Vargas Island, British Columbia
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National Library Bibliotheque nationale of Canada du Canada Acquisitions and Oirection des acquisitions et Bibiiographic Services Branch des services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa, Ontarm Ottawa (Ontario) KIA ON4 KIA ON4 Yo~rft!e voue reference Our hie No!re reference NOTICE AVlS The qualit]( of this mic~roform is La qualit6 de cette microforme heavily dependent upon the depend grandement de la qualit6 quality of the original thesis de la these soumise au submitted for microfilming. microfilmage. Nous awns tout Every effort has been made to fait pour assurer une qualite - ensure the highest quality of supbrieure de reproduction. reproduction possible. If pages are missing, contact the S'il manque des pages, veuillez university which granted the communiquer avec 19universit6 degree. qui a confer6 le grade. Some pages may have indistinct La qualit4 d'impression de print especially if the original certaines pages peut laisser a pages were typed with a poor desirer, surtout si les pages typewriter ribbon or if the originales ont ete university sent us an inferior dactylographiees a I'aide d'un photocopy. ruban use ou si f'universite nous a fait parvenir une photocopie de - qualite inferieure. Reproduction in full or in part of La reproduction, m6me partielie, this microf~rrnis governed by de cette microforme est soumise the Canadian Copyright Act, & la Loi canadienne sur le droit R.S.C. 1970, c. C-30, and d'auteur, SRC 1970, c. C-30,et subsequent amendments. ses amendements subsequents. HOLOCENE RELATIVE SEA-LEVEL CHANGE: VARGAS ISLAND, BRITISH COLUMBIA Pierre A. Friele B .Sc. University of British Cclumbia, 1987 THESIS SUSMTTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCENCE (GEOGRAPHY) in the Department of Geography Pierre A. Friele 1991 SIMON FRASER UMVERSITY' August, 1991 O All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. National Libraty BibliotWque nationale 1+1 of Canada du Canada Acquisitions and Direction des acquisitions et Bibliographic Services Branch des services bibliographiques 395 Weilington Street 395,we Well~ngton Ottawa, Ontario Ottawa (Ontano) KIA ON4 K1 A ON4 Your ttle Voire reference Dur hie Notre refhence The author has granted an L'auteur a accorde une licence irrevocable non-exclusive licence irr6vocable et non exclusive allowing the National Library of permettani & la Bibliothhque Canada to reproduce, ioan, nationale du Canada de distribute or sell copies of reproduire, pr&ter, distribuer ou - his/her thesis by any means and vendre des copies de sa these in any form or format, making de quelque maniere et sous this thesis available to interested quelque forme que ce suit pour persons. mettre des exemplaires de cette these a la disposition des personnes interessees. The author retains ownership of L'auteur conserve la propriet6 du the copyright in hislher thesis. droit d'auteur qui protege sa Neither the thesis nor substantial these. Ni la thbse ni des extraits extracts from it may be printed or substantiels de cefle-ci ne otherwise reproduced without doivent 4tre imprimes ou his/her permission. autrement reproduits sans son autorisation. APPROVAL Name: Pierre Anton Friele Degree: Master of Science Title of Thesis: Holocene Relative Sea-Level Change: Vargas Island, B.C. Examining Committee: Chair: H.D. Moore, Assistant Professor I. Hutchinsoti Associate Professor Senior Supervisor M.C. Roberts Professor B.F. Atwater Senior Scientist US. Geological Survey External Examiner Date Approved: Auaust 2. 1991 PARTIAL COPYRIGHT LICENSE I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) 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. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission. Title of Thesis/Project/Extended Essay Holocene Relative Sea-Level Ctiange: Vargas Island, B.C. Author: . - (si yature) Pierre Antos Friele (name) August 9, 1991 (date) Abstract A new relative sea-level curve is presented which extends the previous sea-level curve for the west-coast of Vancouver Island from 4,000 yr BP to about 7,900 yr BP. The superceded sea-level curve, which was assembled mostly as a by product of archaeological research, showed late-Holocene emergence, but the early and mid-Holocene sea-level pattern was unknown. Thus, two alternative post-glacial relative sea-level scenarios existed: i) that of monotonic emergence from the post-glacial marine limit; or ii) that of rapid post-glacial emergence to some early-Holocene lowstand followed by Holocene submergence and, finally, the previously dwumnted late-Holocene emergence. The significance of the Vargas Island sea-level curve, developed from precise topographic surveys of modem and emergent marine landforms at 16 sites, and detailed stratigraphic and pleo-ecological analyses at five of those, is that it provides solid evidence for the latter scenario, with mean sea-level following Holocene submergence attaining a height of 2.4 - 3.4 m higher than today abut 5,100 yr BP. Following a stillstand, sea- levels did not start to fall until after 4,000 yr BP. Holocene submergence is shown to be a regiond pattern and it is fodyproposed that it be given the name the Clayoquot Transgression to distinguish it from the early post-glacial marine inundation. The 1,100 year stillstand, referred to as the Ahow Bay Stillstand, is well constrained by eight new radiocarbon dates. As well as extending the relative sea-level curve, this study, by comparison with appropriate models from the literature, attempts to resolve the geodynamic mechanisms producing the observed sea-level pattern. It is concluded that the final 1,000 years of the Clayoquot Transgression resulted from a prolonged isostatic response, possibly forebulge collapse, while late-Holocene emergence is attributed to tectonic uplift. Of particular concern is the assessment of seismic hazard along this portion of the Cascadia subduction zone. No unequivocal, co-seismicalty prduced landforms were observed on Vargas Island The dominant Holocene landforms (beach ridges, wave-cut and constructional terraces, and marine scarps) represent two discrete strandline elevations. The higher, the 6 m as1 strandline, formed during the Ahous Bay Stillstand, 5,100 to 4,OW yr BP, while the lower, the 4 m as1 strandline, represents a stilfsmnd ending about 2,200 yr BP suggesting unsteady late-Holocene emergence. Initial emergence and eventual abandonment of the 6 m strandline might reflect co-seismic qli@while abandonment of the 4 m strandline may have resulted from cu-seismic uplift or glacio-eustatic sea-level oscillations. These two processes cannot be distinguished based on present evidence. Continuous emergence for the last 2,200 years is suggested. May the wild woo& remain wild, full of thrush in June, with wolves pee to hunt and deer to flee, and with eagles spirdng down to the sparkling sea in their talons-Locked dance of Love. Friele Table of Contents Page Title Page ....... .................................................................................. i . .4 pprovaf Page ................................................................................... 11 ... Abstract ............................................................................................ 111 Quotation .......................................................................................... iv Table of Contents ............................................................................... v List of Tables .................................................................................. ix List cf Figures ................................................................................... x CHAPTER 1: Introduction ................................................................... 1 The Study of Relative Sea-level .......................................................... 1 Recent Sea-level Studies in the Pacific Northwest ..................................... 2 The Research Framework . Research Objectives ............................................................... 4 Choice of the Research Area ..................................................... 4 Outline of the Thesis ........................................................... 4 Chapter 2: Regional Setting ................................................................. 7 f ntroduction ................................................................................. 7 Physiography Regional Physiography .......................................................... 7 Physiography of Vargas Island .................................................. 7 Climate and Vegetation ................................................................... 10 Winds and Tides .......................................................................... 10 Quaternary Geology and Sea-level Change ......................., .................... 10 Tectonic Framework and History ....................................................... 12 Bedrock and Surficial Geology ........................................................