GEOLOGICAL SURVEY OF CANADA COMMISSION GEOLOGIQUE DU CANADA

PAPER 80-35

LATE QUATERNARY GEOLOGY AND GEOCHRONOLOGY OF BRITISH COLUMBIA

Part 2: Summary and Discussion of Radiocarbon-Dated Quaternary History

JOHN J. CLAGUE

Canada 1981 PAPER 80-35

LATE QUATERNARY GEOLOGY AND GEOCHRONOLOGY OF BRITISH COLUMBIA

Part 2: Summary and Discussion of Radiocarbon-Dated Quaternary History

JOHN J. CLAGUE

1981 ©Minister of Supply and Services Canada 1981

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Author's Address Cordilleran Geology Division 100 West Pender Street Vancouver, B.C. V6B lRB

Original manuscript submitted: 1979-09-26 Approved for publication: 1980-10-01 CONTENTS

I Abstract/Resume 2 Introduction 2 Acknowledgments 3 The framework of late Quaternary geologic-climate units in British Columbia 3 Dates beyond radiocarbon range 5 Olympia nonglacial interval 5 Western System 5 Cowichan Head Formation 5 Paleoclimate 6 Interior System 6 South-central British Columbia 6 Bessette Sediments 7 Paleoclimate 7 Other areas in the Interior System 7 Rocky Mountain Trench 7 Babine Lake 7 A ti in region 7 Interior Plains 8 Summary 8 Fraser Glaciation 9 Fraser Glaciation advance phase 9 Georgia Depression 9 Evans Creek Stade 11 Quadra Sand and the growth of the Cordilleran lee Sheet 11 Vashon Stade and the Fraser Glaciation climax 12 Paleoclimate 12 Other areas in the Western System 12 Interior System 13 Eastern System 13 Interior Plains 13 Summary 14 Fraser Glaciation recessional phase 14 Georgia Depression 15 Everson Interstade 16 Sumas Stade 16 Pa leoclimate 16 Other areas in the Western System 16 Vancouver Island Ranges 16 Queen Charlotte Islands 16 Northern and central mainland coast 16 Interior System 16 Style and pattern of deglaciation 17 Glacial lakes 17 Chronology of deglaciation 18 Eastern System 18 Interior Plains 18 Summary t 8 Postglacial 19 Patterns of sedimentation and erosion 19 Sediment types and their distribution I 9 Late glacial and postglacial sea levels l 9 Vancouver !stand and the mainland 19 Early postglacial sea levels 21 Middle postglacial sea levels 21 Late postglacial sea levels 21 Contemporary sea level fluctuations 22 Queen Charlotte Islands 22 Early postglacial sea levels 22 Middle postglacial sea levels 22 Late postglacial sea levels 22 Summary 22 Paleoclimate 22 Early and middle postglacial climates 22 Southern British Columbia 23 Atlin region 24 Early Holocene glacial advances in the Cordillera 24 Late postglacial climates 24 Southern British Columbia 24 At lin region 25 Summary 25 Postg!acial Java flows and tephras 26 Glacier Peak tephra 26 Edgecumbe (?) tephra 27 Mazama tephra 27 St. Helens tephra 27 Set Y 27 Set P 27 Set W 27 Bridge River tephra 28 Edziza tephra 28 White Ri ver t ephra 28 Summary 28 Concluding remarks 28 Refere nces

Figures

4 J. Map of British Columbia and adjacent regions showing place names cited in the text 6 2. Subdivisions of late Quaternary deposits and events in British Columbia and adjacent regions 10 3. Growth of the Cordilleran lee Sheet in southern British Columbia and northern Washington during the Fraser Glaciation 14 4. Decay of the Cordilleran Ice Sheet in southern British Columbia and northern Washington during the terminal phase of the Fraser Glaciation 20 5. Maximum late Quaternary marine overlap in British Columbia 26 6. Late glacial and postglacial tephras in a nd near British Columbia LATE QUATERNARY GEOLOGY AND GEOCHRONOLOGY OF BRITISH COLUMBIA

Part 2: Summary and Discussion of Radiocarbon- Dated Quaternary History

Abstract That period of late Quaternary time in British Columbia for which there is radiocarbon dating control is subdivided into three major units: Olympia nonglacial interval (or Olympia lnterglaciation). Fraser Glaciation, and the postglacial. The Oly mpia nonglacial interval probably began more than 59 000 years ago. It ended with climatic deterioration and glacier growth at the onset of the Fraser Glaciation, perhaps as early as about 29 000 years ago in parts of the Western System and about 25 000 years ago in the Interior System. Glaciers apparently remained confined to the major mountain ranges throughout the Olympia nonglacial interval, and, in general, the sedimentary deposits, geomorphic framework and processes of the Olympia were similar to those of postglacial time. The Fraser Glaciation began with a build-up of glacier ice in the Coast Mountains. Glacier growth was slow at first, with ice confined to mountainous regions until 20 000 to 25 000 years ago. The Cordilleran glacier complex attained its maximum size about 15 000 years ago. Subsequent deglac iation was rapid - parts of the coastal lowland of British Columbia were ice free about 13 000 years ago. and the entire province probably was as free of ice as at present before 9000 years ago. During both the growth and decay phases of the Fraser Glaciation, aggradation occurred in valleys and on lowlands, drainage patterns were altered extensively, and networks of g lacial lakes developed near glacier termini. Postglacial includes the time from deglaciation until the present. The deposits of this interval formed in response to factors that generally remain active today. Extensive aggradation in river valleys during late glacial and early postglacial time was followed by degradation in most regions. In coastal areas late glacial and postglacial time was marked by changes in the level of the sea relat ive to the land. Along the Vancouver Island and mainland coasts. r elative sea levels were high during deglaciation due to glacio-isostatic depression of the crust. Subsequent isostatic uplift resulted in a rapid fall in sea level relative to the land, such that by 8000 to 11 500 years ago, depending on the locality, inner coastal areas became more emergent than they are at present. Although these areas r emained emergent until r ecently, deviations in sea level from the present during the last 5500 years have been relatively minor. In contrast, sea levels on the outer coast (i.e .. Queen Charlotte Islands and western Vancouver Island) during middle and late post.glacial time were relatively higher than at present. Differences between the se a level histories of the inner and outer coasts are due in part to differential diastrophic effects and in part to differences in the timing and magnitude of the isostatic response to deglaciation. The c limate immediately following the Fraser Glaciation was cool and moist. In some areas there were minor resurgences of remnant Pleistocene glaciers during early post.g lacial time. The climate gradually ameliorated, however , and probably was as warm as or warmer than the present from 8000 to 10 500 years ago until at least 6600 years ago (and perhaps much later). This warm interval was followed in most regions by a generally cooler moister period which has persisted until present. During this cool interval, advances of alpine glaciers occurred between about 2300 and 3100 years ago. within the last several centuries, and perhaps between 4000 and 5000 years ago. Seven dated post.glacial tephras have been recognized in British Columbia. From oldest to youngest.. these are: Mazama, about. 6600 years old; St. Helens Yn , 3300 to 3500 years old; Bridge River (older layer), 2300 to 2400 years old; St. He lens P (?), somewhat older than 2100 years; Bridge River (younger layer). 1900 to 2000 years old; Edziza, about 1350 years old; and St. Helens Wn, about 450 years old. In addition, Glacier Peak layer G, approximately 12 750 years old; Edgecumbe (?) tephra, probably 9000 to 11 000 years old; and Wh ite River tephra, approximately 1200 years old, may occur in British Columbia, although they have not been identified there.

