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Provenance and paleotectonic setting of North American Triassic strata in Yukon : the sedimentary record… Beranek, Luke P. 2009

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PROVENANCE AND PALEOTECTONIC SETTING OF NORTH AMERICAN TRIASSIC STRATA IN YUKON: THE SEDIMENTARY RECORD OF PERICRATONIC TERRANE ACCRETION IN THE NORTHERN CANADIAN CORDILLERA  by  LUKE PATRICK BERANEK  M.Sc., Idaho State University, 2005 B.Sc., University of Wisconsin - Eau Claire, 2003  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (GEOLOGICAL SCIENCES)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  April 2009  ©Luke Patrick Beranek, 2009  ABSTRACT Detrital mineral geochronology, trace element and Nd isotope geochemistry, and field studies provide constraints for the source and paleotectonic setting of Late Devonian to Late Triassic North American strata in the northern Cordillera. Late Devonian-Early Mississippian clastic wedge deposits in northern Yukon and Northwest Territories record the influx of northerly derived sediment from the Innuitian orogenic belt. Isotopic data suggest that Innuitian clastic material was consistently recycled into post-Late Devonian Cordilleran margin strata. Early to Late Triassic sedimentation in Yukon was related to Late Permian-Early Triassic collision of the pericratonic Yukon-Tanana terrane (YTT) with western North America. Permo-Triassic closure of a marginal back-arc basin, whose remnants comprise the Slide Mountain terrane (SMT), juxtaposed YTT against the ancestral North American margin. The age and nature of this collision is analogous to that of the Sonoman orogeny in the southwestern United States and argues for accretionary tectonism along much of the Cordilleran margin during final construction of the Pangean supercontinent. Three stages of basin evolution following Late Permian-Early Triassic tectonism are now recognized in the northern Cordillera: (1) Early(?) to Middle Triassic SMT-YTT overlap assemblage- Early(?) to Middle Triassic coarse sandstone and conglomerate underlain by SMT in southeastern Yukon have detrital mineral ages which suggest that these strata represent westerly derived, firstcycle deposits shed from YTT following collision. (2) Early(?) to Middle Triassic peripheral foreland basin - Ladinian (Middle Triassic) strata in southeastern Yukon contain detrital mineral ages which document the first known occurrences of sediment derived from allochthonous terranes to the west deposited on North America. These data call for pre-Ladinian peripheral foreland basin development along the former Cordilleran margin. This depocentre is now largely buried under younger Mesozoic allochthons; however, Early(?) to Middle Triassic rocks that comprise the YTT-SMT overlap may represent correlatives to these Ladinian strata. (3) Middle to Late Triassic overlap assemblage – Tectonic quiescence in Middle to Late Triassic time led to development of an overlap assemblage linking the YTT, SMT, and ancestral North American margin. These units comprise a geodynamic linkage between outboard pericratonic terranes and the North American plate.  ii  TABLE OF CONTENTS ABSTRACT ................................................................................................................................................ ii TABLE OF CONTENTS ........................................................................................................................ iii LIST OF TABLES ................................................................................................................................... ix LIST OF FIGURES .................................................................................................................................. x PREFACE ................................................................................................................................................. xii ACKNOWLEDGEMENTS .................................................................................................................xiii CO-AUTHORSHIP STATEMENT ................................................................................................... xiv CHAPTER 1 - INTRODUCTION................................................................................................. 1 1.1 INTRODUCTION....................................................................................................................... 2 1.2 PALEOZOIC DEVELOPMENT OF YUKON-TANANA TERRANE .................................................... 4 1.2.1 Late Devonian - Early Mississippian .............................................................................. 4 1.2.2 Early Mississippian - Middle Permian............................................................................ 6 1.2.3 Middle Permian - Triassic............................................................................................... 6 1.3 EVIDENCE FOR LATE PERMIAN-EARLY TRIASSIC TECTONISM ................................................ 8 1.3.1 Late Permian-Early Triassic magmatic cessation .......................................................... 9 1.3.2 Late Permian-Early Triassic deformation and unconformities....................................... 9 1.3.3 Triassic sedimentary rocks of the eastern Cordillera in western Canada .................... 10 1.4 PROJECT OUTLINE ................................................................................................................. 11 1.4.1 Establishing a detrital zircon reference frame for the post-Devonian Cordilleran miogeocline in northern Canada............................................................................................ 12 1.4.2 Defining provenance correlations between North American Triassic strata in the eastern Canadian Cordillera ................................................................................................. 13 1.4.3 Late Permian-Early Triassic closure of the Slide Mountain-Golconda Ocean ............ 14 1.4.4 Paleogeography of the Late Triassic Bug Island limestone.......................................... 14 1.4.5 Collision-related Triassic sedimentation in southeastern Yukon.................................. 14 1.5 REFERENCES ......................................................................................................................... 16 CHAPTER 2 – DETRITAL ZIRCON GEOCHRONOLOGY OF THE LATE DEVONIAN TO EARLY MISSISSIPPIAN ELLESMERIAN CLASTIC WEDGE, NORTHWESTERN CANADA: INSIGHTS ON THE INNUITIAN OROGEN AND EVOLUTION OF THE NORTHERN CORDILLERAN MIOGEOCLINE...................................................................... 20 2.1 INTRODUCTION..................................................................................................................... 21 2.1.1 Devono-Mississippian deformation in Yukon and Northwest Territories..................... 21 2.1.2 Devono-Mississippian Cordilleran margin strata ........................................................ 22 2.1.3 Provenance of mid-Paleozoic strata in Yukon and Northwest Territories ...................... 23 2.2 INNUITIAN OROGENESIS ....................................................................................................... 23 2.2.1 Early Silurian – Accretion of Pearya ............................................................................ 24 2.2.2 Early Devonian – Romanzof orogeny ........................................................................... 25 2.2.3 Late Devonian to Early Mississippian – Ellesmerian orogeny ..................................... 26 2.3 LATE DEVONIAN AND MISSISSIPPIAN STRATA OF NORTHERN YUKON AND NORTHWEST TERRITORIES .............................................................................................................................. 26 2.3.1 Late Devonian Imperial Formation .............................................................................. 27 2.3.2 Late Devonian to Early Mississippian Tuttle Formation .............................................. 29  iii  2.4 LATE DEVONIAN TURBIDITE BASIN AND MISSISSIPPIAN CLASTIC SHELF OF WEST-CENTRAL AND EASTERN YUKON ................................................................................................................ 31 2.4.1 Late Devonian Prevost Formation, upper Earn Group ................................................ 32 2.4.2 Mississippian Keno Hill Quartzite and Tsichu formation............................................. 32 2.5 PREVIOUS DETRITAL ZIRCON STUDIES AND REFERENCE FRAMES ........................................ 32 2.5.1 Arctic reference frame................................................................................................... 33 2.5.2 Western Laurentian reference frame............................................................................. 33 2.5.3 Provenance correlations ............................................................................................... 34 2.6 ANALYTICAL METHODS AND DATA PRESENTATION ............................................................. 34 2.7 DETRITAL ZIRCON RESULTS.................................................................................................. 36 2.7.1 Late Devonian Imperial Formation .............................................................................. 36 2.7.2 Late Devonian – Early Mississippian Tuttle Formation ............................................... 36 2.7.3 Late Devonian Prevost Formation, upper Earn Group ................................................ 39 2.7.4 Mississippian Keno Hill Quartzite ................................................................................ 39 2.7.5 Mississippian Tsichu formation .................................................................................... 40 2.8 PROVENANCE CORRELATIONS .............................................................................................. 