Provenance analysis of the Dezadeash Formation (Jura- western … · 2019. 1. 3. · Draft 2 32...

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Provenance analysis of the Dezadeash Formation (Jura-Cretaceous), Yukon, Canada: Implications regarding a

linkage between the Wrangellia composite terrane and the western margin of Laurasia

Journal: Canadian Journal of Earth Sciences

Manuscript ID cjes-2017-0244.R2

Manuscript Type: Article

Date Submitted by the Author: 05-Sep-2018

Complete List of Authors: Lowey, Grant; Pilot Mountain

Keyword: Provenance, geochemistry, petrography, Dezadeash, Wrangellia

Is the invited manuscript for consideration in a Special

Issue? :Not applicable (regular submission)

https://mc06.manuscriptcentral.com/cjes-pubs

Canadian Journal of Earth Sciences

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10 Provenance analysis of the Dezadeash Formation (Jura-Cretaceous), Yukon, Canada:

11 Implications regarding a linkage between the Wrangellia composite terrane

12 and the western margin of Laurasia

1314151617181920 Grant W. Lowey

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24 P.O. Box 21254

25 Whitehorse, Yukon, Canada, Y1A 6R2

26 (E-mail: [email protected])

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30 Keywords Provenance, geochemistry, petrography, Dezadeash, Wrangellia, turbidite

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mailto:[email protected]

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32 Abstract: The Mesozoic convergence of the allochthonous Wrangellia composite terrane

33 (WCT) with the western margin of Laurasia coincided with the construction of the Chitina

34 magmatic arc on the WCT, and the dispersal of volcanic flows and sediment gravity flows

35 into an adjacent flysch basin. The basin, preserved as the Gravina-Nutzotin belt, includes

36 the Dezadeash Formation in southwest Yukon, the Nutzotin Mountains sequence in

37 southern Alaska, and the Gravina belt in southeastern Alaska. The Dezadeash Formation is

38 a submarine fan system comprising stacked channel-lobe transition and lobe deposits

39 interposed with overbank deposits. Conglomerate pebble-counts, sandstone point-counts,

40 detrital zircon ages, and major element, trace element, rare earth element, and Sm-Nd

41 isotopic geochemistry of sandstone, mudstone, and hemipelagite beds suggests that the

42 deposits consist mainly of first-cycle volcanogenic detritus shed from the undissected

43 Chitina arc, in addition to material eroded from the WCT. The arc was constructed of

44 undifferentiated magma sourced from the depleted mantel, as well as older crustal material

45 attributed to the WCT proxying for continental crust. The compositional provenance

46 results, together with published paleocurrent data for the Dezadeash Formation and

47 compositional and directional provenance indicators from the Nutzotin Mountains sequence

48 and Gravina belt, does not require a sediment source from Laurasia. The provenance record

49 is compatible with deposition of the Gravina-Nutzotin belt in a convergent plate margin

50 setting.

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52 Introduction

53 The Dezadeash Formation is part of the Gravina-Nutzotin belt (Berg et al., 1972),

54 an assemblage of Late Jurassic to Early Cretaceous volcanolithic turbidites up to 3000 m

55 thick with locally important interbedded conglomerate and volcanic rocks, that extends

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56 from southeastern Alaska, through southwestern Yukon, and into southern Alaska. It is

57 subdivided from south to north, into the Gravina belt, Dezadeash Formation, and Nutzotin

58 Mountains sequence (Fig.1). These assemblages are interpreted as submarine fan deposits

59 and submarine volcanic flows that unconformably overly the eastern margin of the

60 allochthonous Wrangellia composite terrane (WCT, ~Insular superterrane, Monger, 2014),

61 a microcontinent assembled in the paleo-Pacific Ocean (Beranek et al., 2014). The

62 Dezadeash Formation and Nutzotin Mountains sequence are interpreted as the same

63 stratigraphic unit that was dismembered and displaced ~370 km by the Denali fault system

64 (Eisbacher, 1976; Lowey, 1998); their geographic continuity with the Gravina belt is

65 uncertain, but all three assemblages were likely deposited in the same overall tectonic

66 setting (Berg et al., 1972). However, the tectonic setting is controversial due to

67 uncertainties regarding the timing and location of collision of the WCT with Laurasia

68 (McCelland et al., 1992; Monger et al., 1994), the number of volcanic arcs present and their

69 polarity (Nokleberg and Richter, 2007; Gehrels et al., 2009), and whether the margin of

70 Laurasia contributed sediment to the Gravina-Nutzotin belt (Berg et al., 1972; Nokleberg et

71 al., 1985; Kapp and Gehrels, 1998; McClelland and Mattinson, 2000).

72 A compositional provenance link between the Gravina-Nutzotin belt and Laurasia

73 was proposed by Kapp and Gehrels (1998) who concluded that 380-310 and >900 Ma

74 detrital zircons from the Gravina belt were sourced from the continental margin of Laurasia

75 (i.e., Yukon-Tanana and Stikine terranes, Fig. 1). However, Hults et al. (2013) argued that

76 zircons of this age were derived from the WCT, and Yokelson et al. (2015) proposed that

77 detrital zircons from the 'western' Gravina belt were also sourced from the west (i.e., the

78 WCT). A compositional provenance link between the Gravina-Nutzotin belt and Laurasia

79 was also proposed by Berg et al. (1972) and Richter (1976) who suggested that clasts of

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80 white vein quartz and metamorphic rocks from the Nutzotin Mountains sequence were

81 derived from Laurasia (i.e., Yukon-Tanana terrane). These observations though, were based

82 on regional mapping over 40 years ago and additional mapping (e.g., Dodds and Campbell,

83 1992), together with sedimentological studies incorporating paleocurrent measurements

84 (e.g., Eisbacher, 1976; Kozinski, 1985; Lowey, 1980, 1998; Cohen, 1992; Manuszak,

85 2000), have cast doubt on a Laurasian source for the clasts. Furthermore, Manuszak et al.

86 (2007) concluded that their study was unable to establish a direct unequivocal provenance

87 link between the Nutzotin Mountains sequence and Laurasia.

88 The Dezadeash Formation is presently located further east than the Nutzotin

89 Mountains sequence, implying that it may have been closer to Laurasia and therefore more

90 likely to contain a record of sediment derived from the continental margin. On account of

91 the potential limitations of provenance analysis, such as non-unique sediment sources,

92 internal variability within a single source area, incomplete characterization of potential

93 sources, sediment recycling, climatic and erosion effects, grain attrition during transport,

94 hydraulic sorting, and post-depositional alteration (Rollinson, 1993; McLennan et al., 2003;

95 Nie et al., 2012), this paper presents the results of an integrated provenance analysis of the

96 Dezadeash Formation, including pebble-counts of conglomerate beds, radiometric and

97 fossil dating of conglomerate clasts, grain point-counts of thin sections of sandstones, U-Pb

98 dating of detrital zircons from sandstones, and whole-rock geochemisty of sandstone,

99 mudstone, and hemipelagite beds, including major elements, trace elements, rare earth

100 elements, and Sm-Nd isotopes. Paleocurrent data from the Gravina-Nutzotin belt are also

101 reviewed. The primary aim is to characterize the lithological and geochemical composition

102 of the Dezadeash Formation, thereby facilitating comparisons with other Jura-Cretaceous

103 flysch basins exposed along the western margin of North America. Secondary aims are to

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104 use the new compositional dataset to constrain the provenance and tectonic setting of the

105 Dezadeash Formation.

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107 Geologic Setting

108 The WCT (Fig. 1) is a composite block of three amalgamated tectonostratigraphic

109 terranes referred to as the Alexander, Wrangellia, and Peninsular terranes (Plafker and

110 Berg, 1994). The Alexander terrane includes a basement of Neoproterozoic to early

111 Paleozoic island arc-related volcanic and sedimentary rocks (Nokleberg et al., 1994;

112 Beranek et al., 2012), and also late Paleozoic island arc-related volcanic and sedimentary

113 rocks. The Wrangellia terrane consists mainly of late Paleozoic to early Mesozoic island

114 arc-related volcanic and sedimentary rocks. The Peninsular terrane consists of an

115 assemblage of Mesozoic arc-related volcanic rocks (Nokleberg et al., 1994). The three

116 terranes represent successively higher structural and stratigraphic successions from

117 southeast to northwest (Nokleberg et al., 1994). The Alexander and Wrangellia terranes

118 were contiguous during late Paleozoic time, based on Pennsylvanian-age plutons that

119 intrude both terranes (Gardner et al., 1988). The Peninsular terrane is interpreted to have

120 collided in Late Jurassic time with either the western margin of Laurasia (the Yukon

121 composite terrane), or the combined Alexander-Wrangellia terrane (Clift et al., 2005;

122 Beranek et al., 2014). The WCT, interpreted as part of an obliquely converging oceanic

123 plateau (Greene et al., 2010), was emplaced against the margin of Laurasia during Middle

124 Jurassic to mid-Cretaceous time (Monger et al., 1982; McClelland et al., 1992; Nokleberg

125 et al., 1994).

126 The Yukon composite terrane (YTC, ~Intermontane superterrane, Monger, 2014)

127 (Fig. 1) refers to the polymetamorphosed and polydeformed Yukon-Tanana, Slide

128 Mountain, Cache Creek, Quesnellia, and Stikinia terranes (Wheeler and McFeely, 1991;

129 Monger, 2014). The YTC includes a substrate of Proterozoic to Paleozoic metasedimentary

130 and mafic meta-igneous rocks, overlain by an assemblage of Devonian-Mississippian arc-

131 related volcanic and sedimentary rocks (Plafker and Berg, 1994; Nelson et al., 2013). The

132 YTC was rifted from the ancient margin of North America in middle Paleozoic time,

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133 resulting in the formation of the oceanic Slide Mountain terrane, and subsequently re-

134 attached to North America in the latest Paleozoic (Nelson et al., 2013). The Cache Creek

135 terrane is a subduction-related assemblage that is flanked by late Paleozoic to early

136 Mesozoic volcanic arc rocks belonging to Quesnellia and Stikinia (Goldfarb et al., 2013;

137 Monger, 2014). Final accretion of the YTC to the western margin of Laurentia occurred in

138 mid-Jurassic to Cretaceous time (Monger et al., 1982; Monger and Journeay, 1994; Nelson

139 et al., 2013).

140 Several Mesozoic magmatic arcs, termed the Talkeetna (~205-155 Ma; Onstott et

141 al., 1989; Palfy et al., 1999; Rioux et al., 2003, 2007), Chitina (~160-140 Ma; Plafker et al.,

142 1989; Nokleberg et al., 1994; Roeske et al., 1991, 2003), and Chisana (~130-110 Ma; Short

143 et al, 2005; Snyder et al., 2005) erupted across the WCT from west to east. The Chitina arc

144 occurs between the Talkeetna and Chisana arcs in both time and space. Volcanic rocks of

145 the Chitina arc are preserved in the Gravina belt, but not in the Nutzotin Mountains

146 sequence or Dezadeash Formation, although volcaniclastic rocks occur in the Dezadeash

147 Formation. The volcaniclastic rocks in the Dezadeash Formation consist of fine-to medium-

148 grained vitric to crystal tuffs interpreted as resedimented syn-eruptive volcaniclastic gravity

149 flow deposits (Lowey, 2011). A U-Pb zircon age (149.4 + 0.3 Ma) indicates the

150 volcaniclastic rocks are contemporaneous with the Chitina arc, and Sm-Nd systematics

151 suggest the volcaniclastic rocks represent mixing of a depleted mantle source and an older

152 crustal source (Lowey, 2011). Furthermore, a variety of tectonic discriminant diagrams

153 show the volcaniclastic rocks have a continental arc signature, which Lowey (2011)

154 attributed to the WCT proxying for continental crust.

155 The Gravina-Nutzotin belt (Fig. 1) depositionally overlies the Alexander and

156 Wrangellia terranes (Jones et al., 1982). It consists of the Dezadeash Formation located

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157 near the middle of the belt, the Nutzotin Mountains sequence at the northern end of the belt,

158 and the Gravina belt at the southern end of the belt (Fig. 2). The Dezadeash Formation is

159 approximately 3000 m thick and consists of thin- to thick-bedded turbidites and massive

160 sandstone with minor amounts of conglomerate (containing limestone clasts up to ~10 m in

161 exposed longest dimensions), volcaniclastic rocks, and hemipelagic lime mudstone

162 (Eisbacher, 1976; Lowey, 1992, 2007). The strata are unmetamorphosed to regionally

163 metamorphosed up to subgreenschist facies (laumontite-prehnite-quartz; Dodds and

164 Campbell, 1992). The Dezadeash Formation is Late Jurassic (Oxfordian) to Early

165 Cretaceous (Valanginian) in age based on collections of the bivalve Buchia (Eisbacher,

166 1976), and unnconformably overlies the Wrangellia terrane, specifically Triassic volcanic,

167 volcaniclastic, and carbonate rocks belonging to the Nikolai Formation, McCarthy

168 Formation, and Chitistone and Nisina Limestone (Dodds and Campbell, 1992). Based on

169 detailed lithofacies analysis, the Dezadeash Formation represents mainly the middle and

170 lower subdivisions of a point-source, mud/sand-rich submarine fan (Lowey, 2007) that was

171 derived from the west (Eisbacher, 1976). The Dezadeash Formation is overlain

172 unconformably by Paleogene clastic and volcaniclastic rocks of the Amphitheater

173 Formation (Eisbacher, 1976). Immediately east of the Dezadeash Formation is the Kluane

174 Schist (Fig. 1), a 160 km long belt of mainly mica-quartz schist of uncertain age and origin.

175 Eisbacher (1976) proposed that the Kluane Schist represents the higher grade

176 metamorphosed Dezadeash Formation, but zircon geochronology by Stanley (2012)

177 suggests that the protolith of the Kluane Schist may be younger (i.e., Late Cretaceous) than

178 the Dezadeash Formation.

