleoecologic importance (e.g. Adrain et al., 1998; Li noise (i.e. diagenesis, mixing of water masses, or changes in carbon and Droser, 1999; Finnegan and Droser, 2005) and sequence stratigra- fluxes) that is superimposed on the global δ13C signal is widely phy (Ross et al., 1997; Miller et al., 2003, 2012) and provides a unique discussed. Immenhauser et al. (2002, 2003) interpreted a positive δ13C opportunity to directly compare δ13C and sea level. While local carbon excursion preserved in Carboniferous carbonates from northwest cycling and diagenesis significantly affected trends observed in the Spain to reflect a transgressive event that caused migration of isotopi- Middle Ordovician portion of these sections, the Lower Ordovician cally heavy open marine waters (with elevated δ13Candδ18O) into portion of the curve correlates well in timing and magnitude to other the more restricted platform environment. These authors further regions. Lower Ordovician δ13C correlations help integrate conodont argue that this relative sea level rise reduced the flux of 12C-enriched biostratigraphic data of different biogeographic realms including the carbon from oxidized organic matter and terrestrial inputs, thus Great Basin region, western Newfoundland (Azmy and Lavoie, 2009), creating a local positive δ13C excursion that can be traced in a coast- and the Argentine Precordillera (Buggisch et al., 2003; Bergström to-basin profile where the magnitude decreases from about 3‰ distally et al., 2009). In addition, Munnecke et al. (2011) report a limited to 1.5‰ in nearshore settings. In this example the change in δ13Cis Lower Ordovician data set from South China, and it is likely that more interpreted to be driven by changes in a relative sea level without any detailed correlations will be possible with the Great Basin in the future. significant changes in global carbon fluxes. A similar model of sea Ultimately, the observed global changes in δ13C observed here may have level-driven changes in δ13C has been interpreted to account for positive implications for the transitions in climate and life that took place during δ13C excursions in the epeiric sea over Laurentia during the Middle–Late the Early Ordovician (e.g. Trotter et al., 2008), but in order to address Ordovician (Holmden et al., 1998; Panchuk et al., 2005, 2006; Fanton this it will be necessary to couple these new data with other proxies and Holmden, 2007). Sea level rise introduces a cooler and nutrient- including global δ13C of organic matter, δ34S, and 87Sr/86Sr in future rich water mass onto the platform (referred to by Holmden et al. studies (e.g. Young et al., 2009; Gill et al., 2011; Saltzman et al., 2011). (1998) as an “aquafacies”) when, in conjunction with increased primary productivity and the burial of 12C-enriched organic matter, an increase 2. Geologic background in δ13C is preserved in authigenic carbonate sediments. In this model a δ13C excursion in a stratigraphic succession may simply record the 2.1. Depositional environments and sequence stratigraphy lateral movement of isotopically unique aquafacies during a sea level change. Therefore, sea level-driven δ13C excursions may offer little The depositional setting of the Great Basin region during the Early value for global correlation when considering the asynchronies of sea Ordovician is interpreted to have been a carbonate ramp with mixed level change from the combination of regional tectonic and eustatic siliciclastic and carbonate sedimentation that today comprises a effects (cf. Fanton and Holmden, 2007). 1–2 km thick succession known as the Pogonip Group (Ross et al., Metzger and Fike (2013) examined the Late Ordovician Guttenberg 1989). In the Shingle Pass section (Fig. 2) the Pogonip Group from δ13C excursion (GICE) from strata around the North American base to top is composed of the House Formation, Parker Spring Forma- midcontinent and concluded that a range of diagenetic effects and not tion, Shingle Limestone, Kanosh Shale, Lehman Formation, and Eureka migration of aquafacies has overprinted the global δ13C signal of the Quartzite (Fig. 3A). In the Ibex area (see Ross et al., 1997) the Parker GICE in some sections. Effects such as the degree of burrowing, dolomi- Spring Formation and Shingle Limestone interval is recognized as the tization, recrystallization, and hydraulic connectivity based on grain size Fillmore Formation and part of the Wah Wah Formation (Hintze, and cementation all factored in to the alteration of the primary δ13C 1951; Kellogg, 1963). The Pogonip Group is primarily composed of valuebyasmuchas2‰. These diagenetic effects, which are evident in lime mudstone and wackestone interbedded with skeletal packstone– both petrographic study and covariation between δ13Candδ18O, likely grainstone and thin-medium beds of calcareous siltstone and shale. account for differences in the shape, magnitude, and pre- and post- There are no apparent major erosional surfaces in the Shingle Pass and excursion δ13C baseline values of the GICE regionally rather than lateral Ibex areas (Hintze, 1951, 1952; Kellogg, 1963; Miller et al., 2012), but variations in isotopically distinct aquafacies (Metzger and Fike, 2013). further west in the Nopah Range (southwest Nevada) some paleokarst Despite these local variations in δ13C in the Midcontinent region during surfaces are present in the upper Antelope Valley Limestone (equivalent the GICE, this δ13C event can still be correlated regionally and globally to the Lehman Formation; Keller and Lehnert, 2010). Unfortunately the (Ludvigson et al., 2004; Young et al., 2005; Kaljo et al., 2007; Young relatively poor biostratigraphic data from the Nopah Range prevents a et al., 2008; Ainsaar et al., 2010; Bergström et al., 2010a,b). precise correlation of these paleokarst surfaces to the Shingle Pass and The clear message from all of these studies is that careful petro- Ibex sections. The carbonate rocks of the Pogonip Group are overlain graphic study and screening of δ13C and δ18O covariation (cf. Metzger by a widespread quartz arenite known as the Eureka Quartzite that and Fike, 2013) is necessary to test whether changes in δ13C may record is found throughout the Great Basin region from Utah to as far west as a global signal useful for making correlations and inferring changes in Nevada and California. global carbon fluxes (Kump and Arthur, 1999). In addition, detailed Regional mapping of facies associations near Shingle Pass and comparison between δ13C and sea level curves is necessary to evaluate the Ibex area indicates that these rocks accumulated under storm- the potential role of lateral migration of water masses with different influenced shallow, normal marine conditions on a carbonate ramp δ13C(Immenhauser et al., 2003; Fanton and Holmden, 2007). (Ross et al., 1989). Distal sponge–algal carbonate buildups and oncolitic 13 The purpose of this study is to 1) document new δ Ccarb curves from shoals formed positive relief structures (upper Shingle Limestone at Lower–Middle Ordovician carbonate rocks at Shingle Pass (South Egan Shingle Pass; Ross et al., 1989) while low-energy shales were deposited Range, NV) and the Ibex area (western UT) in the Great Basin region, in a possibly restricted nearshore lagoon (Kanosh Shale; Ross et al., USA, 2) examine local or regional sources of variability related to dia- 1989; Wilson et al., 1992; Marenco et al., 2013). Paleoenvironmental genesis and sea-level change, and 3) evaluate the global significance analyses of these platform carbonates indicate that sedimentation of these new data by comparison to δ13C from sections deposited occurred under shallow subtidal conditions near fair-weather wave along the Laurentian margin in Argentina and Newfoundland (Fig. 1; base and influenced by passing storms (Wilson et al., 1992; Finnegan Buggisch et al., 2003; Azmy and Lavoie, 2009; Thompson and Kah, and Droser, 2005) as this region was near the paleoequator during 2012). These new δ13C data in the Great Basin are from two successions the mid-Ordovician (Fig. 1) and likely in the path of tropical storms. C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 3

Australia

Siberia

North America China GB S. America Kazakhstan

NF AP Baltica

Fig. 1. Paleogeographic reconstruction of the Middle Ordovician (~470 Ma) world showing the position of Laurentia (North America) with the approximate locations of the Great Basin (GB), and the Argentine Precordillera (AP) and Newfoundland (NF) sections. Modified from Scotese and McKerrow (1991).

677000E 678000E 679000E To Hwy 318 Shingle P 4267000N assRd.

Salt Lake 00 62 City Ely 6800 Delta Reno Shingle Ibex 6949 Pass Area NEVADA UTAH

Las Vegas 85WB ARI. 4266000N CCww CAL. 6000 7200 300 km OOhh 7000 7730 85WA OOpp 0 40 00 7 78 7715 OOss 7726 OOkk 72 0

0 OOll New 8200 4265000N Section OOee

Whipple 6905 0 00 680 Approximate top of Cave 66

lower cliff member 7

6400 40

0 9000 9400 8600 85WC 9923 Shingle 4264000N Peak 500 m

Fig. 2. Location map of the Shingle Pass section in the South Egan Range, eastern Nevada. Sampled sections (blue) from Sweet and Tolbert (1997) are labeled (85WA, 85WB, and 85WC), including a new section sampled in this study measuring the Kanosh and Lehman formations. Red lines indicate formation contacts. Cw = Whipple Cave Formation, Oh = House Limestone, Op = Parker Spring Formation, Os = Shingle Limestone, Ok = Kanosh Formation, Ol = Lehman Formation, Oe = Eureka Quartzite. UTM coordinates shown from zone 11. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 4 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

A

B C

D E

F G

Fig. 3. A) Photograph of the Shingle Pass section in cross section looking NE from Highway 318 with approximate locations of formation contacts. Formation symbols same as in Fig. 2. B) Photomicrograph of micrite lithology representative of the House Fm. at Shingle Pass (sample SPH5111). This micrite contains fragmented bioclastic fragments and is massively bedded. C) Photomicrograph of a skeletal packstone in a quartz silt and carbonate mud matrix from the Wah Wah Formation in the H. minor brachiopod marker bed at Ibex (sample WW6875) showing well preserved internal skeletal microstructures of brachiopod fragments (B), echinoderm plates (E), and arthropod (likely trilobite) fragments (arrows). D) Photomicrograph of a skeletal grainstone from the Shingle Limestone in the Shingle Pass section (sample SPS5231) containing numerous algal-like fragments (possibly Nuia?) with internal radial microstruc- tures still preserved, documenting a low degree of recrystallization and alteration. E) Photomicrograph of skeletal packstone with gastropod mold filled in with spar cement and peloid (P) of carbonate mud from the Lehman Fm. at Shingle Pass (sample SPK5094). Carbonate mud within the gastropod mold and peloid shows no evidence of significant recrystallization or dolomitization. F) Photomicrograph of a spar-replaced mold filled with carbonate and clay minerals of the Lehman Formation at Ibex (sample CP6901). Mold is lined with hematite pseudomorphs of pyrite (arrows) before being filled with spar cement. G) Photomicrograph of carbonate and clay minerals of panel F showing the development of dolomite rhombs.

