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Toarcian (Lower Jurassic) ammonite biostratigraphy and ammonite fauna of North America Jakobs, ,Giselle Kathleen 1992

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TOARCIAN (LOWER JURASSIC) AMMONITE BIOSTRATIGRAPHYAND AMMONITE FAUNA OF NORTH AMERICAbyGISELLE KATHLEEN JAKOBSBACHELOR OF SCIENCE (HONOURS)UNIVERSITY OF BRITISH COLUMBIAA THESIS SUBMITTED IN PARTIAL FULFILMENT OFTHE REQUIREMENTS FOR THE DEGREE OFDOCTOR OF PHILOSOPHYinTHE FACULTY OF GRADUATE STUDIESGEOLOGICAL SCIENCESWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAJUNE 1992© G.K. JAKOBS, 1992Signature(s) removed to protect privacyIn presenting this thesis in partial fulfilment of the requirements for an advanced degreeat The University of British Columbia, I agree that the Library shall make it freelyavailable for reference and study. I furt.her agree that. permission for extensive copying ofthis thesis for scholarly purposes may be granted by the Head of my Department or byhis or her representatives. It is understood that copying or publication of this thesis forfinancial gain shall not be allowed without my written permission.Geological SciencesThe University of British Columbia2075 Wesbrook PlaceVancouver, CanadaV6T 1W5Date: 16 June, 1992Signature(s) removed to protect privacyHAbstractToarcian ammonite collections from British Columbia, Nevada, Oregon, the Yukon, andAlaska form the basis of a detailed taxonomic study. Fifty-seven species are described,allocated to 27 genera, one of which is new ( Yakounia). Nine new species are introduced:Yakouma yakoune’nszs, Y. pacifica, Y. freboidi, Y. s2ivae, Pie ydellia maudenss, P.crassiornata, Phymatoceras hiiiebrandti, Leukadiella ii. sp. A, and Leukadiella n. sp. B.Measured sections from the Queen Charlotte Islands and other key areas in westernNorth America were used to distinguish six successive assemblage zones: Kanense,Levisoni, lonica, Crassicosta, Hillebrandti, and Yakounensis. All six zones, which can berecognized from southern Alaska to Nevada, are defined here for the first time. TheArctic basins (Sverdrup and Brooks-MacKenzie) have a low diversity ammonite faunalsequence similar to that of Siberia and the zonation developed there can be used inArctic North America.The Toarcian of western North America is most commonly represented by argillaceoussediments. On the craton, in t.he Sverdrup basin, a transgression in the Middle Toarciansuggests a link with eustatic sea level changes. On the terranes, two intervals of coarsergrained sedimentation can be recognized, one during the Crassicosta Zone and oneduring the Yakounensis Zone and continuing into the Aalenian. These intervals are alsoprobably related to eustatic sea level changes.A paleobiogeographic study of the similarity of ammonite faunas between different areasused two methods: a Monte Carlo simulation, in which randomly generated data setsprovide confidence levels for similarity coefficients, and complete linkage cluster analysis.The Monte Carlo method corrects for sparseness in the data set., cluster analysis does notand should be used with caution in similar studies.111The ammonite fauna of westeril North America includes taxa with pandemic, Tethyan,Boreal, Pacific, East Pacific, and Athabascan affinities. Several possible migration routesexist that could explain the similarity of western North American faunas to those ofwestern Tethys. An analysis of the similarity of the western North American fauna toother areas, at the generic level. shows that migration of endemic forms occurred via theHispanic Corridor, coinciding with periods of high sea level.ivTable of ContentsVolume 1Abstract.iiTable Of Contents ivList Of Tables ixList Of Figures xAcknowledgements xivChapter 1 Introduction 11.1 Introductory statement 11.2 Purpose 31.3 Previous work 41.4 Methods 6Chapter 2 Regional Geology 82.1 Tectonic Setting 82.2 Sverdrup Basin (A) 102.2.1 Introduction 102.2.2 Stratigraphy Heiberg Group/Formation Jameson Bay Formation Sandy Point Formation 152.3 Brooks-MacKenzie Basin (B) 162.3.1 Introduction 162.3.2 MacKenzie Basin Introduction Stratigraphy 172.3.3 Brooks Basin Introduction Stratigraphy 202.4 Whitehorse Trough (C) 212.4.1 Introduction 212.4.2 Stratigraphy Inklin Takwahoni 232.5 Hazelton Trough (D) 232.5.1 Introduction 232.5.2 Northern area Introduction Iskut and Telegraph Creek areas Spatsizi area Toodoggone 272.5.3 East-central area Introduction Stratigraphy 282.6 Southern Canadian Rocky Mountains (E) 292.6.1 Introduction 292.6.2 Stratigraphy 29V2.7 Quesnellia (F).312.7.1 Introduction 312.8 “Methow Trough” (G) 322.8.1 Introduction 322.8.2 Manning Park 332.8.3 Harrison Lake 332.8.4 Tyaughton Creek area 352.9 East-central Oregon (H) 362.9.1 Introduction 362.9.2 Stratigraphy 362.9.2.1 Nicely Shale 362.9.2.2 Hyde Formation 362.9.2.3 Snowshoe Formation 382.10 Nevada (I) 382.10.1 Introduction 382.11 Peninsular Terrane (J) 392.11.1 Introduction 392.11.2 Stratigraphy 402.12 Wrangellia (K) 402.12.1 Wrangell Mountains 402.12.2 Queen Charlotte Islands 412.12.2.1 Introduction 412.12.2.2 Stratigraphy 41Chapter 3 Biostratigraphy and Paleontology 533.1 Introduction.533.2 Arctic North America Biostratigraphy.553.3 North American Biostratigraphy 593.3.1 Ammonite Zonation.593.3.1.1 Kanense Zone.593.3.1.2 Levisoni Zone 613.3.1.3 Ionica Zone 623.3.1.4 Crassicosta Zone 633.3.1.5 Hillehrandti Zone 643.3.1.6 Yakounensis Zone 653.3.2 Biograph 673.3.2.1 Method 673.4 Biostratigraphy of the measured sections 723.4.1 Tulsequah (C-4A) 723.42 Spatsizi Area (D-4) 723.4.2.1 Section Y of Smith et al., 1984 (D-4-C) 723.4.2.2 Joan Lake Section (D-4-M) 763.4.3 McConnell Creek (D-6-A) 763.4.4 Queen Charlotte Islands (K-2) 793.4.4.1 Central Graham Island (K-2-A) 793.4.4.2 Central Graham Island (K-2-B) 793.4.4.3 Central Graham Island (K-2-C) 823.4.4.4 Central Graham Island (K-2-D) 823.4.4.5 Central Graham Island (K-2-E 823.4.4.6 Central Graham (K-2-H, K-2-I 863.4.4.7 Central Graham Island (K-2-J, K-2-K) 863.4.4.8 Whiteaves Bay (K-2-N) 91viChapter 4 Regional Correlations and Analysis 934.1 Sverdrup Basin (A) 934.1.1 Prince Patrick Island 934.1.2 Melville Island 954.1.3 MacKenzie King Island 964.1.4 Borden Island 964.1.5 Ellef Ringnes Island 964.1.6 Cornwall Island 974.1.7 Axel Heiberg Island 974.1.8 Ellesmere Island 984.1.9 Basin analysis 994.2 Brooks-MacKenzie Basin (B) 1004.2.1 MacKenzie Basin 1004.2.2 Brooks Basin 1014.3 Whitehorse Trough (C) 1024.4 Hazelton Trough (D) 1034.4.1 Northern area 1034.4.1.1 Iskut and Telegraph Creek areas 1034.4.1.2 Spatsizi area 1034.4.2 East-central area 1044.4.2.1 McConnell Creek area 1044.4.2.2 Hazelton area 1044.4.2.3 Smithers, Nechako, and Whitesail areas 1044.4.3 Southern area 10.54.5 Southern Canadian Rocky Mountains (E) 1054.5.1 Northern area 1054.5.2 Southern area 1054.6 Quesnellia (F) 1064.7 ‘Methow TroughM (G) 1064.7.1 Manning Park 1064.7.2 Harrison Lake 1074.7.3 Tyaughton Creek area 1074.8 East-central Oregon (H) 1074.9 Peninsular Terrane (J) 1094.10 Regional Events 1094.10.1 North American evidence 1114.10.1.1 Craton 1114.10.1.2 Terranes 1144.10.2 Conclusions 117Chapter 5 P aleobiogeography 118.5.1 Introduction 118.5.2 Problems and Considerations 121.5.3 Methods and Analysis 1265.3.1 Binary Coefficients 1265.3.2 Monte Carlo Simulation 1325.3.2.1 Introduction 1325.3.2.2 Sub-stage Results 1395.3.2.3 Stage Results 1835.3.3 Cluster Analysis Introduction 1855.3.3.2 Sub-stage Results 1885.3.3.3 Stage Results 1915.4 Conclusions 193vii.5.5Sources. 