179 The Nutzotin Mountains sequence (Fig. 2) is up to 3000 m thick and consists

180 mainly of low-grade metamorphosed thin-bedded turbidites with minor amounts of massive

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181 sandstone, matrix-supported conglomerate (containing limestone clasts up to ~10 m in

182 exposed longest dimensions), and hemipelagite beds (Berg et al., 1972; Richter, 1976;

183 Kozinski, 1985; Manuszak et al., 2007). The strata are Late Jurassic (Tithonian) to Early

184 Cretaceous (Valanginian) in age based on the bivalve Buchia, and unconformably overlies

185 the Wrangellia terrane (Manuszak and Ridgway, 2000). The Nutzotin Mountains sequence

186 is interpreted as westerly sourced, distal to proximal submarine fan deposits that grade

187 upward into shelf deposits (Kozinski, 1985; Manuszak et al., 2007). The Nutzotin

188 Mountains sequence is conformably overlain by the Chisana Formation, a ~3000 m thick

189 assemblage of volcanic-lithic breccia, basaltic-andesite flows, volcaniclastic rocks, and

190 mudstone (Berg et al., 1972; Richter, 1976; Barker, 1987). The Chisana Formation is

191 interpreted to have been deposited proximal to volcanic vents on subaqueous slopes of the

192 contemporaneous proto-continental, or intraoceanic Chisana arc (Short et al., 2005).

193 Eisbacher (1976) proposed that the Dezadeash Formation and Nutzotin Mountains

194 sequence represent the same strata that were dismembered and displaced by the Denali fault

195 system (Eisbacher, 1976). The Denali fault system is one of the main transcurrent faults in

196 the northern part of the North American Cordillera, along which ~370 km of dextral slip

197 occurred since the Early Cretaceous (Clague, 1979; Lowey, 1998, and references therein).

198 Sedimentologic and stratigraphic studies by Kozinski (1985), Manuszak (2000), and

199 Manuszak and Ridgway (2000) on the Nutzotin Mountains sequence corroborates this

200 interpretation.

201 The Gravina belt comprises the Seymour Canal Formation (Fig.2), Douglas Island

202 Volcanics and Brothers Volcanics, and the Treadwell Formation (Gehrels, 2000). The

203 Seymor Canal Formation is ~1800 m thick and consists of sandstone and mudstone

204 turbidites with minor amounts of conglomerate, volcanic rocks, and volcaniclastic rocks

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205 (McClelland et al., 1991; Cohen, 1992; Gehrels, 2000). Strata are regionally

206 metamorphosed to zeolite, prehnite-pumpellyite, and lower-greenschist facies in the north,

207 increasing to greenschist facies in the south (Cohen and Lundberg, 1993). The Seymour

208 Canal Formation is Late Jurassic (Oxfordian) to Early Cretaceous (Albian) in age and

209 unconformably overlies the Alexander terrane (Cohen, 1992; Cohen and Lundberg, 1992).

210 The strata are interpreted as upper and middle submarine fan sediments sourced from the

211 west (Cohen, 1992; Gehrels, 2000). The Seymor Canal Formation is conformably overlain

212 by basalt breccia and pillowed volcanic flows of the Douglas Island Volcanics and Brothers

213 Volcanics, which are conformably overlain by sandstone, mudstone, and conglomerate

214 beds assigned to the Treadwell Formation (Gehrels, 2000). The Douglas Island Volcanics,

215 Brothers Volcanics, and Treadwell Formation are related to the Cretaceous Chisana arc

216 (Gehrels, 2000).

217 Near the southernmost part of the Gravina belt, an assemblage of greenschist to

218 amphibolite facies phyllite, schist, and metaconglomerate originally interpreted as part of

219 the Taku terrane was reinterpreted by Rubin and Saleeby (1991) as part of the Gravina belt

220 and named the 'Gravina sequence'. Since the tectonic affinity of these rocks is the subject of

221 a recent debate (Lowey, 2017) they are not considered further.

222

223 Methods

224 This study is based on 16,335 m of measured strata from 75 sections throughout the

225 Dezadeash Formation (Fig. 3, Supplementary Table S1). Approximately 200 samples

226 representative of the various lithofacies present were collected from these sections (Table

227 1). According to Lowey (2007), the lithofacies display no apparent overall vertical trend in

228 depositional architecture, interpreted as laterally and vertically repetitive submarine fan

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229 channel-lobe transition and lobe deposits separated by overbank deposits (Lowey, 2007),

230 and a subset of samples from the 200 initially collected were selected for analysis.

231 Conglomerate pebble-counts were performed on poorly sorted or disorganized

232 gravelly mudstone beds (Fig. 4A). The beds range from 3 to 23 m in thickness, and only

233 three conglomerate pebble-counts were undertaken due to the scarcity of conglomerate in

234 the Dezadeash Formation (~1.3 % of all lithofacies, based on the vertical percentage of

235 strata in all measured sections; Lowey, 2007). The pebble-counts consisted of identifying

236 the lithology of at least 100 clasts >1 cm long in a conglomerate bed that was encountered

237 during measuring a section. In addition to the pebble-counts, conglomerate clasts were

238 collected for K-Ar age determination and microfossil analysis. One diorite pebble was

239 selected for hornblende K-Ar age determination. The analysis was performed at Geochron

240 Laboratories, Chelmsford, Massachusetts. The sample was crushed and the -80/+200 mesh

241 fraction was used for mineral separation. Hornblende concentrate was separated by heavy

242 liquids, followed by washing with dilute HF and then HNO3 . K was analyzed by replicate

243 atomic absorption spectrophotometric methods, and Ar was analyzed by standard isotopic

244 dilution techniques using an 38Ar-enriched spike. Standard calibration methods were used

245 for the 38Ar tracer, and inter-laboratory standards were checked on a routine basis for both

246 K and Ar determinations. One limestone clast was selected for conodont analysis and

247 separated using standard acetic acid processing techniques by the Geological Survey of

248 Canada, Vancouver, British Columbia. A discussion of the procedure is provided by Harris

249 and Sweet (1989) and Orchard and Foster (1991).

250 Thirty samples of medium-grained sandstone, including thick- to medium-bedded

251 sandstone (Fig. 4B) and the sandstone portion of very thick- to thick-bedded sandstone-

252 mudstone couplets (Fig. 4C) were selected for point-count analysis. Standard thin sections,

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253 half of which were impregnated with blue epoxy, and standard off-cuts, all of which were

254 stained for potassium feldspars, were prepared by Vancouver Petrographics Ltd., Langley,

255 British Columbia. The thin sections were examined by transmitted light microscopy with a

256 petrographic microscope. Between 300-400 framework grains were identified in each thin

257 section using a modified Gazzi-Dickinson method (Dickinson, 1985). The Gazzi-Dickinson

258 method was modified such that sedimentary chert grains and sedimentary carbonate grains

259 were counted as framework lithic fragments due to their potential importance in

260 determining provenance (Zuffa, 1980; Mack, 1984). The sedimentary chert grains generally

261 account for <3% of the framework mode and sedimentary carbonate grains generally

262 represent <4% of the framework mode, and so their inclusion in the framework mode does

263 not significantly affect the position of sandstone compositions plotted on tectonic

264 discrimination diagrams of Dickinson and Suczek (1979). Matrix and cement were not

265 counted. In addition, 2 medium-grained sandstone samples (including one from thick- to

266 medium-bedded sandstone and one from the sandstone portion of very thick- to thick-

267 bedded sandstone-mudstone couplets), each weighing ~15 kg, were selected for U-Pb

268 isotopic analysis of detrital zircons. A total of ~200 detrital zircons were analyzed using

269 laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at the Arizona

270 LaserChron Center, Tucson, Arizona, utilizing methods described by Gehrels et al. (2008).

271 Isotope data and the weighted mean of the 207Pb/206Pb dates were calculated using the

272 program of Ludwig (2008).

273 A total of 41 samples were selected for whole rock geochemical analysis, including

274 29 sandstones (the sandstone matrix from disorganized conglomerate; the sandstone matrix

275 from pebbly sandstone; thick- to medium-bedded sandstone; and the sandstone portion of

276 very thick- to thick-bedded sandstone-mudstone couplets), seven mudstones (the mudstone

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277 portion of thin-bedded sandstone-mudstone couplets, Fig. 4D; thick siltstone-mudstone

278 laminae; and structureless mudstone), and five hemipelagite beds (lime mudstone, Fig. 4E).

279 Major element concentrations were determined by X-ray Fluorescence (XRF), trace

280 element and rare earth element (REE) abundances were measured by fusion inductively

281 coupled plasma-mass spectroscopy (ICP-MS), and Sc was analyzed by instrument neutron

282 activation analysis (INAA), at Activation Laboratories, Ancaster, Ontario. Analytical error

283 for the XRF method is <1% for major elements; for trace elements, precision is better than

284 6% and analytical error is better than 5%. Various trace-element diagrams were plotted

285 using the Igpet program by Carr (2000).

286 A total of 17 samples were selected for Sm-Nd isotopic analysis, including six

287 sandstones (the sandstone matrix from pebbly sandstones; thick- to medium-bedded

288 sandstone; and the sandstone portion of very thick- to thick-bedded sandstone-mudstone

289 couplets), five mudstones (the mudstone portion of thin-bedded sandstone-mudstone

290 couplets; and structureless mudstone), and six hemipelagite beds (lime mudstone). The Sm-

291 Nd isotopic analysis was performed on a Triton-MC mass-spectrometer by Activation

292 Laboratories, Ancaster, Ontario. Rock powder was dissolved in a mixture of HF, HNO3,

293 and HClO4, and before decomposition the sample was mixed with a 149Sm-146Nd spiked

294 solution. Sm and Nd were separated by extraction chromatography on HDEHP covered

295 Teflon powder. Total blanks are 0.1-0.2 ng for Sm and 0.1-0.5 ng for Nd. Accuracy of the

296 measurements of Sm and Nd are ±0.5% and 147Sm/144Nd ±0.5%. 143Nd/144Nd ratios are

297 relative to the value of 0.511860 for the La Jolla standard. During the work the weighted

298 average of 10 La Jolla Nd-standard runs yielded 0.511874±10 (2s) for 143Nd/144Nd, using

299 the depleted mantle value of 0.7219 for 146Nd/144Nd to normalize (Rollinson, 1993).

300

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301 Directional Provenance Indicators

302 Review

303 The most comprehensive directional provenance analysis of the Gravina-Nutzotin

304 belt was by Eisbacher (1976) who measured the orientation of >500 sole marks, cross

305 laminations, and slump folds throughout the Dezadeash Formation (Fig. 5). Eisbacher

306 (1976) corrected paleocurrent measurements for tectonic dip and plunge. Detailed mapping

307 and structural analysis did not reveal any potentially rotated fault blocks that may have

308 affected paleocurrent trends (Eisbacher, 1976). Eisbacher (1976) noted a weak fan-like

309 arrangement to the paleocurrent data and suggested that the overall paleoflow direction was

310 to the northeast. Based on the measurement of 24 sole marks and cross laminations

311 corrected for dip and plunge from the Dezadeash Formation, Lowey (1980) documented a

312 mean paleoflow direction to the northeast for stacked channel-lobe transition deposits and

313 lobe deposits, whereas overbank deposits displayed a mean paleoflow direction to the east.

314 The trend of a channelized debris flow deposit containing limestone clasts up to ~10 m in

315 exposed longest dimensions from the Dezadeash Formation was also determined to be to

316 the east (Lowey, 1998), although the direction was not corrected for dip and plunge because

317 the trend was determined from a ~2 km wide debris flow channel exposed on opposite side

318 of a mountain valley, and mapping by Dodds and Campbell (1992) did not show any

319 potentially rotated fault blocks.

320 In the southern part of the Nutzotin Mountains sequence, Koziski (1985)

321 documented northwest and northeast paleoflow directions based on the measurement of 212

322 cross laminations (Fig. 5); a northeast-southwest direction was recorded from a single sole

323 mark. Kozinski (1985) rotated bedding back to horizontal, but did not correct for plunge

324 because fold axes are approximately horizontal. According to Ramsey (1961), plunges less

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325 <25º can generally be ignored. In the middle part of the Nutzotin Mountains sequence

326 outcrop belt, Manuszak et al. (2007) determined a northeastward paleoflow direction based

327 on the measurement of 24 clast imbrications, whereas in the northern part of the belt, the

328 measurement of 89 clast imbrications indicated eastern and southeastern paleoflow

329 directions, and the measurement of 108 cross laminations revealed eastern sediment

330 dispersal (Manuszak et al., 2007). Manuszak et al. (2007) restored paleocurrent data to

331 horizontal based on bedding orientation. Structural analysis and mapping did not reveal any

332 potentially rotated fault blocks that may have affected paleocurrent trends (Manuszak et al.,

333 2007).

334 In the northern part of the Gravina belt, Cohen (1992) obtained only limited

335 paleocurrent data. A southwest and northwest paleoflow direction was determined from the

336 measurement of 28 cross laminations (Fig. 5), a southeast direction was based on the

337 orientation of five sole marks, and a northeast direction was obtained from the

338 measurement of five slump folds (Cohen, 1992). Cohen (1992) restored paleocurrents to

339 their original orientation and did not observe any rotated fault blocks that may have

340 affected paleocurrent trends.

341

342 Interpretations

343 The available paleocurrent indicators demonstrate consistent eastward-directed

344 sediment transport, suggesting that Gravina-Nutzotin belt strata was sourced from the west.

345 However, throughout the Gravina-Nutzotin belt imbricated clasts and cross laminations

346 tend to show a greater variance in paleocurrent directions compared to that of sole marks.

347 This may be attributed to the difficulty associated with obtaining accurate measurements

348 (only apparent directions of imbrication or cross lamination are measured unless

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349 exceptional, three-dimensional exposures exist; Potter and Pettijohn, 1977), turbulence or

350 variations in flow direction associated with a single turbidity current (Dzulynski and

351 Walton, 1965), and Coriolis forces deflecting overbank turbidity currents to the right

352 (looking down-channel) in the Northern Hemisphere (Wells and Cossu, 2013).

