Upper Cambrian and Lower Ordovician Conodont Biostratigraphy and Revised Lithostratigraphy, Boothia Peninsula, Nunavut

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Canadian Journal of Earth Sciences

Upper Cambrian and Lower Ordovician conodont biostratigraphy and revised lithostratigraphy, Boothia Peninsula, Nunavut

Journal: Canadian Journal of Earth Sciences

Manuscript ID cjes-2020-0006.R1

Manuscript Type: Article

Date Submitted by the 31-Mar-2020 Author:

Complete List of Authors: Zhang, Shunxin; Canada-Nunavut Geoscience Office,

upper Cambrian, Lower Ordovician, conodont biostratigraphy, Boothia Keyword: Peninsula Draft Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? :

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Upper Cambrian and Lower Ordovician conodont biostratigraphy and

revised lithostratigraphy, Boothia Peninsula, Nunavut

Shunxin Zhang

Canada - Nunavut Geoscience Office, PO Box 2319, 1106 Inuksugait IV, 1st floor, Iqaluit, Nunavut X0A 0H0, Canada; [email protected]

Draft

Correspondence author: Shunxin Zhang PO Box 2319, 1106 Inuksugait IV, 1st floor, Iqaluit, Nunavut X0A 0H0, Canada; Phone: (867) 975-4579 Fax: (867) 979-0708 Email: [email protected]

Natural Resources Canada (NRCan) contribution number: 20190339

Abstract

The strata exposed along Lord Lindsay River on southern Boothia Peninsula were

previously named the Netsilik Formation, and then recognized as the Turner Cliffs Formation;

the interpretation of the age and correlation was based on limited data. New detailed field

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investigation at 23 localities along the section resulted in the discovery of over 640 identifiable conodont specimens, with 35 species representing 16 genera, among which a new species,

Rossodus? boothiaensis n. sp., is recognized. Five North American standard conodont zone/subzone-equivalent faunas are documented from the section, namely the Hirsutodontus hirsutus Subzone-equivalent, Cordylodus angulatus, Rossodus manitouensis, Acodus deltatus/Oneotodus costatus and Oepikodus communis zones-equivalent faunas. These faunas enable a new understanding of the age and stratigraphic position of the Netsilik and Turner Cliffs formations on southern Boothia Peninsula. The Netsilik Formation can be correlated to the lower member (except for the lowest part) and upper member of the Turner Cliffs Formation; the previously unmeasured upper part of the section can be associated with the lower Ship Point

Formation. Based on the new conodont Draftdata, these three units are dated as early Age 10, late

Cambrian to middle Tremadocian, Early Ordovician; late Tremadocian, Early Ordovician; and early Floian, Early Ordovician, respectively. This study fills a gap in upper Cambrian and Lower

Ordovician biostratigraphy on Boothia Peninsula, and links the regional biostratigraphy to that of

Laurentia.

Keywords: upper Cambrian; Lower Ordovician; conodont biostratigraphy; Boothia Peninsula

Introduction

Boothia Peninsula, a large peninsula extending from Nunavut's northern mainland into the Canadian Arctic, is about 32 300 km2, located at the northernmost tip of mainland Canada, and separated from Somerset Island by Bellot Strait. Geologically, the peninsula is formed with a central spine of Precambrian metamorphic rocks, flanked by lowlands of Paleozoic carbonate

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and sandstone units (Fig. 1). Its important tectonic and geographic location makes it key for

understanding the Paleozoic stratigraphy and evolution of the Boothia Uplift.

Almost no geological information about Paleozoic rocks from the Boothia region existed

until the Geological Survey of Canada began systematic studies in the Arctic Islands in 1947.

Fortier (1948) provided a general description of the geological structure and the physiography of

the region. Fraser (1958) described the distribution of the crystalline Precambrian basement and

the overlying Paleozoic rocks on Boothia Isthmus in some detail. A brief stratigraphic and

structural report, partially including Boothia Peninsula, was published as a result of Operation

Prince of Wales in 1962 (Blackadar and Christie 1963). In the course of this operation, Christie

(1963) examined the stratigraphy of the Paleozoic rocks on Boothia Peninsula, and established

three stratigraphic units including BoothiaDraft Felix (Middle Cambrian), Netsilik (Lower

Ordovician) and Franklin Strait (Ordovician and Silurian) formations. However, all these three

formations were abandoned and replaced by the well-established stratigraphic units of the Arctic

Islands including Turner Cliffs, Ship Point, Bay Fiord, Thumb Mountain, Irene Bay and Allen

Bay formations by Miall and Kerr (1980) and Stewart (1987) (Fig. 2).

Given these limited earlier studies and the uncertain age assignments and stratigraphic

relationships between the Boothia Peninsula and other areas in the Arctic region, new data,

particularly fossil evidence, are needed to understand the Paleozoic stratigraphy on Boothia

Peninsula, and to provide evidence for supporting revisions of the stratigraphic nomenclature and

correlations to the other areas in the Arctic region, as well as linkage to the Laurentian

biostratigraphic framework. In order to meet this objective, the field investigation on Paleozoic

stratigraphy on Boothia Peninsula was carried by the author in 2018, based on which this present

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paper focuses on the upper Cambrian and Lower Ordovician stratigraphy and conodont biostratigraphy on the peninsula.

Paleozoic stratigraphic units on Boothia Peninsula

The Boothia Felix versus the Turner Cliffs formations

The Boothia Felix Formation was established by Christie (1973) for about 110 m thick sandy dolostone and sandstone with thin beds of intraformational conglomerates. This formation was assigned to the middle Cambrian based on trilobites with an upper Cambrian disconformity between the Boothia Felix and overlying Netsilik formations (Christie 1973; Fig. 2). The lithology of the Boothia Felix FormationDraft was considered to be similar to that of the Turner Cliffs Formation of the Arctic Islands, and the latter was later used in preference to the Boothia Felix

Formation (Miall and Kerr 1980; Fig. 2). The Boothia Felix Formation was correlated to the lower part of the lower member of the Turner Cliffs Formation (Stewart 1987; Fig. 2).

The Netsilik versus the Turner Cliffs formations

The Netsilik Formation was erected by Christie (1973) taking Lord Lindsay River (Fig.

3) as the type section for about 150 m of thin-bedded, dark to greenish grey weathering sandstone and sandy and shaly dolostone. At the type section, ten units were measured in the

Netsilik Formation. Based on graptolite and trilobite fossils, this formation was assigned to the

Lower Ordovician (Christie 1973). However, the Netsilik Formation was abandoned by Miall and Kerr (1980), because 1) complete sections of the formation have nowhere been seen in stratigraphic contact, and the relationship between the Netsilik and underlying Boothia Felix

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formations is problematic; and 2) the Early Ordovician fossils of Netsilik Formation were only

collected from upper part of the formation. Therefore, the Netsilik Formation is confined to the

lower part of the Lower Ordovician and overlaps the age range of the Turner Cliffs Formation;

part or all of the Boothia Felix and Netsilik formations were combined into the Turner Cliffs

Formation (Miall and Kerr 1980; Fig. 2). Further, both Boothia Felix and Netsilik formations

were together correlated to the lower member of Turner Cliffs Formation (Stewart 1987; Fig. 2).

