Carbonate Outliers in the Northern Ottawa-Bonnechere Graben

Canadian Journal of Earth Sciences

Upper Ordovician (Sandbian-Katian) carbonate outliers in the northern Ottawa-Bonnechere graben (central Canada): records of transgressions and sedimentation patterns in the Laurentian platform interior

Journal: Canadian Journal of Earth Sciences

Manuscript ID cjes-2020-0065.R1

Manuscript Type: Article

Date Submitted by the 02-Jun-2020 Author: Complete List of Authors: Kang, He; DraftOttawa-Carleton Geoscience Centre; Carleton University, Department of Earth Sciences Dix, George; Ottawa-Carleton Geoscience Centre; Carleton University, Department of Earth Sciences

sedimentary outliers, Canadian Shield, depositional systems, Sandbian, Keyword: Katian

Is the invited manuscript for consideration in a Special Not applicable (regular submission) Issue? :

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1 Upper Ordovician (Sandbian-Katian) carbonate outliers in the northern 2 Ottawa-Bonnechere graben (central Canada): records of transgressions and 3 sedimentation patterns in the Laurentian platform interior 4 5 6 7 8 9 He Kang1 and George R. Dix1 10 11 1Ottawa-Carleton Geoscience Centre, and Department of Earth Sciences, Carleton University, 12 Ottawa, Ontario, K1S 5B6, Canada 13 14 15 16 17 Corresponding author: George R. Dix, Department of Earth Sciences, Carleton University, 18 Ottawa, ON K1S 5B6, Canada, +16135202600, [email protected] 19 20 21 Draft 22 23 24 25 26 27 28

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29 Abstract

30 Small Ordovician sedimentary outliers, including Brent Crater, within the northern Ottawa–

31 Bonnechere graben are remnants of a once expansive Upper Ordovician sedimentary cover

32 extending across the southern Canadian Shield. Facies successions along with updated

33 macrofossil and conodont biostratigraphy, and isotope (C, O, Sr) chemostratigraphy provide

34 additional insights into the terrestrial-to-marine transformation, carbonate-platform development,

35 and oceanographic communication across the southern Laurentian platform. Four of the outliers

36 document Sandbian shoreline-to-nearshore deposition: near Deux Rivières, Manitou Islands, the

37 upper part of the Brent Crater sedimentary fill, and at nearby Cedar Lake. Marine transgression

38 initially reworked local fine-grained to boulder-rich regolith within high-energy shoreface

39 siliciclastic environments that gave wayDraft to low- to high-energy inner carbonate-ramp setting.

40 Continued transgression resulted in more offshore rhythmic and diverse lithofacies successions

41 defining mixed heterozoan, photozoan, and microbial productivity and marine isotope (C, Sr)

42 signatures, but δ13C excursions that suggest periods of greater mixing of terrestrial and marine

43 carbon reservoirs. Lower Katian strata are preserved near Lake Nipissing and characterize

44 deepening from high-energy ooid-heterozoan skeletal shoals to deeper water mid-ramp

45 siliciclastics and skeletal carbonates, host to a Cruziana ichnofacies. An upsection decline in δ13C

46 values through this succession may identify deposition during the post-peak decline of the global

47 Guttenberg δ13C excursion. This lithic succession fits well with contemporary expansion of

48 heterozoan skeletal lithofacies across the Laurentian platform yet the presence of ooids identifies

49 prevailing warm waters within the platform interior during early stages of transgression.

50 Keywords: sedimentary outliers, Canadian Shield, depositional systems, Sandbian, Katian 51 52

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53 Introduction

54 Sedimentary outliers occur along the southeastern Canadian Shield within two regionally

55 intersecting cratonic fault systems, the northern Ottawa-Bonnechere (OBG) and Timiskaming

56 (TG) grabens (Fig. 1A). Fossil assemblages from outliers in the northern OBG, including the

57 upper portion of the Brent Crater fill, identify a Late Ordovician (Sandbian) age (Colquhoun

58 1958; Lozej and Beales 1975a; Grahn and Ormö 1995) whereas the Timiskaming outlier consists

59 of an Upper Ordovician (Sandbian?-Katian) through Middle Silurian succession (Bolton and

60 Copeland 1972). The outliers are erosional remnants of a once expansive Ordovician through

61 Devonian sedimentary cover across the Laurentian interior (Patchett et al. 2004), and Silurian

62 sea-level records from the Timiskaming outlier demonstrate local sedimentary response to

63 regional (cross-platform) and global base-levelDraft changes (Colville and Johnson 1982).

64 Outliers of the northern OBG provide the opportunity to characterize the marine

65 transformation of a terrestrial Laurentian interior. Integration of outlier lithostratigraphy, facies

66 stacking, macro- and microfossil biostratigraphy, and isotope (87Sr/86Sr, δ13C) profiles allows for

67 comparison with contemporary lithic successions south of the Canadian Shield in eastern North

68 America (Brookfield 1988; Holland and Patzkowsky 1996; Grimwood et al. 1999; Salad Hersi

69 and Dix 1999; El Gadi 2001; Bergström et al. 2010; Quinton et al. 2018; Oruche et al. 2018,

70 2019), and evaluation whether there was regional oceanographic communication versus

71 environmental gradients during successive (Sandbian, early Katian) marine transgressions.

73 Geological setting

74 The Ottawa-Bonnechere graben is an intracratonic fault system extending from the Canadian

75 Shield into the confines of the Ottawa Embayment (Fig. 1A). An axial rift valley is locally

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76 developed (Fig. 1B; Kay 1942), and Neoproterozoic and Early Cambrian syenite plutons along

77 the graben axis characterize an initial history of abortive rifting contemporary with breakup of

78 Rodinia (McCausland et al. 2007). Net Paleozoic burial, then Mesozoic graben inversion and

79 Cenozoic erosion resulted in periods of structural reactivation along the graben axis (see Oruche

80 et al. 2018). Stratigraphy of the OBG outliers is contemporary with development of a regional

81 foreland along southern Laurentia in response to Middle Ordovician through Early Silurian

82 Taconic orogenesis (Ettensohn and Brett 2002). Differences in stratigraphic completeness of the

83 foreland depositional record, the Tippecanoe I Megasequence (Fig. 1C), along the southern

84 Canadian Shield (Fig. 1C) reflects differential uplift among basins driving non-deposition and-or

85 erosion. Regionally, the foreland succession documents net deepening of a mostly carbonate-

86 platform succession, replaced through drowningDraft by a deep-water euxinic basin (Billings and

87 Blue Mountain formations; Fig. 1C). Subsequent north-directed transport of orogen-derived

88 siliciclastics resulted in basin over-fill culminating in the paralic Queenston Formation (Fig. 1C;

89 Brogly et al. 1998). This unit grades northward into platform carbonate in the Timiskaming

90 Graben (Fig. 1C).

92 Methodology

93 Facies characterization and lithostratigraphy are based on outcrop and drill-core descriptions,

94 with facies confirmation through thin-section petrography. Facies were defined on the basis of

95 standard sedimentary facies models (James and Dalrymple 2010; Flügel 2010) and sources

96 related specifically to Upper Ordovician sedimentology of eastern North America (see tables 1

97 and 2). Updated taxonomy of macrofossil lists and details of new fossil occurrences (including

98 conodonts) are provided in an open-access data repository, Kang and Dix (2020):

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99 https://doi.org/10.5683/SP2/IAYKTS. Powdered samples for 13C, 18O, and 87Sr/86Sr analyses

100 were acquired by micro-drilling of lime mudstone and dolomudstone, and fine- to coarsely

101 crystalline dolostone. δ13C and δ18O values were determined at the Queen's Facility for Isotope

102 Research (Kingston, ON), with additional analysis at the Ján Veizer Stable Isotope Laboratory

103 (Ottawa, ON). The results are reported using the delta (δ) notation in permil (‰) relative to

104 Vienna Pee Dee Belemnite (VPDB). Analytical precision (2 sigma) is ± 0.2‰ (Queen’s) and ±

105 0.1‰ (Ján Veizer). Duplicates verified inter-lab consistency. 87Sr/86Sr ratios were determined at

106 the Isotope Geochemistry & Geochronology Research Centre (Ottawa, ON). Analytical precision

107 (2 sigma) is ± 0.0000001. Further details of isotope analytical methodology, standards, and

108 datasets are provided by Kang and Dix (2020).

109 Draft

110 Facies Successions

111 Deux Rivières Outlier

112 This outlier is exposed along the north shore of the Ottawa River, northwest of Deux Rivières

113 (Fig. 2A). Contact with crystalline basement is not exposed. The section is summarized in Fig.

114 3A. Units 1 to 5 are exposed along a prominent escarpment (Fig. 4A) that displays a gentle,

115 southeasterly shallowing, dip over ~500 m to the waterline. Unit 6 occurs above a covered

116 interval (Fig. 3A) and is set back from the shoreline. The facies succession is interpreted as

117 stacked shallowing and deepening patterns (Fig. 3A).

118 Unit 1 contains a conformable transition from sandy fossiliferous dolostone to thin-bedded

119 skeletal-bearing lime mudstone and packstone (Fig. 4B). The sandstone contains large (1 cm

120 diameter) Skolithos and differentially blackened (or pyritic) fragments of trilobites, brachiopods,

121 and ostracodes. The limestone contains a more diverse benthic fossil suite, including crinoid

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122 ossicles, cryptostomid bryozoans, and the calcimicrobe Hedstroemia and calcareous alga

123 Mastopora (Fig. 3A). Siliciclastics reappear as a massive thick unfossiliferous bed (Unit 2) of

124 feldspathic arenite cemented by chlorite, but its contacts are covered (Fig. 3A).