353 Furthermore, terranes in southern Alaska were likely rotated counterclockwise when

354 transported along arcuate faults such as the Denali fault system (Glen, 2004); reversing this

355 rotation brings paleocurrent orientations measured from the Nutzotin Mountains sequence

356 into closer alignment with those from the Dezadeash Formation.

357

358 Compositional Provenance Indicators

359 Pebble-count Analysis and Age of Conglomerate Clasts

360 Results

361 Raw pebble-count data is provided in Supplementary Table S2 and re-calculated

362 pebble-count data is summarized in Table 2. Conglomerates are characterized by a

363 dominance of volcanic and igneous mafic clasts (andesite, rhyolite, and gabbro). Other

364 clasts, in order of decreasing abundance, include limestone, diorite, chert, mudstone,

365 granite, and quartz. On the tectonic discriminant diagram of Cox and Lowe (1995), the

366 conglomerate compositions of the Dezadeash Formation plot in the mixed provenance and

367 volcanic arcs fields (Fig. 6A), whereas on the Plutonic-Volcanic-Sedimentary (P-V-S) clast

368 diagram by Dickie and Hein (1995), they plot in the arc flank field, or undissected arc (Fig.

369 6B). A hornblende K-Ar age of 144 ± 4 Ma was obtained from the diorite pebble (Table 3),

370 and based on conodonts, a Triassic (Late Norian) age was obtained from the limestone

371 cobble (Supplementary Table S3).

372

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373 Interpretations

374 Conglomerate clast compositions suggest derivation from a predominantly volcanic

375 source terrane with subordinate plutonic and sedimentary rocks, and minor vein quartz.

376 Conglomerate compositions plotted on the P-S-V tectonic discriminant diagram of Dickie

377 and Hein (1995) suggests an undissected arc provenance (Fig. 6B). Conglomerate

378 compositions from the Nutzotin Mountains sequence and Gravina belt overlap those of the

379 Dezadeash Formation, suggesting a similar tectonic setting.

380

381 Point-count Analysis

382 Results

383 Sandstone point-count parameters are summarized in Table 4. Raw point-count data

384 are provided in Supplementary Table S4 and re-calculated point-count data are shown in

385 Table 5. Although thick- to medium-bedded sandstones and the sandstone portion of very

386 thick- to thick-bedded sandstone-mudstone couplets were point-counted separately, there is

387 no significant difference between the detrital modes of these two lithofacies, and so they

388 are discussed as one group.

389 Sandstones are characterized by a dominance of lithic fragments (mainly volcanic)

390 compared to either quartz or feldspar (~Q12F26L62). Lithic fragments are dominated by

391 volcanic grains displaying mainly felsitic (Lvf) and lathwork (Lvl) textures. Minor amounts

392 of volcanic grains with microlitic textures (Lvm) are also present. Sedimentary lithic grains

393 are a minor component in the sandstones, and include chert (Lsc, with several grains

394 containing what appear to be radiolarian tests and spines infilled with microquartz),

395 limestone (Lsl, mainly lime micrite and recrystallized carbonate grains, with several

396 skeletal fragments of brachiopods, bryozoans and foraminifers), and mudstone (Lsm). Rare

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397 metamorphic lithic fragments of phyllite (Lmp) and schist (Lms) are also present. The ratio

398 of volcanic lithic grains to total lithic grains (Lv/L) ranges from 0.82 - 0.99, but is mostly >

399 0.90. Feldspar fragments are dominated by plagioclase grains (Fp) that display various

400 types of twinning, with Carlsbad+albite polysynthetic twinning the most common. The

401 plagioclase composition is consistently oligioclase (An19-21, based on the Michel-Levy

402 method). Potassium feldspar grains (Pk) are a minor component of the sandstones, and are

403 dominated by untwined orthoclase. Rare microcline grains displaying 'grid' or 'tartan'

404 twinning (i.e., combined albite+percline twinning) are also present. The ratio of plagioclase

405 to total feldspars (P/F) ranges from 0.68-1.00, but is mostly >0.80. Quartz fragments are

406 dominated by monocrystalline quartz grains (Qm) that are predominantly circular to

407 elliptical in shape, subangular to subrounded, and display non-undulose extinction. Rare

408 shard-like quartz grains and embayed quartz grains are also present. Polycrystalline quartz

409 grains (Qp) are a minor component of the sandstones, and consist mostly irregular-shaped

410 crystal aggregates in which individual crystals display undulose extinction and sutured

411 intercrystalline boundaries.

412 Other non-opaque grains not included in the point-counting (and accounting for

413 <1% of all grains) include clinopyroxene, orthopyroxene, hornblende, sphene, zircon,

414 biotite, and muscovite, in order of decreasing abundance. Opaque minerals were also

415 observed; they were also not included in the point-counting and also account for <1% of all

416 grains. The opaque minerals include magnetite, pyrite, limonite, and several orthopyroxene-

417 Fe-Ti oxide grains (magnetite and/or ilmenite ?) displaying symplectitic texture (a wormy,

418 irregular intergrowth; Barton and Gaans, 1988). Authigenic chlorite, sericite, laumontite,

419 natrolite, pumpellyite, prehnite, and irregular patches and veinlets of calcite are also

420 present.

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421 On the Qt-F-L tectonic discriminant diagram of Dickinson et al. (1983), sandstones

422 plot in the undissected arc and transitional arc fields (Fig.7A). On the Q-P-K tectonic

423 discriminant diagram of Dickinson and Suczek (1979), they plot in the magmatic arc field

424 (Fig.7B), whereas on the Qp-Ls-Lv diagram of Dickinson and Suczek (1979), they plot in

425 the arc orogen field (Fig. 8A); and on the Lm-Ls-Lv diagram Marsaglia and Ingersoll

426 (1992), they plot in the intraoceanic and continental arc fields (Fig. 8B).

427

428 Interpretations

429 Sandstone compositions plotted on the Qt-F-L discriminant diagram of Dickinson et

430 al. (1983) suggest an undissected to transitional arc (Fig. 7A); high ratios of P/F (~>0.8)

431 and Lv/L (~>0.9) favor an undissected arc (Ingersoll and Eastman, 2007). Sandstone

432 compositions plotted on the Lm-Ls-Lv tectonic discriminant diagram of Marsaglia and

433 Ingersoll (1992) suggest an intraoceanic to continental arc provenance (Fig. 8B). Marsaglia

434 and Ingersoll (1992) define a continental arc as one that has a basement of granitic rocks

435 and/or accreted terranes. Sandstone compositions from the Nutzotin Mountains sequence

436 and Gravina belt overlap those of the Dezadeash Formation (Figs. 7A, 7B, 8A, and 8B),

437 suggesting a similar tectonic setting.

438

439 Zircon Analysis

440 Results

441 Raw detrital zircon data are provided in Supplementary Table S5. Results of the analyses

442 are summarized in Pb/U concordia diagrams (Fig. 9) and in relative probability plots (Fig.

443 10). The separated zircons were generally colorless, euhedral prismatic crystals without

444 visible cores or zoning. Although detrital zircon ages range from ~ 2111-145 Ma (2112-148

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445 Ma for sample GL74A, and 2187-145 Ma for sample GL74B), only one grain is Paleozoic

446 in age and only five are Precambrian in age, resulting in a total distribution of 97%

447 Mesozoic, 0.5 % Paleozoic and 2.5% Precambrian ages (~M97 P0.5 Pc2.5). The detrital zircon

448 age data reveal concordant to slightly discordant Mesozoic age zircons, with the majority

449 between ~165-150 Ma, a dominant age mode at ~157 Ma, and subordinate age modes at

450 ~170, ~180 Ma and ~188 Ma. The maximum deposition age (MDA), determined by taking

451 the weighted mean age of three or more zircons that make up the youngest grain cluster

452 (Dickinson and Gehrels, 2009), is 148 Ma for sample GL74A and 147 Ma for sample

453 GL74B. Figure 11 provides a summary of detrital zircon data for the Dezadeash Formation

454 compared to other strata from the Gravina-Nutzotin belt and terranes in the Northern

455 Cordillera.

456

457 Interpretations

458 Calculated MDAs for the Dezadeash Formation are close to the ~149 Ma U-Pb

459 zircon age from a resedimented syn-eruptive tuff in the Dezadeash Formation (Lowey,

460 2011), and support the interpretation based on marine fossils that the Dezadeash Formation

461 is Late Jurassic (Oxfordian) to Early Cretaceous (Valanginian) in age (Eisbacher, 1976).

462 The detrital zircon age spectra of the Dezadeash Formation is dominated by Late Jurassic

463 grains (dominant age mode ~157 Ma), consistent with a source from an active volcanic arc,

464 most likely the Chitina arc (active ~160-140 Ma, Plafker et al., 1989; Roeske et al., 2003).

465 The detrital zircon age spectra from the Dezadeash Formation is similar to that

466 reported from the Nutzotin Mountains sequence (Manuszak et al., 2007; Hults et al, 2013)

467 and Gravina Belt (Kapp and Gehrels, 1998; Yokelson et al., 2015). Based on one sample

468 from the Nutzotin Mountains sequence, Hults et al. (2013) reported that detrital zircon ages

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469 range from 1539-132 Ma, with a dominant age mode between 170-140 Ma, a subordinate

470 age mode between 451-384 Ma, and several Precambrian grains, with an average

471 distribution of detrital zircon ages of ~M92 P6 Pc2; and based on one sample from the

472 Nutzotin Mountains sequence, Manuszak et al. (2007) reported that detrital zircon ages

473 range from 177-136 Ma, with a dominant age mode between 150-145 Ma, a subordinate

474 age mode between 176-164 Ma, and an average distribution of detrital zircon ages of ~M100

475 P0 Pc0. Yokelson et al. (2015) reported detrital zircon age spectra from seven samples of the

476 Gravina belt that were combined with results from five samples previously reported by

477 Kapp and Gehrels (1998). In the lowermost strata of the Gravina belt (specifically the base

478 of the Seymour Canal Formation), 'Fanshaw' samples contain a dominant age mode of 147

479 Ma, subordinate age modes of 331 Ma and 428 Ma, and four Precambrian grains (Yokelson

480 et al., 2015). In the middle strata of the Gravina belt (specifically the top of the Seymour

481 Canal Formation), 'Fort Point' samples reveal dominant age modes of 116 and 432 Ma, a

482 subordinate age mode of 360 Ma, and five Precambrian grains (Yokelson et al., 2015). And

483 in the uppermost strata of the Gravina belt (specifically the Treadwell Formation), 'Berners

484 Bay' samples contain a dominant age mode of 154 Ma, subordinate age modes of 119, 426,

485 and 445 Ma, and ten Precambrian grains (Yokelson et al., 2015). In addition, 'Pybus Bay'

486 samples from either the middle of the Gravina belt strata (specifically the top of the

487 Seymour Canal Formation according to Kapp and Gehrels, 1998), or from the from the base

488 of the Gravina belt strata (specifically the base of the Seymour Canal Formation according

489 to Yokelson et al., 2015), reveal a single dominant age mode of 147 Ma, a couple of

490 Paleozoic grains, and no Precambrian grains, with an average distribution of detrital zircon

491 ages of ~M100 P<1Pc0 (Yokelson et al., 2015).

492

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493 The detrital zircon age spectra of the Dezadeash Formation, Nutzotin Mountains

494 sequence and Gravina belt are all characterized by a dominant Late Jurassic to Early

495 Cretaceous age mode, variable amounts of Paleozoic grains or no Paleozoic grains, and

496 several Precambrian grains or no Precambrian grains. Hults et al. (2013) proposed that this

497 'southern flysch belt' (in addition to several unnamed units in Alaska), with an overall

498 average distribution of detrital zircon ages of ~M94 P1 Pc5, reflects derivation from the

499 Chitina arc and the WCT, and is distinctly different from their 'northern flysch belt', which

500 includes the Cretaceous Kahiltna and Kuskokwim units, with an overall average

501 distribution of detrital zircon ages of ~M54 P14 Pc32, that reflects derivation from the YCT.

502

503 Major Elements

504 Results

505 Results of the whole rock geochemical analyses are provided in Supplementary

506 Table S6 and re-calculated geochemical data is shown in Table 6. The major elements

507 Al2O3 and Na2O of sandstone show an increase in abundance with increasing SiO2 content

508 (Fig. 12), while MgO, CaO, and P2O5 show a decrease in abundance. Major elements

509 Fe2O3, TiO2, and K2O show no trend. The major elements of mudstone show no strong

510 trend with increasing SiO2 concentration (Fig. 12), and tend to plot as a group at the higher

511 SiO2 end of the sandstone trends. The SiO2 and Al2O3 concentration of sandstones and

512 mudstones are similar, ranging from ~40-60 % and ~12-17 %, respectively. Hemipelagites

513 have considerably less SiO2 (~13-28 %) and Al2O3 (~4-9 %), but higher CaO

514 concentrations (>30%) relative to either sandstones or mudstones. The hemipelagites also

515 have higher MnO values (averaging ~0.3 %) and P2O5 values (several >1%) compared to

516 sandstones and mudstones.

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517 The SiO2/Al2O3 ratio (Table 6) is the same for both sandstones and mudstones

518 (~3.6), whereas hemipelagites have a slightly lower ratio (~3.3). The Fe2O3/K2O ratio

519 increases from sandstones (~4.9) to mudstones (~5.2), and decreases for hemipelagites

520 (~3.0). The A-CN-K or feldspar ternary diagram (Fig. 13), with apexes corresponding to

521 Al2O3-(CaO*+Na2O)-K2O (Fedo et al., 1995; Nesbitt, 2003), shows that the majority of the

522 sandstones plot close to, or below, the composition of unweathered igneous rocks and

523 plagioclase. They also have a Chemical Index of Alteration (CIA) ranging from ~20-50

524 (Table 6), indicating they are unweathered or have undergone only incipient weathering.