To make the stratigraphic classification and correlation clear, it is necessary to review the

definition of the Turner Cliffs and Ship Point formations. At the type locality on the west shore

of Admiralty Inlet on Baffin Island, the Turner Cliffs Formation was divided into six members,

in ascending order: 1) edgewise conglomerate; 2) lower sandstone; 3) second edgewise

conglomerate; 4) thin-bedded argillaceousDraft dolostone; 5) third edgewise conglomerate and 6)

upper sandstone (Lemon and Blackadar 1963). The Ship Point Formation at its type locality on

the east shore of Baillarge Bay, northern Baffin Island, was originally defined for nearly 300 m

of thick bedded to massive dolostone with minor argillaceous and sandy beds lying above the

Turner Cliffs Formation (Blackadar 1956; Lemon and Blackadar 1963). It was redefined by

Trettin (1975) to include the original “upper sandstone member” (Lemon and Blackadar 1963) of

the Turner Cliffs Formation as member A of the Ship Point Formation and the original Ship

Point Formation as member B. Since then, this “upper sandstone member” has been accepted as

member A or unit 1 of Ship Point Formation in the Foxe Basin area (e.g. Sanford 1977; Sanford

and Grant 2000; Dewing and Nowlan 2012; Zhang 2013, 2018). However, because of the

different stratigraphic-structural province, these definitions were not employed by Miall and Kerr

(1980) and Stewart (1987) for Somerset Island and the Boothia Peninsula.

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On Somerset Island and Boothia Peninsula, based on Miall and Kerr (1980) and Stewart

(1987) (Fig. 2), the Turner Cliffs Formation is divided into lower and upper members. The lower member is dominated by dolostone with units of intraformational conglomerate and breccia, and the upper member is composed of resistant, massive chert-bearing dolostone with intraclast breccia and thin bedded, laminated dolostone and sandy dolostone. The boundary between the

Turner Cliffs and Ship Point formations was not well defined. It was drawn at the top of a distinct massive, pale weathering, chert-bearing dolostone of the Turner Cliffs Formation (Miall and Kerr 1980). However, it was placed at the level where the distinct, massive bedded dolostone of the upper member of the Turner Cliffs Formation passes upward into the thin to medium bedded dolostone of the Ship Point Formation (Stewart 1987). Apparently, the Ship Point

Formation on Somerset Island and BoothiaDraft Peninsula does not have a lower sandstone unit as it does at the type locality. As the project area of this study is in the same stratigraphic-structural area as that of Christie (1973), Miall and Kerr (1980) and Stewart (1987), the stratigraphic framework of Stewart (1987) is adopted by this study with some modifications.

The Franklin Strait Formation

Blackadar and Christie (1963, p. 9–10) named “beds (9)” for a succession of “light weathering, relatively competent dolostone, dolomitic sandstone, and minor sandstone containing Ordovician and probably Silurian fossils” throughout Somerset and Prince of Wales

Islands and Boothia Peninsula. This unit was formally named the Franklin Strait Formation by

Christie (1973) taking the Pasley Bay section as the type section. This formation is a sequence of dolostone and calcareous dolostone; gastropods, corals and algae indicated an age range of late

Middle Ordovician to middle Silurian (Christie 1973). The Franklin Strait Formation was

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abandoned and replaced by the Ship Point Formation and Cornwallis Group of the Arctic Islands

with an age range from late Early Ordovician to middle Silurian dissected by a couple of

interpreted disconformities (Miall and Kerr 1980; Fig. 2). Later, the Franklin Strait Formation

was correlated to the upper member of Turner Cliffs Formation and Ship Point, Thumb

Mountain and Allen Bay formations (Stewart 1987; Fig. 2). The detailed study of the Franklin

Strait Formation and its correlation with the well-established stratigraphic units of the Arctic

Islands will be reported in a forthcoming paper.

Lord Lindsay River section, outcrops and conodont samples

The Lord Lindsay River section (Fig. 3) is the type section of the Netsilik Formation

(Christie 1973). The lower and middle partsDraft of the section in this study represent the Netsilik

Formation. The rocks are nearly horizontal and outcrop discontinuously along the river, but with

an overall slightly northwestward dip so that successively higher stratigraphic levels are

encountered following the river upstream from point A (70°02'20.7"N, 93°22'52.3"W) to point B

(70°06'56.3"N, 93°31'44.5"W) in Figure 3. However, the rocks are mostly exposed in vertical

river cliffs on the concave bank of the meandering river, which makes sampling difficult. Despite

the limited time in field survey, over 25 km from point A to point B, 23 localities with workable

outcrops were found, as numbered in Figure 3.

The outcrops at localities 1–4 are composed of sandstone and conglomerate interbedded

with dolostone (Fig. 4A); those at localities 5–11 are sandstone interbedded with conglomerate

(Fig. 4B) with some trace fossils (Fig. 4C); those at localities 12–17 are dominated by sandstone

interbedded with dolostone; mud cracks are common (Fig. 4E). From locality 18 up to locality

23, some chert layers and nodules occur (Fig. 4F). Adopting the definition of Miall and Kerr

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(1980) and Stewart (1987) with chert characteristic of the upper member of the Turner Cliffs

Formation, the stratigraphic interval exposed at locality 18 is taken herein as the base of upper member of the Turner Cliffs Formation, and strata at localities 1–17 as the upper part of the lower member of the Turner Cliffs Formation (Figs. 3 and 5). Rocks exposed at localities 18–23 are uniformly thick-medium layered dolostone interbedded with thin layered dolostone; chert

(Fig. 4F) and trace fossils (Fig. 4G) occur. The boundary between the Ship Point and Turner

Cliffs formations defined by either Miall and Kerr (1980) or Stewart (1987) was not observed along this section. The boundary is tentatively drawn between the argillaceous thick-medium layered dolostone at locality 22 and medium-thin layered resistant dolostone at locality 23 (Figs.

3 and 5), with reference to the conodonts recovered from locality 23 (see discussion below).

Thus, the Netsilik Formation measured Draftby Christie (1973) at Lord Lindsay River section can be correlated to the lowest upper member and lower member (except for the lowest part) of the

Turner Cliffs Formation, rather than only the upper part of the lower member of the formation by

Stewart (1987) (Fig. 5). The upper part (localities 21–23) of the section is above the Netsilik

Formation and is assigned to the uppermost Turner Cliffs and lowest Ship Point formations by this study (Figs. 3 and 5).

Most of the outcrops were sampled for conodont microfossils, but localities 4–11 and 14–

16 were not sampled because they comprise non-calcareous sandstone and conglomerates. A total of 46 carbonate samples (each is about 3000 g) were collected with sampling interval about

1–3 meters at different localities. Most samples were collected from the middle and upper parts of the section (localities 12–13 and 17–23) that is dominated by medium-thin layered dolostone, but only a few samples were collected from lower part of the section (locality 1–3) that is mainly formed by clastics with sparse dolostone interbeds.

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Conodont biostratigraphy

No conodonts have been reported previously from the Boothia Peninsula; limited

conodonts were reported from nearby Somerset Island represented by Proconodontus muelleri

Miller from the lower member of Turner Cliffs Formation (Miall and Kerr 1980; Stewart 1987).

Therefore, the new conodont data are essential to define and refine the age of the Netsilik

Formation, the herein Turner Cliffs and Ship Point formations, and the relationship to the North

American upper Cambrian and Lower Ordovician standard conodont zonation (Cooper and

Sadler 2012; Miller 2019; Miller et al. 2003).

The Lord Lindsay River section is not continuous, and it would be impossible to establish

formal conodont zones. However, the conodontDraft faunas recovered from the section can be

described as North American standard conodont zone-equivalent. Based on the new data, five

North American standard conodont zone-equivalent faunas are recognized, namely the

Hirsutodontus hirsutus Subzone-equivalent, Cordylodus angulatus, Rossodus manitouensis,

Acodus deltatus/Oneotodus costatus and Oepikodus communis zones-equivalent faunas. The

relative age of the lithostratigraphic units on Boothia Peninsula is redefined based on the newly

identified conodont faunas (Fig. 5).