Carbonate production ceased when nearshore reworked quartz sand (Saltzman and Young, 2005; Keller and Lehnert, 2010; Miller et al., of the Eureka Quartzite prograded across the platform (Ross et al., 2012). 1989; McBride, 2012). The Eureka Quartzite is interpreted to reflect Miller et al. (2003, 2012) developed a sequence stratigraphic frame- the progradation of intertidal and eolian sands during a regional sea- work for the carbonate strata in the Ibex area that identified sequence level fall during the Middle Ordovician (McBride, 2012), marking a boundaries, but due to limitations on resolution these authors did not eustatic sea level low of the Sauk–Tippecanoe megasequence boundary utilize the more specific terminology traditionally used in siliciclastic C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 5 environments (parasequences, systems-tracts, maximum flooding containing graptolites, a graptolite biostratigraphic framework has surfaces, etc.). Sequence boundaries were defined on the basis of the yet to be produced that is comparable in resolution to those based on presence of sedimentary features such as siliciclastic and insoluble both trilobite and conodont data. residue content, high-energy lithologies (e.g. flat pebble conglomerates The Pogonip Group comprises the Ibexian Series and part of the and ooid-, peloid-, and oncolite-grainstones), and thin stromatolitic Whiterockian Series of North America and the Ibexian–Whiterockian and thrombolitic beds. Using some or all of these criteria, sequence Series contact approximates the global Lower to Middle Ordovician boundaries were correlated regionally and these interpretations are (Floian–Dapingian) boundary (Fig. 4; Bergström et al., 2009). This further supported by evidence of erosion or paleokarst features outside contact has been placed in the upper Shingle Limestone at Shingle of the Ibex area (e.g. North China and central Texas). Integrating the Pass where the conodont Tripodus laevis first occurs (Figs. 4 and 5; biostratigraphic framework of trilobite and conodont faunas further Sweet and Tolbert, 1997) and near lowest occurrence of the trilobite supports correlation of some of these sequence boundaries (Miller Goniotellina ensifer (Fortey and Droser, 1996). In the Ibex area the base et al., 2012). of the Whiterockian is placed at the first occurrence of T. laevis in the up- permost Wah Wah Formation, 1.2 m above the Hesperonomiella minor 2.2. Biostratigraphy brachiopod marker bed (Fig. 6; Ethington and Clark, 1981; Sweet and Tolbert, 1997). A world-class biostratigraphic framework of the Pogonip Group in the study area has been established using conodonts and trilobites 3. Methods (Hintze, 1951, 1952; Ethington and Clark, 1981; Fortey and Droser, 1996; Sweet and Tolbert, 1997; Adrain et al., 2009). A detailed study Samples were collected at 1- to 3-meter spacing along a measured by Sweet and Tolbert (1997) using graphic correlation of conodont section using a Jacob's staff. Thin sections were obtained to provide a occurrences from measured sections across the Laurentian conti- representation of lithologies and a range of diagenetic fabrics. Samples nent established a North American Midcontinent conodont fauna for δ13C analyses were micro-drilled from cut and freshly broken sur- biozonation for Lower–Middle Ordovician. However, these North faces (Tables 1 and 2). Lime mudstones (micrite) were preferentially American Midcontinent conodont biozones are stratigraphically re- collected and sampled, but in intervals where only wackestone or stricted to the midcontinent and Great Basin regions (presumably packstone lithologies were available, the micritic matrix was micro- only in warm, shallow water facies) and are not always coincident drilled. Bulk carbonate may be a suitable material to measure primary with biozones from cooler or deeper water sections with different δ13C in the absence of brachiopod calcite (e.g. Finney et al., 1999; conodont fauna (Webby et al., 2004). Due to the shallow depositional Kump et al., 1999; Saltzman et al., 2000; Maloof et al., 2005; Kaljo environment and lack of thick fine-grained siliciclastic deposits et al., 2007; Ainsaar et al., 2010; Munnecke et al., 2010, 2011).

Argentine Western Shingle Pass Ibex Area Precordillera Newfoundland NA Time Slice Stage Slice Stage Period Global Series

Table Head Group Darriwilian Whiterockian Middle Ordovician Dapingian Floian Ibexian St. George Group Lower Ordovician Tremadocian

Watts Bight Camb.

Fig. 4. Biostratigraphic and lithostratigraphic correlations of conodont zones and formations from Shingle Pass, Ibex area, the Argentine Precordillera, and western Newfoundland. Conodont zone abbreviations A = C. angulatus,I=Iapetognathus,L=C. lindstromi. Formation abbreviation WR = Watson Ranch Quartzite. Camb. = Cambrian, NA = North American. Conodont zones are based on occurrence data from Ethington and Clark (1981), Sweet and Tolbert (1997), Lehnert (1995a,b), Albanesi et al. (1998, 2013), Keller (1999), Ji and Barnes (1994),andStouge (1984). Lithostratigraphy from Kellogg (1963), Hintze (1951, 1973), Buggisch et al. (2003) and Azmy and Lavoie (2009), stage slice data modified from Bergström et al. (2009),andtimeslicedatamodified from Webby et al. (2004). 6 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

Global NA NA Conodont Litho- Period Stage Series Stage Zone stratigraphy δ13C ‰ δ18 Eureka carb O ‰ Quartzite -5 -4 -3 -2 -1 0 1 2 -16 -12 -8 -4 0

Phragmodus polonicus Lehman Histiodella Darriwilian holodentata

Histiodella Kanosh New Section Whiterockian sinuosa Shale

Histiodella Middle Ordovician altifrons Not formally established Tripodus laevis Dapingian

Reutterodus Shingle 85WC andinus Black-

hillsian Limestone

Floian Oepikodus communis

Diaphorodus Tulean deltatus/ Oneotodus Sandstone

costatus 85WB Shale Parker Macerodus Spring Limestone

Ibexian dianae Dolomite Low Diversity Chertylimestone Stairsian

Lower Ordovician Interval 200 m Siltylimestone Tremadocian Rossodus manitouensis House

85WA Poorlyexposed Limestone A I L C. intermedius

Cordylodus Whipple -5 -4 -3 -2 -1 0 1 2 -16 -12 -8 -4 0 proavus Cave δ13 18 Skullrockian Ccarb ‰ δ O ‰ Camb.

Fig. 5. Lithology, biostratigraphic zones, and δ13C and δ18O data from the Shingle Pass section with stratigraphic coverage from each of the measured sections shown in Fig. 2. Black lines represent a three-point moving average of the δ13Candδ18O data. Moving averages were calculated by taking the average of each isotope value and the overlying and underlying values. Stars indicate thin section locations and filled stars are thin sections shown in Fig. 3. Conodont zones A = C. angulatus,I=Iapetognathus,L=C. lindstromi,C.=Cordylodus, Camb. = Cambrian. Lithostratigraphy from Kellogg (1963) and conodont biozones from Sweet and Tolbert (1997).

δ13C values were measured at four different laboratories over the appreciable evidence for surficial micritization or secondary recrystal- course of this study. These data were measured on a Kiel Carbonate lization. Microstructural details like an internal radial fabric and Device III attached to a Thermo-Finnigan MAT 253 Dual Inlet System neomorphic recrystallization of ooids are still preserved in wackestones mass-spectrometer (University of Kansas), a Kiel Carbonate Device III and packstones of the Wah Wah and Lehman formations, and a similar attached to a Finnigan Delta Plus IV mass-spectrometer (Ohio State internal radial fabric is preserved in the constituents of an algal-like University), a Gas Bench II attached to a Thermo-Finnigan Delta Plus grainstone (Nuia(?); cf. Toomey and Klement, 1966) in the lower XP mass-spectrometer (Indiana University), and an Isoprime 100 mass Shingle Formation (Fig. 3D). There is no petrographic evidence of spectrometer configured for continuous flow measurement coupled broken skeletal fragments at grain contacts. Dolomitization is mostly with a Multiflow headspace sampling device (Virginia Polytechnical confined to the uppermost 50 m of the Lehman Formation at Shingle Institute). Replicate samples produced consistent values showing no Pass and in the Ibex area where dolomite crystal growth is present in measureable laboratory bias. lime mudstone and argillaceous internal molds of bioclastic fragments Powders for δ13C analyses were first weighed and roasted in a (Fig. 3FandG). vacuum oven at 100 °C for at least 8 h to remove water and volatile or- ganic contaminants. Between 0.1 and 0.5 mg of carbonate were reacted 4.2. Isotope trends at 72 °C with 3–5 drops of anhydrous phosphoric acid for 4 min on the Kiel devices, and at least 2 h (usually overnight) on the Gas Bench II The δ13C data reported by Saltzman (2005) from the Shingle and Multiflow devices. Isotope ratios were corrected for acid fraction- Pass section (Table 1), following the section originally sampled for ation and 17O contribution and reported in per mil notation relative conodonts by Sweet and Tolbert (1997), has been expanded in this to the Vienna Pee Dee Belemnite (V-PDB) standard (Craig, 1957). study with higher sample resolution in some intervals (House Forma- Precision and calibration of data were monitored through routine tion and Shingle Limestone), as well as extended into previously analysis of the IAEA NBS-18 and NBS-19 standards and internal labora- unmeasured rocks of the Kanosh and Lehman formations in a new tory standards. Standard deviations for δ13C and δ18O are 0.05‰ and section (Fig. 2). δ13C measured from the Ibex area are new data 0.10‰, respectively (one sigma). following the sections described by Ross et al. (1997). During the latest Cambrian, δ13C values decrease sharply from values of ca. +1‰ in the 4. Results Cordylodus intermedius Zone to −0.7‰ in the Rossodus manitouensis Zone (Tremadocian). There is a distinct and short-lived positive δ13C 4.1. Thin section analysis shift at the top of the R. manitouensis Zone where δ13C values rise to +1‰ before falling back to pre-shift values in the Low Diversity Lithologies range from sparsely fossiliferous micrite (b2% bioclasts) Interval Zone (Fig. 4). δ13C values steadily increase from a low of with minor amounts of recrystallization to highly fossiliferous skeletal −2‰ in the Macerodus dianae Zone until the Reutterodus andinus packstones with some micritic matrix and spar-filled pores (Fig. 3C–E). Zone where δ13Creachesamaximumofca.0‰ at the end of the Floian, Where present, brachiopod fragments preserve primary detailed which also represents the end of the Ibexian Series and beginning of the fibrous and prismatic shell microstructure (Fig. 3C) and contain no Whiterockian Series in North America (Fig. 4). A similar δ13C trend for Global NA NA Conodont Trilobite Litho- Period Stage Series Stage Zone Zone stratigraphy 13 Relative Sequence δ C ‰ 18 Watson carb δ O‰ Sea Level Ranch -6 -5 -4 -3 -2 -1 0 12-10 -8 -6 -4 Rise Fall Quartzite Histiodella Tippe. holodentata Lehman Long- N term 1 (2014) 399 Palaeoecology Palaeoclimatology, Palaeogeography, / Saltzman M.R. Edwards, C.T. Histiodella trend Camp Section Darriwilian sinuosa Kanosh Histiodella Shale altifrons M Whiterockian Middle Ord. Tripodus Juab Dapingian laevis L

JSection H.minor K Wah wah markerbed Reutterodus J andinus I F-4

Oepikodus H Sauk H section Blackhillsian communis IV Floian F-3 Diaphorodus G2

deltatus/ Fillmore G Section Oneotodus

Tulean costatus

G1 F-2 Macerodus

Ibexian F dianae Sandstone Shale

Lower Ordovician E Low Diversity CSection F-1 Interval Limestone D Dolomite Rossodus

C BSec. 200 m Cherty limestone Tremadocian manitouensis S a u k House Cordylodus Silty limestone angulatus B Limestone III I L Covered C. intermedius Section Lava Dam Cordylodus A Notch Peak proavus – -6 -5 -4 -3 -2 -1 0 1 2 -10 -8 -6 -4 20

Skullrockian Stairsian δ13 δ18 Camb. Ccarb ‰ O ‰

Fig. 6. Lithology, biostratigraphic zones, and δ13 Candδ18O data from the Ibex section with the stratigraphic coverage from each of the measured sections from Hintze (1973). Black lines represent a three-point moving average of the δ13 Candδ18 O data. Stars indicate thin section locations and filled stars are thin sections shown in Fig. 3. Tippe. = Tippecanoe. Conodont zones I = Iapetognathus,L=C. lindstromi,C.=Cordylodus, Camb. = Cambrian, Ord. = Ordovician. Lithostratigraphy and trilobite zones from Hintze (1973;seealsoRoss et al., 1997) and conodont biozones from Ethington and Clark (1981). Relative sea level curve, flooding events (F-1 to F-4), and megasquence boundaries modified from Miller et al. (2012). 7 8 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

Table 1 δ13Candδ18O data from the Shingle Pass section. FPG = Flat pebble conglomerate. Sample IDs beginning with SPW- are from Saltzman (2005). Ages for Ordovician conodont Zones are from Cooper and Sadler (2012), but ages (*) from Cambrian-aged Zones are approximated.

