Canadian Journal of Earth Sciences
Carbon-isotope stratigraphy of the Furongian Berry Head Formation (Port au Port Group) and Tremadocian Watts Bight Formation (St. George Group), western Newfoundland and the correlative significance
Journal: Canadian Journal of Earth Sciences
Manuscript ID cjes-2018-0059.R1
Manuscript Type: Article
Date Submitted by the 15-Jun-2018 Author:
Complete List of Authors: Scorrer, Sebastian; Memorial University Of Newfoundland Department of Earth Science,Draft Earth Sciences Azmy, Karem; Memorial University of Newfoundland, Stouge, Svend; Natural History of Denmark , University of Copenhagen
HERB Event, High resolution chemostratigraphy, Furongian (latest Keyword: Cambrian), East Isthmus Bay
Is the invited manuscript for Advances in low temperature geochemistry diagenesis seawater and consideration in a Special climate: A tribute to Jan Veizer Issue? :
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1 Carbon-isotope stratigraphy of the Furongian Berry Head Formation (Port au
2 Port Group) and Tremadocian Watts Bight Formation (St. George Group),
3 western Newfoundland and the correlative significance
4 5 Sebastian Scorrera*, Karem Azmya, and Svend Stougeb 6 7
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25 Email: [email protected]
26 Abstract: Carbon-isotope stratigraphy of the Furongian (Stage 10; Upper Cambrian) and
27 Tremadocian (lowermost Ordovician) reveals distinct variations from the carbonates of the Berry Head
28 and Watts Bight formations of the East Isthmus Bay section that accumulated in a shallow-marine
29 setting on the eastern Laurentian platform/passive margin in western Newfoundland, Canada. The East
30 Isthmus Bay δ13C values show insignificant correlation with their Sr (R2 = 0.04), Mn (R2 = 0.001) and
31 Fe (R2 = 0.02) counterparts, implying preservation of at least near-primary C-isotope compositions. The
32 investigated section is largely fossil poor but the δ13C profile shows a pattern with distinct variations 33 that can be matched with those of the westernDraft Laurentian Lawson Cove Auxiliary Boundary 34 Stratigraphic Section and Point (ASSP) section, Utah, USA. Therefore, a conodont biozonal scheme
35 was possible to reconstruct by matching the δ13C profile with its counterpart from the Lawson Cove
36 ASSP section. At the base of the East Isthmus Bay section, the δ13C profile exhibits a broad excursion
37 (the top of the Herllnmaria-Red Tops Boundary, HERB Event), which can be matched with the base of
38 the Eoconodontus Zone (mid-Furongian), followed by an enrichment trend through the Cordylodus
39 intermedius Zone (top Furongian). A positive excursion (Hirsutodontus simplex spike or HSS) is
40 recorded in the Cordylodus intermedius Zone (the top Cambrian), and a prominent positive peak
41 characteristic for the Cordylodus lindstromi Zone is recorded from the top of the investigated section.
42 The δ13C values of the Newfoundland carbonates are generally ~ 1 ‰ VPDB lower than those of
43 Lawson Cove, which is likely attributed to a relative higher productivity and/or organic burial in the
44 Utah region.
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46 Key Words
47 HERB Event, High resolution chemostratigraphy, Furongian (latest Cambrian), East Isthmus Bay
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50 Introduction
51 In the last decade, the δ13C profiles of Upper Cambrian marine carbonates of Port au Port
52 Peninsula, western Newfoundland (e.g., Salzman et al. 2004; Hurtgen et al. 2009), documented the
53 presence of the global distinct carbon-isotope event called the Steptoean positive carbon-isotope
54 excursion (or SPICE) in the Petit Jardin Formation at Felix Cove. The excursion has been dated by
55 trilobites (Aphelaspis, Dunberbergia, and ElviniaDraft zones) to the Steptonian Stage of the Upper
56 Cambrian (Westrop, 1992; Cowan and James, 1993; Knight and Boyce, 2002; Salzman et al. 2004) on
57 the south coast of Port au Port Peninsula (Fig. 1). Hurtgen et al. (2009) presented both δ34S and δ13C
58 isotope data from the Port au Port Group and recorded two δ13C excursions where the positive
59 excursion seen in the upper Felix Cove Member was referred to the SPICE event (Salzman et al. 2004).
60 The authors investigated the March Point and Felix Cove formations of the Port au Port Group and
61 their studies focused on sections exposed in the steep coastal cliffs along the south coast of the Port au
62 Port Peninsula.
63 Azmy and Lavoie (2009) constructed the δ13C-isotope profile for the St. George Group (Lower
64 Ordovician), western Newfoundland and Azmy et al. (2010) discussed its correlation along the
65 Laurentian margin with northeast Greenland.
66 A high-amplitude negative carbon-isotope excursion, known as the Hellnmaria-Red Tops
67 Boundary or HERB Event (Ripperdan, 2002), has been investigated in sections from Utah (USA),
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68 Queensland (Australia) and Newfoundland (Canada) among others (Ripperdan et al. 1992; Buggisch et
69 al. 2003; Jing et al. 2008; Li et al. 2011; Miller et al. 2014; 2015b; Azmy, 2018). The HERB Event is
70 represented by a negative δ13C excursion that consists of several high-amplitude δ13C peaks in Upper
71 Cambrian sections and can be used for global correlations. In the Green Point, western Newfoundland,
72 a negative δ13C shift of ~ 4 ‰ VPDB was observed (Miller et al. 2011), and a similar shift was also
73 documented in the other sections. However, the strength of the excursion (amplitude of peaks) varies
74 globally due to the local disparities of organic primary productivity in response to sealevel changes.
