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Geology of the central Moresby Island region, Queen Charlotte Islands, (Haida Gwaii) British Columbia Taite, Susan Patricia 1991

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GEOLOGY OF THE CENTRAL MORESBY ISLAND REGION,QUEEN CHARLOTTE ISLANDS, (HAIDA GWAII)BRITISH COLUMBIAbySUSAN PATRICIA TAITEB.Sc., The University of British Columbia, 1987A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF SCIENCEinTHE FACULTY OF GRADUATE STUDIESDepartment of Geological SciencesWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIASeptember 1991© Susan Patricia Taite, 1991In presenting this thesis in partial fulfilment of the requirements for an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature)Department of ^E. L-tThe University of British ColumbiaVancouver, CanadaDate ^':IYAN—) •^- t C)C) 2 . DE-6 (2/88)AbstractThe Queen Charlotte Islands represent the most outboard exposure of Wrangelliain the Canadian Cordillera. This study analyzes the structural and stratigraphic history ofthe central Moresby Island area, and correlates this history with ongoing and previousstudies in the Queen Charlotte Islands. The stratigraphic succession preserved in centralMoresby Island comprises marine volcanic and sedimentary rocks of the TriassicKarmutsen Formation and Kunga Group, Middle Jurassic arc volcanic rocks of theYakoun Group, marine sedimentary rocks of the Longarm Formation and QueenCharlotte Group, and Tertiary volcanic rocks.The Karmutsen Formation and Kunga Group rocks exposed in central MoresbyIsland formed during a widespread Triassic volcanic event followed by marine carbonateand clastic sedimentation. Coarse clastic lithologies in the Kunga Group indicate avolcanic provenance as early as the Norian. The Early to Middle Jurassic marinesedimentary rocks of the Maude Group, present elsewhere in the Queen CharlotteIslands, are absent in central Moresby Island. Oldest rocks of the clastic LongarmFormation in central Moresby Island are of Hauterivian age, and the conformablyoverlying Queen Charlotte Group extends into at least the Turonian. Both field andpetrographic evidence suggest two distinct suites of Tertiary volcanic rocks exist incentral Moresby Island.Dominant megascopic structures in central Moresby Island are dominated bynorth, northeast and northwest-trending fault sets. Folding is common in stratifiedKunga Group lithologies, and only of minor importance in younger successions. Thedeformational history outlines five events: Middle Jurassic shortening, Middle to LateJurassic extension, post-Cretaceous and pre-Tertiary shortening, post-Cretaceous and pre-(syn ?) Tertiary extension, and a syn (?) to post-Tertiary extension.The structural history outlined for the central Moresby Island area providesseveral refinements to pre-existing models. It provides evidence that Middle Jurassicshortening continued into and possibly outlasted Yakoun Group arc volcanism.Cretaceous block faulting, documented on Graham Island and northern Moresby Island,extended into central Moresby Island. Asymmetric south-directed Tertiary extension,documented on southern Moresby Island, also extended into central Moresby Island, andhas implications to the offset history of regional faults.iiTable of ContentsAbstract^ iiTable of Contents^ iiiList of Figures viAcknowledgements viii1. INTRODUCTION^ 1Location  1History and previous work^ 3Geologic setting^ 4Objectives and methods 82. STRATIGRAPHY 10Introduction to the stratigraphic history^  10The Wrangellian succession: Upper Triassic to lower Middle JurassicKarmutsen Formation and Kunga Group 15Karmutsen Formation^ 15Kunga Group^ 18Sadler Limestone  18Peril Formation^ 20Sandilands Formation 26Depositional Environments 29Arc Volcanism: Middle Jurassic (Bajocian) Yakoun Group^ 32Yakoun Group rocks in central Moresby Island 32Lapilli tuffs and interstratified sedimentary rocks^ 33Debris flows and lahars^ 35Conglomerate and sandstone 35Shale and siltstone 39Depositional environments^ 39Jurassic Intrusive Rocks 41Cretaceous Marine succession: Longarm Formation and the QueenCharlotte Group^ 42Cretaceous Stratigraphy Introduction^ 42Longarm Formation^ 44Queen Charlotte Group 52Haida Formation 52Skidegate Formation^ 52iiiHonna Formation^ 53Depositional environments 56Generic Stratigraphy 61Tertiary Volcanism^ 63History and Nomenclature^ 63Tertiary Volcanic Rocks in central Moresby Island^ 64Tertiary Intrusive Rocks in central Moresby Island 67Depositional environments^ 68STRUCTURAL GEOLOGY OF CENTRAL MORESBY ISLAND^ 70Introduction, previous work, and the evolution of objectives 70Structure of the central Moresby Island area^ 75Structural domains in central Moresby Island 76Domain boundaries^ 76Structure of the eastern and western domains^ 77Faults 78Northerly-striking faults 78Northeast-striking faults^ 82Northwest-striking faults 83Folds^ 84Northwest-trending folds^ 84Northeast-trending folds 85Structure of the Central Domain 90Faults^ 91Faults in Triassic and Jurassic strata^ 91Faults in Cretaceous and Tertiary strata 91Folds^ 92Folds in Triassic and Jurassic strata^ 92Folds in Cretaceous strata^ 94STRUCTURAL SYNTHESIS FOR CENTRAL MORESBY ISLAND^ 96Introduction^ 96Middle Jurassic northeast-directed shortening^ 96Post-Yakoun Group deposition and pre-Cretaceous deposition: blockfaulting^ 99Syn-Cretaceous tectonism^  108Post-Cretaceous deposition and pre-Tertiary folding^  108Post-Cretaceous and pre- (syn ?) Tertiary block faulting  109ivSyn (?) to post-Tertiary block faulting and extension^ 110REGIONAL SYNTHESIS^ 112Introduction  112Pre-Middle Jurassic deformation^ 112Middle Jurassic deformation:  113Post-Yakoun Group and pre-Cretaceous block faulting^ 114Deposition of the Cretaceous succession^  114Cretaceous shortening^  115Post-Cretaceous block faulting^  115Tertiary block faulting  116CONCLUSIONS^ 116REFERENCES 118APPENDICES 116Appendix 1: Paleocurrent data^  116Appendix 2: Stereograms of structural data^  116Appendix 3: Fossil identification data  116GEOLOGY OF CENTRAL MORESBY ISLAND (map plate)^back pocketList of Figures:Figure 1.1 Location map of study area and the Queen Charlotte Islands ^ 2Figure 1.2 Major tectonic elements of the Queen Charlotte Islands 6Figure 1.3 Geologic mapping limits prior to 1989 field season^ 7Figure 2.1 Stratigraphic chart for the Queen Charlotte Islands  13Figure 2.2 Stratigraphic chart for central Moresby Island 14Figure 2.3 Karmutsen Formation: distribution map of lithotypes^ 17Figure 2.4 Karmutsen Formation: massive lithology ^ 19Figure 2.5 Karmutsen Formation: glomeroporphyry lithotype ^ 19Figure 2.6 Sadler Limestone: karst weathering 21Figure 2.7 Sadler Limestone: stylolites^ 21Figure 2.8 Sadler Limestone: bioclastic limestone^ 22Figure 2.9 Sadler Limestone: alteration minerals 22Figure 2.10 Peril Formation: lithology in outcrop 24Figure 2.11 Peril Formation - Sadler Limestone contact^ 24Figure 2.12 Peril Formation: pelmetazoan calcarenite 25Figure 2.13 Peril Formation: photomicrograph of bioclastic carbonate^ 25Figure 2.14 Sandilands Formation: lithology in outcrop^ 27Figure 2.15 Sandilands Formation: greywacke^ 27Figure 2.16a Sandilands Formation: greywacke 30Figure 2.16b Sandilands Formation: greywacke 30Figure 2.17 Yakoun Group: distribution map of lithotypes^ 34Figure 2.18a Yakoun Group: lapilli tuff^ 36Figure 2.18b Yakoun Group: lapilli tuff 36Figure 2.18c Yakoun Group: lapilli tuff 37Figure 2.18d Yakoun Group: lapilli tuff^ 37Figure 2.19a Yakoun Group: debris flow 38Figure 2.19b Yakoun Group: debris flow 38Figure 2.20 Yakoun Group: cobble conglomerate^ 40Figure 2.21 Yakoun Group: shale and siltstone 40Figure 2.22 Longarm Formation: basal unconformity 47Figure 2.23 Longarm Formation: elastic dyke^ 47Figure 2.24 Longarm Formation: boulder conglomerate^ 48Figure 2.25 Longarm Formation: inoceramid 48Figure 2.26 Longarm Formation: chondrites^ 49viFigure 2.27 Longarm Formation: cross bedding ^ 49Figure 2.28 Longarm Formation: pebble conglomerate 50Figure 2.29 Longarm Formation: elastic dykes 50Figure 2.30a Skidegate Formation: turbidites^ 54Figure 2.30b Skidegate Formation: turbidites 54Figure 2.31a Honna Formation: interbedded with Skidegate Formationturbidites^ 55Figure 2.31b Honna Formation: monotis-bearing clast ^ 55Figure 2.32 Cross section of facies relationships for the Cretaceous section^ 59Figure 2.33 Cretaceous lithologies: distribution map of lithotypes^ 60Figure 2.34a Tertiary volcanic rocks: debris flow^ 65Figure 2.34b Tertiary volcanic rocks: debris flow 65Figure 2.35a Tertiary volcanic rocks: photomicrographs 66Figure 2.35b Tertiary volcanic rocks: photomicrographs^ 66Figure 3.1 Faulted and folded strata in fault zone 79Figure 3.2 Blunt Point Fault^ 81Figure 3.3 Fold classification 86Figure 3.4 Stereographic plot of poles to bedding: Kunga Group^ 87Figure 3.5 Stereographic plot of poles to bedding: Yakoun Group 88Figure 3.6 Folded thrust fault^ 89Figure 3.7 Folds and faults in Peril Formation^ 93Figure 3.8 Stereographic plot of poles to bedding: Cretaceous strata^ 95Figure 4.1 Basement control on cover geometry 98Figure 4.2a Compilation of strain estimates^ 100Figure 4.2b-f Sandilands Formation: strain estimates of outcrop photographs ^ 101Figure 4.3 Fault in Yakoun Group^ 106Figure 4.4 Deformed ammonite used in strain estimates^ 107viiAcknowledgementsI would like to thank the Geological Survey of Canada for continued supportthroughout this project. I especially thank Dr. R. Thompson for suggesting this project,and Dr. J. Haggart for supervising throughout.Doctors John Ross, Paul Smith, Bill Barnes, Kelly Russel, and Marc Bustinprovided academic support from the University of British Columbia.Fellow graduate students Joseph Palfy, Jonny Hesthammer, Jarand Indrelid, HenryLyatsky, and Charle Gamba provided valuable discussion during the development of thisthesis.I would like to thank the residents of Sewell Inlet in the Queen Charlotte Islandsand the employees of Western Forest Products for their friendship and assistance. Inparticular, Buzz Vidal, Bill Waugh, Joe Farkoush, Kevin Warwick and the Colliers.Audrey and Dave Putterill provided excellent expediting from QC city.Fellow graduate students at UBC, Regan Palsgrove, Steve Sibbeck, HarrisonCookenboo, Kieth Everard, Pasakorn Papongsawon, and Tracy Delaney are thanked fortheir friendship.I would especially like to thank my parents, and Peter Lewis, whose enthusiasmknows no boundaries, and whose love and support was unflagging.viiiIntroduction / Location^ 11 INTRODUCTION1.1^Location The Queen Charlotte Islands lie off the northwest coast of British Columbia,Canada, and comprise an archipelago of approximately one hundred and fifty islands.Two main islands represent most of the land mass, Graham Island in the north, andMoresby Island in the south (Figure 1.1). Most of Moresby Island, and the west coast ofGraham Island are mountainous and rugged, whereas the eastern part of Graham Islandforms a broad lowland. The study area is situated in central Moresby Island, andincludes the region surrounding Sewell Inlet, Newcombe Inlet, and Wilson Bay. Itoccurs between 52°55' N, 132°10' W, and 52°45' N, 131°50' W, and coversapproximately 150 square kilometres (Figure 1.1).The climate of the Pacific coast of British Columbia is temperate, and the florawithin the Queen Charlotte Islands is dominated by coastal rain forest. Giant first growthtrees are extensively harvested on both Graham and Moresby islands, and logging andfishing form the economic base of the islands. Tourism is becoming increasinglyimportant with the creation of a new national park on southern Moresby Island dedicatedto the preservation of the ancient climax forests. Wildlife is abundant, and consists ofboth endemic and introduced species of mammals, and diverse migratory and residentbird populations.The central Moresby Island study area coincides largely with the area managed byWestern Forest Products in Sewell Inlet. Access is by float plane or helicopter from thevillage of Sandspit on northern Moresby Island, or by boat from Moresby Camp at thehead of Cumshewa Inlet (Figure 1.1). Logging roads are extensive within the study133'^ 132'^ 131'HecateStraitBurnaby IslandGrahamIslandRennellSoundLong InletPacificOceanCentral MoresbyIslandmap areaSandspitMoresbyIsland^c„,„,„Louise^'IIsland^ewa roietSewell Inlet<7Talunkwan IslandTasu SoundIntroduction / LocationFigure 1.1: Map showing the major islands of the Queen Charlotte Islands, and theposition of the central Moresby Island study area. Inset map shows the position of theislands in British Columbia, and relative to the five tectonic belts of the CanadianCordillera.Introduction / Location^ 3and the majority of geologic observations are from road cuts and road metal quarries; therest were made from stream exposures, ridge tops, shore exposures and rare outcrops inforest1.2 History and previous workThe Queen Charlotte Islands, also known as Haida Gwaii are the ancestral homefor the Haida Indians. These seafaring warriors have inhabited the region for thousandsof years. The history of European explorers date to the voyages of discovery of Dixon,Juan Perez, Caamano, and others in the Sixteenth and Seventeenth centuries. Scientificinvestigations initiated with the reconnaissance study of Richardson (1873), and G.M.Dawson's remarkable natural science and anthropology treatise in 1878. Since then, thediverse geology within the islands has attracted the attention of many researchers, bothacademic and industrial. Their work has been invaluable in deciphering the geologichistory of the islands, and relevant parts are reviewed in later sections of this thesis.Notable among these studies is that of Sutherland-Brown (1968). Initiated in 1958 withthe goal of cataloging possible iron-ore exploration targets on Moresby Island, it wasextended in 1961 to include all of the islands and resulted in the first account of thegeology of the entire Queen Charlotte Islands.In 1987, the federal government of Canada, acting on a mandate to evaluate thehydrocarbon reserves in Canada, charged the Geological Survey of Canada with the taskof exploring the frontier basins. The Frontier Geoscience Program was the umbrellaorganization which united researchers from industry, academia, and government in thistask (Thompson, 1988a). Geologic mapping, geophysical surveys, and stratigraphic andIntroduction / History and previous work^ 4biostratigraphic investigations were among the studies engaged in during the first twoyears of the Frontier Geoscience Program in the Queen Charlotte Islands.By 1989, 1:50,000 scale geologic map coverage for much of central GrahamIsland and northern Moresby Island existed (Hickson, 1990a, 1990b; Hickson and Lewis,1990; Lewis and Hickson, 1990; Lewis et al, 1990; Thompson, 1990; Thompson andLewis, 1990a, 1990b; Figure 1.3). Several important conclusions regarding the geologicevolution of the region had already been reached. Firstly, Wrangellian strata were foundon the east side of Hecate Strait. Thus, the hydrocarbon exploration target (the QueenCharlotte Basin) is underlain by the potentially petroliferous strata exposed onshorewithin the Queen Charlotte Islands (Woodsworth, 1988; Thompson et al., 1991), and therelevance of onshore studies as an aid to hydrocarbon exploration increased. A secondimportant discovery was that the Queen Charlotte Islands likely were not dominated bystrike-slip tectonic styles as proposed in earlier models (Yorath and Chase, 1981; Yorathand Hyndman, 1983); instead, a tectonic history with multiple episodes of shortening andextension was revealed. The tectonic history of the Queen Charlotte Islands was thusmore complex than many had heretofore envisioned.1.3^Geologic SettingThe Queen Charlotte Islands lie along the west coast of North America, withinthe Insular Belt of the Canadian Cordillera (Figure 1.1). These islands are within theknown extent of Wrangellia, an allochthonous terrane which has been identified fromOregon (Vanier, 1977) to Alaska (Smith and MacKevett, 1970). The western margin ofWrangellia is defined by the Queen Charlotte Fault, the plate boundary between theNorth American and Pacific plates (Chase et al., 1975); the eastern margin is now placedsomewhere, as yet undefined, east of Hecate Strait (Woodsworth, 1988).Introduction / Geologic setting^ 5Strata exposed in the Queen Charlotte Islands range in age from Permian andpossibly Carboniferous (Hesthammer et al., 1991) to Tertiary. They have been dividedby many workers into four tectonostratigraphic sequences (Thompson et al, 1991; Lewisand Ross, 1991). The first comprises Paleozoic strata, Upper Triassic volcanic rocks ofthe Karmutsen Formation, and Upper Triassic and lower Middle Jurassic rocks of theKunga and Maude groups. The second comprises arc-related volcanic rocks andderivative sedimentary rocks of the Middle Jurassic Yakoun and Moresby groups. UpperJurassic to Cretaceous sedimentary rocks of the Longarm Formation and the QueenCharlotte Group represent a diachronous transgressive marine sequence, the thirdtectonostratigraphic division. Tertiary volcanic rocks and sedimentary rocks, the fourthsequence, cap the stratigraphic column. Three plutonic suites exist in the QueenCharlotte Islands: the Jurassic Burnaby Island plutonic suite, the Jurassic San Christovalplutonic suite, and the Tertiary Kano plutonic suite (Anderson and Greig, 1989); thelatter two suites are found within central Moresby Island. Units making up the majorstratigraphic divisions are more completely discussed in the stratigraphy section, chapter2, of this study.Structural studies based on both regional and detailed mapping, an important partof the Frontier Geoscience Program, defined four major episodes of deformation in theQueen Charlotte Islands. The oldest recognizable structures were formed during MiddleJurassic southwest-directed shortening, and include abundant folds and contractionalfaults (Lewis and Ross, 1991; Thompson et al., 1991). Late Jurassic through EarlyCretaceous time was characterized by block faulting which resulted in differentialpreservation of Mesozoic strata (Thompson and Thorkelson, 1989; Thompson etal.,1991). In Late Cretaceous to early Tertiary time, a contractional folding eventresulted in megascopic folds and faults in the Cretaceous strata (Indrelid, 1990;133'^ 132'^ 131'LONG INLETDEFORMATION ZONE-7^ LOUSCOONE INLETFAULT SYSTEMLEGENDCENTRAL MORESBY ISLANDMAP AREASAN CHRISTOVAL PLUTONIC SUITEIntroduction / Geologic setting^ 6Figure 1.2: Major tectonic elements of the Queen Charlotte Islands.13 3' 131'132'C-z)HecateStrait54'Central MoresbyIslandmap areaLouiseIslandApproximate areamapped prior to1 989 field season53'Introduction / Geologic setting^ 7Figure 1.3: Mapping coverage produced by Frontier Geoscience Program workersprior to the 1989 field season.Introduction / Geologic setting^ 8Thompson et al., 1991). In the late Tertiary extensional and strike-slip faulting was thedominant tectonic style, and was synchronous with the formation of the Queen CharlotteBasin, (Lewis, 1991a).Several major tectonic and geologic elements of the Queen Charlotte Islands haveundoubtedly influenced the geologic evolution of the central Moresby Island region(Figure 1.2). The Long Inlet deformation zone is a zone of intense Middle Jurassicthrough Tertiary deformation which trends north-northwest approximately ten kilometresnorth of the study area (Lewis, 1991b). The Louscoone Inlet fault system, the subject ofrecent detailed work by Lewis (1991a), is a complex zone coupling a strike-slip faultsystem with an area of asymmetric extension, and likely was active synchronously withTertiary extension in Hecate Strait. Strands of the Louscoone Inlet fault system occuralong the eastern boundary of the central Moresby Island study area. The San Christovalplutonic suite is a mountain-forming body of Middle Jurassic plutonic rocks which liessouthwest of the study area. The plate bounding Queen Charlotte Fault is presentlyactive as a dextral oblique-slip fault, and is situated ten kilometres offshore MoresbyIsland, west of the study area. These elements may all have influenced the structuralevolution of the central Moresby Island region, and resulted in structural styles in thearea unique within the Queen Charlotte Islands. Their influence on the structuralevolution of the study area is the subject of the structural synthesis and regionalcorrelation section presented in chapters 4 and 5.1.4 Objectives and MethodsThis study represents the first detailed geologic investigation conducted in thecentral Moresby Island area, and the initial objectives defined for this study weretherefore general. An initial objective was to identify the stratigraphy in central MoresbyIsland and test the lateral extent of stratigraphic divisions identified on northern MoresbyIntroduction / Objectives and methods^ 9Island and Graham Island. Another major objective of this study was to further thegrowing understanding of the structural evolution of the Queen Charlotte Islands, and totest the regional applicability of recent models developed through map studies elsewherein the islands. To this end, the author spent two field seasons in the area engaged ingeological mapping, stratigraphic, and sedimentological studies (Taite, 1990a;1990b;1991a, 1991b; Gamba et. al, 1990; Haggart et. al, 1991). Thin section analyses wereconducted on selected samples, with the aim of describing provenance and lithologies ofstrata in central Moresby Island, and particular attention was afforded anomalouslithologic occurrences. Specific structural objectives evolved as concurrent studiesilluminated different aspects of the tectonic history of the Queen Charlotte Islands, andare discussed in detail in chapter 3.Preliminary products of this investigation include four Geological Survey ofCanada Current Research Papers (Taite, 1990a, 1991a, Gamba et al., 1990; Haggart etal., 1991) which examined different aspects of the geology of central Moresby Island andthe Queen Charlotte Islands, and related conference presentations (Taite, 1990c, 1990d).The map produced for this thesis (Plate 1) is a component of the mapping conductedduring the Frontier Geoscience Program, and is published as a Geological Survey ofCanada Open File Report (Taite, 1991b).Stratigraphy / Introduction^ 102 STRATIGRAPHY2.1^Introduction to the Stratigraphic HistoryStratigraphic studies within the Queen Charlotte Islands began with Richardson's(1873) examination of the coal-bearing strata in the Skidegate Inlet area. Since then,numerous studies have subsequently refined the understanding of Queen CharlotteIslands stratigraphy. Many geographic names within the Queen Charlotte Islands, suchas Dawson, Newcombe, Whiteaves, and Richardson, bear testament to the naturalscientists who undertook the initial reconnaissance work.The stratigraphic nomenclature used in the Queen Charlotte Islands has evolvedas successive biostratigraphic and lithostratigraphic studies were completed, and thesynthesis of the modern stratigraphic column is largely the result of detailedbiostratigraphic