197Chapter 6 Systematic Paleontology 2166.1 Introduction 2166.2 Systematic Descriptions 220Family Phylloceratidae 220Subfamily Phylloceratinae 220Genus Phylloceras 220Subfamily Calliphylloceratinae 222Genus Holcophylloceras 222Family Lytoceratidae 224Subfamily Lytoceratinae 224Genus Lytoceras 224Family Dactlyioceratidae 227Genus Dactylioceras 227Genus Peronoceras 235Genus Collina 246Genus Catacoeloceras 249Family Flildoceratidae 251Subfamily Harpoceratinae 251Genus Harpoceras 251Genus Taffertia 256Genus Pseudolioc eras 258Genus Polyplectus 261Subfamily Hildoceratinae 263Genus Hildaites 263Genus Mercaticeras 266Subfamily Grammoceratinae 269Genus Grammoceras 269Genus Podagrosites 271Genus Pieydeilia 276Genus Dumorteria 290Subfamily Bouleiceratinae 296Genus Leukadielia 296Genus Paronic eras 304Family Phymatoceratidae 307Subfamily Phymatoceratinae 307Genus Phymatoc eras 307Genus Rarenodia 318Genus Pseudomercaticeras 321Genus Brodieia 324Genus Denckmannia 327Genus Yakounia 330Subfamily Hammatoceratinae 346Genus Hammatoceras 346Genus Sphaerocoeioceras 350Chapter 7 Conclusions 353References 355viiiVolume 2Appendix A Biograph 382Appendix B Fossil Localities 396Appendix C Paleobiogeography (St.age) .5.51Appendix D Paleobiogeography (Substage) .571Appendix E Programs 621Plates 637List of TablesixTable 5-1Table 5-2Table 5-3Table 5-4Table 5-5Table 5-6Table 5-7Table 5-8Table 5-9Table 5-10Table 5-11Table 5-12Table 5-13Table 5-14Table 5-15Table 5-16Table 5-17Table 5-18Table 5-19Table 5-20Dice coefficients for the entire Toarcian 200Simple Matching coefficients for the entire Toarcian 201Coefficients for the entire Toarcian 202Dice coefficients for the Early Toarcian 203Simple Matching coefficients for the Early Toarcian 204Coefficients for the Early Toarcian 205Dice coefficients for the Middle Toarcian 206Simple Matching coefficients for the Middle Toarcian 207Coefficients for the Middle Toarcian 208Dice coefficients for the Late Toarcian 209Simple Matching coefficients for the Late Toarcian 210Coefficients for the Late Toarcian 211Agglomeration schedule for the entire Toarcian 212Agglomeration schedule for the Early Toarcian 212Agglomeration schedule for the Middle Toarcian 213Agglomeration schedule for the Late Toarcian 213Cluster membership of cases, using complete linkage for the entireToarcian 214Cluster membership of cases, using complete linkage for the EarlyToarcian 214Cluster membership of cases, using complete linkage for the MiddleToarcian 215Cluster membership of cases, using complete linkage for the LateToarcian 215xList of FiguresFigure 1-1Figure 2-1Figure 2-2Figure 2-3Figure 2-4Figure 2-5Figure 2-6Figure 2-7Figure 2-8Figure 2-9Figure 2-10Figure 2-11Figure 2-12Figure 3-1Figure 3-2Figure 3-3Figure 3-4Figure 3-5Figure 3-6Figure 3-7Figure 3-8Figure 3-9Figure 3-10Figure 3-11Figure 3-12Figure 3-13Figure 3-14Figure 3-15Figure 3-16Figure 3-17Figure 3-18Depositional basins of western North America in which Toarcian strataoccur 2Tectonic terrane map of the Canadian Cordillera 9Subdivision of the 11 basins of North America into separate geographicareas 11Location map of the areas in the Sverdrup Basin 12Location map of Toarcian localities from Alaska 19Location map of the Toarcian localities from the Canadian Cordillera 22Location map for Toarcian localities from Oregon and Nevada 37Lower Jurassic formations of the Queen Charlotte Islands 42Location map of Toarcian occurrences in the Queen Charlotte Islands 43Location map of Toarcian localities from Central Graham Island, QueenCharlotte Islands 44Location map of Toarcian localities from the Skidegate Inlet area, QueenCharlotte Islands 45Location map of the “Skedans Rock” (K-2-O) locality from the QueenCharlotte Islands 46Widening of the Phantom Creek intraformational hiatus from north tosouth in the Queen Charlotte Islands 51Correlation of the North American zonation with other zonal schemes 56Zonation and relative stratigraphic ranges of Toarcian ammonites of westernNorth America 58Sorted unitary associations produced using Biograph 71Lithologic symbols used in figures 3-5 to 3-18 73Stratigraphic section C-4-A from the “Bug Mountain anticline”, southwest ofKing Salmon Lake, Tulsequah area, northwestern British Columbia 74Stratigraphic section D-4-C from southwest of Nation Peak, Spatsizi area,northwestern British Columbia 75Stratigraphic section D-4-M from near Joan Lake, Spatsizi area,northwestern British Columbia 77Stratigraphic section D-6-A from the McConnell Creek area, northwesternBritish Columbia 78Stratigraphic section K-2-A from the Yakoun River, Central Graham Island,Queen Charlotte Islands 80Stratigraphic section K-2-B from the Yakoun River, Central Graham Island,Queen Charlotte Islands 81Stratigraphic section K-2-C from the Yakoun River, Central Graham Island,Queen Charlotte Islands 83Stratigraphic section K-2-D from the Yakoun River, Central GrahamIsland, Queen Charlotte Islands 84Stratigraphic section K-2-E from the Yakoun River, Central Graham Island,Queen Charlotte Islands 85Stratigraphic section K-2-H from Creek 57, Central Graham Island, QueenCharlotte Islands 87Stratigraphic section K-2-I from Creek 57, Central Graham Island, QueenCharlotte Islands 88Stratigraphic section K-2-J from Road 59, Central Graham Island, QueenCharlotte Islands 89Stratigraphic section K-2-K from Road 59, Central Graham Island, QueenCharlotte Islands 90Stratigraphic section K-2-N from Whiteaves Bay, northern Moresby Island,Queen Charlotte Islands 92xiToarcian zonal occurrences in the nine basins of western North America 94Lithologic symbols used in Figures 4-3 and 4-4 112Lithologies of the Toarcian sections on the North American craton 113Lithologies of the Toarcian sections on the terranes 115Location map of the possible Toarcian migration routes 119Location map of the eighteen areas used in the paleobiogeographicanalysis 125Idealized binomial distributions and distributions of Dice and SimpleMatching coefficients for different levels of sparsity 128Distribution of average coefficient. values vs. matrix sparseness for the Dicecoefficient.. Coefficient value is based on an average of 1000 coefficientsimulations 129Distribution of average coefficient values vs. matrix sparseness for the SimpleMatching coefficient. Coefficient value is based on an average of 1000coefficient simulations 129Average Dice coefficient vs. matrix sparseness. The observed mean values fallclose t.o the expected mean values 133Average Dice coefficient vs. matrix sparseness. The 90 i’o confidence levelsshow some variation due to differences in the observed mean from theexpected mean 134Average Dice coefficient vs. matrix sparseness. A regression line drawnthrough the 90 7o confidence levels illustrates the degree of variation 135Average Dice coefficient vs. matrix sparseness. Regression lines are drawnthrough the 90, 95, and 99 confidence levels 136Average Simple Matching coefficient vs. matrix sparseness. The amount ofvariation in the observed mean affects the 90, 95 and 99 % confidencelevels 137Average Simple Matching coefficient vs. matrix sparseness. Best-of-fit linesare drawn through the 90, 95. and 99 % confidence levels 138Changes in eustatic sea level during the Early Jurassic 140Generic similarity of North America to other areas during the EarlyToarcian 141Generic similarity of South America to other areas during the EarlyToarcian 142Generic similarity of Japan to other areas during the Early Toarcian 143Generic similarity of the Caucasus to other areas during the EarlyToarciall 144Generic similarit.y of Arabia and Iran to other areas during the EarlyToarcian 145Generic similarity of Pakistan and Madagascar to other areas during theEarly Toarcian 146Generic similarity of Indochina and the southwest Pacific to other areasduring the Early Toarcian 147Generic similarity of the North American Arctic to other areas during theEarly Toarcian 148Generic endemism for 18 areas 150Generic endemism for 8 areas 151Generic similarity of North America to other areas during the MiddleToarcian 153Generic similarity of South America to other areas during the MiddleToarcian 15.5Generic similarity of Japan to other areas during the Middle Toarcian.... 