42 2.8.1 Late Devonian Imperial Formation ...................................................................................... 42 2.8.1.1 Interpretation .................................................................................................................. 42 2.8.2 Late Devonian – Early Mississippian Tuttle Formation ............................................... 45 2.8.2.1 Interpretation .................................................................................................................. 45 2.8.3 Late Devonian to Mississippian Cordilleran margin strata ......................................... 46 2.8.3.1 Interpretation .................................................................................................................. 47 2.9 SYNTHESIS ............................................................................................................................ 48 2.10 REFERENCES ....................................................................................................................... 50 CHAPTER 3 – PROVENANCE AND STRATIGRAPHIC FRAMEWORK OF NORTH AMERICAN TRIASSIC STRATA, WEST-CENTRAL TO SOUTHEASTERN YUKON: CORRELATIONS WITH THE WESTERN CANADA SEDIMENTARY BASIN.................... 55 3.1 INTRODUCTION..................................................................................................................... 56 3.1.1 Western Canada Sedimentary Basin ............................................................................. 56 3.1.2 Triassic continental margin strata of Yukon ................................................................. 56 3.1.3 Characterizing North American Triassic strata in Yukon ................................................. 58 3.2 STRATIGRAPHIC FRAMEWORK AND SAMPLE LOCALITIES..................................................... 60 3.2.1 Mount Christie and Jones Lake formation stratotype locations, Selwyn Mountains, eastern Yukon ......................................................................................................................... 60 3.2.2 Mount Christie and Jones Lake formations, Ogilvie Mountains, west-central Yukon .. 64 3.2.3 Jones Lake Formation, Sheldon Lake map area, eastern Yukon .................................. 67 3.2.4 Hoole Formation, Quiet Lake map area, eastern Yukon .............................................. 69 3.2.5 Toad Formation, La Biche River map area, southeasternmost Yukon.......................... 70 3.3 NORTHERN CORDILLERAN REFERENCE FRAMES................................................................... 70 3.3.1 Provenance correlations ............................................................................................... 71 3.4 ANALYTICAL METHODS AND DATA PRESENTATION ............................................................. 71 3.4.1 U-Pb geochronology ..................................................................................................... 71 3.4.2 Ar-Ar geochronology .................................................................................................... 73 3.4.3 Whole-rock trace element and Nd isotope geochemistry .............................................. 74 3.5 NEW CONODONT BIOSTRATIGRAPHY .................................................................................... 74 3.5.1 Mount Christie Formation stratotype ........................................................................... 74 3.5.2 Jones Lake Formation stratotype.................................................................................. 75 3.6 WHOLE-ROCK TRACE ELEMENT GEOCHEMISTRY ................................................................. 76 3.6.1 Mount Christie Formation stratotype ........................................................................... 76 3.6.2 Mount Christie Formation, Ogilvie Mountains............................................................. 76  iv  3.6.3 Jones Lake Formation stratotype.................................................................................. 76 3.6.4 Jones Lake Formation, Ogilvie Mountains ................................................................... 77 3.7 WHOLE-ROCK NEODYMIUM ISOTOPE GEOCHEMISTRY ......................................................... 78 3.7.1 Mount Christie Formation stratotype ........................................................................... 78 3.7.2 Jones Lake Formation stratotype.................................................................................. 78 3.8 DETRITAL MUSCOVITE GEOCHRONOLOGY ........................................................................... 78 3.8.1 Mount Christie Formation stratotype ........................................................................... 78 3.8.2 Jones Lake Formation stratotype .......................................................................................... 78 3.9 DETRITAL ZIRCON GEOCHRONOLOGY .................................................................................. 79 3.9.1 Jones Lake Formation stratotype.................................................................................. 79 3.9.2 Jones Lake Formation, Ogilvie Mountains, west-central Yukon .................................. 80 3.9.3 Jones Lake Formation, Sheldon Lake map area, eastern Yukon .................................. 82 3.9.4 Hoole Formation, Quiet Lake map area, eastern Yukon .............................................. 83 3.9.5 Toad Formation, La Biche River map area, southeasternmost Yukon.......................... 83 3.10 WHOLE-ROCK PROVENANCE CORRELATIONS ..................................................................... 84 3.10.1 Mount Christie Formation .......................................................................................... 84 3.10.2 Jones Lake Formation........................................................................................................... 85 3.11 DETRITAL MINERAL PROVENANCE CORRELATIONS............................................................ 86 3.11.1 Mount Christie and Jones Lake formation stratotypes..................................................... 86 3.11.1.1 Detrital zircon provenance ......................................................................................... 86 3.11.1.2 Detrital muscovite provenance .................................................................................. 87 3.11.2 Jones Lake Formation, Ogilvie Mountains ................................................................. 88 3.11.3 Jones Lake Formation, Sheldon Lake map area ......................................................... 88 3.11.4 Hoole Formation, Quiet Lake map area ..................................................................... 89 3.11.5 Toad Formation, La Biche River map area ................................................................ 90 3.12 CONCLUSIONS ..................................................................................................................... 90 3.13 REFERENCES ....................................................................................................................... 94 CHAPTER 4 – PERMO-TRIASSIC CLOSURE OF THE CORDILLERAN MARGINAL OCEAN BASIN: U-PB DETRITAL ZIRCON AND AR-AR DETRITAL MUSCOVITE CONSTRAINTS FROM TRIASSIC SILICICLASTIC STRATA ASSOCIATED WITH SLIDE MTN. TERRANE IN YUKON, NORTHERN BRITISH COLUMBIA, AND ALASKA ........... 98 4.1 INTRODUCTION ..................................................................................................................... 99 4.1.1 Slide Mountain terrane and related Triassic strata in the northern Cordillera ........... 99 4.1.2 Testable hypotheses for the source of Triassic strata ................................................. 102 4.2 SAMPLE LOCALITIES AND GEOLOGIC FRAMEWORK............................................................ 103 4.2.1 Taylor Highway locality, Eagle quadrangle, eastern Alaska...................................... 103 4.2.2 Clinton Creek asbestos mine, western Yukon.............................................................. 103 4.2.3 Tummel fault zone, Glenlyon map area, central Yukon .............................................. 107 4.2.4 Northern Finlayson Lake district, southeastern Yukon............................................... 109 4.2.5 McNeil Lake klippen, southeastern Yukon .................................................................. 112 4.2.6 Sylvester allochthon, northern British Columbia........................................................ 112 4.3 DETRITAL MINERAL REFERENCE FRAMES FOR THE NORTHERN CORDILLERA .................... 116 4.3.1 Ancestral North American margin .............................................................................. 116 4.3.2 Yukon-Tanana terrane ................................................................................................ 117 4.4 ANALYTICAL METHODS AND DATA PRESENTATION ........................................................... 118 4.4.1 U-Pb geochronology ................................................................................................... 118 4.4.2 Ar-Ar geochronology .................................................................................................. 119 4.5 RESULTS ............................................................................................................................. 120 4.5.1 Taylor Highway locality, Eagle quadrangle, eastern Alaska...................................... 120 4.5.2 Clinton Creek asbestos mine, western Yukon.............................................................. 120  v  4.5.3 Tummel fault zone, Glenlyon map area, central Yukon .............................................. 122 4.5.4 Northern Finlayson Lake district, southeastern Yukon............................................... 124 4.5.5 McNeil Lake klippen, southeastern Yukon .................................................................. 126 4.5.6 Sylvester allochthon, northern British Columbia........................................................ 