Sample ID Cumulative meters Lithology Conodont zone Formation δ13C δ18OAge (Ma)

SPH5104 −1.0 Dolomite C. intermedius Whipple Cave 0.77 −10.45 486.55* SPH5105 0.0 Micrite C. intermedius House 1.30 −9.66 486.50* SPW-0 0.0 Micrite C. intermedius House 1.40 −11.50 486.50* SPH5106 3.0 Micrite C. intermedius House 1.48 −10.58 486.38* SPH5107 6.0 Recrystallized micrite C. intermedius House 1.03 −11.83 486.25* SPW-23 7.0 Micrite C. intermedius House 1.17 −9.96 486.21* SPH5108 9.0 Recrystallized micrite C. intermedius House 1.02 −10.87 486.13* SPH5109 12.0 Recrystallized micrite C. lindstromi House 0.86 −9.37 486.00* SPW-40 12.2 Recrystallized micrite C. lindstromi House 0.89 −11.66 485.99* SPH5111 18.0 Micrite C. lindstromi House 0.77 −9.56 485.79* SPW-60 18.3 Micrite C. lindstromi House 0.85 −9.10 485.78* SPH5113 24.0 Micrite C. lindstromi House 0.70 −12.36 485.58* SPW-82 25.0 Not available C. lindstromi House 0.85 −9.53 485.55* SPH5114 27.0 Micrite C. lindstromi House 0.17 −11.04 485.48* SPH5115 30.0 Recrystallized micrite Iapetognathus House −0.36 −10.45 485.37 SPW-99 30.2 Micrite Iapetognathus House −1.20 −10.18 485.31 SPH5117 36.0 Recrystallized micrite C. angulatus House −0.24 −11.45 481.28 SPW-120 36.6 Micrite C. angulatus House −0.66 −9.59 480.70 SPH5119 42.0 Micrite R. manitouensis House −0.53 −10.80 480.27 SPH5120 45.0 Recrystallized micrite R. manitouensis House −0.72 −9.53 480.27 SPH5121 48.0 Recrystallized micrite R. manitouensis House −0.65 −10.12 480.26 SPW-159 48.5 Recrystallized micrite R. manitouensis House −0.68 −10.26 480.26 SPH5123 54.0 Micrite R. manitouensis House −0.75 −10.34 480.26 SPW-180 54.9 Micrite R. manitouensis House −0.64 −8.91 480.26 SPH5125 60.0 Recrystallized micrite R. manitouensis House −0.49 −10.51 480.25 SPW-200 61.0 Micrite R. manitouensis House −0.64 −10.45 480.25 SPH5126 63.0 Recrystallized micrite R. manitouensis House −0.80 −9.49 480.25 SPH5127 66.0 Recrystallized micrite R. manitouensis House −0.64 −10.25 480.25 SPW-220 67.1 Micrite R. manitouensis House −0.31 −12.60 480.24 SPH5128 67.5 Micrite R. manitouensis House −0.69 −10.18 480.24 SPH5129 69.0 Recrystallized micrite R. manitouensis House −0.97 −10.22 480.24 SPH5131 72.0 Recrystallized micrite R. manitouensis House −0.79 −9.24 480.24 SPW-240 73.2 Argillaceous micrite R. manitouensis House −0.73 −9.96 480.24 SPH5132 73.5 Recrystallized micrite R. manitouensis House −0.85 −9.97 480.24 SPH5133 75.0 Recrystallized micrite R. manitouensis House −0.38 −8.40 480.24 SPH5135 78.0 Micrite R. manitouensis House −0.73 −9.19 480.23 SPW-263 80.2 Micrite R. manitouensis House −0.33 −9.66 480.23 SPH5137 81.0 Micrite R. manitouensis House −0.46 −9.38 480.23 SPH5139 84.0 Recrystallized micrite R. manitouensis House −0.47 −10.44 480.23 SPW-280 85.3 Argillaceous micrite R. manitouensis House −0.60 −10.20 480.23 SPH5142 88.5 Argillaceous micrite R. manitouensis House −0.66 −10.19 480.22 SPH5143 90.0 Recrystallized micrite R. manitouensis House −0.57 −9.92 480.22 SPW-300 91.4 Wackestone R. manitouensis House −0.40 −8.45 480.22 SPH5146 94.5 Argillaceous micrite R. manitouensis House −0.58 −9.26 480.22 SPH5147 96.0 Recrystallized micrite R. manitouensis House −1.08 −10.88 480.22 SPW-320 97.5 Wackestone R. manitouensis House −0.53 −13.26 480.21 SPH5149 99.0 Micrite R. manitouensis House −0.60 −11.56 480.21 SPH5150 100.5 Argillaceous micrite R. manitouensis House −0.55 −17.05 480.21 SPW-342 104.2 Micrite R. manitouensis House −0.91 −9.98 480.21 SPH5153 105.0 Micrite R. manitouensis House −0.64 −10.27 480.21 SPH5155 107.5 Recrystallized micrite R. manitouensis House −0.35 −11.49 480.20 SPH5156 109.5 Argillaceous micrite R. manitouensis House −0.43 −10.47 480.20 SPW-360 109.7 Recrystallized micrite R. manitouensis House −0.94 −9.35 480.20 SPH5160 115.0 Recrystallized wackestone R. manitouensis House −1.02 −9.04 480.20 SPW-379 115.5 Wackestone R. manitouensis House −0.76 −10.81 480.20 SPH5162 118.5 Recrystallized micrite R. manitouensis House −0.43 −10.25 480.19 SPH5164 121.5 Recrystallized wackestone R. manitouensis House 0.04 −8.86 480.19 SPW-401 122.2 Micrite R. manitouensis House 0.11 −9.70 480.19 SPH5167 126.0 Argillaceous micrite R. manitouensis House 0.53 −9.32 480.19 SPW-420 128.0 Wackestone R. manitouensis House 0.70 −8.59 480.18 SPH5169 129.0 Micrite R. manitouensis House 0.47 −10.14 480.18 SPH5171 132.0 Recrystallized wackestone R. manitouensis House −0.17 −10.51 480.18 SPW-435 132.6 Wackestone R. manitouensis House 0.15 −8.91 480.18 SPH5174 136.5 Recrystallized micrite R. manitouensis House −0.51 −8.71 480.17 SPW-455 138.7 Packstone R. manitouensis House −0.48 −8.98 480.17 SPH5176 139.5 Recrystallized micrite R. manitouensis Parker Spring −0.59 −9.38 480.17 SPH5177 141.0 Argillaceous micrite Low Diversity Interval Parker Spring −0.68 −10.14 480.17 SPH5178 142.5 Argillaceous micrite Low Diversity Interval Parker Spring −0.32 −9.85 480.17 SPW-480 146.3 Micrite Low Diversity Interval Parker Spring −0.99 −15.69 480.16 SPH5181 147.0 Micrite Low Diversity Interval Parker Spring −0.86 −9.37 480.16 SPH5184 151.5 Recrystallized micrite Low Diversity Interval Parker Spring −1.06 −9.52 480.15 SPW-501 152.7 Micrite Low Diversity Interval Parker Spring −1.26 −10.26 480.15 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 9

Table 1 (continued) Sample ID Cumulative meters Lithology Conodont zone Formation δ13C δ18OAge (Ma)

SPH5187 156.0 Micrite Low Diversity Interval Parker Spring −1.23 −8.74 480.14 SPW-518 157.9 Wackestone Low Diversity Interval Parker Spring −1.22 −9.27 480.14 SPH5190 160.5 Micrite Low Diversity Interval Parker Spring −1.53 −9.62 480.14 SPW-538 164.0 Micrite Low Diversity Interval Parker Spring −1.50 −10.75 480.13 SPH5193 165.0 Micrite Low Diversity Interval Parker Spring −1.53 −9.63 480.13 SPH5195 168.0 Micrite Low Diversity Interval Parker Spring −1.22 −11.66 480.12 SPH5196 169.5 Micrite Low Diversity Interval Parker Spring −1.42 −11.51 480.12 SPH5197 171.0 Micrite Low Diversity Interval Parker Spring −0.89 −12.96 480.12 SPW-573 174.7 Micrite Low Diversity Interval Parker Spring −1.22 −9.12 480.11 SPH5200 175.5 Argillaceous micrite Low Diversity Interval Parker Spring −1.35 −9.38 480.11 SPH5204 181.5 Argillaceous micrite Low Diversity Interval Parker Spring −1.32 −12.14 480.10 SPH5206 184.5 Argillaceous micrite Low Diversity Interval Parker Spring −1.23 −10.61 480.10 SPH5207 186.0 Argillaceous micrite Low Diversity Interval Parker Spring −1.14 −9.72 480.09 SPW-630 192.0 Not available Low Diversity Interval Parker Spring −1.32 −9.31 480.08 SPW-640 195.1 Recrystallized micrite Low Diversity Interval Parker Spring −1.03 −9.12 480.08 SPW-683 208.2 Recrystallized micrite M. dianae Parker Spring −1.13 −10.87 480.06 SPW-712 217.0 Wackestone M. dianae Parker Spring −1.25 −9.27 480.05 SPW-739 225.2 Micrite M. dianae Parker Spring −1.26 −9.32 480.04 SPW-751 228.9 Wackestone M. dianae Parker Spring − 0.73 −9.44 480.03 SPW-799 243.5 Micrite M. dianae Parker Spring −0.29 −8.67 480.01 SPW-836 254.8 Wackestone M. dianae Parker Spring −0.94 −9.52 480.00 SPW-868 264.6 Micrite M. dianae Parker Spring −1.51 −9.31 479.99 SPW-906 276.1 Packstone M. dianae Parker Spring −1.88 −8.22 479.97 SPW-921 280.7 Wackestone M. dianae Parker Spring −2.79 −8.35 479.97 SPW-941 286.8 Micrite in FPG M. dianae Parker Spring −1.03 −8.66 479.96 SPW-968 295.0 Wackestone M. dianae Parker Spring −0.79 −9.33 479.95 SPW-991 302.1 Micrite A. deltatus/O. costatus Parker Spring −1.31 −8.73 479.94 SPW-1012 308.5 Micrite in FPG A. deltatus/O. costatus Parker Spring −1.76 −8.90 479.85 SPW-1022 311.5 Micrite A. deltatus/O. costatus Parker Spring −1.68 −8.65 479.81 SPW-1042 317.6 Micrite A. deltatus/O. costatus Parker Spring −2.04 −9.48 479.72 SPW-1103 336.2 Micrite A. deltatus/O. costatus Parker Spring −1.35 −8.99 479.45 SPW-1126 343.2 Micrite A. deltatus/O. costatus Parker Spring −1.09 −9.20 479.35 SPW-1175 358.1 Argillaceous micrite A. deltatus/O. costatus Parker Spring −1.71 −8.66 479.13 SPW-1200 365.8 Micrite A. deltatus/O. costatus Parker Spring −1.98 −8.87 479.02 SPW-1217 370.9 Micrite A. deltatus/O. costatus Parker Spring −1.55 −8.22 478.94 SPW-1253 381.9 Recrystallized micrite A. deltatus/O. costatus Parker Spring −1.67 −8.61 478.79 SPW-1277 389.2 Micrite A. deltatus/O. costatus Parker Spring −1.34 −8.86 478.68 SPW-1306 398.1 Wackestone A. deltatus/O. costatus Parker Spring −1.44 −8.75 478.55 SPW-1326 404.2 Wackestone A. deltatus/O. costatus Shingle −1.45 −9.06 478.46 SPW-1343 409.3 Micrite A. deltatus/O. costatus Shingle −1.32 −8.94 478.39 SPW-1361 414.8 Micrite A. deltatus/O. costatus Shingle −1.44 −8.45 478.31 SPW-1385 422.1 Micrite A. deltatus/O. costatus Shingle −1.35 −8.48 478.20 SPW-1402 427.3 Micrite A. deltatus/O. costatus Shingle −1.01 −8.50 478.13 SPW-1432 436.5 Micrite A. deltatus/O. costatus Shingle −1.17 −8.73 478.00 SPW-1467 447.1 Micrite A. deltatus/O. costatus Shingle −1.14 −8.59 477.84 SPW-1483 452.0 Micrite A. deltatus/O. costatus Shingle −1.55 −9.42 477.77 SPW-1503 458.1 Micrite A. deltatus/O. costatus Shingle −1.53 −8.25 477.68 SPW-1503 458.1 Micrite A. deltatus/O. costatus Shingle −1.57 −8.31 477.68 SPS-7591 459.5 Micrite A. deltatus/O. costatus Shingle −1.54 −8.40 477.66 SPW-1521 463.6 Argillaceous micrite A. deltatus/O. costatus Shingle −1.26 −8.63 477.60 SPW-1540 469.4 Recrystallized micrite A. deltatus/O. costatus Shingle −1.16 −8.40 477.52 SPW-1559 475.2 Not available O. communis Shingle −1.38 −8.91 477.32 SPW-1580 481.6 Micrite O. communis Shingle −0.98 −8.40 477.08 SPS-7593 483.5 Argillaceous micrite O. communis Shingle −1.22 −8.22 477.00 SPW-1602 488.3 Micrite O. communis Shingle −1.33 −9.08 476.82 SPS5208 493.0 Argillaceous wackestone O. communis Shingle −0.99 −8.65 476.65 SPW-1621 494.1 Wackestone O. communis Shingle −1.07 −8.54 476.61 SPS5210 494.5 Argillaceous micrite O. communis Shingle −1.56 −9.36 476.59 SPW-1640 499.9 Micrite O. communis Shingle −0.98 −8.72 476.39 SPS5214 500.5 Micrite O. communis Shingle −1.02 −9.04 476.37 SPS5216 503.5 Micrite O. communis Shingle −1.20 −9.09 476.25 SPW-1661 506.3 Not available O. communis Shingle −0.90 −8.65 476.15 SPS5218 506.6 Micrite O. communis Shingle −1.04 −7.92 476.08 SPS5220 509.5 Recrystallized micrite O. communis Shingle −0.69 −9.16 475.97 SPW-1680 512.1 Micrite O. communis Shingle −1.06 −8.53 475.93 SPS5222 512.5 Micrite O. communis Shingle −0.74 −8.66 475.86 SPS5224 515.5 Micrite O. communis Shingle −0.97 −8.59 475.75 SPW-1700 518.2 Micrite O. communis Shingle −1.00 −8.35 475.70 SPS5226 518.5 Micrite O. communis Shingle −0.94 −8.86 475.63 SPS5228 521.5 Micrite O. communis Shingle −1.02 −8.64 475.52 SPS5230 524.5 Micrite O. communis Shingle −1.16 −10.50 475.41 SPW-1721 524.6 Recrystallized wackestone O. communis Shingle −0.94 −8.43 475.46 SPS5232 527.5 Micrite O. communis Shingle −0.96 −8.54 475.30 SPW-1740 530.4 Argillaceous micrite O. communis Shingle −1.23 −8.59 475.25 SPS5234 530.5 Micrite O. communis Shingle −1.01 −8.48 475.18