156Generic similarity of the Caucasus to other areas during the MiddleToarcian 157Figure 4-1Figure 4-2Figure 4-3Figure 4-4Figure 5-1Figure .5-2Figure .5-3Figure 5-4Figure 5-5Figure 5-6Figure .5-7Figure .5-8Figure 5-9Figure 5-10Figure 5-11Figure 5-12Figure .5-13Figure 5-14Figure 5-15Figure 5-16Figure 5-17Figure 5-18Figure .5-19Figure 5-20Figure 5-21Figure 5-22Figure .5-23Figure 5-24Figure .5-2.5Figure 5-26xiiGeneric similarity of Arabia and Iran to other areas during the MiddleToarcian 158Generic similarity of Pakistan and Madagascar to other areas during theMiddle Toarcian 159Generic similarity of Indochina and the southwest Pacific to other areasduring the Middle Toarcian 160Generic similarity of the North American Arctic to other areas during theMiddle Toarcian 161Generic similarity of North America to other areas during the LateToarcian 163Generic similarity of South America to other areas during the LateToarcian 164Generic similarity of Japan to other areas during the Late Toarcian 165Generic similarity of the Caucasus to other areas during the LateToarcian 166Generic similarity of Arabia and Iran to other areas during the LateToarcian 167Generic similarity of Indochina and the southwest Pacific to other areasduring the Late Toarcian 168Generic similarity of the North American Arctic to other areas during theLate Toarcian 169Dice confidence levels during the Early Toarcian for eight regions 172Dice confidence levels during the Middle Toarcian for eight regions 173Dice confidence levels during the Late Toarcian for eight regions 174Generic similarity of North America to other areas during the entireToarcian 175Generic similarity of South America to other areas during the entireToarcian 176Generic similarity of Japan to other areas during the entire Toarcian 177Generic similarity of the Caucasus to other areas during the entireToarcian 178Generic similarity of Arabia and Iran to other areas during the entireToarcian 179Generic similarity of Pakistan and Madagascar to other areas during theentire Toarcian 180Generic similarity of Indochina and the southwest Pacific to other areasduring the entire Toarcian 181Generic similarity of the North American Arctic to other areas during theentire Toarcian 182Dice confidence levels during the Entire Toarcian for eight regions 184Complete linkage cluster analysis for the Early Toarcian using 18 areas... 187Complete linkage cluster analysis for the Middle Toarcian using 18 areas 189Complete linkage cluster analysis for the Late Toarcian using 17 areas.... 190Complete linkage cluster analysis for the entire Toarcian using 18 areas.. 192Generic similarity ( > 90 confidence) of North America to other areas forthe Early, Middle and Late Toarcian 194Generic similarity ( > 90 % confidence) of South America to other areas forthe Early, Middle and Late Toarcian 195Relative percentage of each subfamily present in the Kanense, Levisoni, andlonica zones from the Queen Charlotte Islands 218Relative percentage of each subfamily present in the Crassicosta,Hiliebrandti, and Yakounensis zones from the Queen Charlotte Islands... 219Plot of WH vs. TJD for Podagrosites latescens from the Queen CharlotteIslands and France 274Figure 5-27Figure 5-28Figure 5-29Figure 5-30Figure 5-31Figure 5-32Figure 5-33Figure 5-34Figure 5-35Figure 5-36Figure 5-37FigureFigureFigureFigure5-385-395-405-41Figure 5-42Figure 5-43Figure 5-44Figure 5-45Figure 5-46Figure 5-47Figure 5-48Figure 5-49Figure 5-50Figure 5-51Figure 5-52Figure 5-53Figure 5-54Figure 5-55Figure 6-1Figure 6-2Figure 6-3xiiiFigure 6-4 Regression plot of WH vs. UD for Podagrosites latescens from the QueenCharlotte Islands and France 274Figure 6-5 P1st of WE vs. UD for Pie ydetha maudensis from the Queen CharlotteIslands 280Figure 6-6 Plot of WH vs. UD for Pieydellia crasswrnata from the Queen CharlotteIslands 280Figure 6-7 Plot of WH vs. UD for Pie ydellia aalenszs from the Queen CharlotteIslands 28].Figure 6-8 Regression plot of WH vs. UD for Pie ydeilia maudensis, P. crassiornata, andP. aaienszs from the Queen Charlotte Islands 281Figure 6-9 Suture lines for Pleydellia maudensis n. sp. and Pieydeilia crassiornata fromthe Queen Charlotte Islands 282Figure 6-10 Suture lines of Dumortieria, Dumortieria?, and Atacamiceras 294Figure 6-11 Suture lines of Phymatoceras and Yakounia 334Figure 6-12 Plot of WE vs. UD for Yakounia yakounensis from the Queen CharlotteIslands 335Figure 6-13 Plot of WH vs. UD for Yakounia freboidi from the Queen CharlotteIslands 335Figure 6-14 Plot of WH vs. UD for Yakounia pacifica from the Queen CharlotteIslands 336Figure 6-15 Plot of WH vs. LTD for Yakounia siivae from the Queen CharlotteIslands 336Figure 6-16 Regression plot of WH vs. UD for Yakounza yakounensis, Y. freboidi, Y.pacafica, and Y. siivae from the Queen Charlotte Islands 337Figure 6-17 Regression plot of WH vs. UD for Phymatoceras hiiiebrandti from theQueen Charlotte Islands 337xivACKNOWLEDGEMENTThis study was conducted under the guidance and supervision of Dr. Paul L. Smith. Hissupport, both logistical and financial, is greatly appreciated. In addition, his seeminglyinexhaustible supply of patience and good humour made this study much less onerous.Dr. H.W. Tipper (Geological Survey of Canada), in addition to supporting me in thefield, made available the voluminous Toarcian collections of the G.S.C. His extensiveknowledge of the Jurassic of the Canadian Cordillera has been an invaluable resource.His humour and good sense. both in the office and in the field, is greatly appreciated.The other members of my committee, M.J. Orchard (G.S.C.), G.E. Rouse (U.B.C.), andW.C. Barnes (U.B.C.) read drafts of the manuscript and their suggestions improved thefinal product.The Geological Survey of Canada (Cordilleran Division) supported me through foursummers in the field, as part of the Frontier Geoscience Program. Special thanks go toDr. R.I. Thompson (G.S.C.) and Dr. J.W. Haggart (G.S.C) for logisitical field support.L. Maddison and S. Dennison provided able assistance in the field.Financial support was also provided by a Graduate Fellowship from NSERC and aUniversity Graduate Fellowship from the University of British Columbia.Dr. M.K. Howarth (British Museum, Natural History, London) kindly allowed me toview the Toarcian collections stored there and provided helpful taxonomic comments.Dr. A. von Hillebrandt (Technische Universitkt Berlin) made his South Americancollections available for study and I benefited greatly from our discussions. Dr. Schairer(Baverischen Staatssarnmlung für Palontologie und historische Geologic, Milnchen)kindly showed me the South American material stored there.Beth Carter (Portland) provided radiolarian age dates which helped solve a number ofstratigraphic tangles. Her support in the field and via E-mail is greatly appreciated.Jdzsef P1fy, a former graduate student at UBC, provided much useful advice and Ibenefited greatly from our discussions. I am grateful to him for breaking new ground, bybeing the first in our research group to purchase a personal computer. It has made theproduction of this thesis much less stressful. Genga Nadaraju provided many helpfulcontinents as the thesis neared completion and assisted in the assembly of the numerouscopies. Joanna Beyers, a term employee at the G.S.C., was an invaluable resource for allmanner of taxonomic problems, style questions and the like, that were too basic totrouble my advisor with.Susan Ng (UBC Computing Centre) produced the cluster analysis results for thepaleobiogeography and assisted in their interpretation.Kate Gordanier-Smith photographed the ammonites and I wish to express my thanks forthe excellent job she did.Family and friends provided welcome moral support and especial thanks must go to afew people. To my parents. for saying “You can do it.”