Late Cambrian-aspect fauna

Localities 1–3 and Hirsutodontus hirsutus Subzone-equivalent fauna

Localities 1–3 are in the southeastern part of the study area (Fig. 3). The lowest part of

the exposed lower member of the Turner Cliffs Formation outcrops at locality 1. The bottom and

top of the outcrop at locality 2 are laterally at the same stratigraphic level as those at localities 1

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and 3, probably with minor overlap. In total, this interval comprises about 20 m of sandstone and conglomerate interbedded with dolostone (Fig. 4A); the conodont samples were collected from dolostone beds.

Conodont diversity and richness are low at localities 1 and 2 (Table S1); no conodonts were recovered from locality 3. The rocks exposed at locality 1 are at the lowest stratigraphic position in the entire section and the rare conodonts play an important role in determining their age.

In western USA, especially in the most intensively studied Ibex area, Utah, the

Cordylodus proavus Zone, the lowest zone of the Ibexian Series and of its Skullrockian Stage, is divided into three subzones, namely the Hirsutodontus hirsutus, Fryxellodontus inornatus and

Clavohamulus elongatus subzones (RossDraft et al. 1993, 1997; Miller 2019; Miller et al. 2003, 2006;

Fig. 5). In the study area, no representatives of the latter two subzones were found. At locality 1,

Cordylodus andresi Viira and Sergeyeva (Fig. 6.3) (see discussion on this species in Taxonomy

Note below), C. cf. C. proavus Müller (Fig. 6.4), Hirsutodontus hirsutus Miller (Figs. 7.4–7.7),

Teridontus cf. T. nakamurai (Nogami) (Figs. 7.14 and 7.15), and Teridontus? sp. (Figs. 7.8–7.10) were recovered. The former three are the key representatives of the Hirsutodontus hirsutus

Subzone in the Ibex area.

The Cordylodus proavus Zone was originally considered to be Lower Ordovician (Ross et al. 1993, 1997). However, based on the definition of the Ordovician GSSP at the FAD of the euconodont Iapetognathus fluctivagus Nicoll, Miller, Nowlan, Repetski and Ethington, a position partway through the Skullrockian, the Skullrockian Stage is upper Cambrian in the lower part, including the C. proavus Zone (Cooper et al. 2001; Miller et al. 2006, 2014). The base of the C.

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proavus Zone was proposed as the base of Cambrian Stage 10 (Miller et al. 2006), but later

reconsidered as the second conodont zone of Stage 10 (Fig. 5; Miller et al. 2011, 2014, 2019).

To define the stratigraphic position of the outcrop at locality 1, the distribution of the

three species, C. andresi, C. proavus and H. hirsutus in the Ibex area is important considering: 1)

the base of the H. hirsutus subzone is marked by the lowest occurrence of Cordylodus andresi,

and C. andresi extends through the entire H. hirsutus Subzone; 2) H. hirsutus does not occur in

the lower part of the subzone; and 3) the lowest occurrence of C. proavus is in the upper part of

the subzone (Miller et al. 2003, 2006). Therefore, the associated conodonts at locality 1 suggest a

correlation with the upper H. hirsutus Subzone. However, the three species also extend into the

lower part of overlying F. inornatus Subzone in the Ibex area (Miller et al. 2003, 2006), so it

does not exclude the possibility that theDraft strata at localities 1 and 2 could be correlated to the

lower F. inornatus Subzone. Given that F. inornatus is absent, this study favours correlating

these strata to the H. hirsutus Subzone, Stage 10, Furongian, upper Cambrian (Fig. 5).

Questionable Procondontus muelleri Zone-equivalent fauna

Proconodontus muelleri Miller, the nominate species of the P. muelleri Zone was not

recovered in this study, but it was reported from the lower member of the Turner Cliffs

Formation on Somerset Island (Miall and Kerr 1980; Stewart 1987). However, based only on this

single species, it is insufficient to conclude the presence of the P. muelleri Zone-equivalent

fauna. In the Ibex area, the lowest occurrence of the species marks the base of the zone, but this

zonal species extends up into the uppermost Eoconodontus Zone, immediately below the base of

the Hirsutodontus hirsutus Subzone (Miller 2019; Miller et al. 2003; Fig. 5). Therefore, any

conodont fauna older than that in H. hirsutus Subzone in the region remains to be established.

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Cambrian–Ordovician transition

The rocks exposed at localities 4–11 are uniformly sandstones interbedded with conglomerates, from which no conodont samples were collected. Based on the conodonts from localities 1–2 and 12–13 (see discussion below), stratigraphically this clastic interval most likely includes the strata spanning from uppermost Cambrian to lowest Ordovician.

Biostratigraphically, although the Cambrian-Ordovician boundary is still debatable, this clastic interval could equate to the upper Cambrian Fryxellodontus inornatus and Clavohamulus elongatus subzones of the Cordylodus proavus Zone, C. intermedius Zone and C. lindstromi

Zone and lowest Ordovician Iapetognathus Zone or I. fluctivagus Zone (Cooper et al. 2001;

Cooper and Sadler 2012; Miller et al. 2003, 2006, 2014, 2019; Terfelt et al. 2012; Albanesi et al.

2015; Stouge et al. 2017; Wang et al. 2019),Draft if there is no stratigraphic gap within this interval

(Fig. 5).

Early Ordovician-aspect fauna

Localities 12–17 and Cordylodus angulatus Zone-equivalent fauna

Among localities 12–17, the outcrops at localities 14–16 are uniformly composed of sandstones interbedded with conglomerates; those at localities 12, 13 and 17 are each characterized by a lower part of sandstone and conglomerate and an upper part of dolostone.

Conodont diversity and richness at locality 13 are higher than those at localities 12 and

17. The outcrop at locality 13 is a nearly 20 metre vertical cliff. The lower 10 meters is a sandstone and conglomerate unit and the upper part is a dolostone unit. The lower part of the latter is greenish grey, shaly to thinly bedded dolostone, about six to seven meters in thickness,

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from which six conodont samples were collected; the upper part of the dolostone unit is thickly

bedded, and near the top of the cliff, which is inaccessible for sampling.

The six samples at locality 13 yielded the following conodonts: Cordylodus angulatus

Pander (Fig. 6.1), C. lindstromi Druce and Jones (Fig. 6.2), Drepanoistodus concavus (Branson

and Mehl) (Fig. 7.19–7.21), Teridontus cf. T. nakamurai (Figs. 7.14–7.15), Variabiloconus

bassleri (Furnish) (Figs. 8.1–8.9) and Utahconus cf. U. utahensis (Miller) (Figs. 7.1 and 7.2).

Conodonts are rare at localities 12 and 17; among three samples from locality 12, only one

sample contains ?Variabiloconus bassleri; the single sample from locality 17 contains

Cordylodus intermedius Furnish (Fig. 6.5) and V. bassleri.

To establish the stratigraphic position of strata at localities 12–17, reference to the

distribution of two species, Cordylodus Draftangulatus and Variabiloconus bassleri in the Ibex area is

critical: 1) the lowest occurrence of C. angulatus marks the base of the C. angulatus Zone, and

the species extends up to the top of the overlying Rossodus manitouensis Zone; 2) V. bassleri

occurs in the upper C. angulatus Zone, and it also extends up to the top of R. manitouensis Zone

(Miller et al. 2003, 2006). Based only on these two species, the strata at localities 12–17 can be

correlated to the upper C. angulatus Zone and the R. manitouensis Zone. However, in lacking R.

manitouensis Repetski and Ethington, this stratigraphic interval is better correlated to the upper

C. angulatus Zone (see discussion below).

The other two species, Cordylodus intermedius and C. lindstromi, in this stratigraphic

interval are also important in correlations to the Ibex area. As zonal fossils, the lowest

occurrences of the two species are in the upper Cambrian as discussed earlier, and they both

extended up to the top of Rossodus manitouensis Zone in the Lower Ordovician. Therefore, their

occurrence in the upper R. manitouensis Zone is not surprising.