Resume En Colombie-Britannique. la fin du Quaternaire, pour laquelle ii existe une datation au radio­ carbone. se divise en trois unit.es principales: l'intervalle interglaciaire d'Olympia (ou interglaciation d'Olympia), la glaciation du Fraser, et pffriode postglaciaire. L'intervalle interglaciaire d'Olympia a probablement commence ii y a plus de 59 000 ans. fl s'est termine avec un refroidissement du climat et l'avance des glaciers, au debut de la g laciation de Fraser , peut-e tre ii y a 29 000 ans dans les r egions occident.ales et il y a 25 000 ans environ dons l'interieur. Les glaciers semblent avoir et fi confines aux grandes chaines de montagnes pendant l'intervalle interglaciaire d'Olympia et. en general, les sediments, l 'e ncadrement morphologique et les processus de l'Olympia etaient similaires a ceux du temps postglaciaire. La glaciation Fraser a commence avec !'accumulation de q lace de glacier dons la chaine cotiere. La croissance de glacier a d'abord rte lente, la glace etant confinee aux zones montagneuses jusqu'a ii y a 20 000 a 25 000 ans. Le complexe glaciaire de la Cor·dillere a att.eint son extension maximale ii ya 15 000 ans environ. La deglaciation qui a suivi a ete rapide: certaines basses-terres cotieres de la Colombie-Britannique etaient peut-etre deja degagees ii y a 13 000 ans et toute la province l'etait probablement autant qu'aujourd'hui ii y a plus de 9 000 ans. Tant durant l'avance que durant le recul des glaciers de Fraser, des alluvions se sont deposees dons les v allees et !es basses­ t. erres. le reseau hydroqraphique a ete boulverse. et des r eseaux de lac glaciaires sont apparus pres de l'extremite des glaciers. Le temps postglaciaire dure depuis le debut de la d<'glaciation. Les sediments se sont deposes pendant cette periode se conformant a des phenomenes qui restent qeneralement actifs aujourd'hui . D'importants depots alluvionnaires ont eu lieu dons les vall ees au cours de la derniere g laciation et au debut du temps postqlaciair e; ils ont ete suivis d'une action erosive dons la plupart des r eg ions. Dans les regions cotieres, la fin de la periode qlaciaire Pt la per·iode postglaciaire ont et e marquees par des chanqments relatifs du niveau de la mer par r apport a la terre. Le long de l'ile de Vancouver et des cotes du continent, le niveau de la mer e tait plus eleve pendant la deglac iation, a cm1se de l'abaissement qlacio-isostatique de la croute terr-estre. Le souleve ment isostatique ulterieur a entraine l'abaisse ment rapide du niveau de la mer par rapport a la terre, au point que certaines cotes continent.ales emer·geaient plus ii y a 8 a 11 500 ans qu'a l'h eure actuelle. Bien que ces regions soient restees emergees jusqu'a tres r ecemment , le niveau de la mer a assez peu varie depu is 5 500 ans. Par contre, le niveau de la mer des cotes insulaires (archipel de la Re ine Charlotte et cote ouest. de l'ile Vancouver) etaient relativement plus eleves au cours du t emps postglaciaire moyen e t superieur qu'aujourd'hui. Les differences entre la variation du n iveau de la mer sur les cotes continentales et sur les cotes insu laires sont dues, en par tie. aux effets diastrophiques diff er entiels et en partie aux differences dons le t emps et de l'amplit.ude de la r eaction isostatique a la deglaciation. Le climat qui a suiv i immediatement la glaciation de Fraser e tait froid et humide. Tl y a eu d'abord quelques r esurgences des rest.es de glaciers pleistocenes dons certaines regions, ma is le climat S'est r echauffe progressivement et etait probablement OUSSi Chaud OU meme plUS Chaud que maintenant ii y a 8 000 ou 10 500 ans jusqu'a 6 600 ans (et peut-etre meme plus tard). Ce temps chaud etait suivi dons la plupart des regions par une periode plus froide et plus hu m ide et qui a oersist r jusqu'a aujour d'hui. Au cours de cet intervalle froid, les glaciers alpins ont avance ii y a environ 2 300 a 3 100 annees, au cour·s des derniers siecles et, peut-etre ii ya 4 000 a 5 00 0 ans. On a reconnu en Colombie- Britannique sept t ephras postglaciaires dates. Du plus ancien au plus recent ce sont: Mazama. ii y a environ 6 600 ans; St. Helens Yn, ii y a 3 300 a 3 500 ans; Bridge River (couche ancienne) ii y a 2 300 a 2 400 ans; St. Helens P (?), ii y a un peu plus que 2 100 ans; Bridge River (couche recente), ii y a 1 900 a 2 000 ans; Edz iza, ii ya 1 350 ans environ; et St. Helen s Wn, ii y a 450 ans environ. De plus, la couche G du Glacier Peak ii y a environ 12 7 50 ans; tephra d'Edqecumbe (?), probablement 9 000 a 11 000 ans; et le tephra de White River, 6qe de 1 200 ans environ, peuvent etre presents en Col ombie-Britannique, bien qu'ils n'aient pas encore e t e trouves dons cette r egion.

INTRODUCTION because of the questionable appropriateness of doing so and because of uncertainties i n available char ts relating The "Radiocarbon Geochronology of Southern British radiocarbon and calendar age. Readers who wish to correct Columbia" (Fulton, 1971) provides a sum111ary of the radio­ radiocarbon ages for variations in past atmospheric radio­ carbon-dated Quaternary history of southern British carbon activit y are referred to t he calibration charts and Columbia and a compi lation of most r adiocarbon dates of t ables of Stuiver and Suess (1966), Olsson (J 970), Suess ( 1970), geologic significance published before 1971. Since the Damon et al. ()972, 1974), .V\ ichael and Ra lph (1974), and publication of this important paper, much new information Stuiver ( 1978). These calibration c har t s have been prepared has been gathered on the Quaternary of Br itish Columbia. A by radioc arbon dating large number s of tree-ring samples of larger number of radiocarbon determ inations i s now known dendrochronologic age. T he accuracy of t he r adio­ available, resulting in a corresponding improvement in the carbon 111ethod al so has been evaluated from dated varved chronology of geologic events of late Quaternary age. sediments (e.g., Buddemeier, 1969; Stuiver, 1970, 197 l; In this paper the late Quaternary geology of British Tauber, 1970; Yang , J97l; Y ang and Fairhall, 1972) and by Columbia is summarized within a radiocarbon-dated comparison w i th other radiom etric dating t echniques framework consisting of three major geologic -c limate uni ts: (e.g., Peng et a l., 1978; Stuiver , 1978). All these studies hav e 14 1 2 O l ympia nonglacia l interval (or Olympia lnterg laciation), shown that the ratio of C t o C in at mosp heric C 0 2 has Fraser Glaciation, and the post g lacial. Each unit forms a undergone significant c hange in t he past, thus radiocarbon m a jor sec.tion of t he paper within which physiographic and ages calculated on the assumpt ion of constanc y of t h is r atio geologic-climate subheadings are util ized to simplify may var y substantially from t he 'true' ages of dated discussion and to group geographically and geologically materials. related dates. Physiographic subdivisions used in the text and shown in Figure I are those of Holland (1964). Acknowledgments Radi ocar bon dates cited in the text, as well as other 'v\ar cia Ruby ancJ Sa l ly T opham ass i sted in the dat es of geolog ic significance published prior to 1980 are compi lation of radioc arbon dates u tilizedt in his paper , and summarized in a series of tables in C lague (1980). A ll r ited their he lp is gra tefully acknowledged. R.N.W. D iL abio and age determinations a re in radiocarbon year s based on the R.J. Fulton read and commented on an early version of the original ('Libby') half life of 5570 ± 30 years. No attempt has paper. been made t o change radiocarbon ages t o calendar ages

2 THEFRAMEWORKOFLATEQUATERNARYGEOLOGIC­ Most of the dates beyond t he radiocarbon range are CLIMATE UNITS IINI BRITISH COLUMBIA frorn nonglacial deposi ts overlain by a single t il l, t he latter presumably deposited during the Fraser G laciation. In suc h The geologic-climate framework employed in this paper cases, t he dated sediments are thought to have been is a synthesis of work published by many Quaternary deposited during the early part of the Olympia nonglacial geoscientists over the past 30 years. This framework has interval. Support for this supposition is provided by the fact evolved over this period and undoubtedly will be refined that in t he Georgia Depression** of southwest e rn British further as additional information becomes available; how­ Columbia sediments dated at beyond the radioca rbon range ever, its basic elements are now well established and thus can lie with apparent conformity beneath sediments containing be used for grouping and dise'.ussing radiocarbon dates. organic material of finite Oly mpia age (e.g., F yles, l 963, Readers interested in the details of Quaternary stratigraphy p. 38; Dyck et al., l 965, p. 37). and stratigraphic nomenclature in British Columbia should examine many of the papers listed in thE' Reference It is possible, however, that some of t he dated section \e.g., Fyles, 1963; Armstrong et al., 1965; stratified sediments underlying a single till may have been Armstrong, J 97 5a, b, 1976, J 977 a, b, J 98 l; Armstrong and deposited during an interstade or interglaciation preceding Hicock, 1975, 1976; Clague, 1975c; Fulton, l975a, b, 1976; the Olympia . For example, it is conceivable that Fraser Tallman, 1975; Miller, 1976; Rutter, 1976, ! 977; Ryder, 1976, Glaciation ire locally ma y have eroded Olympia-age in press (a), in press (b); Armstrong and Clague, l 977; Fulton sediments and ju xtaposed across an unconformit y Fraser and Smith, 1978; Mathews, 1978; Alley, 1979; Hicock, 1980). Glaciation drift and pre-Olympia stra tified sediments. Alternatively, the single till at these sites ma y have been That period of late Quaternary time for which there is deposited during a glaciation preceding the Olympia radiocarbon dating control is subdivided into: (I) an early nonglacial interval. This latte r possibility is considered interval during which nonglacial conditions prevailed over unlikely, howe ver, because the dated sites are in areas known most of British Columbia, (2) a middle interval dominated by to have been glaciated during the F raser Glaciat ion, and glacial environments and climates, a nd (3) a late interval because the till is at or nea r the land surface and is present during which nong!acial conditions again prevailed. These are over la rge areas without a cove r of Olympia-age sedi ments. respec tively the Olympia nonglac ial interval* , the Fraser Where sediments overlie this till, they invariably are either Glaciation, and the postglacial. During each of these postglacial or late Fraser G laciation in age. intervals, characteristic suites of sediments were deposited and distinc tive landforms developed; thus, late Quaternary The oldest date beyond the radiocarbon range from stratigraphic units in British Columbia are closely tied to t he sediments beneath a single till is >51 000 years (G SC-94-2, above geologic-climate framework. Fulton and Halstead, 1972, p. 9). This date was obtained on wood in a marine diamicton on southeastern Vancouver Current nomenc lature applied to major late Quaternary Island. The dated sediments, which likely were deposited Jithostratigraphic uni ts and to subdivisions of the Fraser during the transition from the penultimate (pre-Fraser) Glaciation in various parts of the province and bordering g laciation to the Olympia nonglacial interval (Armst rong and regions is summarized in Figure 2. Although Fraser C lague, 1977, p. 14 79), are overlai n with apparent conformity Glaciation sediments in some areas have been subdivided into by Ol ympia sed iments of fini te radiocarbon age. The latter, lower order stratigraphic units and events of stadial­ in turn , are overlain progressively by outwash, t il l, and interstadial rank have been recognized, no attempt yet has glaciomarine sediments, a!J de posited during the Fraser been made to formally define lithostratigraphir and geologir­ G lacia ti on. Thus, the stratigraphic relationships at t his site climate subunits of the Olympia nonglacial interval and the indicate that the Olympia nonglacial interval began more postglac ia l. t han 51 000 years ago. One older radiocarbon date (58 800 + years, QL- 195, C lague, 1977a, p. 15), how­ DATES BEYOND RADIOCARBON RANGE n3g ever, has been obtained on what are thought to be sediments "Greater-than" radiocarbon dates range from of the Olympia nonglac ia l interval, thus possib ly extending >II 600 years 0-2244A, Mathews, 1978, p. 17) to the beginning of the Olympia even 'farther back in time. >62 000 years (QL-194, Lowdon and Blake, 1978, p. 9). The chronostratigraphic significance of many of these dates is in doubt because they represent only minimum ages of dated materia ls.