(continued on next page) 10 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

Table 1 (continued) Sample ID Cumulative meters Lithology Conodont zone Formation δ13C δ18OAge (Ma)

SPS5236 533.5 Micrite O. communis Shingle −0.92 −8.50 475.07 SPW-1760 536.4 Micrite O. communis Shingle −1.04 −8.27 475.02 SPS5238 536.5 Micrite O. communis Shingle −1.15 −8.73 474.96 SPS5240 539.5 Argillaceous micrite O. communis Shingle −0.96 −8.39 474.85 SPS5242 542.5 Recrystallized micrite O. communis Shingle −0.83 −8.09 474.73 SPS5244 545.5 Micrite O. communis Shingle −1.13 −8.69 474.62 SPS5246 548.5 Recrystallized micrite O. communis Shingle −1.00 −9.99 474.51 SPW-1800 548.6 Recrystallized micrite O. communis Shingle −0.94 −8.98 474.56 SPS5248 551.5 Recrystallized micrite O. communis Shingle −0.97 −7.71 474.40 SPS5250 554.5 Recrystallized micrite O. communis Shingle −0.79 −7.93 474.28 SPW-1820 554.7 Argillaceous micrite O. communis Shingle −0.95 −8.34 474.33 SPW-1840 560.8 Micrite O. communis Shingle −0.88 −7.98 474.10 SPW-1860 566.9 Packstone O. communis Shingle −1.05 −7.96 473.87 SPW-1874 571.2 Micrite R. andinus Shingle −0.79 −8.35 473.77 SPW-1896 577.9 Packstone R. andinus Shingle −1.04 −8.06 473.64 SPW-1912 582.8 Micrite R. andinus Shingle −0.91 −8.82 473.54 SPS-7595 589.5 Micrite R. andinus Shingle −0.88 −8.46 473.40 SPW-1940 591.3 Wackestone R. andinus Shingle −1.50 −8.87 473.37 SPW-1957 596.5 Packstone R. andinus Shingle −1.70 −8.48 473.26 SPW-1980 603.5 Micrite R. andinus Shingle −1.76 −11.24 473.12 SPW-2000 609.6 Wackestone R. andinus Shingle −1.05 −8.10 473.00 SPW-2020 615.7 Micrite R. andinus Shingle −0.43 −8.44 472.88 SPS-7598 619.5 Argillaceous wackestone R. andinus Shingle −1.55 −8.23 472.80 SPS-7601 651.0 Argillaceous micrite R. andinus Shingle −1.34 −8.27 472.17 SPW-2173 662.3 Wackestone R. andinus Shingle −1.06 −8.48 471.94 SPW-2198 670.0 Micrite R. andinus Shingle −0.81 −7.78 471.79 SPW-2220 676.7 Micrite R. andinus Shingle −0.73 −8.24 471.65 SPW-2238 682.1 Micrite R. andinus Shingle −1.36 −8.57 471.54 SPW-2260 688.8 Micrite R. andinus Shingle −0.85 −8.40 471.41 SPW-2278 694.3 Recrystallized wackestone R. andinus Shingle −0.53 −7.59 471.30 SPW-2298 700.4 Wackestone R. andinus Shingle −0.55 −7.88 471.17 SPW-2316 705.9 Recrystallized wackestone R. andinus Shingle −0.54 −7.54 471.06 SPW-2333 711.1 Micrite R. andinus Shingle −0.16 −8.12 470.96 SPW-2360 719.3 Micrite R. andinus Shingle −0.27 −8.15 470.79 SPW-2380 725.4 Packstone R. andinus Shingle −0.57 −7.64 470.67 SPW-2404 732.7 Wackestone R. andinus Shingle −1.04 −8.01 470.53 SPW-2420 737.6 Wackestone R. andinus Shingle −0.64 −7.72 470.43 SPW-2440 743.7 Micrite T. laevis Shingle −0.64 −7.97 470.30 SPW-2460 749.8 Micrite T. laevis Shingle −0.23 −8.12 470.17 SPW-2480 755.9 Wackestone T. laevis Shingle −0.55 −8.03 470.04 SPW-2500 762.0 Micrite T. laevis Shingle −0.46 −7.86 469.91 SPW-2520 768.1 Micrite T. laevis Shingle −0.65 −7.92 469.78 SPW-2620 798.6 Not available T. laevis Shingle −1.06 −8.32 469.12 SPW-2638 804.1 Not available T. laevis Shingle −0.99 −7.68 469.01 SPW-2653 808.6 Wackestone T. laevis Shingle −0.94 −7.75 468.91 SPW-2848 868.1 Argillaceous micrite H. altifrons Shingle −1.81 −7.49 467.73 SPK4980 872.0 Argillaceous micrite H. altifrons Shingle −1.17 −8.70 467.66 SPW-2873 875.7 Wackestone H. altifrons Kanosh −1.73 −7.78 467.59 SPK4982 878.0 Micrite H. altifrons Kanosh −1.42 −9.01 467.54 SPW-2893 881.8 Micrite H. altifrons Kanosh −1.86 −8.11 467.47 SPK4986 890.0 Micrite H. sinuosa Kanosh −1.23 −7.44 467.40 SPW-2924 891.2 Wackestone H. sinuosa Kanosh −1.57 −8.28 467.40 SPK7608 910.0 Argillaceous micrite H. sinuosa Kanosh −1.46 −8.45 467.26 SPK4999 929.0 Argillaceous micrite H. sinuosa Kanosh −1.53 −8.19 467.13 SPK5001 935.0 Wackestone H. sinuosa Kanosh −2.06 −8.35 467.08 SPK5003 941.0 Argillaceous wackestone H. sinuosa Kanosh −1.73 −8.25 467.04 SPK5005 947.0 Argillaceous wackestone H. sinuosa Kanosh −1.76 −8.21 467.00 SPK5007 953.0 Argillaceous wackestone H. sinuosa Kanosh −2.25 −9.31 466.95 SPK5009 959.0 Wackestone H. sinuosa Kanosh −2.13 −8.88 466.91 SPK5011 965.0 Argillaceous wackestone H. sinuosa Kanosh −1.68 −13.36 466.87 SPK5013 971.0 Argillaceous micrite H. sinuosa Kanosh −1.75 −8.17 466.83 SPK5015 977.0 Recrystallized wackestone H. sinuosa Kanosh −2.06 −8.21 466.78 SPK5019 989.0 Argillaceous micrite H. sinuosa Kanosh −2.40 −8.66 466.70 SPK7609 998.0 Packstone H. sinuosa Kanosh −3.86 −8.45 466.63 SPK5036 1040.0 Micrite H. holodentata Lehman −2.36 −8.05 466.29 SPK5037 1043.0 Micrite H. holodentata Lehman −2.14 −8.32 466.24 SPK5038 1046.0 Micrite H. holodentata Lehman −1.61 −9.00 466.20 SPK5041 1055.0 Recrystallized micrite H. holodentata Lehman −2.90 −10.13 466.06 SPK5043 1061.0 Argillaceous micrite H. holodentata Lehman −1.87 −9.41 465.97 SPK5044 1064.0 Argillaceous micrite H. holodentata Lehman −2.17 −9.48 465.93 SPK5047 1074.5 Argillaceous micrite H. holodentata Lehman −4.01 −8.07 465.77 SPK5050 1082.0 Recrystallized micrite H. holodentata Lehman −2.61 −7.75 465.66 SPK5051 1085.0 Micrite H. holodentata Lehman −2.39 −7.26 465.61 SPK5052 1088.0 Micrite H. holodentata Lehman −4.77 −7.78 465.57 SPK5053 1091.0 Micrite H. holodentata Lehman −4.71 −7.88 465.52 SPK5055 1097.0 Argillaceous wackestone H. holodentata Lehman −2.00 −6.03 465.43 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 11

Table 1 (continued) Sample ID Cumulative meters Lithology Conodont zone Formation δ13C δ18OAge (Ma)

SPK5057 1103.0 Micrite H. holodentata Lehman −2.89 −7.90 465.34 SPK5060 1112.0 Micrite H. holodentata Lehman −3.22 −7.95 465.21 SPK5061 1115.0 Micrite H. holodentata Lehman −2.78 −7.22 465.16 SPK5062 1118.0 Micrite H. holodentata Lehman −2.05 −7.79 465.12 SPK5063 1121.0 Micrite H. holodentata Lehman −3.23 −7.22 465.07 SPK5064 1124.0 Micrite H. holodentata Lehman −1.80 −7.18 465.03 SPK5066 1130.0 Argillaceous wackestone H. holodentata Lehman −2.36 −8.39 464.94 SPK5068 1136.0 Recrystallized wackestone H. holodentata Lehman −3.62 −7.75 464.85 SPK5069 1139.0 Micrite H. holodentata Lehman −3.98 −8.04 464.80 SPK5071 1145.0 Argillaceous wackestone H. holodentata Lehman −2.51 −7.65 464.71 SPK5072 1148.0 Micrite H. holodentata Lehman −2.64 −8.01 464.67 SPK5073 1151.0 Argillaceous micrite H. holodentata Lehman −1.65 −6.59 464.62 SPK5074 1154.0 Micrite H. holodentata Lehman −3.84 −7.06 464.58 SPK5075 1157.0 Wackestone H. holodentata Lehman −4.74 −7.44 464.53 SPK5077 1163.0 Argillaceous micrite H. holodentata Lehman −2.63 −6.33 464.44 SPK5078 1166.0 Micrite H. holodentata Lehman −2.64 −7.19 464.40 SPK5079 1169.0 Micrite H. holodentata Lehman −2.44 −7.07 464.35 SPK5080 1172.0 Micrite H. holodentata Lehman −4.28 −7.30 464.31 SPK5081 1175.0 Argillaceous micrite H. holodentata Lehman −0.93 −6.66 464.26 SPK5082 1178.0 Wackestone H. holodentata Lehman −1.61 −5.59 464.22 SPK5083 1181.0 Micrite H. holodentata Lehman −2.91 −6.83 464.17 SPK5084 1184.0 Argillaceous micrite H. holodentata Lehman −2.35 −5.34 464.13 SPK5085 1187.0 Argillaceous micrite H. holodentata Lehman −2.93 −6.99 464.08 SPK5087 1193.0 Argillaceous micrite H. holodentata Lehman −2.15 −6.49 463.99 SPK5088 1196.0 Micrite H. holodentata Lehman −2.20 −6.66 463.95 SPK5089 1199.0 Micrite H. holodentata Lehman −2.99 −6.44 463.90 SPK5090 1202.0 Recrystallized micrite H. holodentata Lehman −2.96 −6.77 463.86 SPK5092 1208.0 Micrite P. polonicus Lehman −1.81 −6.38 463.77 SPK5093 1211.0 Argillaceous micrite P. polonicus Lehman −1.30 −6.54 463.72 SPK5094 1214.0 Packstone P. polonicus Lehman −2.92 −6.31 463.68 SPK5095 1217.0 Micrite P. polonicus Lehman −2.19 −6.86 463.63 SPK5096 1220.0 Packstone P. polonicus Lehman −2.22 −7.25 463.59 SPK5098 1226.0 Dolomite P. polonicus Lehman −2.25 −4.44 463.50 SPK5099 1229.0 Argillaceous micrite P. polonicus Lehman −1.24 −1.46 463.45 SPK5100 1232.0 Micrite P. polonicus Lehman −1.83 −3.09 463.41 SPK5101 1235.0 Dolomite P. polonicus Lehman −1.38 −4.72 463.36 SPK5102 1238.0 Micrite P. polonicus Lehman −1.57 −4.15 463.32 SPK5103 1241.0 Dolomite P. polonicus Lehman −1.89 −5.32 463.27