75 The Green Point (Cow Head Group) slope deposits are poorly fossiliferous, but the HERB Event
76 occurs at the base of the Eoconodontus notchpeakensis conodont Subzone (Miller et al. 2014; Stouge et 77 al. 2017). Draft 78 The equivalent Lawson Cove section, located in Utah, USA, has been extensively investigated by
79 Miller et al. (2003; 2011; 2014; 2015a; 2015b). It displays a well-exposed Upper Cambrian to
80 lowermost Ordovician succession, consisting of shallow marine carbonate platform deposits abundant
81 in well preserved shelly fossils assemblages (trilobites and brachiopods) and conodonts (Miller et al.
82 2015b). Recently, the Lawson Cove section has been approved as an ASSP (Auxiliary Boundary
83 Stratigraphic Section and Point) section for the Cambrian−Ordovician transition (Miller, 2017) and
84 represents the best investigated section in Utah. The well-established conodont biozonation in the
85 Lawson Cove section is also tied to a well-defined δ13C profile reflecting the HERB Event which
86 occurs at the base of the Eoconodontus notchpeakensis Subzone (Ripperdan, 2002; Miller et al. 2015b).
87 The current investigation focuses on the Upper Cambrian to Lower Ordovician carbonates
88 exposed East of Isthmus Bay on the southwestern coast of Newfoundland. The section was selected
89 because it is a well exposed, long continuous carbonate section that lacks fossils (Ji and Barnes, 1994)
90 and provides a direct and ideal application of the chemostratigraphy as a tool of correlation. The
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91 correlation of this section will enhance the regional correlation of the HERB Event across
92 Newfoundland and beyond.
93 The purpose of the current investigation is (1) to present the carbon-isotope stratigraphy of the
94 Furongian (Upper Cambrian) Berry Head Formation of the Port au Port Group extending into the
95 Tremadocian (Lower Ordovician) Watts Bight Formation of the St. George Group to fill the gap
96 between the δ13C curve of Hurtgen et al. (2009) and that of Azmy and Lavoie (2009), and (2) to
97 discuss correlation of the conodont biozonation scheme with the mainly barren (fossil-poor) carbonates
98 of the Berry Head and Watts Bight formations of western Newfoundland and the conodont-rich
99 carbonates of the Lawson Cove ASSP section (Utah) by matching the δ13C isotope curves, following 100 the approach promoted by Glumac et al. (2002a;Draft 2002b). 101
102 Geological setting and stratigraphy
103 The Furongian (Upper Cambrian) to Tremadocian (Lower Ordovician) carbonates in western
104 Newfoundland represent the Canadian segment of the extensive peritidal to shallow-marine carbonates
105 that covered most of the Laurentian paleocontinent (James et al. 1989; Knight and Boyce, 2002; Lavoie
106 et al. 2003, 2013). The carbonates accumulated on the Laurentian mixed carbonate-clastic platform in a
107 passive margin setting along the eastern Iapetus Ocean (Chow and James, 1987a; James et al. 1989;
108 Cowan and James, 1993; Lavoie et al. 2013). Today, these deposits are extensively preserved in coastal
109 and inland exposures in western Newfoundland (Knight and Boyce, 2002).
110 On the west coast of Newfoundland, the peritidal to shallow marine, Middle Cambrian to Lower
111 Ordovician carbonate rocks are referred to as the Port au Port and St. George groups (Fig. 2; James and
112 Stevens, 1986; James et al. 1989; Ji and Barnes, 1994; Lavoie et al. 2013). The Port au Port Group
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113 comprises the March Point, Petit Jardin (with five members) and Berry Head formations (Fig. 2; James
114 and Stevens, 1986; James et al. 1989; Lavoie et al. 2013). The sequence generally consists of
115 limestones, dolomitic limestones and dolomites, which contain shallow-marine carbonate components
116 such as limemud, bioclastics, ooids, and oncoids (Chow and James, 1987b; Knight and James, 1987)
117 associated with abundant microbial stromatolite and thrombolite complexes in the Cambrian
118 accumulated in intertidal to subtidal environments. In the Lower Ordovician, extensive Renalcis
119 mounds appeared (Pratt and James, 1982, 1986; Kennard and James, 1986; Knight et al. 2008).
120 The biostratigraphic ages of the Port au Port Group carbonates are constrained from the trilobite
121 Bolaspidella Zone (Series 3; Cambrian) at the base through the Furongian Series (Upper Cambrian) 122 whereas fossils are missing in the upper strata.Draft The St. George Group comprises all of the Lower 123 Ordovician extending into lower Middle Ordovician (Whiterockian). The biostratigraphy of the
124 sedimentary rocks is based on shelly fossil assemblages of trilobites, cephalopods, gastropods and
125 brachiopods (e.g., Westrop, 1992; Rohr et al. 2000; Boyce et al. 2011) as well as conodonts (Barnes
126 and Tuke, 1970; Stouge, 1982; Ji and Barnes, 1994; Boyce and Stouge, 1997).
127 The succession at the East Isthmus Bay section is ~ 200 m thick and composed of limestones,
128 dolomitic limestone and dolomites (Fig. 3), with several horizons of oolites, thrombolites and
129 stromatolites. Shale/siltstone beds and chert may occur with some minor conglomeratic interbeds at the
130 bottom of the section (Fig. 3). These lithologic features suggest shallow-water environment particularly
131 in the upper part of the section.
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133 The study area
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134 The East Isthmus Bay section (Ji and Barnes, 1994) is a coastal cliff exposure situated at the
135 southern coast of Newfoundland and to the east of the Port au Port Peninsula (Fig. 1). The base of the
136 investigated section starts to the east (48° 33’ 05.6” N; 58° 42’ 03.1” W), and the top of the section
137 terminates approximately 200 meters northwest along the coast (48° 33’ 09.2” N; 58° 42’ 38.0” W).