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Utahconus utahensis (Miller), type species of genus Utahconus Miller, ranges from the

uppermost Cordylodus proavus Zone up to almost the top of C. intermedius Zone of the upper

Cambrian (Miller et al. 2003). Outside the type area, the upper stratigraphic limit of this species

and the genus Utahconus is to the Rossodus manitouensis Zone of the Lower Ordovician (Pyle

and Barnes 2002; Albanesi and Bergström 2004). The specimens recognized as Utahconus cf. U.

utahensis in this study possess some features that are different from U. utahensis (see discussion

in Taxonomy Notes). Therefore, it is not contradictory to conclude that the strata at localities 12–

17 should be correlated to the C. angulatus Zone (Fig. 5).

Localities 18–20 and Rossodus manitouensis Zone-equivalent fauna

The strata at localities 18–20 areDraft uniformly composed of thick-bedded dolostone

interbedded with thin-bedded and shaly dolostone and with some thin-bedded chert and chert

nodules; each outcrop is about 10 metres or more in thickness. Accepting chert as characteristic,

the strata at locality 18 are considered as the base of the upper member of the Turner Cliffs

Formation. These outcrops were well sampled for conodonts with eight, four and four samples

collected from localities 18, 19 and 20, respectively.

Conodont diversity and richness at localities 18–20 are obviously higher than those found

in lower intervals, and species from below range up into this interval, including Cordylodus

lindstromi, C. angulatus, Drepanoistodus concavus and Variabiloconus bassleri. The additional species present include D. expansus Chen and Gong (Figs. 7.29–7.32), D. nowlani Ji and Barnes

(Figs. 7.22–7.25), Loxodus bransoni Furnish (Fig. 9.14), Rossodus manitouensis Repetski and

Ethington (Figs. 9.2–9.9), R.? boothiaensis n. sp. (Figs. 10.1–10.21, except for 10.11 and

10.17), ?R. boothiaensis n. sp. (Figs. 10.11 and 10.17) and Scalpellodus? longipinnatus (Ji and

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Barnes) (Figs. 9.15–9.22), as well as paraconodont Prooneotodus rotundatus (Druce and Jones)

(Figs. 7.12 and 7.13) and Prooneotodus? sp. (Fig. 7.11). Overall, this fauna resembles that

described by Landing et al. (1986) from the Tremadocian of Quebec, in which R. manitouensis,

S. iowensis and V. bassleri are important members. The stratigraphic interval bearing this fauna

was first proposed as the Rossodus manitouensis Zone for North American marginal and open

shelf sequences and considered as being equivalent to the “Loxodus bransoni Interval” of

Ethington and Clark (1981). This zone has since been widely recognized in the North American

Midcontinent (e.g. Landing et al. 1996, 2003, 2012; Ross et al.1993, 1997; Pyle and Barnes

2002; Miller et al. 2003).

In the Ibex area, Utah, the Rossodus manitouensis Zone is divided into Loxodus bransoni

and Ventricodus spurius subzones (MillerDraft et al. 2003). The nominate species of the overlying

Ventricodus spurius Subzone was not recovered from the study area. Therefore, to establish the

stratigraphic position of strata at localities 18–20, the distribution of the two species, L. bransoni

and R. manitouensis in the Ibex area is important, namely: 1) the lowest occurrence of R.

manitouensis marks the base of the Rossodus manitouensis Zone; 2) the lowest occurrence of

Loxodus bransoni is either slightly higher or slightly lower than that of R. manitouensis, and it

ranges through most of the R. manitouensis Zone.

In the study area, Rossodus manitouensis occurs in almost all samples from localities 18

and 19. However, Loxodus bransoni is a minor component in the fauna studied, as it was noted

in Landing et al. (1986). It is not present in samples containing R. manitouensis, but rather from

samples yielding R.? boothiaensis n. sp. (see discussion in Systematic Paleontology) at locality 20.

Hence, the conodonts from locality 20 are also considered as part of the Rossodus manitouensis

Zone-equivalent fauna (Fig. 5). Other species, such as Prooneotodus rotundatus and

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Scalpellodus? longipinnatus, are also reported from the R. manitouensis Zone in the Ibex area

(Miller et al. 2003).

It is unknown whether the conodonts recovered from localities 18–20 belong to the

Loxodus bransoni Subzone-equivalent or Ventricodus spurius Subzone-equivalent, because no V. spurius was recovered and the stratigraphic range of L. bransoni is almost the same as that of R. manitouensis (Miller et al. 2003).

The interval between localities 20 and 21, and its possible stratigraphic position

Along the Lord Lindsay River from locality 20 to locality 21, sand and pebbles cover the riverbank; no outcrops were evident. Based on the conodont faunas from locality 20 and locality

21 (see discussion below), the stratigraphicDraft interval between these two localities can be roughly correlated to the Low Diversity Interval, the Macerodus dianae and lower Acodus deltatus/Oneotodus costatus zones established by Ross et al. (1993, 1997) in the North America

Midcontinent (Fig. 5), assuming that there is no stratigraphic gap within this interval.

Localities 21–22 and Acodus deltatus/Oneotodus costatus Zone-equivalent fauna

About 20 m of strata are exposed at locality 21. The lower part comprises about 10 m of sandstone, without samples collected; the upper part is about 10 m of thin to medium bedded dolostone, with two conodont samples collected. Strata at locality 22 are composed of medium interbedded with thin layered dolostone, also about 10 m thick, with five conodont sample collected from the latter lithology.

Almost all species occurring at localities 18–20 do not extend up to localities 21–23, except for Drepanoistodus concavus. Within strata at localities 21–22, conodont diversity and 16

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richness are similar to those at localities 18–20, and the recovered species include Acodus

deltatus Lindström (Figs. 11.1–11.10), A. delicatus (Branson and Mehl) (Figs. 11.11–11.24),

Cristodus loxoides Repetski (Fig. 9.1), Drepanoistodus angulensis (Harris) (Figs. 7.26–7.28),

Colaptoconus quadraplicatus (Branson and Mehl) (Figs. 8.10–8.14), Parapanderodus retractus

Ji and Barnes (8.19–8.20), and P. striatus (Graves and Ellison) (Figs 8.29–8.30).

Within this fauna, A. deltatus and A. delicatus are dominant; the former is the zonal

species of the A. deltatus/Oneotodus costatus Zone established by Ross et al. (1993, 1997) in the

type Ibexian. The base of the zone is characterized by the lowest occurrence of Acodus deltatus;

and it is associated through its range with two other species: aff. Acodus emanuelensis McTavish

and Oneotodus costatus Ethington and Brand. These, and other species listed by Ross et al.

(1993, 1997), were not recovered from theDraft samples at localities 21 and 22. Thus, the only

similarity between the fauna of the Acodus deltatus/Oneotodus costatus Zone in the Ibex area

described by Ross et al. (1993, 1997) and the one at localities 21–22 herein is that both contain

A. deltatus. As the zonal species of the Acodus deltatus/Oneotodus costatus Zone, A. deltatus

also ranges up into strata that contain Oepikodus communis Zone-equivalent fauna. (See

discussion below). Therefore, based only on A. deltatus, the strata at localities 21–22 could be

correlated to either the Acodus deltatus/Oneotodus costatus Zone or the Oepikodus communis

Zone.

To eliminate the possibility that the fauna recovered from localities 21 and 22 could be

the O. communis Zone-equivalent, the following faunas outside the Ibexian type area related to

Acodus deltatus/Oneotodus costatus Zone provide support.

 The range of A. deltatus overlaps slightly that of A. delicatus in the El Paso Group of

westernmost Texas and southern New Mexico, and this short overlapping interval is near the

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base of the Oepikodus communis Zone (Repetski 1982, personal communication, April 15,

2019); these two species occur in almost all productive samples at localities 21–22 herein.