* The "c lima tic episode immediately preceding the last major glac iation" originally was termed the Olympi'1 lnterglac iation (Armstrong et al., 1965, p. 324). Later, Hansen a nd Easterbrook (I 97 4, p. 598) argued on the basis of Ji t hostra tigraphic a nd palynologic: evide nce from Puget Lowland, Washington, that the Olympia was of insufficient length and its c lima te too cool to justify the formal appelation "interglaciation". However, in British Columbia at least, the Olympia persisted far longer than the present nonglacial climatic episode which is generally considered to be an inte rglacia tion rather than an inte rstade. Perhaps of g reater importanc:e is the c haracter of the Olympia climate. An interglaciation is charac terized by a climate simi lar to that of the present, t hat is, one incompatible with the wide e xtent of glaciers in North America and Europe as is characteristic of glac ial episodes. Although not enough is known of the climate of British Columbia during O lympia time, there is evidence that it was similar to t hat of the present for at least part of this interva l (e.g., Clague, 1978a; Alley, 1979). Furthermor·e, it appears that at no t ime du ring the O ly mpia did glaciers occupy lowland areas in British Columbia. On a global scale , however, the c limate during Olympia time apparently was sufficiently cool for ice shee ts to exist on parts of Scandinavia and northeastern Canada (e.g., Dre imanis and Raukas, I 97 5; Andre ws and Barry, 1978); therefore it can be argued that the Olympia interval should be of interstadial rather than interglacial rank. In this paper the more informal and pe rhaps less controve rsial term "Olympia nonglacial interval" is used in preference to both "Olympia lnterglaciation" and "Olympia lnterstade". It is possible, however, that as our understanding of Olympia climatic conditions improves, we will be in a better position to decide whether the interval is more appropriately identified as inte rglac ial or interst adial. ** Place names r ited in the text are located in Figure !. 3

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60 ""' ""' Dates beyond the radiocarbon dating range a lso have These environments changed spatially through time. been obtained on sediments underlying two or more ti lls. In For example, as the Olympia nonglacial int erval progressed, such cases the dates are of limited value in correlating and sea a reas became progressively more restricted in t he identifying stratigraphic units. Because these sediments Georgia Depression due to isostatic and possibly d iastrophic presently are poor ly dated and are exposed in only a uplift and to the influx of sediments into the basin from the fragmentary fashion at scattered localities, little is known of adjacent mountains. Thus, marine sediments were overlain their age, origin, and regional relationships. The little that is by estuarine and fJuvial deposits as terrestrial lowland areas known is based on studies of pre-Olympia de posits in the expanded at the expense of the sea. The common occurrence southern Inte rior System (Fulton, 197 5a, b, 1976; Fulton and of Olympia-age estuarine and fJuv ia l silt and gravel overlying Smith, 1978) and in the Georgia Depression (Fyles, 1956, marine mud and sand is the basis for the subdivision of t he 1963; Armstrong, 197 5a, b, 1977 a, b; Armstrong and Cowichan Head Formation into two members. Hicock, 1975, 1976; Hicock, 1980). The Cowichan Head Formation is overlain by thick, cross-stratif ied, well sorted sand, termed "Quadra Sand" by OLYMPIA NONGLACIAL INTERVAL C !ague (I 976a, 1977 a). CJ ague interpreted the sand to be outwash deposited during the transition from nonglacial to The Olympia nongJacial interval is the time preceding gladal conditions at the beginning of the Fraser Glaciation. the last major glaciation in British Columbia when Fyles (1963) included the sand in his "Quadra sediments", an intermontane valleys, basins, plateaus, and coastal lowlands informal lithostratigraphic unit comprising a ll sediments were largely free of glacier ice. Extensive deposits of deposited during the Olympia nonglacial interval. In Olympia age occur in the lowlands of the Georgia Depression contrast, Clague ( l 976a, 1977 a) and Armstrong and and in many valleys in southern British Columbia. In Clague (1977) emphasized the glaciofluvial origin of Quadra addition, deposits of limited or unknown areal extent at Sand and thu s grouped it with other drift deposits of the scattered localities elsewhere in British Columbia ha ve Fraser Glaciation. According ly, they considered the yielded finite Olympia radiocarbon ages. Cowichan Head Formation to be the only unit deposited during the Olympia nonglacial interval. Western System Most finite radiocarbon dates on deposits of the Paleoclimate O ly mpia nonglacial interval are from the Georgia Depression, Published information on climatic condit ions during the an elongate basin located between the Coast Mountains of O lympia nonglacial interval in coastal southweste rn British mainland British Columbia and the Vancouver Island Ranges. Columbia and northwestern Washington has been su mmarized Thick unconsolidated sediments underlie much of the by Clague (J978a) and Alley (1979). Fyles (1963, p. 28) lowlands bordering the Strait of Georgia and provide a concluded that eastern Vancouver Island was forested, at detailed record of the late Quaternary environments and least in part , and that the c limate during part of the Olympia geomorphic history of the region. interval was somewhat cooler than at present. Gascoyne( l980) and Gascoyneetal. (!980) likewise Cowichan Head Formation considered the Olympia climate to be cooler than that of the Sediments of the Olympia nonglacial interval in present. On the basis of oxygen isotope fract ionation in the Georgia Depression are included in the Cowichan speleothems dated by uranium-series methods, they proposed Head Formation (Fig. 2; Armstrong and C lague, 1977). that cave temperatures near Alberni on Va ncouver Island Reliable finite radiocarbon dates from this unit range decreased 4°C between about 64 000 and 28 000 years ago. This temperature decrease was attributed to gradual c li matic from 23 600 ± ngg to 40 500 ± 1700, a nd possibly deterioration during the Olympia nongJacial interval. 58 800 ± gg years (no laborat ory number, Ande rson, 1968, Alley ( l 976a, 1979) examined fossi I pollen spectra of the n Cowichan Head Formation on eastern and southern Vancouver p. 427; GSC-2167, Armstrong and Clague, 1977, p. 14 78; Is land and concluded that lowland vegetation and climates QL-195, Clague, 1977a, p. 15). from before 51 000 to about 29 000 years ago were broadly The Cowichan Head Formation consists of fluvial, similar to the present. Finally, Armstrong and C lague ( 1977, estuarine, and marine silt, sand, and gravel. Armstrong and p. 1477-1478) reported on fossil beetle and pollen Clague (1977) subdivided the formation in to a lower marine assemblages from the Cowichan Head Formation and stated member cons is ting mainly of c layey silt and sand and an that the Olympia c lima te was at times similar to, and at upper estuarine and fJuvial member comprising gravel and times cooler than the present. sandy silt, in general rich in fossil plant remains. Palynological data obtained from late Qua ternary The Cowichan Head Formation commonly is underlain sediments in northwestern Washington State bear on the by glaciomarine, glaciolacustrine, and glaciofluvial paleoclimatic conditions in nearby southwestern Br itish sediments, which in turn are underlain by till. The sequence Columbia. For example, Florer (1972) and Heusser (1972, apparent ly is conformable and records the transition from 1977) compared modern and radiocarbon-dated foss iJ poJJen glacial conditions of the penultimate glaciation to nong lacial assemblages on Olympic Peninsula and concluded t hat during conditions of the Olympia nonglacial interval. As g laciers the O lympia nonglacial interval average July temperatures retreated from the Georgia Depression at the close of the near the coast were 8 to l 3°C - 2 to 7°C colder than at penultimate glaciation, glaciomarine, g laciolacustrine, a nd present (e.g., Heusser, 1977, p. 299-30 I). Heusse r argued gJaciofJuv ial sediments were deposited on the isosta tically that the climate fluctuated within the Olympia interval; cold depressed lowlands. With the complete disappearance of periods with te mperatures comparable to those of t he Fraser glacier and drift ice from southwestern British Columbia, Glaciation maximum alternated with periods of relative glacigene sedimentation was succeeded by marine, estuarine, warmth during which temperatures approached those of the and fluviaJ sedimentation in a physiographic setting similar to present. Si mi lar conclusions were reached by Hansen and that c haracterizing the area at present. Thus, rivers and Easterbrook (1974) on the basis of palynological investi­ streams flowed across the isostaticaJJy up lifted lowlands and gations in Puget Lowland east of the Olympic \fountains and into the sea. Channe l a nd overbank sediments were deposited south of the Georgia Depression. Hansen and on floodplains and along stream courses; deltaic, lagoonal, Easterbrook ( 1974, p. 59 3) and Easterbrook (l 976a, p. 90; and littoral sediments accumulated in coastal areas; and 1976b, p. 447-448) also proposed that Puget Lowland was marine muds were deposited in offshore areas. occupied by glaciers during part of Olympia time.