138 The Berry Head Formation and the conformably overlying Watts Bight Formation (Tremadocian,
139 Lower Ordovician) are wellexposed in the coastal cliffs. The base of the Berry Head Formation (Port
140 au Port Group) is incomplete at the section as the lowermost part is covered and there are some ‘gaps’
141 in the upper part (Fig. 3). Only the lowermost 30 meters of the Watts Bight Formation is exposed at the
142 East Isthmus Bay section with the strata dipping at a low angle north-northwest. 143 Ji and Barnes (1994) recorded a meagerDraft and undiagnostic fauna composed of mainly long-range 144 conodont species (e.g., Teridontus nakamurai, Cordylodus lindstromi and species of Semiacontiodus)
145 from the uppermost part of the succession. The possible presence of Cordylodus lindstromi indicates
146 that the top beds in the section should be referred to the Cordylodus lindstromi Zone (lowermost
147 Ordovician).
148
149 Material and methods
150 Samples were collected from the Upper Cambrian to Lower Ordovician East Isthmus Bay section at
151 intervals between 20 and 100 cm. Thin sections were cut, stained with a mixture of potassium
152 ferricyanide and alizarin red-S (Dickson, 1966), and examined petrographically using a polarizing
153 microscope. Cathodoluminescence (CL) observations were performed using a Technosyn 8200 MKII
154 cold cathodluminoscope operated at 8 kV accelerating voltage and 0.7 mA current.
155 Mirror-image slabs of thin sections were polished, washed with deionized water and dried at 40°C
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156 overnight prior to microsampling. Guided by the observations from petrographic examination of the
157 thin sections, samples were extracted carefully from the most micritic spots in the clean mirror-image
158 slabs using a low-speed microdrill, avoiding cement and veins.
159 For C- and O-isotope analyses, about 200 µg of powder sample was reacted in an inert atmosphere
160 with ultrapure concentrated (100 %) orthophosphoric acid at 70oC in a Thermo–Finnigan GasBench II
161 at Memorial University of Newfoundland. The liberated CO2 was automatically delivered to a
162 ThermoFinnigan DELTA V plus isotope ratio mass spectrometer in a stream of helium, where the gas
163 was ionized and measured for isotope ratios. Uncertainties of better than 0.1 ‰ (2σ) for the analyses
164 were determined by repeated measurements of NBS-19 (18O = – 2.20 ‰ and 13C = + 1.95 ‰ vs. 165 VPDB) and L-SVECS (18O = – 26.64 ‰ andDraft 13C = – 46.48 ‰ vs. VPDB). The isotopic values (δ13C 166 and δ18O) were expressed as per mil (‰) relative to the Vienna Pee Dee Belemnite (VPDB) (Table 1,
167 Appendix 1).
168 For trace element analyses, a subset of sample powder (~ 10 mg each) was digested in 0.2 M HNO3
169 for 28 hours and analyzed for major and minor elements using an Elan DRC II ICP-MS (Perkin Elmer
170 SCIEX) at Memorial University of Newfoundland. The relative uncertainties of the measurements are
171 better than 5 %, and results (Appendix 1) are normalized to a 100 % carbonate basis (e.g., Brand and
172 Veizer, 1980; Veizer et al. 1999; Azmy et al. 2014).
173
174 Results
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176 Petrography
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177 The sampled carbonates are dominated by fine-grained carbonate mudstones with minor oolitic
178 grainstones interbeds. The bottom of the East Isthmus Bay section is dolomitized and composed mainly
179 of fenestral dolomicrites with minor beds of crystalline dolomite and breccia. Petrographic
180 investigation shows that the sampled carbonates from the East Isthmus Bay section have mainly
181 retained at least their near-micritic texture (4−20 µm; Figs. 4A, B) except for minor recrystallization
182 caused by dolomitization in the lower part of the succession. Samples appear dull to non-luminescent.
183 Ooids were observed in some thin sections (e.g., sample EI-72 and EI-132, C), which have been
184 interpreted in earlier Port au Port Group studies to have accumulate in situ (Cowan and James, 1993).
185 186 Stable isotopes Draft 187 The geochemical characteristics of the investigated carbonates are tabulated in Appendix 1 and
188 their statistics are summarized in Table 1. The δ13C values of the East Isthmus Bay carbonates range
189 from −2.5 to 0.2 ‰ VPDB and are slightly more depleted (−1.2±0.5 ‰ VPDB, n = 92, Table 1; Fig. 3)
190 relative to their Lawson Cove counterparts (0.4±0.5 ‰ VPDB, n = 113, Miller et al. 2015b). When
191 compared to the δ13C signatures, the δ18O values show a relatively wider range of values from −11.3 to
192 −5.1 ‰ VPDB (−7.0±1.2 ‰ VPDB, n = 92; Table 1). The δ13C values of the investigated carbonates
193 show insignificant correlation with δ18O (R2 = 0.0003, Fig. 5) and most of the values fall within the
194 range documented for best-preserved carbonates of the late Cambrian to early Ordovician (Veizer et al.
195 1999).
196 The C-isotope profile of the East Isthmus Bay section shows two negative excursions (Fig. 3).
197 The lower excursion is broad (~ 2 ‰ VPDB, Fig. 3) and the upper excursion (at 132 m, Fig. 3) is
198 sharper (−2.47 ‰ VPDB).
199
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200 Manganese and strontium
201 The Mn concentrations show an overall gradual decrease upward, with the lowest values in the
202 upper part of the section (Fig. 3). There is little variation between 100 and 300 ppm from the lowermost
203 interval to 120 m on the section, except for a high value of ~ 550 ppm at 44 m, but the Mn
204 concentration decreases generally below 100 ppm for the remainder of the section (Fig. 3; Appendix 1).