 Colaptoconus quadraplicatus and Parapanderodus striatus occur in the Acodus

deltatus/Oneotodus costatus Zone of the Fillmore Formation in west-central Utah (Ethington

et al. 2016).

 Cristodus loxoides, Drepanoistodus angulensis and Colaptoconus quadraplicatus occur in

the interval below the Oepikodus communis Zone-equivalent strata in the St. George Group,

western Newfoundland (Ji and Barnes 1994).

 The lowest occurrence of Cristodus loxoides is several tens of meters below that of O.

communis in the Wandel Valley Formation in east and north Greenland (Smith 1991), in the

El Paso Group of westernmost TexasDraft (Repetski 1982), and in the Cow Head Group of

western Newfoundland (Stouge and Bagnoli 1988).

All these species reported from the areas outside the Ibexian type area support the proposal that the conodonts from localities 21 and 22 can be assigned to the Acodus deltatus/Oneotodus costatus Zone-equivalent. However, the only exception is Parapanderodus retractus, although is only represented by a single specimen (Fig. 8.19–8.20) from locality 21. Parapanderodus retractus is not as widely reported as those species discussed above. However, its limited known stratigraphic distribution is apparently higher than the Acodus deltatus/Oneotodus costatus Zone.

The lowest occurrence of P. retractus is in the upper part of the range of Oepikodus communis in the St. George Group of western Newfoundland (Ji and Barnes 1994). The total distribution of this species (named Striatodontus kakivangus n. sp.) is roughly same as that of Oepikodus communis in the Eleanor River Formation of the Arctic area (Nowlan 1976). Parapanderodus retractus, recovered with the Acodus deltatus/Oneotodus costatus Zone-equivalent fauna herein,

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adds new evidence that it has a longer stratigraphic range than that previously recognized

(Nowlan 1976; Ji and Barnes 1994).

Localities 23 and Oepikodus communis Zone-equivalent fauna

About 5 m medium-thin bedded resistant dolostone is exposed at locality 23. At this

locality, Acodus deltatus and A. delicatus are the major components of the conodont fauna

present; Oepikodus communis (Ethington and Clark) (Figs. 9.10–913), the nominate species of

the O. communis Zone defined by Ethington and Repetski (1984), is only represented by four

specimens.

The lowest occurrence of Oepikodus communis is at the base of the zone, but it extends

up to almost the top of overlying ReutterodusDraft andinus Zone in the Ibex area, Utah (Miller 2019).

Therefore, the presence of O. communis is not the only criterion to judge whether the fauna

recovered from locality 23 is O. communis Zone-equivalent. However, as mentioned above, the

association of Oepikodus communis together with Acodus deltatus and A. delicatus at locality 23

is similar to that in the El Paso Group of westernmost Texas and southern New Mexico, where

the range of A. deltatus slightly overlaps that of A. delicatus and this short overlapping interval is

near the base of the Oepikodus communis Zone (Repetski 1982, personal communication, April

15, 2019). Acodus deltatus questionably overlaps with Oepikodus communis in the Ibex area

(Ethington and Clark 1981). Therefore, the stratigraphic interval exposed at locality 23 is most

likely correlated to the lowest Oepikodus communis Zone, although A. deltatus questionably

extends into the overlying Reutterodus andinus Zone in the Ibex area, Utah (Miller 2019).

As discussed earlier, the boundary between the Ship Point and Turner Cliffs formations

as defined by Miall and Kerr (1980) or Stewart (1987) was not observed along the Lord Lindsay

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River section. The medium-thin bedded resistant dolostone at locality 23 is tentatively taken as the lower part of the Ship Point Formation as discussed earlier. Owing to the Oepikodus communis Zone-equivalent fauna in this interval, the following discoveries and correlations in other areas provide support for this stratigraphic assignment: 1) Oepikodus communis was recovered from dolostone unit 2, immediately above the basal sandstone unit, of the Ship Point

Formation on Melville Peninsula (Zhang 2013); 2) lower Ship Point Formation on Somerset

Island and in the Foxe Basin region was correlated to the Oepikodus communis Zone (Dewing and Nowlan 2012).

Taxonomic Notes

This present study is based on theDraft documentation of conodonts with their numerical distribution presented in Table S1. In total, over 640 identifiable conodont specimens plus numerous broken elements were recovered, with 35 species representing 16 genera identified and

8 elements indeterminate, among which one new species is recognized. Type and figured specimens are illustrated in Figures 6–11, which are deposited in the Canadian Museum of

Nature, Ottawa, with assigned curation numbers NUFV 2170–2283. Most conodonts have good preservation with a Colour Alteration Index (CAI) value of 1, indicating minimal thermal alteration (less than 50–80°C) (Epstein et al. 1977).

Most conodont species reported in this study are well known, and require little or no additional comment. Observations below concern some current taxonomic issues and the description of the new species.

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Acodus

The form genus Acodus was established by Pander (1856); Acodus erectus was

subsequently designated as its type species by Ulrich and Bassler (1926). Branson and Mehl

(1933) described a number of Early Ordovician conodont form species from Jefferson City,

Missouri, which were restudied by Kennedy (1980), who recognized an apparatus containing

five different elements including the form species A. delicatus Branson and Mehl. Based on this

apparatus, a multi-element genus Diaphorodus Kennedy, 1980 was founded taking A. delicatus

as a type species. Since then both Acodus and Diaphorodus have been used by different authors.

Sweet (1988) assembled both Acodus and Diaphorodus in Tripodus Bradshaw; however, the

name Diaphorodus, rather than Tripodus, was later employed by Sweet and Tolbert (1997).

Given that the Acodus deltatus Zone wasDraft adopted for the Geological Time Scale 2012 (Cooper

and Sadler 2012), and other new studies, such as Albanesi and Ortega (2016), this study still uses

the name Acodus, in order to maintain stratigraphic and nomenclatural stability.

Acodus deltatus (Lindström) and A. delicatus (Branson and Mehl)

McTavish (1973, pl. 1, figs. 1–9, 12–14) first reconstructed the apparatus of Acodus

delicatus (Branson and Mehl), but referred it to A. deltatus deltatus Lindström (Sweet and

Tolbert 1997). This apparatus includes six elements, namely cordylodiform, prioniodiform,

tetraprioniodiform, gothodiform, trichonodelliform, and oistodiform elements. Since then, some

of these elements have been named differently by various authors, for example:

prioniodiform = acodiform in Kennedy (1980),

tetraprioniodiform = distacodiform in Kennedy (1980), Ethington and Clark (1981), and

oepikodiform in Repetski (1982),

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trichonodelliform = acontiodiform in Kennedy (1980),

cordylodiform = drepanodiform in Kennedy (1980), and Ethington and Clark (1981)

This study continues using those terms of McTavish (1973) to describe different elements in the apparatuses of Acodus, given the earliest reconstruction.

Both Acodus deltatus and A. delicatus recognized by this study commonly occur in the same samples. To differentiate these two species, the following criteria and supporting publications are used:

Acodus delicatus is based on the reconstruction of A. deltatus deltatus by McTavish

(1973) and that of Diaphorodus delicatus by Kennedy (1980, except for oistodiform); A. deltatus is according to the reconstruction of A. deltatus in Ethington and Clark (1981, except for oistodiform) and Repetski (1982, exceptDraft for tetraprioniodiform (oepikodiform)).

 oistodiform element: Based on Sweet and Tolbert (1997), the most distinctive difference

between these two species is that the geniculate coniform (oistodiform) element in A.

delicatus has a short posterior extension of the base, but it extends somewhat farther

posteriorly in A. deltatus. Additional to this, the anterior margin of oistodiform element in A.

deltatus is straight, the best example is in Repetski (1982), and that in A. delicatus is curved.

 prioniodiform element: The posterior extension in A. delicatus is longer than that in A.

deltatus.

 tetraprioniodiform: It is symmetrical in A. deltatus; four sharp costae include anterior,

posterior and two lateral ones, and the latter are symmetrically located in near median

positions. It is asymmetrical in A. delicatus, four costae include two in posterior positions

separated by a deep trough, one anterolateral, and one at the front margin. ?Acodus sp. 3 of

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Ethington and Clark (1981) and oepikodiform of A. deltatus in Repetski (1982) are

considered as tetraprioniodiform element of A. delicatus herein.

 gothodiform: Gothodiform element is not recognized for either A. deltatus or A. delicatus in

this study.