the Ibexian Series appears to be reported by Ripperdan and Miller level curves. Finally, a discussion is presented concerning which aspects (1995, 2013) and Miller et al. (2006) with δ13C values decreasing of the δ13C trends appear to represent global carbon cycling, and may below 0‰ at the beginning of the Ibexian, a brief 3‰ positive excursion therefore aid in refinement of global correlations currently based on at the base of the Stairsian Stage, and an overall increase to −1‰ by the biostratigraphy. end of the Ibexian Series. – During the earliest Dapingian Age near the Ibexian Whiterockian 5.1. Assessment of diagenesis boundary, δ13C becomes steadily more negative starting in the Tripodus laevis Zone and continuing through the Histiodella holodentata Zone. The It is important to assess to what extent diagenesis has affected these δ13 13 C trend at the top of the Ibex section is more C depleted than the rocks and their δ13C values prior to making interpretations about the − ‰ Shingle Pass section, dropping as low as 5 into the Darriwilian global significance of new isotopic data. Previous studies have explored below the contact with the overlying quartz arenite of the Watson the extent to which high porewater:rock ratios and recrystallization δ13 Ranch Quartzite (Fig. 6). The same C trend is observed in the Shingle during diagenesis can alter the original isotopic ratios and trace element δ13 − − ‰ Pass section where C values reach a minimum of 4.5 to 4 be- compositions (e.g. Brand and Veizer, 1980, 1981; Banner and Hanson, fore becoming more positive until reaching the top of the section 1990). δ13C in marine carbonate is generally thought to have a high (Phragmodus polonicus conodont Zone) at the contact with the Eureka preservation potential due to the rock-buffered nature of diagenetic sta- δ13 Quartzite (Fig. 5). While the range of C values in the Lehman Forma- bilization of unstable mineral precursors (Banner and Hanson, 1990). ‰ tion are quite variable (up to 2 swings within tens of meters of However, secondary alteration of primary seawater values via isotopic δ13 section), the overall trend at Shingle Pass indicates that C begins to exchange is possible under some circumstances, such as during the mi- − − ‰ increase to values of 2to 1 up to the contact with the Eureka gration of pore fluids between sediment grains, perhaps enhanced by Quartzite. increased bioturbation and burrowing (e.g. Metzger and Fike, 2013), and must be investigated. There are several criteria that can potentially 5. Discussion be useful in screening samples for diagenesis, including assessment of covariation of δ13Candδ18O and thin section study to characterize the These new δ13C data from the Great Basin region of the western degree of recrystallization and cementation. United States show both similarities and differences with curves in A cross plot of δ13C and δ18O data (Tables 1 and 2; Fig. 7) yields a Newfoundland and Argentina. The role that diagenesis may have played negative correlation from Shingle Pass and the Ibex area (r2 =0.19 in these trends through time is addressed first. Secondly, a look is made and 0.32, respectively), and shows no clear covariation such as would at how sea level may have affected local carbon cycling and δ13C trends be observed in settings with high porewater:rock interaction with through direct comparisons between observed shifts and published sea water of meteoric origin (Banner and Hanson, 1990). An analysis of 12 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

Table 2 δ13Candδ18O data from the Ibex section. FPG = Flat pebble conglomerate. Ages for Ordovician conodont Zones are from Cooper and Sadler (2012), but ages (*) from Cambrian-aged Zones are approximated.

Sample ID Cumulative meters Lithology Conodont Zone Formation δ13C δ18OAge (Ma)

LDN7318 39.6 Micrite C. lindstromi House 0.86 −9.00 485.52* LDN7322 45.7 Argillaceous micrite Iapetognathus House 0.85 −9.09 484.93 LDN7325 50.3 Recrystallized wackestone C. angulatus House 0.45 −8.78 484.28 LDN7329 56.4 Recrystallized micrite C. angulatus House 0.03 −8.84 483.56 LDN7331 59.5 Cherty micrite C. angulatus House −0.57 −8.87 483.21 LDN7333 62.5 Micrite C. angulatus House −0.43 −9.07 482.85 LDN7335 65.5 Recrystallized micrite C. angulatus House −0.28 −9.09 482.49 LDN7337 68.6 Argillaceous micrite C. angulatus House −0.55 −9.02 482.13 LDN7339 71.6 Recrystallized micrite C. angulatus House −0.28 −9.09 481.78 LDN7341 74.7 Argillaceous micrite C. angulatus House −0.74 −8.65 481.42 LDN7343 77.7 Argillaceous micrite C. angulatus House −0.42 −9.12 481.06 LDN7345 80.8 Micrite C. angulatus House −0.74 −8.75 480.70 LDN7347 83.8 Recrystallized micrite C. angulatus House −0.61 −9.57 480.35 LDN7349 86.9 Micrite R. manitouensis House −0.67 −8.81 480.27 LDN7351 89.9 Micrite R. manitouensis House −0.54 −8.69 480.27 LDN7353 93.0 Micrite R. manitouensis House −0.68 −8.83 480.26 LDN7355 96.0 Micrite R. manitouensis House −0.69 −9.26 480.26 LDN7357 99.1 Micrite R. manitouensis House −0.71 −8.76 480.25 LDN7359 102.1 Micrite R. manitouensis House −0.52 −2.14 480.25 LDN7361 105.2 Argillaceous micrite R. manitouensis House −0.83 −8.72 480.24 LDN7363 108.2 Micrite R. manitouensis House −0.90 −8.77 480.24 LDN7365 111.3 Micrite R. manitouensis House −0.60 −8.91 480.24 LDN7367 114.3 Argillaceous micrite R. manitouensis House −0.72 −9.14 480.23 LDN7369 117.4 Micrite R. manitouensis House −0.85 −8.75 480.23 LDN7371 120.4 Micrite R. manitouensis House −0.57 −8.82 480.22 LDN7373 123.5 Micrite R. manitouensis House −0.80 −8.69 480.22 LDN7375 126.5 Micrite R. manitouensis House −0.72 −9.19 480.21 LDN7377 129.6 Wackestone R. manitouensis House −0.85 −8.79 480.21 LDN7379 132.6 Micrite R. manitouensis House −0.55 −8.80 480.21 LDN7381 135.7 Argillaceous micrite R. manitouensis House −0.88 −8.81 480.20 LDN7383 138.7 Argillaceous micrite R. manitouensis House −0.40 −9.04 480.20 LDN7385 141.8 Argillaceous micrite R. manitouensis House −0.72 −8.64 480.19 B7396 145.3 Micrite R. manitouensis House −0.78 −8.76 480.19 LDN7389 147.9 Micrite R. manitouensis House −0.27 −8.81 480.18 B7400 148.3 Recrystallized micrite R. manitouensis House −0.45 −8.53 480.18 B7401 149.0 Micrite R. manitouensis House −0.08 −8.55 480.18 C7542 150.9 Micrite R. manitouensis House −0.03 −8.92 480.18 B7404 151.3 Micrite R. manitouensis House −0.25 −8.69 480.18 LDN7393 154.0 Argillaceous micrite R. manitouensis House 0.55 −8.48 480.17 C7544 154.0 Micrite R. manitouensis House 0.42 −8.80 480.17 B7408 154.3 Argillaceous micrite R. manitouensis House 0.49 −8.70 480.17 C7530 157.0 Argillaceous micrite Low Diversity Interval House 0.72 −8.84 480.17 LDN7395 157.0 Micrite Low Diversity Interval House 1.03 −8.94 480.17 C7546 157.0 Recrystallized wackestone Low Diversity Interval House 0.94 −8.59 480.17 B7412 157.3 Micrite Low Diversity Interval Fillmore 0.92 −8.62 480.17 C7532 160.1 Argillaceous micrite Low Diversity Interval Fillmore 0.91 −8.41 480.17 B7416 160.3 Recrystallized micrite Low Diversity Interval Fillmore 1.23 −8.34 480.17 C7534 163.1 Wackestone Low Diversity Interval Fillmore 0.94 −8.71 480.16 B7420 163.3 Recrystallized micrite Low Diversity Interval Fillmore 1.06 −8.57 480.16 C7536 166.2 Argillaceous micrite Low Diversity Interval Fillmore 1.00 −8.98 480.16 B7424 166.3 Micrite Low Diversity Interval Fillmore 1.36 −8.90 480.16 C7538 169.2 Micrite Low Diversity Interval Fillmore 0.85 −8.97 480.16 B7428 169.3 Micrite Low Diversity Interval Fillmore 0.40 −8.82 480.16 B7431 171.5 Micrite Low Diversity Interval Fillmore 0.60 −8.91 480.16 C7540 172.3 Micrite Low Diversity Interval Fillmore 0.28 −9.00 480.16 C5255 181.7 Recrystallized micrite Low Diversity Interval Fillmore −1.05 −8.73 480.15 C5258 189.9 Micrite Low Diversity Interval Fillmore −0.86 −8.58 480.14 C5263 205.8 Micrite Low Diversity Interval Fillmore 0.25 −8.57 480.12 C5268 221.0 Micrite in FPG Low Diversity Interval Fillmore −1.36 −8.47 480.11 C5273 236.3 Argillaceous micrite Low Diversity Interval Fillmore −0.86 −8.68 480.09 C5278 252.1 Micrite Low Diversity Interval Fillmore −1.16 −8.30 480.08 C5283 266.8 Packstone M. dianae Fillmore −1.14 −8.49 480.06 G7432 271.6 Micrite M. dianae Fillmore −1.01 −9.14 480.04 G7436 277.6 Micrite M. dianae Fillmore −1.23 −8.76 480.02 C5287 279.0 Micrite M. dianae Fillmore −0.61 −8.49 480.02 G7441 285.1 Wackestone in FPG M. dianae Fillmore −1.33 −8.86 480.00 G7444 289.6 Micrite in FPG M. dianae Fillmore −1.40 −8.96 479.99 G7448 295.6 Micrite M. dianae Fillmore −1.11 −9.18 479.97 G7452 301.6 Recrystallized micrite M. dianae Fillmore −0.33 −8.46 479.95 G7456 307.6 Argillaceous micrite A. deltatus/O. costatus Fillmore −0.79 −8.80 479.89 G7460 313.6 Wackestone in FPG A. deltatus/O. costatus Fillmore −1.18 −8.72 479.82 G7464 319.6 Recrystallized wackestone A. deltatus/O. costatus Fillmore −1.55 −8.70 479.75 G7468 325.6 Recrystallized wackestone A. deltatus/O. costatus Fillmore −1.46 −8.56 479.67 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 13

Table 2 (continued) Sample ID Cumulative meters Lithology Conodont Zone Formation δ13C δ18OAge (Ma)