205 On the contrary, the Sr concentrations are nearly constant at ~ 200 ppm in the lower to middle
206 intervals, except for a large interrupting peak at 83 m of ~ 500 ppm, but they are consistently higher (~
207 400 ppm) in the upper interval (above the ~ 120 m horizon), except for one peak of ~ 900 ppm at 140
208 m (Fig. 3; Appendix 1). 209 The Sr concentrations are poorly correlatedDraft with their Mn counterparts (R2 = 0.18, Fig 6A) and 210 both elements exhibit insignificant correlation with their δ13C counterparts (R2 = 0.04 and 0.001,
211 respectively; Fig. 6B, C). Similarly, Fe shows an insignificant correlation with the δ13C counterparts
212 (R2 = 0.02, Fig. 6D). Moreover, the Sr and Mn concentrations are also insignificantly correlated with
213 their δ18O counterparts (R2 = 0.06 and 0.05, respectively). In addition, the Mn/Sr values are poorly
214 correlated with their δ13C (R2 = 0.001) and δ18O (R2 = 0.005) counterparts.
215
216 Discussion
217 Evaluation of diagenetic influence
218 The scarcity of well-preservation Paleozoic sediments, that retain their pristine geochemical
219 signatures, makes the evaluation of the petrographic and geochemical preservation of the investigated
220 carbonates a foundation for carbon-isotope chemostratigraphic correlations.
221 Petrographic investigation shows that the sampled carbonates from the studied section have
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222 mainly retained at least their near-primary sedimentary fabrics (Fig. 4A–C), except for minor
223 recrystallization caused by dolomitization in the lower parts of the succession. Although most of the
224 East Isthmus Bay section consists of dolomites (mainly dolomicrites), the reset of δ13C signatures
225 requires dolomitization to occur at a high water-rock interaction ratio, which is always associated with
226 significant recrystallization and significant increase in crystal size (Veizer, 1983; Banner and Hanson,
227 1990). The micritic/ near-micritic grain size (Fig. 4A, B) of investigated carbonates and the
228 preservation of fabric, such as the ooids internal structure (Fig. 4C, radial-concentric ooids, Chow and
229 James, 1987b) argue against significant reset of the δ13C signatures. Also, the investigated carbonates
230 appear dull to non-luminescent. 231 It is well established that, during burialDraft of sediments, the diagenetic fluids react with marine 232 sediments under anoxic conditions through dissolution-reprecipitation processes that result in
233 recrystallization (generally associated with aggrading neomorphism) and changes in the geochemical
234 composition of the diagenetic carbonate phase where Mn and Fe is enriched in the secondary
235 carbonate, but Sr is progressively depleted (Veizer, 1983; Veizer et al. 1999). However, the
236 investigated samples were extracted from mainly carbonate mudstones and dolomicrites that generally
237 retained micritic to near-micritic grain size and their sedimentary fabrics, thus suggesting a high degree
238 of textural preservation, which is also supported by their non- to dull CL . In addition, the Sr, Mn and
239 Fe contents (diagenetic proxies) exhibit insignificant correlation with their δ13C counterparts (R2 =
240 0.04, 0.001, and 0.02, respectively; Fig. 6B–D) suggesting the preservation of at least near-primary
241 carbon-isotope compositions of the investigated carbonates. The relative contents of the Mn and Fe in
242 carbonates have been found to control their luminescence (CL) under a cold cathodoluminoscope
243 (Machel and Burton, 1991). High Mn concentrations in carbonates activate bright CL whereas, on the
244 contrary, the enrichment of Fe quenches the luminescence and results in dull to non-CL (Machel and
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245 Burton, 1991). The dull to non-CL exhibited by the investigated carbonates supports the preservation of
246 primary geochemical signatures, which is consistent with the near-micritic grainsize and fabric
247 retention. However, cathodoluminescence of carbonates has to be taken with caution because high Fe
248 contents can cause non-CL in altered carbonates (see Rush and Chafetz, 1990). Therefore, other
249 techniques are always applied to confirm the preservation of carbonates.
250 Impact of diagenesis on the δ13C composition of carbonates is relatively less than that on the δ18O
251 counterparts, particularly at low water/rock interaction ratio (reflected by near-micritic grain size and
252 restricted recrystallization) because diagenetic fluids do not usually have high amounts of dissolved
13 253 CO2, which may reset the δ C signatures significantly (Veizer, 1983; Banner and Hanson, 1990). 254 Unless the process of dolomitization occursDraft under conditions of significantly high water/rock 255 interaction ratios, the δ13C of the dolomite reflects the nature of the precursor carbonate (Tucker and
256 Wright, 1990). Freshwater diagenesis is another alteration process that delivers 13C-depleted carbon
18 257 from soil CO2 together with O-depleted oxygen from meteoric water (Allan and Matthews, 1982).
258 Such diagenesis is often associated with meteoric cements that have low values of both δ13C and δ18O
259 and generates the apparent covariance of the C- and O-isotopic values (e.g., Allan and Matthews, 1982;
260 Marshall, 1992). The poor correlation between the δ18O and δ13C values of the investigated carbonates
261 (Fig. 5), combined with the falling of most of these values within the range documented for the best-
262 preserved marine carbonates of the Late Cambrian (Fig. 5; Veizer et al. 1999), strongly support the
263 preservation of at least near-primary δ13C signatures of the investigated carbonates.
264
265 Match to the Lawson Cove ASSP section, Utah, USA
266 The systematic sampling of the investigated section allows the reconstruction of a continuous
267 δ13C profile from the Furongian (Stage 10, Upper Cambrian) into the Tremadocian (Lower Ordovician)
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268 in the East Isthmus Bay section (eastern Laurentia, Fig. 3) and the correlation with the coeval strata
269 from the Lawson Cove ASSP section, from Utah, USA (western Laurentia; Miller et al. 2011, 2014).
270 The two sections consist of shallow-marine carbonates deposited on the platform of Laurentia, but the
271 strata in the Lawson Cove section are much less dolomitized and provide a well-established and nearly
272 complete conodont record tied to the δ13C isotope profile (Miller et al. 2015a, 2015b).