125 The remaining escarpment section consists of fossiliferous limestone comprising Units 3 and

126 5 (Fig. 3A), and a hard crystalline dolostone (Unit 4) separating the limestones (Fig. 4C). The

127 limestone succession contains three intervals (units 3a-b, 3c-d, and 5a-b) that describe repeated

128 upsection changes from basal sandy or silty skeletal-bearing muddy limestone or, in the case of

129 Unit 3c-d, limestone interbedded with calcareous shale, into crinoid- and ooid-bearing skeletal

130 grainstone. The muddier limestone of Unit 3a contains fragmented colonies of the calcareous

131 worm tubes Tymbochoos sinclairi Okulitch whereas a more diverse fossil assemblage appears in

132 the coarser-textured limestone facies of Draftthis and younger limestone successions. In Unit 5,

133 packstone with calcareous alga Vermiporella canadensis Horne and Johnson is succeeded

134 upsection by grainstone with shrubs of Hedstroemia sp. and ooids (Fig. 4D). The crystalline

135 dolostone (Unit 4) does not show any obvious depositional fabric except in the lower 40 cm

136 where there are several upright recrystallized colonies of domal (10-20 cm in diameter)

137 stromatoporoids and Tetradium fibratum?.

138 Stepped back from the escarpment, Unit 6 contains nodular skeletal and oncoid-bearing

139 packstone and grainstone (Fig. 4E). Fragments of Vermiporella sp. and Hedstroemia sp. are

140 present. Oncoids display bored skeletal cores coated by Girvanella filaments (Fig. 4E).

141

142 Brent Crater

143 Brent Crater is located southwest of Deux Rivières (Fig. 2A) and is a small-diameter (~3 km)

144 simple impact crater in Mesoproterozoic gneiss (Fig. 2B; Grieve 2006). The age of impact has

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145 been interpreted as being prior to Late Ordovician (Turinian) transgression (Lozej and Beales

146 1975a). The cross-sectional geometry of the pre-Quaternary basin-fill is an open syncline (Fig. 5

147 inset). This study examined core 1-59 from the crater centre (Fig. 2B) that recovered ~210 m of

148 sedimentary rock above thermally altered fall-back breccia and melt rock (Fig. 5 inset). The

149 reader is also directed to core descriptions of Lozej and Beales (1975a, b).

150 Units 1 through 3 of this study (Fig. 5A) comprise a lower stratigraphic division replete with

151 numerous small-scale folds and faults that define synsedimentary deformation. These features

152 are in contrast with sub-horizontal satin spar (gypsum) veins (Fig. 6A) that document post-

153 lithification fracturing. Unit 1 defines an overall fining-upward succession (Fig. 5A) of inter-

154 laminated and thinly interbedded sandstone and siltstone. Sedimentary structures include sand-

155 clay laminae couplets, asymmetric (current)Draft cross-stratification, massive sand drapes, and normal

156 grading. Unit 2 consists of a lower interval of dolomudstone breccia with varying abundance of

157 siltstone matrix (Fig. 6B). This occurs intercalated with in situ thin-bedded dolomudstone of

158 similar composition. The breccia is succeeded conformably by a succession of lower

159 siliciclastics similar to Unit 1b grading into an upper division of sandy thinly laminated

160 dolomudstone similar to the lower part of the unit. Unit 3 displays an apparent rhythmic

161 (conformable to abrupt) interstratification among thin-bedded to thickly laminated calcareous

162 siltstone, minor sandstone, and very silty lime mudstone (Fig. 6C). This interpretation differs

163 from Lozej and Beales’ (1975a) description (see their Fig. 5) of a mostly sub-arkosic sandstone

164 over this same interval, whereas Lozej and Beales (1975b) reported mostly siltstone and minor

165 sandstone.

166 The upper division of core I-59 documents abrupt establishment of a shallow-water

167 carbonate-platform succession interrupted by siliciclastic intervals of varying thicknesses (Fig.

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168 5A, B). Unit 4 is mostly lime mudstone, its lower ~ 5 m composed of microbial (stromatolite)

169 mounds and intermound lime mudstone. The rest of the unit is fossiliferous lime mudstone with

170 Tymbochoos sinclairi, gastropods, rare trilobites, chitinozoans, and conodonts (Fig. 5A; Grahn

171 and Ormö 1995). Small vertical burrows and lingulid brachiopod valves occur along an abrupt

172 upper contact. Unit 5 consists of two thick siliciclastic units bounding very fossiliferous

173 carbonate strata (Fig. 5A). The lower siliciclastic division is a thick-bedded green and red

174 feldspathic wacke, with rare local interbeds of argillaceous to sandy lime mudstone. One of these

175 beds shows downward tapering fractures filled with gravel-bearing siltstone host to pebble-sized

176 limestone clasts some with diffuse margins (Fig. 6D). The fossiliferous carbonate unit (Fig. 5A)

177 coarsens upward from sandy (< 10%) carbonate mudstone to skeletal-rich packstone and

178 grainstone (Fig. 5A). The upper siliciclasticDraft division is interbedded fossiliferous feldspathic

179 arenite and siltstone (Fig. 5A).

180 Unit 6 illustrates the greatest abundance of fossils as well as diversity of fossil and allochem

181 types and resulting carbonate facies (Fig. 5B). Vertical arrangement of carbonate, sandy

182 carbonate, and quartz arenite facies form an apparent rhythmic succession of four depositional

183 transgressive-regressive successions, C1-C4 (Fig. 5B). The lower part of a fifth division, C5,

184 forms the upper few metres of the core and represents a distinct facies association of burrowed

185 clayey skeletal-ooid-bearing packstone and wackestone with local hardground development (Fig.

186 6E).

187

188 Cedar Lake

189 This is a very small-area outlier (Loc. 3) along the north shore of Cedar Lake, ~6 km south of

190 Brent Crater (Fig. 2B). Two measured sections are separated by ~20 m and illustrate stratal onlap

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191 across a metre-scale paleotopographic high of Precambrian gneiss (Fig. 7A), although the

192 Ordovician-Precambrian nonconformity remains covered (Fig. 7B). Section A is positioned

193 within a paleotopographic low (Fig. 7A). Here, a basal ferruginous feldspathic wacke (Fig. 7C) is

194 succeeded abruptly by feldspathic arenite with dolomite cement. The arenite is traced to Section

195 B (Fig. 7A). At Section A, the conformable Unit 2 (Fig., 7D) displays wavy bedding associated

196 with a repetitive cm-scale depositional couplet: a basal thin coarsely crystalline dolostone

197 containing allochem ghosts of crinoid ossicles, ostracodes, and bivalve or brachiopod shells (Fig.

198 7E) overlain gradationally to abruptly by sandy dolomudstone. Similar sandy dolostone

199 comprises Unit 2 at Section B (Fig. 7A). Dolomudstone makes up the remainder (Unit 3) of

200 Section A (Fig. 7A).

201 Draft

202 Manitou Islands

203 The islands occur in eastern Lake Nipissing (Fig. 2A) and form an elliptical cluster coincident

204 with an underlying high-level intrusion of syenite and altered alkalic rocks (Fig. 2C) of

205 Neoproterozoic (570-580 Ma) age (Lumbers 1971; McCausland et al. 2007). The thickest

206 exposed sedimentary section, including exposure of the Ordovician-Precambrian nonconformity,

207 is on Great Manitou Island (Loc. 4). The nonconformity is represented by irregular (metre-scale),

208 but generally rounded, paleotopography; there is no evidence of surface weathering.

209 The sedimentary section contains an overall upsection change from basal very coarse

210 siliciclastics to muddy carbonate facies (Fig. 8). Unit 1 is an oligomictic framework-supported

211 boulder breccia (Fig. 9A) with clast lithologies of local basement lithology. The matrix is a

212 granule to pebble-bearing feldspathic arenite host to locally preserved dolomitized bivalve shells

213 (Fig. 9B) and fragmented cryptostomid bryozoans. Bivalve shells are smooth, narrow, and

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214 elongate (2-3 cm), but of an indeterminate genus. This basal facies grades upward into an

215 oligomictic matrix-support conglomerate (Fig. 9C) with small, often elongate, pebble (< 2 cm)-

216 sized clasts of basement-derived lithologies. Long axes of clasts are oriented parallel to bedding.

217 The matrix is a sandy crystalline dolostone with poorly sorted and rounded to subrounded quartz.

218 Unit 2 is a sandy to syenite/gneiss pebble-bearing finely crystalline dolostone illustrating

219 continued decrease in abundance of siliciclastics matched by greater abundance of carbonate.

220 However, individual beds (< 20 cm thick) display normal grading of syenite clasts, 1 to 5 cm in

221 diameter. Whole, large (< 3 cm) dolomitized bivalve shells are present but of indeterminate

222 genus. This unit contains the highest stratigraphic occurrence of basement-derived clasts.

223 Unit 3 is a fine- to medium-crystalline dolostone with locally abundant intercrystalline

224 porosity. There are rare interbeds of dolomitizedDraft crinoid- and bryozoan-bearing packstone in its

225 lower part whereas the upper unit contains no identifiable depositional features. This unit is

226 abruptly overlain by a carbonate succession (Unit 4) that contains an upsection decrease in

227 abundance of fossils through the following lithic succession: a lowermost nodular lime mudstone

228 and skeletal packstone with abundant fossils, including crinoids (Fig. 8); a nautiloid-bearing

229 dolopackstone with some associated benthic skeletal material; and, burrowed lime mudstone.

230 Blackened burrowed erosional surfaces occur within the lower limestone, and coarser more

231 fossiliferous beds have basal erosional contacts (Fig. 9D). A recessive 2-cm-thick bed of

232 smectite-bearing clay caps Unit 4 and is likely an altered volcanic ash (Kang 2018). Unit 5 is

233 disconformably overlain by Quaternary sediment and consists of medium crystalline dolostone

234 with no obvious depositional features.

235 On adjacent Little Manitou Island, the basal coarse-grained breccia is absent. Instead, metre-

236 scale outcrop exposure demonstrates the following composite succession (see Kang 2018)

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237 onlapping a low-relief paleotopographic high of Precambrian gneiss along the western lakeshore:

238 feldspathic arenite with abundant short nautaloids and other marine benthic fossils (Fig. 9E;

239 facies S1-c, Table 2), pebble-bearing skeletal dolostone (facies D5-b, Table 1; similar to Unit 2

240 above), and finely interbedded argillaceous dolomudstone and lime mudstone (Fig. 9F).