127 4.6 PROVENANCE CORRELATIONS ............................................................................................ 128 4.6.1 Eastern Alaska – Western Yukon border region ......................................................... 128 4.6.2 Tummel fault zone, Glenlyon map area, central Yukon .............................................. 131 4.6.3 Northern Finlayson Lake district and McNeil Lake klippen, southeastern Yukon...... 134 4.6.4 Sylvester allochthon .................................................................................................... 136 4.7 CONCLUSIONS ..................................................................................................................... 137 4.7.1 New detrital mineral reference frame for the northern Cordillera............................. 137 4.7.2 Triassic stratigraphic linkages in the peri-Laurentian realm ..................................... 137 4.7.3 Paleogeographic implications..................................................................................... 139 4.7.4 Correlations with Sonoman orogenesis ...................................................................... 139 4.8 REFERENCES ....................................................................................................................... 142 CHAPTER 5 – LATE TRIASSIC ‘TETHYAN’ CONODONTS IN THE PERI-LAURENTIAN REALM: NORTH AMERICAN DETRITAL ZIRCONS DE-BUG THE BUG ISLAND LIMESTONE?............................................................................................................................ 149 5.1 INTRODUCTION ................................................................................................................... 150 5.1.1 Review of terrane and paleobiogeographic analysis in the Canadian Cordillera...... 150 5.1.2 Exotic conodonts in the peri-Laurentian realm? ........................................................ 152 5.1.3 Testing models for Tethyan faunal occurrences in the Canadian Cordillera ............. 153 5.2 REGIONAL GEOLOGY OF THE FINLAYSON LAKE MAP AREA ................................................ 155 5.2.1 Yukon-Tanana and Slide Mountain terranes .............................................................. 155 5.2.2 Triassic strata – The Bug Island limestone ................................................................. 156 5.3 DETRITAL ZIRCON REFERENCE FRAMES ............................................................................. 157 5.3.1 Ancestral North American margin .............................................................................. 157 5.3.2 Yukon-Tanana terrane ................................................................................................ 157 5.3.3 Finlayson Lake area.................................................................................................... 158 5.3.4 Late Triassic strata associated with Slide Mountain terrane...................................... 158 5.3.5 Tethyan sequences in Himalaya .................................................................................. 158 5.3.6 Detrital zircon statistics .............................................................................................. 159 5.4 ANALYTICAL METHODS AND DATA PRESENTATION ........................................................... 159 5.5 RESULTS ............................................................................................................................. 160 5.6 PROVENANCE CORRELATIONS ............................................................................................ 161 5.7 DISCUSSION ........................................................................................................................ 162 5.7.1 Detrital zircon provenance.......................................................................................... 162 5.7.2 Evaluation of Tethyan fossils in the Cordillera........................................................... 163 5.8 SYNTHESIS .......................................................................................................................... 167 5.9 REFERENCES ....................................................................................................................... 168 CHAPTER 6 – TRIASSIC PERIPHERAL FORELAND BASIN DEVELOPMENT AND OVERLAP ASSEMBLAGES IN THE NORTHERN NORTH AMERICAN CORDILLERA: NEW INSIGHTS ON THE ACCRETION OF YUKON-TANANA AND RELATED TERRANES ................................................................................................................................ 172 6.1 INTRODUCTION ................................................................................................................... 173 6.1.1 A new model for Permo-Triassic tectonism in the northern Cordillera...................... 173 6.1.2 Testing for collision-related and overlap assemblages in southeastern Yukon .......... 175 6.2 YUKON-TANANA TERRANE ................................................................................................. 177 6.2.1 Overview ..................................................................................................................... 177  vi  6.2.2 Tectonic assemblages of Yukon-Tanana terrane......................................................... 177 6.2.3 Linkages between Yukon-Tanana and other terranes ................................................. 179 6.3 SAMPLE LOCALITIES AND GEOLOGIC SETTING ................................................................... 179 6.3.1 Middle Triassic strata, Frances Lake map area, southeastern Yukon ........................ 179 6.3.2 Middle Triassic strata, Watson Lake map area, southeastern Yukon ......................... 181 6.3.3 Middle to Late Triassic strata, Cassiar terrane, Quiet Lake map area ...................... 182 6.3.4 Middle to Late Triassic strata, Cassiar terrane, Finlayson Lake map area ............... 184 6.3.5 Late Triassic(?) Faro Peak formation, Yukon-Tanana terrane, central Yukon .......... 185 6.3.6 Middle to Late Jurassic strata, Dawson map area, west-central Yukon..................... 186 6.4 NORTH AMERICAN CONTINENTAL MARGIN REFERENCE FRAMES ....................................... 188 6.4.1 Cordilleran margin strata ........................................................................................... 188 6.4.2 Detrital zircon statistics .............................................................................................. 189 6.5 ANALYTICAL METHODS AND DATA PRESENTATION ........................................................... 189 6.5.1 U-Pb geochronology ................................................................................................... 189 6.5.2 Ar-Ar geochronology .................................................................................................. 191 6.5.3 Whole-rock trace element and Nd isotope geochemistry ............................................ 192 6.6 WHOLE-ROCK TRACE ELEMENT GEOCHEMISTRY ............................................................... 192 6.6.1 Middle Triassic strata, Frances and Watson Lake map areas.................................... 192 6.6.2 Middle to Late Triassic strata, Cassiar terrane, Finlayson Lake map area ............... 192 6.6.3 Middle to Late Jurassic strata, Dawson map area, west-central Yukon..................... 193 6.7 WHOLE-ROCK NEODYMIUM ISOTOPE GEOCHEMISTRY ....................................................... 195 6.7.1 Middle Triassic strata, Frances Lake map area ......................................................... 195 6.7.2 Middle Triassic strata, Watson Lake map area .......................................................... 195 6.8 DETRITAL ZIRCON GEOCHRONOLOGY ................................................................................ 195 6.8.1 Middle Triassic strata, Frances and Watson Lake map areas, southeastern Yukon... 195 6.8.2 Middle to Late Triassic strata, Cassiar terrane, southeastern Yukon......................... 196 6.8.3 Faro Peak formation, Yukon-Tanana terrane, central Yukon..................................... 197 6.8.4 Jurassic Lower Schist division, Dawson map area, west-central Yukon .................... 197 6.9 DETRITAL MUSCOVITE GEOCHRONOLOGY ......................................................................... 198 6.9.1 Middle Triassic strata, Frances Lake map area ......................................................... 198 6.9.2 Middle to Late Triassic strata, Cassiar terrane, Finlayson Lake map area ............... 199 6.10 WHOLE-ROCK PROVENANCE CORRELATIONS ................................................................... 199 6.10.1 Middle Triassic strata, Frances and Watson Lake map areas.................................. 199 6.10.2 Middle to Late Triassic strata, Cassiar terrane, southeastern Yukon....................... 200 6.10.3 Middle to Late Jurassic strata, west-central Yukon .................................................. 201 6.11 DETRITAL MINERAL PROVENANCE CORRELATIONS.......................................................... 202 6.11.1 Middle Triassic strata, Frances and Watson Lake map areas ...................................... 202 6.11.1.1 Interpretation .............................................................................................................. 205 6.11.2 Middle to Late Triassic strata, Hoole Formation, Cassiar terrane .......................... 205 6.11.2.1 Interpretation .............................................................................................................. 206 6.11.3 Middle to Late Triassic strata, Cassiar terrane, Finlayson Lake map area ............. 206 6.11.3.1 Interpretation .............................................................................................................. 207 6.11.4 Faro Peak formation, Yukon-Tanana terrane, central Yukon................................... 