525 Furthermore, their average Index of Compositional Variability (ICV, Table 6), calculated as

526 [Fe2O3+CaO+Na2O+K2O+MgO+MnO+TiO2)/Al2O3] (Cox et al., 1995), is >1,

527 corresponding to first-cycle input or compositional immaturity (Cox et al., 1995).

528 Mudstones generally plot between the composition of unweathered igneous rocks and

529 plagioclase, and the average shale composition (Fig. 13). Their CIA ranges from ~50-70,

530 indicating they are moderately weathered (Fedo et al., 1995; Nesbitt, 2003), and their

531 average ICV is also >1, corresponding to first-cycle input or compositional immaturity

532 (Cox et al., 1995). Both sandstone and mudstone compositions deviate slightly from the A-

533 CN join towards the K-apex. Hemipelagite compositions cluster near the CN-apex on the

534 ternary diagram (Fig. 13), with CIA ranging from ~5-15, and their average ICV is > 1.

535

536 Interpretations

537 The SiO2/Al2O3 ratio is an index of mineralogical maturity (Taylor and McLennan,

538 1985), and both sandstones and mudstones have similar values (~3.6). The Fe2O3/K2O ratio

539 is an index of mineralogical stability (Taylor and McLennan, 1985), and values increase

540 from sandstones (~4.9) to mudstones (~5.2). The major element A-CN-K ternary diagram

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541 (Fig. 13) and CIA of Fedo et al. (1995) monitors only feldspar weathering, but these two

542 parameters, together with the index of mineralogical maturity and the index of

543 mineralogical stability, show that mudstones are slightly more weathered than sandstones,

544 as might be expected. In addition, the siliciclastic compositions deviate slightly from the A-

545 CN join towards the K-apex, suggesting minor post-depositional K metasomatism.

546 Hemipelagites were initially classified as biogenic oozes (> 75 % biogenics) based

547 on their vigorous reaction to HCl acid in the field (Lowey, 2007), but according to their

548 CaO content (29-43%, and assuming all of it was biogenic in origin) they are more properly

549 classified as biogenic mud (25-50% biogenics; Pickering et al., 1989). The hemipelagites

550 are geochemically distinct from the sandstones and mudstones on the basis of their higher

551 CaO, MnO (0.3 %), and P2O5 (~ >1%) contents. The anonymously low CIA values for the

552 hemipelagites is attributed to their high CaO content, because in calculating the CIA value

553 CaO is assumed to be associated only with silicate minerals.

554

555 Trace Elements, Rare Earth Elements, and Isotopes

556 Results

557 Sandstones have an average total rare earth element (∑REE) concentration of ~88

558 ppm (Table 6), comprising an average light rare earth element (∑LREE) concentration of

559 ~76 ppm and an average heavy rare earth element (∑HREE) concentration of ~12 ppm,

560 with an average ∑LREE/∑HREE ratio of ~6. Mudstones have a slightly lower average

561 ∑REE concentration of ~83 ppm, consisting of an average ∑LREE concentration of ~70

562 ppm and an average ∑HREE concentration of ~12 ppm, with an average ∑LREE/∑HREE

563 ratio of ~5. Hemipelagites have a significantly higher average ∑REE concentration of ~141

564 ppm, comprising an average ∑LREE concentration of ~127 ppm, but an average ∑HREE

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565 concentration of only ~13 ppm, corresponding to an average ∑LREE/∑HREE ratio of ~9.

566 Chondrite-normalized rare earth element plots (Fig. 14A, B, C) of sandstone, mudstone,

567 and hemipelagite samples display similar, parallel, listric-shaped profiles with significant

568 LREE enrichment (x40-100) that is broadly decreasing, moderate middle rare earth-element

569 (MREE) enrichment (x10-20), and minor HREE enrichment (x10). The lack of significant

570 Ce and Eu anomalies relative to chondrite appears to be present in all profiles, with the

571 exception of hemipelagites, for which one sample displays a positive Eu anomaly. The

572 chontrite-normalized ratio of La/YbN indicates moderate fractionation of LREE in

573 sandstones (~5.81) and mudstones (~4.29), compared to greater fractionation of LREE in

574 hemipelagites (~14.34), whereas the chontrite-normalized ratio of Gd/YbN indicates minor

575 fractionation of HREE in sandstones (~1.46) and mudstones (~1.39), compared to slightly

576 greater fractionation of HREE in hemipelagites (~1.56).

577 On the Lu/Hf versus Sm/Nd diagram (Fig. 15), sandstones plot in the field for

578 turbidites and along the trend for magmatic differentiation (close to the composition of

579 granitoids, or GTS, with SiO2 >55%; Hawkesworth et al., 2010), whereas mudstones are

580 concentrated in the field for cratonic shales. Hemipelagites have considerable scatter: one

581 sample plots in the field for normal clays, but most of the samples have compositions

582 between the field for normal clays and the field for red clays (not shown in Figure 15, but

583 directly above the field for normal clay and above the Lu/Hf value of 0.25).

584 On the Th/Sc versus Zr/Sc diagram (Fig. 16), sandstones and mudstones plot within

585 the field for active margin turbidites and along the trend for compositional variations. This

586 diagram also indicates that element abundances in sandstones and mudstones are due to the

587 composition of the source area (which was andesitic in composition), rather than sediment

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588 recycling or sorting. Element abundances in hemipelagites also appear to be due to

589 compositional variations in the source area.

590 Tectonic discrimination diagrams of La versus Th (Fig. 17A) and Sc-Th-Zr/10 (Fig.

591 17B) reveal that sandstone and mudstone samples plot mainly in the ocean island arc field,

592 with some overlap in the continental arc field. Hemipelagites also plot in or near the ocean

593 island arc field (Fig. 17A).

594 The initial εNd (149) values for the time corresponding to deposition (~149 Ma) range

595 from +1.6 to +4.6 for sandstones, +0.1 to +3.3 for mudstones, and -2.0 to +2.5 for

596 hemipelagites (Table 7). Figure 18 shows histograms of sandstone, mudstone, and

597 hemipelagite samples for εNd (149) (Fig. 18A), Eu/Eu* (the Eu value expected for a smooth

598 chondrite-normalized REE profile) (Fig. 18B), Th/Sc (Fig. 18C), and Th/U (Fig. 18D),

599 based on values defined by McLennan at al. (1993). The εNd (149) values are inconclusive

600 with respect to the fields defied by McLennan et al. (1993), although these fields were

601 defined for modern sediments only. The Eu/Eu*, Th/Sc, and Th/U values all fall within the

602 fields for sediments derived from a young (i.e., juvenile or depleted mantle source),

603 undifferentiated arc.

604 The present day εNd (0) values for sandstones range from +0.4 to +3.4; mudstones

605 range from 0 to +4.2; and hemipelagites range from -3.2 to +1.4 (Table 7). A plot of εNd(0)

606 versus 147Sm/144Nd (Fig. 19) reveals that the sandstone, mudstone, and hemipelagite

607 samples have similar Sm-Nd characteristics as the Gravina belt and are within the Sm-Nd

608 isotopic field of the Alexander and Wrangellia terranes that form part of the WCT. The

609 depleted mantle model age for sandstones range from 0.69-0.94 Ga; mudstones range from

610 0.9 -1.0 Ga; and hemipelagites range from 0.75-1.27 Ga.

611

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612 Interpretations

613 The ∑REE for sandstones (~88 ppm) is within the range of Phanerozoic greywackes

614 (~45-207 ppm) and modern turbidite sands (~50-195 ppm) (Taylor and McLennan, 1985).

615 The ∑REE for mudstones (~84 ppm) is lower than North American Shale Composite

616 (NASC) (~173) and Post Archean Australian Shale (PAAS) (~187) (Taylor and McLennan,

617 1985). The relatively low ∑REE displayed by both sandstones and mudstones is

618 characteristic of sediments derived from young, undifferentiated arcs (McLennan et al.,

619 1993). The ∑LREE/∑HREE ratio for sandstones (~6) and mudstones (~5), is slightly less

620 than NASC (~7.1) and total crust (~7.2), but less than Global Subducting Sediment

621 (GLOSS) (~8.8), PAAS (~9.45), and upper crust (~9.47) (Taylor and McLennan, 1985).

622 However, the SiO2/Al2O3 ratio for sandstones (~3.55-3.68) and mudstones (~3.63) is

623 similar to andesite (~3.39), NASC (~3.8) and total crust (~3.8), but lower than GLOSS

624 ~4.9, or upper crust ~4.3 (Taylor and McLennan, 1985). Therefore, the lower observed

625 ∑LREE/∑HREE ratio for the sandstones and mudstones is probably not due to quartz

626 dilution, but rather mixing of a juvenile and more evolved source. Furthermore, the

627 siliciclastics lack significant Eu anomalies on chondrite normalized REE diagrams (Fig.

628 14A, B, C), making these profiles dissimilar to the profiles for GLOSS, NASC, PAAS,

629 upper crust, and middle crust (Fig. 14D), but they closely match the profile for total crust.

630 The lack of significant Eu anomalies (Eu/Eu*) in sandstones (~0.97-1.04) and mudstones

631 (~1.01), both of which are close to Eu anomalies for andesites (~0.95-1.07; Taylor and

632 McLennan, 1985), further substantiates a young, undifferentiated arc provenance and are

633 characteristic of first-cycle volcanogenic material derived from an adjacent magmatic arc

634 (Taylor and McLennan, 1985).

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635 The moderate (La/Yb)N values for the sandstones (~5.81) and mudstones (~4.29),

636 together with the low (Gd/Yb)N values for these rocks (~1.46 and ~1.39, respectively), also

637 indicates only moderate igneous differentiation of the source rocks, corroborating the Lu/Hf

638 and Sm/Nd results (Fig. 15) and the Th/Sc vs Zr/Sc results (Fig. 16).

639 The Lu/Hf ratio is an index of igneous differentiation comparing compatible HREE

640 Lu and incompatible high field strength element Hf, whereas the Sm/Nd ratio is also an

641 index of igneous differentiation comparing incompatible LREE Sm (which tends to

642 concentrate in the mantle) and moderately compatible LREE Nd (which tends to

643 concentrate in continental crust); both ratios decrease with increasing differentiation

644 (Taylor and McLennan, 1985; McLennan et al., 1993). The Lu/Hf vs Sm/Nd plot (Fig. 15)

645 for the siliciclastics suggests that source rocks were granitoid in composition (i.e., SiO2

646 >55%; Hawkesworth et al., 2010), compatible with an andesitic composition determined

647 from the Th/Sc vs Zr/Sc diagram (Fig. 16). Furthermore, the siliciclastics display lower

648 Lu/Hf and Sm/Nd ratios than island arcs, indicating the sediments appear to be more

649 chemically evolved than volcanic arc rocks, but higher Lu/Hf and Sm/Nd ratios than Upper

650 Continental Crust (UCC), suggesting the sediments appear to be less chemically evolved

651 than continental crust rocks

652 The Th/Sc ratio is an index of igneous differentiation that compares incompatible

653 Th to moderately compatible Sc, whereas the Zr/Sc ratio is an index of zircon enrichment

654 that compares moderately incompatible Zr to moderately compatible Sc (Taylor and

655 McLennan, 1985; McLennan et al., 1993). The Th/Sc vs Zr/Sc plot (Fig. 16) documents

656 moderate igneous differentiation corresponding to a source area that was andesitic in

657 composition, and the low zircon enrichment (low sediment recycling) is compatible with

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658 the CIA results. Low Th/Sc ratios also suggest that the source was a young (juvenile or

659 mantle derived), undifferentiated arc (McLennan, 1989; McLennan et al., 1993).

660 Sandstone and mudstone compositions plotted on the La vs Th and La-Sc-Th

661 tectonic discriminant diagrams of Bhatia and Crook (1986) suggest an ocean island arc

662 provenance with some input from a continental arc (Fig. 17). Bhatia and Crook (1986)

663 define a continental arc as an island arc formed on well developed continental crust or a

664 thin continental margin.

665 The Sm-Nd isotopic systematics for sandstones (εNd(149 Ma)=+1.6 to +4.6) and

666 mudstones (εNd(149 Ma) =+0.1 to +3.3) indicate primarily a depleted mantle source with

667 some mixing of an older crustal source (Fig.18). Mixing of an older crustal source is

668 supported by the TDM age for sandstones (0.7-0.9 Ga) and mudstones (0.9-1.0), which

669 depart significantly from their stratigraphic age (~149 Ma), implying magmatic or

670 sedimentary re-cycling of older material. The εNd vs Age plot (Fig. 19) shows that

671 siliciclastics plot within the fields for the Alexander, Wrangellia, and Stikine terranes, and

672 the Gravina belt.

673 The hemipelagites not only have higher CaO, MnO, and P2O5 contents compared to

674 that of sandstones and mudstones, but they also have higher ∑REE (~141 ppm)

675 concentrations and ∑LREE/∑HREE ratios (~9, which is similar to values for GLOSS,

676 PAAS, and UCC). The hemipelagites also display significant negative Ce anomalies

677 (~0.83) and positive Eu anomalies (~1.33), and somewhat more evolved initial εNd values (-

678 2.0 to +2.5) and older depleted mantle model ages (0.75-1.27 Ga) than the sandstones and

679 mudstones.

680 Generally, hemipelagites are thought to have a mixed origin (components of

681 lithogenous, biogenous, hydrogenous, and cosmogenous origin; Seibold and Berger, 1982),

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682 which could result in a complicated geochemical fingerprint of their provenance. The

683 ∑LREE enrichment, evolved initial εNd values, and older TDM ages of the hemipelagites

684 suggest mixing with continental derived material, possibly via eolian dust (e.g., Rea, 1994).