241

242 Owen Quarry

243 This abandoned quarry occurs a few kilometres southeast of Lake Nipissing (Fig. 2A). Strata are

244 exposed in three fault blocks (Locs. 5A-C) according to contrast in structural attitudes (Fig. 2D).

245 The principal section is Loc. 5A (Figs. 10 and 11A); strata at Loc. 5B and 5C correlate with the

246 lower and uppermost parts of this section, respectively (Kang 2018). Contact with Precambrian

247 rocks is not exposed, and a vegetated, rock-filledDraft narrow (1-2 m) gulley separates outcrop at Loc.

248 5C from a large fault escarpment of Precambrian gneiss (Lumbers 1971).

249 Units 1 and 2 consist of two interbedded facies: medium-thick beds of crystalline sandy and

250 skeletal-rich dolograinstone to rudstone with erosional basal contacts that overlie thinner beds of

251 finely crystalline fossiliferous dolostone (Fig. 11B). Planar and trough cross-stratification are

252 developed, including steeply (20-30o) inclined cross-sets in Unit 2. Sand-sized, circular to ovoid-

253 shaped, non-skeletal grains display core-rim differentiation (Fig. 11C), and are interpreted as

254 ooids. They occur only in the coarse-grained facies. Fossil fragments are dolomitized, but forms

255 are sufficiently preserved to characterize a diverse assemblage of differentially blackened crinoid

256 ossicles and cryptostomid bryozoans; whole to disarticulated bivalve or brachiopod shells; whole

257 to fragments of the rugose coral, Lambeophyllum profundum (Conrad); fragments of trilobites;

258 and a small encrusting tabulate coral (Kang and Dix 2020). Conformably overlying this

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259 succession is a finely crystalline dolostone (Unit 3) with rare crinoid ossicles and whole

260 specimens of L. profundum.

261 Unit 4 is represented mostly by a covered interval (Fig. 10 and 11A) except for a decimetre-

262 scale exposure of finely crystalline dolostone similar to Unit 3, but interbedded with greenish

263 dolomitic siltstone (Fig. 11D). This facies association also makes up large (metre-scale) quarried

264 blocks piled across the covered interval (Fig. 11A). There is no evidence to suggest that the

265 blocks have been moved significantly from their blast site. They contain locally abundant shell

266 fragments to disarticulated valves of brachiopods, fragmented gastropods, crinoid ossicles,

267 fragmented bryozoans, and rugose corals. Most prominent, however, are large trace fossils,

268 Chondrites, Palaeophycus, and Bergaueria (Fig. 11E), that extend from dolostone into siltstone.

269 The remainder (Unit 5) of the section isDraft a hard, finely crystalline, massive dolostone.

270

271 Biostratigraphy

272 A Sandbian age had been established for the Deux Rivières outlier and units 4 to 6 in Brent

273 Crater based on Blackriveran fossils (Colquhoun 1958; Lozej and Beales 1975a; Grahn and

274 Ormö 1995). A poorly resolved late Sandbian-early Katian age and more definitive early Katian

275 age were interpreted for the Manitou Island and Owen Quarry outliers, respectively, on the basis

276 of macrofossils (Colquhoun 1958). Our study reinforces these interpretations (Fig. 12) with

277 updated taxonomic lists and new fossil occurrences (Kang and Dix 2020) as summarized below.

278 The Deux Rivières, Great Manitou Island, and Brent Crater sections demonstrate, collectively,

279 a faunal succession concordant with Turinian strata in the Ottawa Embayment and northern

280 Appalachian Basin. The bryozoan Stictopora labyrinthica labyrinthica Hall (Fig. 12A) in units

281 1-3 of the Deux Rivières outlier and one specimen in the Great Manitou Island section is a form

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282 associated with the Lowville-Watertown formation succession of the northern Appalachian Basin

283 (New York State) (Ross 1964). This range overlaps with that of the calcareous worm tubes,

284 Tymbochoos sinclairi Okulitch (Fig. 12B, C), restricted to the Pamelia and Lowville formations

285 of the Ottawa Embayment (Steele-Petrovich and Bolton 1998), found in Unit 3a in the Deux

286 Rivières outlier and Unit 4 of Brent Crater. The co-occurrence of the chitinozoan Conochitina

287 schopfi Taugourdeau, now in the genus Belonechitina?, with T. sinclairi in Unit 4 at Brent Crater

288 also reinforces a Sandbian age. The chitinozoan species was first described from Sandbian, but

289 not younger, strata in Oklahoma (see Grahn and Ormö 1995). The bryozoan Pachydictya acuta

290 tabulata Ross recovered from Unit 5 in the Deux Rivières outlier (Fig. 12D) has a range in the

291 northern Appalachian Basin from the upper Watertown Formation of Sandbian age through

292 undifferentiated lower Trentonian strataDraft (Ross 1964) of early Katian age. Conodonts from Unit 5

293 support a zonal range spanning the stage boundary (Table 3, Fig. 12).

294 Reinforcement of an early Katian age for strata in Owen Quarry is supported by the following

295 macrofossil assemblage (Fig. 12): the coral Lambeophyllum profundum Conrad in units 1-3; the

296 bryozoan Escharopora recta Hall in Unit 2; the brachiopod Dinorthis iphigenia Billings or its

297 variant minor in units 1 and 2; and, a single cluster of the distinctive bryozoan Arthroclema

298 pulchella Billings reported from Trentonian strata in the Ottawa Embayment and central Ontario

299 (Kang and Dix 2020). A conodont assemblage from Unit 1 records a range that likely spans the

300 Sandbian-Katian stage boundary (Fig. 12, Table 3).

301

302 Isotope Chemostratigraphy

303 Stable isotope (C, O) and Sr-isotope stratigraphic profiles identify potential depositional to early

304 diagenetic (or marine-derived) signatures thereby aiding in correlation among outliers and with

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305 coeval strata along the greater Laurentian platform. Strong isotopic (δ13C, δ18O) covariance is

306 usually taken to define burial diagenetic alteration (Columbié et al., 2011; Oehlert and Swart,

13 307 2014). δ Ccarbonate values increase upsection through Sandbian strata (Fig. 3A, 5A, 8). For the

308 Deux Rivières outlier, they increase into the range of marine calcite (Fig. 3A; Tobin and Walker

309 1994; Saltzman and Thomas 2012) along with increased abundance of skeletal-diverse and

310 crinoid-bearing limestone. In this section, 87Sr/86Sr ratios also shift upsection toward marine

311 values (Edwards et al. 2015) in open marine carbonate of Unit 5 (Fig. 3A). Some δ18O values are

312 similar to contemporary marine calcite but strongly negative in dolostone (units 1 and 4) as well

313 as limestone of Unit 3b interbedded with shale. There is little covariance between δ18O and δ13C

314 except in Unit 1 and only weakly developed (r2=0.29; Kang and Dix 2020) through the interval

315 ~6 to 7.5 m above the section base (Fig.Draft 3A).

13 316 The Brent Crater section preserves two scales of δ Ccarbonate variation. First, a large-scale (∼22

317 ‰) increase extends upsection from an apparent baseline of -18 to -20 ‰ in Unit 2 (Fig. 5A).

318 The increase reaches an apparent compositional plateau varying about 2 ‰ within Unit 3, then

319 returns to the negative baseline just beneath Unit 4 (Fig. 5A). 18O values over this same interval

320 fluctuate between -2 and -6 ‰. Isotopic covariance occurs only over a 10 m interval within the

321 compositional plateau, not within the gradients (Fig. 5A). The second scale of δ13C variation is

322 smaller fluctuation (~2-3 ‰) forming positive excursions in the upper 20 m of Unit 6 (Fig. 5B).

323 This occurs coincident with very abrupt inter-sample variation (-7 to -1 ‰) in 18O. The lower

324 20 m of Unit 6 exhibit strong C and O isotopic covariance (Fig. 5B).

325 In the Manitou Island section, upsection increase in δ13C values crosses the lower limit of

326 Turinian marine calcite at ~5 metres above the base (Fig. 8). However, a negative deflection

327 occurs over 1.5 m starting beneath Unit 4 and extending into the lower part of this unit (Fig. 8).

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328 δ18O variation shows isotopic variation related to lithology (Fig. 8): in dolostone, inter-sample

329 variation is minor, yet values are strongly negative relative to the marine reference; in limestone

330 (Unit 4), δ18O values fall within range of Turinian marine calcite, yet an 87Sr/86Sr value of

331 0.70866 from this limestone (Kang and Dix 2020) is much greater than contemporary seawater.

332 In contrast to the Sandbian sections, Katian strata of Owen Quarry displays an upsection

13 333 decrease in δ Cdolomite from values within range of contemporary marine calcite (Fig. 10; Tobin

334 et al. 2005). Saddle dolomite occupies secondary porosity and exhibits a relatively uniform

18 335 composition throughout the section. δ O values for both dolomite cohorts display little

336 stratigraphic variation and, as with Sr-isotope ratios, are well outside the marine range (Fig. 10).

337

338 Discussion Draft

339 A Sandbian Carbonate Platform in the Craton Interior

340 Sections at Deux Riviéres, Brent Crater, Cedar Lake, and Great Manitou Island each record

341 marine transformation of an initial terrigenous or mixed siliciclastic-carbonate depositional

342 system into a carbonate platform system. Appearance of mud-dominated carbonate facies reflect

343 low-energy conditions, with limited fossil diversity, whereas continued development of the

344 platform, as illustrated by the Deux Riviéres and upper part (Unit 6) of the Brent Crater

345 succession, demonstrates greater variation in facies, including high-energy ooid production and

346 greater fossil diversity. This overall transformation is predicted along an epicontinental platform

347 wherein net sequestration of siliciclastics (and likely coastal turbidity by association) occurs

348 along a retreating shoreline in response to sea-level rise (Handford and Loucks 1993).