207 6.11.4.1 Interpretation .............................................................................................................. 208 6.11.5 Middle to Late Jurassic strata, Dawson map area, west-central Yukon................... 209 6.11.5.1 Interpretation .............................................................................................................. 210 6.12 TRIASSIC PERIPHERAL FORELAND BASIN DEVELOPMENT ................................................. 210 6.12.1 Interpretation ....................................................................................................................... 212 6.13 TRIASSIC OVERLAP ASSEMBLAGE DEVELOPMENT ............................................................ 213 6.14 SYNTHESIS ........................................................................................................................ 214 6.15 REFERENCES ..................................................................................................................... 215  vii  CHAPTER 7 – CONCLUSIONS AND DIRECTIONS FOR FUTURE RESEARCH ........... 221 7.1 CONTRIBUTIONS TO THE CORDILLERAN KNOWLEDGE BASE .............................................. 222 7.2 KEY RESULTS ...................................................................................................................... 223 7.3 FUTURE RESEARCH ............................................................................................................. 224 7.4 REFERENCES ....................................................................................................................... 228 APPENDICES ........................................................................................................................... 230 APPENDIX A – CHAPTER 2 DATA REPOSITORY ...................................................................... 231 APPENDIX B – CHAPTER 3 DATA REPOSITORY ....................................................................... 253 U-PB DETRITAL ZIRCON DATA .................................................................................................. 254 TRACE ELEMENT GEOCHEMICAL DATA .................................................................................... 268 AR-AR DETRITAL MUSCOVITE DATA ........................................................................................ 270 SM-ND ISOTOPIC DATA ............................................................................................................. 270 CONODONT BIOCHRONOLOGY (REPORT FROM M.J. ORCHARD) ................................................ 271 APPENDIX C – CHAPTER 4 DATA REPOSITORY ...................................................................... 273 U-PB DETRITAL ZIRCON DATA .................................................................................................. 274 AR-AR DETRITAL MUSCOVITE DATA ........................................................................................ 304 APPENDIX D – CHAPTER 5 DATA REPOSITORY ...................................................................... 305 APPENDIX E – CHAPTER 6 DATA REPOSITORY ....................................................................... 308 U-PB DETRITAL ZIRCON DATA .................................................................................................. 309 TRACE ELEMENT GEOCHEMICAL DATA .................................................................................... 323 AR-AR DETRITAL MUSCOVITE DATA ........................................................................................ 324 SM-ND ISOTOPIC DATA ............................................................................................................. 324  viii  LIST OF TABLES TABLE 2.1  DETRITAL ZIRCON AGE PEAKS IN THE NORTHERN CORDILLERA.......................... 37  TABLE 3.1  WHOLE-ROCK GEOCHEMICAL REFERENCE FRAME IN NORTHERN CORDILLERA .. 79  TABLE 3.2  DETRITAL ZIRCON AGE PEAKS IN THE NORTHERN CORDILLERA.......................... 81  TABLE 4.1  DETRITAL ZIRCON AGE PEAKS IN THE NORTHERN CORDILLERA........................ 125  TABLE 5.1  DETRITAL ZIRCON AGE PEAKS IN THE NORTHERN CORDILLERA........................ 164  TABLE 6.1 TABLE 6.2  WHOLE-ROCK AND ND ISOTOPE GEOCHEMISTRY IN NORTHERN CORDILLERA .. 194 DETRITAL ZIRCON AGE PEAKS IN THE NORTHERN CORDILLERA........................ 204  TABLE A1  LOCATION DATA FOR DETRITAL ZIRCON SAMPLES IN CHAPTER 2 ..................... 231  TABLE B1 TABLE B2 TABLE B3 TABLE B4  LOCATION DATA FOR DETRITAL ZIRCON SAMPLES IN CHAPTER 3 ..................... 253 LOCATION DATA FOR WHOLE-ROCK GEOCHEMICAL SAMPLES IN CHAPTER 3 ... 253 LOCATION DATA FOR AR-AR SAMPLES IN CHAPTER 3........................................ 253 LOCATION DATA FOR ND ISOTOPE SAMPLES IN CHAPTER 3 ............................... 253  TABLE C1 TABLE C2  LOCATION DATA FOR DETRITAL ZIRCON SAMPLES IN CHAPTER 4 ..................... 273 LOCATION DATA FOR AR-AR SAMPLES IN CHAPTER 4........................................ 273  TABLE D1  LOCATION DATA FOR DETRITAL ZIRCON SAMPLE IN CHAPTER 5....................... 305  TABLE E1 TABLE E2 TABLE E3 TABLE E4  LOCATION DATA FOR DETRITAL ZIRCON SAMPLES IN CHAPTER 6 ..................... 308 LOCATION DATA FOR DETRITAL ZIRCON SAMPLES IN CHAPTER 6 ..................... 308 LOCATION DATA FOR AR-AR SAMPLES IN CHAPTER 6 ........................................ 308 LOCATION DATA FOR ND ISOTOPE SAMPLES IN CHAPTER 6 ............................... 308  ix  LIST OF FIGURES FIGURE 1.1 FIGURE 1.2 FIGURE 1.3 FIGURE 1.4  TECTONIC ELEMENTS OF NORTH AMERICAN CORDILLERA .................................. 3 TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ............................... 5 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES....................... 7 U-PB AND FOSSIL AGES FOR ROCKS OF YUKON-TANANA TERRANE ..................... 8  FIGURE 2.1 FIGURE 2.2 FIGURE 2.3 FIGURE 2.4 FIGURE 2.5 FIGURE 2.6 FIGURE 2.7 FIGURE 2.8 FIGURE 2.9 FIGURE 2.10 FIGURE 2.11 FIGURE 2.12  PHANEROZOIC OROGENIC BELTS OF NORTH AMERICA ....................................... 22 GEOLOGIC MAP OF ARCTIC ALASKA, NORTHERN YUKON, AND NWT ................. 24 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES..................... 25 DEV.-MISS. STRATIGRAPHIC AND TECTONIC FRAMEWORK IN N. YUKON, NWT .. 27 TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ............................. 28 IMPERIAL AND TUTTLE FORMATION SAMPLE MAP IN N. RICHARDSON MTNS..... 30 IMPERIAL AND TUTTLE FORMATION SAMPLE MAP IN PEEL PLATEAU ................ 31 DETRITAL ZIRCON AGE SPECTRA FOR IMPERIAL FORMATION SAMPLES ............ 38 DETRITAL ZIRCON AGE SPECTRA FOR TUTTLE FORMATION STRATA ................. 40 DETRITAL ZIRCON AGE SPECTRA FOR MISSISSIPPIAN STRATA ........................... 41 NORMALIZED RELATIVE PROBABILITY PLOT FOR CHAPTER 2 SAMPLES ............ 44 LATE DEVONIAN-EARLY MISSISSIPPIAN GLOBAL PALEOGEOGRAPHY. .............. 49  FIGURE 3.1 FIGURE 3.2 FIGURE 3.3 FIGURE 3.4 FIGURE 3.5 FIGURE 3.6 FIGURE 3.7 FIGURE 3.8 FIGURE 3.9 FIGURE 3.10 FIGURE 3.11 FIGURE 3.12 FIGURE 3.13 FIGURE 3.14 FIGURE 3.15 FIGURE 3.16 FIGURE 3.17 FIGURE 3.18 FIGURE 3.19 FIGURE 3.20  TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ............................. 57 NORTH AMERICAN TRIASSIC ROCKS IN YUKON .................................................. 59 TRIASSIC STRATIGRAPHIC FRAMEWORK IN E. CANADIAN CORDILLERA ............ 60 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES..................... 61 BEDROCK GEOLOGY OF THE WILSON SYNCLINE AREA....................................... 63 PANORAMIC VIEW OF THE WILSON SYNCLINE.................................................... 63 STRATIGRAPHIC COLUMN FOR WESTERN LIMB OF WILSON SYNCLINE............... 64 OUTCROP PICTURES OF MT. CHRISTIE AND JONES LAKE FM. STRATOTYPES ...... 65 BEDROCK GEOLOGY OF MOUNT ROBERT SERVICE AREA ................................... 66 OUTCROP PICTURES OF MT. CHRISTIE AND JONES LK. FM. IN OGILVIE MTNS ..... 67 SIMPLIFIED BEDROCK GEOLOGY OF CONNOLLY CALDERA AREA ...................... 68 OUTCROP PICTURES OF THE CONNOLLY CALDERA AREA. ................................. 68 SIMPLFIED BEDROCK GEOLOGY ALONG S. CANOL RD. SOUTH OF ROSS RIVER .. 69 OUTCROP PICTURES OF HOOLE FORMATION ...................................................... 70 CHONDRITE-NORMALIZED REE PLOTS, MT. CHRISTIE AND JONES LK. FMS. ....... 77 DETRITAL ZIRCON AGE SPECTRA FOR JONES LAKE FM. STRATOTYPE ................ 82 DETRITAL ZIRCON AGE SPECTRA FOR JONES LAKE FM., OGILVIE MTNS. ........... 83 DETRITAL ZIRCON AGE SPECTRA FOR VARIOUS TRIASSIC SAMPLES .................. 84 147 144 INITIAL EPSILON ND VERSUS SM/ ND PLOT ................................................. 91 NORMALIZED RELATIVE PROBABILITY PLOT FOR CHAPTER 3 SAMPLES ............ 92  FIGURE 4.1 FIGURE 4.2 FIGURE 4.3 FIGURE 4.4 FIGURE 4.5 FIGURE 4.6 FIGURE 4.7A FIGURE 4.7B FIGURE 4.8A  TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ........................... 100 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES................... 102 TRIASSIC STRATIGRAPHIC FRAMEWORK FOR THE SLIDE MTN. TERRANE ......... 104 SIMPLIFIED BEDROCK GEOLOGY OF E. ALASKA/W. YUKON BORDER REGION.. 105 SIMPLIFIED BEDROCK GEOLOGY OF CLINTON CREEK MINE AREA .................... 106 BEDROCK GEOLOGY OF TUMMEL FAULT ZONE, GLENLYON MAP AREA. .......... 108 SIMPLIFIED BEDROCK GEOLOGY OF N. FINLAYSON LAKE AREA....................... 110 SCHEMATIC STRATIGRAPHIC SECTION THROUGH N. FINLAYSON LK. AREA ..... 111 SIMPLIFIED BEDROCK GEOLOGY OF MCNEIL LAKE AREA ................................. 113  x  FIGURE 4.8B FIGURE 4.9 FIGURE 4.10 FIGURE 4.11 FIGURE 4.12 FIGURE 4.13 FIGURE 4.14 FIGURE 4.15 FIGURE 4.16  SCHEMATIC OPTIONS FOR STRATIGRAPHY IN MCNEIL LAKE AREA .................. 113 BEDROCK GEOLOGY OF CUSAC GOLD PROPERTY, TABLE MTN. AREA .............. 115 DETRITAL ZIRCON AGE SPECTRA FOR CLINTON CK. AND E. AK SAMPLES . ...... 121 DETRITAL ZIRCON AGE SPECTRA FOR GLENLYON MAP AREA .......................... 