DOCSLIB.ORG

Irving1990canadian Journal of Earth

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Irving1990canadian Journal of Earth 811 1 Paleomagnetism of the Flores volcanics, Vancouver Island, in place by Eocene time E. IRVING AND M. T. BRANDON2 PacificGeoscience Centre, Geological Survey of Canada, P. 0. Box 6000, Sidney, B .C., Canada VBL 4B2 Received September 6, 1989 Revision accepted February 13, 1990 The Eocene Flores volcanics of the Insular Belt of southwestern Vancouver Island have U-Pb zircon ages of 51-50 Ma and a mean direction of magnetization (D, I) of 349.8°, 69.6° (12 collecting sites, k = 41, a95 = 7.0°). The paleopole (81.1°N, 188.0°E, K = 20, A95 = 9. 9°) agrees well with Early to Middle Eocene (54-48 Ma) paleopoles fromcratonic North America and with two Early to Middle Eocene paleopoles (49 and 52 Ma) from theIntermontane Belt of the Canadian Cordillera. This shows that both the Vancouver Island section of the Insular Belt and the Intermontane Belt were in their present positions with respect to ancestral North America at that time. The data can be used as a reference for estimating tilts in bodies that themselves contain no geological evidence of paleohorizontal; as an illustration, tilts of two Eocene intrusions on Vancouver Island are estimated. Les volcanites de Flores, d'ilgeeocene, de la ceinture Insulaire du sud-ouest de l'ile de Vancouver, foumissent des ages U-Pb sur zircon de 51-50 Ma et une direction d'aimantation moyenne (D, I) de 349,8°, 69,6° (12 sites d'echantillonnage, k = 41, a95 = 7,0°). Le paleopole (81.l0N, l88.0°E, K = 20, A95 = 9.9°) est v9isin des paleopoles de l'Ecocece moyen a precoce (54-48 Ma) de I' Amerique du Nord cratonique et de deux paleopoles de !'Eocene moyen a precoce (49 et 52 Ma) de la ceinture Intermontane de la Cordillere canadienne. Ceci demontre que la section de l'ile du Vancouver de la ceinture Insulaire ainsi que la ceinture Intermontane occupaient en ce temps leurs positions actuelles par rapport I' Amerique du Nord ancienne. Les resultats peuvent servir de reference pour evaluer Jes inclinaisons dans Jes corps pour lesquels ii y a absence d'indication geologique de paleohorizontalite; a titre d'illustration, des inclinaisons de deux intrusions eocenes sur l'ile de Vancouver sont estimees. [Traduit par la revue] Can. J. Earth Sci. 27, 811-817 (1990) Introduction Previous paleomagnetic data from Eocene rocks of the Omineca (Fox and Beck 1985) and Intermontane (Symons and Wellings 1989; Bardoux and Irving 1989) belts show that by '* Eocene time they had reached their present latitude relative to � cratonic North America (Fig. 1). The purpose of this paper is to � � describe paleomagnetic data from Eocene rocks of the Insular so• Belt, the westernmost element of the Canadian Cordillera. N PACIFIC The Eocene Flores volcanics rest unconformably on Mesozoic OCEAN rocks of the Wrangellian terrane of southwestern Vancouver Island (Fig. 2). Its paleomagnetism is of interest because, by 130° 125° 12o•w comparison with data from rocks of comparable age from the Fm. 1. Tectonic belts of the Cordillera and general locations of study craton, it ought to be possible to determine whether Vancouver area of Eocene rocks as follows: FL, Flores volcanics; KA, Kamloops Island, the major component of the Insular Belt, had become Group volcanics; KE, Kelowna volcanics; SP, Sanpoil volcanics. fixed relative to North America by the Early Eocene. These volcanics generally are silicic and in a low to intermediate Geology oxidation state. As a consequence, although a number of flows have been found to be good recorders of the paleofield, most The Flores volcanics are composed primarily of welded and have low magnetic stability and do not record the paleofield. massive ash-flow tuff and tuff breccia, with subordinate flows Symons (1971) studied two small stocks, which probably are and hypabyssal intrusions. A section of the unit