349 Transgression resulted in development of a mixed tropical-carbonate biotic assemblage of

350 heterozoan filter feeders, trilobite scavengers, and microbial (stromatolites and oncolites) and

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351 phototrophic (calcareous algae, tabulate coral) productivity. The presence of phototrophs and

352 ooids supports warm-water carbonate production at the contemporary paleotropical latitude for

353 this region (Cocks and Torsvik 2011).

354

355 Local Records of Initial Marine Transgression

356 The record of marine transgression differs among the outliers and attests to varied terrestrial to

357 nearshore siliciclastic environments within the craton interior. First, the base of the Deux

358 Rivières outlier exposes a high-energy siliciclastic shoreface (lower Unit 1) with Skolithos and

359 fragmented, blackened fossil fragments that identify substrate mobility combined with

360 synsedimentary burial and exhumation (Baird and Brett 1991; MacEachern et al. 2010). This

361 sandy, silty dolomudstone may documentDraft the local record of Sandbian transgression succeeded

362 by accumulation of offshore low-energy muddy carbonate (upper Unit 1; Fig. 3A).

363 Second, marine transgression appears to have reworked residual (regolith) terrestrial deposits

364 forming basal deposits of sections at Cedar Lake (Loc. 3) and Great Manitou Island (Loc. 4). At

365 Cedar Lake, the basal feldspathic wacke defines a chemically and mechanically immature

366 deposit apparently restricted to a local paleotopographic depression (Fig. 7A). The overlying

367 arenite likely illustrates shoreface reworking that segregated siliciclastic fines, and continued

368 transgression culminated in formation of a low-energy muddy platform setting. At Great

369 Manitou Island, transgression produced an initial high-energy boulder-rich shoreface. The

370 absence of this facies on nearby Little Manitou Island (Fig. 2C), but appearance of a basal

371 arenite, may indicate transgression occurred in a region of differentially weathered boulder-sized

372 material (e.g., corestones, Mignon and Thomas 2002). Syenite is 40-80 times more susceptible to

373 such weathering than the surrounding Precambrian gneiss (Franke 2009). Reworking of residual

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374 boulder-sized material generated, initially, a rocky shoreface with a coarse-grained matrix

375 accumulating between breccia blocks. These interblock environments served as protective

376 habitats for colonies of bivalves. Continued transgression is marked by an upsection decrease in

377 both grain size and abundance of basement-derived material (through to Unit 3) that suggests

378 gradual burial of an initial residual paleotopography, eventually replaced by a low-energy muddy

379 carbonate platform. Thus, the records of transgression at Cedar Lake and Manitou Islands

380 demonstrate submergence of variable paleotopography, from undulating (low-relief

381 monadnocks) to rocky (regolithic) settings. This broadens the spectrum of shoreline types

382 produced in response to Phanerozoic transgressions across the Laurentian interior (Johnson and

383 Baarli 1999; Nelson and Johnson 2002).

384 A third variation in the nature of localDraft marine transgression is documented in the Brent Crater

385 section. Lack of a confirmed age for units 1-3 precludes knowing if these units predate or are

386 part of the Sandbian transgression. Lozej and Beales (1975a) interpreted this interval to

387 characterize deposition within a variably hypersaline (peritidal) tidally-influenced crater lake

388 eventually destroyed by marine transgression (producing their arkosic sandstone between ~130-

389 150 m above the base of the section; see their Fig. 5). Our study supports a tidal signature for

390 Unit 1 (e.g., sand-shale couplets) but observations related to our units 2 and 3 require a different

391 interpretation than that of Lozej and Beales (1975a). First, the gypsum layers are fracture-fill

392 deposits (Fig. 6A), not depositional in origin; and (2) the section from 130-150 m contains a

393 finely interlaminated lithic (sandstone, siltstone, carbonate) variation (Fig. 6C). This lithic motif

394 supports continued tidal influence along an evolving mixed siliciclastic-carbonate platform rather

395 than reworking of crater walls (Lozej and Beales, 1975a). Continued transgression established a

396 low-energy marine carbonate platform (Unit 4).

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397 Correlation with the Greater Laurentian Platform

398 The paleotropical Sandbian carbonate facies and their stratigraphic succession comprising outlier

399 sections in the northern Ottawa-Bonnechère graben are similar to those that characterize

400 contemporary development of the greater southern Laurentian platform that underlies eastern

401 North America. This suggests effective cross-platform oceanographic communication during net

402 transgression, as illustrated below.

403 First, the microbial limestone of lower Unit 4 in the Brent Crater section marks a prominent

404 transgressive step-back of the interpreted prior mixed siliciclastic-carbonate depositional system

405 (Unit 3). In the Ottawa Embayment, ~180 km to the southeast (Fig. 1A), a stromatolitic

406 biostrome of similar thickness occurs in the lowermost Pamelia Formation and extends

407 stratigraphically to the northwestern limitDraft of the embayment over a distance of at least 100 km.

408 The local stratigraphy documents an abrupt transgressive step-back of a mixed siliciclastic-

409 carbonate platform succeeded by an embayment-wide low-energy muddy-carbonate platform

410 (Dix et al. 2013). The presence of Tymbochoos sinclairi above the biostrome in Unit 4 of Brent

411 Crater and restriction of this fossil to the Pamelia-Lowville formation succession in the

412 embayment (Steele-Petrovich and Bolton 1998) may identify coeval environmental response to

413 regional transgression. This may indicate that older strata (units 1-3) in the Brent Crater section,

414 and the bolide impact are of earliest Sandbian age (Fig. 12), an age accommodated by new

415 geochronological data for the underlying fall-back breccia (McGregor et al. 2020).

416 Second, the overall facies transition among outlier sections from an initial mud-rich carbonate-

417 platform succession to one with greater diversity of shallow subtidal carbonate facies and abrupt

418 stratigraphic juxtaposition of high- and low-energy facies (e.g., lime mudstone and skeletal-ooid

419 grainstone) is similar to that found among Sandbian successions south of the Canadian Shield. In

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420 the Ottawa Embayment and northern Appalachian Basin (central Ontario), muddy peritidal

421 carbonates of the Pamelia and equivalent lower Gull River formations are succeeded by high-

422 order subtidal or peritidal facies variation characteristic of the Lowville and equivalent upper

423 Gull River formations (Fig. 1C; MacFarlane 1992; Grimwood et al. 1999; Salad Hersi and Dix

424 1999; El Gadi 2001; Oruche et al. 2018). The vertical facies transition can be extended into

425 equivalent strata farther south in the Appalachian Basin of the eastern United States (Holland and

426 Patzkowsky 1996). As with the outlier sections, contemporary carbonate production across the

427 Laurentian platform included a mixed assemblage of microbial, photozoan, and heterozoan

428 sources. Peripheral to the southern Canadian Shield, the Coboconk-Selby and equivalent

429 Watertown-L’Orignal formation successions in central Ontario and the Ottawa Embayment

430 respectively, demonstrate that continuedDraft transgression resulted in common development of

431 deeper subtidal, low- to high-energy, facies expressed initially by oncolitic, burrowed, and

432 peloidal facies along with evidence for local wave-base planation and hardground development

433 in (Fig. 1C; El Gadi 2001; Oruche et al. 2018). Similar attributes characterize the uppermost

434 strata of the Deux Rivières and Brent Crater outliers each exhibiting different attributes of this

435 facies variation.

436 Third, outlier sections reveal high-order variation in facies succession that suggest rhythmic

437 depositional controls. Such variation does not occur in all parts of the Sandbian successions

438 peripheral to the Canadian Shield (Grimwood et al. 1999), but three different motifs occur within

439 the outliers:

440 (1) At Cedar Lake, centimetre-scale couplets define normal-marine (crinoid-bearing) facies

441 grading up into unfossiliferous sandy dolomudstone. Although the dolostone is a diagenetic

442 replacement, the skeletal ghosts serve as evidence that the basal deposits reflect more open-

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443 marine circulation (with local erosion) whereas the transition to sandy carbonate mudstone

444 suggests shallower (nearshore) deposition subject to greater environmental restriction. Such thin

445 couplets identify restricted water-depth variation as expected within inner-ramp (peritidal)

446 environments (Pratt 2010).

447 (2) In the Deux Rivières outlier, three vertical successions of muddy limestone changing

448 upsection to skeletal/ooid-bearing limestone (i.e., Units 3a-b, 3c-d, and Unit 5) are similar to

449 subtidal shoaling cycles on modern and ancient carbonate platforms (Jones 2010) with the

450 exception that basal transgressive (deepening) phase seems to be absent (or not recognized).

451 Upsection change from radial (Unit 3a) to laminated (Unit 5) ooid cortices also suggests net

452 increase in depositional energy (Davies et al. 1978) with each cycle. Such a change might arise if

453 fluctuations in water depth spanned a decreasingDraft rate of transgression.

454 (3) Temporal variation in abundance of siliciclastics along an inner epicontinental platform is

455 expected with change in base-level and-or sediment supply. This provides the basic elements for

456 interpreting alternating carbonate-siliciclastic accumulation in Unit 5, and apparent rhythmic

457 deposition in Unit 6 at Brent Crater (Fig. 5B). First, within the otherwise thick lower wacke of

458 Unit 5 (Fig. 5B), the presence of a thin bed of fractured lime mudstone documents higher order

459 variation in base-level. The presence of fracturing, reworked limestone clasts, and development

460 of diffuse clast contacts (Fig. 6D) are also characteristics of some stony soils (Tabor et al. 2017)

461 indicating exposure related to base-level fall. Second, in Unit 6, change in siliciclastic abundance

462 and carbonate textures defines deepening-shallowing patterns characterized by cycles C2, C3,

463 and C4 (Fig. 5B). These patterns are similar to those found in Quaternary and older subtidal

464 platform depositional cycles (Jones 2010) including the basal coarse-textured carbonate as a

465 transgressive (deepening) phase and regressive phase of deposition (Fig. 5B). Where a more

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466 substantive drop in sea level has occurred, or in response to greater siliciclastic supply, the

467 regressive phase contains increased admixture of siliciclastics. Renewed transgression has also

468 reworked siliciclastics into discrete beds at the base of cycle C3 and C4 (Fig. 5B).