. To my sister Pamela. forassistance with thesis assembly. To Jim, for long-distance friendship.INTRODUCTIONChapter 1 Introduction1.1 Introductory statementToarcian (Lower Jurassic) sediments occur along western North America, from theCanadian Arctic islands in the north to Nevada in the south (Figure 1-1). Thetectonically complex nature of western North America, with its accreted allochthonousterranes, has demonstrated the need for accurate dating of sediments using fossils.Ammonites, with a long history of study in Europe, are the most useful index fossils forthe Jurassic. Their nektic mode of life led to their wide geographic dispersal and theirrapid evolutionary changes allow precise chronologic resolution. Previous attempts to usethe standard northwest European zonation in the Lower Jurassic of North America havefailed due to:1. the absence of key European index species and genera in North America2. the presence in North America of species and genera absent in Europe3. the overall affinity of North American faunas to the Tethyan region ratherthan northwest EuropeA regional North American ammonite zonation for the Early Jurassic is of primeimportance in the age determination of sedimentary rocks and in the relative timing oflocal, regional, and global events. Towards that end, work has been progressing onproducing ammonite zonations for the Lower Jurassic. The Pliensbachian was recentlycompleted (Smith et al., 1988), and the Hettangian and Sinemurian are also beingstudied.Of the many areas in which Toarcian sediments outcrop, the Queen Charlotte Islandshave proven to contain the most complete stratigraphic sequence, with diverse and wellpreserved ammonites. The ammonite zonation is therefore based to a large extent on theINTRODLC I NFigure 1-1-Depositional basins of western North America in which Toarcian strataoccur.2INTRODUCTION 3Queen Charlotte Islands material. In addition, the presence in the Queen CharlotteIslands of Tethyan genera, previously not known from North America, has raised thequestion of possible migration paths for these forms.1.2 PurposeThis study is a contribution to the Frontier Geoscience Program, a multidisciplinarybasin analysis project to assess the hydrocarbon potential of the Queen Charlotte Basin.The stratigraphically complete Toarcian sequence in the Queen Charlotte Islands andthe diverse and well preserved ammonite fauna have been known for several decades butlittle work has been done. The primary aims of this thesis are:1. To provide a complete and detailed taxonomic analysis of the Toarcianammonite fauna of North America2. To use measured sections from the Queen Charlotte Islands. and other areas,to delimit the stratigraphic ranges of the taxa involved3. To establish a regional ammonite zonation for the Toarcian of North America4. To use the zonal scheme in assessing the presence and extent of the “Toarcianblack shale event” and other regional events in North America.5. To analyze the paleobiogeographic affinities of the North American ammonitefauna with other areas, particularly western Tethys6. To assess the feasibility of different migration routes between North Americaand western Tethys and assess their effect on the distribution of endemic formsINTRODUCTION 41.3 Previous workPrevious studies of Toarcian ammonite distributions within limited parts of NorthAmerica have been done by several workers, but no comprehensive taxonomic orstratigraphic synthesis has been made.Frebold (1957, 1958b, 1960, 1975) reported on ammonite occurrences from the CanadianArctic Islands and figured such genera as Dactylioceras, Harpoceras, Peromoc eras, andPseudolioc eras. No measured section was available, although superpositionalrelationships were documented.Frebold (1958, 1960, 1975; Frebold, Mountjoy, and Tempelman-Kluit, 1967) alsoreported on scattered fossil occurrences from the northern Yukon. These were recentlyrevised and updated by Poulton (1991) and include such genera as Tiltomiceras,Dactylioc eras, Harpoc eras, Hildaites, Peronoc eras, and Pseudolioc eras.Imlay (1955, 1981) reported on Toarcian occurrences from northern Alaska, from theDelong Mountains in the west to the Brooks Range in the east. The South Barrow TestWell 3 provided a measured section, but other occurrences in northern Alaska are fromscattered outcrops. The forms collected from northern Alaska are the same as thosefound in the northern Yukon and in the Canadian Arctic.Imlay (1981) figured ammonites from several localities in southern Alaska, from theAlaska Peninsula and the Talkeetna Mountains. He considered the fauna to be MiddleToarcian in age, but the current study has determined that it is actually Late Toarcian.Frebold (1964) documented scattered Toarcian localities from the southern Yukon andnorthern British Columbia. The fauna contains species of Dactylioceras, Harpoceras,Peronoceras, Pseudolioceras, and Gatulloceras (= Durriortieria).INTRODUCTIONNorth-central and central British Columbia has yielded numerous Toarcian ammonites,but these occurrences have never been published. Frebold identified many of the formsand reported on them in G.S.C. internal fossil reports. These may have beensubsequently quoted by geologic mappers working in the relevant map areas.Thomson, Smith, and Tipper (1986) reported on Early Jurassic ammonite occurrencesfrom the Spatsizi area and mentioned several forms ranging from the Early to MiddleToarcian.Frebold. Tipper. and Coates (1967) reported on Late Toarcian ammonites from theManning Park area, collected from scattered outcrops.Arthur (1987, Arthur et al., 1991; Arthur et al.. in press) illustrated a sparse Toarcianfauna from the Harrison Lake area, including Dactylioceras, Harpoceras, Phymatoceras?(= Hildaites), and Durnortieria.Frebold (1959, 1976) illustrated ammonites from the e1son/Salmo area of southeasternBritish Columbia. This sparse fauna consists almost entirely of Dactylioceras andHarpoc eras.Frebold (1957, 1969, 1976; Frebold and Little, 1962) documented the occurrence ofToarcian ammonites at a number of scattered localities of the Fernie Formation. fromsouthwestern Alberta north to the Jasper area. Hall (1984, 1987) updat.ed theseidentifications and published a stratigraphic section showing three faunal intervals.Imlay (1968) reported on Toarcian occurrences from the Izee-Suplee area of east-centralOregon. These were later updated by Smith (1976) who also provided measured sections.The fauna is Late Toarcian in age and of low diversity. It includes Hammatoceras,Dumortieria, and Pledellia.INTRODUCTION 6Corvaln (1962) described a measured section from the Clan Alpine Mountains of centralNevada which included Toarcian strata. Smith (1981) conducted a detailed study ofSinemurian and Pliensbachian ammonites and also mentioned the presence of EarlyToarcian Tiltoniceras and dactylioceratids.The first Toarcian ammonite occurrences from the Queen Charlotte Islands weredocumented by Whiteaves (1884) and IVlcLearn (1927, 1929, 1930, 1932, 1949).Sutherland Brown (1965) produced a geologic map for the Queen Charlotte Islands andcollected several Toarcian forms which were identified by Frebold. Cameron and Tipper(1985) conducted the most recent study of the Jurassic strata of the Queen CharlotteIslands, and record the occurrence of Early to Late Toarcian forms.1.4 MethodsExtensive fossil collections made in the Queen Charlotte Islands during the summers of1987, 1988, 1989, and 1990 form the basis of the present study. Preexisting collectionsfrom the Queen Charlotte Islands, made by officers of the Geological Survey of Canada,provided a great deal of supplementary material. Sections were measured using theBrunton compass and tape technique and the true stratigraphic thickness was calculatedusing the Fortran program STRAT (Smith, 1976).Material from other areas in the Canadian Cordillera, collected by officers of theGeological Survey of Canada, was also available for study. In some cases stratigraphicsections had been measured and these supplemented the ones obtained from the QueenCharlotte Islands. Material from Oregon (Smith. 