having a coeval with the Flores volcanics and which he found to have stratigraphic thickness of about 730m is exposed on the normal (Totino stock) and reversed (Kennedy Lake stock) southwest side of Flores Island. Modal quartz is present in the magnetizations. However, these data cannot be used to deter­ tuff, indicating a dacitic composition. Chemical analyses have mine the Eocene paleofield because the attitudes of the stocks, however shown them to be mostly moderately potassic calc­ which may have been tilted after emplacement, are not known. alkaline andesites and dacites, with minor low-potassium The possibility of using their paleomagnetism to reconstruct tholeiitic basalts (Massey 1989). The rocks were originally their attitude will be considered at the end of this paper. mapped as part of the Jurassic Bonanza Group (Muller 1977), but their fresh appearance suggested to one of us (MTB) that they were probably younger. Accordingly, three samples were 1Geological Survey of Canada Contribution 21789; Lithoprobe collected for dating. Fission-track studies (J. A. Vance, Contribution 106. unpublished data, 1983, 1986) indicate ages of 51-55 Ma for 2Present address: Department of Geology and Geophysics, Yale their crystallization. Two of these three samples, one fromCow University, P.O. Box 6666, New Haven, CT 06511, U.S.A. Bay, Flores Island, and one from Mount Ozzard, were also 812 CAN. J. EARTH SCI. VOL. 27, 1990 FL1 "\ � U. EOCENE-OLIGOCENE L:.J CARMANAH GROUP � MESOZOIC PACIFIC F71 L. EOCENE � RIM COMPLEX � FLORES VOLCANICS 0 10 MESOZOIC � EOCENE D A L � CATFACE INTRUSIONS k :\!�� �A�a>l��� km 49°N 126°W FIG. 2. General geology of sampling region (from Brandon 1989). The stars at the southern tip of Flores Island and in the main sampling area are localities from which samples for U-Pb studies were collected. An enlargement of the main sampling area is given in Fig. 4. isotopic ages for the Pacific Rim area is given by Brandon (1989). 0.0080 There are numerous small Tertiary stocks in the Tofino­ Ucluelet area (Carson 1973; Armstrong 1988), which Muller ( 1977) mapped as the Catface intrusions. These stocks range in age from 67 to 33 Ma (Fig. 2 in Brandon 1989). Two are :::> � Mt.Ozzard 49 relevant to our study: the Totino stock, 51.6 5 Ma (K/ Ar Jl 50.0±0.5 Ma ± 0. 0.0076 biotite), and the Kennedy Lake stock, 67.4 ± 4 Ma (K/ Ar 48 hornblende) and 45. 7 ± 2. 3 Ma (K/ Ar biotite). These ages are all from Wanless et al. (1967, 1968) and have been recalculated using modem decay constants. 0.0072+--�--�-�--�-�--�-�-� Paleomagnetic results 0.048 0.050 0.052 0.054 0.056 Measurements were made on a Schonstedt spinner magne­ Pb/U tometer controlled by IBM PC's. Thermal demagnetization was FIG. 3. Concordia diagram for Pb-U dates from the Flores carried out using a Schonstedt TSD-1 furnace and altemating­ volcanics. The two zircon fractions from the Cow Bay locality are field demagnetization, a Schonstedt GSD-5 tumbling demagne­ concordant. The two fractions from the Mount Ozzard locality are tizer. Principal-component analysis (Zidjerveld 1967; Kir­ slightly discordant, indicating contamination (see text). schvink 1980) was used to isolate stable magnetizations using the programme LINEFIND (Kent et al. 1983), Directions of stable magnetizations of each specimen have been averaged to dated by the U-Pb zircon method (Fig. 3 and Table 1). The obtain the mean direction for each site (Table 2). U-Pb methods used were those of Parrish et al. ( 1987); zircons Most samples obtained in a trial collection had variable were abraded prior to analysis. Errors at 95% are quoted directions of remanent magnetization. Intensities of magnetiza­ throughout. tion varied by two orders of magnitude. These samples were The Cow Bay sample is a tuff from the basal part of the pale grey or buff in colour and silicic in composition. They sequence and its zircons yield overlapping concordant analyses include