control. Evolution of stratigraphic nomenclature up to the inception ofthe Frontier Geoscience Program is well described by Woodsworth and Tercier (1991).The stratigraphic sequence, as understood at the initiation of this project, is illustrated infigure 2.1. Details of the stratigraphic scheme continue to improve as biostratigraphicstudies progress (Jakobs, Pally, Smith, Tipper, Haggart, personal communications,1991). Whereas the Triassic —Lower Jurassic nomenclature seems relatively stable(Woodsworth and Tercier, 1991), the nomenclature for both the Middle Jurassic and theCretaceous strata is in a state of flux (i.e. Haggart et. al., 1991; Hesthammer, 1991, Taite,1990d). Recent developments in the understanding of these divisions will be discussed inthis chapter.Recent workers in the Queen Charlotte Islands have informally divided thestratigraphic succession into four unconformity bound sequences — a device whichfacilitates the understanding and description of the sedimentological, igneous, andStratigraphy / Introduction^ 11tectonic history (Thompson et. al, 1991; Lewis and Ross 1991; Taite, 1991a), and whichis employed in this study. Strata belonging to these four sequences exposed in the centralMoresby Island region range in age from Late Triassic through Tertiary (Figure 2.2).The lowest succession includes Upper Triassic volcanic rocks of the KarmutsenFormation and Upper Triassic to Lower Jurassic sedimentary rocks of the Kunga Group(comprising the Sadler Limestone and Peril and Sandilands formations), and ischaracteristic of Wrangellian successions (Jones et al., 1977). It is unconformablyoverlain by volcanic and sedimentary rocks of the Middle Jurassic (Bajocian) YakounGroup. The Cretaceous clastic rocks of the Longarm Formation and Queen CharlotteGroup (including the Haida, Skidegate, and Honna formations) comprise the thirdsuccession, and the fourth succession includes volcanic rocks of Tertiary age.Several units which are present in the Queen Charlotte Islands, and are wellexposed on northern Moresby Island and Graham Island, do not occur in the centralMoresby Island study area. Late Paleozoic sedimentary rocks, recently identified onnorthwest Moresby Island (Hesthammer et. al., 1991) do not crop out in the centralMoresby Island region, but likely underlie all of the Queen Charlotte Islands. The Lowerto Middle Jurassic Maude Group, a sequence of clastic marine sedimentary rocks whichconformably overlies the Kunga Group, and the upper Middle Jurassic Moresby Groupsedimentary strata are also absent in the study area. In addition, the upper age limit ofthe Queen Charlotte Group rocks exposed in central Moresby Island has not beendetermined; newly identified unnamed sedimentary and volcanic strata of UpperCretaceous age have been recognized on Graham Island (Haggart et al., 1990) but not incentral Moresby Island. Finally, Tertiary sedimentary rocks of the Skonun Formationcrop out only in central and northeastern Graham Island.Two suites of intrusive rocks occur in central Moresby Island. The Middle toLate Jurassic plutonic rocks of the San Christoval plutonic suite crop out extensivelyStratigraphy / Introduction^ 12southeast of the study area (Figure 1.2), where they form the San Christoval MountainRange. In the study area, small intrusive bodies related to this suite intrude Kunga Grouplithologies east of Newcombe Inlet and Wilson Bay. The second suite of intrusive rocksis Tertiary in age and is locally volumetrically significant. In outcrops east of WilsonBay and south of Sewell Inlet, they form up to 80% of the rock exposed. They comprisean extensive suite of compositionally heterogeneous dykes, sills, and irregular bodies,and were likely feeders for extensive Tertiary volcanism (Souther, 1988, 1989; Southerand Jessop, 1991)This chapter summarizes the present understanding of the stratigraphic unitspresent in central Moresby Island. It includes both observations made in the centralMoresby Island area as part of the present study, and where necessary for completeness,summaries of lithologic descriptions from elsewhere in the Queen Charlotte Islands.Descriptions pertaining directly to the central Moresby Island study area are products ofthis investigation exclusively, while those of other workers are referenced accordingly.Some of the stratigraphic analyses completed in this study, particularly those involvingthe Cretaceous succession, have formed components of previously published discussions(Gamba et al., 1990; Haggart et al., 1991; Taite, 1990a; 1991a).Stratigraphy / Introduction^ 13CH RONOSTRATIGRAPHICUNITSTRATIGRAPHICHISTORYaNI0L.,ui- `-`0E,1.65.323.736.657.866.474.584.087.588.59197.5113119124131138144152156163169 176183187193198204208225230 235240245PLEISTOCENE<F-GCLI..1I—PLIOCENE ...,"---.'-- SKONLINFORMATIONMIOCENE MASSET FM.^..----------u,.OLIGOCENEUNNAMEDVOLCANICROCKSROCKS..........„/EDIUMNENNATMAREYDEOCENEPALEOCENEH111 I1IIII1II111111111111111111111111111111111M1liiilOONIC)v)w00LLI0<I--LLCCoLL,MAASTRICHTIANr0_JCC  O<i (;)(") tX0Zuju. ,D0UNNAMED SEDIMENTARY ROCKSCAMPANIANSANTONIANCONIACIAN UNNAMED VOLCANIC ROCKSHONNA FORMATIONTURONIANSKIDEGATEFORMATION._._ s--HAIDAFORMATIONCENOMANAINwo-,ALBIAN APTIANFORMATIONLONGARMBARREMIANHAUTERIVIANVALANGINIANBERRIASIANU,—cn<D---)wLda.a_DTITHONIANKIMMERIDGANOXFORDIANLu0°CALLOVIANMORESBY GROUPBATHONIANYAKOUN GROUPBAJOCIANM111i JIIIIIIIII11111111111MIIIIIIMI11111111111111111HilAALENIANLL.1 0_0 D 0< CC> 0PHANTOM CREEK FORMATIONcew0_■TOARCIAN WHITEAVES FORMATIONFANNIN FORMATIONPLIENSBACHIANGHOST CREEK FORMATIONSINEMURIAN< 0_0Z 0D G!Y 0SANDILANDS FORMATIONHETTANGIAN0Cf)<DCI-NORIAN PERIL FORMATIONSADLER LIMESTONECARNIAN KARMUTSEN FORMATIONLADINIAN(./) ANISIANSPATHIANSMITHIANOIENERIANGRIESBACHIANFigure 2.1: Stratigraphic column outlining ages and contact relationships of the majormappable units of the Queen Charlotte Islands, modified from. Lewis and Ross ( 1991).Stratigraphy / Introduction^ 14CHRONOSTRATIGRAPHICUNITSTRATIGRAPHICHISTORYc.)0Zw0i -o,c,K,1.65.323.736.657.866.474.584.087.588.59197.5113119124131138144152156163169176183187193198204208225230235240245PLEISTOCENEcE).-<r--CYLI-IF—Z'' 'wPLIOCENEMASS ET FORMATIONORUNNAMEDVOLCANICROCKSMIOCENE,43.0.OLIGOCENEEOCENEPALEOCENE05NJ0u)LiCl)=0W0<I—Ldor)wo_a-MAASTRICHTIANCAMPANIANSANTON IANCONIACIANLloz _In-w ce D,-.-■ a oD 1 CC0 U 0HON NA FORMATIONSKIDEGATEFORMATIONTURON IANFORMATIONHAIDACENOMANAINctL'-'3owALBIANLONGARMFORMATIONAPTIANBAR REM IANHAUTERIVIANVALANGINIANB ER R IAS IAN0(I)Cl)<ecc,wa_a_0TITHON IANKIM MERIDGIANOXFORDIANIfioc)a-CALLOVIANBATHONIANBAJOCIAN YAKOUN GROUP_ ,AALEN IANtc,30TOARC IANPLIENSBACHIANSINEMURIAN< 0-0 0z o0 oceSANDILANDS FORMATIONHETTANGIANU(7)V)<CY(-NORIANPERIL FORMATIONSADLER LIMESTONECARMAN KARMUTSEN FORMATIONLADINIANAN ISIANSPATH IANSMITH IANDIENERIANGRIESBACH IANFigure 2.2: Stratigraphic chart outlining ages and contact relationships of the mappableunits occurring in the central Moresby Island area, adapted from Lewis and Ross ( 1991).Stratigraphy / The Wrangellian succession^ 152.2^The Wrangellian succession: the Upper Triassic to lower Middle JurassicKarmutsen Formation and Kunga Group Dawson (1880) recognized the regional correlation between the Triassic andLower Jurassic volcanic and sedimentary rocks (now known as the Karmutsen Formationand the Kunga Group) of the Queen Charlotte Islands and coeval Vancouver series strataon Vancouver Island. These rocks are now all included within the Wrangelliansuccession (Coney et al., 1980), and indeed, this succession is characteristic ofWrangellia throughout the Cordillera: Jones et al. (1977) define the unifying Wrangelliancharacteristics as Upper Triassic basalts overlain by calcareous sedimentary rocks whosedeposition commenced during late Camian to Norian time. Both the KarmutsenFormation and the Kunga Group, along with the Maude Group and the Yakoun Group,were previously included in the Vancouver Group (Sutherland Brown, 1968), a term nowfallen from common usage (Cameron and Tipper, 1985).2.3.1 The Karmutsen FormationThe lowest unit exposed in the central Moresby Island region is the UpperTriassic Karmutsen Formation. Named by Gunning (1932) for its type location in theKarmutsen Range of northern Vancouver Island, this distinctive volcanic unit iswidespread throughout the Insular Belt. The Karmutsen Formation is best exposed incentral Moresby Island to the north and west of Newcombe Inlet, and to the northeast ofBarrier Bay. The lack of continuous outcrop in the study area, due to irregular exposureand structural complication, precludes the construction of a stratigraphic column for theKarmutsen Formation. The aggregate thickness of this unit is estimated by SutherlandBrown (1968) to exceed 4,200 metres.Stratigraphy / The Wrangellian succsssion^ 16The Karmutsen Formation comprises a suite of basaltic rocks of Late Triassic agethat accumulated in a subaqueous environment (Sutherland Brown, 1968). This unit iscommonly green to black in outcrop, often with a brown to rusty weathering rind.Sutherland Brown (1968, page 41) described several different lithologic types in thisunit, three of which have been identified in central Moresby Island: a massive flowlithology, pillow lavas and breccias, and a glomeroporphyry lithology. Figure 2.3 showsthe distribution of these lithologies in the map area; the lithotype shown on this diagramrepresents the dominant lithology in outcrop, but other lithotypes may be interlayered.The most common lithotype of the Karmutsen Formation exposed in centralMoresby Island is the massive flow lithology (Figure 2.4). Amygdule-rich layers oftendefine primary layering in outcrop, otherwise this unit is featureless. Pillow basalt andpillow breccia lithotypes occur northeast of Newcombe Inlet. Pillows range in size fromtens of centimetres to several metres; average pillows are approximately one metre inlength, and ellipsoidal. Pillow breccias consist of resistant pillow fragments in amonolithic matrix. The glomeroporphyry (colloquially the "star porphyry" of SutherlandBrown, 1968; p. 68) is the least common lithology in outcrop, and is defined by thepresence of radial clusters of plagioclase feldspar laths greater than one centimetre inlength. Sutherland Brown (1968) notes that this lithology occurs approximately 60-150metres below the top of the Karmutsen Formation elsewhere in the islands. A pervasivefoliation is locally developed in outcrop where the Karmutsen Formation occurs in faultzones, and is defined by the parallel preferred orientation of platy minerals (chlorite).All Karmutsen Formation samples show pervasive alteration in thin section. Theglomeroporphyry lithotype exhibits chlorite pseudomorphs partially replacing 0.5centimetre pyroxene phenocrysts (pigeonite). Two populations of feldspars exist —ticro E?.,.-70 ,`S •F:?-4 0132'0'0^1^2^3 kmMTn!GriTasu SoundKarrnutsen For motion distribution of lithologieskey — dominant lithology in outcropmassive flows, aplianitic to finelyporphyriticpillowed flows, pillows,Q...,,,212 and pillow breccias.„^1_,.,.,__.•^ylorner ophyrt, per pl tyt yStratigraphy / The Wrangellian succsssion^ 18larger (1-2 centimetre) laths of oligoclase in radiating clusters, and a second generationof microphenocrysts (<0.5 millimetre), that along with chloritized pyroxene, form thematrix. Both plagioclase types have been altered to clays or sericite (Figure 2.5). Themassive, pillow flow, and breccia lithologies exhibit similar petrographic characteristics,with a single population of feldspar and chloritized pyroxene microphenocrysts formingsub-ophitic to intersertal texture.2.3.2 The Kunga GroupThe Kunga Group comprises three formations, the Upper Carnian to NorianSadler Limestone, the Norian Peril Formation, and the Norian to PliensbachianSandilands Formation. Estimates of stratigraphic thickness for the Kunga Group unitshave been attempted by Desrochers and Orchard (1991) with their disclaimer thatcomplete sections have been constructed from dismembered and fault-bound exposuresusing biostratigraphic markers for correlation. In addition, these units may vary widelyin thickness throughout their regional extent; the Sadler Formation ranges from 42 to 200metres in several different sections examined by Desrochers and Orchard (1991). ThePeril Formation is approximately 350 metres thick, and the Sandilands Formation has anestimated aggregate thickness of approximately 500 metres (Desrochers and Orchard,1991). Structural disruption and lack of biostratigraphic control thwarted attempts toestimate original stratigraphic thicknesses in the central Moresby Island area.Sadler LimestoneThe Sadler Limestone is a massive to thickly-bedded grey limestone of LateCarnian age, which conformably overlies the Karmutsen Formation. At its basal contact,thin grey limestone beds and lenses are interstratified with the top volcanic layers of theStratigraphy / Kunga Group^ 19Figure 2.4: Massive volcanic flows of the Karmutsen Formation, northwest ofNewcombe Inlet. This lithology is the dominant rock type in outcrop, and isdistinguished by its lack of stratification, pervasive alteration to chlorite, and itsirregular fracturing in outcrop.Figure 2.5: Photomicrograph of the glomeroporphyry lithology of the KarmutsenFormation illustrating subophitic intergrowth of plagioclase and pyroxene. Pyroxene ispartially altered to chlorite, and plagioclase is altered to clay minerals. Field of view isapproximately 4 mm left to right.Stratigraphy / Kunga Group^ 20Karmutsen Formation, representing the last pulses of Karmutsen volcanism and the onsetof carbonate sedimentation. Conodonts derived from these interbeds are also LateCarnian (Desrochers and Orchard, 1991). The Sadler Limestone comprises three distinctlithotypes: 1) lime mudstone to peloidal wackestone; 2) bioclastic wackestone topackstone; and 3) oolitic calcarenite (Desrochers and Orchard, 1991). The first lithotypeis common in the central Moresby Island region, the second occurs rarely, and the thirdlithotype was not observed.The lime mudstone is distinctive in outcrop; on hill slopes it exhibits aesthetickarst formation (Figure 2.6), whereas in shoreline exposures it weathers to sharpirregular peaks (dog-tooth weathering) several centimetres high. It is generally light greyon both fresh and weathered surfaces, except for rare rust coloured staining, or thickblack algal coatings which are ubiquitous on intertidal exposures. Bioclastic fragmentsinclude corals and crinoid fragments, which weather resistantly relative to the matrix, andare readily observable in outcrop. Thin sections reveal echinoderm, chert and crinoidfragments, and abundant sparry calcite cement. This unit has abundant styloliticsurfaces, usually parallel to bedding planes, with "teeth" reaching five centimetres(Figure 2.8). Pervasively developed veins are randomly oriented in outcrop, and arefilled with both fibrous and blocky calcite. This lithology often appears recrystallized inhandsample and thin section. Outcrops containing wollastonite are found southwest ofPacofi Bay (Figure 2.9).Peril FormationThe Peril Formation is characterized by thinly-bedded (3-15 centimetres thick)calcareous argillite layers (Figure 2.10). The age of this unit is Upper Carnian to UpperNorian on the basis of abundant Monotis coquinas and rare ammonites (Discotropites;Stratigraphy l Kunga Group^ 21Figure 2.6: Sadler Limestone shows typical karst weathering. Light grey weathering,rounded outcrops, extensive veining and massive character are all diagnostic of this unit.Field assistant is approximately 0.5 m tall.Figure 2.7: Bedding parallel stylolites in Sadler Limestone. Planar calcite veins areperpendicular to stylolites in this and other outcrops.Stratigraphy / Kunga Group^ 22Figure 2.8: Photomicrograph of the Sadler Limestone illustrating bioclastic echinodermfragments . Note the rounding of the carbonate clasts. Field of view is 4 mm left toright.Figure 2.9: Photomicrograph of Sadler Limestone illustrating radiating wollastonite (?)crystals. Wollastonite is uncommon and occurs in altered rocks adjacent to intrusions.Field of view is 4 mm left to right .Stratigraphy / Kunga Group^ 23Dr. E. T. Tozer, personal communication, 1991). The Sadler Limestone — PerilFormation contact is conformable and grades over several metres from thickly-bedded(<1 metre) grey limestones through successively thinner and more argillaceous beds(Figure 2.11). In outcrop, this unit is black, very fine grained, and thinly bedded, withrare white weathering silty to sandy layers. On wave cut benches, it occasionallyweathers recessively along bedding planes, leaving free standing 'plates' exposed.Desrochers and Orchard (1991) describe five lithofacies within the Perilformation: 1) radiolarian rich calcilutite — periplatform ooze; 2) laminated calcarenites— calciturbidites; 3) pelecypod coquinas (Monotis and Halobia) — pelagic limestone; 4)intraformational conglomerates; and 5) pelmatozoan calcarenites. Within the centralMoresby Island region, the most common lithofacies is the calcilutite interbedded withubiquitous pelecypod coquinas — these coquinas are commonly diagnostic of the PerilFormation. Graded beds of the laminated calcarenites (calciturbidites) are rarelyobserved — the coarse clastic component in rare Bouma Ta-e and Ta-c sequencesconsists of silt-sized particles which weather as thin white bands in outcrop.Intraformational conglomerates were not observed in the central Moresby Island area.The pelmatozoan calcarenite occurs sparsely west of Newcombe Inlet, where it generallyforms 5 to 15 centimetre thick beds interbedded with calcilutites and pelecypod coquinas.In one outcrop, bedding in this unit is considerably thicker (>1 metre thick), and contain10 to 20 centimetre concretions (Figure 2.12). Thin section examination of this lithologyreveals calcareous bioclastic echinoid plate fragments, pelecypod valve fragments,monocrystalline quartz grains, and abundant plagioclase feldspar. The plagioclase occursas both angular single crystals, and as phenocrysts in rounded trachytic clasts (Figure2.13).Stratigraphy / Kunga Group^ 24Figure 2.10: Typical thinly-bedded calcareous argillite of the Peril Formation,northeast of Newcombe Inlet. .Figure 2.11: Gradational contact between Sadler Limestone (left) and Peril Formation,east side of Newcombe Inlet. Contact typically grades over two to five metres fromthickly-bedded grey limestone to thinly-bedded calcareous argillite.Stratigraphy / Kunga Group^ 25Figure 2.12: Pelmetazoan calcarenite lithology of the Peril Formation, Newcombe Inlet.This lithology is common in the study area as thin beds within the calcareous argillite,but only rarely is thickly bedded.Figure 2.13: Photomicrograph of Peril Formation showing bioclastic carbonatefragments and plagioclase crystals. Field of view is 4 mm left to right.Stratigraphy / Kunga Group^ 26Sandilands FormationThe Sandilands Formation is the Norian to Sinemurian black argillite member ofthe Kunga Group which conformably overlies the Peril Formation. The contact isgradational and is arbitrarily drawn by Desrochers and Orchard (1991) at the highestMonotis-bearing horizon. This level also corresponds to the first appearances ofcolourful green, white, buff, and grey tuffaceous layers. The dominant lithology in theSandilands Formation is thinly-bedded siliceous siltstone and tuffaceous shale. This unithas not been subdivided into other lithologic members, but several distinctive lithotypesoccur in central Moresby Island. Massive sandstones are noted at the base of theformation on Graham Island (Hesthammer, 1991) and occur west of Newcombe Inlet incentral Moresby Island, where massive greywacke layers greater than ten metres thickcrop out (Taite, 1990a). The most common lithology in central Moresby Island, and inthe Queen Charlotte Islands in general, is the thinly-bedded black argillite andinterbedded tuff (Figure 2.14).The Sandilands Formation is commonly intensely folded and faulted in outcrop.It has a distinctive banded appearance, which is accentuated in intertidal exposures. Thisunit is well indurated, but has good bedding plane fissility. It fractures into angularblocks on joint sets oriented perpendicular to bedding. In the sandy to silty layers, finingupwards sequences are often present. Euhedral pyrite cubes and clusters of framboidalpyrite are distributed throughout the unit. Near fault zones, and zones of abundantintrusions, the Sandilands Formation appears as bleached green and white bands, seen inthin section as pervasive silicification, or less commonly as carbonate replacing quartz.In these hydrothermally altered exposures, all bedding plane fissility is lost.Stratigraphy / Kunga Group^ 27Figure 2.14: Typical thinly-bedded argillites and tuffs of the Sandilands Formation westof Newcombe Inlet. Blocky fracturing and alternating light and dark banding isdiagnostic.Figure 2.15: Greywacke lithofacies of the Sandilands Formation, beds are one-halfmetre thick, east of Two Mountain Bay.Stratigraphy / Kunga Group^ 28The Sandilands Formation is highly fossiliferous, with abundant and diverseammonite faunas appearing throughout the section as bedding plane molds or casts.These faunas have been the subject of detailed examination (Palfy, 1991). Palfyidentified different species of Arnioceras, Paltechioceras, and Juraphyllites; the presenceof Paltechioceras indicates the uppermost Sinemurian stage is represented (Palfy, 1991).In thin section, the silty layers contain abundant trachytic volcanic rockfragments, which appear as altered plagioclase laths in a chloritic groundmass. Euhedralplagioclase laths are present and they have been partially to completely altered to clay.Rare chert fragments, and recrystallized quartz or calcified radiolarian spheres, andmono- and polycrystalline quartz grains are also present. The matrix is composed ofclays with variable birefringence, and authigenic chlorite, formed through the diagenesisof clays.Anomalous outcrops of bedded greywackes and lithic arenites have beenidentified in central Moresby Island. These rocks do not resemble the typical SandilandsFormation lithologies, but their age and stratigraphic position place them within themiddle part of that formation. They appear as thickly-bedded (on the metre scale),blocky, and conchoidally fractured siltstones and sandstones (Figure 2.15). Abundantfossils are found in this lithology, including ornamented gastropods, corals, belemnites,and rare three-dimensionally preserved ammonite casts. Fossils are all preservedrandomly throughout the rock volume, represent both shallow and deeper water forms,and do not occur as bedding plane 'prints', suggesting deposition was the result of masssediment movement.Thin sections of this facies show moderate to good sorting, with angular tosubangular clasts. Plagioclase (oligoclase) occurs in volcanic rock fragments, and aseuhedral laths. Mono- and polycrystalline quartz fragments are present, as are bioclasticStratigraphy / Kunga Group^ 29carbonate fragments. K-feldspar occurs as rare angular crystals. Matrix, and pore liningand