Cordylodus andresi Viira and Sergeyeva in Viira et al. 1987

Cordylodus andresi was established by Viira and Sergeyeva (Viira et al., 1987, p. 148)

for elements with “a very large and high basal cavity and thin upper surface layer”. The elements

identified as C. andresi by Szaniawski and Bengtson (1998) have basal cavities that extend well

above the zone of maximum cusp curvature, and sometimes almost reaching the tip of the

element, further clarified the diagnosis ofDraft the species, which was followed by Landing et al.

(2007).

This species was questionably included among the species of Cordylodus by Bagnoli and

Stouge (2014). They restricted the concept of this species to be composed only of elements that

have a basal cavity extending up to reach the tip of the cusp, and restricted the distribution of

species endemically to the Baltoscandia region (Bagnoli and Stouge 2014). On the other hand,

they referred those elements with a basal cavity that does not reach close to the tip of the cusp

previously named as C. andresi to C.? aff. andresi; these include the specimens outside

Baltoscandia, such as those in Laurentia (Miller et al. 2006), Mexican West Gondwana (Landing

et al. 2007), and even within Baltoscandia itself (Szaniawski and Bengtson 1998).

The specimen (Fig. 6.3) recovered from locality 1 possesses all the features of C. andresi

as described by Viira and Sergeyeva (Viira et al. 1987) and Szaniawski and Bengtson (1998), but

the tip of the cusp is not preserved. This study follows the definition of the species by

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Szaniawski and Bengtson (1998) due to the great intraspecific variability; therefore, the name C. andresi is adopted herein.

Teridontus? sp.

Teridontus Miller includes the species of symmetrical coniform elements usually erect to reclined forming probably unimembrate apparatuses, costae lacking, cross section circular to slightly oval (Clark et al. 1981). Teridontus? sp. (Figs. 7.8–7.10) recognized by this study includes reclined, laterally symmetrical coniform elements with circular and slightly oval cross sections, which meet the criteria of the genus, but with a posterior groove beginning near bend of cusp and extending to near tip. Given this feature, these elements are questionably classified within Teridontus, although an asymmetricalDraft coniform element with very shallow groove on one lateral side described by Ji and Barnes (1994) was identified as the b element of T. nakamurai

(Nogami).

Utahconus cf. U. utahensis (Miller)

Utahconus utahensis (Miller) has an apparatus with two types of simple-cone elements, i.e. unicostate and bicostate elements; one or two costae extend from the basal margin to the tip of cusp. The costa of the unicostate element (Fig. 7.2) and the anterolateral costa of the bicostate element (Figs. 7.1 and 7.3) herein develop from the point of recurvature of the element to the tip of cusp, but not from the basal margin. It might represent a new species, but given the small number of specimens, it is recognised as Utahconus cf. U. utahensis.

Systematic Paleontology

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Order Prioniodontida Dzik, 1976

Family Oistodontidae Lindström, 1970

Subfamily Tripodontidae Sweet, 1988

Genus Rossodus Repetski and Ethington, 1983

Rossodus? boothiaensis new species

Figures 10.1–10.10, 10.12–10.16 and 10.18–10.21

ZOOBANK LSID: urn:lsid:zoobank.org:pub:1BEE23E9-2F75-43F7-991C-4B0809844927

DIAGNOSIS: Multielement conodont apparatus of Rossodus? that consists of a symmetrical

transition series of costate acontiodontiform, asymmetric coniform, drepanodontiform and

oistodontiform elements. Basal pit of acontiodontiform element is located at anterior end, and

growth lamellae are conchoidally distributedDraft from basal pit.

ETYMOLOGY: In recognition of Boothia Peninsula, where the new species was discovered

DESCRIPTION: Acontiodontiform element is symmetrical and stout with posteriorly inclined cusp.

Anterior face of cusp is round and bears blunt carina. Posterior face of cusp is deeply concave in

lower part. Basal cavity is round and small, located at anterior end of front side. Base is

expanded in three directions: laterally, posteriorly and upward. Outline of base forms a concave

isosceles triangle with vertex angle anteriorly. Growth lamellae are conchoidally distributed from

basal pit. Asymmetric coniform, drepanodontiform and oistodontiform elements are similar to

those of Rossodus manitouensis.

TYPES: Holotype NUFV 2251 (Figs. 10.5–10.7); Paratypes NUFV 2250, NUFV 2252, NUFV

2254, NUFV 2255, NUFV 2256, NUFV 2257, NUFV 2258, NUFV 2260 and NUFV 2261 (Figs.

10.1–10.4, 10.8–10.10, 10.12–10.16 and 10.18–10.21).

MATERIAL EXAMINED: thirty-nine specimens.

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OCCURRENCE: upper member of Turner Cliffs Formation at locality 20 (70°06ʹ53.5ʺN,

90°24ʹ48.6ʺW), south side of Lord Lindsay River.

DISCUSSION: The distinct acontiodontiform element with anteriorly located basal pit and

conchoidally distributed growth lamellae significantly differs from that of Rossodus

manitouensis, but it is similar to acontiodontiform element of bimembrate apparatuses of

Clavohamulus reconstructed by Ji and Barnes (1994). However, Lehnert et al. (2005) considered

that Ji and Barnes’ (1994) acontiodontiform element does not belong to the Clavohamulus

apparatus, but new genus A, and informally illustrated Gen nov. A reniformis and Gen. nov. A

sp. nov A in their text-figure 4. The acontiodontiform element of the new species Rossodus?

boothiaensis is different from that of six species described by Ji and Barnes (1994) and two species illustrated by Lehnert et al. (2005)Draft in 1) both posterior side of cusp and basal cavity deeply concave, and 2) outline of basal cavity in a shape of acute isosceles triangle.

The acontiodontiform element of new species Rossodus? boothiaensis is associated with asymmetric coniform, drepanodontiform and oistodontiform elements in two samples (SZ17-20-

03 and SZ17-20-04, Table S1), which are similar to those of Rossodus type species, R. manitouensis. Considering the similar component of apparatus to that of Rossodus and the different acontiodontiform element from that of R. manitouensis (rhombus shape of basal cavity with central basal pit), the new species is questionably classified under genus Rossodus.

The two specimens of acontiodontiform element are similar to Gen. nov. A sp. nov. 1 of

Lehnert et al. (2005, fourth image from top in text-figure 4) in having laterally wider basal cavity

than Rossodus? boothiaensis; these two specimens are questionably identified as ?Rossodus

boothiaensis herein.

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Summary

 The strata exposed along Lord Lindsay River on the southern Boothia Peninsula, most of

which were previously named Netsilik Formation, are redefined as the lower and upper

members of the Turner Cliffs Formation and lower Ship Point Formation.

 35 conodont species representing 16 genera, with 8 elements indeterminate among over

640 identifiable conodont specimens, are recognized from 23 conodont-bearing samples

at 12 localities, among which one species is new (Rossodus? boothiaensis).