1976) and Nevada (Smith, 1981) wasavailable at the University of British Columbia. During the summer of 1989, a trip wasmade to the Clan Alpine Mountains in Nevada to collect additional material. In the fallof 1990, the Bighorn Creek area in the Canadian Rocky Mountains was visited toexamine ammonites in the Fernie Formation.INTRODUCTIONThe quantitative and qualitative taxonomic descriptions conform with the AMMONdatabase developed at the Universtiy of British Columbia (Smith, 1986).The computer program Biograph, developed by Savary and Guex (1990) was used toproduce an ammonite zonation, which was then compared with the one obtainedmanually.In studying the paleogeographic distribution of Toarcian genera, a DBASEIV computerprogram was written to calculate confidence levels for randomly generated binarysimilarity coefficients. A second DBASEIV program was written to produce thesimilarity coefficients between geographic areas at a global scale. The similaritycoefficients produced were later analyzed by cluster analysis using SPSS (StatisticalPackage for the Social Sciences).REGIONAL GEOLOGYChapter 2 Regional Geology2.1 Tectonic SettingThe west coast of North America is a tectonically complex area. due to the convergenceof the Pacific and North American plates. Evidence for the relatively eastwardsubduction of the Pacific ocean floor beneath the North American Plate goes back at.least to the Late Triassic (225 Ma) (Monger. 1991). The Canadian Cordillera is made upof several terranes (Figure 2-1): regions, usually fault bounded. with geological historiesdistinct from that. of adjacent terranes. The terranes are usually referred to as ‘suspect”.indicat.ing their uncertain paleogeographic affinity. Some terranes (e.g. Cache Creek)possess “exotic” faunas which appear to have been deposited in lower latitudes.Paleomagnetic evidence from Triassic basement rocks of many of the terranes alsoprovides evidence of significant latitudinal displacement (Irving, et al.. 198.5). Over time,the separate terranes amalgamated and accreted to the stable craton of western NorthAmerica. This amalgamation involved both accretion and transcurrent faulting. Toarcianstrata are found on several terranes in western North America, including the Peninsular(southern Alaska), Stikinia, Quesnellia, Wrangellia, and several small fragments in the“Methow Trough” area. Of these, Stikinia and Wrangellia contain the most stratigraphicand faunal information.The fragmented nature of western North America makes it difficult to compare Toarcianlithologies across terrane boundaries. Eleven Toarcian basins or depositional troughs canbe discerned (Figure 1-1), many of which are within terranes. Stikinia, for example,contains the Whitehorse and Hazelton troughs. The Sverdrup Basin was a depositionalcentre along the north coast of North America in Early Jurassic time. The BrooksMackenzie Basin received sediment from the North American craton to the southeast.The Whitehorse Trough occupies the northern part of Stikinia, separated from theREGIONAL GEOLOGYFigure 2-1 - Tectonic terrane map of the Canadian Cordillera (from Armstrong et al.,1989).9REGIONAL GEOLOGY 10Hazelton Trough by the Stikine Arch. The Hazelton Trough occupies much of Stikinia,although the southern part is not well documented. The Southern Canadian RockyMountains area, previously known as the Fernie Basin, lay to the west of the NorthAmerican Craton. The Quesnellia Basin extends through much of Quesnellia. The“Methow Trough’ comprises several discrete terrane fragments of questionable originand affinities; including the Manning Park area, the Harrison Lake area, and theTyaughton Creek area of southern British Columbia. The localities in Oregon occur inthe John Day Terrane, an isolated inlier in Tertiary volcanics. The locality in Nevadawas deposited on the North American craton. The Peninsular Terrane of southernAlaska includes strata from Puale Bay and from the Talkeetna Mountains. In Wrangelliathere are minor exposures in southern Alaska as well as the Toarcian basin of the QueenCharlotte Islands, the finest sequence in North America. Toarcian sedimentary rocks arenot known from Vancouver Island.A four-part locality code is used to refer to the different basins, areas, sections, andcollections (see Appendix B). The basins are subdivided into separate geographic areasas listed in Figure 2-2.2.2 Sverdrup Basin (A)2.2.1 IntroductionGeological studies in the Sverdrup Basin have been carried out by a number of scientists(Tozer, 1956; Souther, 1963; Greiner, 1963; Tozer, 1963a, 1963b, 1963c; Tozer andThorsteinsson, 1964; Stott, 1969; Nassichuk and Christie, 1969; Balkwill, 1983; Embry,1983a, 1983b, 1984). Frebold (1957b, 1958b, 1960, 1964, 1967, 197.5) published a series ofpapers on Jurassic fossils from the Canadian Arctic. The last 10-1.5 years has seen a vastexpansion in our knowledge of the basin, due in a large part, to subsurface stratigraphicinformation obtained from oil exploration in the region. Embry (1983a, 1983b, 1984)CD00 CD Cl)0 0 CD U) U) 0 z 0 CD fl 0 ci) CD p 1 p CD 00 CD 0 do p nC) 0 z C) LIj 0 0 C)rea12345678910A-SverdrupPrinceMelvilleMacK&jeBordenEllefCornwallCameronEllesmerePatrickKingRingnesHeibergNorthernBritishBonnetRichards.B-Brooks-Mack.AlaskaMtns.LakeMtns.SouthernC-WhitehorseAtlinBennettTulsequahCryLakeYukonD-HazeltonStewartlskutTelegraphSpatsiziToodogMcconnellHazeltonSmithersWhitesailNechakoCreekgoneCreekE-FernieNorthernSouthernFt.St.F-QuesnelliaQuesnelSalmoJamesG-MethowTyaughtonHarrisonManningCreekLakeParkH-OregonIzee-SupleeI-NevadaWestgateJ-PeninsularPualeTalkeetnaBayMtns.K-WrangelliaWrangellQ.C.I.Mtns.I.I.CD a C-) a 0 CD CD p U) CD CJD CD M p U)C) 0 C) 0 0 C)REGIONAL GEOLOGY 13redefined the Triassic and Jurassic stratigraphy of the region by abolishing someformations, raising others to group status and creating new formations and members.The Sverdrup Basin is a longitudinal, northeast-southwest trending basin which, for theUpper Triassic and Lower Jurassic strata, can be divided into two sub-basins separatedby Ellef Rirignes Island (Figure 2-3’). The western basin includes western Ellef RingnesIsland, King Christian, Borden. Brock, MacKenzie King, Lougheed, Melville and PrincePatrick islands and can be subdivided into finer stratigraphic units than the east-centralbasin. The east central basin includes eastern Ellef Ringnes Island, Amund Ringnes,Cornwall, Graham, Axel Heiberg and western and northern Ellesmere islands (Figure 2-3). The Upper Triassic and Lower Jurassic sequence in the Sverdrup Basin encompassestwo broad stratigraphic packages: the Heiberg Group/Formation and the Wilkie PointGroup.2.2.2 StratigraphyThe following stratigraphic synopsis is based primarily on work of Embry (1983a, 1983b,1984). Heib erg Group/FormationThe Heiberg Group is a Middle Norian to Upper Pliensbachian, predominantlysandstone unit occurring in the western basin. In the east-central basin the unit. referredto as the Heiberg Formation, is more lithologically homogeneous and includes the LowerToarcian beds. The Heiberg in both areas is overlain by the Wilkie Point Group. Thetwo lowermost formations of the Wilkie Point Group, the Jameson Bay and SandyPoint, are Toarcian and will be examined in more detail.The Heiberg Formation, in the east-central basin, is Norian to Early Toarcian in age. Itis conformably underlain by shales of the Triassic Barrow Formation and conformablyREGIONAL GEOLOGY 14overlain by shales of the Toarcian Jameson Bay Formation. According to Embry (1983),it is essentially the same sequence of rocks that were initially designated the HeibergFormation by Souther (1963) at the type section of the unit at Buchanan Lake, AxelHeiberg Island. It also includes the Borden Island Formation from western EliesmereIsland (Tozer. 