filling authigenic chlorite is abundant. Iron carbonates, opaque minerals, andorganic matter are a minor constituent; organic matter is preserved along 'microstyllolitic'surfaces. There is a small detrital clay component to this unit, relative to typicalSandilands Formation units. Echinoderm fragments and shell fragments are foundcommonly in impersistent, discrete layers. The rocks in this lithofacies are classified aslithic wackes to lithic and bioclastic lithic arenites (Figure 2.16).2.3.3 Depositional EnvironmentsRocks of the Triassic to Middle Jurassic Karmutsen Formation accumulated in avariety of depositional environments. Geochemical data presented by Andrews andGodwin (1989) suggest the Karmutsen Formation basalts of Vancouver Island originatedin a back arc rift environment, and an analogous origin for the correlative units in theQueen Charlotte Islands is likely. Carbonate sedimentation of the Sadler Limestonecommenced in Late Carnian time (Desrochers and Orchard, 1991) on a widespreadvolcanic platform. During this time, open marine conditions prevailed, and shallowwater depth is consistent the lithologic characteristics and with supporting coral andcrinoid fauna. Desrochers and Orchard (1991) indicate depositional environmentsincluded sand shoals, which resulted in the oolitic calcarenite facies; this lithotype wasnot observed in central Moresby Island, and was likely local in extent. During the LateCamian, the rapidly rising sea level resulted in the deposition of deeper water slope tobasin carbonates. The presence of plagioclase crystals and trachytic volcanic rockfragments in the Peril Formation is indicative of a distal volcanic source during Camianto Norian time.Stratigraphy / Kunga Group^ 30Figure 2.16: Photomicrograph of Sandilands Formation greywacke lithofacies, withcurved gastropod shell fragment . Field of view is 4 mm left to right.Figure 2.16b: Photomicrograph of a quartz-rich layer within the Sandilands Formation.This lithology is only documented in the central Moresby Island area. Field of view is 4mm left to right.Stratigraphy / Kunga Group^ 31Carbonate sedimentation ended with the drowning of the carbonate platforms inthe Late Triassic to Early Jurassic, and terrigenous Sandilands Formation depositioncommenced. The distal turbidites were deposited in a largely euxinic basin; brief periodsof oxygenation are evidenced by rare Chondrites feeding traces (Palfy, 1991). Thepresence of the greywacke and lithic arenite facies in the central Moresby Island areindicative of a more proximal terrigenous influence; the faunal assemblage preserved,and the sorting and provenance of the clasts are independent lines of evidence supportingtransport in a fluid gravity flow. These sediments may have been deposited at the base ofa submarine canyon, where massive influxes of volcanic detritus would result in anunstable sediment source. Subsequent mass movement by fluid gravity flow wouldtransport both volcanogenic sediments and the shallower marine fauna into the basin. Asource for the volcanic detritus has not been demonstrated, but the coarser sands areindicative of deposition in a shallow marine near shore environment.Sandilands Formation deposition ended in Sinemurian to Pliensbachian time, anddeposition of the conformable units of the Maude Group commenced (Tipper et al.,1991). The Sandilands Formation - Maude Group contact is diachronous and spansSinemurian to Pliensbachian time (Palfy, 1991). The Maude Group is thought torepresent two successive transgressive-regressive episodes of deposition with a greaterterrigenous influence (Palfy 1991). The Maude Group has not been identified in centralMoresby Island, and the closest known occurrence is on the east coast of Louise Island(Jakobs, 1989). Whether this is the result of a depositional hiatus or of subsequenterosion of this unit is unclear; however, Jacobs (1990) notes the presence of localdepositional breaks at the Louise Island location, and hypothesizes a paleotopographichigh may have existed in the southern Queen Charlotte Islands at the time of MaudeGroup deposition (Tipper et al. 1991).Stratigraphy / Yakoun Group^ 322.4 Arc Volcanism: the Middle Jurassic (Bajocian) Yakoun GroupThe Yakoun Group is composed of predominantly pyroclastic andesitic rocks andderivative epiclastic sedimentary rocks. First described by Dawson (1880), this unit hasa complex history of stratigraphic and nomenclatural revision, which is outlined byWoodsworth and Tercier (1991). The latest work before the advent of the FrontierGeoscience Program mapping was that of Cameron and Tipper (1985), where the unitwas elevated to group status. The age of the unit is constrained by molluscan fauna toEarly Bajocian by Cameron and Tipper (1985), who treated the group as comprising twodistinct formations; the predominantly volcanic Richardson Bay Formation, and theelastic Graham Island Formation, based on stratigraphic sections within the centralGraham Island area.Initial Frontier Geoscience Program mapping brought into question thestratigraphic and regional significance of these formational divisions. As a result,mappers of the Frontier Geoscience Program individually devised their own stratigraphicschemes, based on the lithostratigaphy within their respective study areas (Haggart,1991b, Hesthammer, 1991a, 1991b). The thickness of the Yakoun Group varies widely,due to variations in both initial depositional thickness, and subsequent preservation.2.4.1 Yakoun Group rocks in central Moresby IslandWithin central Moresby Island, four lithostratigraphic divisions occur within theYakoun Group: 1) lapilli tuff and interstratified tuff and epiclastic sedimentary rocks, 2)debris flow and lahar deposits, 3) conglomerate and sandstone, and 4) shale and siltstone.No stratigraphic sequence for these divisions has been determined. Slight differencesexist between these arbitrarily assigned divisions, and those proposed in the newstratigraphic scheme by Hesthammer (1991) for central Graham Island. The shale andStratigraphy / Yakoun Group^ 33tuff lithologies are interstratified in the central Graham Island area, and were assigned toa single unit, whereas in the central Moresby Island, they are seldom associated.Conglomerates within central Moresby Island are not volumetrically significant, and arealways interbedded with sandstones; on central Graham Island these lithologies form asignificant facies on their own. In addition, the volcanic lithofacies of Hesthammer(1991) includes volcanic flows, which are not documented on central Moresby Island.Figure 2.17 illustrates the distribution of Yakoun Group lithotypes in central MoresbyIsland; the lithology shown is the one dominant in outcrop, but other lithologies mayoccur as minor components.Thin section analyses of Yakoun Group rocks reveal several characteristicscommon to all lithofacies. Trachytic volcanic rock fragments contain commonplagioclase phenocrysts altered to clay, and minor highly-altered mafic phenocrysts.Alteration products include abundant chlorite replacing mafic crystals, and chlorite in thematrix as a replacement product and a pore filling phase. Carbonate cement is commonto all lithofacies. Secondary pyrite and associated sulfide minerals with both framboidaland cubic habits are found in all lithofacies. In epiclastic sedimentary rocks, clasts arealmost exclusively volcanic rock fragments, with chlorite and other clays forming thematrix.Lapilli tuffs and interstratified sedimentary rocksThis lithofacies occurs in all outcrops of Yakoun Group rocks in the study area,and forms significant deposits northeast of Wilson Bay. There are two majorsubdivisions within this unit, an unstratified lapilli tuff, and interstratified tuff andsedimentarykey — dominant lithology in outcroplapilli tuff, stratified tuff, andderivative clastic sedimentary rocksYa Koun Groupdistribution of lithofaciesStratigraphy / Yakoun Group^ 35rock layers. Lapilli and tuffaceous ash range in size from less than one millimetre toseveral millimetres, discrete clasts are composed of accretionary lapilli formed ofagglutinated ash particles. Vesicular blocks up to ten centimetres across occur rarely(Figure 2.18). This unit exhibits a characteristic green colour on weathered surfaces withwhits calcite or zeolite (rare) interstitial cement. Interstratified lapilli tuff - sedimentaryrocks grade upwards through repeated sections of accretionary lapilli, sandstones,siltstones, and shales. All of the clasts in the sedimentary strata are derived fromsubjacent reworked tuffs. Sedimentary structures observed in this unit include crossbedding, planar laminated bedding, and ripples. Small (less than two centimetre), andrare ammonite casts are preserved in the shale interbeds, indicating marine conditions.Debris flows and laharsThe debris flow lithofacies is the most common facies preserved in north andnorthwest of Two Mountain Bay (Figure 2.19). It is characterized by eithercompositionally intermediate angular volcanic clasts within a monolithologic matrix, orby volcanic clasts and rare angular accidental clasts derived from the subjacentSandilands Formation in a muddy matrix. Clasts range from granule to boulder size.Most clasts are derived from the unstratified lapilli tuff facies, and lend the outcrops theircharacteristic green weathering colour. This facies is generally matrix supported,unstratified, and ungraded. Scour surfaces occur where this facies unconformablyoverlies the Sandilands Formation.Stratigraphy / Yakoun Group^ 36Figure 2.18a: Poorly sorted, weakly-stratified lapilli tuff lithology of the Yakoun Group,northeast of Two Mountain Bay. Yakoun Group lithology is olive green in freshexposures, rusty orange on weathered surfaces.Figure 2.18b: Photomicrograph of the lapilli tuff lithology of the Yakoun Group.Lapilli illustrated here are accretionary. Field of view is 4 mm left to right.Stratigraphy I Yakoun Group^ 37Figure 2.18c: Well bedded lapilli tuff and epiclastic sedimentary rocks east of TwoMountain Bay.Figure 2.18d: Close up photograph of lapilli tuff and epiclastic sedimentary rocklithology illustrating low angle cross bedding, west of Newcombe Inlet.Stratigraphy / Yakoun Group^ 38Figure 2.19: Debris flow lithology of the Yakoun Group comprises dominantlyhomogeneous volcanic clasts in light weathering matrix.Figure 2.19b: Photomicrograph of the debris flow lithology of the Yakoun Group.Muddy matrix surrounds clasts of trachytic volcanic fragments. Field of view is 4 mmleft to right. matrix.Stratigraphy / Yakoun Group^ 39Conglomerate and sandstoneThe conglomerate and sandstone facies comprises units bedded on the metrescale. Sandstones exhibit planar laminations, or contain rare ripple marks. Within theconglomerate rocks, clasts range to cobble size, are well rounded, and arecompositionally intermediate volcanic rocks (Figure 2.20). Thin section examinationreveals clasts which are compositionally similar to the other Yakoun Group volcanicfacies. The provenance for the clasts is local: trachytic rock fragments and reworkedfragments of lapilli tuff are the most abundant, with rare mud or mudstone clasts ofunknown origin (Sandilands Formation ?).Shale and siltstoneThe shale and siltstone facies comprises thick, homogeneous successions ofvirtually featureless rocks. Black on fresh surfaces, this friable unit often weathers arustier colour than the older Sandilands Formation, or the younger Cretaceous shales.Close inspection reveals rare thin beds of lapilli tuff with a muddy matrix gradingupward into siltstone. The presence of tuff layers allows the differentiation from theother black shale units. These tuffaceous layers do not have the banded appearancecharacteristic of the Sandilands Formation, and accretionary lapilli are visible. This unitis found mostly the east of Wilson Bay, with only rare outcrops occurring elsewhere. Nofossils were observed in this lithotype.2.4.2 Depositional environmentsRecreating the depositional environments extant during Yakoun Group volcanismis a subjective exercise, due to the paucity of continuous outcrops. It is surmised thatYakoun volcanic facies do not have regional lateral continuity, and facies are likelyrepetitive in the stratigraphic column, as new episodes of volcanism commenced. TheStratigraphy / Yakoun Group^ 40Figure 2.20: Cobble conglomerate lithology of the Yakoun Group incorporates clasts ofthe bedded lapilli tuff, west of Newcombe Inlet.Figure 2.21: Shale and siltstone lithology of the Yakoun Group east of Wilson Bay ,distinguished by rare layers of lapilli tuff interbedded with green-grey to dark grey shalesand silts.Stratigraphy / Yakoun Group^ 41unstratified lapilli tuffs, and stratified and interlayered tuffs and sedimentary rocks areinterpreted to have been deposited in subaerial and submarine environments, and theirpresence is suggestive of a landscape in which andesitic tuff cones rose out of shallowseas. Elsewhere in the Queen Charlotte Islands, marginal marine deltaic deposits andpossibly lacustrine deposits have been identified (Hesthammer, 1991 b) — theunfossiliferous shale and siltstone strata may belong to this environment. Conglomeratesindicate deposition in channels or shallow marine environments. Lahars unconformablyoverlying the Sandilands Formation indicate channel or valley deposits distal to theflanks of volcanoes. No contact relations are observed with units other than theSandilands Formation. The Yakoun Group overlies a varied topography, which cannotbe constrained due to unknown offsets on younger faults. This relationship mayconstrain the amount of uplift occurring post-Sinemurian, and pre-Bajocian.2.4.3 Jurassic Intrusive RocksTwo suites of Jurassic plutonic rocks crop out in the Queen Charlotte Islands, theSan Christoval plutonic suite (SCPS), and the Burnaby Island plutonic suite (BIPS).These rocks received extensive attention as part of the Frontier Geoscience Program(Anderson, 1988; Anderson and Greig, 1989; Anderson and Reichenbach, 1990, 1991),with the aims of establishing their character and estimating the effect intense plutonicactivity had on the thermal maturation of the potentially petroliferous strata. Plutonicrocks exposed in the southern part of the central Moresby Island study area are includedwithin the 172-171 Ma San Christoval plutonic suite (Anderson and Reichenbach, 1991),and represent the northern extent of the San Christoval Mountain Range (Figure 1.2).This suite comprises medium grained, foliated diorites and quartz diorites which arecharacterized by prismatic hornblende, and rare biotite (Anderson and Greig, 1989).Stratigraphy / Cretaceous succession^ 422.5 Cretaceous Marine succession Longarm Formation and the Queen CharlotteGroup 2.5.1 Cretaceous Stratigraphy IntroductionOriginal descriptions of Queen Charlotte Group lithologies date to Richardson(1873) who described three units: an upper shale and sandstone, a coarse conglomerate,and a lower shale containing coal and iron ores. Dawson (1880) added what is now thesandstone member of the Haida Formation, and mistakenly included agglomerates (nowYakoun Group) and sandstones (now Maude Group) due to difficulty distinguishinglithologies in the field. Clapp (1914) introduced the Image member, which containedJurassic and Lower Cretaceous volcanic rocks and basal conglomerates, and the Haida,the Skidegate, and Honna members of the Queen Charlotte Series. Sutherland Brown(1968) recognized the stratigraphic distinctions between the Middle Jurassic volcanicrocks, the Yakoun Group, and the unconformably overlying basal sandstone andconglomerate, for which he introduced the name Longarm Formation. The Haida,Skidegate, and Honna members were elevated to formational status in his newly definedQueen Charlotte Group, which comprised a Cretaceous marine succession of sandstone,shale, and conglomerate unconformably above the Longarm Formation. The temporalequivalency of parts of the Honna and Skidegate Formations was recognized, but heplaced the Skidegate Formation stratigraphically overlying the Honna Formation, anerroneous interpretation not corrected until Haggart (1987) re-examined macrofossilfaunas.Numerous on going stratigraphic and sedimentological studies of the Cretaceoussuccession have been undertaken as part of the Frontier Geoscience Program's effort toidentify and describe possible hydrocarbon reservoir lithologies (Fogarassy and Barnes,1988, 1991; Fogarassy, 1989; Haggart, 1989, 1991; Haggart et al., 1991; Higgs, 1988a,Stratigraphy / Cretaceous succession^ 431988b, 1989, 1990; Gamba et al. 1990; Haggart and Gamba, 1990; Indrelid, 1990).These workers have demonstrated that stratigraphic relationships within the Cretaceoussuccession are more complex than previously understood. Detailed biostratigraphiccontrol has allowed workers to recognize that complex facies relationships replicateidentical lithologies throughout the stratigraphic column, and lateral continuity of faciesis restricted (Gamba et al, 1990; Taite, 1991a; Haggart et al. 1991). As a result, thesimplistic layer cake stratigraphy interpreted before the Frontier Geoscience Programwork gave way to a revised and modern process-oriented stratigraphic scheme (seeHaggart et al., 1991 for preliminary discussion). Formational names within this newstratigraphic scheme have yet to be formalized. Therefore, this thesis utilizes theformation names for Cretaceous nomenclature as outlined by Sutherland Brown (1968),and as defined as they were understood at the onset of the Frontier Geoscience Programmapping (Woodsworth and Tercier, 1991). The relationship between the formalformations, retained during mapping by the author in the central Moresby Island region,and the revised and interim stratigraphy of Haggart et. al. (1991), is explained within thetext (sections 2.4.5 and 2.4.6). An explanation of the relationship between the formalstratigraphy and the revised stratigraphy is included to simplify comparisons withongoing and future studies of the Cretaceous section in the Queen Charlotte Islands.The known age range of the Cretaceous rocks in central Moresby Island extendsfrom the Hauterivian to the Turonian, but both younger and older Cretaceous strata haverecently been identified in the Cretaceous succession elsewhere in the Queen CharlotteIslands (Gamba, 1991; Haggart and Higgs, 1989). These older and younger strata arethought to be restricted to discrete sub-basins (Gamba, 1991), and therefore have notbeen included in this discussion.Stratigraphy / Cretaceous succession^ 442.5.2 The Longarm FormationThe Longarm Formation was originally proposed by Sutherland Brown (1968)for previously undescribed Valanginian to Barremian strata which unconformably overliea variety of lithologies, including the Triassic to Lower Jurassic Kunga Group and theLate Jurassic Burnaby Island plutonic suite intrusive rocks (Anderson and Greig, 1989).Haggart and Gamba (1990) describe six lithofacies within the Longarm Formation,which they relate to depositional environments:i) A basal transgressive lag deposit consists of poorly-sorted, angular torounded cobble conglomerate. This lithofacies contains fauna indicative of ashallow marine environment. It contains reworked beach deposits derived fromadjacent headlands. Haggart and Gamba (1990) suggest this lithology isindicative of a complex serrated coastline.ii) An interbedded conglomerate and sandstone lithofacies consists ofcross-stratified sandstone, siltstone, and conglomerate, including the black andwhite pebble conglomerate of Sutherland Brown (1968). These lithologies areconformably overlain by trough cross-stratified greywacke. This sequence isdiagnostic of shallow foreshore and storm reworked beach deposits and longshoremigrating megaripples.iii) The bioturbated sandstone lithofacies comprises swaley cross-stratifiedsilty fine-grained greywacke, siltstone, and shale, and contains both terrestrialorganic matter (tree trunks and plant debris) and marine fauna. This facies isindicative of a deeper shoreface environment, below fairweather wave base, butstill storm influenced.Stratigraphy / Cretaceous succession^ 45iv) The sandstone and siltstone storm deposit lithofacies, in general,abruptly overlies the bioturbated sandstone. These deposits are characterized byplanar tabular laminated sandstone, and siltstone overlain by densely bioturbatedmudstone, the cap of the storm deposits. This unit is indicative of rapid sedimentaccumulation.v) A laminated siltstone and mudstone lithofacies contains a basalintraclast pebble conglomerate overlain by horizontal to low-angle laminatedsandstone and siltstone, capped by heavily bioturbated mudstone. This unit isindicative of rapid sediment accumulation in a storm-dominated shelfenvironment.vi) The turbidite lithofacies is rarely seen but can obtain thicknesses oftwenty metres (Haggart and Gamba, 1990). This lithofacies exhibits the Tabcdivisions of Bouma with intraclasts near a scoured base, and represents submarinechannel and levee deposits.Within central Moresby Island, rocks of the Longarm Formation were notrecognized during the first season by the author (Taite, 1990a); map relationships and thevolcanic lithic component in the sedimentary rocks suggested outcroppings of these rocksinstead belonged to the Yakoun Group. They were correctly identified when thediagnostic and ubiquitous Inoceramid valves were identified as Hauterivian (Haggart,personal communication 1990; Appendix 1), and the higher relative maturity of thesandstones was noted.The southwesternmost exposure of Longarm Formation strata corresponds to thetransgressive lag-cobble conglomerate lithofacies of Haggart and Gamba (1990). Theunconformity is clearly exposed overlying both Yakoun Group lithologies and theSandilands Formation (Figure 2.21). Clasts within the basal sequence are typicallyStratigraphy / Cretaceous succession^ 46derived from the directly subjacent unit throughout the Queen Charlotte Islands. Wherethis lithology overlies sedimentary rocks of the Yakoun Group, it can be distinguished byits higher relative maturity, the complete absence of lapilli tuff, and the presence ofubiquitous Inoceramid valves and prisms.A laminated mudstone, siltstone, and sandstone facies occurs locally in thesoutheasternmost exposures of the Longarm Formation. Abundant sedimentarystructures, including slump folding, climbing ripples, convolute beds, and fining upwardsequences are present, and correspond most closely to the turbiditic lithofacies ofHaggart and Gamba (1990). Soft-sedimentary deformation structures also include clasticinjection dykes - indicative of material failure due to high pore pressure resulting fromrapid burial (Figure 2.22).The northwesternmost exposures of the Longarm Formation is a matrix-supportedboulder conglomerate which fines upward over tens of metres into trough cross-beddedmedium- to coarse-grained sandstones (Figure 2.23). The boulders, some greater thantwo metres in length, are rounded on all sides. This unit is thought to overlie the YakounGroup, based on the intermediate composition of most of the boulders and the