685 Alternatively, the greater MnO and P2O5 compositions, together with the negative Ce and

686 positive Eu anomalies displayed by the hemipelagites, may indicate preferential

687 concentration of LREE in post-depositional authigenic apatite or monazite (cf., Milodowski

688 and Zalasiewicz, 1991; Ball et al., 1992; Ehrenberg and Nadeau, 2002; Evans et al., 2009;

689 Guo, 2010). Deciphering the complex geochemical signal in the hemipelagites is the focus

690 of ongoing research.

691

692 Discussion

693 Directional Provenance Indicators

694 Previous researchers (e.g., Nokleberg et al., 1985; McClelland et al., 1992; Kapp

695 and Gehrels, 1998; Nokleberg and Richter, 2007; Yokelson et al., 2015) appear to have

696 overlooked the utility of existing paleocurrent data for the Gravina-Nutzotin belt, thereby

697 obfuscating the provenance record. However, paleocurrent data for the Dezadeash

698 Formation are robust (i.e., ~600 measurements of sole marks, cross laminations, slump

699 folds, and a debris flow channel distributed vertically and laterally throughout the strata)

700 and documents a sediment source from the west (i.e., the WCT) with a paleoslope dipping

701 eastward in the direction of Laurasia. Paleocurrent data from the Nutzotin Mountains

702 sequence are less robust (i.e., ~400 measurements of mainly cross laminations and clast

703 imbrications), but also suggests a sediment source to the west. There are no directional

704 provenance indicators linking the Dezadeash Formation and Nutzotin Mountains sequence

705 with inboard terranes (i.e., Yukon-Tanana, Slide Mountain, Cache Creek, Quesnel, and

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706 Stikine). Therefore, the paleocurrent data for the Dezadeash Formation and Nutzotin

707 Mountains sequence constrain the provenance to the west. Paleocurrent data for the

708 Gravina belt are not robust (i.e., ~30 measurements of mainly cross laminations), but

709 Cohen et al. (1985) inferred a sediment source to the west based on a dominance of 160-90

710 Ma 40Ar /39Ar ages from biotite and amphibole grains in Gravina belt strata that were

711 interpreted to have been derived from the Chitina arc. If the Gravina belt formed in the

712 same overall tectonic setting as the Dezadeash Formation and Nutzotin Mountains

713 sequence, then an overall sediment source to the west for the Gravina-Nutzotin belt is

714 likely, as originally proposed by Monger et al. (1983).

715 Although the eastern margin of the Dezadeash Formation is not preserved or has not

716 been recognized, it is conceivable that sediment could have been shed from the east (i.e.,

717 YCT). However, any potentially east-derived sediment would represent an entirely

718 different sediment dispersal system than the Dezadeash Formation, interpreted as an

719 eastward prograding point-source submarine fan (Eisbacher, 1976; Lowey, 2007). That is,

720 separate 'western facies' (Dezadeash Formation) and 'eastern facies' (not preserved or not

721 recognized yet) are possible, similar to that proposed for the Gravina belt (Yokelson et al.,

722 2015).

723

724 Compositional Provenance Indicators

725 Consideration of the directional provenance indicators is a requisite for the

726 interpretation of the compositional provenance indicators. Namely, paleocurrent data for

727 the Dezadeash Formation suggests that sediment was derived exclusively from the west

728 (i.e., the WCT and Chitina arc). Inboard terranes (e.g., Yukon-Tanana, Slide Mountain,

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729 Cache Creek, Quesnel, and Stikine) did not contribute sediment, with the exception of

730 perhaps minor additions to hemipelagite beds.

731 Conglomerate clasts in the Dezadeash Formation were likely derived locally from

732 the WCT and Chitina arc: volcanic and igneous mafic clasts match the composition of the

733 Permian Skolai Group and Triassic Nikolai Formation; sedimentary clasts resemble the

734 compositions of an unnamed upper Paleozoic-upper Triassic map unit (uPpc), the Permian

735 Skolai Group, Triassic McCarthy Formation, and the Chitistone and Nizina Limestone

736 units; and plutonic clasts match the composition of the Jura-Cretaceous Saint Elias Plutonic

737 Suite (Dodds and Campbell, 1992). Even though Berg et al. (1972) suggested that clasts of

738 white quartz and metamorphic rocks were derived from the Yukon-Tanana terrane, these

739 lithologies are also present in the WCT. Detritus sourced from the WCT is supported by the

740 Triassic (Late Norian) conodont age obtained from the limestone clast in the Dezadeash

741 Formation. This age is identical to that of an unnamed upper Paleozoic-upper Triassic map

742 unit (uPpc) and the Triassic McCarthy Formation, both of which contain similar conodont

743 species (Dodds et al, 1993). The K-Ar age (~144 Ma) from the diorite pebble in the

744 Dezadeash Formation is compatible with K-Ar ages for the Saint Elias Plutonic Suite

745 (Dodds and Campbell, 1992), interpreted as the roots of the Chitina arc (Lowey, 2011).

746 Conglomerate clast and sandstone frameworks modes from the Dezadeash

747 Formation are compatible with derivation from the Chitina arc according to various tectonic

748 discrimination diagrams (Figs. 7, 8). As discussed by Boggs (2009), the larger particle size

749 of conglomerate may make them more reliable provenance indicators than sandstone, with

750 the caveat that conglomerate clasts have not been removed during weathering or

751 transportation. The preservation of carbonate clasts in conglomerate and carbonate grains in

752 sandstone from the Dezadeash Formation, together with the results of the A-CN-K feldspar

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753 weathering diagram (Fig. 13) for sandstone from the Dezadeash Formation, suggests that

754 the conglomerate, like the sandstone, is only moderately weathered.

755 Detritus sourced from the Chitina arc is supported by the detrital zircon age mode

756 between ~165-150 Ma from the Dezadeash Formation (Fig. 10), which matches the 160-

757 140 Ma age of the Chitina arc (Plafker et al., 1989; Nokleberg et al., 1994; Roeske et al.,

758 2003), and is close to the age of the Chitina arc as determined from the age of magmatic

759 zircons recovered from a tuff bed in the Dezadeash Formation (~149 Ma; Lowey, 2011).

760 The somewhat older detrital zircon ages (207-164 Ma) obtained from the sandstones in the

761 Dezadeash Formation may indicate proximity to the Talkeetna arc, which was apparently

762 active ~205-155 Ma (Amato et al., 2007; and zircon data compiled by Hampton et al.,

763 2010). The Dezadeash Formation contains only several Paleozoic grains and several

764 Precambrian grains, although zircons of these ages are present in greater abundance in the

765 WCT ( Gehrels et al., 1996; Grove et al., 2008; Beranek et al., 2012; Beranek et al., 2013).

766 The lack of abundant detrital zircons of Paleozoic age is not uncommon in samples from

767 the Gravina-Nutzotin belt: samples from the Nutzotin Mountains sequence contain no

768 Paleozoic zircons (Manuszak et al., 2007), or only a few grains (Hults et al., 2013), and

769 'Pybus Bay' samples from the Gravina belt contain no Paleozoic zircons (Kapp and Gehrels,

770 1998; Yokelson et al., 2015). Generally, samples from the Gravina belt contain a significant

771 population of Paleozoic zircons (Kapp and Gehrels, 1998; Yokelson et al., 2015). The

772 difference in the population of Paleozoic zircons in the Gravina belt compared to the

773 Dezadeash Formation and Nutzotin Mountains sequence may simply reflect differences in

774 the number of samples (twelve from the Gravina belt versus two from the Dezadeash

775 Formation and two from the Nutzotin Mountains sequence). Another explanation is that

776 Paleozoic zircons are more readily available from the Alexander terrane, which underlies

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777 the Gravina belt, compared to the Wrangellia terrane, which underlies the Dezadeash

778 Formation and Nutzotin Mountains sequence (Hults et al., 2013).

779 The geochemistry of sandstone and mudstone beds from the Dezadeash

780 Formation is characteristic of sediments sourced from young, undifferentiated arcs,

781 compatible with derivation from the Chitina arc, as revealed by various tectonic

782 discrimination diagrams (Figs. 15, 16, 17, 18). Sm-Nd systematics of sandstone and

783 mudstone beds from the Dezadeash Formation are compatible with the strata being sourced

784 from the WCT and the Chitina arc (Fig. 19).

785

786 Tectonic Setting

787 Due to uncertainties regarding the timing and location of collision of the WCT with

788 Laurasia, and the number and polarity of Mesozoic magmatic arcs, the tectonic setting of

789 the WCT with respect to Laurasia remains unresolved. As a result, various tectonic settings

790 have been proposed and these are summarized by and Kapp and Gehrels (1997) and

791 Sigloch and Mihalynuk (2017). Tectonic settings relevant to the origin of the Gravina-

792 Nutzotin belt can be subdivided into east-dipping subduction and west-dipping subduction

793 models (Fig. 20). East-dipping subduction models include: 1) a precollisional, ocean basin

794 scenario (Fig. 20A) with east-dipping subduction beneath the WCT, east-dipping

795 subduction beneath the accreted YCT margin, and an ocean of indeterminant width

796 separating the WCT from the YCT (Monger et al., 1982); 2) a syncollisional, retroarc

797 foreland basin scenario (Fig. 20B) with east-dipping subduction beneath the WCT and east-

798 dipping subduction beneath the YCT, in which the WCT is colliding progressively from

799 the south to the north with the accreted YCT (Trop et al., 2002); and 3) a rift or

800 transtensional basin scenario (Fig. 20C) with east-dipping subduction beneath the WCT and

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801 a narrow ocean separating the WCT from the accreted YCT (Yokelson et al., 2015). The

802 only west-dipping subduction model is a precollisional, forearc basin scenario (Fig. 20D),

803 with west-dipping subduction beneath the WCT and a wide ocean separating the WCT

804 from the accreted YCT (Sigloch and Mihalynuk, 2017).

805 The backarc, rift/transtensional, and retroarc foreland basin scenarios are based on

806 the premise that a provenance link exists between the Gravina-Nutzotin belt and the

807 western margin of Laurasia: namely, that clasts of white vein quartz and metamorphic rocks

808 in the Nutzotin Mountains sequence (Berg et al. 1972; Richter, 1976; Nokleberg et al.,

809 1985; Manuzsak et al., 2007), and 380-330 and >900 Ma detrital zircons in the Gravina belt

810 (Kapp and Gehrels, 1998) were derived from the YCT. However, clasts representing these

811 compositions and zircons representing these ages can be accounted for in the WCT.

812 Support for the rift/transtensional and retroarc foreland basin models is further weakened

813 by the detrital zircon signature of the Gravina-Nutzotin belt. According to Cawood et al.

814 (2012), the tectonic setting of a basin can be inferred from the detrital zircon age spectra

815 deposited in the strata. The Dezadeash Formation, Nutzotin Mountains sequence, and

816 Gravina belt display detrital zircon age spectra that are unlike those for collisional settings

817 (foreland basins) and extensional settings (rift/transtensional basins), characterized by a

818 greater proportion of older zircon ages compared to the depositional age of the strata), but

819 match those for convergent settings (including trench, forearc and backarc basins), which

820 are dominated by zircon ages close to the depositional age of the sediment (Cawood et al.,

821 2012).

822 The preferred tectonic setting, based in part on the reinterpretation by Sigloch and

823 Mihalynuk (2013, 2017) of the tectonic setting of the western margin of Laurasia (i.e., the

824 North American Cordillera), is the forearc basin scenario (Fig. 20D). Using tomographic

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825 images of lower-mantle slabs, Sigloch and Mihalynuk (2013, 2017) suggested that

826 westward subduction of the Mezcalera slab beneath the WCT consumed the large

827 intervening 'Mezcalera ocean basin' separating the WCT from Laurasia. The basin fill

828 (mainly deep marine turbidites), preserved basin dimensions (tens of kilometres wide and

829 hundreds of kilometres long, with sediment thickness of ~3,000 m), and basin architecture

830 (flanked by a volocanoplutonic arc) of Dezadeash Formation is consistent with modern and

831 ancient forearc basins documented by Dickinson (1995). In addition, the depositional

832 architecture of the Dezadeash Formation and Nutzotin Mountains sequence supports a

833 forearc basin scenario: the Dezadeash Formation, interpreted as the distal facies of the

834 basin, comprises lower to middle submarine fan deposits that display no apparent, overall

835 vertical trend (Lowey, 2007), whereas the Nutzotin Mountains sequence, interpreted as the

836 proximal facies of the basin, comprises upper submarine fan to shelf deposits that display a

837 general upward-shallowing and upward-coarsening sequence (Manuzsak et al., 2007).

838 According to Dickinson (1995), one of the characteristics of a forearc basin is a

839 depositional architecture that shoals upward from turbidite facies to shelf facies.

840 The directional and compositional provenance indicators for the Dezadeash

841 Formation cannot indicate with certainty the tectonic setting of the Gravina-Nutzotin belt

842 because the eastern margin of the Dezadeash Formation is no longer preserved (or has not

843 been recognized). Reconciling which scenario is correct may be difficult, or impossible,

844 given the variable preservation potential of different tectonic segments along a converging

845 and colliding arc (Draut and Clift, 2013).

846

847 Conclusions

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848 Compositional provenance data from submarine fan deposits of the Dezadeash

849 Formation, including conglomerate pebble-counts, a hornblend K-Ar age from a diorite

850 pebble, a conodont age from a limestone cobble, sandstone point-counts, U-Pb age of

851 detrital zircons from sandstones, and the lithogeochemistry of sandstones, mudstones and

852 hemipelagites, including major elements, trace elements, rare earth elements, and Sm-Nd

853 isotopes, interpreted in the context of directional provenance indicators that document

854 sediment was derived from the west, lead to the following conclusions:

855

856 1 The framework composition of conglomerates is dominated by andesite clasts,

857 with lesser amounts of sedimentary, plutonic, and quartz clasts. A hornblende K-Ar age

858 from a diorite clast and a conodont age from a limestone clast is compatible with the WCT

859 as the sediment source. The P-S-V ternary diagram suggests that conglomerates were

860 derived mainly from an undissected arc compatible with the Chitina arc built on the WCT.