lavas, tuffs, and lithic tuffs from Flores Island, Mount and an age of 51.2 ± 0.4 Ma. The Mount Ozzard sample is also Frederick, and Mount Ozzard, and quartz dioite from the Totino a tuff fromthe basal part of the sequence. Its zircons are slightly stock exposed on Stubbs Island and at Tonquin Park (Fig. 2). discordant, indicating the presence of a minor inherited compo­ The magnetization at some sites had random directions, and nent, derived, presumably, by assimilation at depth, or surface demagnetization yielded no significant grouping. Other sites intermixing of foreign material. The lower intercept of a had complex magnetizations that appeared to result from an two-point array of data is 50.0 ± 0.5 Ma, which is taken as the intermixing of normal and reversed components, but detailed best estimate of the time of crystallization. Fission-track dates demagnetization studies were unsuccessful in separating them. on zircons from these two samples are 50. 7 ± 5. 8 and 55. 2 ± Fortunately, however, a few sites yielded coherent mgnetiza­ 6.4 Ma respectively. A third fission-track date from basal tuff tions, and during later collections their number was increased to near Mount Frederick is 54. 7 ± 5. 8 Ma. The U-Pb dates are the 13, distributed among three localities: Flores Island (1 site, Fig. more precise and indicate an age of 51-50 Ma (early Middle 2), Mount Frederick (8 sites, Fig. 4), and Mount Ozzard (4 Eocene on the DNAG (Decade of North American Geology) time sites, Fig. 4). After removal of small, soft components of scale of Palmer 1983). A summary of these and other Cenozoic magnetization, probably imposed by the present Earth's field, IRVING AND BRANDON 813 TABLE 1. U-Pb ages of zircons from Flores volcanics Cow Bay Mount Ozzard (49°15.88'N, 126°10.62'W) (48°57.22'N, 125°29.07'W) 8817-2A 8817-2B 81813-2A 81813-2B Weight (mg) 0.557 0.415 0.649 0.689 U (ppm) 584.5 528.3 569.5 515.6 Pb (ppm)a 4.639 4.192 4.509 4.023 206pb/204pbb 451 378 779.6 670.4 Pbc (pgY 377 306 242 269 208pb C%r 9.
Load more

Recommended publications
  • The Geological Framework of the Yukon Territory by C
    Y GSEOLOGICAL URVEY The Geological Framework of the Yukon Territory by C. Hart The Yukon Territory occupies the northern portion of a large geologic (and physiographic) province known as the Cordillera. This province is composed of relatively young mountain belts that range from Alaska to Mexico. Like most of the Cordillera, Yukon is composed of a diverse array of rock types that record more than a billion years of geological history. Most of the rocks have been affected by folding, faulting, metamorphism and uplift during various deformation events over at least the last 190 million years. This deformation has resulted in a complex arrangement of rock units and the mountainous terrain we see today. In Yukon, there are two main geological components which are largely separated by a major, northwest- trending fault (the Tintina): 1) the northeastern region is composed of a thick, older sequence of sedimentary rocks which was deposited upon a stable geological basement; and 2) the southwestern region is composed of a younger, complex mosaic of varying rock types that amalgamated and accreted to the stable sedimentary package. This paper briefly describes the geological framework of Yukon south of 65 degrees N and, with some exceptions, uses the Tectonic Assemblage Map of the Canadian Cordillera (Wheeler and McFeely 1991) and the Terrane Map of the Canadian Cordillera (Wheeler et al. 1991) as a foundation. However, some of the names used on these maps have been superseded by new terminology and they are included in this paper. Recent brief syntheses of Yukon physiography and geology are rare (Tempelman-Kluit, 1979; 1981), although geological compilations of Cordilleran geology are numerous and contain useful information about Yukon geology (Monger et al., 1982; Monger, 1989; Gabrielse and Yorath, 1992).