5 It is difficult to reconcil e the above evidence for the existence of glacial climatic condit ions during parts of the Olympia interval in northern Washington both with the z palynological evidence that Olympia climates were similar w 0 to, or s li ghtly cooler than those present on Vancouver Island ~ :{ and with t he absence of coeval glacial events in lowland ::> u ~ <( areas throughout southern British Columbia. It is possible 0 that intervals of extreme cold were too brief to lead to "" significant glaciation in the Cordillera. There remains an incompatibility, however, be tween the paleoclimatic interpretations based on palynostra tigraphic studies in Washington and British Columbia. It seems probable that the O lympia-age temperature reductions estimated by Heusser ( 1972, J 977) and Hansen and East e rbrook (1974) are too large a nd that the Ii thostra tigraphic evidence for glaciation during t he Olympia interval in Puget Lowland is invalid (see also Fulton et al., 1976).

Interior System Radiocarbon-dated sediments of Olympia age occur in w several valleys in south-central and southeastern British w"" w Columbia a nd in the northern Rocky \l\ountain Trench and at u"' zu Babine Lake in the northern Interior System. z ~ w Q Q <( Q South-Central British Columbia i

Bessette Sediments ~ 1-- z Sedimentary deposits of the Olympia nonglacial interval ~ ~ ~ <( V) in south-central Br itish Columbia are included in the Bessette V) 0 < ~ u I-­ Sediments (Fulton, 197 5a, b, 1976; Fulton and Smith, 1978). "' V) < z uz "' 1-- w 0 V) 0 9 Blake, 1970, p. 72; GSC-74U, Lowdon and Blake, 1968, p. 224). z V) 0.. ,_ w"' 1-- At two s ites in southern British Columbia there are z radiocarbon-dated exposures of Bessette Sediments that span long periods of time (Fulton, 1968, 1975b; Fulton and Smith, V) 1978; Alley et a l., in press). A sequence exposed at the <( V) .... w .... - 1-­ V)... ~ U z _ ,_ z Duncan Dam borrow pit in the Purcell Trench dates from <( "" "' w sequence has been correlated by tephrochronology with 0.. "'<( V) ~ sediments exposed along Bessette Creek east of Lumby (Westgate and Fulton, 1975). Bessette Sediments at t he latter site, the t ype locality for the unit, range in age from z 19 JOO ± 240 to more than 31 200 ± 900 years old (GSC-9 13, 0 I-- Lowdon a nd Blake, 1970, p. 72; GSC-2031, We stgate and < <( Fulton, 1975, their Table 2). The date of 19 JOO± 240 years 0.. u is of conside rable importance in tha t it defines the age of the ,_"' ~<( cont act between floodplain deposits of the Bessette 0 "' Sediments and overlying laminated lacustrine sedime nts of ,_w the Kamloops Lake Drift (Fig. 2). The change from a fluvial z to a lacustrine environment a t Bessette C reek is thought to be due to disruption of the regional drainage pattern by g laciers advancing south across the southern Interior System during the Fraser Glaciation (Fulton, 197 l , p. 8). Bessette Sediments are underlain by Okanagan Centre Drift, deposited during the glaciation immediately preceding the Olympia nonglacia l interval, and a re overlain by Kamloops Lake Drift deposited during the Fraser Glaciation (Fig. 2). Bessette Sediments for med within a geomorphic framework similar to that in south-central British Columbia today - "large valleys filled in part by sediments and in part I by lakes, set between hilly upland or mountain blocks" ~ z (Fulton, 197 1, p. 5). As they are at present, sedimentation <( Q <( <( u 0: u patterns during the Olympia nonglacial interval were <( .... ~ y ~ ~ ~ <("' complex. A variety of fluvial and organic sediments were 0 : ~ () ~ u z .... "' u V) <( <( 0 z z deposited in the channels of small streams and on f loodplains, 6 ::> 0 - 0 0 "' ~ 0.. z 0 ~ 0 0 I I I I 0 S? 0 0 0 0 N M ... "' 6 and soil and colluvium developed on slopes bordering Babine Lake floodplains. Fans and deltas were built out into valleys and Wood from organic-rich silt at Babine Lake in central lake basins. British Columbia has yielded da tes of 42 900 ± 1860 Bessette Sediments from widely separated localities in and 43 800 ± 1830 years (GSC-16 57 and GSC-1687, southern British Columbia have been correlated using Harington et al., 1974, p. 287). 1v\am moth bone in t his s ilt tephrochronology (Westgate and Fulton, 197 5). Ten distinct was dated at 34 000 :!: 690 years (GSC-1754 , Harington et al., thin fine grained rhyolitic tephras have been recognized, and l 974, p. 287). On the basis of the palynological a nalysis of a each serves as a valuable isochronous stratigraphic marker. single sample of the si lt, Harington et al. (1974, p. 301) In order of increasing age these tephras are: Rialto Creek, c oncluded tha t the site, which is presently c overed by boreal about 20 000 years old; Cherryv ille, about 25 000 years old; forest, was in a shrub-tundra biozone at t he t ime t he Riggins Road, about 30 000 years old; Duncan Lake, about sediments were accumulating. This indicates a markedly 34 000 years old; Dufferin Hill and Sweetsbridge, probably colder c limate in this area about 43 000 years ago. Howeve r, close in age to Duncan Lake tephra; Kamloops Lake, s lightly additional paleobotanical work is required in central and older than 34 000 years; Mission Flats, probably older than northern British Columbia to substantiate the above 35 000 years; and Cout lee, older than 37 000 years; the age of conclusion. Okanagan Centre tephra is unknown. The source area of all these tephras is the Cascade Mountains of the Pacific At!in Region Northwest; many probably were derived from Mount St. Helens in Washington (Westgate and Fu lton, 1975, Weathering zones developed in drift in the Atlin region p. 500). of northwestern Br itish Columbia are thought by Tallman (1975) to have formed during an in terstade (the Pine Creek lntraglacial) which may correlate in part with the Paleoclimate O lympia nonglac::ial interval. This correlation is tenuous, Fossil animal and plant remains from Bessette however, in that radiocarbon dates of Olympia age that have Sediments suggest that the c limate in south-central British been reported for the region (M iller, 19 76, p. 48 1) a re in an Columbia during much of the Olympia nonglacial interval was unce1·ta in strat ig raphic context. Tallman (1 975) also not significantly different from that at p resent suggested t hat a glac ial event (Atlin I) occurred about 30 000 (Fulton, 1975a; Alley and Valentine, 1977; Alley et al., in to 40 000 years ago, im media te ly before the Pine Creek press). For example, during at least part of t he Olympia, the Intrag laciaJ. This is within the Olympia nonglacia l interval as climate was sufficiently warm and humid to support large defined for southern British Columbia. Unti l t he deposits of vertebrates such as Equus sp., Equus cf. c onvers idens, both the Pine Creek Intraglacial and Atlin I are better dated, Bison sp., and '.'.1ammuthus cf. columbi (Fulton, 197 5a, however, the occurrence of a glacial event in northwestern p. 16-17). Leaf impressions, wood fragments, and molluscs Br itish Columbia du ring Olympia t ime shou ld be viewed with also suggest climatic conditions similar to the present. caution. Palynological analyses of Bessette Sediments at the Duncan Dam borrow pit and at the type locality a t Bessette C reek Interior Plains suggest that: (!)the c limate was simi lar to or warmer than that at present in south-central British Columbia between Stratified sediments deposited before the Fraser about 25 000 and 42 000 years ago; (2) major c li matic Glaciation climax occur in the Fort St. John area near the deterioration accompany ing the onset of the Fraser western edge of the Interior Plains physiographic province Glac iation began about 25 000 years ago, but a fu ll glacial (Ma thews, 1963, 1978). A t ypical succession of these c limate was not attained until a bout 19 000 years ago (Alley sediments consists of a lower unit of gravel a nd minor sand, and Valentine, 1977; Alley et al., in press). overlain conformably by an upper unit of si lt a nd clay. The sediments occupy a buried interglacial valley system of Ava ilable evidence suggests that, whe reas t he c limate Peace River (Mathews, 1978, p. 5-6). The time involved in during the Olympia nonglacial interval in south-central cutting this valley system probably was much greater than British Columbia wa s for the most part similar to the that required for Peace River t o erode its postglacial t rench, pre sent, the Olympia climate in coastal sou t hwestern British because postglacial Peace Va lley is much smaller than the Colu mbia and northwestern Washington was somewhat cooler interglacial valley. t han at present. The reasons for this difference, if indeed it is real, are unknown. The gravel within the nonglacial succession in the Fort St. John area is similar in texture and provenance to Other Areas in the Interior System that on the present Peace River floodplain and was deposited by the ancestral Peac e River under aggrading conditions. Weathe ring zones and sediments that formed during the The fine gra ined sediments overlying the fluvial gravel were Olympia nonglacial interval also have been identified in the deposited as a result of aggradation and ponding of Peace Roc ky Mountain Trenc h, at Babine Lake, and in the River by glaciers advancing from the east (M athews, 1978, A tlin region. p. 8). The c ontact between these t wo units thus marks the transition from nong la c ial to proglacia l conditions Rocky Mountain Trench accompanying a ma jor expansion of the Laurentide Ice Sheet. The silt and c lay of the upper unit are capped by till Nonglacial sediments that correlate with Bessette deposited when the area fina lly was overriden by g lacier ice. Sediments occur in the southern Rocky Mountain Tre nch in This success ion of subtill stratified sediments likely was southeastern British Columbia and have been desc ribed by deposited during t he O lympia nonglacial interval and the Clague (1973, l 975c ). One radiocarbon date has been early part of the Fraser Glaciat ion. A radiocarbon date of obtained on these sediments (26 800 ± 1 ~88 years, GX-2032, 27 400 ± 580 years (GSC-2034, Ma thews, 1978, p. 17) was obt a ined on a mammoth tooth from nonglacial gravel beneath C lague, l 973, p. 258). Another Olympia date has been a postglacial river terrace near Fort St. J ohn. The dated obtained from inter till stratified sediments in the northern sediments at this site have been correlated with gravel Rocky Mountain Trench (25 940 ± 380 years, GSC-57 3, occurr ing elsewhere in the region beneat h silt , c lay, and till Lowdon e t a l., 1971, p. 298-299). These latte r sediments (Mathews, 1978, p. 8). Recently, however, some doubt has have been described by Rutter (1976, 1977).