273 The δ13C values at East Isthmus Bay are generally ~ 1 ‰ VPDB lower than those of the Lawson
274 Cove counterparts (Table 1; Miller et al. 2015b, their text-figure 14), which is likely attributed to the
275 local paleo-oceanographic conditions such as productivity and/or organic carbon burial. The paleo-
276 geographical different positions of the two sections on Laurentia (relatively shallower depositional 277 setting) of the Lawson Cove section, representedDraft by a thicker section, may have contributed to the 278 higher δ13C values. The δ13C profiles of both sections (East Isthmus Bay and Lawson Cove) exhibit
279 comparable peaks of distinct negative and positive excursions that allow a possible correlation of the
280 conodont-poor section in western Newfoundland (Fig. 7). For consistency, the numbering of C-isotope
281 peaks on the profiles of the correlated sections in this study (Fig. 7) follows the format of Miller et al.
282 (2015b). The lower negative excursion (~ 2 ‰ VPDB), that peaks in the bottom of East Isthmus Bay
283 section, is close to the base of the Eoconodontus conodont Zone (Fig. 7); though this excursion is not
284 complete in the investigated section, as the largest negative excursion (Peak 5) associated with the
285 appearance Eoconodontus notchpeakensis has not been recorded but it can therefore be matched with
286 the top of the HERB Event (Miller et al. 2011, 2014; also known as TOCE – the Top of Cambrian
287 Excursion; Zhu et al. 2006). The upper negative excursion (Fig. 7; Peak 13) can be reliably correlated
288 with the upper subzone of the Cordylodus intermedius Zone (Upper Cambrian). The following sharp
289 increase (Peak 14) appears to match the spike seen in the upper Cordylodus lindstromi Zone of the
290 Lawson Cove, which is supported by the reported presence of Cordylodus lindstromi in the upper beds
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291 in the currently investigated section (Ji and Barnes, 1994). The intermediate but characteristic
292 excursions (Peaks 9 to 11) can be matched respectively with the base and the upper part of the
293 Cordylodus proavus Zone. The overlying positive peak (Peak 12), here named HSS (= Hirsutodontus
294 simplex spike, i.e. following Chen et al. 1995), lies within the lower Hirsutodontus simplex Subzone of
295 the Cordylodus intermedius Zone.
296 This match using the primary δ13C-isotope variations described above greatly improves the
297 relative dating of the non-fossiliferous to fossil-poor Furongian (Stage 10; Upper Cambrian) platform
298 carbonates of the Berry Head Formation (Port au Port Group) in Newfoundland and its lateral
299 equivalents along the eastern Laurentian margin. It also allows for precise match to the coeval slope 300 deposits of the Cow Head Group, where similarDraft carbon-isotope curves based on closely spaced 301 sampling have been documented (Fig. 8; Azmy et al. 2014; Stouge et al. 2017; Azmy 2018).
302 Thus, the HERB and HSS carbon-isotope excursions have been documented and correlated
303 regionally and globally in sections from the Green Point GSSP in Newfoundland, Canada (Miller et al.
304 2014) and Black Mountain (Ripperdan et al. 1992) in Australia (Fig. 8). The large positive excursion
305 (Peak 14, Fig. 7) likely represents the beginning of the Ordovician System as the spike is similar to the
306 spikes in the interval with planktonic graptolites of the Green Point section, western Newfoundland
307 (Fig. 8; see Cooper et al. 2001; Azmy et al. 2014; Stouge et al. 2017). The HERB event has been
308 globally documented by several authors in many sections from different paleocontinents such as China
309 (Chen et al. 1995; Jing et al. 2008; Li et al. 2017), Argentina (Buggish et al. 2003), Australia
310 (Ripperdan et al. 1992).
311
312
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313 Conclusions
314 Samples were collected at narrow intervals from the near-micritic carbonates of the East Isthmus
315 Bay section of Berry Head and Watts Bight formations in western Newfoundland, Canada.
316 Petrographic examination and geochemical analyses suggest preservation of at least near-primary δ13C
317 signatures. The δ13C profile shows two main negative excursions, a broad one in the lower section
318 (Furongian, Upper Cambrian) and a sharper counterpart in the upper part of the section (uppermost
319 Cambrian).
320 The main negative excursions and the bracketed minor peaks in between can be correlated with
321 counterparts on the well-established equivalent profile of the Lawson Cove ASSP section, Utah, USA. 322 The match suggests that the large lower negativeDraft excursion seen in the lower East Isthmus Bay section 323 can be correlated with the Eoconodontus notchpeakensis Subzone of the Eoconodontus Zone
324 (Furongian, Stage 10, Upper Cambrian) in the Lawson Cove section and the large upper negative
325 excursion can be correlated with the top of the Cordylodus intermedius Zone (top Cambrian) in the
326 Lawson Cove section.
327 The large positive excursion (Peak 14) at the top of the East Isthmus Bay section probably
328 corresponds to the largest positive excursion recorded in the upper subzone of the Cordylodus
329 lindstromi Zone of the Lawson Cove (Miller et al. 2015b).
330 The positive and negative peaks between the two major negative excursions on the East Isthmus
331 Bay C-isotope profile can be matched with equivalent counterparts in the Lawson Cove profile
332 allowing for a secure match with the conodont biozonation scheme between the Eoconodontus
333 notchpeakensis Subzone of the Eoconodontus Zone and Iapetognathus Zone.
334 Local variations in paleo-oceanographic conditions likely resulted in a slight decrease (~ 1 ‰
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335 VPDB) in the δ13C values at East Isthmus Bay relative to those of their Lawson Cove counterparts.
336 The current study provides a continuous carbon-isotope profile from the top of Port au Port Group
337 extending into the base of the St. George Group that allows better regional correlation for the sections
338 with poor biostratigraphic controls.