    [Show full text]
  • Review of National Geothermal Energy Program Phase 2 – Geothermal Potential of the Cordillera
    GEOLOGICAL SURVEY OF CANADA OPEN FILE 5906 Review of National Geothermal Energy Program Phase 2 – Geothermal Potential of the Cordillera A. Jessop 2008 Natural Resources Ressources naturelles Canada Canada GEOLOGICAL SURVEY OF CANADA OPEN FILE 5906 Review of National Geothermal Energy Program Phase 2 – Geothermal Potential of the Cordillera A. Jessop 2008 ©Her Majesty the Queen in Right of Canada 2008 Available from Geological Survey of Canada 601 Booth Street Ottawa, Ontario K1A 0E8 Jessop, A. 2008: Review of National Geothermal Energy Program; Phase 2 – Geothermal Potential of the Cordillera; Geological Survey of Canada, Open File 5906, 88p. Open files are products that have not gone through the GSC formal publication process. The Meager Cree7 Hot Springs 22 Fe1ruary 1273 CONTENTS REVIEW OF NATIONAL GEOTHERMAL ENERGY PROGRAM PHASE 2 - THE CORDILLERA OF WESTERN CANADA CHAPTER 1 - THE NATURE OF GEOTHERMAL ENERGY INTRODUCTION 1 TYPES OF GEOTHERMAL RESOURCE 2 Vapour-domi ate reservoirs 3 Fluid-domi ated reservoirs 3 Hot dry roc) 3 PHYSICAL QUANTITIES IN THIS REPORT 3 UNITS 4 CHAPTER 2 - THE GEOTHERMAL ENERGY PROGRAMME 6 INTRODUCTION THE GEOTHERMAL ENERGY PROGRAMME 6 Ob.ectives 7 Scie tific base 7 Starti 1 the Geothermal E er1y Pro1ram 8 MA4OR PRO4ECTS 8 Mea1er Mou tai 8 Re1i a 9 ENGINEERING AND ECONOMIC STUDIES 9 GRO6 TH OF OUTSIDE INTEREST 10 THE GEOTHERMAL COMMUNITY 10 Tech ical groups a d symposia 10 ASSESSMENT OF THE RESOURCE 11 i CHAPTER 3 - TECTONIC AND THERMAL STRUCTURE OF THE CORDILLERA 12 TECTONIC HISTORY 12 HEAT FLO6 AND HEAT
    [Show full text]
  • Petroleum Source Rock Potential of Lower to Middle Jurassic Clastics, Intermontane Basins, British Columbia
    PETROLEUM SOURCE ROCK POTENTIAL OF LOWER TO MIDDLE JURASSIC CLASTICS, INTERMONTANE BASINS, BRITISH COLUMBIA Filippo Ferri Resource Development and Geoscience Branch, BC Ministry of Energy and Mines, 6th Flr-1810 Blanshard St., Victoria, BC, Canada, V8W 9N3 Kirk Osadetz Geological Survey of Canada: Calgary, 3303 33 St. NW, Calgary, AB, Canada, T2L 2A7 Carol Evenchick Geological Survey of Canada: Pacific, 101-605 Robson St. Vancouver, BC, Canada, V6B 5J3 KEYWORDS: petroleum source rocks, petroleum, crude Subsurface characterization of potential Cretaceous oil, natural gas, Bowser Basin, Quesnel Trough, Nechako and Tertiary petroleum source rocks within the Nechako Basin, Sustut Basin, Intermontane, Interior Basins, area has been documented by Hunt (1992) and Hunt and Canadian Cordillera, Jurassic Bustin (1997). Osadetz et al. (2003) obtained RockEval pyrolytic and total organic content (TOC) data for well cuttings from all bore holes within the Nechako and INTRODUCTION Bowser basins. Evenchick et al. (2003) reported bleeding crude oil from paleomagnetic coring operations in fine The presence of suitable petroleum source rocks is a grained clastics that may be either migrated petroleum or necessary condition for the presence of an effective total residual crude oil stains in potential petroleum source petroleum system which constrains the petroleum rocks. The purpose of the present study was to sample potential of under-explored basins such as those within potential source bed horizons of Early and Middle the Intermontane region of British Columbia (Curiale, Jurassic age in areas where subsurface data is lacking. In 1994). Hayes (2002), in his report on the crude oil and addition, the following brief summary on the extent of natural gas potential of the Nechako area of British potential source bed horizons of this age within certain Columbia, indicated that a major issue for the basin was parts of the Canadian Cordillera inidicates these units are the lack of recognition of a good petroleum source rock potentially regionally distributed.