1963a), eastern Axel Heiberg Island (Tozer, 1963a) and Cornwall Island(Balkwill, 1983), and the two lower members of the Jaeger Formation (JjA and JjB)from Cornwall Island (Balkwill, 1983). The Heiberg Formation is predominantlysandstone with some interbedded siltstone and shale. It was deposited in a deltaicnearshore environment and can be divided into three members: Romulus, Fosheim andRemus.The Heiberg Group, in the western basin, is coeval with the Heiberg Formation of theeast-central basin but can be subdivided into five formations: Skybattle, GrosvenorIsland, Maclean Strait, Lougheed Island and King Christian. The King ChristianFormation can be divided into three members: Drake Point, Stupart and Whitefish. TheWhitefish Member is Late Pliensbachian in age and is laterally equivalent to the basalJameson Bay Formation on Borden and Melville islands from which Late Pliensbachianammonites have been collected. To the east the Whitefish Member grades into theRemus Member of the Heiberg Formation. The lower part of the Whitefish Member is afine grained, bioturbated sandstone with shale-siltstone partings probably deposited in adelta front environment. It is overlain by a more massive fine to medium grainedsandstone which was deposited as a distributary mouth bar deposit. This is capped by acommonly glauconitic, burrowed, slightly argillaceous sandstone deposited as a deltadestructional facies.REGIONAL GEOLOGY Jameson Bay FormationThe Jameson Bay Formation is widely distributed throughout the basin and wasassigned to parts of the Wilkie Point, Savik, and Jaeger formations in previous studies.It is a predominantly shale unit and conformably overlies the King Christian Formationin the west but unconformably along the basin margins. In the east-central basin itconformably overlies the Heiberg Formation. It is conformably overlain by the SandyPoint Formation, except in the basin centre where the Sandy Point Formation may beabsent due to facies changes, and is then conformably overlain by shales of theMcConnell Island Formation. It is primarily medium to dark green-grey shales withsiltstone laminae and interbeds and is thickest in the centre of the basin, reaching amaximum in the subsurface of 539 m. It is Late Pliensbachian to Aalenian in age andrepresents an offshore shelf environment. In the western basin, the Jameson BayFormation is divided into three members: Intrepid Inlet, Cape Canning and Snowpatch. Sandy Point FormationThe Sandy Point Formation was referred to parts of the Jaeger, Wilkie Point and Savikformations by earlier workers (Tozer & Thorsteinsson, 1964; Stott, 1969; Balkwill, 1983).It is conformably to unconformably overlain by the McConnell Island Formation. On thebasin edges the Sandy Point Formation may be overlain by the Upper Jurassic RingnesFormation. The Sandy Point Formation is primarily interbedded sandstone. siltstoneand shale with coarsening upwards cycles. The shales are medium grey-green and silty.The siltstone is light to medium grey and argillaceous to arenaceous. The sandstonesmay be up to 30 m thick and coarsen upwards from very fine to medium grained. Thesandstone units are usually extensively burrowed and are commonly interbedded withmassive to horizontally bedded sandstone. Along the basin margin there may be apebbly, medium to coarse grained sandstone. The Sandy Point Formation is absent orREGIONAL GEOLOGY 16thin in the centre of the basin (east-central Ellef Ringnes, northern Amund Ringnes andwestern Axel Reiberg islands) due to facies changes. It reaches a maximum thickness of162 m and is Toarcian to Aalenian in age. It represents a nearshore marine shelfenvironment.2.3 Brooks-MacKenzie Basin (B)2.3.1 IntroductionThe Brooks-MacKenzie Basin extends from the Richardson Mountains (Yukon) in theeast to the Delong Mountains (Alaska) in the west (Figure 1-1 and Figure 2-4). Duringthe Early Jurassic, nearshore sediments of the Bug Creek Group were deposited alongthe southeast margin and interfinger to the northwest with the basinal sediments of theKingak Shale. The MacKenzie Basin refers to the northern Yukon, whereas the BrooksBasin refers to northern Alaska.2.3.2 MacKenzie Basin2.3.2.1 InLroductionThe geology of the basin was discussed by Young, Myhr, and Yorath (1976), with morerecent stratigraphic revisions by Poulton (Poulton, 1978a, 1978b, 1978c, 1982, 1988,1989; Poulton, Leskiw, and Audretsch, 1982). Jeletzky (1967, 1971, 1972) did much ofthe initial work on the Mesozoic stratigraphy of the region and Frebold (1958b, 1960,1964, 1975; Frebold, Mountjoy, and Tempelman-Kluit, 1967) identified many of theJurassic ammonites. Toarcian deposits occur throughout the basin except in the easternRichardson Mountains where they have been removed by a Middle Jurassic erosionalevent.REGIONAL GEOLOGY St’ratigraphyThe Bug Creek Formation was defined by Jeletzky (1967, p. 13) as a predominantlysandstone unit of Sinemurian to Tithonian age. Poulton, Leskiw, and Audretsch (1982)presented a comprehensive, revised stratigraphy of the unit by elevating it to groupstatus and introducing new formations and members. The following stratigraphicsummary is taken from their work.Bug Creek GroupThe Bug Creek Group is the Lower Jurassic to Lower Oxfordian southeastern equivalentof the Kingak Shale, becoming thicker and more argillaceous to the northwest. Fiveformations are included within the group and can be placed into two main subdivisionsseparated by a Middle Jurassic hiatus: the Murray Ridge, Alstrom Creek and ManuelCreek formations below the hiatus and the Richardson Mountains and Aklavikformations above. The Bug Creek Group unconformably overlies a Permian sandstoneunit, although this may be locally absent and is then underlain by the DevonianImperial Formation. Erosional remnants of the Upper Triassic Shublik Formation ofAlaska may be present in the south to southeast. The Bug Creek Group is conformablyoverlain by the Upper Jurassic to Lower Cretaceous shales and sandstones of the HuskyFormation.Murray Ridge FormationThe Murray Ridge Formation is a coarsening upward sequence of shales and mudstoneswidespread in the northern Richardson Mountains. The unit represents fairly quiet, openmarine conditions with a Late Paleozoic source to the south and east and a generalshallowing upwards trend. It is Early to Late Sinemurian in age and is conformablyoverlain by the Alstrom Creek Formation.Alstrom Creek FormationREGIONAL GEOLOGY 18The Aistrom Creek Formation is a bioturbated, commonly glauconitic sandstone unit.The eastern exposures commonly contain oysters in the upper beds which suggests anearshore, possibly brackish, environment. The northwestern, more basinal exposurescontain Lingula in the lower beds, which suggests deposition on a marine shelf (Poulton,et al., 1982). The unit is bracketed by Late Sinemurian and Early to Middle Toarcianfaunas and an outcrop in Old Crow Flats yielded an Amaitheus (?) (G.S.C. Loc. 53458,88278; Poulton, 1978a, p. 458) suggesting a Pliensbachian age. It is conformably overlainby the Manuel Creek Formation.Manuel Creek FormationThe Manuel Creek Formation is a predominantly recessive, argillaceous unit that iswidespread in the northern Richardson Mountains but is absent in the eastern andsoutheastern parts of the basin due to Middle Jurassic erosion. It is characterized bydark grey to black shales, mudstones, and siltstones with thin sandstone interbeds andrusty concretions. Siltstones and sandstones are common near the top of the unit in theeastern and southeastern exposures and are usually thinly bedded, laminated,crossbedded and ripple marked, with evidence of bioturbation. The unit was depositedon an open marine shelf during a transgressive event and the poor fossil diversitysuggests unfavourable water conditions may have existed. The Anne Creek Member is athinly laminated to massive, upper sandstone unit with crossbedding, bioturbation andrip-up clasts. It is exposed near the headwaters of /Vaters River and represents ashoaling event. The Manuel Creek Formation is Toarcian to Aalenian in age and isunconformably overlain by the Richardson Mountains Formation.In the southwestern part of the basin in the Ogilvie Mountains and in the adjoining partof Alaska, the Kingak Shale and its equivalent, the Glenn Shale, have been mapped. TheGlenn Shale (Brabb, 1969, p. 19-113) is a fissile, greyish-black carbonaceous shale whichgrades upwards into greyish-black, massive argillite and siltstone containing carbonateREGIONAL GEOLOGY 19SOUTh BARROWWELL 3GULF OF ALASKAFigure 2-4 - Location map of Toarcian localities from Alaska.REGIONAL GEOLOGY 