123 DETRITAL ZIRCON AGE SPECTRA OF N. FINLAYSON AND MCNEIL LK. AREAS .. 126 DETRITAL ZIRCON AGE SPECTRA FOR SYLVESTER ALLOCHTHON.................... 129 DETRITAL MUSCOVITE AGE SPECTRA .............................................................. 130 NORMALIZED RELATIVE PROBABILITY PLOT FOR CHAPTER 4 SAMPLES.......... 132 LATE PERMIAN – EARLY TRIASSIC GLOBAL PALEOGEOGRAPHY...................... 141  FIGURE 5.1 FIGURE 5.2 FIGURE 5.3 FIGURE 5.4 FIGURE 5.5 FIGURE 5.6 FIGURE 5.7  TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ........................... 151 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES................... 153 LATE TRIASSIC GLOBAL PALEOGEOGRAPHY .................................................... 154 SIMPLIFIED BEDROCK GEOLOGY OF NORTHERN FINLAYSON LAKE AREA ........ 155 SCHEMATIC STRATIGRAPHIC SECTION THROUGH N. FINLAYSON LK. AREA ..... 156 DETRITAL ZIRCON AGE SPECTRA FOR THE BUG ISLAND LIMESTONE. .............. 161 NORMALIZED RELATIVE PROBABILITY PLOT ................................................... 165  FIGURE 6.1 FIGURE 6.2 FIGURE 6.3 FIGURE 6.4 FIGURE 6.5 FIGURE 6.6 FIGURE 6.7 FIGURE 6.8 FIGURE 6.9 FIGURE 6.10 FIGURE 6.11 FIGURE 6.12 FIGURE 6.13 FIGURE 6.14 FIGURE 6.15 FIGURE 6.16 FIGURE 6.17 FIGURE 6.18 FIGURE 6.19 FIGURE 6.20  TERRANE MAP OF ALASKAN AND CANADIAN CORDILLERAS ........................... 174 PALEOZOIC PALEOGEOGRAPHY OF PERI-LAURENTIAN TERRANES................... 178 NORTH AMERICAN TRIASSIC ROCKS IN YUKON ................................................ 180 SIMPLIFIED BEDROCK GEOLOGY OF FINLAYSON AND FRANCES LAKE AREAS . 181 SIMPLIFIED BEDROCK GEOLOGY OF N. WATSON LAKE MAP AREA ................... 183 SIMPLIFIED BEDROCK GEOLOGY ALONG S. CANOL RD., MT. GREEN AREA....... 183 SIMPLIFIED BEDROCK GEOLOGY OF MCNEIL LAKE AREA ................................. 184 BEDROCK GEOLOGY NEAR FARO TOWNSITE .................................................... 186 BEDROCK GEOLOGY NEAR BLIND CREEK, EAST OF FARO ................................ 187 BEDROCK GEOLOGY OF MOUNT ROBERT SERVICE AREA ................................. 188 CHONDRITE-NORMALIZED REE PLOTS, TRIASSIC AND JURASSIC STRATA ........ 193 DETRITAL ZIRCON AGE SPECTRA FOR FRANCES AND WATSON LK. AREAS. ..... 196 DETRITAL ZIRCON AGE SPECTRA FOR CASSIAR TERRANE SAMPLES ................ 197 DETRITAL ZIRCON AGE SPECTRA FOR THE FARO PEAK FORMATION ................ 198 DETRITAL ZIRCON AGE SPECTRA FOR THE LOWER SCHIST DIVISION. .............. 198 DETRITAL MUSCOVITE AGE SPECTRA FROM MCNEIL LAKE AREA .................... 199 147 144 INITIAL EPSILON ND VERSUS SM/ ND PLOT. .............................................. 201 DISTRIBUTION OF LATE TRIASSIC TO MID-JURASSIC INTRUSIVES IN YUKON ... 209 SCHEMATIC PERIPHERAL FORELAND BASIN .................................................... 211 ESTIMATES ON PERIPHERAL FORELAND BASIN FACIES BELTS ......................... 213  xi  PREFACE  There’s gold, and it’s haunting and haunting; It’s luring me on as of old; Yet it isn’t the gold that I’m wanting So much as just finding the gold. It’s the great, big, broad land ‘way up yonder, It’s the forests where silence has lease; It’s the beauty that thrills me with wonder, It’s the stillness that fills me with peace.  -Robert Service, From The Spell of the Yukon  xii  ACKNOWLEDGEMENTS This dissertation benefited from the assistance of many people. I am indebted to my supervisor Jim Mortensen who proposed this project and introduced me to the many wonders of Yukon. Jim provided constant moral and scientific support in an independent, free-thinking work environment that exceeded my expectations. The large analytical database produced by this project was fully funded by NSERC Discovery grants to Mortensen. Maurice Colpron and Don Murphy from the Yukon Geological Survey and JoAnne Nelson from the British Columbia Geological Survey were fantastic mentors that fostered this project since its inception. Conversations and time in the field with them greatly improved my understanding and appreciation of regional tectonics and sedimentation. Maurice Colpron is also thanked for sharing many of his phenomenal illustrations. Field logistics and helicopter budget for this project over three summers was supported by the Yukon Geological Survey. Co-advisors Michael Orchard at the Geological Survey of Canada and Stuart Sutherland and Paul Smith at the University of British Columbia (UBC) are thanked for their many comments and conversations regarding paleontology and Cordilleran geology. Richard Friedman at the Pacific Centre for Isotopic and Geochemical Research at UBC has been a tremendous personal and scientific resource. His positive demeanor and knowledge of U-Pb zircon geochronology were highly appreciated on a daily basis. I am thankful for my remarkable colleagues and friends at UBC, past and present, including Elspeth Barnes, Andrew Caruthers, Evan Crawford, Sarah Gordee, Amber Henry, Chris Leslie, the lovely Inês Nobre Silva, Kirsten Rasmussen, Tyler Ruks, and Reza Tafti. Mary Jessica Della Vedova is also thanked for her patience and friendship. Finally, my parents and family have provided unwavering support for my scientific and personal desires during the past 10 years of university studies. I thank them for coming on this journey with me.  xiii  CO-AUTHORSHIP STATEMENT The five manuscripts of this dissertation are coauthored with several colleagues. I designed the research programme with my supervisor Jim Mortensen, acted as the principal investigator for field and U-Pb analytical studies, and I was the primary author for all manuscripts. My supervisor Jim Mortensen offered comments and revisions to each of the five manuscripts. Tom Ullrich conducted all Ar-Ar muscovite geochronology. General contributions from coauthors are outlined below and stated in section 1.4. CHAPTER 2 Detrital zircon geochronology of the Late Devonian to Early Mississippian Ellesmerian clastic wedge, northwestern Canada: Insights on the Innuitian orogen and evolution of the northern Cordilleran miogeocline Authors: Beranek, L.P., Allen, T., Fraser, T., Hadlari, T., Lane, L., Mortensen, J.K., and Zantvoort, W. Coauthors Allen, Fraser, Hadlari, Lane, Mortensen, and Zantvoort provided samples for analysis and general comments about regional geology. CHAPTER 3 Provenance and stratigraphic framework of North American Triassic strata, westcentral to southeastern Yukon: Correlations with the Western Canada Sedimentary Basin Authors: Beranek, L.P., Mortensen, J.K., Orchard, M.J., and Ullrich, T. Coauthor Orchard conducted all conodont biochronology and offered comments on an earlier version of this manuscript. CHAPTER 4 Permo-Triassic closure of the Cordilleran marginal ocean basin: U-Pb detrital zircon and Ar-Ar detrital muscovite constraints from Triassic siliciclastic strata associated with Slide Mountain terrane in Yukon, northern British Columbia, and eastern Alaska Authors: Beranek, L.P., Mortensen, J.K., and Ullrich, T. CHAPTER 5 Late Triassic ‘Tethyan’ conodonts in the peri-Laurentian realm: North American detrital zircons de-bug the Bug Island limestone? Authors: Beranek, L.P., Murphy, D.C., Orchard, M.J., and Mortensen, J.K. Coauthors Murphy and Orchard contributed comments on an early version of this manuscript. CHAPTER 6 Triassic peripheral foreland basin development and overlap assemblages in the northern North American Cordillera: New insights on the accretion of Yukon-Tanana and related terranes Authors: Beranek, L.P., Mortensen, J.K., and Ullrich, T.  xiv  Chapter 1:  Introduction  1  1.1 INTRODUCTION The North American Cordillera represents a type example of an accretionary orogen, formed in large part by the tectonic addition of terranes against the western margin of Laurentia (Coney et al., 1980). Recognition and study of these terranes has been fundamental to the understanding of Cordilleran geodynamics (Monger and Price, 2002). As a result, hypotheses concerning the initial development of the orogen can be tested directly by examining the suture zone where Cordilleran terranes were emplaced over the North American craton. The core of the eastern Canadian Cordillera in Yukon and northern British Columbia provides an ideal laboratory for such terrane analysis because it encompasses the contact between pericratonic terranes and the ancestral North American margin (Nelson et al., 2006). The current working hypothesis in the northern Cordillera features the Yukon-Tanana (YTT) and Slide Mountain (SMT) terranes accreting to the western edge of North America in Late Permian-Early Triassic time (Mortensen et al., 2007; Colpron and Nelson, in press). No geologic or temporal constraints related to accretion have been developed on the cratonal side of this presumed collisional event; however, bedrock mapping studies have documented that broadly similar Triassic sedimentary rocks form the youngest stratigraphic units on YTT, SMT, and the North American miogeocline in eastern Yukon (Mortensen and Jilson, 1985; Murphy et al., 2006). This observation led to the hypothesis that Triassic rocks were deposited within a collisionrelated basin superposed on the northern Cordilleran margin that subsequently developed into overlap assemblage. An early Mesozoic terrane-craton sedimentary linkage would fundamentally define a Late Permian-Early Triassic accretion event between pericratonic elements and western North America. This investigation evaluated the source and paleotectonic setting for North American Triassic strata in eastern Alaska, Yukon, and northern British Columbia. The primary project goal was to test the hypothesis of a Triassic overlap assemblage recording juxtaposition of YTT and related terranes with North America. Five separate studies were constructed to address the primary project goal and examine the midPaleozoic to early Mesozoic evolution of the northern Cordilleran margin. An overview  2  of the regional geology and motivation for these investigations are outlined in this chapter.  