861

862 2 The framework composition of sandstones is dominated by lithic grains (mainly

863 volcanic grains exhibiting felsitic and lathwork textures). Sandstone ternary diagrams of

864 Qt-F-L and Qm-Fl-T suggest derivation from a transitional to undissected arc; high P/F

865 ratios (~>0.8) and Lv/L ratios (~>0.9) also suggest an undissected arc provenance.

866

867 3 The U-Pb age range of 165-155 Ma from detrital zircons in the sandstones is

868 compatible with their derivation from the contemporaneous Chitina volcanic arc.

869

870 4 The lithogeochemistry of sandstones and mudstones is similar with regards to

871 major elements (e.g., SiO2/Al2O3 ~3.6), rare earth elements (e.g., ∑REE ~83-88 ppm,

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872 ∑LREE/∑HREE ~5-6, and lack of Ce and Eu anomalies), various plots of Lu/Hf vs Sm/Nd,

873 Th/Sc vs Zr/Sc, La vs Th, La-Sc-Th, and Sc-Th-Zr plots, and Sm-Nd isotopic systematics

874 (e.g., overrlapping initial εNd values, with sandstones ranging from +1.6 to +4.6, and

875 mudstones from +0.1 to +3.3). The similarities in their geochemistry implies they were

876 derived from the same young (dominantly mantle derived), undifferentiated volcanic arc,

877 with mudstones being more weathered than sandstones (e.g., CIA values range from ~50-

878 70, compared to ~20-50 for sandstones).

879

880 5 The lithogeochemistry of the hemipelagites is distinct from the sandstones and

881 mudstones, particularly with regards to several major elements (e.g., higher CaO, MnO, and

882 P2O5 contents), rare earth elements (e.g., ∑REE ~141 ppm, ∑LREE/∑HREE ~9, and

883 negative Ce anomalies and positive Eu anomalies), and Sm-Nd isotopic systematics (e.g.,

884 initial εNd values range from -2.0 to +2.5). Their geochemistry implies a mixed (i.e., more

885 evolved) provenance and/or diagenetic alteration.

886

887 Integrated provenance analysis of the Dezadeash Formation suggests that

888 conglomerate, sandstone, and mudstone were shed eastward from the undissected Chitina

889 magmatic arc and the WCT into an adjacent flysch basin. The Chitina arc consisted mainly

890 of undifferentiated andesitic volcanic rocks built on the WCT. The andesitic rocks were

891 sourced from the depleted mantle with some mixing of crustal contaminant (i.e., the WCT

892 terrane proxing for continental crust). Hemipelagites may have a mixed (partly continental-

893 derived) provenance and/or have undergone diagenetic modification of their

894 lithogeochemistry. Given that the eastern margin of the Dezadeash Formation is not

895 preserved, the provenance dataset presented herein does not unequivocally constrain the

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896 tectonic setting of the Gravina-Nutzotin belt, but strongly suggests a convergent plate

897 margin setting.

898

899 Acknowledgements

900 Thanks to Werner Liebau for his outstanding assistance in the field, pilot Doug Makkonen

901 for his expert helicopter flying, and Jochen Mezger for his thoughtful discussions. George

902 Gehrels graciously analyzed the zircons. I am grateful to CJES Editor Ali Polat and an

903 anonymous reviewer for making a thorough examination of this manuscript and particularly

904 Todd Lamaskin for providing thoughtful, constructive comments.

905

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1325 Gravina belt, southeast Alaska. Tectonics, 34: 1-14.

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1328

1329 Figure Captions

1330

1331 Figure. 1. Location map and geologic setting of the Dezadeash Formation, Yukon

1332 (compiled from Makevet, 1978; Wheeler and McFeely, 1991; and Monger, 2014).

1333 AT=Alexander terrane, CC=Cache Creek terrane, PT=Peninsular terrane, ST=Stikine

1334 terrane, YTT=Yukon-Tanana terrane, WT=Wrangellia terrane. Kootenay , Cassiar, and

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1335 Quesnel terranes not shown. Other Jura-Cretaceous basins not part of the Gravina-Nutzotin

1336 belt: KBa=Kahiltna basin-Alaska Range, KBt=Kahiltna basin-Talkeetna Mountains,

1337 MB=Matanuska Valley basin, WB=Wrangell Mountains basin. T=Talkeetna arc,

1338 C=Chitina arc, A=Chisana arc.

1339

1340 Figure. 2. Generalized stratigraphic sections showing lithologic comparison of strata from

1341 different parts of the Gravina-Nutzotin belt (after Berg et al., 1972; McClelland et al., 1992;

1342 Cohen and Lundberg, 1993; Plafker and Berg, 1994; and Trop et al., 2002).

1343

1344 Figure. 3. Location of measured sections (numbers) in the Dezadeash Formation, Yukon,

1345 from which samples were collected (modified from Lowey, 2007).

1346

1347 Figure. 4. Photographs of representative lithofacies that were sampled from the Dezadeash

1348 Formation, Yukon. A) Disorganized gravelly mudstone, long white interval on Jacob's Staff

1349 is 0.5 m long. B) Thick-bedded sandstone, 1.5 m long Jacob's Staff for scale. C) Medium-

1350 to thin-bedded sandstone, 1.5 m long Jacob's Staff for scale. D) Mudstone, green squares at

1351 top of scale card are 1 cm long. E) Hemipelagite bed (brown bed). Brown interval on

1352 Jacob's Staff is 0.1 m long.

1353

1354 Figure. 5. Directional provenance indicators from the Gravina-Nutzotin belt: the Nutzotin

1355 Mountains sequence compiled from Kozinski (1985) and Manuzsak et al. (2007); the

1356 Dezadeash Formation compiled after Eisbacher (1976) and Lowey (1980, 1998); and the

1357 Gravina Belt compiled after Cohen (1992).

1358

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1359 Figure. 6. Pebble-count compositions of conglomerates from the Dezadeash Formation,

1360 Yukon. A) P+M-S-V ternary diagram. Classification after Cox and Low (1995). B) P-S-V

1361 ternary diagram. Classification after Dickie and Hein (1995). Data sources as follows:

1362 Gravina belt, Cohen (1992); Nutzotin Mountains sequence, Manuszak et al. (2007).

1363 P=plutonic clasts; M=metamorphic clasts; S=sedimentary clasts; and V=volcanic clasts.

1364

1365 Figure. 7. Point-count compositions of sandstones from the Dezadeash Formation, Yukon.

1366 A) Qt-F-L ternary diagram. Classification after Dickinson et al. (1983). B) Qm-P-K ternary

1367 diagram. Classification after Dickinson and Suczek (1979). Data sources as follows:

1368 Gravina belt, Cohen and Lundberg (1993); Nutzotin Mountains sequence, Kozinski (1985)

1369 and Manuszak et al. (2007). Qt=total quartz grains, including monocrystalline and

1370 polycrystalline grains, and chert; F=total feldspar grains; L=total lithic grains; Qm-

1371 monocrystalline quartz grains; P=plagioclase grains; and K=potassium feldspar grains.

1372

1373 Figure. 8. Point-count compositions of sandstones from the Dezadeash Formation, Yukon.

1374 A) Qp-Ls-Lv ternary diagram. Classification after Dickinson and Suczek (1979). B) Lm-

1375 Ls-Lv ternary diagram. Classification after Marsaglia and Ingersoll (1992). Data sources as

1376 follows: Gravina belt, Cohen and Lundberg (1993); Nutzotin Mountains sequence,

1377 Kozinski (1985) and Manuszak et al. (2007). Qp=polycrystalline quartz grains;

1378 Ls=sedimentary lithic grains; Lv=volcanic lithic grains; Lm=metamorphic lithic grains.

1379

1380 Figure. 9. Pb/U concordia diagrams of analyses of single detrital zircon grains from the

1381 Dezadeash Formation, Yukon. A) Sample GL-74A. B) Sample GL-74B. Error ellipses are

1382 shown at 1σ (plotted with the programs of Ludwig, 2008).

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1383

1384 Figure. 10. Pb/U histograms and age spectra of single detrital zircon grains from the

1385 Dezadeash Formation, Yukon. A) Sample GL-74A. B) Sample GL-74B. Error ellipses are

1386 shown at 1σ (plotted with the programs of Ludwig, 2008).

1387

1388 Figure. 11. Comparison of Pb/U age spectra detrital zircon grains for Yukon-Tanana

1389 terrane (YTT), Wrangellia composite terrane (WCT), and Gravina-Nutzotin belt. Data

1390 source as follows: Kapp and Gehrels (1998), and Nelson and Gehrels (2007).

1391

1392 Figure. 12. Harker diagrams of sandstone (yellow squares), mudstone (green circles) and

1393 hemipelagite (blue triangles) samples from the Dezadeash Formation, Yukon, showing

1394 general compositional trends (sandstone=solid red line, mudstone=dashed red line) and

1395 Spearman rank correlation coefficients (r).

1396

1397 Figure. 13. Feldspar weathering diagram [A-CN-K ternary plot of molecular proportions of

1398 Al2O3-(CaO*+Na2O)-K2O] and Chemical Index of Alteration (CIA) of sandstone,

1399 mudstone and hemipelagite samples from the Dezadeash Formation, Yukon. CaO*=CaO

1400 associated only with silicates. Yellow field (top) indicates main range in CIA of sandstone

1401 samples; green field (middle) indicates main range in CIA of mudstone samples; and blue

1402 field (botton) indicates main range in CIA of hemipelagite samples. After Nesbitt and

1403 Young (1984), Fedo et al. (1995), Nesbitt (2003), and McLennan et al. (2003).

1404

1405 Figure. 14. Chondrite-normalized rare earth element diagrams of sandstones (A),

1406 mudstones (B) and hemipelagites (C) from the Dezadeash Formation, Yukon. D) Average

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1407 REE values for Upper Crust, Middle Crust, Total Crust, North American Shale Composite

1408 (NASC), Post Archean Australian Shale (PAAS), and Global Subducting Sediment

1409 (GLOSS) (from Gromet et al., 1984; Plank and Langmuir, 1998; McLennan, 2001; and

1410 Rudik and Gao, 2003). Normalizing values after Sun and McDonough (1989).

1411

1412 Figure. 15. Chemical classification diagram (Lu/Hf versus Sm/Nd) for sandstone

1413 (SANDSTN), mudstone (MUDSTN) and hemipelagite (HEMIPLG) samples from the

1414 Dezadeash Formation, Yukon. Classification after Hawkesworth et al. (2010). Most

1415 sandstone and mudstone samples plot within the field for turbidites and along the trend for

1416 magmatic differentiation.

1417

1418 Figure. 16. Chemical classification diagram (Th/Sc versus Zr/Sc) for sandstone

1419 (SANDSTN), mudstone (MUDSTN) and hemipelagite (HEMIPLG) samples from the

1420 Dezadeash Formation, Yukon. Classification after McLennan et al. (1993). Most sandstone

1421 and mudstone samples plot within the field for active margin turbidites and along the trend

1422 for compositional variations in the source area.

1423

1424 Figure. 17. Tectonic setting discrimination diagrams for samples from the Dezadeash

1425 Formation, Yukon. A) La versus Th diagram for sandstone (SANDSTN), mudstone

1426 (MUDSTN) and hemipelagite (HEMIPLG) samples. Classification after Bhatia and Crook

1427 (1986). B) Sc-Th-Zr/10 ternary diagram for sandstone (SANDSTN), mudstone (MUDSTN)

1428 and hemipelagite (HEMIPLG) samples. Classification after Bhatia and Crook (1986).

1429

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1430 Figure. 18. Tectonic setting discrimination histograms for sandstone (SANDSTN),

1431 mudstone (MUDSTN) and hemipelagite (HEMIPLG) samples from the Dezadeash

1432 Formation, Yukon. A) εNd (149) values. B) Eu/Eu* values. C) Th/Sc values. D) Th/U values.

1433 OUCC=Old Upper Continental Crust, RSR=Re-cycled Sedimentary Rocks, YDA=Young

1434 Differentiated Arc, YUA=Young Undifferentiated Arc. Classification after McLennan et al.

1435 (1993).

1436

1437 Figure. 19. εNd (o) vs. Age diagram for sandstone (SANDSTN), mudstone (MUDSTN) and

1438 hemipelagite (HEMIPLG) samples from the Dezadeash Formation, Yukon, compared to the

1439 Wrangellia composite terrane (specifically the Alexander and Wrangellia terranes), Yukon

1440 composite terrane (specifically the Yukon-Tanana, Kootenay, Cassiar, Quesnel, Cache

1441 Creek, Slide Mountain, and Stikine terranes), and Kluane Schist. DM=depleted mantle

1442 standard, CHUR=chondrite meteorite standard. After Samson et al. (1989, 1990, 1991),

1443 Farmer et al. (1993), Patchett and Gehrels (1998), Aleinikoff et al. (2000), Mezger et al.

1444 (2001), and Green et al. (2009).

1445

1446 Figure. 20. Possible tectonic settings for the Wrangellia composite terrane and the

1447 continental margin of Laurasia, and origin of the basin containing strata of the Gravina-

1448 Nutzotin belt (no horizontal or vertical scale implied). A) Precollisional, ocean basin

1449 scenario with east-dipping subduction beneath the WCT, east-dipping subduction beneath

1450 the accreted YCT margin, and an ocean of indeterminant width separating the WCT from

1451 the YCT (modified from Berg et al., 1972; Monger et al., 1982; Nokleberg et al., 1985; and

1452 Kapp and Gehrels, 1998); B) Syncollisional, retroarc foreland basin scenario with east-

1453 dipping subduction beneath the WCT and east-dipping subduction beneath the YCT, in

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1454 which the WCT is colliding progressively from the south to the north with the accreted

1455 YCT (modified from Trop et al., 2002; and Manuszak et al., 2007); C) Rift or

1456 transtensional basin scenario with east-dipping subduction beneath the WCT and a narrow

1457 ocean separating the WCT from the accreted YCT (modified from van der Heyden, 1992;

1458 McClelland et al., 1992; McClelland and Mattinson, 2000; and Yokelson et al., 2015); and

1459 D) Precollisional, forearc basin scenario, with west-dipping subduction beneath the WCT

1460 and a wide ocean separating the WCT from the accreted YCT (modified from Hildebrand,

1461 2013; and Sigloch and Mialynuk, 2017). Penecontemporaneous east-dipping subduction

1462 (dashed lines) may have occurred (Sigloch and Mialynuk, 2017).