inferredcontact relationship; the contact is not exposed. Abundant Inoceramid valves, somereaching greater than fifty centimetres in length, provide a Hauterivian age for theoutcrop (Figure 2.24). Oyster fragments are common in the interstices between theboulders, and are occasionally attached to the boulders. The matrix varies from a 'hash'of lithic fragments and shell shards to medium- to coarse- grained sandstones. WithinStratigraphy / Cretaceous succession^ 47Figure 2.22: Basal unconformity of the Longarm Formation truncating the SandilandsFormation. The conglomerate lithofacies of the Longarm Formation includes roundedvolcanic boulders and locally-derived angular shale clasts.Figure 2.23: Clastic injection dykes and breccias within the Longarm Formation,northeast of Two Mountain Bay.Stratigraphy / Cretaceous succession^ 48Figure 2.24: Longarm Formation boulder conglomerate overlain by bioclastic cross-bedded sandstones. This location south of Sewell Inlet contains oyster, inoceramid, andammonite fragments.Figure 2.25: Inoceramid mold in sandstone, from locality illustrated in figure 2:24.Stratigraphy / Cretaceous succession^ 49Figure 2.26 Ichnofossils (chondritres ?) from locality illustrated in figure 2:24.Figure 2.27: Close up photograph of the cross beds within the sandstone beds shown infigure 2:24. Light coloured fragments are oyster and inoceramid valve fragments.Stratigraphy / Cretaceous succession^ 50Figure 2.28: Photomicrograph of Longarm Formation pebble conglomerate. VRFfragment embayed in an inoceramid valve fragment illustrates a pressure solutioncontact, but no mesoscopic dissolution surfaces are visible.Figure 2.29: Clastic injection dykes and breccias within the Longarm Formation,northeast of Two Mountain Bay.Stratigraphy / Cretaceous succession^ 51the coarse and medium-grained sandstone cross beds, very large feeding tracesresembling Chondrites occur — the large size and the coarse elastic substrate areanomalous for Chondrites (Figure 2.25).Thin section microscopy of the Longarm Formation lithologies reveals that mostof the clasts within the basal lithologies are locally derived. Intermediate compositionvolcanic rock fragments, presumably derived from the underlying Yakoun Group, arefound in all thin sections. Plagioclase laths within the fragments are mostly tocompletely altered to clay. Abundant Inoceramid prisms, and rare oyster valvefragments also appear in thin section. Sedimentary rock fragments make up avolumetrically significant proportion of the rock volume, and most are apparentlyderived from the Sandilands Formation; however, chert and carbonate fragments are alsopresent, and are likely derived from strata older than the Sandilands Formation. Siltstoneclasts are occasionally deformed into pseudomatrix. Pressure solution features,especially sutured boundaries, are obvious in some thin sections (Figure 2.26). Calciteoccurs as pore filling cement in all samples, and even in those that are texturally the mostmature, visual porosity is nearly zero. The calcite could be precipitated from circulatingCO3 -rich water locally derived from the dissolution of the bioclastic fragments, anddissolution of carbonate is visible along grain boundaries in thin section. Disseminatedpyrite is found in all samples, and pore filling chlorite occurs at the expense of volcanicrock fragments and biotite; compaction has locally resulted in the kinking of biotitesheaves. Most of the sandstones are classified as greywackes.Stratigraphy / Cretaceous succession^ 522.5.3 The Queen Charlotte GroupThe Haida FormationThe Haida Formation is subdividable into two members, a basal sandstonemember, and a shale member. Further lithologic subdivisions have been suggested(Yagishita, 1985; Fogarassy and Barnes, 1988, 1991), but the regional utility of thesedivisions has not been demonstrated.The sandstone member is characterized by medium to fine grained, green to grey,cross-stratified sandstone. The tops of the sandstone beds are locally bioturbated(Haggart, 1991). Sutherland Brown estimated the thickness of the unit at 823 metres atthe type locality in Bearskin Bay in Skidegate Inlet (Figure 1.1). Haggart (1991)suggested that thickness is tectonically modified, and that the true thickness is closer to400 metres. The sandstone member of the Haida Formation has not been identified inthe central Moresby Island region.The shale member of the Haida Formation comprises a monotonous succession ofblack, silty shale containing abundant calcareous concretions with rare fine grainedsandstone interbeds. Within the central Moresby Island area, sandstone beds aretypically 1-2 metres thick, with thin, bioturbated shale and siltstone interbeds. Grit, orbioclastic shell fragment debris layers are occasionally interbedded. The compositethickness of this unit in Bearskin Bay is approximately 100 metres; the stratigraphicthickness for the unit in central Moresby Island is not known.The Skidegate FormationThe Skidegate Formation is a lithologically distinct unit in the Queen CharlotteIslands. It is defined by turbiditic sandstone, siltstone, and shale, and the presence ofStratigraphy / Cretaceous succession^ 53partial to complete Bouma sequences. Beds range in thickness from approximately onecentimetre to greater than one metre (rare) (Figure 2.27). In outcrop, these beds formrhythmic grey and black bands representing the sandstone and shale fractionsrespectively. Grading and cross-bedding are visible in many of the beds. Thin sectionanalysis of sandstone beds reveals poorly to moderately sorted, lithic wacke withsubangular to subrounded grains. Matrix in the sandstone fraction is composed ofdetrital and authigenic clay. Framework grains include chert, calcite, siltstone, andtrachytic volcanic rock fragments with partially to completely altered plagioclase laths.Fossil collections made from stratigraphically highest exposures of the SkidegateFormation near Sewell Inlet indicate an Early Turonian age.The Honna FormationThe Honna Formation comprises interlayered conglomerate and sandstonelithologies. In Cumshewa Inlet, Haggart (1991) estimates the thickness of this unit to beapproximately 200 metres; it is likely highly variable regionally. Feldspathic sandstoneforms thickly bedded to massive, occasionally cross-stratified intervals. The sandstonesare medium to well sorted, subangular to subrounded, and contain a variety of clasttypes, including plagioclase laths, trachytic volcanic rock fragments, chert,monocrystalline quartz, K-feldspar, and rare biotite and hornblende. The relativeproportion of chert in the Honna Formation is greater than that characterized byFogarassy (1989) in his studies north of the central Moresby Island study area,suggesting regional provenance variability.The conglomerate lithofacies is a clast supported, pebble to cobble conglomeratewith medium to poorly sorted, medium to coarse grained, subangular sandstone matrix.The cobble clasts exposed south of Sewell Inlet are imbricate, and indicate paleocurrentsStratigraphy / Cretaceous succession^ 54Figure 2.30a: Turbidites of the Skidegate Formation south of Sewell Inlet. Light bandsare siltstones and sandstones, dark bands are shale.Figure 2.30b: Close up photograph of turbiditic layering within the SkidegateFormation.Stratigraphy / Cretaceous succession^ 55Figure 2:31a: Wave cut bench of Honna Formation conglomerate and sandstone, southof Sewell Inlet.Figure 2.31b: Monotis-bearing clast of the Peril Formation within the HonnaFormation conglomerate, south of Sewell Inlet.Stratigraphy / Cretaceous succession^ 56from the northwest (Gamba et al., 1990). Clast types include rounded volcanic andgranitic cobbles, and rare angular bedded shale and siltstone blocks. Banded tuffaceousclasts of the Sandilands Formation and Monotis-bearing angular argillaceous clasts of thePeril Formation also occur (Figure 2.28).In central Moresby Island, stratigraphic relationships with the other QueenCharlotte Group units are ambiguous. Skidegate Formation turbidites occur interlayeredwithin Haida Formation shales, and locally thin Honna Formation conglomerate bedsinterfinger with turbidites of the Skidegate Formation (Taite, 1990a; Gamba et al., 1990;Figure 2.29). Differentiating these units at the megascopic level is often impractical.Paleocurrent measurements taken from the base of the Honna Formation south of SewellInlet reveal a strong northwestward trend. Paleocurrents from the underlying SkidegateFormation reveal a consistent southwestward trend, at right angles to the overlyingHonna Formation (Gamba et al, 1990; Appendix 3).2.5.4 Depositional EnvironmentsThe Longarm Formation and the Haida Formation sandstones represent the basalsequence in a widespread and diachronous fining-upward marine sequence. These richlyfossiliferous strata constrain the onset of the marine transgression in the Queen CharlotteIslands to the Valanginian. The coarse sandstones and conglomerate exposed in centralMoresby Island represent beach and shallow marine deposits, largely above fair weatherwave base. The swaley cross-bedded sandstones are suggestive of offshore sandbardeposits, and the abundant Inoceramid valves, oyster fragments, and Chondritesichnofacies are characteristic of shallow marine conditions. Haggart and Gamba (1990)suggest the Longarm Formation deposits formed in shelf and upperslope environments.In the Queen Charlotte Islands, these rocks are conformably overlain by siltstone andshale of the Haida Formation, representing a transition to a deeper water, and furtherStratigraphy / Cretaceous succession^ 57offshore environments. Interfingering relationships between shales and sandstones withgrit and shell fragment lag deposits are indications that sedimentation was influenced bystorm deposits.The Skidegate Formation turbidites are representative of a submarine fan setting.Soft-sediment deformational features, such as slump structures, and dewateringstructures, are indicative of rapid sedimentation. The Skidegate Formation is interpretedby Gamba et al. (1990), to represent overbank levee deposits formed in a submarine fanenvironment. Paleocurrent measurements collected from Skidegate Formation turbiditesin Sewell Inlet indicate a southwestward directed flow, in contrast to the northwestwarddirected channelized conglomerates in the overlying Honna Formation. Thisperpendicular relationship between channels and overbank levee deposits is characteristicof submarine fan complexes (Walker, 1989).The depositional environment in which the Honna Formation formed hasattracted more controversy than perhaps any other unit in the Queen Charlotte Islands.Various interpretations include deep water fan deltas formed in response to thrustfaulting (Higgs, 1990), and shallow water deposits formed in response to eustatic sealevel changes (Haggart, 1991). Up to the Turonian to Coniacian sedimentation, the olderQueen Charlotte Group formations and the Longarm Formation describe a macroscopicfining upward sequence consistent with deposition in a marine transgressive sequence.The appearance of the coarse elastic sandstone and conglomerate units of the HonnaFormation herald a different kind of deposition: the eastward-stepping marinetransgression is overprinted by aggressive, westward-directed progradation of fancomplexes. In part, the cause of the controversy can be explained by the differingstratigraphic relationships the Honna Formation exhibits with older units in the QueenCharlotte Islands. On central Graham Island, the base of the Honna Formation scoursinto the Haida and Skidegate formations, and unconformably overlies Jurassic YakounStratigraphy / Cretaceous succession^ 58Group lithologies on northeast Moresby Island (Fogarassy, 1989; Thompson and Lewis,map). Within central Moresby Island, sandstones and conglomerates of the HonnaFormation form thickly- to thinly-bedded, planar to irregular bodies, conformablyinterstratified with turbidites of the Skidegate Formation. These are representative ofchannelized conglomerates and overbank levee deposits in a submarine fan environment(Walker, 1984).The earliest age of Honna Formation deposition is uncertain due to poorbiostratigraphic control, however in central Moresby Island, the conformably underlyingand presumed genetically related Skidegate Formation turbidites (Gamba et al., 1990) areof early Turonian age (Haggart, 1991). Three hypothesis have been proposed for theimpetus for Honna Formation sedimentation. Haggart (1991) notes that the timing ofHonna Formation deposition coincides well with established eustatic sea level curvesshowing global sea level drops in Turonian to Coniacian time (Hancock and Kaufman,1979; Haq et al., 1987). Thompson et al. (1991) suggest late Cretaceous block-faultingmay have resulted in the formation of local fan complexes. Clasts derived from theSandilands and Peril Formations indicate there was a nearby source for Kunga Grouplithologies by Turonian to Coniacian time. A variation on this theme has been proposedby Higgs (1988a, 1990), who suggests Honna Formation deposition may reflect thesedimentary front of a westward migrating foreland thrust system. The merits of thesehypothesis will be further discussed in the regional synthesis section (chapter 5).2.5.5 Problems with Cretaceous nomenclatureThe need for revised Cretaceous nomenclature first arose when field workersfound the formal Cretaceous stratigraphic divisions were not universally applicable at theoutcrop, and could not easily be used in mapping exercises. Existing stratigraphicSHALESILTSTONEMaastrichtianCampanianSantonianConiacianTuronianCenomanianAlbianAptianBarremian(SKIDEGATE FM)TURBIDIDTESSHALESILTSTONESHALEHONNA FM.CONGLOMERATES0(r)>-cocf)(HAIDA FM)^C_JHauterivianValanginianBerriasian(LONGARM FM) ,\„„\Cc)>\9 PRE—CRETACEOUSROCKSStratigraphy / Cretaceous succession^ 59Figure 2:32: Schematic cross section of the Cretaceous succession in the QueenCharlotte Islands illustrating the idealized relationship between lithotypes, and thelocation of central Moresby Island.key — dominant lithology in outcropconglomerate with interbeddedturbiditic sandstone and shaleblack shale, often concretionarythinly interbedded turbiditicsandstone and shale0^1^2^3 km!Gd!SEn!li■IlTasu Sound132'0'44/ 4Queen Charlotte Group Longarm Formation distribution of lithologiesthick to massive sandstone withinterbedded shalesandstone, conglomerate, siltstone,and turbiditic shale with inoceramidOStratigraphy / Cretaceous succession^ 61schemes proved to be misleading for both recreating depositional environments, andinterpreting map patterns to evaluate post-Cretaceous tectonic activity. For example,Thompson and Lewis (1990a) interpreted a tectonically repeated section of Honnaconglomerate north of Sewell Inlet that is in fact a stratigraphic repetition (Taite, 1989),this type of repetition is also demonstrable on the mesoscopic scale in central MoresbyIsland. A revision of the nomenclature became even more compelling when Haggart(1991) demonstrated that the basal unit of the Cretaceous sequence was diachronousthrough Valanginian to Aptian time and represented a eustatically controlled marinetransgression — the previously inferred Aptian hiatus does not exist, and the LongarmFormation and the Queen Charlotte Group are demonstrably conformable. Depositionalenvironments reflecting a long lasting marine transgression are necessarily complex, anda representative stratigraphy would illustrate interrelated and interdependent facies inboth time and space.2.5.6 Generic StratigraphyTo circumvent the problems caused by the formal nomenclature, as outlinedabove, a generic stratigraphy was developed concurrent with the present study. Thisgeneric stratigraphy is included in this study to aid future workers in reconstructingCretaceous depositional models. This stratigraphic scheme divided the Cretaceoussuccession into mappable lithologic components, with no reference to chronostratigraphy(Haggart et al. 1991; figure 2.30). Three major lithologic units were defined: shallowwater sandstone, deeper water shale, and Honna Formation sandstones andconglomerates. These units were further subdivided: the Cretaceous sandstonelithofacies comprises sandstone, siltstone, and the basal transgressive conglomerates(including the Longarm Formation, and the Haida Formation sandstones), the Cretaceousshale lithofacies comprises black shale, and the turbiditic sandstone and shale (includingStratigraphy / Cretaceous succession^ 62the Haida Formation shale, and the Skidegate Formation). The Honna Formation isconsidered lithologically and genetically distinctive, and the name is retained. Haggart etal. (1991) hoped this scheme, when combined with available chronostratigraphic data,would allow the Cretaceous evolution and depositional environments of the QueenCharlotte Islands to be reconstructed. Figure 2.31 illustrates the position of theCretaceous stratigraphic column in central Moresby Island in a schematic illustration offacies relationships, and figure 2.32 illustrates the distribution of the Cretaceouslithofacies in central Moresby Island.The Honna Formation conglomerate lithofacies contains minor turbiditicsandstone and shale (Skidegate Formation). The dark grey to black shale lithofacies isthe shale member of the Haida Formation. The turbiditic sandstone and shale areequivalent to the Skidegate Formation. The interbedded thick to massive sandstone withturbiditic shale represents interbedded Skidegate Formation turbiditic sandstone andshale with Honna Formation sandstone and conglomerate - neither the formalnomenclature nor the interim stratigraphy of Haggart et al. (1991) have a division whichrepresents this lithotype. Finally, the basal transgressive lithofacies corresponds to theLongarm Formation in central Moresby Island.Stratigraphy / Tertiary succession^ 632,6 Tertiary Volcanism 2.6.1 History and NomenclatureTertiary volcanic rocks were first recognized in the Queen Charlotte Islands byClapp (1914), but received no detailed attention until Sutherland Brown's (1968) study.Sutherland Brown included all Tertiary volcanic rocks in the Masset Formation, whichhe subdivided into three facies based on lithologic character and age. The Tartu Facieswas defined as comprising two main rock types: dominant aphanitic to rare phenocrysticand microphenocrystic basalt with basalt breccias, and sodic rhyolites with feldspar andpyroxene phenocrysts. The Dana Facies comprised tuff breccias of mixed basalt andrhyolite clasts. The Kootenay facies comprised acidic, bedded pyroclastic rocks rangingfrom agglomerates to welded ashflows interlayered with foliated spherulitic rhyolites.Hickson (1988, 1989, 1991) further examined the Tertiary volcanic rocks, andrecognized two distinct assemblages: a Neogene unit, for which she retained the nameMasset Formation, and an older unnamed Paleogene suite. The Kootenay facies ofSutherland Brown (1968), which contains the felsic pyroclastic rocks and interbeddedrhyolites, lithologically corresponds to the Neogene Masset Formation. The MassetFormation is compositionally distinctive; it lacks large feldspar and hornblendephenocrysts in the felsic units, and lacks olivine phenocrysts (or normative olivine) inmafic units. The Dana and Tartu Facies of Sutherland Brown (1968) arecompositionally more heterogeneous, are commonly porphyritic with feldspar andamphibole phenocrysts, and are representative of the unnamed Paleogene suite. Thework of Hickson (1991) concentrated on rocks of the Masset Formation; the Paleogenesuite remains poorly understood.Stratigraphy / Tertiary succession^ 642.6.2 Tertiary Volcanic Rocks in central Moresby IslandTertiary volcanic rocks lie unconformably on all older lithologies in the centralMoresby Island area. The basal contact is not exposed, and no attempts at estimatingstratigraphic thickness were made. Rocks assigned to the Tertiary volcanic suites in thecentral Moresby Island comprise a wide range of lithologies. The subdivision of theTertiary rocks into two suites (Hickson, 1991) initially proved problematic to this fieldinvestigation; lithologies representative of both suites are apparently present. This studyproposes that both suites occur within central Moresby Island, based on lithologicdescriptions and thin section microscopy. The observations that suggested thishypothesis were made during laboratory investigations, and no attempt was made tocorrect mapping retroactively by differentiating the suites. A definitive determination ofthis hypothesis will require a more systematic survey of these rocks, includinggeochemical and geochronological analysis coupled with detailed facies analysis.The most abundant lithologies within the Tertiary volcanic rocks are debris flowswith subangular to subrounded heterolithic volcanic and accidental fragments (Figure2.33). Bedding surfaces are often discernable in the field, although no internalstratification is developed. Clasts of volcanic origin range from aphanitic to feldspar andhornblende phyric. Angular shale and mudstone accidental clasts locally form asignificant portion of some units. Clasts range in size from less than one centimetre toboulder-sized blocks. These rocks correspond lithologically and compositionally to thePaleogene assemblage. In thin section, this lithology reveals abundant secondary calcite,silica, authigenic chlorite, serpentine minerals replacing mafic phenocrysts, and finelydisseminated epidote (Figure 2.34). The wide range in commonly-found clast sizes, andthe heterolithic population of clasts including the abundant accidental clasts, both serveas useful field tools to distinguish these rocks from the mainly monolithologic debrisflows of the Yakoun Group.Stratigraphy / Tertiary succession^ 65Figure 2.34: Debris flows in Tertiary volcanic rocks, south of Lagoon Inlet., contact isnorth dipping.Figure 2.35: Tertiary debris flow south of Lagoon Inlet. Clasts include volcanicfragments, and angular argillites and sandstone blocks., .66Stratigraphy / Tertiary successionFigure 2.35a: Photomicrograph of Tertiary flow banded rhyollite of probable Neogeneage showing devitrification of glass . Field of view is 4 mm left to right._21111M11811•1111I'Milwar■- -nik 3LPflitNaMil -JR ^ ."