469 The association of quartz arenites with transgressive phase of cyclic deposition is part of a

470 long-term history of increased siliciclastic maturity moving upsection within the carbonate-

471 platform succession in Brent Crater; that is, from feldspathic wacke (Unit 5a), through

472 feldspathic arenite (Unit 5c), to quartz arenite (Unit 6b, d). This change cannot be explained by

473 base-level fall (or forced regression) or sediment supply. Instead, the stratigraphic change

474 coincides with appearance of subtidal, open-marine carbonate facies; in other words, there was

475 increased potential for reworking of siliciclastics (and weathering) within emerging subtidal

476 settings through wave or current activityDraft driven by net transgression.

477

478 13C Characterization of Marine and Terrestrial Carbon Reservoirs

479 Each of the Sandbian outlier sections display upsection enrichment in 13C toward

480 contemporary marine-like values coincides with net transgression, siliciclastic sequestration, and

481 appearance of more open-marine carbonate facies. This suggests increasing oceanographic

482 communication with a regional marine-carbon reservoir during net transgression. This is

483 supported by local co-occurrence of marine-like 87Sr/86Sr ratios associated with ooid-skeletal

484 carbonate facies (Unit 5 at Deux Rivières) typical of marine carbonate platforms with good

485 cross-platform circulation (Jones, 2010; Diaz and Eberli, 2019).

486 The 13C record, however, contains apparent positive excursions. These isotopic excursions

487 are of similar scale as those within coeval Sandbian platform successions farther to the south and

488 southeast (Ludvigson et al. 2004; Oruche et al. 2019). In general, this isotopic variation is

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489 interpreted to document some combination of oceanographic controls influencing burial and

490 oxidation of carbon and-or short-term change in ocean-atmospheric exchange of carbon

491 (Bergström et al. 2010). In a craton-interior region such as the study area, wherein transgression

492 is recorded by a depositional-system shift from terrestrial, through coastal, to marine conditions,

493 there is increased likelihood that fluctuations in 13C also records mixtures of terrestrial-derived

494 and-or marine carbon sources (Moyer et al. 2011). Within Unit 6c of the Brent Crater section, for

495 example, negative transposition of δ13C from the contemporary marine reference is maximized in

496 association with increased abundance of siliciclastics admixed with carbonate in cycle C4 (Fig.

497 5B). This negative transposition disappears with renewed transgression (C5) that produces

498 deeper water, more open-marine carbonate facies (Fig. 5B). A more dramatic larger scale

499 excursion is documented in units 2 and Draft3 of Brent Crater wherein there is a positive shift in 13C

500 values from a strongly negative baseline (-18 to -20 ‰), through marine-like values, then a

501 return to the baseline in uppermost Unit 3. The negative baseline may characterize the

502 contemporary terrestrial carbon source, one either microbially mediated or representing recycled

503 sedimentary origins (Keller and Wood 1993).

504 Short-term variation in δ13C forms an important correlation tool (Bergström et al. 2010), and a

505 tentative regional 13C correlation from the outlier region to the Ottawa Embayment is illustrated

506 (Fig. 13). The section illustrated from the Ottawa Embayment forms part of a regional

507 correlation among Sandbian δ13C profiles in the Ottawa Embayment and upper Mississippi

508 Valley, central United States, a distance of ~1400 km strike-parallel to the regional Laurentian

509 platform (Oruche et al. 2019). The outlier-Ottawa Embayment correlation (Fig. 13) is

510 constrained by correlative Watertown and equivalent Coboconk lithofacies and similar profile

511 geometry above a zone of interpreted diagenetic influence based on covariant isotope profiles

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512 (see above). The overall negative transposition of the Brent Crater profile in excursion 2 (Fig.

513 13), when compared to the others, likely reflects increased influence of terrestrial-sourced carbon

514 within the coastal reservoir as described above. Of local significance, the correlation suggests

515 that the covered interval between units 5 and 6 in the Deux Rivières outlier may be underlain by

516 siliciclastics.

517

518 A Katian Carbonate Platform in the Craton Interior

519 Transgression across the southern Laurentian platform during the earliest Katian is marked by

520 a profound regional facies transition from photozoan- to heterozoan-dominated productivity

521 (Brookfield 1988; Lavoie 1995; Holland and Patzkowsky 1996; Grimwood et al. 1999; Quinton

522 et al. 2018; Oruche et al. 2018). The sectionDraft at Owen Quarry was previously correlated with the

523 Rockland Formation in the Ottawa Embayment (Colquhoun 1958), and this study proposes a

524 more finely tuned correlation that integrates conodont assemblage data and δ13C stratigraphy.

525 The Rockland Formation contains a local expression of the global Guttenberg δ13C excursion

526 (Oruche et al. 2018) and, globally, this excursion is contained within the P. tenuis conodont zone

527 (Bergström et al. 2010) within the lower Katian stage (Goldman et al. 2007). Biostratigraphy for

528 the Owen Quarry section suggests that the basal skeletal-rich carbonate may be of similar age

529 (Fig. 12). If correct, the upsection decrease in δ13C values may indicate deposition during the

530 post-peak decline of the GICE.

531 The Owen Quarry section records an upsection disappearance of siliciclastics through units 1

532 and 2 that accommodates backstepping of a local siliciclastic source with rising sea level. The

533 sedimentary transformation, however, did not establish an initial low-energy muddy platform as

534 in the Sandbian outlier sections but, instead, an initial high-energy, wave- and-or current

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535 influenced platform demonstrated by basal erosional contacts of coarser-grained beds (Fig. 11B),

536 steeply inclined strata (Unit 2) that may define a shoal-face or channel, differentially blackened

537 fossils that illustrate reworking of shallowly-buried skeletal material (Baird and Brett 1991), and

538 coated grains or ooids (Fig. 11C).

539 Dolomite forms a replacement mineralogy in this outlier and the upsection decrease in

540 dolomite crystallinity through to Unit 4 is interpreted to document fining of the original host

541 limestone (Kang 2018). This change corresponds to facies evidence defining deepening from an

542 initial shoal environment (Unit 1 and 2) to a mid-ramp setting (Unit 4) host to a Cruziana

543 ichnofacies and likely below fair-weather wave base (Burchette and Wright 1992; McEachern et

544 al. 2010). This deepening history is similar to, but more stratigraphically condensed than,

545 contemporary platform development withinDraft the lower Trenton Group of the northern

546 Appalachian Basin (Titus and Cameron 1976), and uggests regional commonality in platform

547 response to Katian transgression. The source of the siliciclastic fines in Unit 4 of the outlier

548 section as well as origin of high-order carbonate-siliciclastic segregation remains uncertain.

549 Along an epicontinental ramp, however, such segregation can reflect base-level change

550 influencing one or some combination of terrestrial-derived supply of siliciclastics, long-shore

551 transport, or onlap of more offshore marine siliciclastic mud (Burchette and Wright 1992;

552 Handford and Loucks 1993). The remainder of the outlier section is insufficient to determine if

553 reappearance of only carbonate (Unit 5) represents shallowing along the ramp. If so, it would

554 match contemporary evolution of the greater Laurentian platform to the south (Titus and

555 Cameron 1976; Lavoie 1995; Oruche et al. 2018).

556 The presence of ooids in the basal paleo-shoal facies is not anomalous for such a high-energy

557 setting but contrasts with absence of this grain type in coeval strata along the southern

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558 Laurentian platform (Brookfield 1988; Holland and Patzkowky 1996; Oruche et al. 2018). Owen

559 Quarry is one of three outliers along the graben northwest of the Ottawa Embayment in which

560 ooids are present in high-energy facies of early Katian age (Fig. 1A). Ooids are diagnostic of

561 warm agitated and typically supersaturated seawater (Davies et al. 1978; Diaz and Eberli 2019),

562 and their presence in the outliers but not in the northern Appalachian Basin nor Ottawa

563 Embayment suggests there was an initial cross-platform oceanographic gradient subsequently

564 erased through deepening. This regional environmental gradient might reflect a warm paleo-

565 equatorial water mass compared to cooler waters along the greater Laurentian platform although

566 the role of cool waters in the Appalachian Basin has been recently discounted (Quinton et al.

567 2018). Alternatively, there existed a shallow thermocline intersecting only regional inner-

568 platform bathymetry. Apart from thermalDraft gradients, other potential factors include regional

569 patterns in carbonate supersaturation, microbial mediation, and disruption to ooid mineralization-

570 sequence patterns (Diaz and Eberli 2019).

571

572 Conclusions

573 Four sedimentary outliers (Deux Rivières, Brent Crater, Cedar Lake, and Manitou Islands) in

574 the northern Ottawa-Bonnechere graben document the record of Sandbian transgression within

575 the craton interior whereas strata of another outlier (Owen Quarry) record local expression of

576 regional Katian transgression. Sandbian sea-level rise reworked local fine- to very coarse

577 regolith into sandy to boulder-rich transgressive shoreface sediments, respectively, with local

578 transgression across low-relief smoothed Precambrian monadnocks. Continued sea-level rise

579 caused step-back of siliciclastic influence, resulting in a high diversity of non-skeletal (including

580 ooids) and microbial/heterozoan/photozoan carbonate facies (including ooid grainstone). This

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581 transformation is similar to the change in depositional systems across the contemporary southern

582 Laurentian platform. δ13C positive excursions are interpreted to document changing influence of

583 marine and terrestrial carbon reservoirs as governed by base-level change. Katian transgression

584 is expressed by development of high-energy ooid-heterozoan skeletal carbonate shoals that grade

585 into offshore (Cruziana ichnofacies) interbedded carbonate-siliciclastic deposits. The presence of

586 platform-interior ooids identifies an initial, possible latitudinal, oceanographic gradient along the

587 Laurentian platform.

588

589 Acknowledgements

590 This work represents M.Sc. research by the lead author funded by an NSERC Discovery Grant to

591 G.R. Dix. We thank the following for researchDraft support: Mr. Terry Owen and Ontario Parks for

592 access and sampling in Owen Quarry and Manitou Islands Provincial Park, respectively; the

593 Geological Survey of Canada (Ottawa) for access to the Brent Crater core: Tim Mount (Carleton

594 University) and Vancouver Petrographics Ltd. for thin section preparation; Dr. Shuangquan

595 Zhang (Carleton University) who guided strontium isotopes analyses; Dr. Sandy McCracken

596 (GSC-Calgary) for conodont analysis; Dr. Yuefeng Shen (Hefei University of Technology,

597 China) for confirmation of cyanobacteria and algae; and, the staffs of the Ján Veizer Stable

598 Isotope Laboratory (University of Ottawa) and Queen’s Facility for Isotope Research. Two

599 anonymous reviewers and the Associate Editor provided valuable recommendations.