    [Show full text]
  • Mesoproterozoic–Early Cretaceous Provenance and Paleogeographic Evolution of the Northern Rocky Mountains
    Mesoproterozoic–Early Cretaceous provenance and paleogeographic evolution of the Northern Rocky Mountains: Insights from the detrital zircon record of the Bridger Range, Montana, USA Chance B. Ronemus†, Devon A. Orme, Saré Campbell, Sophie R. Black, and John Cook Department of Earth Sciences, Montana State University, P.O. Box 173480, Bozeman, Montana 59717-3480, USA ABSTRACT Jurassic detritus into the foreland basin to rels et al., 1996, 2011; Gehrels and Ross, 1998; dominate by the Early Cretaceous. Park et al., 2010; Laskowski et al., 2013). These The Bridger Range of southwest Montana, ancient sources may consist of first-cycle grains USA, preserves one of the most temporally INTRODUCTION derived from Precambrian basement provinces extensive sedimentary sections in North or more recent magmatism. However, zircons America, with strata ranging from Meso- Sedimentary rocks in the Bridger Range of are more commonly sourced from erosion and proterozoic to Cretaceous in age. This study southwest Montana, USA, record the Mesopro- recycling of previously deposited sedimentary presents new detrital zircon geochronologic terozoic–Mesozoic history of sedimentation in rock (e.g., Schwartz et al., 2019). data from eight samples collected across this this region of North America, with Mesopro- The evolution of sedimentary provenance is mountain range. Multidimensional scaling terozoic to Cretaceous stratigraphy exposed as strongly influenced by tectonic factors (Gehrels, and non-negative matrix factorization sta- a generally eastward dipping homoclinal panel 2014). Tectonic events, such as rifting and moun- tistical analyses are used to quantitatively across the range (Fig. 1). The >8 km of stratig- tain building, trigger drainage reorganization unmix potential sediment sources from these raphy collectively record critical information and uplift new sediment sources.
    [Show full text]
  • Baja British Columbia Hypothesis
    A Moderate Translation Alternative to the Baja British Columbia Hypothesis Rob e r t F.Butler and George E. Ge h re l s , km. The resulting paleogeography has Luyendyk, 1979; Beck et al., 1986). This De p a r tment of Geosciences, the appealing feature of an Andean-like, history suggests that apparent conflicts Un i ve r s i t y of Ar i zo n a , Tuc s o n , AZ 85721, continuous subduction-related magmatic between paleomagnetism and geology USA ,b u t l e r @ g e o . a r i zo n a . e d u ar c along the Cordilleran margin during can lead to significant insights that Cr etaceous time. neither discipline alone could have de l i v e re d . Kenneth P.Kod a m a , De p a r tment of IN T R O D U C T I O N The Baja B.C. controversy is focused Ea r th and Envi ro n m e n t al Sciences, One may quibble over the details, but on the magnitude of post–mid- Lehigh Univer s i t y, Be t h l e h e m , PA 18015- the general picture on paleomagnetism Cr etaceous northward transport of 3 1 8 8 ,U SA is sufficiently compelling that it is much segments of the North American m o re reasonable to accept it than to Cordillera. Did southeast Alaska, d i s re g a rd it. we s t e r n British Columbia, and the North AB S T R AC T —H.H.