Figure 1.1 – Paleozoic and early Mesozoic terranes of the North American Cordillera. Elements are grouped relative to their paleogeographic or faunal affinity in Paleozoic time. Canadian Cordillera shown in Figure 1.2. Terrane abbreviations: QN – Quesnellia, SM- Slide Mountain, ST – Stikinia, WR – Wrangellia, YT – Yukon-Tanana in the Coast Mountains. Other abbreviations: B.C. – British Columbia, CA – California, NV – Nevada, OR – Oregon, U.S.A. – United States of America. Modified from Colpron and Nelson (in press).  3  1.2 PALEOZOIC DEVELOPMENT OF YUKON-TANANA TERRANE The YTT is one of the largest tectonic elements of the North American Cordillera, underlying western and southern Yukon and portions of easternmost Alaska, and British Columbia (Figure 1.1, YT in Figure 1.2; Mortensen, 1992; Colpron and Nelson, 2006). Dextral transcurrent faulting affected the configuration of YTT (Gabrielse et al., 2006), dissecting it into two main components, an arcuate body on the west and a semicircular outlier on the east. Counterclockwise oroclinal rotation of Stikinia (ST in Figures 1.1, 1.2) and western YTT is the preferred mechanism to explain the arcuate nature of the terrane (see Mihalynuk et al., 1994). Initial bedrock mapping studies on YTT suggested that it was a mélange of highly metamorphosed rocks whose internal stratigraphy was completely obscured by tectonism (Tempelman-Kluit, 1979). Subsequent investigations established YTT as a single entity comprised of variably deformed metamorphic rocks within an internally coherent, discernable stratigraphic framework (e.g., Mortensen and Jilson, 1985; Mortensen, 1992). Most recently, whole-rock geochemical analyses, high-precision U-Pb zircon geochronology, and detailed geologic mapping allowed Colpron and Nelson (2006, and references therein) to define a consistent tectonostratigraphic and magmatic framework for YTT. These assemblages characterize three stages of geodynamic development for the terrane, Late Devonian-Early Mississippian, Early Mississippian-Middle Permian, and Middle Permian to Triassic.  1.2.1 Late Devonian – Early Mississippian Back-arc extension led to the separation of west-facing continental margin and arc fragments from the northwestern Laurentian margin in latest Devonian time, contemporaneous with development of the Antler and Innuitian orogenies in southwestern and northern Laurentia, respectively (Figure 1.3a; Piercey et al., 2004; Nelson et al., 2006). These rifted pericratonic assemblages comprised the foundation for the northern Cordilleran elements YTT, Quesnellia (QN in Figures 1.1, 1.2), and Stikinia. The Eastern Klamath and Northern Sierra terranes, presently exposed in northern California, are interpreted to form the southern portion of this peri-Laurentian ribbon fragment (Colpron et al., 2007). Latest Devonian extension also generated a marginal  4  ocean basin, referred to as the Slide Mountain-Golconda Ocean, in the YTT back-arc region alongside the ancestral North American margin (Figure 1.3a,b). The Snowcap and Finlayson assemblages are the oldest identified units of YTT (Colpon et al., 2006). The pre-Late Devonian Snowcap assemblage represents the lowest structural level of the terrane and consists of metasedimentary and metavolcanic rocks of continental margin affinity (Nelson et al., 2006). The Finlayson assemblage is recognized as a package of continental arc and back-arc rocks that cover and intrude the basement of YTT. Late Devonian to Early Mississippian volcanic and intrusive rocks yield U-Pb zircon ages from ca. 357-390 Ma, comprising the Ecstall and Finlayson magmatic cycles of YTT (Figure 1.4; Mortensen, 1992; Colpron et al., 2006).  Figure 1.2 – Terrane map of the Canadian and Alaskan Cordillera. Modified from Colpron et al. (2007).  5  1.2.2 Early Mississippian – Middle Permian The mid- to late Paleozoic record of YTT consists primarily of metavolcanic and intrusive rocks of the Finlayson and Klinkit assemblages (Colpron et al.. 2006). Finlayson assemblage igneous rocks are recognized to have continental-arc geochemical affinities whereas those of the Klinkit assemblage correlate with an island-arc tectonic setting (Piercey et al., 2006). Volcanic arc activity during this time ranged from ca. 269357 Ma, comprising the Wolverine, Little Salmon, and Klinkit cycles (Figure 1.4). Mississippian to Permian Klinkit assemblage rocks in southern Yukon are interpreted to be correlative with both the Harper Ranch and Lay Range assemblages of Quesnellia in central and southern British Columbia and the Stikine assemblage of Stikinia in northwestern British Columbia (see dark green polygons labeled HR in Figure 1.2; Simard et al., 2003; Gunning et al., 2006). As a consequence, YTT may form the basement to Mesozoic Quesnellia and Stikinia (Mortensen, 1992; Colpron et al., 2006). Late Paleozoic reversal in arc polarity dramatically changed the geodynamic setting of YTT. By the Middle Permian, the west-facing magmatic arc system that existed for ~120 million years ceased by an unknown mechanism and subduction of Slide Mountain-Golconda Ocean lithosphere commenced under the eastern margin of the terrane (Figure 1.3b; Mortensen, 1992; Colpron et al., 2006). Therefore, by this time, the marginal ocean basin between YTT and ancestral North America had reached its greatest expanse. The mid- to late Paleozoic geometry and width of the basin is not clear; however, many terranes related to YTT, such as Quesnellia and Stikinia, have occurrences of Permian McCloud fauna, also observed on the North American craton in Texas (see Figure 1.2b; Miller, 1987; Colpron et al., 2007). This may suggest that the pericratonic terranes did not travel more than a few thousand kilometres from the Laurentian continent (Belasky et al., 2002).  1.2.3 Middle Permian to Triassic West-dipping subduction along the eastern margin of YTT progressively closed the Slide Mountain-Golconda Ocean and accommodated eastward transport of the peri-  6  Figure 1.3 – Paleozoic paleogeographic evolution of northwestern Laurentia and adjacent pericratonic terranes. Gold discs indicate McCloud faunal occurrences. YTT – Yukon-Tanana terrane Modified from Colpron et al. (2007).  Laurentian terranes towards western North America (Figure 1.3c). Calc-alkaline, felsic metavolcanic and metaplutonic rocks of the Middle to latest Permian Klondike assemblage formed by this east-facing arc system and represent the youngest units of YTT (Mortensen, 1990; Colpron et al., 2006). Klondike assemblage rocks yield U-Pb zircon ages from ca. 253-269 Ma (Mortensen, 1992; Colpron et al., 2006). Remnants of the Slide Mountain-Golconda Ocean in the northern Cordillera are referred to as the Slide Mountain assemblage and consist of Late Devonian to Permian deep-water marine stata, mafic igneous rocks of oceanic affinity, and slivers of oceanic lithosphere (Colpron et al., 2006). In western Canada and adjacent Alaska, these rocks comprise the Slide Mountain terrane (SMT; SM in Figures 1.1, 1.2; Harms et al., 1984; Struik and Orchard, 1985). The Slide Mountain assemblage shares lithologic and age characteristics with Havallah sequence rocks of the Golconda allochthon in the southwestern United States (see location in Figures 1.1, 1.3c). The SMT and Golconda allochthon both represent the easternmost terranes in the Cordillera, and are typically 7  Figure 1.4 – Probability density plot for the ages of Yukon-Tanana terrane rocks. Solid black line indicates U-Pb zircon ages; apparent lull during Pennsylvanian-Permian time reflects mafic and intermediate volcanism that did not generate much zircon. Dotted black line corresponds to fossil ages, mainly from conodonts (see Orchard, 2006). Fin – Finlayson, Wolv. – Wolverine. From Colpron et al. (2006).  in thrust-related contact with North American continental margin strata (Nelson, 1993; Dickinson, 2006; Murphy et al., 2006).  1.3 EVIDENCE FOR LATE PERMIAN-EARLY TRIASSIC TECTONISM Accretion of the peri-Laurentian terranes against the western edge of North America is widely interpreted to have commenced in Early to Middle Jurassic time because intense deformation and stitching plutons of that age occur in the southern Canadian Cordillera (e.g., Gabrielse and Yorath, 1991; Murphy et al., 1995). However, field and analytical studies in western Canada have reported compelling evidence for Late Permian-Early Triassic (ca. 250 Ma) collision (e.g., Read and Okulitch, 1977; Mortensen et al., 2007). Latest Paleozoic to earliest Mesozoic collision in western Canada is a viable hypothesis because it most easily explains coeval magmatic cessation, deformation, unconformities, and the composition of Triassic siliciclastic rocks in the Canadian Cordillera. Furthermore, it is analogous to Late Permian-Early Triassic Sonoman orogenesis in the southwestern United States.  8  1.3.1 Late Permian-Early Triassic magmatic cessation U-Pb zircon ages from Klondike assemblage rocks demonstrate that widespread YTT arc magmatism ceased by ca. 253 Ma (Mortensen, 1992). As a direct result, this suggests subduction of Slide Mountain-Golconda Ocean lithosphere under YTT also concluded by ca. 253 Ma. The simplest explanation for magmatic cessation would be full closure of the marginal ocean basin by Late Permian-Early Triassic time, thus requiring proximity between pericratonic terranes and the North American margin (see Figure 1.3c).  