600

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683 Kang, H., and Dix, G.R. 2020. Paleontological and geochemical datasets for outliers of the

684 northern Ottawa-Bonnechere Graben. https://doi.org/10.5683/SP2/IAYKTS. Scholars Portal

685 Dataverse.

686 Kay, G.M. 1942. Ottawa-Bonnechere graben and Lake Ontario homocline. Geological Society of

687 America Bulletin, 53: 585–646.

688 Keller, C.K., and Wood, B.D. 1993. Possibility of chemical weathering before the advent of

689 vascular land plants. Nature, 364: 223–225.

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690 Lavoie, D. 1995. A Late Ordovician high-energy temperate-water carbonate ramp, southern

691 Quebec, Canada: implications for Late Ordovician oceanography. Sedimentology, 42: 95–116.

692 Lozej, G.P., and Beales, F.W. 1975a. The unmetamorphosed sedimentary fill of the Brent

693 meteorite crater, southeastern Ontario. Canadian Journal of Earth Sciences, 12: 606–628.

694 Lozej, G.P., and Beales, F.W. 1975b. Appendix 1-Drill log DDH #1-59 Brent Crater, Depository

695 of Unpublished Data, National Research Council of Canada.

696 Ludvigson, G.A., Witzke, B.J., Schneider, C.L., Smith, E.A., Emerson, N.R., Carpenter, S.J., and

697 González, L.A. 2004, Late Ordovician (Turinian-Chatfieldian) carbon isotope excursions and

698 their stratigraphic and paleoceanic significance: Palaeogeography., Palaeoclimatology, and

699 Palaeoecology, 210: 187–214.

700 Lumbers, S.B. 1971. Geology of the NorthDraft Bay Area, Districts of Nipissing and Parry Sound,

701 Ontario Department of Mines and Northern Affairs, Geological Report 94.

702 Lumbers, S.B. 1976. Mattawa-Deep River Area (western half), District of Nipissing, Preliminary

703 Map P.1196. Ontario Division of Mines, Geological Series, scale 1:63,360.

704 MacEachern, J.A., Pemberton, S.G., Gingras, M.K., and Bann, K.L. 2010. Ichnology and facies

705 models. In Facies models. Edited by N.P. James and R.W. Dalrymple. Geological Association

706 of Canada, St. John’s. pp. 19–58.

707 McFarlane, R.B. 1992. Stratigraphy, paleoenvironmental interpretation, and sequences of the

708 Middle Ordovician Black River Group. MSc thesis, Queen’s University, Canada.

709 McCausland, P.J.A., Van der Voo, R., and Hall, C.M. 2007. Circum-Iapetus paleogeography of

710 the Precambrian-Cambrian transition with a new paleomagnetic constraint from Laurentia.

711 Precambrian Research, 156: 125–152.

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712 McCracken, A.D. 2017. Report on 2 Ordovician (Blackriveran to Kirkfieldian) conodont

713 samples from unnamed strata in small outliers, central Ontario. Geological Survey of Canada,

714 Paleontology Report, 6–ADM–2017.

715 McGregor, M., Dence, M.R., McFarlane, C.R.M. and Spray, J.G. (2020). U-Pb geochronology

716 of apatite and zircon from the Brent impact structure, Canada: a Late Ordovician Sandbian-

717 Katian boundary event associated with L-Chondrite parent body disruption. Contributions to

718 Mineralogy and Petrology, v. 175, 1-20.

719 Metzger, J.G., Fike, D.A., and Smith, L.B. 2014. Applying carbon-isotope stratigraphy using

720 well cuttings for high-resolution chemostratigraphic correlation of the subsurface. American

721 Association of Petroleum Geologists Bulletin, 98: 1551–1576.

722 Mignon, P., and Thomas, M.F. 2002. GrusDraft weathering mantles-problems of interpretation.

723 Catena, 49: 5–24.

724 Moyer, R.P., Bauer, J.E., and Grottoli, A. 2011. Carbon isotope biogeochemistry of tropical

725 small mountainous river, estuarine, and coastal systems of Puerto Rico. Biogeochemistry, 112:

726 1–24.

727 Nelson, S.J., and Johnson, M.E. 2002. Jens Munk Archipelago: Ordovician‐Silurian Islands in

728 the Churchill Area of the Hudson Bay Lowlands, Northern Manitoba. Journal of Geology,

729 110: 577–589.

730 Oehlert, A.M., and Swart, P.K. 2014. Interpreting carbonate and organic carbon covariance in

731 the sedimentary record. Nature Communications, 5: 4672 doi: 10.1038/ncomms567.

732 Oruche, N.E., Dix, G.R., and Kamo, S.L. 2018. Lithostratigraphy of the Blackriveran-

733 Rocklandian (Upper Ordovician) foreland succession, and a U-Pb ID-TIMS date for the

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734 Millbrig volcanic ash bed, in the Ottawa Embayment: relevance for extrabasinal correlation in

735 eastern North America. Canadian Journal of Earth Sciences, 55: 1079–1102.

736 Oruche, N.E., Dix, G.R., and Gazdewich, S. 2019. 13C stratigraphy of a Turinin-Chatfieldian

737 (Upper Ordovician) foreland succession, Ottawa Embayment (central Canada): resolving local

738 and inter-regional isotope excursions in a tectonically active basin. Palaeogeography,

739 Palaeoclimatology, Palaeoecology, 528: 186–203.

740 Patchett, P.J., Embry, A.F., Ross, G.M., Beauchamp, B., Harrison, J.C., Mayr, U., Isachsen,

741 C.E., Rosenberg, E.J., and Spence, G.O. 2004. Sedimentary cover of the Canadian Shield

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743 Basin, Arctic Canada. Journal of Geology, 112: 39–57.

744 Pratt, B.R. 2010. Pertidal Carbonates. InDraft Facies Models 4. Edited by N.P. James and R.W.

745 Dalrymple. Geotext 6, Geological Association of Canada, pp. 401–421.

746 Quinton, P.C., Law, S., Macleod, K.G., Herrmann, A.D., Haynes, J.T., and Leslie, S.A. 2018.

747 Testing the early Late Ordovician cool-water hypothesis with oxygen isotopes from conodont

748 apatite. Geological Magazine, 155: 1727–1741.

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750 Paleontology, 38: 1–32.

751 Salad Hersi, O., and Dix, G. R. 1999. Blackriveran (lower Mohawkian, Upper Ordovician)

752 lithostratigraphy, rhythmicity, and paleogeography: Ottawa Embayment, eastern Ontario,

753 Canada. Canadian Journal of Earth Sciences, 36: 2033–2050.

754 Saltzman, M., and Thomas, E. 2012. Carbon isotope stratigraphy. In The Geologic Time Scale

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756 207–232.

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757 Sanford, B.V. 1993. St. Lawrence Platform-Geology. In Sedimentary cover of the craton in

758 Canada. Edited by D.F. Stott and J.D. Aitken. Geological Survey of Canada, Geology of

759 Canada, vol. 5, Ottawa. pp. 723–786.

760 Steele-Petrovich, H.M., and Bolton, T.E. 1998. Morphology and palaeoecology of a primitive

761 mound-forming tubicolous polychaete from the Ordovician of the Ottawa Valley, Canada.

762 Palaeontology, 41: 125–145.

763 Stott, D.F. 1991. Geotectonic correlation chart, Sheet 3, Southernmost Prairie Provinces, Hudson

764 Platform and St. Lawrence Platform. In Sedimentary Cover of the North American Craton:

765 Canada. Edited by D.F. Stott and J.D. Aitken. Geological Survey of Canada, Ottawa.

766 Tabor, N.J., Myers, T.S., and Michel, L.A. 2017. Sedimentologist's guide for recognition,

767 description, and classification of paleosols.Draft In Terrestrial Depositional Systems. Edited by

768 K.E. Zeigler and W. Parker. Elsevier. pp. 165–208.

769 Titus, R.C., and Cameron, B. 1976. Fossil communities of the lower Trenton Group (Middle

770 Ordovician) of central and northeastern New York. Journal Paleontology, 50: 1209–1225.

771 Tobin, K.J., and Walker, K.R. 1994. Meteoric diagenesis below a submerged platform:

772 implications for δ13C compositions prior to pre-vascular plant evolution, Middle Ordovician,

773 Alabama, USA. Sedimentary Geology, 90: 95–111.

774 Tobin, K.J., and Walker, K.R. 1997. Ordovician oxygen isotopes and paleotemperatures.

775 Palaeogeography, Palaeoclimatology, and Palaeoecology, 129: 269–290.

776 Tobin, K.J., Bergström, S., and de la Garza, P. 2005. A mid-Caradocian (453 Ma) drawdown in

777 atmospheric pCO2 without ice sheet development? Palaeogeography, Palaeoclimatology, and

778 Palaeoecology, 226: 187–204.

779

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780 Figure Captions

781 Figure 1. Geological framework along the southern Canadian Shield. A) Distribution of

782 Ordovician outliers (1-5) relative to the boundary limits (red dashed lines) of the

783 Ottawa-Bonnechere (OBG) and Timiskaming (TG) grabens, and distribution of

784 Precambrian bedrock (white) and Paleozoic sedimentary cover (grey) in south-

785 central Canada and the adjacent United States. Lower Katian sections with ooids are

786 noted by red arrows (Oruche et al., 2019; this study). The interior limit of the

787 Appalachian orogen (AO) and location of a topographic profile (X-X') presented in

788 Fig. 1B are indicated. The inset map shows distribution of regional sedimentary

789 basins, regional arches (thin dashed lines), and axes of the OBG and TG grabens.