G7472 331.6 Wackestone A. deltatus/O. costatus Fillmore −2.36 −8.65 479.60 G7476 337.6 Micrite in FPG A. deltatus/O. costatus Fillmore −0.66 −8.13 479.53 G7480 343.6 Wackestone A. deltatus/O. costatus Fillmore −0.95 −8.56 479.45 G7480.1 359.4 Micrite in FPG A. deltatus/O. costatus Fillmore −0.93 −7.98 479.26 G7480.3 364.6 Recrystallized FPG A. deltatus/O. costatus Fillmore −1.61 −7.98 479.20 G7480.7 370.6 Micrite in FPG A. deltatus/O. costatus Fillmore −1.67 −8.85 479.13 G5288 376.6 Micrite in FPG A. deltatus/O. costatus Fillmore −1.57 −9.12 479.05 G5291 394.6 Micrite in FPG A. deltatus/O. costatus Fillmore −1.07 −9.14 478.84 G5293 408.6 Micrite in FPG A. deltatus/O. costatus Fillmore −1.81 −8.68 478.67 G5296 424.6 Micrite A. deltatus/O. costatus Fillmore −1.57 −8.74 478.47 G5298 438.6 Argillaceous micrite A. deltatus/O. costatus Fillmore −1.51 −8.36 478.30 G5301 454.6 Micrite A. deltatus/O. costatus Fillmore −1.48 −8.63 478.11 G5303 468.6 Micrite A. deltatus/O. costatus Fillmore −1.48 −8.52 477.94 H5321 475.9 Micrite A. deltatus/O. costatus Fillmore −1.64 −7.83 477.85 G5306 484.6 Wackestone in FPG A. deltatus/O. costatus Fillmore −1.52 −8.59 477.74 G5308 496.6 Micrite in FPG A. deltatus/O. costatus Fillmore −1.58 −8.55 477.60 H5325 499.4 Micrite in FPG A. deltatus/O. costatus Fillmore −1.26 −8.37 477.57 H5327 511.4 Argillaceous micrite O. communis Fillmore −1.18 −8.05 477.21 G5311 514.6 Micrite O. communis Fillmore −1.40 −7.91 477.09 G5313 526.1 Micrite O. communis Fillmore −1.24 −8.56 476.63 H5330 531.4 Wackestone in FPG O. communis Fillmore −1.52 −8.12 476.41 H5333 547.9 Micrite O. communis Fillmore −1.34 −8.50 475.76 H5336 565.9 Recrystallized packstone O. communis Fillmore −0.45 −8.34 475.04 H5338 578.3 Micrite O. communis Fillmore −0.09 −8.29 474.54 H5340 589.9 Micrite in FPG O. communis Fillmore −1.10 −7.78 474.08 H5343 607.9 Wackestone R. andinus Fillmore −1.53 −7.94 473.60 H5345 619.9 Wackestone R. andinus Fillmore −1.60 −7.73 473.37 H5348 638.9 Packstone R. andinus Fillmore −1.06 −8.19 473.00 H7483 649.9 Micrite R. andinus Fillmore −1.83 −8.15 472.79 H7487 655.9 Glauconitic wackestone R. andinus Fillmore −0.85 −8.10 472.67 H7488 657.4 Micrite R. andinus Fillmore −1.32 −8.62 472.65 H7491 661.9 Wackestone R. andinus Fillmore −1.98 −8.32 472.56 H7495 667.9 Micrite nodule R. andinus Fillmore −0.64 −8.97 472.44 H7499 673.9 Argillaceous wackestone R. andinus Fillmore −1.39 −8.57 472.33 H7503 679.9 Wackestone R. andinus Fillmore −1.74 −7.41 472.21 H7507 685.9 Recrystallized micrite R. andinus Fillmore −2.18 −7.56 472.09 H7511 691.9 Argillaceous wackestone R. andinus Fillmore −1.36 −8.74 471.98 H7515 697.9 Recrystallized packstone R. andinus Fillmore −2.05 −8.37 471.86 H7516 699.4 Recrystallized micrite R. andinus Fillmore −1.66 −8.13 471.83 H7519 703.9 Packstone R. andinus Fillmore −1.43 −7.66 471.74 WW6854 708.8 Argillaceous wackestone R. andinus Wah Wah −0.91 −7.32 471.65 H7523 709.9 Micrite in FPG R. andinus Wah Wah −1.02 −8.60 471.63 WW6855 711.9 Wackestone R. andinus Wah Wah −1.52 −8.47 471.59 WW6857 714.5 Argillaceous wackestone R. andinus Wah Wah −1.27 −8.46 471.54 WW6856 714.9 Wackestone R. andinus Wah Wah −1.33 −8.39 471.53 H7527 715.9 Argillaceous wackestone R. andinus Wah Wah −1.18 −7.60 471.51 H7529 718.9 Micrite R. andinus Wah Wah −0.98 −7.88 471.45 WW6858 719.5 Argillaceous wackestone R. andinus Wah Wah −1.50 −7.94 471.44 WW6859 722.3 Argillaceous micrite R. andinus Wah Wah −0.01 −7.01 471.39 WW6860 725.6 Argillaceous wackestone R. andinus Wah Wah −1.42 −8.18 471.32 WW6861 728.1 Argillaceous micrite R. andinus Wah Wah −1.28 −8.58 471.28 WW6862 730.2 Micrite in FPG R. andinus Wah Wah −1.22 −8.41 471.24 WW6863 733.2 Micrite R. andinus Wah Wah −1.34 −8.56 471.18 WW6864 736.3 Recrystallized packstone R. andinus Wah Wah −0.64 −7.00 471.12 WW6866 744.2 Argillaceous micrite R. andinus Wah Wah −0.88 −8.22 470.96 WW6867 747.0 Argillaceous micrite R. andinus Wah Wah −1.44 −8.17 470.91 WW6868 750.0 Micrite R. andinus Wah Wah −1.43 −8.86 470.85 WW6870 756.1 Recrystallized wackestone R. andinus Wah Wah −1.08 −7.72 470.73 WW6871 759.2 Argillaceous micrite R. andinus Wah Wah −0.79 −8.72 470.67 WW6872 763.7 Argillaceous micrite R. andinus Wah Wah −1.30 −8.41 470.59 WW6873 766.8 Micrite in FPG R. andinus Wah Wah −1.42 −8.45 470.53 WW6874 769.8 Argillaceous micrite R. andinus Wah Wah −1.91 −9.93 470.47 WW6875 771.3 Brachiopod packstone R. andinus Wah Wah −1.68 −8.09 470.44 WW6876 772.9 Argillaceous wackestone T. laevis Wah Wah −1.49 −8.37 470.40 WW6877 775.9 Argillaceous wackestone T. laevis Wah Wah −1.73 −8.81 470.32 WW6878 779.0 Argillaceous micrite T. laevis Wah Wah −0.85 −7.93 470.23 WW6879 782.0 Argillaceous micrite T. laevis Wah Wah −0.67 −8.14 470.15 WW6880 784.4 Argillaceous micrite T. laevis Wah Wah −0.71 −8.40 470.08 J-10 786.6 Micrite T. laevis Juab −0.91 −8.61 470.02 J-30 792.7 Argillaceous wackestone T. laevis Juab −0.98 −8.58 469.85 J-55 800.3 Argillaceous micrite T. laevis Juab −1.08 −8.29 469.64 J-86 809.8 Argillaceous micrite T. laevis Juab −1.13 −8.78 469.38 J-98 813.4 Argillaceous micrite T. laevis Juab −1.12 −8.58 469.28 J-108 816.5 Argillaceous micrite T. laevis Juab −0.98 −8.44 469.19 J-120 820.1 Argillaceous micrite T. laevis Juab −0.98 −7.49 469.09

(continued on next page) 14 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20

Table 2 (continued) Sample ID Cumulative meters Lithology Conodont Zone Formation δ13C δ18OAge (Ma)

J-145 827.7 Argillaceous micrite T. laevis Juab −1.41 −8.73 468.88 J-155 830.8 Wackestone T. laevis Juab −1.29 −7.94 468.79 J-157 831.4 Wackestone T. laevis Juab −1.45 −8.52 468.78 KA5350 835.9 Packstone H. altifrons Kanosh −2.50 −7.57 468.68 KA5351 838.9 Wackestone H. altifrons Kanosh −2.63 −8.61 468.63 KA5357 846.4 Wackestone H. altifrons Kanosh −2.29 −7.36 468.49 KA5359 849.4 Packstone H. altifrons Kanosh −3.31 −8.11 468.43 KA5360 850.9 Recrystallized wackestone H. altifrons Kanosh −1.98 −7.58 468.40 KA5361 852.4 Packstone H. altifrons Kanosh −1.95 −6.79 468.38 KA7362 851.4 Argillaceous packstone H. altifrons Kanosh −2.78 −7.43 468.39 KA5362 853.4 Argillaceous wackestone H. altifrons Kanosh −1.85 −7.99 468.36 KA7361 861.4 Packstone H. altifrons Kanosh −2.99 −6.93 468.21 KA7367 861.4 Argillaceous packstone H. altifrons Kanosh −3.10 −7.75 468.21 KA5369 865.4 Argillaceous packstone H. altifrons Kanosh −3.34 −8.10 468.13 KA7360 871.4 Packstone H. altifrons Kanosh −3.36 −8.15 468.02 KA5375 873.4 Recrystallized packstone H. altifrons Kanosh −3.42 −7.77 467.99 KA7359 880.4 Wackestone H. altifrons Kanosh −2.93 −7.65 467.86 KA7358 893.4 Packstone H. altifrons Kanosh −3.25 −7.91 467.61 KA7357 898.4 Packstone H. altifrons Kanosh −3.32 −8.19 467.52 KA7356 913.4 Packstone H. sinuosa Kanosh −3.61 −7.94 467.37 KA7355 923.4 Packstone H. sinuosa Kanosh −3.54 −8.25 467.30 KA7354 928.4 Wackestone H. sinuosa Kanosh −3.50 −7.40 467.26 KA7352 938.4 Packstone H. sinuosa Kanosh −3.10 −7.04 467.18 CP6881 952.2 Argillaceous wackestone H. sinuosa Kanosh −2.15 −7.23 467.08 CP6883 958.2 Wackestone H. sinuosa Kanosh −2.76 −8.00 467.03 CP6884 961.2 Argillaceous wackestone H. sinuosa Kanosh −2.97 −8.03 467.01 CP6885 964.2 Packstone H. sinuosa Kanosh −3.19 −7.45 466.99 CP6886 967.2 Packstone H. sinuosa Lehman −3.40 −6.76 466.97 CP6887 970.2 Argillaceous packstone H. sinuosa Lehman −3.46 −8.29 466.94 CP6888 973.2 Packstone H. sinuosa Lehman −3.19 −8.12 466.92 CP6889 976.2 Argillaceous wackestone H. sinuosa Lehman −3.78 −8.28 466.90 CP6890 979.2 Wackestone H. sinuosa Lehman −3.76 −7.76 466.88 CP6891 982.2 Wackestone H. sinuosa Lehman −3.06 −7.66 466.85 CP6892 985.2 Packstone H. sinuosa Lehman −3.39 −8.59 466.83 CP6893 988.2 Packstone H. sinuosa Lehman −3.63 −7.31 466.81 CP6894 991.2 Packstone H. sinuosa Lehman −2.36 −7.16 466.79 CP6895 994.2 Packstone H. sinuosa Lehman −3.03 −7.18 466.76 CP6896 997.2 Argillaceous wackestone H. sinuosa Lehman −2.09 −7.17 466.74 CP6897 1000.2 Wackestone H. sinuosa Lehman −2.92 −7.17 466.72 CP6898 1003.2 Argillaceous micrite H. sinuosa Lehman −1.97 −7.74 466.70 CP6899 1006.2 Packstone H. sinuosa Lehman −2.93 −7.01 466.67 CP6900 1009.2 Wackestone H. sinuosa Lehman −2.17 −7.51 466.65 CP6901 1012.2 Wackestone H. sinuosa Lehman −3.80 −7.49 466.63 CP6902 1015.2 Wackestone H. sinuosa Lehman −4.68 −7.35 466.61 CP6903 1018.2 Argillaceous micrite H. sinuosa Lehman −3.60 −7.87 466.58 CP6904 1021.2 Micrite H. sinuosa Lehman −4.78 −7.37 466.56 CP6905 1024.2 Argillaceous wackestone H. sinuosa Lehman −3.97 −7.26 466.54 CP6906 1027.2 Packstone H. sinuosa Lehman −3.88 −7.47 466.52 CP6907 1030.2 Argillaceous wackestone H. sinuosa Lehman −3.49 −7.33 466.49 CP6908 1033.2 Argillaceous packstone H. sinuosa Lehman −3.60 −6.11 466.47 CP6909 1036.2 Argillaceous micrite H. sinuosa Lehman −2.84 −7.36 466.45 CP6910 1039.2 Packstone H. sinuosa Lehman −4.65 −7.11 466.42 CP6912 1045.2 Argillaceous micrite H. sinuosa Lehman −3.78 −7.50 466.38 CP6913 1048.2 Argillaceous wackestone H. holodentata Lehman −3.52 −6.83 466.36 CP6914 1051.2 Dolomite H. holodentata Lehman −2.87 −7.77 466.33 CP6915 1054.2 Wackestone H. holodentata Lehman −3.72 −7.21 466.31 CP6916 1057.2 Dolomite H. holodentata Lehman −4.07 −4.23 466.29 CP6917 1060.2 Argillaceous micrite H. holodentata Lehman −4.13 −5.12 466.27 CP6918 1063.2 Dolomitic wackestone H. holodentata Lehman −5.21 −6.03 466.24 CP6919 1066.2 Dolomite H. holodentata Lehman −4.47 −4.68 466.22 CP6920 1069.2 Dolomite H. holodentata Lehman −4.05 −5.02 466.20 thin sections from a representative selection of lithologies also gener- affect δ13C in most diagenetic environments (Banner and Hanson, ally shows no correlation between isotopic trends and facies (Fig. 8). A 1990). While a lack of covariation between δ13Candδ18Ovalues lack of correlation between facies and δ13C has also been reported does not definitively rule out the possibility that a strong diagenetic across a range of carbonate facies in Cambrian strata during major overprint exists, it is also true that the presence of covariation does changes in δ13C(Saltzman et al., 1998; Maloof et al., 2005). The in- not require a diagenetic explanation. A study by Bickert et al. (1997) creasing δ18Otrendfrom−10‰ to −7‰ in the Great Basin is similar on well-preserved Silurian brachiopods from Gotland concluded that to the δ18O values measured from a compilation of well-preserved the covariation of δ13C and δ18O was a primary seawater signal pro- brachiopod calcite from various sections around the globe (Veizer duced by variations in salinity under changing humid/arid climactic et al., 1999; Shields et al., 2003). Oxygen isotope ratios are more easily conditions. reset during diagenesis, even with low porewater:rock ratios less than Isotope trends from the uppermost Kanosh and Lehman formations 10:1 compared to the greater than 1000:1 ratio estimated to begin to are antithetical where δ13C decreases up section while δ18O increases C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 15