339
340 Acknowledgements
341 The authors wish to thank the reviewers for their constructive comments. Also, the efforts of Drs. Ali
342 Polat (editor) and Ihasan Al-Aasam (associate editor) are greatly appreciated. This work was supported
343 by funding (to Karem Azmy) from Petroleum Exploration Enhancement Program (PEEP) and (to 344 Svend Stouge) the Carlsberg Foundation, Denmark.Draft 345
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546 547 Veizer, J., Ala, D., Azmy, K., Bruckschen,Draft P., Bruhn, F., Buhl, D., Carden, G., Diener, A., Ebneth, S., 548 Goddris, Y., Jasper, T., Korte, C., Pawellek, F., Podlaha, O., and Strauss, H., 1999. 87Sr/86Sr, δ18O and
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557
558
559
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560
561
562 Figure captions
563 Fig. 1. (A) Map of western Newfoundland, Canada, showing the location of the investigated section,
564 and (B) Localities where the boundary between the Berry Head and Watts Bight formations is exposed
565 on the Port au Port Peninsula (Modified from Ji and Barnes, 1994). Red arrow points at the study area
566 (EI, known as East Isthmus Bay section). (C) Coastline where the East Isthmus Bay section is exposed
567 (Coordinates for the base of section: 48° 33’ 05.6” N; 58° 42’ 03.1” W; and top of section: 48° 33’
568 09.2” N; 58° 42’ 38.0” W).
569 Draft
570 Fig. 2. Stratigraphic chart spanning the East Isthmus Bay section. Highlighted area shows the
571 approximate interval covered by the investigated section.
572
573 Fig. 3. Stratigraphic framework and detailed measured section with the positions of investigated
574 samples along with the carbon-isotope, Mn and Sr profiles of the studied Upper Cambrian to lowermost
575 Ordovician section East of Isthmus Bay, western Newfoundland. Highlighted area shows the top of the
576 HERB Event. The dotted line marks the mean value.
577
578 Fig. 4. Photomicrographs of various petrographic features of the East Isthmus Bay section showing (A)
579 lime mudstone (Sample EI-139, PPL), (B) laminated micrite limestone (Sample EI-77, XPL), and (C)
580 radial-concentric ooids (Sample EI-132, XPL) in oolitic grainstone.
581
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582 Fig. 5. Scatter plot showing correlation of the δ13C with their δ18O counterparts. The square represents
583 the composition documented for the best-preserved carbonates from the Late Cambrian (Veizer et al.
584 1999).
585
586 Fig. 6. Scatter plot showing correlation of (a) Mn with Sr, and (b) Sr, (c) Mn, and (d) Fe with their δ13C
587 counterparts for the investigated samples.
588
589 Fig. 7. The correlation of the δ13C profiles of the East Isthmus Bay section, western Newfoundland,
590 Canada, with that of Lawson Cove, Utah, USA (Miller et al. 2015b). Conodont biostratigraphy in Utah 591 is from Miller et al. (2015b). The constructionDraft of the conodont biostratigraphy at East Isthmus Bay is 592 based on the C-isotope correlation. Detail in text. (HSS = Hirsutodontus Simplex Spike, a characteristic
593 positive excursion seen in the Hirsutodontus Simplex conodont Subzone; after Chen et al. 1995).
594
595 Fig. 8. The carbon-isotope chemostratigraphic correlations of the HERB Event (latest Cambrian) in
596 sections from eastern Laurentia (East Isthmus Bay and Green Point, Azmy et al. 2014; Miller et al.
597 2014), western Laurentia (Lawson Cove, Miller et al. 2015b) and Australia (Black Mountain,
598 Ripperdan et al. 1992).
599
600
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56o Legend A Labrador Start of sampled path...... + Sampled Area...... Cliff...... Beach...... Québec N Road...... 52o Road Number...... 460 Newfoundland Hare Bay Gulf Strait of Belle Isle of St. Lawrence
+ + +
+ + B + + Port au Port + +
+ + o Peninsula + 50 + + Atlantic Ocean Draft + +
+ + +
+ + + +
Gulf of St. Lawrence + + EI +
+ Long+ Range massif + Carboniferous cover + + + Silurian-Devonian granitic and sedimentary rocks Isthmus Bay Fault Mafic-silicic igneous rocks Ophiolite complex N 5 km Bay of Islands Sedimentary rocks/mélange ALLOCHTHONS COW HEAD GROUP C 460 Port au Port Peninsula Transported continental margin slope/rise rocks + + + AUTOCHTHONOUS / PARAUTOCHTHONOUS + + Silici-clastic rocks + + N Isthmus Bay + + Shelf carbonate rocks o + + 46 + Shelf clastic rocks