-StFigure 2.35b: Photomicrograph of Tertiary debris flow lithology of probable Paleogeneage. Extensive alteration includes chlorite and serpentine group minerals. Field of viewis 4 mm left to right.Stratigraphy / Tertiary succession^ 67Another distinctive lithotype observed in the Tertiary volcanic rocks is thespherulitic rhyolite, which corresponds lithologically to the Neogene Masset Formation(Hickson, 1991). These rocks appear bright white to greenish-white in outcrop,spherulites are one to three millimetres in diameter, and flow banding is observable on asub-centimetre scale. In thin section, devitrification features are not observed, insteadthese rocks are characterized by pervasive recrystallization of the groundmass, consistentwith local hydrothermal alteration, to the extent that primary igneous textures arecompletely obscured (Figure 2.35).Vein, fracture, and joint sets are abundant in both the Paleogene and the Neogenesuites and orientations are not regionally consistent. Calcite and quartz both form veinfilling phases, and epidote veins occur within Paleogene lithologies. Thin sectionanalyses of the Tertiary volcanic rocks emphasizes the pervasive alteration in centralMoresby Island. The most interesting result obtained from examination of thin sectionsis that two apparent degrees of alteration exist, a lower greenschist-grade metamorphismof the Paleogene succession, and hydrothermal alteration, characteristic of alterationproximal to volcanic vents of Neogene lithologies. While this apparent disparity ofalteration levels is not, in itself, sufficient to categorize volcanic suites, it does supportthe hypothesis of two episodes of Tertiary volcanism.2.6.3 Tertiary Intrusive Rocks in central Moresby IslandTertiary intrusive rocks in the Queen Charlotte Islands include plutonic bodies ofthe Kano Plutonic suite (Anderson and Reichenbach, 1991), and regionally abundantdykes (Souther and Jessop, 1991). Dykes and plutons of the Kano Plutonic suite havebeen identified in the central Moresby Island area. Both dykes and plutons are spatiallyassociated with the greatest accumulations of Tertiary volcanic rocks, and are consideredcogenetic. Dykes of the Queen Charlotte Islands were studied in detail as part of theStratigraphy / Tertiary succession^ 68Frontier Geoscience Program, in order to estimate the influence of intrusive bodies onthe thermal maturation of potential hydrocarbon source rocks (Souther and Bakker, 1988;Souther 1988, 1989; Souther and Jessop, 1991). Two distinct populations of dykes occurwithin the central Moresby Island study area: the Tasu swarm, and the Selwyn Inletswarm. These swarms are defined by differing orientations (Souther and Bakker, 1988;Souther and Jessop, 1991). Dykes of the Tasu swarm, situated most commonly north andeast of Tasu Sound, dominantly trend northerly, and are basaltic to rhyolitic incomposition. The Selwyn Inlet swarm extends from Sewell Inlet south to TalunkwanIsland, and dykes within it have a predominantly easterly trend in contrast to all otherswarms on Moresby Island. They also range compositionally from basaltic to rhyolitic.Tertiary intrusions can generally be distinguished from Jurassic intrusions because ofcomposition range and amount of deformation. Jurassic intrusions are intermediate incomposition, and dykes are occasionally folded.2.6.4 Depositional EnvironmentMapping and dating of Tertiary volcanic rocks suggests there may have beenmany phases of Tertiary volcanism on the Queen Charlotte Islands (Hickson, 1991).Thickest accumulations of rocks correspond spatially to areas of most intense intrusiveactivity. Souther (1988) suggests original accumulations of volcanic rocks may havebeen restricted to these areas, and present accumulations may correspond to originalaccumulations around discrete centers. The Paleogene suite was subject to conditionssufficient for metamorphism to lower greenschist grade. Minimum temperaturesrequired for this are greater than 3750 - 4000C (Winkler, 1979).It is not known if the Neogene Masset Formation rocks were depositedconformably on the Paleogene volcanic rocks. The outcrops which contain thehydrothermally altered rocks occur spatially close to those of greenschist metamorphicgrade. This could be the result of erosion of the metamorphosed Paleogene strata beforeStratigraphy / Tertiary succession^ 69the onset of Masset volcanism, or it could reflect subsequent structural complicationsjuxtaposing different grades of Tertiary rocks during Tertiary tectonism; evidence forTertiary tectonism will be discussed in Chapter 4.Structural Geology / Introduction^ 703 STRUCTURAL GEOLOGY OF CENTRAL MORESBY ISLAND3.1 Introduction, previous work and the evolution of objectives:As with the stratigraphic studies, early observations pertaining to the structuralevolution of the Queen Charlotte Islands date back to the pioneering work done early onthis century, and late in the last (Dawson, 1880; Clapp, 1914). It is humbling to seemany of the earliest observations these first workers made on the structural evolution ofthe islands vindicated by their contemporary counterparts (Lewis and Ross, 1991;Thompson et. al., 1991, and others). Dawson recognized a chronology of tectonic eventsin the Queen Charlotte Islands which included a post Triassic "period of disruption", aperiod of great volcanic activity synchronous to Yakoun Group deposition, succeeded byquiescent sedimentary deposition (the Cretaceous section), and a final post-Cretaceouspre-early Tertiary "period of disruption". Clapp (1914) recognized the uplift and erosionmarked by the pre-Yakoun Group unconformity.The synthesis of tectonic history by Sutherland Brown (1968) marked the firstdetailed and regional synthesis of the Queen Charlotte Islands. He believed that faultingand crustal fractures were the dominant tectonic influence on the evolution of the QueenCharlotte Islands, and major regional scale fault systems controlled the distribution of thestratified units, as well as the emplacement of intrusive units. These major fault systemsincluded the Renell Sound - Louscoone Inlet fault systems, and the Sandspit Fault. Thetiming of movement and the offset history on these fault systems is poorly constrained,but Sutherland Brown (1968) hypothesized these faults had a complex history couplingpredominantly dextral strike slip movement with subsidence of the eastern block. Hesurmised the Rennell Sound fault zone - Louscoone Inlet fault system was likely active inEarly Cretaceous or possibly Late Jurassic time, again in the late Tertiary, and possibly inrecent time. The Sandspit fault is less well exposed, and thus less well constrained.Structural Geology / Introduction^ 71Sutherland Brown (1968) suggests it was active in the Cretaceous, and again in the post-Pleistocene.Sutherland Brown (1968) considered folds to be mainly secondary features in theQueen Charlotte Islands, and suggested that they are confined to localized zones. Herecognized four ages of fold systems, Triassic-Jurassic, Cretaceous, early Tertiary, andlate Tertiary. He speculated that some folds formed in response to fault blockmovement, while others formed without any obvious relation to faults.No additional field research aimed at constraining the tectonic evolution of theQueen Charlotte Islands was conducted between Sutherland Brown's 1968 work and theonset of Frontier Geoscience Program research. However, interim studies employedSutherland Brown's tectonic interpretations to synthesize the evolution of the QueenCharlotte Islands and, in particular, the Tertiary Queen Charlotte Basin. Yorath andChase (1981), and Yorath and Hyndman (1983) considered the Louscoone Inlet and theSandspit fault systems to be remnants of a single dextral strike slip fault that had beenoffset by the dextral Rennell Sound fault zone in Tertiary time.The next significant field research into the tectonic evolution of the QueenCharlotte Islands came with the onset of the Frontier Geoscience Program in 1987(Figure 1.3). Thompson et al. (1991) outline the state of knowledge as understood at theend of the 1988 field season. Frontier Geoscience Program workers in northern MoresbyIsland and central Graham Island recognized four major tectonic events of regionalsignificance. The earliest recognizable event is a southwest-directed shortening event ofAalenian to Bajocian age, and is characterized by northwest-trending contractional foldsand faults (Lewis, 1991b; Lewis et al, 1991; Lewis and Ross, 1988a, 1988b, 1991;Thompson et al., 1991). The Late Jurassic to Cretaceous was characterized bywidespread block faulting, which controlled the preservation of Middle Jurassic andStructural Geology / Introduction^ 72Cretaceous strata (Thompson et al., 1991). A second, northeast-directed contractionaldeformation event occurred in Late Cretaceous to Tertiary time (Lewis, 1991 b;Thompson et al., 1991). Tertiary block faulting post-dated deposition of the Massetvolcanic rocks. Subsequent research was able to constrain a complex Tertiary tectonichistory. Lewis (1990) was able to delineate four distinct deformation events of unknownregional significance affecting newly identified Paleogene strata in Long Inlet: (1) LateCretaceous to early Tertiary shortening; (2) early Tertiary extensional faulting; (3) mid-Tertiary shortening; and (4) late Tertiary to Holocene extensional faulting.Frontier Geoscience Program workers also established a rough chronology for thetiming of deformation of the major tectonic elements in the Queen Charlotte Islands.The Long Inlet Deformation Zone (LIDZ), a northwest-trending belt of folds and faultsextending over northern Moresby and Graham islands (roughly coincident with theRennell Sound fault zone of Sutherland Brown, 1968; Figure 1.2), was active inCretaceous and Tertiary time (Lewis, 1991b). Stratigraphic contacts proved mappablewithout offset across this zone (Thompson 1988b), and thus this fault zone was insteadrecognized as an intense zone of northeast- and southwest-directed compressionaldeformation and extensional block faults, with little or no strike slip offset. Lewis(1991 b), hypothesizes that deformation within this zone reflects reactivation of basementstructures. It was informally renamed the Rennell Sound fold belt by Thompson andThorkelson (1989) and later the Long Inlet deformation zone by Lewis (1991b; Figure1.2).An additional observation made arising from field mapping during the first twoyears of the Frontier Geoscience Program was that discreet fault-bound blocks in theislands preserve different stratigraphic successions. The proposed explanation for thisobservation is that a multiple movement history on block-bounding faults alternately ledto preservation and erosion of the sedimentary strata (Thompson and Thorkelson, 1989;Structural Geology / Introduction^ 73Thompson et. al., 1991). Clearly, understanding the mechanisms which resulted invariable preservation of potential source and/or reservoir strata is paramount for thedevelopment of a hydrocarbon exploration model.Initial reconnaissance work in central Moresby Island was initiated by SutherlandBrown and Jeffery (1960), and was elaborated upon by Sutherland Brown (1968). Sincethen, most regional geologic and structural studies in the Queen Charlotte Islands haveconcentrated on Graham Island and northern Moresby Island. This work represents thefirst significant detailed study of the geology of central Moresby Island.Ongoing studies by Frontier Geoscience Program workers immediately precedingand concurrent with this study helped define this study's objectives. Because of the rapidsynthesis of geologic ideas by FGP workers within the time period of this study, initialobjectives occasionally lost emphasis, and subsequent areas of inquiry were madeobvious. This section discusses the evolution of objectives for the structuralinvestigations of this study. The initial objectives of the study, firstly to document thestructural characteristics of central Moresby Island, and secondly to test the regionalapplicability of tectonic models developed by Frontier Geoscience Program workers,remained unchanged throughout the duration.During the 1989 field season, R.I. Thompson of the Geological Survey of Canadamapped an area including Louise Island and the mouth of Sewell Inlet (Thompson andThorkelson, 1989; Thompson and Lewis, 1990a, 1990b). He noted both anomaloustrends for major structures, and anomalous amounts of deformation in Cretaceous stratarelative to structural styles documented on northern Moresby Island and central GrahamIsland (R.I. Thompson, personal communication, 1989). While elsewhere in the QueenCharlotte Islands structures in Cretaceous strata trend northwest, coaxial with the MiddleJurassic deformation, in Cretaceous strata at Sewell Inlet, northeast-trending structuresStructural Geology / Introduction^ 74dominate (Thompson and Lewis, 1990a; Sutherland Brown, 1968). The additional goalof ascertaining the significance of the northeast-trending structures was defined.Thompson and Thorkelson (1989) describe a post-Cretaceous block faulting eventwhich controlled the preservation of Cretaceous strata on northern Moresby Island andcentral Graham Island. Faunal evidence in Cretaceous strata of northern Moresby Islandsuggested the presence of an additional "post Haida Formation - pre Honna Formation"deformation event (Thompson et al., 1991). The Cretaceous strata around Sewell Inletproved to be a possible testing ground for both the regional significance of the LateCretaceous block faulting event, and the possibility of a syn-Cretaceous deformationevent.Subsequent re-examination of faunal collections from northern Moresby Island,which provided the initial evidence for syn-Cretaceous tectonic activity, suggested pre-Honna Formation faulting was not well supported, (J. W. Haggart, personalcommunication, 1990). The poor exposure and extensive disruption of the Cretaceousstrata in central Moresby Island, combined with the lack of stratigraphic orbiostratigraphic markers, resulted in the objective of testing possible syn-Cretaceoustectonism losing relative importance.The second field season conducted in central Moresby Island for this study wasconcurrent with a project initiated along the Louscoone Inlet fault system in the southernQueen Charlotte Islands (Lewis, 1991a). Lewis documented structural stylesfundamentally different from those on central Graham Island. The southwest-directedshortening event apparently did not extend into the southern islands. Instead, a zone ofintense north-striking, dextral faulting (the Louscoone Inlet Fault) separated a 'rigid'block to the west from an extended half-graben style region to the east. This wasinterpreted to be related to Tertiary tectonic activity, synchronous with the formation ofStructural Geology / Introduction^ 75the Tertiary Queen Charlotte Basin (Lewis, 1991a). Central Moresby Island represents astructural transition zone between regions dominated by the southwest-directedshortening event, such as central Graham Island, and regions which displayed dominantlyTertiary wrench fault features, such as Burnaby Island and southern Moresby Island. Anadditional objective for this study was formulated: to determine the relative influence ofthe different tectonic styles documented on central Graham Island and the southernQueen Charlotte Islands to the structural development of central Moresby Island.3.2 Structure of the central Moresby Island areaMegascopic structures in central Moresby Island are dominated by north- andnortheast-striking faults. Northwest-trending folds and northwest-striking faults areobservable as both mesoscopic and megascopic features. Mesoscopic folds and faultsextensively disrupt bedding locally, and as a result bedding measurements in outcrop aredifficult to use to outline megascopic structures. Unequivocal offset markers arenonexistent in central Moresby Island for major faults: offset histories have occasionallybeen constructed from extrapolation of movement histories of geometrically similarfaults observed in outcrop. Major structural features are inferred from outcropdistribution, except for rare occurrences where they can be observed directly.Confidence levels for contact relationships in central Moresby Island are, of course,directly proportional to outcrop density. The space between outcrops ranges from tens ofmetres in recently logged areas, to hundreds of metres. Minor faults are ubiquitous in alllithologies, megascopic structures are only interpreted when they best explain outcropdistribution. Strain accommodation in central Moresby Island is very inhomogeneous —areas of intense deformation alternate abruptly with relatively undeformed strata, andareas of intense strain often coincide with volumetrically significant intrusions whichboth alter the lithologic characteristics of host strata and obscure mesoscopic structures.Structural Geology / Introduction^ 763.3 Structural Domains in central Moresby IslandCentral Moresby Island is divided into three mainly fault-bound domains(western, central, and eastern), which are defined by the internal preserved stratigraphicsuccessions (Plate 1). The western and eastern domains are characterized by rocks of theTriassic and Jurassic Karmutsen Formation and Kunga and Yakoun groups, allunconformably overlain by Tertiary volcanic rocks. The central domain containsCretaceous rocks unconformably overlain by Tertiary volcanic rocks. The Cretaceousand the Tertiary strata unconformably overlie the Jurassic Sandilands Formation andYakoun Group at the mouth of Sewell Inlet and in the southern region.3.4 Domain BoundariesDomain boundaries are generally defined by faults or inferred fault systems, someof which are informally named (Plate 1). Tectonic activity on these faults is thought tohave resulted in differential preservation of the stratigraphic sequence within eachdomain. The boundary separating the western and central domains is defined by theinferred north-striking fault or system of faults (the Crazy Creek Fault, Plate 1) whichseparates Tertiary volcanic rocks unconformably overlying Triassic and Jurassic strata tothe west from the area containing Tertiary volcanic rocks overlying Cretaceouslithologies to the east. This fault zone is obscured along its northern extent by Tertiaryvolcanic rocks, and contact relationships do not indicate whether this fault cuts the baseof the Tertiary volcanic rocks or is restricted to pre-Tertiary strata.The northern boundary between the central and eastern domains is defined alongnortheast- and north-striking, steeply-dipping faults which separate Cretaceous strata tothe north from Tertiary strata to the south. The position of the western edge of theeastern domain is the north-striking Boundary Fault which can be constrained along itssouthern extent, where it separates Cretaceous Longarm Formation to the west from theStructural Geology / Introduction^ 77Triassic Karmutsen Formation. The northern extension of this fault can be inferred withvarying degrees of confidence: the Cretaceous Haida Formation is separated from theSandilands Formation along Pacofi Creek (Plate 1). To the south of the eastern domain,apparent offset on faults is less, and the domain boundary is consequently poorly defined.It is arbitrarily defined in a southeast-trending lowland covered mainly by Quaternaryalluvium.3.5 Structure of the eastern and western domainsThe eastern and western domains are characterized by Triassic and Jurassic rocksof the Karmutsen Formation, and the Kunga and Yakoun groups, all overlain by Tertiaryvolcanic rocks. In the western domain, oldest lithologies are exposed in the northwestarea, and strata progressively young to the south. This regional southern tilt is consistentwith southeast-plunging megascopic structures, such as the Newcombe Inlet Anticline(Plate 1), but is seldom reflected by mesoscopic structures or regional beddingmeasurements. Tertiary volcanic rocks crop out extensively in the northern region,where they unconformably overlie all lithologies except the Yakoun Group. The Tertiarystrata are consistently tilted 20° —40° to the north and northwest.The eastern domain displays no such southerly regional tilting of the oldestlithologies; instead, the Karmutsen Formation, and the Kunga and Yakoun groups arefaulted along north, northeast, and east-striking faults. Tertiary volcanic rocks areabundant in the eastern domain, and are consistently tilted 20° —40° to the north ornorthwest. The basal contact does not demonstrate a regional northerly tilting; this isthought to reflect tilting and extension being accommodated by abundant closely-spacednormal faults with moderate offsets that are not observable in the field.Structures in both domains are dominated by north- and northeast-striking faults,with faults of other orientations being subordinate. These faults are mappable in theStructural Geology / eastern and western domains^ 78Triassic and Jurassic lithologies based on offsets of the well-defined stratigraphy. InTertiary rocks, movement histories along faults are much less constrainable - thestratigraphy is not well understood, and sparse outcrop density often preventsdetermining if the basal contact is offset. Map-scale faults in Tertiary rocks are thereforeonly inferred if offset of the basal contact can be documented beyond reasonable doubt.Mesoscopic faults of different orientations are ubiquitous in all lithologies, folds are notidentified in Tertiary strata.3.5.1 FaultsNortherly-striking faultsThe Newcombe Inlet fault zoneThe Newcombe Inlet fault zone (Plate 1) is exposed at the head of NewcombeInlet, where anastomosing north-striking fault surfaces bound slivers of the Sandilandsand Peril formations between Karmutsen Formation to the east and Sadler Limestone tothe west. The fault-bound slivers are intensely and disharmonically folded, minor foldaxes are both subhorizontal and subparallel to the fault zone, and are vertically- to northand south shallowly-plunging, and associated axial planar surfaces are subparallel to thefault zone boundaries (Figure 3.1). Karmutsen Formation rocks adjacent to the faultzone contain weakly-developed, north-trending, steeply-dipping foliation defined by theparallel preferred orientation of chlorite.The Blunt Point faultThe Blunt Point fault is a steeply-dipping, north-striking fault approximatelythree kilometres east of the Newcombe Inlet fault zone (Plate 1). It extends for at leastfive kilometres north from Blunt Point on the northeast side of Newcombe Inlet andappears as a steep-walled valley where the fault has weathered recessively. Rocks withinStructural Geology / eastern and western domains^ 79Figure 3.1: Sketch showing fault styles in Triassic and Lower Jurassic strata where faultsurfaces bound intensely folded slivers of limestone and argillite, head of NewcombeInlet. Modified from Lewis and Ross ( 1991).Structural Geology / eastern and western domains^ 80the fault zone are not exposed (Figure 3.2). At its northern known extent the Blunt Pointfault separates Sadler Limestone to the east from Sandilands Formation to the west.North-trending slivers of Karmutsen Formation and steeply-dipping Sadler Limestoneare bound by northern fault splays. No mesoscopic structures within these slivers can beattributed to activity along the fault. Farther north, this fault is covered by, or occurswithin, Tertiary volcanic rocks; offset of the basal Tertiary contact is indeterminate.The Tasu Creek faultThe Tasu Creek fault occurs in the northern part of the western domain. At itssouthern extent, it forms a valley within Tertiary volcanic rocks. Along the centralextent, it separates basalts of the Karmutsen Formation (west) from Tertiary pyroclasticrocks (east), and truncates two northeast-striking faults (Plate 1). At the northern limit ofthe study area, this fault separates Sandilands Formation to the east from KarmutsenFormation to the west. Within the