    [Show full text]
  • Geophysical Interpretation of the Gneiss Terrane of Northern Washington and Southern British Columbia, and Its Implications for Uranium Exploration
    Geophysical Interpretation of the Gneiss Terrane of Northern Washington and Southern British Columbia, and Its Implications for Uranium Exploration GEOLOGICAL SURVEY PROFESSIONAL PAPER Geophysical Interpretation of the Gneiss Terrane of Northern Washington and Southern British Columbia, and Its Implications for Uranium Exploration By JOHN W. CADY and KENNETH F. FOX, JR. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1260 Gravity highs suggest that gneiss domes of the Omineca crystalline belt are the surface expression of a zone of dense infrastructure UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 UNITED STATES DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Cady, John W. Geophysical interpretation of the gneiss terrane of northern Washington and southern British Columbia and its implications for uranium exploration. (Geological Survey Professional Paper ; 1260) Bibliography: 29 p. 1. Gneiss Washington (State) 2. Gneiss British Columbia. 3. Uranium ores Washington (State) 4. Uranium ores British Columbia. I. Title. II. Series. QE475.G55C3 553.4'932 81-607564 AACR2 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Abstract ............ Gravity studies continued Introduction .......... Regional crustal models .................. 13 Geologic setting ........ East-west gravity model ............... 15 Cenozoic plate-tectonic setting North-south gravity model .............. 17
    [Show full text]
  • Electromagnetic Images of a Volcanic Zone
    Physics of the Earth and Planeta,y Interiors, 81(1993) 289—314 289 Elsevier Science Publishers By., Amsterdam Electromagnetic images of a volcanic zone Alan G. Jones *,a Isabelle Dumas b Geological Survey of Canada, 1 Observatory Crescent, Ottawa, Ont., K1A 0Y3 Canada b Genie Mineral, Ecole Polytechnique de Montréal, CP 6079Suc. A, Montréal, Qué., H3C 3A7 Canada (Received 8 November 1992; revision accepted 15 March 1993) ABSTRACT Data from 20 magnetotelluric (MT) soundings in the Coast belt of southwestern British Columbia, Canada, in the vicinity of volcanic Mounts Meager and Cayley (approximately 150 km north of Vancouver), are analysed to determine both the internal electrical conductivity structure of the Garibaldi volcanic belt and the regional conductivity structure. Galvanic distortion effects on the data are removed using Groom—Bailey tensor decomposition, and the regional 2D responses are determined in a survey-consistent reference coordinate frame for 1D and 2D modelling and inversion. The remaining unknowns, the site gain at each location, are estimated by requiring the long-period asymptotes of the E-polarization p 0 curves to be the same, and alternatively are derived as part of the 2D inversion procedure. Positive correlations are observed between an increased temperature gradient at a depth of about 200 m, a zone of enhanced electrical conductivity and drilling results. The zone of enhanced conductivity is interpreted to be due to montmorillonite-dominated clay alteration minerals which form the cap rock of the geothermal reservoir. Below this cap, the zone is electrically resistive owing to the chlorite and sericite which form the reservoir itself.
    [Show full text]
  • Eocene Initiation of the Cascadia Subduction Zone: a Second Example of Plume-Induced Subduction Initiation? GEOSPHERE, V
    Research Paper THEMED ISSUE: Subduction Top to Bottom 2 GEOSPHERE Eocene initiation of the Cascadia subduction zone: A second example of plume-induced subduction initiation? GEOSPHERE, v. 15, no. 3 Robert J. Stern1 and Trevor A. Dumitru2 1Department of Geosciences, University of Texas at Dallas, Richardson, Texas 75080, USA https://doi.org/10.1130/GES02050.1 2Jasper Canyon Research, Inc., 4100 Campana Drive, Palo Alto, California 94306, USA 12 figures; 1 table; 1 supplemental file ■ ABSTRACT focus on how the new Cascadia subduction zone in the Pacific Northwest of CORRESPONDENCE: [email protected] North America (United States–Canada) formed at ca. 55 Ma. The existing paradigm for the major ca. 56–48 Ma subduction zone reorga- There are two principal ways that a new subduction zone may form: it may CITATION: Stern, R.J., and Dumitru, T.A., 2019, Eo- cene initiation of the Cascadia subduction zone: A sec- nization in the Pacific Northwest of North America is that: (1) the Siletzia large be induced or it may form spontaneously (Fig. 1). Induced nucleation of a sub- ond example of plume-induced subduction initiation?: igneous province erupted offshore to the west of North America, forming an duction zone (INSZ) is expected if plate convergence continues after a collision Geosphere, v. 15, no. 3, p. 659–681, https://doi.org oceanic plateau; (2) Siletzia then collided with North America, clogging the event arrests convergence in a preexisting subduction zone. There are two vari- /10.1130 /GES02050.1. Pacific Northwest segment of the Cordilleran subduction zone; and (3) the eties of INSZ, polarity reversal and transference.