Metasedimentary rocks East Isthmus Bay 100 m + + Grenville basement (crystalline rocks) Cabot fault
20 km 58o 56o
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Long Point Group Mainland Sandstone
Table
Head Bight Watts Watts Form. MIDDLE Group L. ORD. Tremadoc ORDOVICIAN
St. George Group LOWER Port au
Port Trempealeauan
UPP. Draft Group M. Berry Head Formation Labrador CAMBRIAN Group Man O’ LOW. War Є
Franconian Member P
St. George Felix Unconformity Member UPPER CAMBRIAN Big Cove Member Petit Jardin Formation Dresbachian Campbells Member
Cape Ann Member Є M Point Form. March
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Algal Mats Laminations Dolostone Algal Mound Lens Dolomitic Limestone Bioturbation (Minimal to Intense) Ooids Limestone Black Chert Planar Bedding Brecciated Ripple Marks Dolomitic Siltstone Concretion sc Scoured Surface Conglomerate sh si Cross bedding Stromatolite mound Breccia Dolostone Series
Group Tepee Structure Lithology Desiccation Cracks Chert Dolomitic Limestone System m w/g c
Formation Flaser Bedding Thrombolite mound Thickness (m) Shale Limestone Intraclasts Wavy Bedding Gap/ Break in Succession EI-40 Sample ID and Position Collected
190 13 180 d C ‰ (VPDB) Sr (ppm)
-3 -2 -1 0 1 0 1000 170 St. George Watts Bight Watts
EI-161 Lower 160 EI-159 EI-157a EI-156 EI-154 ORDOVICIAN EI-152 150 EI-150 EI-148 EI-146 EI-144a EI-143 140 EI-139 EI-136 EI-134 EI-132 130 EI-129b EI-129
EI-127 EI-125 Draft EI-123 120 EI-121 EI-119
EI-114 EI-112 110 EI-110
Breccia EI-108 EI-105 EI-103 100 EI-101 EI-99 EI-97 Furongian sc EI-95 Berry Head Port au EI-93
90 Dolosiltstone EI-90 EI-88 EI-85 EI-80 EI-77 C A M B R I A N A M B R I A C 80 Conglomerate EI-74 EI-72 EI-70 EI-68 Conglomerate EI-66 70 EI-64 EI-62 EI-60 EI-59 EI-58 EI-57 60 EI-56 EI-54 EI-55 Conglomerate EI-52 EI-53 Dolosiltstone sc EI-51 Conglomerate EI-50 EI-49
Breccia EI-48 50 EI-46 EI-43 EI-44 EI-41 EI-42 EI-40 Breccia EI-39
Breccia 40 Breccia EI-36 EI-38 EI-34 EI-35 EI-33 EI-31 EI-29 30 EI-28 EI-26 EI-27 EI-24 EI-23 EI-22 Breccia EI-21 EI-19 EI-20
20 Breccia EI-18 EI-16
Breccia EI-14 EI-12 EI-10 10 EI-9 EI-7 EI-6 EI-5 HERB Event EI-3 0 EI-1 0 600 -10 https://mc06.manuscriptcentral.com/cjes-pubs Mn (ppm) Page 31 of 42 Canadian Journal of Earth Sciences A
250 µm
B
Draft
250 µm
C
250 µm https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 32 of 42
Table 1. Summary of geochemical statistics.
13 18 δ C (‰ δ O (‰ CaCO3 MgCO3 Fe Mn Sr VPDB) VPDB) (%) (%) (ppm) (ppm) (ppm) n 92 92 32 32 32 32 32 STDV 0.5 1.2 16.9 16.9 1907 121 184 Median -1.2 -6.8 63.5 36.5 1696 163 149 Average -1.2 -7.0 72.3 27.7 2155 199 214 Max 0.2 -5.1 99.4 41.8 7182 565 918 Min -2.5 -11.3 58.2 0.6 180 40 37
Draft
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Appendix 1
Elemental and isotopic geochemical compositions of the East Isthmus Bay carbonates. 13 18 Sample ID Distance δ C δ O CaCO3 MgCaO3 Sr Mn Fe # (m) (‰ VPDB) (‰ VPDB) % % (ppm) (ppm) (ppm) EI-161 160.0 -0.5 -8.2 99.4 0.6 278 61 190 EI-159 158.0 -1.6 -7.8 99.2 0.8 399 55 371 EI-157a 156.5 -1.0 -8.4 EI-156 155.0 -0.8 -8.2 EI-154 153.0 -0.3 -6.0 EI-152 151.0 0.2 -8.2 99.1 0.9 322 117 468 EI-150 149.0 -0.7 -8.2 99.4 0.6 314 40 270 EI-148 147.0 -0.2 -6.9 EI-146 145.0 -0.1 -8.1 94.9 5.1 358 53 180 EI-144a 143.5 -0.7 -8.1 EI-143 142.0 -0.7 -6.7 EI-139 138.0 -1.9 -8.1 98.7 1.3 918 96 2184 EI-136 135.0 -1.4 -6.0 63.1 36.9 233 149 7182 EI-134 133.0 -1.8 -7.8 EI-132 131.0 -2.5 -7.8 99.1 0.9 427 55 264 EI-129b 128.0 -0.5 -6.9 Draft66.1 33.9 158 162 3386 EI-129 127.0 -0.7 -7.6 EI-127 125.0 -0.8 -9.8 EI-125 123.5 -1.4 -6.1 EI-123 121.0 -1.8 -7.7 65.4 34.6 111 262 4638 EI-121 119.0 -1.4 -10.3 EI-119 117.0 -1.4 -7.3 EI-114 112.0 -1.0 -5.5 58.5 41.5 69 116 932 EI-112 110.0 -1.3 -5.9 EI-110 108.0 -1.3 -7.6 60.3 39.7 77 291 1854 EI-108 106.0 -1.3 -6.7 EI-105 103.0 -1.0 -5.1 59.9 40.1 91 164 1790 EI-103 101.0 -1.2 -5.8 EI-101 99.0 -1.1 -8.0 EI-99 97.0 -1.6 -8.1 60.7 39.3 87 158 1362 EI-97 95.0 -1.3 -5.1 EI-95 93.0 -1.5 -6.1 EI-93 91.0 -1.4 -6.4 EI-90 88.0 -1.4 -6.3 EI-88 86.0 -1.6 -6.4 EI-85 83.0 -2.1 -7.7 98.9 1.1 535 97 218 EI-80 82.0 -1.2 -7.4 98.2 1.8 493 175 248 EI-77 81.0 -1.5 -8.0 EI-74 79.0 -1.6 -5.7 EI-72 77.0 -2.1 -6.2 59.3 40.7 96 164 1096 EI-70 75.0 -1.6 -5.8 EI-68 73.0 -1.8 -7.4 EI-66 71.0 -1.2 -9.8 EI-64 69.0 -1.1 https://mc06.manuscriptcentral.com/cjes-pubs-6.0 60.3 39.7 124 146 644 Canadian Journal of Earth Sciences Page 34 of 42