creek bed of Tasu Creek, extensive Tertiary intrusivebodies crop out.The Boundary faultThe Boundary fault (Plate 1) defines the north-trending boundary separating thecentral and eastern domains and extends a minimum of five kilometres. Apparent offsetis best constrained along its southern extent, where it separates Cretaceous LongarmFormation on the west from the Triassic Karmutsen Formation. The KarmutsenFormation occurs east of and approximately 150 metres topographically above theCretaceous rocks. The Karmutsen Formation at this location is the glomeroporphyrylithofacies, which Sutherland Brown (1968) suggests occurs some 60 — 150 metresbelow the stratigraphic top of the Karmutsen Formation throughout the Queen CharlotteIslands. If his stratigraphy is regionally applicable, minimum apparent offset includesStructural Geology / eastern and western domains^81Figure 3.2: The Blunt Point Fault is a steep walled topographic lineamint whichseparates Sadler Limestone to the west from Sandilands Formation to the east.Photograph is looking north.Structural Geology / eastern and western domains^ 82the stratigraphic thickness represented by the top of the Karmutsen Formation, and theKunga Group and Yakoun Group present before deposition of the Cretaceous strata, aswell as the offset of Tertiary strata. More apparent offset is inferred within Triassic toCretaceous strata than within Tertiary strata, and Cretaceous strata is only observed westof the fault, indicating tectonic activity on this fault both before and after deposition ofTertiary volcanic strata.North-striking faults in the eastern domainOther megascopic north-striking faults are constrained by outcrop distribution inthe eastern domain. They occur approximately 750 — 1500 metres apart, and in at leastone location demonstrably cut the basal Tertiary contact. Outcrop distribution isconsistent with these faults having a steeply- to vertically-dipping attitude. These faultsare interpreted to truncate northeast-trending contacts and faults. Mesoscopic north-striking faults are common in outcrop, where they are steeply to vertically dipping.Tertiary intrusive bodies are commonly associated with these faults.Northeast-striking faultsThe second most predominant set of faults within the western and easterndomains is northeast striking, and is inferred to be southeasterly dipping. Faults of thisset are rarely observed in the field, and fault positions are determined throughdistribution of outcrops. Fault geometry is interpreted to be the same as uncommonsouth-dipping mesoscopic faults with the same strike orientation observed in outcrop.The Dass Creek faultThe Dass Creek fault intersects the study area in the northern part of the westerndomain (Plate 1). It separates hornfelsed Sandilands Formation to the north fromTertiary rocks to the south. It is observable in air photographs as an obvious topographicStructural Geology / eastern and western domains^ 83lineament, extends to some ten kilometres northeast of the study area, and terminateswhere it intersects Carmichael Inlet (P.D. Lewis, personal communication, 1990).Northeast-striking faults within the western and eastern domainsOther northeast-striking faults are mapped east and west of Newcombe Inlet.They are generally inferred from outcrop distribution; however, north of Two MountainBay, they can be mesoscopically observed separating Jurassic Yakoun Group rocks fromSandilands Formation strata, with vertical offsets of tens of metres. The majority ofthese mesoscopic faults have normal, south-side down offset, but rare northwest-dipping,north-side down faults are also observed. Northeast-striking faults in the eastern domainare interpreted to be truncated by north-striking faults based on outcrop distribution.Megascopic faults are not interpreted to cut Tertiary strata — this may be an artifact ofthe lack of stratigraphic control in Tertiary strata. Mesoscopic northeast-striking faultsare rarely observed in outcrop.Northwest-striking faultsThe third orientation of faults in central Moresby Island occurs mainly in thewestern domain, and are best exposed west of Newcombe Inlet. These faults arenorthwest-striking, and shallowly- to moderately-dipping. They are best exposed west ofMcAlmond Point, where they place Sandilands Formation over Yakoun Group withseveral metres to tens of metres of offset. These faults are also observed in outcropwithin the Sandilands Formation and Peril Formation, where they form layer-parallel slipand ramp thrust faults. Sense of movement is generally top to the southwest, however,both senses of vergence occur.A megascopic northwest-striking fault occurs west of and parallel to NewcombeInlet. It is best constrained at its southern extent by outcrop distribution; SandilandsFormation occurs topographically above Yakoun Group exposed along the shore. ThisStructural Geology / eastern and western domains^ 84fault is poorly constrained along its northern extent, and map pattern interpretationsuggests this fault is steeply-dipping.3.5.2 FoldsTwo orientations of folds occur within Kunga and Yakoun group strata: adominant set with northeast-trending axial traces is evidenced by mesoscopic folds,stereonet plots, and regional dips both east and west of Newcombe Inlet. A second set offolds with northwest-trending fold axes is observable in disharmonically folded outcrops,and inferred by stereonet plots of Kunga Group bedding. This second set of folds is notconsidered important to the development of megascopic structures. No folding isobserved in Tertiary strata.Northwest-trending foldsThe Newcombe Inlet anticlineThe best exposed northwest-trending megascopic fold is the Newcombe Inletanticline, exposed on the northeast shore of Newcombe Inlet. The Newcombe Inletanticline folds strata of the Sadler Limestone and the Peril and Sandilands formationsabout a southeast-plunging fold axis. Bedding within the Sadler Limestone is exposed atsea level along the shore of Newcombe Inlet where it is steeply dipping to vertical.Approximately one kilometre farther east, the Sadler Limestone dips 25° —35° south tosoutheast at an elevation of 150 metres, thus providing a unique indication of themagnitude of megascopic folds in central Moresby Island. The eastern limb of thisparallel fold may be only partially exposed, and the interlimb angle subtendsapproximately 60°. The wavelength and amplitude of this structure cannot bedetermined, both the eastern and western limbs have been disjoined by north-strikingfaults. Although no sense of asymmetry is obvious, the steeply-dipping western limbStructural Geology / eastern and western domains^ 85suggests southwest vergence. This anticline, together with the Newcombe Inlet faultzone, defines a lobate/cuspate geometry.Mesoscopic folds with northwest to west-northwest-trending axial traces withinthe study area are concentrated in zones of more intense deformation, and are limited tothe Peril Formation, the Sandilands Formation, and the Yakoun Group. Intensity offolding varies within these units: Kunga Group lithologies are characterized by tight toopen, upright to overturned buckle folds, Yakoun Group rocks are gently warped andupright. Characterization of buckle fold profiles typically correspond to 1B to 1C typefolds of Ramsay (1967; Figure 3.3), and range from tightly folded chevron folds torounded and open concentric folds, and rare isoclinal folds with rounded hinge zones.The wavelength of folds within the Sandilands Formation is generally within the metre toten metre range, and fold amplitude is commonly a metre to several metres.Overprinting of these features by northeast-trending folds forms disharmonic structures.Both northeast- and southwest-verging folds occur within the western and easterndomains, with southwest-verging ones being the most common. This is reflected in theweakly defined concentration of poles to bedding in the northeast quadrant of thestereonet plot for bedding both west of Newcombe Inlet, and in the eastern domain(Figures 3.4 and 3.5).Mesoscopic chevron folds are often associated with ramp and layer parallel slipstructures, and northwest-striking thrust faults are occasionally folded, indicating agenetic link between folds and faults of this orientation (Figure 3.6).Northeast- trending foldsNortheast-trending folds in Kunga and Yakoun group lithologies are evidencedby rare open folds and by superposition of northeast-trending folds on northwest-OStructural Geology / eastern and western domains^860Figure 3.3: t' vs. a plot showing variation of layer thickness within folds of KungaGroup lithologies. All plot in the 1C field, corresponding to moderate thickening ofhinge zones.Late Triassic —Lower JurassicKunga Group loIIII 13 -1215 SigmaNN = 21= 19N = 95LEGEND1 — 3-^6A 4-^97Contour method Karnb (1959)Contour interval 3 Sigmapoles to bedding^ N = 71equal area, lower hemisphere projection'44z4.1.vqlcok • !.44CO :4.cozr.As"' On •!-1coCS"0.croOOcococo00Middle Jurassic(Bajocian)Yakoun Grouppoles to beddingequal area, lower hemisphere projection/ westerndomaincentral domaineasterndomainLEGEND 1 — 34 — 67 — 910 — 121.1 13 — 15 SigmaContour method: Kamb (1959)Contour interval: 3 Sigmatz:1 !al"--#1cooc";;"coc•57:3O-ros?:izsijcaco0000•••••,,,Structural Geology / eastern and western domains^89Figure 3.6: Top to the northeast thrust fault is refolded about northwest trending foldaxis. Plane of photograph is approximately 040°, west of Newcombe Inlet. Estimatedamount a shortening from bed length measurements is 25%, no attempt was made toestimate shortening accommodated by the fault.Structural Geology / eastern and western domains^ 90trending folds. The significant variation in bedding orientations, observable in the fieldand on stereonet representations, reflects the superposition of the two orientations offolds.3.6 Structure of the Central Domain Rocks of the Cretaceous Haida, Skidegate, Longarm, and Honna formations areexposed in the central and northern parts of the central domain, where theyunconformably overlie "basement" rocks of the Sandilands Formation and the YakounGroup. The oldest basement strata are exposed at the mouth of Sewell Inlet in thenorthern area of the central domain, and stratigraphic exposure youngs to the south,analogous to the trend for the same stratigraphic level in the western domain. In general,the oldest Cretaceous strata (the Hauterivian Longarm Formation) are exposed south andwest of younger Cretaceous formations (Plate 1), and Cretaceous rocks young to thenorth. Turonian turbidites of the Skidegate Formation occur south of Sewell Inlet(Haggart, 1991) and thick accumulations of Honna Formation sandstones andconglomerates (undated) occur stratigraphically above the Skidegate Formation north andsouth of Sewell Inlet. This northerly-younging trend is consistent with the northerly dipscommonly found in Cretaceous strata south of Sewell Inlet, and with the north andnortheast-plunging fold axes common in folded Cretaceous rocks.Faults are the most common structures in Triassic and Jurassic strata. Mesoscopicfaults are ubiquitous and commonly associated with intrusive bodies, megascopic faultsare inferred on the basis of outcrop distribution. No megascopic folds are interpreted inthe Kunga or Yakoun Group strata. Mesoscopic folds are locally abundant, andconsiderable variation in bedding orientation exists throughout the central domain.The Cretaceous succession is characterized by stratigraphic repetition oflithologies and interfingering facies relationships. With the exception of the LongarmStructural Geology / central domain^ 91Formation, no unequivocal stratigraphic markers exist, such as the easily recognizableformational contacts in Triassic and Jurassic strata. It is therefore likely that the numberof faults, and their offsets are under represented and underestimated respectively. Forthis reason, structures in the central domain will be discussed according to stratigraphiclevels in which they occur. Tertiary strata in the central domain consistently tilt 20° —40° to the north or northeast. Tertiary strata are not folded, but are commonly faulted.3.6.1 FaultsFaults in Triassic and Jurassic strataStructures in Kunga and Yakoun group strata exposed in the central domain aredominated by north- and northwest-striking faults. North and east of Barrier Bay,relatively planar Sandilands and Yakoun group strata are faulted along northeast-striking,steeply south- or rare north-dipping surfaces, which are interpreted on the basis ofstratigraphic distribution to represent south-side and north-side down movementrespectively. These faults are observed on the mesoscopic scale, and are inferred on themegascopic scale by outcrop distribution. Rare northwest-striking faults are observed inoutcrop, and a megascopic fault is inferred north of Barrier Bay, based on outcropdistribution and stratal dips. East of Wilson Bay, mesoscopic faults are dense, exhibit arandom orientation, and are generally cospatial with intrusive bodies.Faults in Cretaceous and Tertiary strataTwo major fault sets occur in Cretaceous and Tertiary strata: northeast-striking,steeply-dipping, south-side-down faults, and north-striking, steeply-dipping faults. Thesemegascopic faults are entirely inferred from outcrop distribution. In general, thenortheast-striking set is truncated by the north-striking set on both mesoscopic andmegascopic scales, however the reverse relationship is rarely observed. Mesoscopicfaults are rare — intrusive bodies often obscure probable fault zones, and bedding isStructural Geology / central domain^ 92commonly rotated parallel to intrusive contacts. A megascopic north-striking faultoccurs north of Sewell Inlet along Waterfall Creek, where it separates Tertiary strata tothe west from hornfelsed Cretaceous strata to the east. Intrusions of magmatic materialare abundant on this fault, bedrock in Waterfall Creek is almost entirely composed ofTertiary intrusions. The second megascopic fault occurs in the central part of the centraldomain, where it offsets the basal Tertiary contact. It is interpreted to dip to thesoutheast, and based on mesoscopic fault geometries, the simplest offset history involvessouth-side-down movement. This fault is aligned with a fault of the same orientation tothe northeast, and these two may form a single continuous feature.3.6.2 FoldsFolds in Triassic and Jurassic strataKunga Group strata in the central domain exposed at the head of Sewell Inlet areinhomogeneously deformed. South of Sewell Inlet, quarry exposures show moderatelyeasterly-dipping strata of the Sandilands Formation with no evidence of folding, faultedagainst Yakoun Group strata exposed to the west along a steeply-dipping north-trendingfault. The Peril Formation exposed approximately 500 metres east display an intenselyfolded anticline with steeply-dipping north-trending cataclastic faults in the core (Figure3.7). This inhomogeneous partitioning of strain is typical of structural styles developedwithin the study area. Lack of exposure between outcrops precludes more detailedanalysis of strain partitioning.East of Thorsen Creek and south of Sewell Inlet rocks are chaotically deformed,and are commonly steeply dipping. Adjacent to megascopic north-striking faults,bedding is steeply dipping to overturned, and strikes are parallel to fault traces.Intrusions obfuscate structures.Structural Geology / central domain^ 93..,/\\^ /-....•.•^. •• c • :;,: ; "-^-^;^‘"Az.Figure 3.7: Intensely folded and faulted strata in the core of an anticline, south ofSewell Inlet. Fault zones are north-trending, folds are about both northwest- andnortheast-trending axis. Plane photograph is approximately 090°.Structural Geology / central domain^ 94Folds in Cretaceous strataFolds in Cretaceous strata south of Sewell Inlet are characterized by broad,megascopic warps with north to northeast-trending axial traces. Fold hinges are notexposed, fold geometry is inferred from stratal dips and rare formational contactrelationships. The trends interpreted for these megascopic features are corroborated bystereonet data (Figure 3.8).Strata exposed in Thorsen Creek south of Sewell Inlet have consistent north andnortheast dips of 30°-50° for over a kilometre, and are interpreted to represent the eastlimb of a megascopic north- to northeast-trending and north to northeast-plunginganticline - syncline pair with a wavelength of approximately one to two kilometres (Plate1). A northeast-trending fold on the north shore of Trotter Bay is defined by both contactrelationships between the Honna and the Skidegate formations and bedding orientations.South of Sewell Inlet, contact relationships between the Honna Formation and theSkidegate Formation, and bedding orientations commonly trend northeasterly and areparallel to both fold axial traces, and megascopic faults. Whether the Trotter Baystructure represents the north limb of a macroscopic fold that has been subsequentlybisected by the northeast-striking fault, or bedding rotated parallel to the fault in responseto movement along it is unclear.easterndomainwesterndomainCretaceousQueen Charlotte GroupLongarm Formationpoles to beddingequal area, lower hemisphere projectionLEGEND^1 — 34 — 67 — 910 -- 1213 — 15 SigmaContour method: Kamb (1959)Contour interval: 3 SigmaP"ticoco"c;:i •^LIr€,„c")tiar••604Es'coOticpco0.c,5Structural Synthesis / Introduction^ 964 STRUCTURAL SYNTHESIS FOR CENTRAL MORESBY ISLAND4.1 IntroductionThis chapter presents interpretations that are derived from research completed incentral Moresby Island for this study. No reference to, or comparison with, other work ismade with the exception of ages of units determined from paleontological evidence incentral Moresby Island, which help constrain the timing of deformation events. Eventsdescribed in this chapter will be integrated with regional models in chapter 5.Five deformation events can be constrained by geological relations in centralMoresby Island. The earliest recognized event is characterized by northwest-trendingfolds and faults, and is marked by the pre-Yakoun Group unconformity. The secondinvolves block faulting constrained to post-Yakoun Group and pre-Longarm Formationdeposition. Post-Cretaceous folding characterized by open northeast-trending structuresis evidence for a third deformation event. Post-Cretaceous block faulting represents thefourth recognizable event, and normal block faulting and tilting of Tertiary strata markthe fifth event.4.2 Middle Jurassic Deformation: northeast-directed shorteningThe earliest recognized event in central Moresby Island is characterized bynorthwest-trending flexural slip folds and contractional faults, and by steeply-dippingnortheast-trending (transfer ?) faults in the Karmutsen Formation, and the Kunga andYakoun Group rocks. Kunga Group strata have accommodated more shortening thanthose of the Yakoun Group. Vergence of folds is dominantly to the northeast.The Middle Jurassic deformation event is marked most notably by the pre-Yakoun Group angular unconformity, which separates moderately- to steeply-dippingStructural Synthesis / middle-Jurassic shortening^ 97beds of the Sandilands Formation from the overlying, relatively undeformed YakounGroup strata. The youngest Sandilands Formation rocks in central Moresby Island areSinemurian, Yakoun Group strata are Bajocian. Rocks of the Yakoun Group are onlyobserved overlying Sandilands Formation rocks, never older strata. Folds within theYakoun Group are open northwest-trending structures, coaxial with the older structures.This suggests the deformation event lasted into, or was reactivated syn- or post-YakounGroup deposition.Structures in the Kunga Group strata formed during this event areinhomogeneously distributed. Areas of intensely folded and faulted strata alternate withrelatively unfolded strata. Areas of most intense folding may be the surface expressionof steeply-dipping reverse faults in basement rocks. Northeast-vergence of folds inKunga Group cover strata suggests faults in basement strata may be southwest-dipping(Figure 4.1), but are not mappable due to lack of exposure and stratigraphic markers inthe Karmutsen Formation.Fold geometry in Kunga Group strata varies according to lithology, and iscontrolled by layer thickness. In the thickly-bedded Sadler Limestone, flexural slip foldsgenerally have rounded profiles. Thinly-bedded limestones and argillites exhibit chevronto round folds.The ductility contrast between the Karmutsen Formation basement and the KungaGroup cover has resulted in a regional cuspate/lobate structural geometry along thejunction between basement and cover. To the west of the axial trace of the anticline, thecuspate closure at the head of Newcombe Inlet contains slivers of sheared SandilandsFormation strata. This geometry is never observed within rocks younger than SandilandsFormation, and the timing of the shortening event which formed these structures is thusthought to predate Yakoun Group deposition.Structural Synthesis / middle-Jurassic shortening^98Figure 4.1: Schematic diagram illustrating how the geometry of basement structureswithin the crystalline Karmutsen Formation controls vergence of structures developed inthe stratified Kunga Group. Adapted from Gratier and Viallon, 1980.Structural Synthesis / middle-Jurassic shortening^ 99Regional strain is difficult to quantify, but several different methods can be usedto make strain measurements, and derive maximum and minimum values for strainexperienced by rocks locally. The first is to palinspastically restore local sections fromphotographs and field sketches, and the second is to measure strain directly fromdeformed strain markers. This results in two 'types' of strain being analyzed: restoredsections reveal strain magnitudes accommodated by layer parallel slip and foldingmechanisms, whereas deformed strain markers record finite strain suffered on the grainand subgrain scale. Several field book sketches and photographs of structures in KungaGroup strata have been restored and the results compiled in figure 4.2. Rare ammonitesmolds found in situ record finite strain of the host rock, and two measurements have beenincluded 4.3.4.3 Post- Yakoun Group deposition. and pre -Cretaceous deposition: block faultingA post-Yakoun Group deposition and pre-Cretaceous deposition faulting event isevidenced in central Moresby Island. The Cretaceous succession lies unconformably oneither Kunga Group strata, or Yakoun Group, indicating uplift of discreet fault boundblocks, and the stripping of Yakoun Group strata from the elevated fault bound areas.An alternative explanation, that Yakoun Group strata was originally inhomogeneouslydistributed is not supported. Original depositional edges should show facies changestowards thicker depocentres, a trend not noted in the central Moresby Island area.Instead, thick accumulations of tuff, shale and other lithologies end abruptly at faults(Figure 4.4). These faults are overlapped by Hauterivian Longarm Formation, arelationship directly observable in the field north of Two Mountain Bay. North-trendingfaults are the dominant block -bounding structures, northwest trending faults were likelyalso active at this time. Northwest-trending faults are common to Karmutsen Formation,Kunga Group, and Yakoun Group strata, and are rare in Cretaceous or Tertiary strata.Structural Synthesis / post-Yakoun Group^ 100132'dFigure 4.2a: Estimated amounts and directions of shortening within Kunga Groupstrata in the central Moresby Island area. The planes of the photographs in figures 4.2b- f are perpendicular to the dominant fold axis and parallel to the shortening direction,unless otherwise indicated. All shortening estimates are based on bed lengthmeasurements only. Photographs of individual outcrops on following pages illustrateswide variation in fold styles throughout the area.