20concretions a few centimetres in diameter. A 15 to 61 m (50 to 200 foot) thick,fossiliferous limestone may occur near the base. The unit is Middle Triassic (Ladinian) toLate Valanginian (Cretaceous) in age. Hettangian and Pliensbachian ammonites wereidentified (Imlay, 1981, p. 6-7) but no Toarcian, although it is probably representedstratigraphically.2.3.3 Brooks Basin2.3.3.1 IntroductionIn general, Toarcian rocks are poorly exposed in northern Alaska (Figure 2-4) but a fewammonites indicate that most of Toarcian and Pliensbachian time is represented,possibly the Sinemurian as well. The following descriptions are from Imlay (1955),Detterman, Reiser, Brosgé, and Dutro (1975), and Imlay (1981). StratigraphyIn northern Alaska the Lower Jurassic Kingak Shale is a dark olive grey to black shalewith some siltstone, claystone and clay ironstone (Detterman et al., 1975); the containedfauna was updated by Imlay in 1981. The lowest part of the Kingak Shale is aSinemurian to Pliensbachian, fissile, black paper shale up to 180 m thick. The shalefractures and weathers into centimetre long slivers. It contains large concretions in themiddle of the unit over an interval of 45 m. It is overlain by 90 m to 300 m of UpperPliensbachian to Upper Toarcian soft, dark-grey clay shale with some claystone. Theupper part of this unit may contain clay ironstone nodules usually weathering a bright,brick red. Overlying the claystone is a thin-bedded Middle Jurassic siltstone and siltyshale and an Upper Jurassic black clay shale with irregularly shaped, grey, clay-ironstonenodules. The Kingak Shale has many diastems and varies rapidly in thickness over asmall area.REGIONAL GEOLOGY 212.4 Whitehorse Trough (C)2.4.1 IntroductionThe Whitehorse Trough is the sedimentary basin in which the Lower Jurassic LabergeGroup was deposited. It extends from the southern Yukon through Bennett, Atlin, andTulsequah areas and east to Cry Lake area (Figure 2-5). The basin is part ofnorthernmost Stikinia and is bounded on the east by the Nahlin Fault, which separatesit from the Atlin terrane (an extension of the Cache Creek terrane) and on the southwestby the Stikine Arch. The Laberge Group is underlain by Upper Triassic volcanics andvolcanic sediments including several coeval units: the Lewes River Group in the Yukon,and the Stuhini Group and Sinwa Limestone in northern British Columbia.2.4.2 StratigraphyThe Laberge Series was first described by Cairnes (1910. p. 30) for rocks of Jurassic orCretaceous age in southern Yukon. Buckman, in Cockfield and Bell (1926, p. 21),reported Middle Lias to Middle Jurassic fossils. Wheeler (1961) mapped the Whitehorsemap area and defined the Laberge Group as Lower to Middle Jurassic but did notformally subdivide it. Aitkin (1959) in the Atlin area recognized the Laberge Group butdid not define it or subdivide it. Souther (1971a) in the Tulsequah map area recognizedtwo facies: the coarse-grained, near-shore Takwahoni in the southwest, and theargillaceous, basinal Inklin in the northeast. Toarcian fossils occur within the Takwahonifacies and there is a possibility that they also occur in the Inklin (Tipper, pers. comm.).The following lithologic summaries are based on Souther (1971a).In/dinThe Inklin Formation is an approximately 3050 m (10,000 foot) thick sequence ofpredominantly shales and siltstones with minor greywacke and conglomerate.‘ /I ‘ /I ij •1 I’jJ/\jQUESNEL \ \ NORTHERN FERNIETYAUGHTON CREEK1 I ‘ \I I \t• • I tI-.G ‘IHARRISON.‘.—___ MANNING PAF< \ SOUTHERN FERNIES. ‘ ‘;b4 Ø•--L INELSON AND SALMOFigure 2-5 - Location map of the Toarcian localities from the Canadian Cordillera.Whitehorse (C), Hazelton (D), Fernie (E), Quesnellia (F), ‘Methow (G), and QueenCharlotte (K) basins are dashed.REGIONAL GEOLOGY130 125YUKON120BENNETtATUN5565S.’/.5.‘S‘S.-‘S-S.—/—5--•-,. 115//‘//D ////\110•120 15• 1O•REGIONAL GEOLOGY 23Convoluted bedding, slump structures, graded bedding. and intraformationalconglomerates are present throughout the unit. The absence of ripple marks and generallack of fossils (which are abundant in the Takwahoni) suggests a fairly deepenvironment. The unit was probably deposited by turbidity currents off a delta intodeeper water. It is possibly Hettangian to Early Bajocian in age (Tipper, pers. com.,1992).2..2.2 TakwahoniThe Takwahoni Formation is a thick assemblage (approximately 3350 m (11,000 feet)) ofinterbedded conglomerates, greywackes, siltstones, and shales. It undergoes rapid facieschanges and has local unconformities due to channelling, both of which suggest a rapidlysubsiding basin near a source area of high relief. The unit was probably derived from avolcanic terrane but primary volcanic rocks are absent or restricted to the lower hundredmetres of the formation (Souther, 1971a). The most complete section is in the Tulsequaharea (C-4-A). Conglomerates are usually confined to the lower half of the section andmay reach 275 m (900 feet) in thickness with 30 m (100 foot) thick beds being commonin the southern part of the Tulsequah area. Hettangian, Sinemurian, and LatePliensbachian fossils have not been found.2.5 Hazelton Trough (D)2.5.1 IntroductionThe Hazelton Trough occupies much of Stikinia, from the Stikine Arch in the north tothe Yalakom Fault in the south and falls into three distinct areas: the northern areaincluding the Iskut, Telegraph, Spatsizi, and Toodoggone areas (Figure 2-5), the eastcentral area including the McConnell Creek, Hazelton, Smithers, Nechako, and Whitesailareas (Figure 2-5), and the southern area which is poorly exposed and understood.REGIONAL GEOLOGY 242.5.2 Northern area2.5.2.1 ImtroductronLower Jurassic rocks outcrop along the margins of the Bowser Basin and are bounded tothe north by the Stikine Arch and to the west by the Coast Plutonic Complex. Broadstratigraphic comparisons can be made between the Iskut, Telegraph Creek and Spatsizimap areas. The Upper Triassic Stuhini Group underlies all regions and is capped by aLower Jurassic, predominantly volcanic, sequence. The volcanics are overlain by a Lowerto Middle Jurassic sedimentary sequence which is unconformably overlain by sedimentsof the Bowser Lake Group (Middle Jurassic to Cretaceous). Correlation of the Lower andMiddle Jurassic rocks between the three areas is difficult due to structural complexitiesand a lack of good fossil control. Iskut arid Telegraph Greek areasRecent gold and silver discoveries in the Lower Jurassic rocks of the Eskay Creek areahave fueled an intensive geological study of the region (Alidrick and Britton, 1988;Alldrick et al., 1989; Anderson, 1989; Anderson and Thorkelson, 1990), which has shedsome light on the stratigraphy. The following summary is taken primarily from Andersonand Thorkelson (1990).The Upper Triassic Stuhini Group is conformably to unconformably overlain byvolcanics and sediments of the Hazelton Group. The Hazeiton Group is Lower to MiddleJurassic and includes the volcanogenic Unuk River, Betty Creek, and IViount Dillworthformations which are overlain by sediments of the Salmon River Formation.Anderson and Thorkelson (1990) restricted the Salmon River Formation to upper LowerJurassic and lower Middle Jurassic strata and Evenchick (1991) follows this same usagein the Telegraph Creek area. The Salmon River Formation has two members: a basal,REGIONAL GEOLOGY 25thin. belemnoid-rich. upper Lower Jurassic calcareous sandstone and an overlying Lowerto Middle Jurassic member with three facies. The basal member is a rusty brown orgreen, fossiliferous greywacke, usually 60 to 100 cm thick. It is the only consistentlyfossiliferous Jurassic unit in the map area and was thought to be Toarcian in age. It isnow recognized as Triassic (Nadaraju pers. comm., 1992). The upper member of theSalmon River Formation contains three northward trending facies: Troy Ridge, EskayCreek, and Snippaker Mountain. The Troy Ridge is the easternmost facies and is ablack, siliceous, radiolarian-hearing shale with white, reworked tuff turbidites and iscommonly referred