2 Ibex: r2=0.32 lithologies, however, is not present in the underlying strata, which show 18 Shingle Pass: r2=0.19 δ 1 very little scatter in O(Figs. 5 and 6).

δ13 0 5.2. Causes of C variability: sea level change and local effects

-1 The short-term relative sea level curve produced by Miller et al. (2012) from the Ibex area (see Fig. 6) does not show a clear and consis- -2 tent correlation between δ13C shifts and Lower Ordovician sea level C (‰) 13 13 change. The most prominent positive δ C shift in the Tremadocian δ -3 (base of Stairsian Stage of North American Ibexian Series) occurs in the uppermost House Formation near the contact with the Fillmore -4 Formation, which is interpreted by Miller et al. (2003, 2012) to repre- sent a major sea level fall known as the Tule Valley lowstand and Sauk -5 III–IV subsequence boundary (Fig. 8). According to the aquafacies model, this sea level fall should be associated with a negative δ13Cex- -6 -16 -12 -8 -4 0 cursion instead of a positive excursion in δ13C. The sea level curve δ18O (‰) of Miller et al. (2012) also contains numerous sea level rise–fall cycles, including four particularly well-studied and named cycles within the Fig. 7. Cross plot of δ13Candδ18O from the Shingle Pass and Ibex sections. Note the lack of a Fillmore Formation (F-1 to F-4), that do not show a predictable relation- δ13 δ18 δ18 correlation between C and O (see text for discussion). Samples with O values ship to changes in δ13C. Higher up in the Fillmore Formation during a sea above −6‰ are likely altered and dolomitic. level fall and then rise (F-2 to F-3), δ13C remains unchanged and shows no covariation (Fig. 8). Although the short-term relative sea level curve produced by Miller (Figs. 5 and 6), and represent an exception to the above interpretation of et al. (2003, 2012) from the Ibex area does not show a clear and consis- primary seawater values in these study sections. These antithetical δ13C tent correlation with δ13C shifts, this sea level curve may not be a true and δ18O isotopic trends could reflect the effects of dolomitization on reflection of global sea level due to regional factors (i.e., basin subsi- δ18O. In hand sample and thin sections, dolomite rhombs (Fig. 3G) dence, sediment supply). There are other sea level curves available are observed in association with a sharp increase in δ18O in the upper- for the Lower Ordovician, including that of Nielsen (2004), Haq and most 10–30 m of the Lehman Formation below the contact with Schutter (2008),andDronov et al. (2011), which also show many the overlying Eureka Quartzite and Watson Ranch Quartzite (Figs. 5 similar short-term fluctuations that appear to compare with the and 6). Dolomite precipitation directly from water will produce an en- curve of Miller et al. (2012). However, the Miller et al. (2012) curve richment of 18Obyabout2–6‰ when compared to calcite (McKenzie, is most appropriate to compare these new δ13C data to because the 1981; Land, 1983; Humphrey, 1988, 2000; Vasconcelos et al., 2005) chance of introducing regional effects from basins, with a sufficient de- and it appears that this may have occurred soon after or during deposi- tailed biostratigraphic framework, where other curves were based on tion of these carbonate muds under arid supratidal conditions and shal- (e.g. Baltoscandia) is minimized. [For a similar example in the Silurian low burial. This sharp increase in δ18O that is associated with dolomitic of the difficulty in comparing sea level curves from different regions,

180m Rel. Sea Level Rel. Sea Level Rel. Sea Level Rise Fall Rise Fall Rise Fall 880m 470m

160m Kanosh Shale

Fillmore Formation 840m 430m Fillmore Formation

140m 390m 800m Juab Formation House Limestone W -1 0 1 -1-2 -4 -3 -2 -1 δ13C‰ δ13C‰ δ13C‰ Bioturbated lime Wavy-bedded lime Skeletal wackestone/ Sponge/stromatolite mudstone/wackestone mudstone/wackestone packstone boundstone Cherty lime Interbedded shale Cross-bedded Flat pebble mudstone and lime mudstone lime mudstone conglomerate

Fig. 8. Stratigraphic intervals from the Ibex area with δ13C values and three-point moving averages plotted along side the interpreted relative sea level curve from Miller et al. (2012).Note the lack of correlation between facies changes and δ13C. The three stratigraphic intervals show a range of covariation between δ13C and sea level change. In the first example (left) δ13C increases while sea level is falling, which is opposite of what the aquafacies model predicts. An example of no covariation (middle) shows an interval where δ13C changes very little during an interval in the Fillmore Formation when sea level is interpreted to fall and rise (F2 to F3; Miller et al., 2012). The one interval where δ13C and sea level change shows some degree of covariance (right) is at the Juab–Kanosh contact where δ13C decreases during a sea level rise, although below this δ13Cdrop,δ13C is fairly constant throughout the Juab Formation while sea level rises and falls. W = Wah Wah Formation. 16 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 see Loydell (1998), Eriksson and Calner (2008) and Kozlowski and excursions occurred during transgressions. Thus it remains unclear to Munnecke (2010)]. what extent sea level is the main driver of δ13C excursions during the The overall pattern of variations in δ13C from Shingle Pass and Ibex is Early Paleozoic, but if eustatic changes contribute to excursions in not easily explained by the short-term changes in local sea level defined δ13C, these excursions should be globally correlative. in the Ibex area by Miller et al. (2012). However, the coarser-scale, long- term sea level curve may explain significant local magnitude differences 5.3. δ13C correlation to the Argentine Precordillera and western in δ13C between Shingle Pass and Ibex that are apparent in the Middle Newfoundland Ordovician part of the section (the Lower Ordovician δ13C variations at Shingle Pass and Ibex are quite similar in timing and magnitude) The Lower Ordovician δ13C data measured from the Shingle Pass and (Figs. 5, 6). For example, δ13C at the base of the Dapingian decreases Ibex area have excellent potential for use in global correlations because steadily from 0‰ to ca. −4‰ near the middle of the Darriwilian Stage the Great Basin contains a thick succession of carbonate rock within a in the Shingle Pass section (Fig. 5), but in the Ibex area δ13C decreases well-defined conodont biostratigraphic framework (Ethington and sharply at the base of the Kanosh Shale to ca. −4‰ much earlier by Clark, 1981; Sweet and Tolbert, 1997) that can be correlated to the the end of the Dapingian (Fig. 6). The sharp decrease in δ13Cinthe Argentine Precordillera (Lehnert, 1995a,b; Albanesi et al., 1998; Keller, Kanosh Shale at Ibex likely represents the isotopic values of a local 1999; Albanesi et al., 2013) and western Newfoundland (Stouge, water body superimposed on the global signal. The Kanosh Shale is 1984; Ji and Barnes, 1994). In addition, the δ13C trends measured from interpreted to have been deposited in a lagoon-like environment the Great Basin are similar to the δ13C trends reported from similar car- (Ross et al., 1989; Wilson et al., 1992). This oceanographic restriction bonate platform environments in the Argentine Precordillera (Buggisch may have increased the contribution of 13C-depleted waters derived et al., 2003; Thompson and Kah, 2012; Thompson et al., 2012)and from land compared to the more distal Shingle Pass locality. However, Newfoundland (Azmy and Lavoie, 2009; Thompson and Kah, 2012) in the Lehman Formation (Histiodella holodentata conodont Zone) δ13C (Figs. 9, 10). These results are also consistent with Munnecke et al. values from both sections in the Great Basin are nearly identical. More (2011), who report a limited Lower Ordovician data set from South generally, the Middle Ordovician δ13C trend from the Great Basin region China where δ13C decreases from +1‰ at the Cambrian–Ordovician may reflect a global signal (see comparisons with Argentina in boundary to less than −2‰ by the late Tremadocian before increasing Section 5.3 below) with superimposed variations caused by local effects, to ca. 0‰ at the Floian–Dapingian (Lower to Middle Ordovician) bound- including long-term sea level fall and platform restriction as well as ary. Making correlations to Munnecke et al. (2011) is challenging due to diagenesis (dolomitization). limited δ13C data in the Lower Ordovician, but future studies in China Other studies have compared Early Paleozoic δ13C excursions with will make more detailed comparisons possible. Using the estimated sea level curves (e.g. Kump et al., 1999; Saltzman et al., 2000; Eriksson ages at the base of each conodont zone in the 2012 Geologic Time and Calner, 2008; Bergström et al., 2010a; Munnecke et al., 2010; Scale (Cooper and Sadler, 2012), the age of the sections from the Great Calner et al., 2012) and no clear and consistent pattern emerges. For ex- Basin and Argentine Precordillera are approximated by interpolating ample, Eriksson and Calner (2008) and Calner et al. (2012) found that between the first occurrences of conodont zones in each measured sec- the onset of δ13C excursions in the Silurian occurred during regressions tion (Fig. 10, Table 3). rather than a sea level rise. Saltzman et al. (2000) found that the The positive δ13C shift recorded in the Great Basin in the Steptoean δ13C excursion (SPICE) peak coincided with a fall in sea Tremadocian (R. manitouensis Zone; Figs. 5 and 6) is preserved in the level in the Cambrian, as did the Late Ordovician Hirnantian δ13C excur- carbonates of the La Silla Formation in Argentina (C1 in Figs. 9, 10). In sion (Kump et al., 1999). Bergström et al. (2010a) compared sea level western Newfoundland, however, this isotope shift is apparently sequences with δ13C excursions in upper Ordovician strata of North not preserved in the shallow water carbonates of the Boat Harbour America and found that while the Fairview and Whitewater δ13C excur- Formation of the St. George Group due to a disconformity and possible sions occurred during regressions, the Kope, GICE, and Waynesville δ13C meteoric diagenesis (M. dianae Zone; Ji and Barnes, 1994; Azmy and

Shingle Pass, NV LasChacritasSec. This study La Chilca Sec. Talacasto Sec. Thompson & Kah (2012) -4 -2 0 2 LaSilla Sec. -3 -1 1 Ibex, UT ? Thompson et al. (2012) This study Buggisch etal.(2003) Azmy & Lavoie (2009) 100 m -4 -2 0 -3 -1 1 -3 -1 1 -4 -2 0 0 C4 C4

C3 C3 -3 -1 1 δ13 C2 Ccarb ‰ C2 200 m Table Head Gp. ? St. George Gp. 200 m 200 m 200 m 200 m C1 0 0 -4-20 0 0 0 13 -4 -2 0 δ C ‰ -4 -2 0 2 carb δ13C ‰ δ13C ‰ carb -3-1 1 -3 -1 1 carb δ13 δ13 Ccarb ‰ Ccarb ‰

Fig. 9. Correlation of δ13C data through three-point averages (thickness in meters) from the Shingle Pass and Ibex area to δ13C (color-coded to individual sections) from the Argentine Precordillera (Buggisch et al., 2003; Thompson and Kah (2012) and western Newfoundland (Azmy and Lavoie, 2009). Sections are hung upon the Ibexian–Whiterockian boundary (red line). Correlative δ13C isotope shifts (C1–C4) are highlighted in gray. Dap. = Dapingian. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Stage slice data modified from Bergström et al. (2009) and time slice data modified from Webby et al. (2004). C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 17

δ13C‰ δ18O‰ -5 -4 -3 -2 -1 0 1 -14 -10 -6 -2

465 Ma C4

470 Ma C3

C2 475 Ma

480 Ma C1

Shingle Pass Ibex area Argentina 485 Ma -5 -4 -3 -2 -1 0 1 -14 -10 -6 -2 δ13C‰ δ18O‰

Fig. 10. Three-point running averages of δ13Candofδ18 O from Shingle Pass, Ibex area, and Argentine Precordillera (Buggisch et al., 2003) are scaled to age using age estimates of the bases of conodont Zones according to the 2012 Geologic Time Scale (Cooper and Sadler, 2012). Ages between conodont zonal boundaries are interpolated using the meterage between zonal boundaries for each stratigraphic section. Isotope shifts C1–C4 from Fig. 9 are indicated. The similarity in isotope trends between the Great Basin and Argentina indicates that a global δ13C signal is preserved in the Lower Ordovician with minor variability from local effects superimposed on this global signal. The Middle Ordovician portions of the Great Basin curves show the effects of local factors, including diagenesis and platform restriction, superimposed on the global signal. Ord. = Ordovician, Dap. = Dapingian.