\ .---•\....."•^./.. ...........^ --,^ ....-....._^__..... .-..• -... -.....^-..^,...^,...-..--Structural Synthesis / post-Yakoun Group^ 101NFigure 4.2b: Sandilands Formation strata exhibiting irregular tight to open folds. Bedlength measurements indicates 35% shortening.Structural Synthesis / post-Yakoun Group^ 102Figure 4.2c: Sandilands Formation strata exhibiting irregular tight to open folds withboth rounded and angular hinge zones. Folds in this diagram plotted within the _ICcategory in figure 3.3. Bed length measurements indicates 32% shorteningStructural Synthesis / post-Yakoun Group^ 103Figure 4.2d: Sandilands Formation strata exhibiting chevron to round folds withcontractional fault surfaces parallel to axial planes. Photograph is approximately 10metres across. Bed length measurements indicates 51% shortening, no attempt was madeto estimate shortening accommodated by fault surfaces.NNStructural Synthesis / post-Yakoun Group^ 104Figure 4.2e: Sandilands Formation strata exhibiting open fold with rounded hinge zone.Bed length measurements indicates 35% shortening. Fold in this diagram plotted withinthe 1C category in figure 3.3.105Structural Synthesis / post-Yakoun Group1,u ..^•^=,c)JFigure 4.2f• A rare field example of a tight fold with a northwest-trending axial planerefolded about a northeast-trending axial surface. Northwest-directed shorteningestimated from bed length measurements is 60%. This photograph is facing southeastStructural Synthesis / post-Yakoun Group^ 106Figure 4.3: East-trending fault separating the debris flow lithotype (left) from thelapilli tuff lithotype of the Yakoun Group. Fault zone has been intruded by a felsic andpresumably Tertiary dyke.Structural Synthesis I post-Yakoun Group^ 107Figure 4.4: Deformed ammonite in the Sandilands Formation shows evidence ofmesoscopic layer parallel shortening. Strain ratio 1+e 11 +e 3 = 1.31. Rare deformedammonites indicate that shortening by mechanisms other than folding and faulting occurslocally.Structural Synthesis / syn-Cretaceous tectonism^ 1084.4 Syn-Cretaceous TectonismNo direct evidence either supporting, or refuting the presence of syn-Cretaceoustectonic activity was discovered. Indirect evidence for tectonism during HonnaFormation deposition exists, however. Large angular blocks of fragile Monotis-bearingPeril Formation are found within the Honna Formation conglomerates, suggesting anearby uplifted point source for Kunga Group strata. The lithologic uniqueness of theHonna Formation rocks also reveals a very different provenance from underlyingCretaceous elastic rocks. Source material for Longarm Formation sandstones isinvariably locally derived, while Honna Formation sandstones contain significantquantities of quartz, including chert, that have no known source in the stratigraphyexposed in central Moresby Island. Paleocurrent vectors measured in channelized HonnaFormation conglomerates in central Moresby Island indicate an eastern to southeasternsource direction (Gamba et al., 1990). Rocks directly underlying Honna Formationconglomerates have been dated as Turonian by molluscan fauna (Haggart, 1991). A syn-Cretaceous tectonic event is not unequivocally supported by this study.4.5 Post-Cretaceous deposition and pre-Tertiary deposition: foldingCretaceous strata in central Moresby Island have been demonstrably subject toone episode of shortening, which resulted in the formation of northeast-trending openmacroscopic folds. Formation of northeast-trending folds in Cretaceous "cover" stratalikely occurred when contraction occurred along northeast-trending faults, alreadypresent in the older "basement" strata, analogous to the model presented for the basementcontrol of cover folding in the Middle Jurassic shortening event. This folding is mostobvious south of Sewell Inlet. North of Sewell Inlet, strata are relatively undeformed,suggesting structures in basement strata are not homogeneously distributed.Structural Synthesis / post-Cretaceous and pre-Tertiary^ 109Northeast-trending folds are also present in Kunga and Yakoun Group strata,where they have been superimposed on the northwest-trending structures. As with thenorthwest-trending folds, these northeast-trending structures are rare, and occur onlylocally. They are likely the source of the significant scatter found in stereonet plots ofpoles to bedding for the Triassic and Jurassic units, in which northwest-trendingstructures are refolded about a northeast-trending fold axis.This event also constrains the timing of the shortening event experienced by theYakoun Group strata which studies elsewhere in the Queen Charlotte Islands have beenunable to do. Structures in the Yakoun Group are coaxial with those found in the KungaGroup. Cretaceous structures trend perpendicular to those found resulting from theMiddle Jurassic shortening event and no evidence for northwest-trending structures existin Cretaceous strata . Therefore the northwest-trending folds in the Yakoun Grouppredate the deposition of the Cretaceous strata.4.6 Post-Cretaceous and pre- (syn ?) Tertiary volcanic rock deposition: block faultingPost-Cretaceous to Tertiary block faulting followed the post-Cretaceousshortening event, and is the event which defined the domains in central Moresby Island.The effect of block faulting is best illustrated by the differential preservation ofCretaceous strata. The dominating north-trending, steeply-dipping faults formed at thistime, and the central domain was dropped relative to the eastern and western domainsalong north- and northeast-striking faults. The northeasterly-trending faults may bereactivated tear faults which were formed during the Middle Jurassic shortening event,and were reactivated during the Cretaceous shortening event. The relative amount ofvertical movement was equivalent to at least the entire thickness of the Cretaceoussection: no Cretaceous strata have been found in either the western or eastern domains,and all must have been eroded in this event. A regional northerly-tilting of CretaceousStructural Synthesis / post-Cretaceous and pre- (syn ?) Tertiary^110strata may also have accompanied this event, leading to the preservation of the oldestCretaceous strata are exposed in the southern and western regions of the central domain.South of Sewell Inlet, there is a consistent north to northeast tilt of 30° —40°, which issignificantly greater than dips found commonly in Tertiary rocks.The timing of both the onset of this event, and the preceding Cretaceousshortening event are poorly constrained. They occurred after the deposition of theCretaceous strata, the youngest of which are at most Turonian in age. It is possible thatthe contractional event and the block faulting event occurred in reverse order to thatstated here, there are no data which allow the certain determination of order in centralMoresby Island. The simplest constructible geologic history would have the shorteningevent prior to the onset of block-faulting. This is supported by the linear traces of thenorth-trending fault traces which extend over several kilometres, and appear to beunaffected by a later contractional deformation event.4.7 Syn (?) to post- Tertiary deformation: block faulting and extensionYoungest faults in the central Moresby Island area cut and offset the base of theTertiary succession. Lithologic evidence suggests both Paleogene and Neogene Tertiaryvolcanic rocks are present in central Moresby Island. Constraining tectonic activity inTertiary rocks is problematic — the pre-Tertiary unconformity was not likely horizontal,and exposure in Tertiary rocks is poor, even relative to general levels of exposure incentral Moresby Island.North- and northeast-trending faults are both present in the Tertiary rocks incentral Moresby Island. The basal contact of the Tertiary succession is demonstrablyoffset in several areas. Neogene "Masset Formation" rocks in the central domain are atthe same elevation and only several hundred metres from Paleogene strata across theStructural Synthesis / Syn ( ?) to post-Tertiary deformation_^ 111Boundary fault. The most compelling evidence for post-Tertiary tectonism is the north-to northwest-tilting, ubiquitous in Tertiary strata.The gentle north- and northwest-tilting of the Tertiary strata combined with thenortheast-trending, southerly-dipping, and south-side-down normal faults are indicativeof a south-directed, asymmetric extension, and block rotation, analogous to domino styleor bookcase faulting, which occurred after the deposition of the Tertiary strata.Two sets of dykes, defined by orientation, intrude all lithologies including theTertiary volcanic rocks. One set of dykes trends 080° —120° and is generally steeply toshallowly southerly-dipping. This set is most common in the western domain. The otherset is steeply-dipping, trends 340° —010°, and occurs mainly in the western domain.Dykes locally compose up to 80% of the rock volume in outcrop.Regional Synthesis / Middle Jurassic deformation^ 1125 REGIONAL SYNTHESIS ,5.1 IntroductionThe most recent synthesis of the regional evolution of the Queen CharlotteIslands is presented in Lewis (1991b), who integrates structural, stratigraphic, magmatic,and geophysical elements of work done by Frontier Geoscience Program and otherworkers. Because of the immense volume of recent data, and to prevent the reiteration ofmodels presented elsewhere, this chapter will focus on presenting the evolution of centralMoresby Island in a regional context. It presents only those aspects where informationderived from this study will help illuminate the larger regional picture, or where eventsobserved elsewhere can help constrain the history of central Moresby Island. Theseevents will be described chronologically.5.2 Pre-Middle Jurassic DeformationThe Karmutsen Formation basalts and Kunga Group carbonate and clastic rocksof the Wrangellian succession were deposited in a tectonically quiescent basin (Tipper etal., 1991). Maude Group lithologies, present on Graham Island, northern MoresbyIsland, and elsewhere are absent from central Moresby Island (Taite, 1989a, 1990a).Local hiati in Maude Group rocks on Skedans Rock, east of Louise Island, indicate localuplift during the Toarcian to Aalenian (Jakobs, 1989). Tipper et al. (1991) speculateregions of the southern Queen Charlotte Islands may have been emergent by this time.Coarse clastic sedimentary rocks present in the Sandilands Formation of central MoresbyIsland are indicative of deposition in a submarine fan environment. Faunal and lithologicevidence suggests a shallow water source for these sediments during the Sinemurian,consistent with emergence at a slightly younger date. The volcanic component of clasticRegional Synthesis / Middle Jurassic Deformation^ 113lithologies in the Peril and Sandilands Formation indicate a volcanic source in Norian toSinemurian time.5.3 Middle Jurassic Deformation: southwest and northeast directed shorteningThe Middle Jurassic deformation event is evident throughout central GrahamIsland and northern Moresby Island. Lewis (1991b) interprets a northwest-trendingdeformation front extending across Moresby Island, which evidently extended intocentral Moresby Island. Middle Jurassic deformation is absent from southern MoresbyIsland (Lewis, 1991a). While elsewhere in the Queen Charlotte Islands, structures aresouthwest-verging, in central Moresby Island, northeast-verging structures are dominant,possibly reflecting the geometry of faults within the basement strata in central MoresbyIsland.The onset of this event is only constrainable to post-Sinemurian in centralMoresby Island. On central Graham Island, the presence of Maude Group strata allowsthe timing to be bracketed to late Aalenian to early-Bajocian. This event is correlatedwith the possible assembly and accretion of outboard Cordilleran terranes onto NorthAmerica (Lewis, 1991b).Jurassic Yakoun Group strata represent arc volcanic rocks and derivativesedimentary rocks. Throughout the Queen Charlotte Islands, Jurassic Yakoun Grouprocks have been subject to southwest-directed shortening; however, elsewhere the timingof the Yakoun Group deformation could not be constrained due to a superimposedcoaxial event. In central Moresby Island no shortening events younger than the YakounGroup are coaxial with the Middle Jurassic event. Thus the southwest-directedshortening event lasted into, or through the Bajocian, and ended before the onset ofCretaceous sedimentation.Regional Synthesis / Post-Yakoun Group and pre-Cretaceous^ 114A regional southerly tilting of Triassic and Jurassic strata occurred after thedeposition of the Yakoun Group in central Moresby Island. A similar style andmagnitude of tilting is described on south Moresby Island (Lewis, 1991a), and may haveformed concurrently.5.4 Post-Yakoun Group and pre-Cretaceous: block faultingThompson et al. (1991) describe block faulting in north Moresby Island whichuplifted discrete fault-bound blocks and stripped them of Yakoun Group strata prior todeposition of the Cretaceous section. This event is demonstrable on central MoresbyIsland, where is can be constrained to post-Bajocian and pre-Hauterivian. On northwestGraham Island, Gamba (1991) describes a fault-bound Tithonian basin which may haveformed syn-tectonically, and as such would further constrain the timing of this event.5.5 Deposition of the Cretaceous succession The Longarm Formation and the Haida Formation lithologies representdeposition in a tectonically quiescent shelf environment which developed in response torising sea level (Haggart, 1991). The onset of coarse clastic Honna Formationsedimentation marks a change in depositional rates, and provenence of clasts. The post-Turonian age in central Moresby Island is better defined as Coniacian on north MoresbyIsland (Haggart, 1991). Haggart (1991) suggests Honna Formation deposition was alsoeustatically controlled, and corresponded to a Turronian-Coniacian sea level drop. Lewis(1991b) speculates that the Honna Formation may represent the progradation ofsubmarine fan complexes from the east, the result of foredeep deposits related to thewestward migration of the Prince Rupert thrust system (Rubin, et al., 1990). Higgs(1990) suggests the Sandspit Fault may represent the leading edge of the thrust belt, aproposition not supported by field evidence (Lewis, 1991b). In central Moresby Island,the Cretaceous succession is interpreted to represent a submarine fan environment. TheRegional Synthesis / Cretaceous shortening_^ 115prograding Honna Formation is interbedded with Skidegate Formation turbidites,representing submarine channels and overbank levee deposits.5.6 Cretaceous shorteningThroughout central Graham Island and northern Moresby Island, shortening ofCretaceous strata was southwest- and northeast-directed — coaxial with the MiddleJurassic deformation (Indrelid, 1991). The structural style in central Moresby Islandmarks a significant departure from this geometry. In central Moresby Island, shorteninghas resulted in northeast-trending structures — proposed here to be the higher levelmanifestation of contraction on pre-existing northeast-trending faults in 'basement'. Theregional significance of this change of orientation is uncertain. Tertiary strata are notfolded in central Moresby Island, thus this event is constrained as post-Turonian and pre-Paleogene.5.7 Post-Cretaceous block faultingThompson et al. (1991) describe the uplift of fault-bound blocks resulting in theerosion of the entire Cretaceous section. This event extended into central MoresbyIsland, and resulted in the domain divisions recognized in this study. The map-dominating north-trending faults formed during this event; no evidence exists whichsuggests these features are older. North-trending features are also observed in TertiaryMasset Formation rocks on Graham Island (Hickson, 1991) and in the offshore QueenCharlotte Basin (Rohr and Dietrich, 1990) and may have originally formedsimultaneously with north-trending structures in central Moresby Island.Regional Synthesis / Conclusions^ 1165.8 Tertiary Block FaultingLewis (1990; 1991a) describes an elegant and complex tectonic history for theTertiary Queen Charlotte Islands involving multiple extensional and compressionalevents related to the formation of the Queen Charlotte Basin. Tilting of Tertiary strataobserved in on central Moresby Island is compatible with the asymmetric, south-directedextensional event described for southern Moresby Island (Lewis, 1991a). This has directbearing on his model estimating amounts of extension along the Louscoone Inlet fault.In this model, the western domain (to the west of the Louscoone Inlet fault system)which includes central Moresby Island in the 'rigid' block, behaves has a rigid block, andaccommodates no extension. The presence of south-directed extension in centralMoresby Island indicates amounts of shear displacement estimated for Louscoone Inletfault may be overestimated by this model, and the absolute amounts of extension incentral and southern Moresby Island may have been underestimated. Total extensionoccurring in central and southern Moresby Island is an aggregate of extensionexperienced by the 'rigid' block, and the amount estimated in eastern 'extended' block.5.9 Conclusions1. Clastic lithologies present in the Jurassic Sandilands Formation in centralMoresby Island indicate shallow marine influences different from that documentedelsewhere in the Queen Charlotte Islands.2. The Middle Jurassic shortening event extended into central Moresby Island, andstructural styles developed are consistent with deeper structural control. Vergence ofstructures in central Moresby Island indicates this event was northeast-directed, incontrast to the southwest-directed event described elsewhere in the Queen CharlotteIslands.Regional Synthesis / Conclusions^ 1173. The Middle Jurassic shortening event lasted into or was re-activated post-Bajocian and pre-Hauterivian.4. Lithofacies in the Yakoun Group are not laterally continuous on a regional scale,and are not usable to define formal formations.5. Uplift and partial erosion of Yakoun Group strata occurred before the onset of theCretaceous marine transgression.6. Cretaceous sedimentation in central Moresby Island commenced in theHauterivian. Sediments of the Honna Formation may represent foredeep deposits relatedto the Prince Rupert thrust system.7. Cretaceous lithofacies are complex and are not regionally continuous.8. Post-Cretaceous block-faulting, such as documented on northern Moresby Islandand central Graham Island, extends into central Moresby Island.9. Two episodes of Tertiary volcanism affected central Moresby Island, and arerecognized on the basis of lithologic differences.10. Asymmetric south-directed extension occurred in central Moresby Island inTertiary time.11. Tertiary volcanism was accompanied by widespread hydrothermal alteration.12. The structural evolution of central Moresby Island is a composite of stylesobserved on central Graham Island and southern Moresby Island.References^ 118REFERENCESAnderson, R.G.^1988:^Jurassic and Cretaceous-Tertiary plutonic rocks on the Queen CharlotteIslands, British Columbia; in Current Research, Part E, Geological Survey ofCanada, Paper 88-1E, p. 213-216.Anderson, R.G. and Greig,^1989:^Jurassic and Tertiary plutonism in the Queen Charlotte Islands, BritishColumbia; in Current Research, Part H, Geological Survey of Canada, Paper89-1H, p. 95-104.Anderson, R.G. and Reichenbach, I.^1990:^A note on the geochronometry of Late Jurassic and Tertiary plutonism in theQueen Charlotte Islands, British Columbia; in Current Research, Part H,Geological Survey of Canada, Paper 89-1H, p. 105-112.^1991:^U-Pb and K-Ar framework for Middle to Late Jurassic (172->158 Ma) andTertiary (46-27 Ma) plutons in the Queen Charlotte Islands, British Columbia;in Evolution and Hydrocarbon Potential of the Queen Charlotte Basin, BritishColumbia, Geological Survey of Canada, Paper 90-10, p. 59-88.Andrew, A., and Godwin, C.I.^1989:^Lead- and strontium-isotope geochemistry of the Karmutsen Formation,Vancouver Island, British Columbia; Canadian Journal of Earth Sciences, v.26, p. 908-919.Cameron, B.E.B., and Tipper, H.W.^1985:^Jurassic stratigraphy of the Queen Charlotte Islands, British Columbia;Geological Survey of Canada, Bulletin 365, 49 p.Chase, R.L., Tiffin, D.L., and Murray, J.W.^1975:^The Western Canadian Continental Margin; Canada's Continental Marginsand Offshore Petroleum Exploration Canadian Society of PetroleumGeologists, Memoir 4, p. 701-722.Clapp, C.H.^1914:^A geological reconnaissance on Graham Island, Queen Charlotte Group, B.C.;in Geological Survey of Canada, Summary Report, 1912, p. 12-40.Coney, P.J., Jones, D.L., and Monger, J.W.H.^1980:^Cordilleran suspect terranes; Nature, v. 288, no. 5789, p. 329-333.Dawson, G.M.^1880:^Report on the Queen Charlotte Islands, 1878; Geological Survey of Canada,Report of Progress for 1878 - 79, Part B, p. 1-239.References^ 119Desrochers, A. and Orchard, M.J.^1991:^Stratigraphic revisions and carbonate sedimentology of the Kunga Group(Upper Triassic - Lower Jurassic ), Queen Charlotte Group, Queen CharlotteIslands, British Columbia; in Evolution and Hydrocarbon Potential of theQueen Charlotte Basin, British Columbia, Geological Survey of Canada,Paper 90-10, p. 163-172.Engebretson, D.C., Cox, A., and Thompson, G.A.^1984:^Correlation of Plate Motions with continental tectonics: Laramide to Basin-Range: Tectonophysics, v.3, n.2, p. 115-119.Fogarassy, J.A.S^1989:^Stratigraphy, diagenesis and petroleum reservoir potential of the CretaceousHaida, Skidegate and Honna formations, Queen Charlotte Islands, BritishColumbia; unpublished M.Sc. thesis, The University of British Columbia,1989, 177 p.Fogarassy, J.A.S., and Barnes, W.C.^1988:^Stratigraphy, diagenesis and petroleum reservoir potential of the mid- toupper Cretaceous Haida and Honna formations of the Queen CharlotteIslands, British Columbia; in Current Research, Part E, Geological Survey ofCanada, Paper 88-1E, p. 265-268.^1991:^Stratigraphy and diagenesis of the mid- to Upper Cretaceous Queen CharlotteGroup, Queen Charlotte Islands, British Columbia; in Evolution andHydrocarbon Potential of the Queen Charlotte Basin, British Columbia;Geological Survey of Canada, Paper 90-10, p. 279-294.Gamba, C.A.