7 been cast on the validity of this correlation as a result of new Clima t ic deterioration marking the transit ion from the radiocarbon determinations in Peace R iver valley west of Olympia nong lacial interval to the Fraser Glaciation probably Hudson Hope and in west-central Alberta southeast of occurred over a period of several thousand years. This Fort St. John. These dates, briefly discussed below, raise t he climatic change was accompanied by increased sediment possibility, but do not prove, that surface glacial deposi t s in production in mountain areas, leadi ng to aggradation a long the Fort St. John region predate both the Fraser Glaciation most rivers and streams. This period of fluvia l aggradation and the Olympia nonglacial interval. at the close of the Olympia nonglacial interval and during the early F raser Glaciation was preceded by a period during A mammoth tusk, found about I 3 km west of Hudson which most fluvial systems in British Columbia were either Hope in a large kame moraine marking the terminus of a stable or degrading, much as they are at present. major Cordilleran glacial advance or sti II stand, yielded a radiocarbon date o( > l l 600 years* U-2244A, Mathews, 1978, p. 17). On the basis of this date, both the kame moraine and FRASER GLACIATION Cordilleran glacial deposits farther east ha ve been assigne d a The Fraser Glaciation is the last major glaciation of Fraser Glaciation age. Recently, however, a larger sample of British Columbia, during which ice covered most of the the same tusk was dated at 25 800 ± 320 years (G SC-2859, province. In the Puget Lowland and in the Strait of Georgia Lowdon and Blake, 1979, p. 28). This latter date sugge sts, region, the Fraser Glac ia tion is subdivided into several lower among other things, the possibility that surface Cordilleran order, geologic-climate units, including the Evans Creek dritt east of the kame moraine was deposited during a Stade, Vashon Stade, Everson lnterstade, and Sumas Stade glaciation preceding the Olympia nonglacial inte rval, and (Armstrong et al., 1965). Several lithostratigraphic units that parts of the Interior Plains of British Columbia were ice have been establi shed which broadly correlate with these free during the Fraser Glaciation. The date, however, is geologic-climate units (Fig. 2) difficult to reconcile with the nearly contemporaneous date of 25 940 ± 380 years (GSC-573, Lowdon e t al., 1971, In south-central Br itish Columbia none of the above p. 298- 299) from nonglac ia l sediments 135 km to the west and uni ts have been recognized. Instead, all deposits of the much closer to the source of Cordilleran ice. This Fraser Glaciation are included in a single lithostratigraphic discrepancy raises t he possibility that the tusk was unit, Kam loops Lake Drif t. At a few localities elsewhere in contaminated** or redeposited (Lowdon and the Interior System, however, the last glaciation has been Blake, 1979, p. 28). subdivided into stades and interstades. For examp le, C lague (197 3, 197 5c) proposed three stades a nd two Radiocarbon dates from sediments in a high-level lake interstades for the southern Rocky Mountain Trench. in west-central Alberta 120 km southeast of Fort St. John Likewise, Rutter (1976, 1977) suggested that there were also bear on the age of the last glaciation of the Interior three glacier advances separated by two intervals of glacier Plains of British Columbia (White et al., 1979). A core of recession in the northern Rocky Mountain Trench. organic mud from this lake yielded four radiocarbon dates Tipper (J 971 a, b) presented evide nce for a late glacial spanning the period from 10 74 0 ± 395 to >30 000 years readvance following the Fraser Glaciation maximum in (WAT-362 and WAT-36 1, White et a l., 1979, p. 1873). These central British Columbia. Finally, Tallman (1975) outlined dates raise the possibility that this hilly area and thus, by for the Atlin region a complicated sequence of "glacials" and inference, the Fort St. John region escaped overriding by "interglacials" characterized by out-of-phase fluctuations of Laurentide ice du ring the Fraser Glaciation. This glaciers from different source areas. Two main stades and supposition, however, cannot be accepted without additional three lesser ones with intervening interstades were defined. field and laboratory stud ies because of: ( 1) the possibility of Unfortunately, a t none of the above localities in t he Interior contamina tion of the dated sediments, (2) the possible System are the g lacial events which have been recognized presence in the core of an unrecognized stratigraphic adequately duted. Thus, it is not possible at present to discontinuity which might indicate a period of ice advance, correlate these events within the British Columbia interior, and (3) the apparent youthfulness of glacial landforms at the nor to deduce their relationships to the better dated date locality (White et a l., 1979, p. 187 2- 1873). geologic-climate units of the Georgia Depression and Puget In summary, the age of surface glacial deposits in the Lowland . Interior Plains of British Columbia is uncertain. This, in turn, Sediments and landforms of the Fraser G lac ia ti on occur introduces doubt as to the age of stratified nonglacial throughout Br itish Columbia and are particularly prom inent sediments underlying ti ll in the Fort St. John a rea. These a nd widespread in vall eys, plateau areas, and t he coastal nonglac ia l sediments must be better dated in order to lowlands. In fac t, much of t he present landscape of British confirm t he ir Olympia age. Columbia is a product of glacial erosion and deposition during the Frase r G lacia tion. Summary At the close of the Olympia nonglacial inte rval, in The O lympia nonglacial interval is t hat portion of late response to c li matic cooling and perhaps increased Quaternary time in British Columbia be tween the Fraser precipitation, glaciers in the mountains of British Colu mbia Glaciation and the penultimate glaciation. During this advanced. With continued growth, they coalesced to for m interval a varie ty of nonglacial sediments were deposited piedmont glaciers and small mountain ice sheets. Eventuall y, within a geomorphic framework similar to t hat of post glacial piedmont co mplexes fro m sepa rate mountain source areas time. Most of these sediments accumulated in intermontane joined to cover most of the province. valleys, on coastal lowlands, and in offshore areas where they During the g lacier advanc:e phase of the Fraser are still preserved. Glaciation, the long-established Olympic drainage system was Although there is some uncertainty rega rding t he disrupted and rearrange d. P roglacial lakes formed in many climate of the Olympia nonglacial inte rval, temperatures a reas in front of the advancing g laciers, but e ventually were probably were at times similar to, and at times coole r than overriden. fee build-up also was accompanied by aggradation, those at present. Apparently, a lpine glaciers a t no time as outwash flooded into interior and coastal valleys from during the Olympia interva l expanded into the plateau and a lpine areas. The detai Is of these c hanges are not known in lowland a reas of southern and central British Columbia . most areas because much of the pertinent stratig raphic