    [Show full text]
  • Volcanology, Petrography, and Geochemistry of the Kitselas Volcanic Rocks Compared to Rocks of the Telkwa Formation, Northwestern British Columbia
    Open File 2007-5 1 Volcanology, Petrography, and Geochemistry of the Kitselas Volcanic Rocks Compared to Rocks of the Telkwa Formation, Northwestern British Columbia By Nicole T. Boudreau A Thesis Submitted to Saint Mary’s University, Halifax, Nova Scotia in Partial Fulfillment of the Requirements for the Degree of Bachelor of Sciences, Honours, Department of Geology December 6, 2006 © Nicole T. Boudreau, 2006 Approved: Dr. Jarda Dostal Date: December 2, 2006 British Columbia Ministry of Energy, Mines and Petroleum Resources Open File 2007-5 Open File 2007-5 2 Open File 2007-5 3 Abstract Volcanology, Petrography, and Geochemistry of the Kitselas Volcanic Rocks Compared to Rocks of the Telkwa Formation, Northwestern British Columbia. By Nicole Therese Boudreau The Lower Jurassic Kitselas volcanic sequence of the Hazelton Group is located within the Intermontane Stikine Terrane in the western part of the Usk map-area in north- western British Columbia. It is surrounded by intrusive units to the north and south and by Hazelton Group volcanic rocks of the Telkwa Formation to the east. Telkwa and Kitselas rocks are coeval in age; however, the primary relationship between the two map units is enigmatic due to a structural contact and differences in composition and metamorphic grade. The objective of this thesis was thus to characterize the Kitselas volcanic rocks in terms of volcanology, petrography, and geochemistry and to use this data to determine the primary relationship between Kitselas and Telkwa rocks. The field and petrographic characteristics are consistent with a model wherein the Kitselas volcanic rocks comprise the foot-wall of a detachment fault system, which includes the Usk Fault.
    [Show full text]
  • Evolution of the Jura-Cretaceous North American Cordilleran Margin: Insights from Detrital-Zircon U-Pb and Hf Isotopes of GEOSPHERE; V
    Research Paper GEOSPHERE Evolution of the Jura-Cretaceous North American Cordilleran margin: Insights from detrital-zircon U-Pb and Hf isotopes of GEOSPHERE; v. 13, no. 6 sedimentary units of the North Cascades Range, Washington doi:10.1130/GES01501.1 Kirsten B. Sauer1, Stacia M. Gordon1, Robert B. Miller2, Jeffrey D. Vervoort3, and Christopher M. Fisher3 12 figures; 3 tables; 1 supplemental file 1Department of Geological Sciences, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, USA 2Department of Geology, San Jose State University, One Washington Square, San Jose, California 95192-0102, USA 3School of the Environment, Washington State University, P.O. Box 642812, Pullman, Washington 99164-2812, USA CORRESPONDENCE: kirsten .b .sauer@gmail .com CITATION: Sauer, K.B., Gordon, S.M., Miller, R.B., ABSTRACT sedimentary basins (e.g., Saleeby and Busby-Spera, 1992; Dickinson, 2004). Vervoort, J.D., and Fisher, C.M., 2017, Evolution of the Jura-Cretaceous North American Cordilleran The U-Pb age spectra of detrital zircons from western North American Cordi - margin: Insights from detrital-zircon U-Pb and Hf The U-Pb age and Hf-isotope composition of detrital zircons from Jurassic lleran sedimentary rocks have been used to help understand episodic high-flux isotopes of sedimentary units of the North Cas- to Upper Cretaceous sedimentary rocks adjacent to the southern North Cas- magmatism (Paterson and Ducea, 2015), the timing at which sediment sources cades Range, Washington: Geosphere, v. 13, no. 6, p. 2094–2118, doi:10.1130/GES01501.1. cades–Coast Plutonic Complex continental magmatic arc document shifting were uplifted and when basins subsided (e.g., DeGraaff-Surpless et al., 2003; provenance, the tectonic evolution of the arc system, and translation along Laskowski et al., 2013; Surpless et al., 2014), paleogeography, and terrane Received 20 January 2017 the continental margin.