 Five North American (Laurentian) standard conodont zone/subzone-equivalent faunas are

recognized, namely the Hirsutodontus hirsutus Subzone-equivalent, Cordylodus

angulatus, Rossodus manitouensisDraft, Acodus deltatus/Oneotodus costatus and Oepikodus

communis zones-equivalent faunas.

 The lower member of Turner Cliffs Formation yields Hirsutodontus hirsutus Subzone-

equivalent and Cordylodus angulatus Zone-equivalent faunas, with an interval without

conodonts in between, which can be dated as early Age 10, late Cambrian to middle

Tremadocian, Early Ordovician. The upper member of Turner Cliffs Formation contains

Rossodus manitouensis and Acodus deltatus/Oneotodus costatus zones-equivalent faunas,

with an interval without conodonts in between, which can be dated as late Tremadocian,

Early Ordovician. The lower Ship Point Formation yields an Oepikodus communis Zone-

equivalent fauna, which can be dated as early Floian, Early Ordovician. This links the

regional upper Cambrian and Lower Ordovician biostratigraphy to the Laurentian

biostratigraphic framework.

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 Tectonically, the exposed upper Cambrian and Lower Ordovician rocks on southern

Boothia Peninsula are the Paleozoic erosional remnants, which are almost undisturbed by

regional faults and folds that formed during the late Silurian-Early Devonian Boothia

Uplift. The conodonts establish the age of the youngest preserved strata in this area,

which provide direct evidence for what part of Paleozoic strata have been eroded from

the Boothia Peninsula after the late Silurian-Early Devonian Boothia Uplift.

Acknowledgments

This project is part of the GEM-2 Boothia-Somerset Integrated Geoscience Project.

Financial support from the Canadian Northern Economic Development Agency’s (CanNor)

Strategic Investments in Northern EconomicDraft Development (SINED) program, and logistic support from the Polar Continental Shelf Project (PCSP) are greatly appreciated. The author sincerely thanks M. Sanborn-Barrie (Geological Survey of Canada (GSC)) for her organizing the project, and the Inuit from Taloyoak, Nunavut, S. Hicks from Carlton University, and C. Kinney from University of Waterloo for their field assistance. The special thanks to C.R. Barnes

(University of Victoria) for his valuable suggestions on the first draft, to G. Nowlan (GSC) for his thorough internal review within Natural Resources Canada, to G. Albanesi and an anonymity for acting as journal’s scientific reviewers, and to J.B. Murphy, B. Pratt and D.L. Regier for their assistance from the journal.

Natural Resources Canada contribution number 20190339.

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Figure captions

Figure 1: Simplified geological map of Boothia Peninsula and vicinity (modified from Wheeler et al. 1997), showing the project location (red polygon; LLR: Lord Lindsay River).

Figure 2: Previous Paleozoic stratigraphic classification and correlation on Boothia Peninsula.

Ordovician and Silurian stages in the Geological Time Scale (GTS) are adopted from Cooper and

Sadler (2012) and Melchin et al. (2012), respectively. 1, 2, and 3 represent Bay Fiord, Thumb

Mountain and Irene Bay formations; N and B represent Boothia Felix and Netsilik formations, respectively.

Figure 3: A) Lord Lindsay River section on a Google Maps TM base (Google 2013); B) Sketch of Lord Lindsay River with sampling localitiesDraft shown by dots and numbers, Christie’s (1973) section and Netsilik Formation shown by black dashed line of north-south direction, and the boundaries between different stratigraphic units and general trend of stratigraphic strike showed by red dashed lines of northeast-southwest direction. Red and yellow dots represent observed and sampled localities, respectively.

Figure 4: Typical lithologies along the Lord Lindsay River section. A) greenish grey weathering shaly dolostone overlying dark grey massive conglomerate, locality 2; B) grey medium-massive sandstone (outcrop about 15–20 m high), locality 8; C) trace fossils in sandstone, locality 7; D) greenish grey medium-massive argillaceous dolostone, locality 13; locality 19; E) mud cracks, locality 16; F) thin bedded dolostone interbedded with chert, locality 19; G) trace fossil in dolostone, locality 23.

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Figure 5. Upper Cambrian and Lower Ordovician stratigraphy at Lord Lindsay River section,

southern Boothia Peninsula and its correlation with the Upper Cambrian and Lower Ordovician

chronostratigraphic and biostratigraphic framework adopted from Cooper and Sadler (2012) and

Peng et al. (2012). The Upper Cambrian conodont zonation adopted from Miller (2019) and

Miller et al. (2003) with tentative chronostratigraphic correlation; the Lower Ordovician

conodont zonation adopted from Cooper and Sadler (2012). L.S.: lithostratigraphy.

Figure 6. Species of Cordylodus Pander with observable basal cavity. A, photographs with Zeiss

Axio Cam ICc 3 camera (1–4 and 5 with black and white background, respectively); B, the

corresponding illustrations showing the basal cavity; C, the corresponding SEM photos. 1. inner

lateral view of P element of Cordylodus angulatus Pander, from 18-04, locality 18, NUFV 2170;

2. inner lateral view of S element of CordylodusDraft lindstromi Druce and Jones, from 13-05,

locality 13, NUFV2171; 3. inner lateral view of S element of Cordylodus andresi Viira and

Sergeyeva, from 01-01, locality 1, NUFV 2172; 4. inner lateral view of M element of

Cordylodus cf. C. proavus Müller, from 01-01, locality 1, NUFV 2173; 5. lateral view of M

element of Cordylodus intermedius Furnish, from 17-01, locality 17, NUFV 2174. The white

scale bars represent 0.25 mm.

Figure 7

1–3. Utahconus cf. U. utahensis (Miller). (×170); from 13-01, locality 13; 1, outer lateral view of

bicostate element, NUFV 2175; 2, posterior-lateral view of unicostate element, NUFV 2176; 3,

inner lateral view of bicostate element, NUFV 2177; 4–5. Hirsutodontus cf. H. simplex (Druce

and Jones) (×110); from 01-02, locality 1, NUFV 2178; anterior and lateral views of the same

specimen; 6–7. Hirsutodontus hirsutus Miller (×110); from 01-01, locality 1, NUFV 2179;

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anterior and lateral views of the same specimen; 8–10. Teridontus? sp. (×90); from 01-01, locality 1; 8, posterior-lateral view of round element, NUFV 2180; 9, lateral view of slightly compressive element, NUFV 2181; 10, lateral view of round element, NUFV 2182; 11.

Prooneotodus? sp. (×65); from 18-03, locality 18, NUFV 2183; lateral view oistodiform; 12–13.

Prooneotodus rotundatus (Druce and Jones) (×85); from 18-02, locality 18; lateral views of

NUFV 2183 and NUFV 2184; 14–15. Teridontus cf. T. nakamurai (Nogami) (14×100; 15×75); from 01-01, locality 1; lateral views of simple cone element, NUFV 2186 and NUFV 2187; 16.

Phosphannulus universallis Müller, Nogami and Lenz (×90); from 18-05, locality 18, NUFV

2188; upper view; 17–18. Teridontus nakamurai (Nogami) (×90); 17 from 13-01, locality 13,

NUFV 2189; 18 from 18-05, locality 18, NUFV 2190; 19–21. Drepanoistodus concavus

(Branson and Mehl); (19–20×55; 21×45);Draft from 20-03, locality 20; 19, outer lateral view of curvatiform, NUFV 2191; 20, lateral view of suberectiform, NUFV 2192; 21, inner lateral view of homocurvatiform, NUFV 2193; 22–25. Drepanoistodus nowlani Ji and Barnes (22 and 24

×85; 23 and 25 ×60); 22 and 24 from 18-05, 23 and 25 from 18-02, locality 18; 22, lateral view of suberectiform, NUFV 2194; 23, inner lateral view of oistodiform, NUFV 2195; 24, inner lateral view of homocurvatiform, NUFV 2196; 25, inner lateral view of curvatiform, NUFV

2197; 26–28. Drepanoistodus angulensis (Harris) (26 and 27 ×100; 28 ×80); from 21-01, locality

21; 26, inner lateral view of curvatiform, NUFV 2198; 27, inner lateral view of homocurvatiform, NUFV 2199; 28, inner lateral view of oistodiform, NUFV 2200; 29–32.