^1991:^An update on the Cretaceous sedimentology of the Queen Charlotte Islands,British Columbia; in Current Research, Part A, Geological Survey of Canada,Paper 91-1A , 373-382.Gamba, C.A., Indrelid, J., and Taite, S.^1990:^Sedimentology of the Upper Cretaceous Queen Charlotte Group, with specialreference to the Honna Formation, Queen Charlotte Islands, British Columbia;in Current Research, Part F, Geological Survey of Canada, Paper 90-1F, p.67-73.Gratier, J.P., and Vialon, P.^1980:^Deformation pattern in a heterogeneous material: folded and cleavedsedimentary cover immediately overlying a crystalline basement (Oisans,French Alps); Tectonophysics, v. 65, p. 151-180.References^ 120Gunning, H.C.^1932:^Preliminary report on the Nimpkish Quadrangle, Vancouver Island, BritishColumbia; Geological Survey of Canada, Summary Report, 1931, Part A, p.22-35.Haggart, J.W.^1987:^On the age of the Queen Charlotte Group of British Columbia; CanadianJournal of Earth Sciences, v. 24, p. 2470-2476.^1989:^Reconnaissance lithostratigraphy and biochronology of the Lower CretaceousLongarm Formation, Queen Charlotte Islands, British Columbia; in CurrentResearch, Part H, Geological Survey of Canada, Paper 89-1H, p. 39-46.1991:^A synthesis of Cretaceous stratigraphy, Queen Charlotte Islands, BritishColumbia; in Evolution and Petroleum Potential of the Queen CharlotteBasin, British Columbia, Geological Survey of Canada, Paper 90-10, p. 253-278.Haggart, J.W., Indrelid, J., Hesthammer, J., Gamba, C.A., and White J.W.^1990:^A geological reconnaissance of the Mount Stapelton-Yakoun Lake region,central Queen Charlotte Islands, British Columbia; in Current Research, PartF, Geological Survey of Canada, Paper 90-1F, p. 29-36.Haggart, J.W., Taite, S., Indrelid, J., Hesthammer, J., and Lewis, P.D.^1991:^A revision of stratigraphic nomenclature for the Cretaceous sedimentary rocksof the Queen Charlotte Islands, British Columbia; in Current Research, PartA, Geological Survey of Canada, Paper 91-1A , p. 367-372.Haggart, J.W., and Gamba, C.A.^1990:^Stratigraphy and sedimentology of the Longarm Formation, southern QueenCharlotte Islands, British Columbia. in Current Research, Part F, GeologicalSurvey of Canada, Paper 90-1F, p. 61-66.Haggart, J.W., and Higgs, R.^1989:^A new Late Cretaceous mollusc fauna from the Queen Charlotte Islands,British Columbia; in Current Research, Part H, Geological Survey of Canada,Paper 89-1H, p. 65-72.Hancock, J.M., and Kauffman, E.G^1979:^The great transgressions of the Late Cretaceous; Journal of the GeologicalSociety, v. 136, pt. 2, p. 175-186.Haq, B.U., Hardenbul, J., and Vail, P.R.^1987:^Chronology of fluctuating sea levels since the Triassic; Science, v. 235, p.1156-1167.References^ 121Hesthammer, J.^1990:^Structural interpretation of Upper Triassic and Jurassic units exposed oncentral Graham Island, Queen Charlotte Islands, British Columbia; in CurrentResearch, Part F, Geological Survey of Canada, Paper 90-1f, p. 11-18.^1991a:^Stratigraphic and structural geology of Jurassic units on central GrahamIsland Queen Charlotte Islands, British Columbia; unpublished MSc. thesis,University of British Columbia, Vancouver, British Columbia.1991b:^Lithologies of the Middle Jurassic Yakoun Group in the central GrahamIsland area, Queen Charlotte Islands, British Columbia; in Current Research,Part A, Geological Survey of Canada, Paper 91-1A, p. 353-358.Hesthammer, J., Indrelid, J., Lewis, P.D., and Orchard, M.J.^1991b:^Permian strata in the Queen Charlotte Islands: correlations and implications;in Current Research, Part A, Geological Survey of Canada, Paper 91-1A, p.321-330.Hickson, C.J.^1988:^Structure and stratigraphy of the Masset Formation, Queen Charlotte Islands,British Columbia; in Current Research, Part E, Geological Survey of Canada,Paper 88-1E p. 269-274.1989:^An update on structure and stratigraphy of the Masset Formation, QueenCharlotte Islands, British Columbia; in Current Research, Part H, GeologicalSurvey of Canada, Paper 89-1H, p. 73-79.1990a:^Geology, Port Clements, British Columbia; Geological Survey of Canada,Map 6-1990, scale 1:50 000.1990b:^Geology, Awun Lake, British Columbia; Geological Survey of Canada, Map7-1990 (Sheet 1 of 2), scale 1:50 000.1991:^The Masset Formation on Graham Island, Queen Charlotte Islands, BritishColumbia; in Evolution and Hydrocarbon Potential of the Queen CharlotteBasin, British Columbia, Geological Survey of Canada, Paper 90-10, p. 305-324.Hickson, C.J., and Lewis, P.D.^1990:^Geology, Frederick Island (West Half), British Columbia; Geological Surveyof Canada, Map 8-1990, scale 1:50 000.Higgs, R.^1988:^Cretaceous and Tertiary sedimentology, Queen Charlotte Islands, BritishColumbia; in Current Research, Part E, Geological Survey of Canada, Paper88-1E, p. 261-264.References^ 1221990:^Sedimentology and tectonic implications of Cretaceous fan-deltaconglomerates, Queen Charlotte Islands, Canada; Sedimentology, v. 37, pp.83-103.Indrelid, J.1990:^Stratigraphy and structures of Cretaceous units, central Graham Island, QueenCharlotte Islands, British Columbia; in Current Research, Part F, GeologicalSurvey of Canada, Paper 90-1F, p. 5-10.1991:^Cretaceous geology of Graham Island, Queen Charlotte Islands, BritishColumbia; unpublished MSc. thesis, University of British Columbia,Vancouver, British Columbia.Indrelid, J., Hesthammer, J., and Ross, J.V.1991:^Structural geology and stratigraphy of Mesozoic rocks of central GrahamIsland, Queen Charlotte Islands, British Columbia; in Evolution andHydrocarbon Potential of the Queen Charlotte Basin, British Columbia,Geological Survey of Canada, Paper 90-10, p. 51-58.Jakobs, G.K.1989:^Toarcian (Lower Jurassic) biostratigraphy of the Queen Charlotte Islands,British Columbia; in Current Research, Part H, Geological Survey of Canada,Paper 89-1H, p. 35-38.Jones, D.L. Silberling, NJ., and Hillhouse, J.1977^Wrangellia - A Displaced terrane in northwestern North America; CanadianJournal of Earth Sciences, v. 14, p. 2565-2577.Kamb, W.B.1959:^Ice petrofabric observations from Blue Glacier, Washington, in relation totheory and experiment; Journal of Geophysical Research, v. 64, p. 1891-1909.Lewis, P.D.1990:^New timing constraints on Cenozoic deformation in the Queen CharlotteIslands, British Columbia; in Current Research, Part F, Geological Survey ofCanada, Paper 90-1F, p. 23-28.1991a:^Dextral strike slip faulting and associated extension along the southern portionof the Louscoone Inlet Fault System, southern Queen Charlotte Islands,British Columbia; in Current Research, Part Geological Survey of Canada,Paper 91-1A, p. 383-392 .1991b:^Structural geology and processes of deformation on the Mesozoic andCenozoic evolution on the Queen Charlotte Islands, unpublished PhD. thesis,University of British Columbia, Vancouver, British Columbia.References^ 123Lewis, P.D., Hesthammer, H., Indrelid, J., and Hickson, C.J.^1990:^Geology, Yakoun Lake, British Columbia; Geological Survey of Canada,Map 5-1990, scale 1:50 000.Lewis P.D., and Hickson, C.J.^1990:^Geology, Langara Island (West Half), British Columbia: Geological Surveyof Canada, Map 9-1990, scale 1:50 000.Lewis, P.D., and Ross, J.V.^1988a:^Preliminary investigations of structural styles in Mesozoic strata of the QueenCharlotte Islands, British Columbia; in Current Research, Part E, GeologicalSurvey of Canada, Paper 88-1E, p. 275-279.^1988b:^Crustal shortening in a wrench fault tectonic setting, Queen Charlotte Islands,British Columbia; in Geological Society of America Cordilleran SectionAnnual Meeting, Abstracts with Programs, 20.1991:^Mesozoic and Cenozoic structural history of the central Queen CharlotteIslands, British Columbia; in Evolution and Hydrocarbon Potential of theQueen Charlotte Basin, British Columbia, Geological Survey of Canada,Paper 90-10, p. 31-50.Lewis, P.D., Haggart, J.W., Anderson, R.G., Hickson, CJ., Thompson, RI.,Dietrich, J.R., and Rohr, K.M.M^1991:^Triassic to neogene evolution of the Queen Charlotte Basin; Canadian Journalof Earth Sciences, V. 27 (in press).Lewis, P.D., Indrelid, J., Hesthammer, J., Taite, S.P., and Haggart, J.W.^1991:^Regional mapping update, Queen Charlotte Islands, British Columbia. inGeological Survey of Canada, Program and Abstracts, Cordilleran Geologyand Exploration Roundup 1991.McKenzie, J.D.^1914:^South-central Graham Island, B.C.; Geological Survey of Canada, SummaryReport for 1913, p. 34-54.Palfy, J.^1991:^Uppermost Hettangian to Lowermost Pliensbachian (Lower Jurassic)biostratigraphy and ammonoid fauna of the Queen Charlotte Islands, BritishColumbia; Unpublished M.Sc. thesis, University of British Columbia,Vancouver, British Columbia, 243 p.Ramsey, J.G.^1967:^Folding and Fracturing of rocks; McGraw-Hill, 568 p.Richardson, J.^1873:^Report on the coal-fields of Vancouver and Queen Charlotte Islands;Geological Survey of Canada, Report of Progresses for 1872-1873, p. 32-65.References^ 124Rohr, K.M.M., and Dietrich, J.R.^1990:^Deep seismic survey of Queen Charlotte Basin; Geological Survey of Canada,Open File 2258.Rubin, C.M., Saleeby, J.B., Cowan, D.S., Brandon, M.T., and McGroder, M.F.1990: Regionally extensive mid-Cretaceous west-vergent thrust system in thenorthwestern Cordillera: Implications for continent-margin tectonism;Geology, v. 18, p. 276-280.Smith, J.G. and MacKevett, E.M. Jr.,^1970:^The Skolai Group in the McCarthy B-4, C-4, and C-5 quadrangles, WrangellMountains, Alaska; United States Geologic Survey, Bulletin 1274-Q, p. Q1-Q26.Souther, J.G.^1988:^Implications for hydrocarbon exploration of dyke emplacement in the QueenCharlotte Islands, British Columbia: in Current Research, Part E, GeologicalSurvey of Canada, Paper 88-1E, p. 241-245.^1989:^Dyke swarms in the Queen Charlotte Islands, British Columbia; in CurrentResearch, Part H, Geological Survey of Canada, Paper 89-1H, p. 117-120.Souther, J.G. and Bakker, E.^1988:^Petrography and chemistry of dykes in the Queen Charlotte Islands, BritishColumbia; Geological Survey of Canada, Open File 1833.Souther, J.G., and Jessop, A.M.^1991:^Dyke swarms in the Queen Charlotte Islands, British Columbia, andimplications for hydrocarbon exploration; in Evolution and HydrocarbonPotential of the Queen Charlotte Basin, British Columbia, Geological Surveyof Canada, Paper 90-10, p. 465-488.Sutherland Brown, A.^1968:^Geology of the Queen Charlotte Islands, British Columbia Department ofMines and Petroleum Resources, Bulletin 54, 226 p.Sutherland Brown, A. and Jeffery, W.G.^1960:^Preliminary geological map, southern Queen Charlotte Islands; BritishColumbia Department of Mines.Taite, S.P.^1990a:^Observations on structure and stratigraphy of the Sewell Inlet-Tasu Soundarea, Queen Charlotte Islands, British Columbia; in Current Research, Part F,Geological Survey of Canada, Paper 90-1F, p. 19-22.References^ 1251990b:^Geology, Sewell Inlet - Tasu Sound area, Q.C.I. in Geological Survey ofCanada, Program and Abstracts, Cordilleran Geology and ExplorationRoundup 1990.1990c:^Structure and Stratigraphy of the Sewell Inlet - Tasu Sound area, QueenCharlotte Islands, British Columbia. 16th Cordilleran Tectonics Workshop,Carelton University, Ottawa, Ontario.1990d:^Sedimentology of the Upper Cretaceous Queen Charlotte Group, QueenCharlotte Islands - Implications for Reservoir Potential. in GeologicalAssociation of Canada - Mineralological Association of Canada, Programwith Abstracts, Annual Meeting 1990, Vancouver, British Columbia.1991a:^Geology of the Sewell Inlet - Tasu Sound area, Queen Charlotte Islands,British Columbia; in Current Research, Part A, Geological Survey of Canada,Paper 91-1A, p. 393-399.1991b:^Geology of the Sewell Inlet - Tasu Sound area, Queen Charlotte Islands,British Columbia; Geological Survey of Canada Open File Report 2317, scale1:25,000.Thompson, R.I.1988a:^Introduction to the Frontier Geoscience Program, Queen Charlotte Islands,British Columbia; in Current Research, Part E, Geological Survey of Canada,Paper 88-1E, p. 207-208.1988b:^Late Triassic through Cretaceous geological evolution, Queen CharlotteIslands, British Columbia; in Current Research, Part E, Geological Survey ofCanada, Paper 88-1E. 217-219.1990:^Geology, Cumshewa Inlet, British Columbia; Geological Survey of Canada,Map 3-1990, scale 1:50 000.Thompson, R.I. and Lewis, P.D.1990a:^Geology, Louise Island, British Columbia; Geological Survey of Canada,Map 2 -1990, scale 1:50,000.1990b:^Geology, Skidegate Channel, British Columbia: Geological Survey ofCanada, Map 4-1990, scale 1:50 000.Thompson, R.I. and Thorkelson, D.1989:^Regional mapping update, central Queen Charlotte Islands, British Columbia;in Current Research, Part H, Geological Survey of Canada, Paper 89-1H, p. 7-11.References^ 126Thompson, R.I., Haggart, J.W., and Lewis, P.D.^1991:^Late Triassic through Early Tertiary evolution of the Queen Charlotte Basin,British Columbia, with a perspective on hydrocarbon potential; in Evolutionand Hydrocarbon Potential of the Queen Charlotte Basin, British Columbia.Geological Survey of Canada, Paper 90-10, p. 3 - 29.Vallier, T.L.^1977:^The Permian and Triassic Seven Devils Group, western Idaho andnortheastern Oregon; United States Geological Survey, Bulletin 1437, 58p.Walker, R.G.^1984:^Turbidites and Associated Coarse Clastic Deposits; in Facies Models, SecondEdition, Edited by R. G. Walker, Geoscience, Reprint Series 1, p. 177-188.^1989:^Turbidites and turbidity currents: introduction, facies sequence and models;Society of Economic Paleontologists and Mineralogists, Short Course (inpress).Winkler, H.G.F^1979:^Petrogenesis of metamorphic rocks [revised second edition]; Springer-Verlag,New York, 237 p.Woodsworth, G.J.^1988:^Karmutsen Formation and the east boundary of Wrangellia, Queen CharlotteBasin, British Columbia; in Current Research, Part E, Geological Survey ofCanada, Paper 88-1E, p. 209-212.Woodsworth, G.J. and Tercier, P.E.^1990:^Evolution of the stratigraphic nomenclature of the Queen Charlotte Islands,British Columbia; in Evolution and Hydrocarbon Potential of the QueenCharlotte Basin, British Columbia. Geological Survey of Canada, Paper 90-10, p. 151-162.Yagashita, K.^1985:^Evolution of a provenance as revealed by petrographic analyses of Cretaceousformations on the Queen Charlotte Islands, British Columbia, Canada;Sedimentology, v. 32, p. 671-684.Yorath, CJ., and Chase, R.L.^1981:^Tectonic History of the Queen Charlotte Islands and adjacent areas - a model.Canadian Journal of Earth Sciences, v. 18, p. 1717-1738.Yorath, C.J., and Hyndman, R.D.^1983:^Subsidence and Thermal History of Queen Charlotte Basin; Canadian Journalof Earth Sciences, v. 20, p. 135-159.Appendices^ 127APPENDIX 1 Clast orientation data from which paleocurrent directions are interpretted from the HonnaFormation and the Skidegate Formation, south of Sewell InletDisk measuresents are of the AB plane in clasts with a greater than 3:3:1 aspect ratioRods: measuresents are of the A-axis direction in clasts with a greater tan 3:1:1 aspectratioStation 386^A Axis, 2nd bed8 -204AB plane 26 -314232/72^ 25 -235048/85255/46235/82242/76A axis22 -03524 -04632 -26930 -04826 -062Station 386, 2nd bed186/80214/60170/65204/62196/58200/50188/35185/45225/45230/80220/50190/70220/66A-axis22 -20514 -20838 -23050 -00425 -008Late Triassic —Lower JurassicKunga Groupeasterndomain/ westerndomain central domainAppendices^ 128Appendix 2: Stereographic projections of structural orientation dataLEGEND :=1 1 — 34 — 67 — 910 — 12III 13 — 15 SigmaContour method: Kamb (1959)Contour interval: 3 Sigma,Queen Charlotte GroupLongarm FormationCretaceouscentraldomain/ westerndomaincentral domainMiddle Jurassic(Bajocian)Yakoun GroupwesterndomaineasterndomaineasterndomainAppendices^ 129NN = 2 12counting area: 0.087expected no.: 8.22 pts. per areasigma: 2.74N = 9 5Appendices^130counting area: 0.300expected no.: 6.3 pts. per areasigma: 2.1Lc to Tric ssic —Lower^rcssicKungc GroLpcounting area: 0.072expected number: 8.35 pts. per areasigma: 2.78N= 116Ncounting area: 0.112expected no.: 7.99 pts. per areasigma: 2.66= 71Appendices^ 131Late Triassic —Lower JurassocKunga GroupAppendices^ 132Lc to Tricsslc —ower ,Licssic-<Lnga GroLpcounting area: 0.281expected no.: 6.47 pts. per areasigma: 2.16N^6counting area: 0.321expected no.: 6.11 pts per areasigma: 2.04= 19counting area: 0.250expected no.: 6.75 pts. per areasigma: 2.257N ------ 27Appendices^ 133counting area: 0.243expected no.: 6.81sigma: 2.27Middle Jurassic(Bajocian)Yakoun Group = 2 8Appendices 1349counting area: 0.191expected no.: 7.28 pts per areasigma: 2.4310.counting area: 0.095expected no.: 8.15 pts. per areasigma: 2.7285CretaceousQueen Charlotte GroupLongarm FormationAppendices^ 135Appendix 3: Cretaceous fossil identification informationReport on Cretaceous fossils from the Queen Charlotte Islands,B.C. (NTS map-areas 103 B, C), requested to be identified bySusan Taite of the University of British Columbia, Vancouver (6lots).All references to paleontologic data and age determinationsmust quote the authorship of the report, and the unique GSClocality number of the fossil collection.Reference to, or reproduction of, paleontologic data andage determinations in publications must be approved by theauthor of the fossil report prior to manuscript submission.Substantial use of paleontologic and age data inpublications should be reflected in the authorship.IDENTIFICATIONSField No.HFB-89-210aM^ GSC loc.C-156690Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 B/13-B/14 (Louise Island)UTM: Zone 9, 298500 E, 5861800 NHillside west of Clint Creek, on logging road("Fossil Hill")Possible Longarm FormationCoarse-grained feldspathic sandstoneFossils: Inoceramus cf. paraketzovi EFIMOVA, 1963Age: Although the specimens do not include a preservedbeak to firmly differentiate them from Jurassicspecies of the Retroceramus group, the form, generaloutline, coarse ribbing, and lack of strongconstrictions suggests that they are probablyrelated to the I. paraketzovi species group. Therange of this species is Hauterivian in NE USSR(Efimova, 1963; Vereschagin et a/., 1965) and theform I. cf. paraketzovi is widespread in the westernCanadian Cordillera in rocks of approximatelyHauterivian age (Jeletzky, 1970; Haggart, 1989).The probable age of the fossil supports correlationwith the Longarm Formation.Appendices^ 136Field No.HFB-90-238M^ GSC loc .C-187349Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 C/16 (Moore Channel)UTM: Zone 8, 701900 E, 5855250 NJust north of saddle in ridge north of Two MountainBayLongarm Formation, lower partFine-grained sandstone/siltstone, locally withsingle pebblesFossils: Inoceramus cf. paraketzovi EFIMOVA, 1963whole pinnate leavesinoceramid prismsAge: Hauterivian. See comments under GSC loc.C-156690,above.Field No.HFB-90-239M^ GSC loc .C-187350Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 C/16 (Moore Channel)UTM: Zone 8, 701850 E, 5855850 NRidge north of Two Mountain BayLongarm FormationFine-grained sandstone/siltstoneFossils: Inoceramus cf. paraketzovi EFIMOVA, 1963Lytoceras aulaeum ANDERSON, 1938?belemnite molds, indeterminateinoceramid prismsAge: Hauterivian. See comments under GSC loc.C-156690,above. The large ammonite fragment is similar tomaterial from the Hauterivian of northern Californiadescribed as L. aulaeum by Anderson (1938).Field No.HFB-90-242M^ GSC loc C-187361Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 C/16 (Moore Channel)UTM: Zone 8, 701700 E, 5856100 NHighest exposures on ridge north of Two Mountain BayLongarm FormationFine-grained sandstone/siltstoneAppendices^ 137Fossils: Inoceramus cf. paraketzovi EFIMOVA, 1963Entolium? sp.mactrid? bivalve, indeterminateAge: Hauterivian. See comments under GSC loc.C-156690,above.Field No.HFB-90-243M^ GSC loc.C-187362Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 C/16 (Moore Channel)UTM: Zone 8, 701750 E, 5855800 NRidge north of Two Mountain BayLongarm FormationMedium-grained, poorly indurated sandstoneFossils: Inoceramus cf. paraketzovi EFIMOVA, 1963Age: Hauterivian. See comments under GSC loc.C-156690,above.Field No.HFB-90-268M^ GSC loc.C-187387Locality: British Columbia, Queen Charlotte IslandsLat. -^N; Long. -NTS: 103 B/13-B/14 (Louise Island)UTM: Zone 9, 302500 E, 5855200 NIn bed of logging road, north side of valleydraining west from Redtop MountainLongarm Formation, float occurrenceFine-grained sandstoneFossils: Inoceramus cf. paraketzovi EFIMOVA, 1963Age: Hauterivian. See comments under GSC loc.C-156690,above. This float occurrence indicates that LongarmFormation is present somewhere in the vicinity,probably the quarry just east of the junction ofthis spur with the Metric Main.GENERAL COMMENTSThe presence of Hauterivian strata in this region of the QueenAppendices^ 138Charlotte Islands has not been previously demonstrated. Duringthe 1991 field season, I noted that the Cretaceous successioncontaining the fossil localities GSC loc.C-187349, C-187350, C-187361, and C-187362 is a fining-upward one, with a basaltransgressive-lag conglomerate (unconformably overlying theSandilands Formation), coarse- and fine-grained sandstone in themiddle portion, and fine-grained sandstone interstratified withshale at the top. This sequence therefore is very similar tothe standard Hauterivian-Barremian Cretaceous succession of theislands, as previously described by Haggart (1989, 1991) andcalled the Longarm Formation.The presence of the Longarm succession in this part of theislands supports Haggart's (1991) interpretation of eastward-directed transgreszion across the Queen Charlotte Islands duringCretaceous time. All of the deposits studied in the geographicarea covered by this fossil report represent the basal part ofthis transgressive sequence. The younger, deeper-water part ofthe succession is preserved to the northeast, in the valley ofThorsen Creek and along the shores of Sewell Inlet, where shalesand interstratified turbiditic sandstone of Albian to Turonianage have been identified.REFERENCESAnderson, F.M.1938: Lower Cretaceous deposits in California and Oregon;Geological Society of America, Special Papers No.16, 339pp., 84 pls.Efimova, A.F.1963: Nizhnemelovye peletsipody iz bassejna r. Eropol;Materialy po geologii i polezn. Iskopaemy Severo-VostokaSSSR, Byp.16, Magadan [In Russian].Haggart, J.W.1989: Reconnaissance lithostratigraphy and biochronology of theLower Cretaceous Longarm Formation, Queen CharlotteIslands, British Columbia; Geological Survey of Canada,Paper 89-1H, p.39-46.1991: A synthesis of Cretaceous stratigraphy, Queen CharlotteIslands, British Columbia; Geological Survey of Canada,Paper 90-10, p.253-277.Jeletzky, J.A.1970: Cretaceous macrofaunas; In E.W. Bamber et al.,Biochronology: Standard of Phanerozoic Time; GeologicalSurvey of Canada, Economic Geology Report No.1, 5thAppendices^ 139edition, p.649 -662, pls.23 -28.Vereschagin, V.N., Kinasov, V.P., Paraketsov, K.V., andTerekhova, G.P.1965:Polevoj atlas melovoj fauny Severo-Vostoka SSSR; Severo-Vostochnoe Geologicheskoe Upravlenie, GosudarstvennyjProizvodstvennyj Geologicheskij Komitet RSFSR, 216 pp.,74 pls. Magadan [In Russian].J.W. HaggartCordilleran DivisionGeological Survey of CanadaMarch 8, 1991

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