* This date was incorrectly reported as 11 600 ± 1000 years by Bryan (1 969, p. 340) and Rutter (l 976, p. 433; 1977, p. 21 ). ** The tusk was coa ted with a hydrocarbon-based preservat ive (Krylon?) before the sample for GSC-2859 was obtained. evidence was removed by glacial erosion or was covered by evolved as glaciers down wast ed and retreated over the younger drift. In some areas, however, events of the Fraser Interior Pia teau. The glac io-isosta tically depressed coastal Glaciation advance pha se have been reconstructed, and low lands of the Western System were f looded by t he sea and details are prnvided in the following section. became sites of g laciomarine deposition. Floodplains throughout Br itish Columbia rapidly aggraded because rivers As the Cordilleran glarier complex expanded, its and streams were unable to cope with the large volumes of nourishment and su rface f low patterns became less controlled sediment made available during deglaciation. by ground surface topography and more rontrolled by ice sheet morpho logy (Dav is and Mathews, L944). It has been The pattern and history of deglaciation in British proposed t hat t he ice berame sufficien t l y thick over interior Columbia are murh better understood than are Fraser British Columbia for an ice dome to exist, w ith surface flow Glar ia tion advance events because the sediments and radially away from its centre (e.g. Dawson, 188 1; Kerr, 1934; landforms produced during deglaciation in most areas have Mathews, L9 55; Wilson et al., 1958; Fulton, 1967; Flint, 1971). not been removed by er osion or covered by younger deposits. lf this indeed happened, i t would have been accompanied by a rever sa l o f g lacier flow in the Coast Mountains, as the ice Fraser Glaciation Advance Phase divide (i.e., the axis of ou tflow) shifted from the mountain crest eastward to a position over the Interior Pla teau The advance phase of the Fraser Glaciation is defined (Flint, 197 l, p. 469). :\ comparable westward shi f t and here as the period from the close of the Olympia nonglac ial reversal of flow would have occurred in the Rocky Mountains. interval to the maxirn um of the Fraser Glaciation. During t his interva l, glaciers advanced from retracted positions in Tipper (1971 a, p.80; 197lb, p.749- 750), however, the mountains of British Columbia to cov er nearly the entire questioned t he existence of an ice dome over central British prov ince (Fig. 3). Columbia du ring the Fraser Glariation. He proposed instead that at the glacial maximum the Cordilleran lee Sheet r onsisted of coalescent piedmont g lar iers wh ich covered the Georgia Depression Interior System, but which wer e fed entir ely from alp ine As mentioned previously, the Fraser Glaciation in the centres. This conrlusion was based, in large part, on Lin St rait of Georgia region and Puget Lowland has been analysis of the regional pattern of drumlins, f lutings, and subdiv ided into the Evans Creek Stade, Vashon Stade, Everson striae in the Interior System. lnterstade, and Su mas Stade. The first two of t hese geologic ­ . evertheless, the possibility must be considered t hat climate units constitut e the advance phase of the Fraser the pattern of ice f low at the base of the Cordilleran Ice Glaciation. Sheet may have differed from that at the surface. The for mer was controlled largely by the topography of t he F.va ns Cr eek Stade terrain over which the ir e flowed. For example, most ice flow indicators shown on the Glacial Map of Canada Evans Creek Stade is "the climatir episode early in t he (Prest et al., l 968 ) indicate basal flow in conform ity with F raser Glaciation during which alpine g laciers formed and major physiographic elements. If the ice was thick enough t o reached their maximum extents ... " (Armstrong et al., 1965, cover high elevation terrain, however, surface flow may not p. 326 ). The ep isode was recogn ized in t he western Cascade have been topographica lly controlled and thus would not Mount a ins adjacent to Puget Low land where alpine drift is necessarily conform to the basal f low indicators. overlain by glaciolacustrine sediments deposited in a Jake Reconstru<":tion of the ice flow pattern at the surface of t he dammed by the Puget lobe of the Cordi lleran Ice Sheet. ice sheet at the peak of the Fraser Glac iation should be made From this stratigraphic succession, Crandell (1963, largel y by measuring h igh elevation str iae. From the p. A32-A36) inferred that the alpine glac ier had reached its observations that have been rnade, it appears that Fraser maximum extent and retreated far upvalley pr ior to the Glaciation ice in some areas indeed was thick enough t o Puget lobe attaining it s maxirnum stand dur ing the Vashon overtop high mount ain divides, thus suggesting that glacier Stade. nourishment and surface f low were controlled, at least for a The expansion of alpine glaciers in t he Cascade short time, by the ice sheet itself rather t han by substrate Mountains probably was contemporaneous with the initial topography (Prest et al., 1968). growth of t he Cordilleran glacier complex in the mountains Fraser Glaciation ire flow patterns were even 1nore of western British Columbia. Cont inued expansion of alpine compl icated than suggested above because f low varied with g !Liciers in British Columbia eventually led to the formation time in re la t ion to the stage of glaciation. Thus, flow of an ice sheet, whereas in Washington growth of alpine patterns of early Fraser t ime, w hen indiv idua l g lariers were glaciers was arrested and indi vi dual glariers r etreated before con fined to their va lleys, differed from those near the Fraser the Fraser Glaciation climax (Armstrong et al., 1965, p. 327). maximum when glaciers fror11 different source areas :\t t wo p laces in the Georgia Depression deposits of an coa lesced on t he plateaus and lowlands. Furthermore, during early Fraser Glaciation advance have been different ia ted the Fraser Glac iation, events of stadial-interstadial rank from those of the Vashon St ade. The low lands o f affected the extent of ice cover and complicated flow southeastern Vancouver Isl and are underlain by thick outwash patterns, at least near th<"' periphery of the ice sheet. gravels (Saanichton gravel) which Halstead (1968) attributed The pattern of glacial recession at the end of t he t o a pre-Vashon glacial advance in nearby Cowichan River Fraser Glaciation was not everywhere t he mirror image of valley. He correl ated this alpine glacial event with the Evans the pattern of glacial advance. In many areas of the Interior Creek Stade. Halstead, however, was unable to show System, deg laciation was c harac terized by widespread conclusively that the Cowichan Va lley advanc e occurred stagnation of tongues of ice in valleys a fter uplands berame significantly before or was in fact distinct from t he main ice free. This pattern of deg laciation rontrasts sharply with Vashon advance. There is no good evidenre for recession of a pattern of orderly frontal retr eat without stagnation, whirh the Cowichan glaci er prior to t he Vashon Stade; thus i t seems would occur if deg lariation was a m irror -image replica of icf' possible that the Cowichan Va lley and Vashon advances in build-up in these areas. this area were more or less in-phase. This casts doubt on the correlation of t he Cowic han Va lley advance with the Evans As was the case during the adv ance phase of the Fraser Creek S~ade . G laciation, rapid aggradation and ext ensive drainage changes occurred during deglariation. Large glacial lakes formed and

9 Jn Coquitlam River valley and the Fraser Lowland east 18700 :t 170years (GSC-2322, Lowden and Blake, 1978, of Vancouver, a Fraser Glaciation drift unit older than the p. 8-9; GSC-2 344, Armstrong, 1977 a, his Fig. I) on Vashon Drift has been reported by Armstrong and pre-Vashon organic sediments in the Fraser Lowland east of Hicock (1976), Hicock (1976), and Armstrong (I 977a, b). This Vancouver provide chronologic control on deglaciation of this unit, the Coquitlam Drift, apparently was deposited by alpine part of the lowland prior to the Vashon advance. glaciers advancing out of the Coast Mountains during the of recession following the early part of the Fraser Glaciation. Radiocarbon dates from The regional significance Coquitlam advance is unknown. A lthough Heusser (1972, Coquitlam Drift and correlative sediments range from of palynological evidence from 21 500 ± 240 to 21 700 ± 130 years (GSC-2536 and J973a, 1977), on the basis interval GSC-2416, Lowden and Blake, 1978, p. 8). At the time of this Olympic Peninsula, suggested that there was a brief 18 000 years ago, no stratigraphic advance in Coquitlam Valley, glaciers probably already of relative warmth about glacier occupied large parts of the Georgia Depression (Clague et al., evidence has been found of contemporaneous River 1980). However , after the Coqui tlam Valley glacier entered recession in the Georgia Depression outside Coquitlam the the Fraser Lowland and reached its maximum extent, it valley and the adjacent Fraser Lowland, despite s receded an unknown distance and the lowland became at least abundance of well studied exposures of Quaternary sediment slow, but partially ice free. Subsequently, the Fraser Lowland was in the region. Rather, the record indicates: (I) the glaciers in the Coast Mountains, completely inundated by ice during the Vashon Stade. progressive growth of in mountain valleys; followed by Radiocarbon dates ranging from 18 300 ± 170 to acrompanied by aggradation (2) the advance of glaciers down these va lleys and into the

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L EGE N D

EXISTING ICE FIELDS -mm 25.000 YEARS B p 20,000 YEARS BP. 0 50 100 lli\HHTIJ .._ I Kl LOMETRES 1...... 1 15.000 YEARS B. P.

Figure 3. Growth of the Cordilleran lee Sheet in southern British Columbia and nothern Washington during the Fraser Glaciation. Approximate glacier margins at 25 000. 20 000, and 15 000 years B.P. are shown. These positions have been determined from available radiocarbon dates and physiography and should be considered first approximations, subject to revision as additional data become available. The 15 000 year old margin is. in part, from Crandell ( 1965b) and Richmond et al. ( 1965) and is speculative off the west , north, and south coasts of Vancouver Island. Alpine glaciers in the Olympic and Cascade mountains outside the 15 000 year old boundary of the Cordilleran Ice Sheet and unglaciated areas within the confines of the ice sheet are not shown.

