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, first- cycle 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 ...................................................................................