1.3.2 Late Permian-Early Triassic deformation and unconformities Late Permian to Middle Triassic deformation has been documented in numerous localities throughout the Cordillera. Sub-Triassic unconformities or depositional hiatuses are typically described at these localities (e.g., Read and Okulitch, 1977). In western Yukon, three suites of YTT and SMT rocks demonstrate latest Paleozoic-earliest Mesozoic deformation. Berman et al. (2007) reported that garnet porphyroblasts in mid-Paleozoic mica schist contain monazite inclusions with U-Pb ages ca. 239 Ma, recording amphibolite facies metamorphism at conditions near 9 kbar and 600°C. Detrital zircons from the mica schist have low Th/U overgrowths that indicate metamorphism ca. 260 ± 3 Ma (Villeneuve et al., 2003). In an adjacent area, crosscutting field relationships allowed Mortensen et al. (2007) to document that Middle to Late Permian Klondike assemblage rocks were ductily deformed twice by ca. 250 Ma. Finally, Htoon (1981) demonstrated that metavolcanic rocks associated with SMT in western Yukon yield whole-rock isotopic ages ca. 260 Ma and inferred that a Permian metamorphic event affected those units. Read and Okulitch (1977) suggested that sub-Triassic angular unconformities on Quesnellia in southern British Columbia indicate Late Permian to Middle Triassic uplift and erosion (their Tahltanian and Sonoman orogenies). Schiarizza (1989) concluded that SMT rocks in southern British Columbia were faulted over the continental margin in Late Permian-Early Triassic time, similar to Havallah sequence units of the Sonoman orogeny in Nevada.  9  Sub-Triassic unconformities are also recognized along the Cordilleran miogeocline in Yukon, British Columbia, and Alberta (Gibson and Barclay, 1989; Gordey and Anderson, 1993; Davies, 1997). However, there is no direct evidence for pre-Triassic deformation in continental margin strata of western Canada. Farther south in the western United States, repeated episodes of late Paleozoic uplift and erosion affected Cordilleran margin rocks preceding the Sonoman orogeny (Trexler et al., 2004).  1.3.3 Triassic sedimentary rocks of the eastern Cordillera in western Canada Despite the compelling nature for Late Permian-Early Triassic tectonism in western Canada, there is a paucity of information regarding the source of Triassic Cordilleran margin strata. Muscovite-bearing siliciclastic rocks sit above a sub-Triassic unconformity on YTT, SMT, and the North American margin in Yukon, and are typically located near major structures along the eastern margins of the terranes. The source of the muscovite is not constrained and mica does not typically occur in the underlying North American Paleozoic stratigraphy. Therefore, the spatial proximity of North American Triassic strata to micaceous metamorphic rocks of YTT is conspicuous and may suggest stratigraphic coherence between the two elements. Northerly derived Triassic strata of Arctic Canada contain ubiquitous ca. 430-700 Ma detrital zircon populations that may have been sourced from the Innuitian orogenic belt (see location on inset map of Figure 1.1; Miller et al., 2006). Limited detrital zircon studies of North American Triassic strata in the southern Canadian Cordillera led Ross et al. (1997) to a similar conclusion. The ultimate source of Innuitian-derived detrital zircon in Cordilleran margin strata is unconstrained and remains as a fundamental problem to address in North American geology. However, Nd isotope signatures in postLate Devonian continental margin strata suggest the Innuitian signal is substantial and that it dramatically influenced the composition of the miogeocline (Garzione et al., 1997). The source of fine-grained Triassic strata of Quesnellia and the North American margin has been addressed in southern British Columbia. Unterschutz et al. (2002) reported that Late Triassic strata of Quesnellia have trace element and Nd isotope signatures indicating mixture of primitive and evolved source material, similar to coeval continental margin strata (see Boghossian et al., 1996). Unterschutz et al. (2002)  10  concluded that these compositions define a Late Triassic depositional tie between Quesnellia and western North America. The early Mesozoic paleogeography of Cordilleran terranes remains a point of contention because geologic, paleontologic, and paleomagnetic datasets are typically not in agreement with each other (Haggart et al., 2006). The affinity of the peri-Laurentian terranes is intriguing because geodynamic models suggest their development alongside western Laurentia (Figure 1.3; Colpron et al., 2007); however, these terranes contain faunal assemblages that are both endemic and exotic with respect to the eastern protoPacific Ocean and North American craton (Monger and Ross, 1971). For example, Late Triassic carbonate overlying the SMT in southeastern Yukon, informally named the Bug Island limestone, yields conodonts that are typical of late early Norian strata along the Tethyan margin in central Europe (Orchard, 2006). This may suggest an exotic origin for the Bug Island limestone (Johnston, 2008).  1.4 PROJECT OUTLINE The investigation of a Triassic overlap assemblage in Yukon was initially conceived by M. Colpron of the Yukon Geological Survey and J.K. Mortensen of the University of British Columbia in November 2004. An outline of project scope and goals was first defined in July 2005 by Colpron, Mortensen, and myself. It was hypothesized that provenance analysis would be the most promising approach to examine the affinity of Triassic rocks because the pericratonic terranes and North American margin have different mid- to late Paleozoic magmatic and deformational histories (see section 1.2). Therefore, the YTT should yield detrital zircon and muscovite populations of unique ages with respect to Cordilleran margin. Five studies, comprising chapters 2-6, were designed and implemented to complete the primary project goal. Unless noted, I was the principal investigator for all field studies. Field work took place during the summers of 2005-2007 and comprised measurement, description, and sampling of previously described mid-Paleozoic to midMesozoic stratigraphic sections in Yukon, northern British Columbia, and eastern Alaska (see Beranek and Mortensen, 2006; 2007; 2008). I conducted all detrital zircon sample preparation and U-Pb data collection by laser-ablation inductively coupled plasma mass  11  spectroscopy (LA-ICP-MS) at the Pacific Centre for Isotopic and Geochemical Research (PCIGR), at the University of British Columbia. I was the main author on all manuscripts comprising chapters 2-6 but comments from coauthors are acknowledged to have improved the text and rationale. The motivation behind each of the five studies, and roles of the coauthors, are listed below.  1.4.1 Establishing a detrital zircon reference frame for the post-Late Devonian Cordilleran miogeocline in northern Canada Previous detrital zircon provenance analysis of post-Late Devonian Cordilleran margin strata in western Canada and adjacent Alaska recognized unique early Paleozoic (ca. 430 Ma) grains that have no obvious Laurentian source (Ross et al., 1997; Gehrels et al., 1999). In these studies, U-Pb ages were measured using thermal-ionization mass spectroscopy (TIMS) methods, which are both time consuming and expensive. As a result, the number of individual zircon grains analyzed per sample was low (i.e., n < 40). Miller et al. (2006) generated a large dataset (i.e., n = 100 per sample) on their study of Triassic strata in the circum-Arctic region by using LA-ICP-MS. These extensive datasets defined a much broader early Paleozoic to late Neoproterozoic signal than previously recognized. These age signatures were also observed in preliminary LAICP-MS detrital zircon studies on North American strata in Yukon (Beranek and Mortensen, 2007). The source of Paleozoic sedimentary rocks along the northern Cordilleran margin must be well-defined to access the source of North American Triassic strata. For this reason, Chapter 2 tested the provenance of Late Devonian to Mississippian siliciclastic strata in northern Yukon and Northwest Territories. Based on paleocurrent indicators, geophysical datasets, and geologic inferences, these strata were previously interpreted to be sourced directly from the Innuitian orogenic belt, the suggested origin of ca. 430 Ma detrital zircons. The products of this study were two-fold: constraining the provenance of non-Laurentian, early Paleozoic detrital zircons in North American continental margin strata and defining a regional framework for future studies on Triassic rocks in the northern Cordillera.  12  Chapter 2 comprises a version of a manuscript to be submitted for publication. L. Lane of the Geological Survey of Canada, T. Allen and T. Fraser of the Yukon Geological Survey, T. Hadlari and W. Zanvoort of the Northwest Territories Geoscience Office, and J.K. Mortensen donated rock samples (Imperial and Tuttle formations) for detrital zircon analysis and will be coauthors on the submitted manuscript. Three samples collected during the course of my dissertation research (Prevost and Tsichu formations) were also analyzed. Comments from T. Hadlari, J.K. Mortensen, and L. Lane on an early manuscript were incorporated into the version of Chapter 2 in this dissertation.  1.4.2 Defining provenance correlations between North American Triassic strata in the eastern Canadian Cordillera A stratigraphic, age, and compositional study of North American Triassic rocks from west-central to southeastern Yukon, comprising Chapter 3, was designed to test correlation between miogeoclinal strata in Yukon with coeval rocks in British Columbia and Alberta. In concert with results from Chapter 2, these data established a continental margin signature in Yukon that can be directly compared to Cordilleran strata derived from pericratonic terranes. Detrital muscovite analyses described in Chapter 3 were conducted by coauthor T. Ullrich at the PCIGR. Whole-rock trace element geochemical samples were analyzed by inductively coupled plasma atomic emission (ICP-AES) and ICP-MS at the ALS Chemex laboratories in North Vancouver, British Columbia. Whole-rock Sm-Nd isotope geochemical analysis by TIMS was carried out by B. Kieffer at the PCIGR. New conodont collections were analyzed by coauthor M.J. Orchard of the Geological Survey of Canada. Chapter 3 has been prepared as a manuscript to be submitted for publication. Comments from coauthors J.K. Mortensen and M.J. Orchard on an early manuscript were included into the version of Chapter 3.  