EI-62 67.0 -1.1 -9.1
Draft
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EI-60 65.0 -1.0 -5.5 EI-59 63.0 -1.0 -5.1 EI-58 62.0 -0.8 -6.7 64.7 35.3 121 306 1831 EI-57 60.5 -0.9 -7.1 EI-56 59.5 -0.9 -6.8 EI-55 58.5 -1.2 -8.0 EI-54 57.5 -1.8 -5.8 64.1 35.9 202 207 1509 EI-53 56.0 -1.5 -6.7 EI-52 55.5 -1.7 -9.5 EI-51 54.5 -1.6 -6.3 EI-50 53.0 -1.4 -5.6 EI-49 52.5 -1.2 -6.6 67.4 32.6 194 288 2013 EI-48 50.0 -1.2 -7.3 EI-46 49.0 -1.5 -6.6 EI-44 47.5 -1.5 -6.9 EI-43 47.0 -1.3 -6.8 EI-42 46.0 -1.0 -7.4 EI-41 45.0 -1.5 -11.3 59.7 40.3 37 139 1248 EI-40 44.0 -0.7 -7.6 63.9 36.1 81 565 2561 EI-39 42.0 -0.8 -7.2 EI-38 40.0 -1.3 -6.7 Draft EI-36 39.0 -0.8 -7.0 EI-35 37.5 -1.7 -6.8 69.5 30.5 184 374 4622 EI-34 37.0 -1.0 -8.2 EI-33 35.5 -0.4 -6.6 63.1 36.9 152 340 2715 EI-31 35.0 -1.1 -8.9 59.0 41.0 75 279 1499 EI-29 33.0 -0.6 -7.8 EI-28 30.5 -0.7 -6.8 EI-27 29.0 -0.5 -5.6 60.1 39.9 189 368 2862 EI-26 28.5 -1.1 -5.8 EI-24 27.5 -1.1 -5.1 58.2 41.8 84 198 1603 EI-23 26.0 -0.9 -6.3 EI-22 25.0 -0.8 -5.8 EI-21 23.5 -0.6 -7.8 59.9 40.1 88 123 2397 EI-20 23.0 -0.8 -6.8 EI-19 22.0 -1.2 -7.0 EI-18 20.0 -1.1 -6.4 EI-16 18.5 -1.0 -5.3 EI-14 17.0 -1.6 -6.8 62.6 37.4 131 314 5897 EI-12 15.0 -1.0 -5.9 EI-10 12.5 -1.1 -5.2 EI-9 9.5 -0.7 -5.6 59.2 40.8 91 157 4872 EI-7 8.0 -1.3 -6.3 EI-6 6.0 -1.3 -5.4 EI-5 4.0 -1.6 -6.1 62.4 37.6 146 356 6042 EI-3 2.0 -1.5 -5.5 EI-1 0.5 -1.5 -5.6
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2 R2 = 0.0003
1
δ18O ‰ VPDB 0 -12 -10 -8 Draft-6 -4 -2 0 C ‰ VPDB C
-1 13 δ
-2
-3
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600 R2 = 0.18
500
400
300 Draft Mn (ppm) Mn 200
100
0 0 100 200 300 400 500 600 700 800 900 1000 Sr (ppm)
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0.5
Sr (ppm) 0.0 0 200 400 600 800 1000
2 -0.5 R = 0.04
-1.0 Draft ‰ VPDB
C -1.5 13 δ
-2.0
-2.5
-3.0
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0.5
Mn (ppm) 0.0 0 100 200 300 400 500 600
2 -0.5 R = 0.001
-1.0 Draft
‰ VPDB -1.5 C 13 δ -2.0
-2.5
-3.0
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Draft Canadian Journal of Earth Sciences https://mc06.manuscriptcentral.com/cjes-pubs 0 1000 2000 3000 4000 5000 6000 7000 8000
0.5 0.0
-0.5 -1.0 -1.5 -2.0 -2.5 -3.0
C C „ VPDB „ / 13 Page 41 of 42 Canadian Journal of Earth Sciences Laurentia east Laurentia west (East Isthmus Bay, (Lawson Cove, Utah)
Newfoundland) Conodont Zones System Group Thickness (m) Formation Thickness (m) (15) 190 200 Rossodus manitouensis Zone 180
170 Cordylodus angulatus St. George Watts Bight Watts ? ? ? 175 Zone 160 ORDOVICIAN (14) Iapetognathus Zone 150 (14) Cordylodus lindstromi Zone 140 (13) 150 (13) Clavohamulus Z. 130 hintzei Subzone
120 Draft 125 Hirsutodontus simplex 110 HSS (12)
Subzone Cordylodus intermedius 100 (12) HSS (11) Clavohamulus elongatus Sz.
Berry Head 90 100 Port au
Fryxellodontus Zone 80 (11) inorantus Subzone C A M B R I A N A M B R I A C 70 (10)
75 Hirsutodontus hirsutus Cordylodus (10) proavus 60 (9) Subzone (8) 50 (9) (8) 40 50 Cambrooistodus Zone minutus Subzone 30 HERB (7) HERB Event 20 (7) Event 25 10 (6) (6) Eoconodontus notchpeakensis Subzone
(5) Eoconodontus 0 ? ? ? -10 0 Proconodontus muelleri Zone -2 -1 0 -2 -1 0 1
13 13 δ Ccarb (‰ VPDB) δ Ccarb (‰ VPDB) https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 42 of 42
Eastern Laurentia Western Laurentia Gondwana Eastern Laurentia East Isthmus Bay, Newfoundland Lawson Cove, Utah, USA Black Mountain, Austrailia Green Point, Newfoundland (this study) (Miller et al. 2015b) (Ripperdan et al. 1992) (Azmy et al. 2014; Miller et al. 2014)
HSS 10 m HSS 10 m Draft100 m 10 m
HSS HSS
Top of HERB HERB HERB Event Event HERB Event Event
-3 -2 -1 0 1 -2 -1 0 1 2 -3 -2 -1 0 1 -6 -5 -4 -3 -2 -1 0 1 2 13 13 13 13 δ Ccarb (‰ VPDB) δ Ccarb (‰ VPDB) δ Ccarb (‰ VPDB) δ Ccarb (‰ VPDB)
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