1463

1464 Supplementary Figure Captions

1465

1466 Supplementary Figure. 1. Point-count classification of sandstones from the Dezadeash

1467 Formation, Yukon. Q-F-R ternary diagram. Classification after Folk et al. (1970). Q=total

1468 monocrystalline and polycrystalline quartz grains excluding chert, F=total feldspar grains,

1469 R=total plutonic, metamorphic, and sedimentary rock grains, including chert.

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Table 1. Lithofacies sampled in the Dezadeash Formation, Yukon, Canada (lithofacies classification after Pickering et al., 1989).

____________________________________________________________________________________________________________________________

Description Other Characteristics Interpretation Lithofacies Code ____________________________________________________________________________________________________________________________

Disorganized conglomerate clasts up to 3 cm long debris flow A1.1

Disorganized muddy conglomerate clasts up to 20 cm long debris flow A1.2

Disorganized gravelly mudstone limestone clasts up to 10.5 m long debris flow A1.2

Disorganized gravelly mudstone limestone clasts up to 10.5 m long debris flow A1.4

Normally graded conglomerate clasts up to 30 cm long, rare coquina beds hyperconcentrated density flow A2.3

Thick/medium-bedded, fine- to medium-grained sand, rare granules, hyperconcentrated density flow B1.1

disorganized sandstone rip-up clasts, small channels or scours

Very thick/thick-bedded fine-grained sand, locally tuffaceous concentrated density flow C2.1

sandstone-mudstone couplets

Thin-bedded sandstone-mudstone couplets very fine to fine-grained sand surge-like turbidity flow C2.3

Thick irregular siltstone and mudstone laminae - - - turbidity flow-surge D2.2

Structureless mudstone - - - turbidity flow-surge E1.1

Lime mudstone black, associated with lithofacies C and D settling of biogenic ooze G1.1

____________________________________________________________________________________________________________________________

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Table 2. Re-calculated pebble-count data,

Dezadeash Formation, Yukon, Canada

(PMQ=plutonic+metamorphic+quartz clats,

S=sedimentary clasts, V=volcanic clasts).

_________________________________________

Sample PMQ % S % V %

_________________________________________

GL-244 28 60 12

GL-250 5 11 84

GL-257 31.6 46.4 22

_________________________________________

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Table 3. K-Ar isotopic age of diorite pebble (sample GL-244), Dezadeash Formation,

Yukon, Canada.

______________________________________________________________________________

Material K, 40*

Ar, 40*

Ar/Total 40

Ar 40*

Ar/40

K K-Ar age

analysed % ppm Ma ± 2σ

______________________________________________________________________________

hornblende 0.513 0.005319 0.254 0.008691 144 ±4

concentrate,

-80/+200

mesh

______________________________________________________________________________

Constants used are λᵦ=4.962x10 -10

/year, (λ ₑ + λ' ₑ)=0.581x10 -10

/year, 40

K/K=1.193x10-4

g /g, and

σ equals one standard deviation. Analysis by Geochron Laboratories, Cambridge, Massachusetts.

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Table 4. Sandstone point-count catagories, Dezadeash Formation, Yukon, Canada.

_______________________________________________________________________

Quartz Qt=Qm+Qp

Qc=Qm+Qp+Lsc

Qm=monocrystalline

Qp=polycrystalline (not including chert)

Feldspar F=Fk+Fp

Fk=kspar (potassium)

Fp=plagioclase

Lithic L=Ls+Lm+Lv

sedimentary Ls=Lsc+Lsm+Lsl

Lsc=chert

Lsm=mudstone

Lsl=limestone, dolostone and fossils

metamorphic Lm=Lmp+Lms

Lmp=phyllite

Lms=schist

volcanic Lv=Lvv+Lvf+Lvm+Lvl

Lvv=vitric texture

Lvf=felsitic texture

Lvm=microlitic texture

Lvl=lathwork texture

_______________________________________________________________________

Other (not included in total): bio=biotite, cpx=clinopyroxene, hor=hornblende,

opx=orthopyroxene, sph=spene, zir=zircon and (1, 2, 3, etc.)=number of grains counted.

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Table 5. Calculated point-count data (percent), Dezadeash Formation, Yukon, canada.

Sample Lithofacies Qm Qp Fk Fp Lsc Lsm Lsl Lmp Lms Lvv Lvf Lvm Lvt TOTAL

GL-19-1 C2.1 15.27 2.99 7.49 33.23 0.30 0.00 0.00 0.30 0.00 0.00 24.85 0.90 14.67 100.00 334

GL-22-2 C2.1 13.72 4.42 3.95 34.19 1.16 0.23 1.86 0.00 0.23 0.00 36.51 0.00 3.72 100.00 430

GL-23-3 C2.1 1.86 1.17 0.93 23.31 1.17 0.23 0.23 0.00 0.23 0.00 16.08 5.59 49.18 100.00 429

GL-260-1 C2.1 9.26 2.31 0.69 14.12 1.62 0.00 6.48 0.00 0.00 0.00 18.29 3.70 43.52 100.00 432

GL-1-2 B1.1 10.21 5.41 1.80 15.62 5.71 0.00 4.20 0.00 0.30 0.00 38.14 6.31 12.31 100.00 333

GL-2-1 B1.1 21.43 6.85 1.49 10.42 0.00 0.00 0.30 0.00 0.00 0.00 57.14 0.30 2.08 100.00 336

GL-2-4 B1.1 5.36 1.79 6.25 15.18 0.30 0.00 5.06 0.00 0.00 0.00 55.65 3.57 6.85 100.00 336

GL-3-1 B1.1 5.72 2.71 5.72 12.05 0.00 0.00 2.71 0.00 0.00 0.00 62.35 4.22 4.52 100.00 332

GL-3-8 B1.1 4.33 2.79 3.41 15.17 1.24 0.00 3.72 0.00 0.00 0.00 63.47 2.48 3.41 100.00 323

GL-4-1 B1.1 9.52 0.89 4.46 30.36 4.17 0.30 2.08 0.00 0.30 0.00 27.38 8.63 11.90 100.00 336

GL-6-1 B1.1 4.83 2.72 2.42 16.01 4.83 2.11 5.74 0.00 0.30 0.00 32.33 6.34 22.36 100.00 331

GL-8-6 B1.1 5.72 2.41 2.11 30.42 3.01 1.20 4.82 0.00 0.30 0.00 31.33 10.24 8.43 100.00 332

GL-9-3 B1.1 4.78 4.48 2.09 14.63 2.69 1.79 4.48 0.00 0.30 0.00 27.16 8.96 28.66 100.00 335

GL-10-1 B1.1 8.66 3.28 3.28 21.19 1.49 0.30 3.88 0.00 0.60 0.00 34.33 14.33 8.66 100.00 335

GL-12-2 B1.1 3.63 2.42 3.63 31.42 2.11 0.30 4.83 0.00 0.00 0.00 25.68 12.99 12.99 100.00 331

GL-13-1 B1.1 10.78 5.69 4.49 25.75 0.60 0.30 0.30 0.00 0.60 0.00 39.52 2.69 9.28 100.00 334

GL-13-2 B1.1 2.10 1.80 3.00 21.32 1.20 0.90 1.80 0.00 0.30 0.00 28.23 9.01 30.33 100.00 333

GL-13-3 B1.1 2.39 1.79 1.49 11.64 1.79 1.19 3.28 0.00 0.60 0.00 37.91 7.16 30.75 100.00 335

GL-14A-1 B1.1 12.20 4.17 6.85 34.23 1.49 2.98 1.19 0.00 0.30 0.00 31.55 0.89 4.17 100.00 336

GL-14B-1 B1.1 2.69 1.79 0.00 20.90 0.90 2.39 0.60 0.00 0.30 0.00 29.85 8.36 32.24 100.00 335

GL-17-3 B1.1 2.69 2.39 1.19 20.00 2.99 0.90 2.99 0.00 0.00 0.00 31.64 5.67 29.55 100.00 335

GL-17-4 B1.1 6.57 4.18 2.99 15.22 2.99 0.60 4.78 0.00 0.30 0.00 29.25 6.87 26.27 100.00 335

GL-18-1 B1.1 13.13 1.19 8.96 24.48 0.60 0.60 1.79 0.00 0.30 0.00 34.03 0.30 14.63 100.00 335

GL-18-6 B1.1 3.87 0.89 0.89 18.15 2.08 0.00 0.89 0.00 0.00 0.00 32.44 5.95 34.82 100.00 336

GL-19-2 B1.1 2.56 1.63 0.47 15.15 1.86 0.23 1.17 0.00 0.00 0.00 26.11 2.56 48.25 100.00 429

GL-21B-2 B1.1 3.78 3.55 2.60 19.39 2.13 0.00 3.78 0.00 0.00 0.00 23.40 4.49 36.88 100.00 423

GL-23-1 B1.1 15.81 3.72 2.79 29.30 1.86 0.47 0.00 0.00 0.23 0.00 33.95 2.56 9.30 100.00 430

GL-24-2 B1.1 4.41 0.46 0.46 20.42 2.55 0.00 3.25 0.00 0.23 0.00 11.14 1.62 55.45 100.00 431

GL-25-2 B1.1 5.81 2.33 0.23 11.40 1.40 0.47 0.47 0.00 0.00 0.00 27.91 5.12 44.88 100.00 430

GL-25-5 B1.1 2.32 1.86 0.23 21.11 2.32 0.70 3.02 0.00 0.23 0.00 17.63 3.71 46.87 100.00 431

GL-201-4 B1.1 3.26 3.73 0.93 18.65 1.63 0.00 1.40 0.23 0.00 0.00 17.02 9.09 44.06 100.00 429

GL-219-1 B1.1 0.70 1.63 1.40 38.37 0.23 0.23 1.16 0.00 0.00 0.00 25.81 1.40 29.07 100.00 430

Sample: section number-sample number

Lithofacies: C2.1=classical thick bedded turbidite, B1.1=massive sandstone

Quatz grains: Qm=monocrystalline; Qp=polycrystalline (not including chert)

Feldspar grains: Fk=kspar (potassium), Fp=plagioclase

Lithic sedimentary grains: Lsc=chert, Lsm=mudstone, Lsl=limestone, dolostone and fossils

Lithic metamorphic grains: Lmp=phyllite. Lms=schist

Lithic volcanic grains: Lvv=vitric texture, Lvf=felsitic texture, Lvm=microlitic texture, Lvl=lathwork texture

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Table 6. Calculated lithogeochemical data, Dezadeash Formation, Yukon, Canada.

Sample Lithofacies ¹ CIA ² ICV ³ SiO2/Al2O3 Fe2O3/K2O Cr/Ni Cr/Th Cr/V La/Co La/Sc La/Y La/Yb Th/Co Th/Sc Th/U Y/Ni Zr/Sc ∑LREE ¹¹ ∑HREE ¹² ∑LREE/∑HREE ¹³ ∑REE ²¹ (Gd/Yb)N ²² (La/Lu)N ²³ (La/Sm)N ³¹ (La/Yb)N ³² Ce/Ce* ³³ Eu/Eu* ³³³

GL-2-3 conglomerate (A1.1) 47.48 1.49 3.61 3.93 2.33 22.36 0.39 1.22 0.94 0.76 8.08 0.16 1.66 1.60 0.77 6.17 79.39 13.64 5.82 94.30 1.28 5.61 2.48 5.46 0.91 0.98

GL-6-2 conglomerate (A1.1) 39.44 1.65 3.99 3.32 3.00 32.49 0.53 1.04 1.15 0.81 9.66 0.14 0.16 1.43 0.81 5.75 88.91 14.24 6.24 104.78 1.64 6.61 2.82 6.52 0.93 1.16

GL-3-5 pebbly sandstone (A1.4) 35.32 1.48 3.94 5.52 2.33 24.22 0.38 0.87 0.81 0.73 7.44 0.17 0.16 1.28 0.68 5.93 68.41 12.75 5.36 82.36 1.38 5.10 2.57 5.03 0.92 1.04

GL-9-4 pebbly sandstone (A1.4) 41.32 1.67 3.76 3.38 2.21 14.59 0.41 0.93 1.02 1.02 8.81 0.25 0.28 1.47 0.55 na na na na na na 6.04 4.09 5.95 na na


GL-12-1 pebbly sandstone (A1.4) 34.61 1.91 3.75 2.94 2.60 14.94 0.44 0.86 na 0.63 46.62 0.27 na 2.04 0.88 na 66.90 11.37 5.88 79.17 1.22 4.10 2.12 4.11 1.01 0.87


GL-4-8 pebbly sandstone (A1.4) 1.00 56.50 3.53 2.33 na na na 8.68 na 0.62 11.89 0.32 na 0.09 na na 29.43 4.94 5.94 34.69 1.45 7.46 4.17 8.04 1.05 0.72

GL-208-1 conglomerate (A2.3) 39.30 1.70 3.48 3.33 1.83 13.58 0.47 1.09 na 1.04 13.62 0.24 na 2.19 0.58 na 93.63 11.19 8.37 106.01 1.66 3.16 3.13 9.21 0.95 0.96

average 34.07 7.83 3.68 4.14 2.45 22.48 0.435 1.84 0.93 0.79 13.66 0.21 0.42 1.47 0.72 5.62 73.14 11.90 6.17 86.18 1.46 5.51 2.94 6.19 0.96 0.97