790 Basin abbreviations: OE, OttawaDraft Embayment; M, Michigan Basin; A, Appalachian

791 Basin; MR, Moose River Basin; and HB, Hudson Bay Basin. Map drawn in Inkscape

792 and modified from Sanford (1993). No permissions required. B) Topographic profile

793 (SN in Fig. 1A) across the OBG and TG axes was generated using Google Earth Pro

794 and completed using Inkscape. Shown schematically are major high-angle faults, the

795 alkaline intrusion beneath Loc. 4, and a structural platform underlying Loc. 5

796 adjacent to a regional fault escarpment. No permissions required. C) Middle and

797 Upper Ordovician formations and megasequence divisions underlying platform

798 successions peripheral to the southern Canadian Shield. Based on Stott (1991),

799 Ettensohn and Brett (2002), Armstrong and Carter (2010), and Oruche et al. (2018).

800

801 Figure 2. Local Precambrian bedrock geology in the region of Upper Ordovician outliers in the

802 northern Ottawa-Bonnechère graben. Maps drawn using Inkscape, modified from

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803 Baer et al. (1971) and Lumbers (1976), with no permissions required. A) Distribution

804 of outliers: 1, Deux Rivières; 2, Brent Crater; 3, Cedar Lake; 4, Manitou Islands; and

805 5, Owen Quarry. B) Brent Crater (Loc. 2), with location of core I-59 (Lozej and

806 Beales, 1975a), and the nearby Cedar Lake (Loc. 3) outlier. Brent Crater is capped by

807 a mantle of Quaternary sediment and is host to two lakes: Gilmour (G) and

808 Tecumseh (T). C) The elliptical distribution of the Manitou Islands, with the

809 principal outlier section on Great Manitou Island (Loc. 4), is shown relative to the

810 interpreted underlying distribution of a Neoproterozoic syenite intrusive (Lumbers

811 1971). D) Outcrop distribution at Owen Quarry (Loc. 5) among three fault blocks (A-

812 C) adjacent to a fault escarpment of Precambrian gneiss.

813 Draft

814 Figure 3. Stratigraphic attributes of the Deux Rivières outlier. A) The lithologic succession

815 (metres) illustrating facies types, interpreted depositional energy, shallowing and

816 deepening successions, and inferred (dashed line) intervals, fossil types, distribution

817 of key fossils, and isotope profiles. Grey boxes define the isotopic compositional

818 ranges for Sandbian marine calcite (Tobin and Walker 1997; Tobin et al. 1997, 2005;

819 Edwards et al. 2015). Dashed box outlines identify intervals within which isotope

820 trends appear covariant. B) Legend for lithology and fossil types applicable to this

821 and subsequent outlier sections. Details of facies types and interpreted environments

822 are provided in Tables 1 and 2.

823

824 Figure 4. Outcrop and facies characteristics, Deux Rivières outlier. A) Shoreline escarpment

825 illustrating the gentle southeasterly shallowing of dip. Locations of Figs. 4B and 4C

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826 are indicated (B and C, respectively). Scale refers to the vertical plane of the

827 escarpment. B) Unit 1, resistant dolostone. The measuring stick is ~ 0.8 m in length.

828 C) Outcrop exposure of dolostone (Unit 4), about ~1.5 m in thickness (double

829 arrow). D) Thin section (plane-polarized light) of ooid-skeletal grainstone (Unit 5b)

830 host to the reported conodont assemblage. Scale bar = 2 mm. E) Thin-section (plane-

831 polarized light) of Girvanella oncolites (white arrows) in skeletal packstone of Unit

832 6. Cores of oncolites often display a bored skeletal fragment (black arrow). Scale bar

833 = 2 mm.

834

835 Figure 5. Stratigraphic attributes at Brent Crater for (A) core #1-59 and (B) Unit 6. Vertical

836 measure in feet allows comparisonDraft with section of Lozej and Beales (1975a, b). See

837 Fig. 3 for explanation of symbols, lithology, and fossil types, and Tables 1 and 2 for

838 facies details. Shallowing-deepening divisions are separated into cycles. Positive

839 13C excursions are numbered in Unit 6 (Fig. 5B). A geologic cross-section (inset,

840 lower right) through the crater (with position of lakes GL and TL indicated; see Fig.

841 2B) illustrates lithostratigraphic divisions fit to the stratigraphic geometry of Lozej

842 and Beales (1975a) above fractured and shock-metamorphosed (fsm) crystalline

843 basement.

844

845 Figure 6. Selected facies and sedimentary structures in core 1-59, Brent Crater. Scale for all

846 figures is 1 cm. A) Sub-horizontal fibrous gypsum (or satin-spar) veins in Unit 1. B)

847 Dolomudstone breccia within syndepositionally deformed siltstone matrix, Unit 2. C)

848 Thinly bedded to laminated siltstone, fine-grained sandstone, and argillaceous lime

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849 mudstone, Unit 3. D) Angular to rounded soil- (or ped) like bodies and related

850 microfractures in lime mudstone succeeded by wacke (grey-green), lower Unit 5. E)

851 Lensoid geometry of clayey skeletal wackestone (dark brown) and skeletal-ooid

852 packstone and wackestone (light brown) with local hardground (white arrow),

853 uppermost Unit 6.

854

855 Figure 7. Stratigraphic and facies attributes of the Cedar Lake outlier. A) Correlation of

856 sections A and B extending across a low monadnock of Precambrian gneiss. See Fig.

857 3 for additional explanation of symbols, lithology, and fossil types, and Tables 1 and

858 2 for facies details. B) Covered interval (hammer, circled, for scale) separating

859 Precambrian (PC) and OrdovicianDraft (O) rocks at Section B. C) Thin section (plan-

860 polarized light) of basal ferruginous feldspathic wacke. Scale bar = 1 mm. D)

861 Gradational contact (dashed line) between units 1 and 2, section A. Exposed

862 thickness of Unit 1 is ~50 cm. E) Thin section (plane-polarized light) of skeletal

863 dolostone facies (Unit 2, section A) with skeletal ghosts of crinoid ossicle (black

864 arrow), fragments of pyritized bivalve (black-outlined arrow) and Fe-oxidized

865 cryptostomid bryozoan. Scale bar = 1 mm.

866

867 Figure 8. Stratigraphic attributes of the Great Manitou Island section. See Fig. 3 for additional

868 explanation of symbols, lithology, and fossil types, and Tables 1 and 2 for facies

869 details. Light-grey bars indicate isotopic range of Sandbian marine calcite.

870

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871 Figure 9. Selected outcrop expression of the Manitou Islands outlier. A) Two boulder-size

872 syenite clasts (white dashed lines) with intervening sand matrix form basal breccia

873 that overlies nonconformably (yellow line) crystalline basement, Great Manitou

874 Island. Hammer for scale. B) Photograph of polished slab of feldspathic arenite

875 matrix of the basal boulder breccia showing dolomitized bivalve shells (arrows).

876 Scale bar is 1 cm. C) Outcrop of pebbly dolostone (Unit 2, Great Manitou Island).

877 Knife for scale. D) Limestone of Unit 4a (Great Manitou Island) exhibiting two

878 styles of erosional surfaces in lime mudstone: a burrowed discoloured firmground

879 (lower arrow), and erosional contact (upper arrow) with overlying skeletal

880 wackestone. Scale bar is 1 cm. E) Pebbly feldspathic arenite (Little Manitou Island;

881 see Fig. 2C for location) withDraft abundant fossilized whole body orthoconic nautiloids

882 (arrow). Knife for scale. F) Thinly interlaminated lime mudstone and dolomudstone

883 forming the highest unit (Little Manitou Island). Length of measuring stick is 1.1 m.

884

885 Figure 10. Stratigraphy of the Owen Quarry outlier, Loc. 5 (see Fig. 2). See Fig. 3 for

886 additional explanation of symbols, lithology, and fossil types, and Tables 1 and 2

887 for facies details. The light grey box indicates the isotopic range for Sandbian

888 marine calcite whereas the dark grey box indicates the range for early Katian marine

889 calcite (Tobin and Walker 1994, 1997; Tobin et al. 2005).

890

891 Figure 11. Outcrop and petrographic attributes of the Owen Quarry outlier. A) Field view of

892 two outcrop areas (A, B), with area C just beyond the photo frame (see Fig. 2D).

893 The arrow (mid-centre) indicates the covered interval with large quarried blocks

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894 representing Unit 4. Person (bottom left) for scale. B) Exposure of scour contact

895 (arrow) separating dolomudstone (a) from overlying coarse-grained skeletal

896 dolograinstone (b) of Unit 1, area A. C) Thin-section (plane-polarized light, scale

897 bar = 1 mm) of sandy ooid-skeletal grainstone characteristic of Units 1 and 2, with

898 the inset photo (plane-polarized light, scale bar = 150 μm) showing dolomitized

899 circular grains (white arrows) with oxidized (reddish) cores (a) and clear rims

900 (black arrow). The clear grain is quartz. D) Interbedded burrowed dolomudstone (a)

901 and dolomitic siltstone (b) of Unit 4. Quarter (coin) for scale. E) Large trace fossils

902 of Unit 4. Hammer for scale.

903

904 Figure 12. Biostratigraphic ranges of Draftselected biota and conodont assemblages from the

905 outliers shown relative to Sandbian-Katian lithostratigraphy of the Ottawa

906 Embayment and northern Appalachian Basin (New York), and distribution of the

907 Millbrig Bentonite and Guttenberg δ13C excursion (Bergström et al. 2010; Oruche et

908 al. 2018). The grey boxes identify overlap of individual macrofossil and conodont

909 assemblage ranges. Sources for ranges are indicated, and see Kang and Dix (2020)

910 for details. Thin-section photographs (plane-polarized light, scale bars = 1 mm) of

911 fossils from Deux Rivières outlier: (A) cryptostomid bryozoan Stictopora

912 labyrinthica labyrinthica. (B) fragment of a colony of Tymbochoos sinclairi. (C)

913 Colony of Tymbochoos sinclairi showing splayed arrangement (arrows) of tubes,

914 Unit 4 in Brent Crater. Scale bar = 1 cm. (D) cryptostomid bryozoan Pachydictya

915 acuta tabulata.