10 lowlands of the Georgia Depression, with aggradation As an interesting aside, it is worth mentioning that the occurring mainly on lowland floodplains; and (3) continued diachroneity of Quadra Sand causes difficulties in defining thickening and coalescence of glaciers to form a large the age of the boundary between the Olympia nonglacial piedmont lobe which advanced southeast down the Georgia interval and the Fraser Glaciation (Clague, l976b, Depression, outwash being deposited as a proglacial apron or p. 323- 324 ). According to the Code of Stratigraphic blanket fronting the advancing ice (Clague, 1976a, 1977a). In Nomenclature, the time boundaries of geologic-climate units such a scenario, the Vashon Stade, defined by such as the Olympia nonglac ial interval and the Fraser Armstrong et al. ( 1965, p. 327) as "the last major climatic Glaciation are defined from the dated boundaries of episode during which drift was deposited by continental ice stratigraphi(' units. In the Georgia Depression there are no originating in the mountains of the mainland of British isochronous lithostratigraphic units which can be used to Columbia and occupying the lowlands of southwestern British establish on a regional basis the age of the Olympia-Fraser Columbia and northwestern Washington", is not clearly boundary. A unique isochronous biostratigraphic boundary, separable from an early alpine stade in a regiona l sense. reflecting the regional climati(' changes accompanying the onset of the Fraser Glaciation, may yet be discovered and thus provide a suitable time horizon for the end of the Quadra Sand and the Growth of the Cordil!eran Ice Sheet Olympia nongla('ial interval and the beginning of the Fraser Proglacial outwash deposited in the Georgia Depression Glaciation. Unfortunately, insufficient work has been done and in some adjoining mountain valleys during the Fraser on the fossil plant and anima l assemblages of Quadra Sand Glaciation advance phase has been termed Quadra Sand by and the Cowichan Head Formation to know whether or not Clague (1976a, 1977a). Thi s prorninent lithostratigraphic such a time horizon indeed can be specified. unit, consisting of horizontally a nd cross-stratified we ll sorted sand, minor si lt and gravel, is underlain by the Vashon Stade and the Fraser Glaciation Climax Cowichan Head Formation and overlain by till and related glacial sediments (Armstrong and Clague, 1977). Quadra Vashon Stade glaciers did not completely cover the Sand has a wide, although patchy distribution in the Georgia southern Georgia Depression until after 17 000 to Depression and Puget Lowland*. Fyles (1963, p. 33) and 18 000 years ago. This conclusion is based on several radio­ Clague (J 976a, 1977a) proposed that the sand formed carbon dates on bone, wood, and peat underlying Vashon till, subaerially on floodplains which extended across or along the in c luding 17 000 ± 240 years from the Victoria area margins of what is now the Strait of Georgia. Clague (1977a, (GSC-2829, Keddie, 1979, p. 20); 17 800 ± 150 and p. v) further stated that the initial influx of Quadra Sand into 18 000 ± 150 years from Coquitlam River va lley (GSC-2297, the Georgia Depression: Lowdon et al., 1977, p. 15; GSC-2371, Lowdon and Blake, 19 78, p.8); 18300 ± 170, 18600 ± 190, and " .. . occurred during a period of c limatic 18 700 ± 170 years from western Fraser Lowland (GSC-2322, deterioration at the onset of the Fraser Lowdon a nd Bl ake, 197 8, p. 8-9; GSC-2194, Clague, l 977a, Glaciation. The sand was deposited, in p. 15; GSC-2344, Armstrong, 1977 a, his Fig. l ); and part, as distal outwash aprons at 19 15 0 ± 250 years from Cowichan River valley (GSC-21 O, successiv e positions in front of, and Dyck e t al., 1965, p. 36). perhaps along the margins of, glac iers moving from the Coast Mountains into As Vashon ice overrode the Georgia Depression, it split the Georgia Depression and Puget into two lobes near the southeastern end of Vancouver Island. Lowland during late Wisconsin time. One Job e fl owed south into the Puget Lowland and the other After deposition at a site, but before west-northwest along Juan de Fuca Strait towa rds the Pacific burial by ice, the sand was dissected by Ocean (Alley, 1974; Chatwin, 1974; Alley and Chatwin, 1979). meltwater and the eroded detritus was Gla

*The unit is called Esperance Sand in Washington (Mulline aux et al., 1965). ll Anderson (1967, 1968), on the basis of stratigraphic Other Areas in the Western System analysis of radiocarbon-dated cores from the seafloor of In the Western System outside of the Georgia western Juan de Fuca Strait, disputed this generally accepted Depression relatively little is known of the ice build-up phase view, stating that "there is no sedimentary evidence that the of the Fraser Glaciation. However, one date of Vashon 'Juan de Fuca' ice lobe penetrated to the Pacific 16 700 ± 150 years (GSC-2768, Clague et al., 1980) closely Ocean" ( 1968, p. 419). Instead, he suggested that Vashon ice deli mi ts Vashon Stade glacial occupation of the Estevan occupied only the eastern part of Juan de Fuca Strait, east of Coastal Plain on westernmost Vancouver Island. Another the vicinity of Victoria. This appears unlikely, however, in that the Puget lobe at the Vashon maximum terminated about date of 17 250 ± r~gg years (no laboratory dating number, 80 km south of Seattle (that is, about 280 km south of Anderson, 1968, p. 427) probably predates the Vashon advance Vancouver). In order for the Puget lobe to have reached this into Juan de Fuca Strait. far south, ice must have been quite thick in the vicinity of Victoria and, consequently, would have extended far to the It is likely that climatic deterioration at the beginning west of that city. Futhermore, the geomorphic and of the Fraser G!ariation produced similar effects throughout stratigraphic work of Bretz (1920) and Alley and the Coast Mountains. Thus, valley glaciers advanced and Chatwin (1979), among others, suggests that western mountain ice caps grew along the entire length of the Juan de Fuca Strait w;:is occupied by Vashon ice at the Fraser Western System. Glaciers flowing west off the Coast Glaciation climax. This ice, however, may not have been as Mountains advanced down fiords and spilled onto the thick as previous workers have suggested; if Anderson's data continental shelf. With continued thickening, the valley are valid, it is conceivable that the Juan de Fuca lobe was glaciers overtopped divides and formed coalescent ice masses not grounded in westernmost Juan de Fuca Strait at the covering much of the mainland coast. Fraser clima x. Glaciers also grew on the mountains of Vancouver Island and the Queen Charlotte Islands. For example, Paleoclimate glac iers flowing east and northeast off northern Vancouver Palynological investigations of early Fraser c...;1aciation Island coalesced with Coast Mountains glaciers to form an ice stream which flowed northwest along Queen Charlotte Strait. sediments in the Georgia Depression have been conducted by Alley (1979) and Mathewes (1979). Alley examined Quadra At the Vashon maximum, however, mainland ice possibly overrode northern Vancouver Island (Fl int, 1971, p. 469; Sand and related sediments on eastern and southern Vancouver Island. He concluded that between about 29 000 Howes, 1981, p. 10-11). At the Fraser climax, a small independent ice cap existed on the Queen Charlotte Islands. and 21 000 years ago there was a gradual deterioration in climate marked by the progressive replacement in lowland The eastern fringe of this ice cap may have coalesced briefly with mainland ice flowing west off the Coast Mountains. The areas of temperate plant speries with subalpine, and finally resulting piedmont complex perhaps covered what is now alpine or tundra vegetation. This supports the conclusions of Hecate Strait and flowed north and northwest into Dixon Clague (I 976a, l 977a) regarding the genesis and Entrance and southeast into Queen Charlotte Sound paleoclimatic significance of Quadra Sand. It also is in (Suthe rland Brown and Nasmith, 1962; Sutherland agreement with the finding of .\ilathewes (1979) at Vancouver; Brown, l 968). there, pollen assemblages in Quadra Sand dating 24 000 to 25 000 years include significant subalpine and minor alpine F!admark (1975, 1978, 1979) has argued for less components, indicating a colder climate than at present. extensive ice cover on the outer coast during the Fraser Glaciation. Specifically, he suggested that Hecate Strait was Palynological investigations on Olympic Peninsula not glaciated at the Fraser climax and that ice from the (Florer, 1972; Heusser, 1972, 1977 , 1978) and in the northern mainland and Queen Charlotte Islands last coalesced prior to Puget Lowland (Hansen and Easterbrook, l 974) have the Olympia nonglacial interval. He further proposed that important implications for early Fraser Glaciation events and much of the oute r continental shelf and the western fringe of paleoclimates in the Georgia Depression. On Olympic Vancouver Island were free of ice during the Fraser Peninsula climatic- deterioration associated with the Fraser Glaciation. This contradicts the generally held view Glaciation is interpreted to have begun about 28 000 years (e.g., Prest, 1969) that the Cordilleran Ice Sheet extended to ago. Between about 28 000 and 22 000 years ago, treeline in the outer edge of the continental shelf at the Vashon Stade the area fell, and the dominant plant community on the maximum. coastal lowlands changed from closed temperate forest to subalpine fore st. Towards the end of this interval, The controversy surrounding the extent of Vashon ice nonarboreal species became dominant in lowland areas. on the continental shelf and along the outer coast cannot be Heusser (e.g., 1972, p. 197; 1977, p. 294) thought that this satisfactorily resolved until the youngest drift sheet in these was due to incursion of tundra vegetation into the coastal areas is dated. However, early postglacial bog-bottom dates lowlands. Hansen and Easterbrook ( 1974, p. 598), however, from Langara Island at the nothern end of the Queen have commented that fossil pollen assemblages dominated by Charlotte group (Sutherland Brown, 1968, p. 34) and from the nonarboreal pollen may also result from a lowering of sea uplands of southern Vancouver Island (Alley and level, with the resultant expansion of grasses, sedges, and Chatwin, 1979, p. 1651-1652) support the concept of fairly herbs onto a former seafloor exposed during marine widespread Vashon ice along at least some parts of the outer regression. coast (see section entitled "Fraser Glaciation Recessional Phase" for details). A less complete pollen record from the northern Puget Lowland suggests that, as on Olympic Peninsula, a cool moist climate prevailed during the early stages of the Fraser Interior System Glaciation. Between about 28 000 and 23 000 years ago an open forest containing both lowland and subalpine species was The initial response to climatic deterioration at the onset of the Fraser Glaciation was the growth of alpine gradually replaced by what Hansen and Easterbrook (1974, p. 598) interpreted to be tundra vegetation. glaciers and mountain ice caps in the Coast, Skeena, Hazelton, Cassiar, Omineca, Columbia, and Rocky mountains. As in the Western System, this was accompanied by aggradation in valleys draining these mountain ranges. For example, thick gravel underlying Fraser Glaciation till in the