GL-1-5 sandstone (B1.1) 31.87 1.93 3.78 3.92 2.50 14.58 0.37 1.32 1.34 0.87 9.20 0.26 0.27 1.52 0.98 7.58 77.1 11.97 6.44 90.2 1.37 6.4 2.84 6.22 0.93 0.99

GL-2-1 sandstone (B1.1) 51.41 1.26 4.04 7.32 4.00 50.42 0.75 0.92 0.91 0.82 7.88 0.14 0.14 2.59 0.64 5.99 70.36 12.12 5.80 83.61 1.24 5.35 2.87 5.33 0.95 1.07

GL-2-4 sandstone (B1.1) 50.48 1.41 3.17 3.65 3.50 24.05 0.40 0.76 0.73 0.70 7.38 0.15 0.15 1.67 1.09 6.33 70.52 12.94 5.45 84.65 1.43 5.07 2.33 4.99 0.96 1.00

GL-3-1 sandstone (B1.1) 49.58 1.28 3.67 3.49 0.50 22.81 0.36 0.83 0.78 0.74 7.31 0.16 0.15 1.83 0.60 5.65 60.49 11.28 5.36 72.92 1.31 5.04 2.63 4.94 0.94 1.15

GL-4-1 sandstone (B1.1) 41.84 1.50 3.76 5.39 2.33 18.97 0.50 1.23 11.24 0.95 9.83 0.26 0.24 1.78 0.60 6.80 75.93 12.02 6.32 89.18 1.51 6.69 2.98 6.64 0.93 1.09

GL-6-1 sandstone (B1.1) 42.86 1.78 3.71 8.67 3.00 30.82 0.45 0.84 0.75 0.75 7.79 0.15 0.13 1.69 0.75 5.31 78.62 14.33 5.49 94.35 1.46 5.43 2.51 5.26 0.93 1.05

GL-8-6 sandstone (B1.1) 44.61 1.83 3.63 5.74 2.60 37.68 0.65 0.63 0.71 0.85 9.00 0.15 0.17 1.77 0.34 5.57 68.81 10.88 6.32 80.51 1.56 6.18 2.57 6.08 0.95 1.1

GL-9-3 sandstone (B1.1) 27.45 2.62 3.60 9.07 3.00 19.87 0.49 1.24 1.24 1.07 11.93 0.21 0.21 1.89 0.81 6.43 116.14 15.45 7.52 133.14 1.73 8.33 2.90 8.06 0.93 0.92

GL-10-1 sandstone (B1.1) 39.05 1.88 3.83 11.72 2.33 15.69 0.39 0.79 0.90 0.79 8.32 0.25 0.24 1.90 0.71 7.65 77.41 13.14 5.88 91.68 1.39 5.66 2.80 5.63 0.97 0.95

GL-12-2 sandstone (B1.1) 42.16 1.58 3.68 6.40 2.30 19.23 0.46 1.10 1.15 1.04 10.45 0.21 0.22 1.81 0.60 6.56 83.64 11.96 6.99 96.87 1.53 6.56 2.80 6.49 0.96 1.07

GL-13-2 sandstone (B1.1) 49.40 1.28 3.27 6.46 na 20.92 0.34 0.81 0.75 7.20 7.30 0.14 0.13 1.89 na 5.57 64.96 12.27 5.29 78.46 1.40 5.03 2.47 4.93 0.95 1.11

GL-17-4 sandstone (B1.1) 49.85 1.53 3.65 4.54 4.00 29.3 0.45 0.93 0.86 0.82 8.37 0.16 0.15 1.74 0.96 5.49 72.79 12.68 5.74 86-72 1.49 5.77 2.76 5.65 0.94 1.07

GL-19-2 sandstone (B1.1) 44.81 1.61 3.25 6.06 4.50 34.88 0.40 0.81 0.69 0.81 8.29 0.12 0.10 1.69 1.04 4.38 79.99 13.98 5.72 95.44 1.56 5.79 2.47 5.60 0.95 1.08

GL-20-1 sandstone (B1.1) 22.74 3.07 3.28 5.47 2.50 14.00 0.30 1.52 1.70 1.25 15.7 0.21 0.23 1.83 1.03 6.97 112.95 13.13 8.60 127.57 2.14 10.35 3.20 10.61 0.93 1.00

GL-20-3 sandstone (B1.1) 45.36 1.35 3.57 3.22 2.50 11.09 0.35 1.15 1.29 0.91 7.42 0.32 0.36 1.80 0.88 8.80 76.15 11.39 6.68 87.89 1.18 6.26 2.97 5.36 0.98 0.90

GL-25-1 sandstone (B1.1) 48.38 1.32 3.34 4.92 na 19.38 0.32 0.85 0.81 0.76 7.25 0.15 0.14 2.00 na 5.28 68.1 12.50 5.45 81.79 1.34 5.02 2.53 4.90 0.90 1.05

GL-25-5 sandstone (B1.1) 62.86 0.92 3.28 2.08 1.67 8.12 0.39 1.40 1.09 0.97 8.48 0.51 0.40 1.91 0.58 4.61 73.42 11.31 6.49 88.91 1.17 5.83 3.16 5.74 0.97 0.94

GL-400-3 sandstone (B1.1) 52.45 1.28 3.97 2.36 2.23 24.12 0.39 0.66 0.60 0.63 4.80 0.15 0.14 1.67 0.63 5.03 na na na na na 3.74 2.97 3.20 na na

GL-260-1 sandstone (C2.1) 46.55 1.27 3.16 6.64 1.83 33.86 0.47 0.60 na 0.73 8.32 0.10 na 2.19 0.43 na 51.51 8.76 5.88 61.22 1.47 5.36 2.39 5.62 0.96 1.12

GL-400-1 sandstone (C2.1) 48.67 1.34 3.32 6.95 2.19 19.32 0.28 0.79 0.78 0.83 7.13 0.14 0.14 1.56 0.77 5.47 na na na na na 5.15 3.29 4.85 na na

average 44.62 1.60 3.55 5.70 2.64 23.46 0.43 0.96 1.49 1.17 8.61 0.20 0.20 1.84 0.75 6.08 76.61 12.34 6.19 90.49 1.46 5.95 2.77 5.81 0.95 1.04

GL-12-5 mudstone (C2.3) 59.08 1.25 3.52 4.00 0.78 9.25 0.32 1.39 1.43 0.87 10.18 0.38 0.39 2.08 0.36 8.46 99.07 15.37 6.44 115.71 1.49 4.95 2.21 5.31 0.94 0.87

GL-16-1 mudstone (C2.3) 44.27 1.65 4.13 3.40 1.70 17.41 0.40 0.80 0.75 0.68 6.16 0.27 2.51 1.53 0.42 5.68 na na na na na 4.58 3.77 4.13 na na

GL-219-1 mudstone (C2.3) 45.89 1.37 3.33 10.6 2.00 46.62 0.43 0.66 na 0.75 7.11 0.10 na 2.06 0.37 na 49.57 9.94 4.99 60.49 1.46 4.68 2.41 4.80 0.90 1.10



GL-27-1 mudstone (D2.2) 52.97 1.19 3.73 5.53 5.50 46.6 0.74 0.78 0.71 0.59 5.78 0.15 0.13 2.05 1.07 na 60.47 13.28 4.55 74.9 1.22 3.78 2.35 3.90 0.95 1.05

average 54.28 1.35 3.63 5.25 2.18 25.88 0.44 0.90 0.88 0.73 6.75 0.22 0.68 2.11 0.57 5.97 69.70 12.86 5.33 83.70 1.39 4.39 2.97 4.29 0.93 1.01

GL-352-1 mudstone (E1.1) 68.66 0.76 6.60 2.36 1.66 9.71 0.16 0.78 0.07 0.09 0.38 2.00 0.17 1.14 0.71 7.39 na na na na na 0.22 1.09 0.24 na na

GL-1-3 hemipelagite (G1.1) 9.96 6.08 3.56 2.88 1.86 20.26 2.59 1.19 1.28 0.69 7.34 0.22 0.24 1.77 0.72 5.46 na na na na na 5.15 3.98 4.96 na na


GL-3-2 hemipelagite (G1.1) 7.32 8.25 3.08 4.19 na 20.39 0.34 8.2 na 2.82 47.65 0.19 na 1.32 na na 67.42 9.03 7.47 77.66 1.5 29.77 16.12 32.22 0.83 1.47


GL-12-4 hemipelagite (G1.1) 8.80 7.15 3.42 4.23 na 14.35 0.37 7.90 na 1.66 27.23 0.27 na 1.55 na na 186.61 16.22 11.5 204.79 1.61 16.14 7.54 18.39 0.83 1.18

average 12.53 7.59 3.28 3.01 1.50 18.92 0.82 4.47 2.10 1.48 21.23 0.22 0.22 1.82 0.96 5.97 127.02 12.63 9.49 141.23 1.56 13.32 7.72 14.34 0.83 1.33

Lithofacies ¹ = A1.1 (disorganized conglomerate), A1.4 (pebbly sandstone), A2.3 (graded conglomerate), (B1.1 (massive sandstone), C2.1 (thick bedded turbidite). C2.3 (thin bedded turbidite), D2.2 (thick bedded mudstone), E1.1 (structureless mudstone), G1.1 (lime mudstone)

CIA ² = 100[Al2O3/(Al2O3+Na2O+CaO*+K2O)], the Chemical Index of Alteration, where CaO* represents CaO associated only with silicates (Fedo et al., 1995).

ICV ³ = (Fe2O3+CaO+Na2O+K2O+MgO+MnO+TiO2/Al2O3), the Index of Compositional Variability (Cox et al., 1995).

∑LREE ¹¹ = ∑(La+Ce+Pr+Nd+Sm)

∑HREE ¹² =∑(Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu)

∑LREE/∑HREE ¹³ =∑(La+Ce+Pr+Nd+Sm) /∑(Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu)

∑REE ²¹ = ∑(La+Ce+Pr+Nd+Sm+Eu+Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu)

(Gd/Yb)N ²² = , N=chondrite-normalized

(La/Lu)N ²³ = , N=chondrite-normalized

(La/Sm)N ³¹ = , N=chondrite-normalized

(La/Yb)N ³² = , N=chondrite-normalized

Ce/Ce* ³³ = CeN/[(LaN)(PrN)]½

, N=chondrite-normalized

Eu/Eu* ³³³ = EuN/[(SmN)(GdN)]½, N=chondrite-normalized

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Draft

Table 7. Sm-Nd isotopic data, Dezadeash Formation, Yukon, Canada. ____________________________________________________________________________________________________________________________________________________________________________________ Sample Lithology Sm Nd 147Sm/144Nd ±2σ 143Nd/144Nd ±2σ εNd(0)* εNd(149) ƒ Sm/Nd ̽ TDM(Ga)†

(ppm) (ppm)

____________________________________________________________________________________________________________________________________________________________________________________ GL-3-8 sandstone 3.73 18.05 0.12508 0.00013 0.512754 0.000005 +2.3 +3.5 -0.36 0.70 GL-4-8 sandstone 3.81 17.35 0.13262 0.00013 0.512660 0.000004 +0.4 +1.6 -0.33 0.94 GL-9-4 sandstone 3.86 18.03 0.12954 0.00013 0.512634 0.000007 +0.6 +1.9 -0.34 0.90 GL-18-6 sandstone 3.28 14.52 0.13566 0.00014 0.512815 0.000007 +3.4 +4.6 -0.30 0.69 GL-400-1 sandstone 3.91 17.26 0.13697 0.00014 0.512790 0.000005 +3.0 +4.1 -0.30 0.74 GL-400-3 sandstone 2.88 12.02 0.14460 0.00014 0.512788 0.000005 +2.9 +3.9 -0.26 0.82 GL-12-5 mudstone 6.85 31.80 0.13046 0.00013 0.512637 0.000005 0.0 +1.2 -0.34 0.96 GL-16-1 mudstone 3.95 17.69 0.13494 0.00013 0.512645 0.000005 +0.1 +0.1 -0.31 1.00 GL-352-1 mudstone 0.41 0.957 0.25791 0.00026 0.512852 0.000019 +4.2 +3.0 +0.31 na GL-400-2 mudstone 4.48 19.03 0.14226 0.00014 0.512738 0.000004 +1.9 +3.0 -0.28 0.9 GL-400-4 mudstone 4.39 18.67 0.14225 0.00014 0.512755 0.000006 +2.3 +3.3 -0.28 0.9 GL-1-3 hemipelagite 2.42 11.18 0.13087 0.00013 0.512472 0.000019 -3.2 -2.0 -0.33 1.27 GL-2-2 hemipelagite 2.73 12.99 0.12687 0.00013 0.512683 0.000011 +0.9 +2.2 -0.35 0.84 GL-3-2 hemipelagite 2.19 9.86 0.13442 0.00013 0.512658 0.000020 +0.4 +1.6 -0.32 0.97 GL-3-9 hemipelagite 3.34 16.37 0.12336 0.00012 0.512657 0.000019 +0.4 +1.8 -0.37 0.82 GL-9-6 hemipelagite 1.77 10.03 0.10669 0.00011 0.512634 0.000006 -0.1 +1.6 -0.46 0.75 GL-26-1 hemipelagite 3.07 13.40 0.13845 0.00014 0.512711 0.000007 +1.4 +2.5 -0.30 0.90

________________________________________________________________________________________________________________________________________________ *εNd(0)=(143Nd/144Ndmeas/

143Nd/144NdChur-1) x 104; present-day 143Nd/144NdChur=0.512638, normalized to 146Nd/144Nd=0.7219 (DePaolo and Wasserburg, 1976). ̽ ƒSm/Nd=[(147Sm/144Nd)meas/(

147Sm/144Nd)Chur]-1 (DePaolo, 1988). †TDM=(1/λ) x ln[(143Nd/144Ndmeas-

143Nd/144Ndmantle)/ (147Sm/144Ndmeas-

147Sm/144Ndmantle)+1] (DePaolo, 1981), with 143Nd/144Ndmantle=0.513163 and 147Sm/144Ndmantle=0.2138 (Goldstein et al., 1984).

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