Drepanoistodus expansus (Chen and Gong) (29×110; 30–32×60); from 18-03, locality 18; 29, lateral view of suberectiform, NUFV 2201; 30, inner lateral view of homocurvatiform, NUFV

2202; 31, anterior-inner lateral view of homocurvatiform, NUFV 2203; 32, inner lateral view of oistodiform, NUFV 2204.

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Figure 8

1–9. Variabiloconus bassleri (Furnish) (×70); from 18-02, locality 18; 1 and 2, lateral and

posterior view of quadri-costate element, NUFV 2205; 3, inner lateral view of bi-costate

element, NUFV 2206; 4 and 5, lateral and posterior view of symmetric tri-costa element, NUFV

2207; 6 and 7, lateral and posterior-lateral view of asymmetric tri-costa element, NUFV 2208; 8,

inner lateral view of acostate element, NUFV 2209; 9, inner lateral view of uni-costate element,

NUFV 2210; 10–14. Colaptoconus quadraplicatus (Branson and Mehl) (×75); from 21-01,

locality 21; 10, inner lateral view of symmetricDraft quadri-costate element, NUFV 2211; 11, inner

lateral view of acostate element, NUFV 2212; 12, inner lateral view of asymmetric quadri-

costate element, NUFV 2213; 13 and 14, inner lateral and posterior view of symmetric quadri-

costate element, NUFV 2214; 15. Semiacontiodus sp. 1 (×75); from 18-02, locality 18; posterior

view of symmetric simple cone element, NUFV 2215; 16. Semiacontiodus? sp. 1 (×125); from

18-02, locality 18; posterior view of symmetric simple cone element, NUFV 2216. 17.

Semiacontiodus sp. 2 (×120); from 18-02, locality 18; posterior view of symmetric simple cone

element, NUFV 2217; 18. Semiacontiodus? sp. 2 (×115); from 18-02, locality 18; posterior view

of symmetric simple cone element, NUFV 2218; 19–20. Parapanderodus retractus Ji and Barnes

(×95); from 21-01, locality 21; anterior and posterior view of the same specimen, NUFV 2219;

21–28. Semiacontiodus iowensis (Furnish) (×70); from 20-03, locality 20; 21, posterior view of

asymmetric tri-costate element, NUFV 2220; 22, posterior view of multi-costate element, NUFV

2221; 23 and 27, posterior view of symmetric tri-costate element NUFV 2222, 2225; 24 and 25,

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inner and outer lateral views of multi-costate element, NUFV 2223; 26, posterior view of subsymmetric tri-costate element, NUFV 2224; 28, lateral view of asymmetric tri-costate element, NUFV 2226; 29–30. Parapanderodus striatus (Graves and Ellison) (18×75; 19×110); from 21-01, locality 21; 29, posterior view of symmetric element, NUFV 2227; 30, inner lateral view of asymmetric element, NUFV 2228; 31. Cordylodus sp. 1 (×85); from 18-01, locality 18; inner lateral view of S element, NUFV 2229; 32. Cordylodus sp. 2 (×140); from 18-07, locality

18; inner lateral view of M element, NUFV 2230.

Figure 9

1. Cristodus loxoides Repetski (×80); from 21-01, locality 21; inner lateral view of M element,

NUFV 2231. 2–9. Rossodus manitouensisDraft Repetski and Ethington (×90 except 4–6×115); from

18-02 except 2 and 3 from 18-03, locality 18; 2 and 4, posterior view of asymmetric coniform element, NUFV 2232, 2234; 3, posterior view of acontiodontiform element, NUFV 2233; 5 and

6, anterior and posterior view of asymmetric coniform element, NUFV 2235; 7, outer lateral view of oistodontiform element, NUFV 2236; 8 and 9, outer and inner lateral view of drepanodontiform element, NUFV 2237; 10–13. Oepikodus communis (Ethington and Clark)

(×120); from 23-01, locality 23; 10, inner lateral view of M element, NUFV 2238; 11, inner lateral view of Sc element, NUFV 2239; 12, inner lateral view of P element, NUFV 2240; 13, inner lateral view of Sb element, NUFV 2241; 14. Loxodus bransoni Furnish (×90); from 20-03, locality 20; inner lateral view, NUFV 2242; 15–22. Scalpellodus longipinnatus (Ji and Barnes)

(10–14 ×70; 15–17 ×65); from 20-03, locality 20; 15 and 16, posterior view of narrow acontiodiform element, NUFV 2243, 2244; 17, posterior view of broad scandodiform element,

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NUFV 2245; 18 and 19, posterior and lateral view of narrow scandodiform element, NUFV

2246; 20–22, posterior view of broad acontiodiform element, NUFV 2247–2249.

Figure 10

1–10, 12–16, 18–21. Rossodus? boothiaensis n. sp. [(1–3, 5–10, 16) ×100; 4×360; (12–14, 20–

21) ×80; (15, 18–19) ×70], from 20-03, locality 20; 1–4, posterior, posterior-basal, lateral view,

and basal enlargement of acontiodontiform, NUFV 2250; 5–7, basal-lateral, posterior-lateral, and

posterior-basal view of acontiodontiform element, NUFV 2251; 8–10, posterior, posterior-basal,

and posterior view of acontiodontiform element, NUFV 2252; 12 and 13, inner lateral view of

drepanodontiform element, NUFV 2254,Draft 2255; 14–16, inner lateral view of asymmetric

coniform element, NUFV 2256–2258; 18–21, inner and outer lateral view of oistodontiform

element, NUFV 2260, 2261; 11 and 17. ?Rossodus boothiaensis n. sp. (11×115, 17×100); from

20-03, locality 20; posterior view of acontiodontiform element, NUFV 2253, 2259.

Figure 11

1–10. Acodus deltatus Lindström (×75 except 3–4×52, 5×100, 9×60); from 23-03, locality 23

except 10 from 21-01, locality 21; 1–2, inner lateral view of prioniodiform element, NUFV 2262,

2263; 3–4, inner lateral view of cordylodiform element, NUFV 2264, 2265; 5–6, lateral view of

trichonodelliform element, NUFV 2266, 2267; 7–8, lateral and posterior view of

tetraprioniodiform element, NUFV 2258; 9–10, inner lateral view of oistodiform element, NUFV

2269, 2270; 11–24. Acodus delicatus Branson and Mehl (×75 except 11, 12 and 19 ×45, 22–

24×60); from 23-03, locality 23 except 20 from 21-01, locality 21; 11–12, inner lateral view of

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cordylodiform element, NUFV 2271, 2272; 13–15, inner lateral view of prioniodiform element,

NUFV 2273–2275; 16–18, outer-lateral, posterior-lateral, and posterior view of tetraprioniodiform element, NUFV 2276; 19–20, inner lateral view of oistodiform element,

NUFV 2277, 2278; 21, posterior view of trichonodelliform element, NUFV 2279; 22–24, posterior-lateral, nearly posterior and inner-lateral view of tetraprioniodiform element, NUFV

2280; 25. Acodus sp. (×45); from 23-03, locality 23; posterior view of trichonodelliform element,

NUFV 2281; 26–27. Acodus brevis Branson and Mehl s. f. (×60); 26 from 23-10, 27 from 23-03, locality 23; inner lateral view of prioniodiniform, NUFV 2282, 2283.

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