to informally as ‘pyjama beds”. It is similar to the Lower BajocianQuock Formation in the Spatsizi area (Thomson, Smith, and Tipper, 1986) and theYuen Member of the Smithers Formation in the Smithers area (Tipper and Richards,1976). The Eskay Creek facies is a unit of pillowed lava and limy to siliceous shale andsiltstone. It is Late Pliensbachian to Early Bajocian in age. Similar clastics and pillowlavas occur in the Telegraph Creek area (Evenchick, 1991). The Snippaker Mountainfacies is a unit of andesitic volcaniclastics which shows some similarity to rocks in theTelegraph Creek area. There is a northerly trend to the facies and an apparent shalingout to the north, where basinal sediments are more common. SpaLsizi areaThomson, Smith, and Tipper (1986) produced the most comprehensive and recent reporton the Lower Jurassic rocks of the Spatsizi area. Rocks of the Stuhini Group andHotailuh Intrusions are overlain by the Plienshachian to Lower Bajocian Cold FishVolcanics. The volcanics are conformably overlain by the predominantly sedimentarystrata of the Spatsizi Group. The Cold Fish volcanics and the Spatsizi Group are coeval,in part, with the Hazelton Group, but Thomson (1985) felt that they could bedistinguished because:REGIONAL GEOLOGY 261. the two rock units, although partly time equivalent, are geographically separatefrom one another.2. volcanics in the northern part are related to the Stikine Arch whereas theHazelton volcanics are related to the plutonic core of the ancestral Skeena Arch.Spatsizi GroupThe five formations of the Spatsizi Group were defined by R.C. Thomson after field workin the Joan Lake area in 1981-83. The following descriptions are taken from his M.Sc.thesis (Thomson, 1985) which is currently being revised prior to publication as a G.S.C.Bulletin.The Spatsizi Group is Pliensbachian to Early Bajocian in age and lies disconformably onCold Fish volcanic flows and is overlain, with a slight (< 5°) angular unconformity, bythe Ashman Formation of the Bowser Lake Group. The five formations, in ascendingstratigraphic order, are: Joan, Wolf Den, Melisson, Abou, and Quock.The Joan Formation is Early Pliensbachian in age and is primarily medium-beddedsiltstone, with minor interbeds of mudstone and silty limestone, and a thin, locallydeveloped basal conglomerate that grades laterally to pebbly sandstone and possibly siltyshale.The Wolf Den Formation attains a thickness of 280 m. It is Late Pliensbachian toMiddle Toarcian in age. It is composed mainly of dark grey to black, fissile to blockyweathering shale with three concretionary beds and minor tuffaceous beds or lenses.The Melisson Formation attains a maximum thickness of about 130 m, and is wellexposed in the Joan Lake area where its resistant beds underlie prominent ridges. TheMelisson Formation consists of medium bedded, siliceous to calcareous siltstones and finesandstones with minor silty calcarenite beds. Fossil content of the Melisson Formation isREGIONAL GEOLOGY 27restricted to dicoelitid belemnites that are usually sparse but may be abundant in a fewbeds. The lower contact of the Melisson Formation with the underlying shales of theWolf Den Formation is conformable. The age of the Melisson Formation is not wellconstrained due to the absence of ammonites. The presence of the late Middle Toarcianammonites (Denckmamnia and Phymatoc eras hillebrandti) in shales underlying theMelisson Formation, and dicoelitid belemnites within the Melisson Formation suggest aLate Toarcian age.The Abou Formation is a fairly thin unit of siliceous shale. The lower contact of theAbou Formation is an erosional unconformity. In places, the entire thickness of theunderlying Melisson Formation was completely eroded away before the deposition of theAbou and Quock Formations took place. The ammonite Tmetoc eras commonly found inthe Abou Formation indicates an Aalenian age for the formation.The Quock Formation is an Upper Aalenian? and Lower Bajocian, thinly bedded tolaminated siliceous shale with distinctive banding and reddish-brown weathering,commonly referred to as ‘pyjama beds.2.5.2. ToodoggoneWithin the Toodoggone area, one collection of Toarcian ammonites from a volcanic unitnear Claw Mountain. resembles Late Toarcian forms such as Pieydeliza and Podagrosites(D-5-A- East-central area2.5.3. .1 IntroductionThe Lower Jurassic in this region is represented by the Hazelton Group, a unit whichhas undergone frequent revisions in the literature. Tipper and Richards (1976) attemptedREGIONAL GEOLOGY 28a regional synthesis of the unit and subdivided it into formations and members. Richards(1991) recently updated the Hazelton map area and the Smithers map area is currentlybeing revised by Richards. A regional correlation with rocks from the northern andnorthwestern Hazelton Trough has yet to be done and the relationships of the rocks inthese areas are unknown. StratigraphyThe Upper Triassic Stuhini Group occurs over much of the east-central part of the basin(McConnell Creek - Hazelton- Smithers) and in earlier works (Tipper and Richards,1976), was referred to the Takia Group. It is a subaqueous volcanic unit with augiteporphyry flows, breccia, tuff, shale, greywacke and minor limestone, and feldsparporphyry.The Hazelton Group was divided into three formations by Tipper and Richards (1976):Telkwa, Niikitkwa and Smithers. Recent studies in the Hazelton and Smithers map areas(Richards, 1991) have upheld these, with the addition of a volcanic unit between theNilkitkwa and Smithers formations. The Hazelton Group is a thick, widespreadassemblage of basaltic to rhyolitic volcanic rocks, sedimentary rocks, their tuffaceousequivalents, and minor limestone. It was considered to be Sinemurian to EarlyCallovian? in age, but recent work suggests it is no younger than Early Bajocian(Tipper, 1992, pers. comm.).The Telkwa Formation is a predominantly volcanic unit of Sinemurian to EarlyPliensbachian age. It is overlain by the Nilkitkwa Formation, an Upper Sinemurian toBajocian sequence of well-bedded, distal marine tuffaceous argillite, shale, siltstone,greywacke, ash and lapilli tuff, with minor limestone and conglomerate. The NilkitkwaFormation contains a Toarcian volcanic unit, the Ankwell Member, a sequence ofsubaqueous volcanic flows and pyroclastics, overlain by massive bedded reddish subaerialREGIONAL GEOLOGY 29basalt flows and intercalated volcaniclastic sediments. Minor thin limestone biohermsand lenses, rhyolite and subaqueous basait-andesite lenses also occur. The NilkitkwaFormation is overlain by Aalenian to Bajocian? volcanics and volcaniclastic sediments ofthe Saddle Hill volcanics in the Hazelton area and the Eagle Peak volcanics in theSmithers area. These are overlain by the Smithers Formation, an Aalenian to Bajocianunit of interbedded, shallow marine volcaniclastic tuffaceous sandstone, siltstone, andgreywacke, with minor conglomerate and local glauconitic sandstone. In the McConnellCreek area, the Smithers Formation extends into the Toarcian (Tipper and Richards,1976).2.6 Southern Canadian Rocky Mountains (E)2.6.1 IntroductionThe Jurassic Fernie Formation is a widespread unit ranging from southwestern Albertato the Peace River area of northeastern British Columbia. The region was arbitrarilydivided into a northern and a southern region. The following lithologic description istaken primarily from Hall (1984, 1987) and Stronach (1984).2.6.2 StratigraphyHall (1984) recommended that the Fernie be retained as a formation as the numerousinformal ‘members” and beds of the unit, commonly defined by both biostratigraphicand lithostratigraphic criteria, may have a variety of rock types in their lateral extension.In the southern and central areas of exposure, the lower Fernie comprises a dark shalewith calcareous intercalations or a phosphatic conglomerate, with abundant bivalves andgastropods. In the northern area, the black, cherty limestones of the Nordegg Memberform the base. The oldest ammonites are Early Sinemurian in age, alt