13  1.4.3 Late Permian-Early Triassic closure of the Slide Mountain-Golconda Ocean The hypothesized Late Permian-Early Triassic closure of the Slide MountainGolconda Ocean in northern Canada was tested in Chapter 4. In this study, the provenance of 20 sedimentary rock samples was evaluated to constrain the source of Triassic strata associated with the SMT and their provenance correlation with units discussed in chapters 2 and 3. These data were also used to construct a holistic model for the evolution of the Slide Mountain-Golconda Ocean marginal basin, including comparison between Late Permian-Early Triassic tectonism in northern Canada and the Sonoman orogeny in Nevada. A version of Chapter 4 will be submitted for publication. Detrital muscovite analyses were conducted by coauthor T. Ullrich at the PCIGR. Coauthor J.K. Mortensen provided comments on an early edition of the manuscript.  1.4.4 Paleogeography of the Late Triassic Bug Island limestone The paleogeographic affinity and origin of several Cordilleran terranes is still under debate. The source of sandy material in the Bug Island limestone was evaluated in Chapter 5 to test possible exotic versus peri-Laurenitian affinities for the SMT and Late Triassic conodont fauna that are similiar to Tethyan collections in Europe. U-Pb detrital zircon ages from the Bug Island limestone were correlated to other Cordilleran units using the reference frames built in chapters 2-4. A version of Chapter 5 will be submitted for publication. Discussion with, and comments from, coauthors D.C. Murphy of the Yukon Geological Survey, M.J. Orchard, and J.K. Mortensen improved the rationale and scope of this chapter.  1.4.5 Collision-related Triassic sedimentation in southeastern Yukon The provenance of North American Triassic siliciclastic rocks adjacent to the YTT and SMT in southeastern Yukon were examined in Chapter 6. This chapter tests the hypothesis that these strata filled a collision-related, peripheral foreland basin situated along the North American margin. This chapter also evaluated the source of Jurassic strata in two locations in order to test other Mesozoic sedimentary patterns in Yukon.  14  A modified version of Chapter 6 will be submitted for publication. Whole-rock geochemical data described in Chapter 6 will not be included in the submission. Detrital muscovite dates reported in this chapter were conducted by coauthor T. Ullrich of the PCIGR. Whole-rock trace element geochemical samples were analyzed by ICP-AES and ICP-MS at the ALS Chemex laboratories in North Vancouver, British Columbia. Wholerock Sm-Nd isotope geochemical analysis by TIMS was completed by B. Kieffer at the PCIGR. Coauthor J.K. Mortensen provided comments on an early draft of this manuscript.  15  1.5 REFERENCES Belasky, P., Stevens, C.H., and Hanger, R.A., 2002, Early Permian location of western North American terranes based on brachiopod, fusulinid, and coral biogeography: Palaeoceanography, Palaeoclimatology, Palaeoecology, v. 179, p. 245-266. Beranek, L.P., and Mortensen, 2006, Triassic overlap assemblages in the northern Cordillera: Preliminary results from the type section of the Jones Lake Formation, Yukon and Northwest Territories (NTS 105I/13), in Emond, D.S., Bradshaw, G.D., Lewis, L.L., and Weston, L.H., eds., Yukon Exploration and Geology 2005: Yukon Geological Survey, p. 79-91. Beranek, L.P., and Mortensen, J.K., 2007, Investigating a Triassic overlap assemblage in Yukon: On-going field studies and preliminary detrital zircon age data, in Emond, D.S., Lewis, L.L., and Weston, L.H., eds., Yukon Exploration and Geology 2006: Yukon Geological Survey, p. 83-92. Beranek, L.P., and Mortensen, 2008, New stratigraphic and provenance studies of Triassic sedimentary rocks in Yukon and northern British Columbia, in Emond, D.S., Blackburn, L.R., Hill, R.P., and Weston, L.H., eds., Yukon Exploration and Geology 2007: Yukon Geological Survey, p. 115-124. Berman, R.G., Ryan, J.J., Gordey, S.P., and Villeneuve, M., 2007, Permian to Cretaceous polymetamorphic evolution of the Stewart River region, Yukon-Tanana terrane, Yukon, Canada: P-T evolution linked with in situ SHRIMP monazite geochronology: Journal of Metamorphic Geology, v. 25, p. 803-827. Boghossian, N.D., Patchett, P.J., Ross, G.M., and Gehrels, G.E., 1996, Nd isotopes and the source of sediments in the miogeocline of the Canadian Cordillera: Journal of Geology, v. 104, p. 259-277. Colpron, M., and Nelson, J.L., eds., 2006, Paleozoic evolution and metallogeny of pericratonic terranes at the ancient Pacific margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada Special Paper 45, 523 p. Colpron, M., and Nelson, J.L., in press, The Northwest Passage: Incursion of Baltican and Siberan crustal fragments into eastern Panthalassa, and the mid-Paleozoic to early Mesozoic evolution of the Cordilleran margin of western North America, in Cawood, P., and Kröner, A., eds., Accretionary orogens: Geological Society of London Special Publication. Colpron, M., Nelson, J.L., and Murphy, D.C., 2006, A tectonostratigraphic framework for the pericratonic terranes of the northern Canadian Cordillera, in Colpron M., and Nelson, J.L., eds., Paleozoic evolution and metallogeny of pericratonic terranes at the ancient Pacific margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada Special Paper 45, p. 1-23. Colpron, M., Nelson, J.L., and Murphy, D.C., 2007, Northern Cordilleran terranes and their interactions through time: GSA Today, v. 17, p. 4-10. Coney, P.J., Jones, D.L., and Monger, J.W.H., 1980, Cordilleran suspect terranes: Nature, v. 288, p. 329-333. Davies, G.R., 1997, The Triassic of the Western Canada Sedimentary Basin: tectonic and stratigraphic framework, paleogeography, paleoclimate, and biota: Bulletin of Canadian Petroleum Geology, v. 45, p. 434-460.  16  Dickinson, W.R., 2006, Geotectonic evolution of the Great Basin: Geosphere, v. 2, p. 353-368. Gabrielse, H., and Yorath, C.J., eds., 1991, Geology of the Cordilleran Orogen in Canada: Geological Survey of Canada, The Geology of North America, v. G-2, 844 p. Gabrielse, H., Murphy, D.C., and Mortensen, J.K., 2006, Cretaceous and Cenozoic dextral orogen-parallel displacements, magmatism, and paleogeography, northcentral Canadian Cordillera, in Haggart, J.W., Enkin, R.J., and Monger, J.W.H., eds., Paleogeography of the North American Cordillera: Evidence for and against large-scale displacements: Geological Association of Canada, Special Paper 46, p. 255-276. Garzione, C.N., Patchett, P.J., Ross, G.M., and Nelson, J.L., 1997, Provenance of Paleozoic sedimentary rocks in the Canadian Cordilleran miogeocline: a Nd isotopic study: Canadian Journal of Earth Sciences, v. 34, p. 1603-1618. Gehrels, G.E., Johnsson, M.J., and Howell, D.G., 1999, Detrital zircon geochronology of the Adams Argillite and Nation River Formation, east-central Alaska, U.S.A.: Journal of Sedimentary Research, v. 69, p. 135-144. Gibson, D.W., and Barclay, J.E., 1989, Middle Absaroka Sequence – the Triassic stable craton, in Ricketts, B., ed., Western Canada Sedimentary Basin: Canadian Society of Petroleum Geologists, Special Publication no. 30, p. 219-233. Gordey, S.P., and Anderson, R.G., 1993, Evolution of the northern Cordilleran miogeocline, Nahanni map area (105I), Yukon and Northwest Territories: Geological Survey of Canada Memoir 428, 214 p. Gunning, M.H., Hodder, R.W., and Nelson, J.L., 2006, Contrasting styles and their tectonic implications for the Paleozoic Stikine assemblage, western Stikine terrane, northwestern British Columbia, in Colpron M., and Nelson, J.L., eds., Paleozoic evolution and metallogeny of pericratonic terranes at the ancient Pacific margin of North America, Canadian and Alaskan Cordillera: Geological Association of Canada Special Paper 45, p. 210-227. Haggart, J.W., Enkin, R.J., and Monger, J.W.H., eds., Paleogeography of the North American Cordillera: Evidence for and against large-scale displacements: Geological Association of Canada Special Paper 46, 429 p. Harms, T.A., Coney, P.J., and Jones, D.L., 1984, The Sylvester allochton, Slide Mountain terrane, British Columbia: A correlative of oceanic terranes of northern Alaska: Geological Society of America, Abstracts with Programs, v. 16, p. 288. Htoon, M., (1979), Geology of the Clinton Creek asbestos deposit, Yukon Territory: M.Sc. thesis, University of British Columbia, Vancouver. Johnston, S.J., 2008, The Cordilleran ribbon continent of North America: Annual Review of Earth and Planetary Sciences, v. 36, p. 495-530. Mihalynuk, M.G., Nelson, J., and Diakow, L.J., 1994, Cache Creek terrane entrapment: Oroclinal paradox within the Canadian Cordillera: Tectonics, v. 13, 575-595. Miller, M.M., 1987, Dispersed remnants of a northeast Pacific fringing arc: upper Paleozoic terranes of Permian McCloud faunal affinity, western U.S.: Tectonics, v. 6, p. 807-830. Miller, E.L., Toro, J., Gehrels, G.E., Amato, J.M., Prokopiev, A., Tuchkova, M.I., Akinin, V.V., Dumitru, T.A., Moore, T.E., and Cecile, M.P., 2006, New insights  17  into Arctic paleogeography and tectonics from U-Pb detrital zircon geochronology: Tectonics, v. 25, p. 1-19. Monger, J.W.H., and Ross, C.A., 1971, Distribution of Fusulinaceans in the western Canadian Cordillera: Canadian Journal of Earth Sciences, v. 8, p. 259-278. Monger, J.W.H., and Price, R.A., 2002, The Canadian Cordillera: geology and tectonic evolution: Canadian Society of Exploration Geophysicists Recorder, February, p. 17-36. Mortensen, J.K., 1990, Geology and U-Pb geochronology of the Klondike district, westcentral Yukon: Canadian Journal of Earth Sciences, v. 27, p. 903-914. Mortensen, J.K., 1992, Pre-mid-Mesozoic evolution of the Yukon-Tanana terrane, Yukon and Alaska: Tectonics, v. 11, p. 836-853. Mortensen