    [Show full text]
  • Geochemistry and Geochronology of Eocene Forearc Magmatism on Vancouver Island: Implications for Cenozoic to Recent Plate Configurations in the Pacific Basin
    GEOCHEMISTRY AND GEOCHRONOLOGY OF EOCENE FOREARC MAGMATISM ON VANCOUVER ISLAND: IMPLICATIONS FOR CENOZOIC TO RECENT PLATE CONFIGURATIONS IN THE PACIFIC BASIN Julianne Kathleen Madsen BSc. Hons. Earth Sciences The University of Victoria, 200 1 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department of Earth Sciences O Julianne Madsen 2004 SIMON FRASER UNIVERSITY Fall 2004 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. APPROVAL Name: Julianne Kathleen Madsen Degree: M.Sc. Earth Sciences Geochemistry and geochronology of Eocene forearc magmatsim on Vancouver Island: Title of Thesis: implications for Cenozoic to Recent plate configurations in the Pacific Basin Examining Committee: Chair: Dr. Doug Stead Professor Simon Fraser University Dr. Derek J. Thorkelson Senior Supervisor Associate Professor Simon Fraser University Dr. Daniel Marshall Associate Professor Simon Fraser University Dr. Richard Friedman Research Associate (PCIGR) University of British Columbia Dr. Stephen T. Johnston External Examiner Associate Professor Department of Earth and Ocean Sciences, University of Victoria Date Approved: December 2,2004 SIMON FRASER UNIVERSITY PARTIAL COPYRIGHT LICENCE The author, whose copyright is declared on the title page of this work, has granted to Simon Fraser University the right to lend this thesis, project or extended essay to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users.
    [Show full text]
  • Dickinson2004.Pdf
    7 Apr 2004 20:19 AR AR211-EA32-02.tex AR211-EA32-02.sgm LaTeX2e(2002/01/18) P1: GCE 10.1146/annurev.earth.32.101802.120257 Annu. Rev. Earth Planet. Sci. 2004. 32:13–45 doi: 10.1146/annurev.earth.32.101802.120257 Copyright c 2004 by Annual Reviews. All rights reserved First published online as a Review in Advance on November 10, 2003 EVOLUTION OF THE NORTH AMERICAN CORDILLERA William R. Dickinson Department of Geosciences, University of Arizona, Tucson, Arizona 85721; email: [email protected] Key Words continental margin, crustal genesis, geologic history, orogen, tectonics ■ Abstract The Cordilleran orogen of western North America is a segment of the Circum-Pacific orogenic belt where subduction of oceanic lithosphere has been under- way along a great circle of the globe since breakup of the supercontinent Pangea began in Triassic time. Early stages of Cordilleran evolution involved Neoproterozoic rifting of the supercontinent Rodinia to trigger miogeoclinal sedimentation along a passive continental margin until Late Devonian time, and overthrusting of oceanic allochthons across the miogeoclinal belt from Late Devonian to Early Triassic time. Subsequent evolution of the Cordilleran arc-trench system was punctuated by tectonic accretion of intraoceanic island arcs that further expanded the Cordilleran continental margin during mid-Mesozoic time, and later produced a Cretaceous batholith belt along the Cordilleran trend. Cenozoic interaction with intra-Pacific seafloor spreading systems fostered transform faulting along the Cordilleran continental margin and promoted incipient rupture of continental crust within the adjacent continental block. INTRODUCTION Geologic analysis of the Cordilleran orogen, forming the western mountain system of North America, raises the following questions: 1.
    [Show full text]