Lavoie, 2009). Above this prominent isotopic shift in the Tremadocian, Figs. 9, 10) in all sections. δ13C reaches the highest Floian values of ca. δ13C continues to rise throughout the Early Ordovician and includes a 0‰ (C3) across the Ibexian–Whiterockian boundary (Floian–Dapingian) minor 1‰ positive shift that occurs during the Early Floian (C2 of (Figs. 9, 10). δ13C trends reported by Munnecke et al. (2011) from the Honghuayuan and Huangnitang sections also show an increase through- out the Floian where δ13Creachesamaximumof~0‰. Table 3 Near the beginning of the Dapingian Age (Middle Ordovician) Geologic age and stratigraphic position (m) of the base of each conodont Zone (if present) and continuing through the Darriwilian, δ13C decreases in general at Shingle Pass, Ibex, and in the Argentine Precordillera. δ13 From Buggisch et al. (2003). Ages for Ordovician conodont Zones are from Cooper and but the rate and magnitude C decreases varies between all sec- 13 Sadler (2012), but ages for Cambrian Zones (*) are approximated. tions. In the Great Basin, δ C decreases from ca. 0‰ to −5‰ by the mid-Darriwilian, but in western Newfoundland δ13C only reaches Zone name Age of Base of zone Base of zone Base of zone − ‰ zone base (m) (m) (m) a minimum of 3 beneath the St. George unconformity (Azmy and 13 (Ma) Shingle Pass Ibex area Argentine Lavoie, 2009). In the Argentine Precordillera, δ C only reaches a low Precordillera of −1.5‰ in the La Chilca and Talacasto sections (Fig. 9; Buggisch Cordylodus intermedius* 486.5 0 0 – et al., 2003; Thompson et al., 2012). Superimposed on this long term 13 Cordylodus lindstromi* 486.0 12 29.9 1350 decrease is a 1‰ positive δ C shift in the Darriwilian (C4 of Figs. 9, Iapetognathus 485.37 30 42.7 – 10) that occurs near the base of the Histiodella holodentata/Lenodus – Cordylodus angulatus 484.28 33 50.3 variabilis conodont Zone in Argentina, but its expression in other Rossodus manitouensis 480.27 37 84.5 1382 Low Diversity Interval 480.17 141 157.0 1524 regions remains unclear due to questions surrounding conodont 13 Macerodus dianae 480.07 201 263.7 1565 zonal correlations and local influences on δ C described above in Acodus deltatus/Oneotodus 479.94 302 303.4 – Section 5.2. In the Shingle Pass section above the C4 shift δ13C becomes costatus more positive and increases to −1‰ in the Phragmodus polonicus Zone Paroistodus proteus 479.94 ––1687 just below the contact with the Eureka Quartzite (Fig. 5), which likely Oepikodus communis 477.51 470 504.0 – δ13 Prioniodus elegans 476.41 ––1715 represents the same C increase as in the middle of the Table Head Reutterodus andinus 473.83 568 596.0 – Group of western Newfoundland where Histiodella kristinae occurs Oepikodus evae 473.83 ––1780 (Fig. 4), and the δ13C increase in the Las Chacritas section of Argentina – Tripodus laevis 470.42 738 772.3 in the Eoplacognathus suecicus conodont Zone (Albanesi et al., 2013; Histiodella altifrons 468.75 816 832.3 – Paroistodus originalis 468.30 ––1885 Fig. 9). The new radiometric ages measured from zircon-bearing Histiodella sinuosa 467.46 882 901.5 – K-bentonites in the uppermost San Juan Formation in the Talacasto Histiodella holodentata 466.38 1034 1045.7 – and La Chilca sections of Argentina, which yield precise ages between Lenodus variabilis 466.38 ––1980 469.86 ± 0.62 Ma and 469.53 ± 0.62 Ma (Thompson et al., 2012), com- –– Phragmodus polonicus 463.77 1208 plicate proposed correlations of the C4 isotope shift and younger events 18 C.T. Edwards, M.R. Saltzman / Palaeogeography, Palaeoclimatology, Palaeoecology 399 (2014) 1–20 because these ages cannot yet be reconciled with Darriwilian conodonts improvements made on this manuscript. We thank R. Ethington, J. Miller, recovered by Albanesi et al. (2013) from the uppermost San Juan J. Adrain, and S. Westrop for discussion of biostratigraphy of the study Formation in the Las Aguaditas and Las Chacritas sections. areas. We also thank J. Codispoti, J. Collinson, K. Crawford, M. Edwards, A. Howard, A. Sedlacek, C. Sedlak, R. Swift, and N. Umholtz for fieldwork 6. Implications assistance. We are grateful for P. Pufahl (Acadia University) for thin section preparation, and laboratory assistance to P. Sauer and S. Young The new δ13C data presented here are from two stratigraphic sec- (Indiana University), G. Cane (Keck Paleoenvironmental and Environ- tions, each from a single study area, and preserve a high-resolution, mental Stable Isotope Laboratory at The University of Kansas), B. Gill near-continuous record of Early Ordovician seawater δ13C that can be and T. Them (Virginia Polytechnical Institute), and Y. Matsui (The Ohio correlated globally. Because the conodont faunas differ, such as with State University). Funding was provided in part by Sigma Xi Grants-in- the North American Midcontinent fauna of the Great Basin and the Aid (Edwards), a Friends of Orton Hall Research Grant (Edwards) and North Atlantic fauna of Argentina and Newfoundland (Bergström, the National Science Foundation (NSF-EAR 0745452 to Saltzman). 1986; Fig. 4), these δ13C correlations can help refine biostratigraphic correlations that are less reliable between different faunas (see Webby References et al., 2004; Cooper and Sadler, 2012). These stratigraphic sections are also important in a global context because they were deposited prior Adrain, J.M., Fortey, R.A., Westrop, S.R., 1998. Post-Cambrian trilobite diversity and evolu- tionary faunas. Science 280, 1922–1925. to and during a time of major changes to the biosphere. This event is Adrain, J.M., McAdams, N.E.B., Westrop, S.R., 2009. Trilobite biostratigraphy and revised known as the Great Ordovician Biodiversification Event (GOBE), the bases of the Tulean and Blackhillsian Stages of the Ibexian Series, Lower Ordovician, exact causes of which remain poorly understood (Webby et al., 2004; western United States. Mem. Assoc. Australas. Palaeontol. 37, 541–610. Ainsaar, L., Kaljo, D., Martma, T., Meidla, T., Männik, P., Nõlvak, Tinn, O., 2010. Middle and Trotter et al., 2008; Servais et al., 2010). Major changes in the composi- Upper Ordovician carbon isotope chemostratigraphy in Baltoscandia: a correlation tion of benthic paleocommunities are preserved across the Ibexian– standard and clues to environmental history. Palaeogeogr. Palaeoclimatol. Palaeoecol. Whiterockian boundary (Early–Middle Ordovician) as evidenced in 294, 189–201. Albanesi, G.L., Hünicken, M.A., Barnes, C.R., 1998. Biostratigrafia de conodonts de las the Shingle Pass and Ibex areas by a marked increase in skeletal shell secuencias Ordovicicas del Cerro Potrerillo, Precordillera Central de San Juan, bed abundances and thicknesses (Li and Droser, 1999) and a change Repúlica Argentina. Actas XII Academia Nacional de Ciencias, Córdoba, pp. 7–72. from trilobite- to brachiopod-dominated communities (Li and Droser, Albanesi, G.L., Bergström, S.M., Schmitz, B., Serra, F., Feltes, N.A., Voldman, G.G., Ortega, G., δ13 1999; Finnegan and Droser, 2005). The long-lived δ13C increase in the 2013. Darriwilian (Middle Ordovician) Ccarb chemostratigraphy in the Precordillera of Argentina: documentation of the middle Darriwilian Isotope Carbon Excursion Lower Ordovician that peaks at the Ibexian–Whiterockian boundary is (MDICE) and its use for intercontinental correlation. Palaeogeogr. Palaeoclimatol. consistent with a period of sustained burial of isotopically light organic Palaeoecol. 389, 48–63. matter in a stratified ocean (cf. Thompson and Kah, 2012). Azmy, K., Lavoie, D., 2009. High-resolution isotope stratigraphy of the Ordovician St. George Group of western Newfoundland, Canada: implications for global correlation. δ13 The global C signal preserved at Shingle Pass and Ibex indicates Can. J. Earth Sci. 46, 403–423. that the potential exists to study other geochemical proxies (e.g. δ13C Banner, J.L., Hanson, G.N., 1990. Calculation of simultaneous isotopic and trace element of organic matter and δ34S) to elucidate the potential effect of a variations during water interaction with applications to carbonate diagenesis. Geochim. Cosmochim. Acta 54, 3123–3137. sustained Early Ordovician period of organic matter burial (e.g. cooling Bergström, S.M., 1986. 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The new chrono- shallow nearshore environments by aiding in expanding the habitable stratigraphic classification of the Ordovician system and its relations to major regional ecospace and oxygenated environments required of benthic metazoan series and stages and to δ13C chemostratigraphy. Lethaia 42, 97–107. communities and potentially fostering higher biodiversification rates Bergström, S.M., Young, S.A., Schmitz, B., 2010a. Katian (Upper Ordovician) δ13C during the earliest pulses of the GOBE (Gill et al., 2011; Saltzman chemostratigraphy and sequence stratigraphy in the United States and Baltoscandia: a regional comparison. Palaeogeogr. Palaeoclimatol. Palaeoecol. 296, 217–234. et al., 2011). Bergström, S.M., Schmitz, B., Saltzman, M.R., Huff, W.D., 2010b. The Upper Ordovician Guttenberg δ13C excursion (GICE) in North America and Baltoscandia: occurrence, fi 7. Conclusions chronostratigraphic signi cance, and paleoenvironmental relationships. In: Finney, S.C., Berry, W.B.N. 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Carbon isotope record of Late Cambrian Ordovician sections from the Great Basin does not appear to be to Early Ordovician carbonates of the Argentine Precordillera. Palaeogeogr. Palaeoclimatol. Palaeoecol. 195, 357–373. 13 explained by sea level change alone. This δ C variability more likely Calner, M., Lehnert, O., Jeppsson, L., 2012. New chemostratigraphic data through the represents a changing global δ13C signal and supported by the excellent Mulde Event interval (Silurian, Wenlock), Gotland, Sweden. GFF 134, 65–67. correlation of δ13C trends to other basins. Cooper, R.A., Sadler, P.M., 2012. The Ordovician period. In: Gradstein, F.M., Ogg, J.G., Schimtz, M.D., Ogg, G.M. (Eds.), The Geologic Time Scale 2012, pp. 489–523. Craig, H., 1957. Isotopic standards for carbon and oxygen and correction factors for mass- Acknowledgments spectrometric analysis of carbon dioxide. Geochim. Cosmochim. Acta 12, 133–149. 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