916

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917 Figure 13. 13C profiles and correlation among outliers and a section in the Ottawa

918 Embayment (Oruche et al. 2019). The numbered excursions are fit to those in Unit 6

919 at Brent Crater (Fig. 5B). The correlation is supported by matching correlation of

920 Watertown-like facies in the Brent Crater and Deux Rivières outliers.

Draft

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Table 1. Carbonate lithofacies, related sedimentary features, fossils, and interpreted paleoenvironments Facies Sedimentary Features Fossils and Other Textural Details Paleonvironment(s)* LIMESTONE L1 Mudstone -a non-fossiliferous massive barren subtidal, low-energy; environmentally restricted?

-b fossil restricted dolomudstone nodules bivalves (whole, disarticulated) subtidal, low-energy; environmentally restricted?

-c dolomitic synsedimentary scarce ostracodes; Tymbochoos sinclairi; peritidal to subtidal (1); unstable substrate microfolds and faults lingulid brachiopod shells likely due to seismicity

-d sandy skeletal wavy-laminated bivalves, trilobites; < 10% siliciclastics subtidal, brackish?, shore-distal

-e skeletal horizontal burrows gastropods, bivalves, brachiopods, subtidal, marine, low energy bryozoans, trilobites

-f microbial lime mud rich; ostracodes (disarticulated) subtidal, low energy laminae, buildups Draft L2 Wackestone -a skeletal horizontal/sub-horizontal fragmental: crinoid ossicles, bivalve, subtidal, normal marine, low energy, warm water; burrows; transported ostracode, trilobite, gastropod, bryozoan, proximal to ooid shoal; fragmentation related to ooids; trace quartz grains T. sinclairi predation?

-b skeletal hardgrounds; vertical and crinoid ossicles, bryozoans, bivalves, subtidal, normal marine, episodic wave-planation sub-vertical burrows brachiopods, ostracodes, Vermiporella sp. and seafloor marine lithification (2, 3)

-c greenish massive fragmented trilobites, bryozoans, subtidal, marine, low-energy ostracodes, and brachiopods

L3 Packstone -a peloidal horizontal burrows scarce trilobites subtidal, marine, agitated

-b coral-bearing fragments: Tetradium, bivalves, ostracodes subtidal, marine, shoal or carbonate sand flat (3)

-c skeletal (diverse) medium-bedded brachiopods, ostracodes, bivalves, crinoids, subtidal, normal marine, moderate-energy, trilobites, gastropods, cyanobacteria, photic zone and Vermiporella sp.

-d sandy skeletal 3D-burrow networks as above, without Vermiporella sp. subtidal, normal marine, shore-proximal

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-e peloidal/skeletal thin-bedded Vermiporella sp., crinoids, bryozoans, subtidal, normal marine, photic zone trilobites, ostracodes, and bivalves moderate energy, stable substrate

L4 Grainstone -a sandy skeletal thin-bedded; dolostone disarticulated: bivalves, brachiopods; subtidal, normal marine, high-energy, (glauconitic) fragments; quartz, feldspar ostracodes; blackened crinoid ossicles; shore-proximal; burial/exhumation heavy minerals

-b encrinite massive abundant crinoid ossicles, bivalve shells subtidal, normal marine, high-energy (2-4)

-c ooid-bearing thin-bedded ooids (radial, laminar cortices); gastropods, subtidal, normal marine high- to low energy (radial, laminar) bivalves, microbial laminae, bryozoans, : laminar cortex = higher energy and crinoid ossicles

-d oncolite-bearing thin-bedded, nodular brachiopods, crinoids, trilobites, bivalves, subtidal, normal marine, moderate-energy cyanobacteria, Vermiporella sp., bryozoans, L5 Skeletal float/rudstone bryozoans,Draft bivalves subtidal, marine, low-energy

DOLOSTONE D1 Dolomudstone -a silty thin-bedded, scarce brachiopods subtidal, marine, shore distal + horizontal burrows

-b sandy skeletal medium-bedded, Skolithos; blackened shells of ostracodes, subtidal, variable energy, shore-proximal; bivalves, trilobites, and bryozoans synsedimentary burial/exhumation

-c sandy skeletal medium-bedded scarce crinoid ossicles, rugose corals subtidal, marine, low energy;

-d skeletal medium-bedded disarticulated to fragmented shells of below fair-weather wave-base (5), brachiopods, gastropods, crinoid ossicles, normal marine bryozoans; prominent Cruziana ichnogenera

-e sandy skeletal coarsely-crystalline, crinoids, bryozoans, shells (indeterminate) subtidal, normal marine, low energy with crinoids thin bedded

-f pure dolomite thin bedded barren; no siliciclastics subtidal, marine, low energy

D2 Skeletal basement clasts subfacies-i: crinoid osscicles, bryozoans; i: subtidal, normal marine, shore proximal

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dolopackstone incorporated subfacies-ii: bryozoans, trilobites ii: subtidal, marine, shore proximal

D3 Dolograinstone -a sandy with medium-thick, fragmented: crinoid ossicles, bryozoans, subtidal, normal marine, high-energy; coated grains borizontal bedding bivalves, rugose corals, trilobites; coated grains (ooids)

-b cross-bedded, sandy foreset cross-beds as above subtidal, normal marine, high-energy; with coated grains or trough cross-beds cross-beds identify sand-wave or current shoal

D4 Crystalline Dolostone (no fine depositional fabric preserved) -a pure medium-bedded, ? (no depositional features preserved) fine to medium crystalline

-b calcitic thin-bedded; finely upright colonies of domal stromatoporoid subtidal, marine; no depositional features crystalline; hard and Tetradium fibratum? other than fossil colonies

D5 Lithic-Bearing Rudstone/Floatstone -a pebbly rudstone normal grading of whole bivalves peritidal? to subtidal, deposition basement clasts Draft with waning energy; shore proximal

-b lithoclastic skeletal basement clasts orthocones, bivalves, gastropods, subtidal, marine, shore-proximal rudstone/floatstone trilobites, bryozoans; rare crinoid ossicles

-c sandy skeletal normally graded crinoid ossicles, tabulate coral colonies, subtidal, normal marine, phases of waning energy

D6 Dolostone Breccia framework- and matrix- jig-saw to chaotic clast distribution; peritidal/subtidal, hypersaline?, shore-distal, support; monomictic; synsedimentary deformation of matrix unstable substrate due to seismicity (this study) or siltstone matrix stratification evaporite dissolution (6)

* reference to marine may include brackish conditions; shore-proximal versus shore-distal defines a measure of distance from influx of terrigenous siliciclastics; paleoenvironmental interpretations are based on the environmental compendium of Flügel (2010) with additional numbered references related to equivalent platform successions peripheral to the Canadian Shield: 1, Steele-Petrovich and Bolton (1988); 2, Grimwood et al. (1999); 3, Oruche et al. (2018); 4, Brookfield (1988); 5, MacEachern et al. (2010); 6, Lozej and Beales (1975a)

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Table 2. Siliciclastic lithofacies, related sedimentary features, fossils, and interpreted paleoenvironments Lithology Sedimentary Features Interpreted Paleonvironment* Cg Syenite-Gneiss Rudite -a breccia framework-support, oligomictic; clast diameter of < 1 m; subtidal, high-energy, marine; feldspathic, quartz arenite matrix; dolomite cement; individual and reworked coarse-grained regolith (1) locally clustered bivalves, also individuals; fragmented cryptostomid bryozoan fragments

-b conglomerate matrix-support, oligomictic; pebble-sized clasts; sandy dolostone subtidal, marine, shore-proximal matrix; gastropod shells (whole, fragmented)

S1 Arenite -a quartz biomodal: fine- and coarse-grained; pyritized coated grains subtidal, normal marine, high-energy (2)

-b feldspathic medium-bedded, planar-laminated; fine- to medium-grained; terrestrial? or shore-proximal; rapid deposition chlorite and kaolinite as cements

-c skeletal, feldspathic thin-bedded; bimodal: rounded and angular coarse-grained; subtidal, marine, high-energy, shore-proximal with whole to disarticulated bivalves;Draft orthocones, gastropods, and bryozoans

-d lithic, feldspathic wave-rippled and locally normal grading; fine- to medium-grained; depositional influx with waning energy; calcitic and dolomitic cements; no fossils recognized peritidal or subtidal, shore-proximal; fan-delta?

S2 Wacke -a lithic medium- to very coarse-grained; with basement and limestone clasts; terrestrial? to shore-proximal; rapid deposition quartz and feldspar; red and green mottling of matrix

-b feldspathic yellow-green, ferruginous, with some basement clasts; residual sediment (grus or regolith) (1) overlies nonconformity in paleodepression on Precambrian basement

M Mudrock -a grey/grey-brown shale no fossils; dolomitic low energy and siltstone

-b green shale/siltstone laminated to massive low energy

* reference to marine may include brackish conditions; numbered sources are: 1, Mignon and Thomas (2002), and 2, Flügel (2010)

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Table 3. Conodont taxa

Location Taxa Deux Rivières* Belodina compressa? (Branson and Mehl) (Unit 5) Curtognathus sp. Drepanoistodus suberectus (Branson and Mehl) Erismodus sp. Panderodus unicostatus (Branson and Mehl) Plectodina aculeata (Stauffer)

Brent Crater** Chirognathus duotactylus Branson and Mehl Curtognathus sp. Erismodus sp. Microcoelodus unicornis? Branson and Mehl Phragmodus influexus Stauffer

Owen Quarry* Curtognathus sp. (Unit 1) Drepanoistodus suberectus (Branson and Mehl) Erismodus sp. Plectodina aculeata Draft(Stauffer) * McCracken (2017); report provided by Kang and Dix (2020) ** Grahn and Ormö (1995)

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