12 Fraser and Thompson river valleys in the southwestern lnterioc Plains Interior System probably was deposited during the early part The Interior Plains physiographic province in British of the F raser Glaciation. Aggradation here foll owed an Columbia probably was affect ed bot h by Cordil leran and interval of valley deepening (Ryder, 1976, p. I 3), which likely Laurentide glaciers during the Fraser Glaciation. Nonglacial coincided in part or wholly with t he O lympia nonglacial gravel in the Fort St. John area is overlain by sand, silt, and inte rval. c lay deposited when Peace River was blocked by advancing Glaciers eventually advanced beyond the mountains and Laurentide glaciers (Mathews, 1978, p. 8). Laurentide ice coalesced over the Interior Plateau. As mentioned flowed southwest into the area, bu t apparently was deflected previously, it is possible that a t the Fraser Glaciation in a broad sweeping curve south and then southeast by maximum one or more ice domes existed over the Interior Cordilleran glaciers flowing east and northeast. Plateau; however, during much of the Fraser Glaciation the The Laurentide and Cordilleran advances occurred ice sheet was a large piedmont complex nourished by glaciers approximately contemporaneously and are thought to be of flowing from the high mounta ins. Fraser Glaciation age. The e vide nce for this is tha t drift The ice sheet was hemmed in by t he Coast Mountains to deposited during these advances overlies nonglacial sediments the west and the Rocky Mountains to the east and was at that have been correlated with gravel near Fort St. John least 2300 m thick over valleys of the Interior Plateau dated at 27 400 ± 580 years (GSC- 2034, Mathews, 1978, (Flint, I 97 l, p. 469). Ice from this complex flowed out of the p. 17). Unfortunate ly, this correlation is somewhat tenuous Interior System through valleys transecting the mountain because the dated sediments are unconformably over lain by barriers. It also flowed south into nort hern Washington, postglac ial r iver gravel, rather tha n drift. Thus, t he age of Idaho, and Montana, and north into Yukon Territory the most recent coalescence of Laurentide and Cordilleran (Wilson et al., I 9 58; Richmond et al., 1965; Hughes et al., ice in the a rea remains somewhat uncertain, and the 1969; Prest, 1969). Ice flow ing north out of British Columbia possibility t hat coalescence last occurred prior to the Fraser was in contact with a lobe flowing west from the Selwyn Glaciation cannot be denied at present (see section entitled Mountains (Hughes et a l., 1969). "Inter ior Plains" in "Olympia Nonglac ia l Interval"). The last Cordilleran advance on the Plains may corre la t e with t he Several radiocarbon dates provide control on the timing Early Portage Mountain advance in the Rocky Mountain of glacia l invasion of south-central and southeast ern British Trench to the west (Fig. 2; Rutter, 1976, 1977). Columbia during t he Fraser Glaciation. A date of 19 100 ± 240 years (GSC-913, Lowdon and Blake, 1970, p. 72) A better-dated succession of nonglac ial sediments at the t ype sect ion of the Bessette Sediments near Lumby is overlain by Laurentide drift occurs at Watino, Alberta, closely related to initial glac ial occupation of that region 200 km east of Fort St. John. Wood and peat fro m this (Fulton, 1971, p. 8). Dates of 17 240 ± 330 and sequence have yielded radiocarbon dates from 27 400 ± 850 17 440 ± 330 years 0 -10,022 and I-J 0,021 , C lague e t al., to 43 500 ± 620 and >38 000 years 0 -4878, GSC- l 020, and 1980) from proglacial outwash near Trail further define GX- 1207; Lowdon and Blake, 1970, p. 69; Westgate et al., the Fraser advance. Five addit ional dates ranging 1972, p. 380); thus, at this site the last Laurentide advance from 19 900 ± 230 to 21 700 ± 240 years (GSC-1188 and clearly is of Fraser age. GSC-1 258, Low don e t al., 1971, p. 29 3-294) have been In addition to t he main Laurentide and CordilJeran obtained on subtill sediments at other sites in south-central glacial advances discussed above, Mathews (1978, p. 7-8, 14) and southeastern Brit ish Columbia, providing additional suggested that there may have been a less extensive evidence that the southern Interior Plateau was invaded Cordilleran advance of presumed early Fraser Glacia tion age re lative ly late by glaciers. One of these dates to the front of the Rocky Mountains. Sediments att r ibuted to (21 500 ± 300 years, GSC-l73, Dyck e t a l., 1965, p. 32) is this glacial event, however, were found at only t wo sites, and from sediments at a site only 35 km from one of the largest because Mathews could not definitely prove that these existing ice fie lds in the Rocky Mountains. This suggests t hat sediments were indeed of glacial origin, he was reluctant to alpine glaciers did not advance beyond t he western front of state unequivocall y that t he advance had occurred. t he Rocky Mountains unt il after about 21 50 0 years ago. Finally, a date of 19 100 ± 850 years (G X-2033, C lague, 1973, p. 258) was obtained on a peat c last within Summary Fraser Glac iation recessional outwash. The clast apparently The Fraser Glaciation advance phase bega n with was redeposited from sediments predating the last glacial c limat ic deterioration at t he end of the Olympia nonglacial advance, and the refore its age is limiting for this advance. interval and ended when the Cordille ran Ice Sheet attained The only radiocarbon date bearing on the Fraser its maximum size. Initially, glac ier growth was slow, and (Portage Mountain) advance in the northern Inte rior System many t housands of years elapsed before glaciers reached the is 25 940 ± 380 years (GSC- 57 3, Lowdon et al., 1971, lowland and plateau a reas outside the major mountain p. 298-299). This is a maximum limiting date, and the actual syst ems. Thus, although t he in itial climatic deterioration of advance may have occurred up to several thousand the F raser G laciation may have occurred as ea rly as years later. 29 000 years ago on the Pacific coast, most low land and plateau areas, a t least in southern British Columbia, we re ice Eastern System free until after 2 1 500 years B.P ., and some areas we re not covered by the Cordilleran Ice Sheet until about 17 000 years The chronology and characterist ics of the Fraser ago (Fig. 3). Glaciation advance phase in the Rocky Mountains of British Columbia are poorly known. It is noteworthy, however, that C limatic dete rioration and glacier growth were va lley glaciers probably did not advance beyond the Rocky accompanied by widespread rapid aggradation within river Mountain front until some time after about 21 500 years ago, valleys. Also, as glaciers advanced across the Interior even though t he initial climatic det erioration marking the Plateau, there were major drainage disruptions - many rivers onset of the Fraser Glaciation in nearby south-central British and streams changed courses and large ice-dammed lakes Columbia occurred a few thousand years earlier (Alley a nd formed. Valentine, 1977; Alley et a l., in press). It is li kely that g laciers in the Rocky Mountains advanced during the early phase of the Fraser Glaciation but remained confi ne d to the mounta in belt for several thousand years before spill ing into the Interior System.

13 Brief intervals of glacier recession ou-urred during the Georgia Depression Fraser Glac1at1on advance phase. Although these recessional The Cordilleran Ice Sheet reached its maximum extent events are known from several different areas in British in the Puget Lowland between 14 460 ± 200 and Columbia, their ages, climatic significance, and relationships ago (Y-2452, Heusser,1973b, p.289; to one another are not well established. J5000±400years W-1227, Mullineaux et al., 1965, p. 07). Northward retreat of the glacier lobe was accompanied initially by the Fraser Glaciation Recessional Phase development of proglacial J.:ikes in the southern Puget as Juan de Fuca Strait became The recessional phase of the Fraser Glaciation Lowland and later, marine waters into the area encompasses the time during which the Cordilleran Ice Sheet deglaciated, by the incursion of The Puget lobe had retreated to a disintegrated _after attaining its maximum size (Fig. 4). (Thorson, 1979, 1980). by 13 650 ± 550 years ago (L-346A, Climatic ameliorat1on resulted in down-wasting, stagnation, position north of Seattle p. 357). Radiocarbon dates from and _front_al retreat. Locally, rece ss ion was interrupted by Rigg and Gould, 1957, glacier st1Jl stands and minor readvances. glaciomar ine sediments deposited on the isosta tically depressed lowlands of the Georgia Depression indicate that deglacia tion was in progress there about 13 000 years ago (e.g., 12 900 ± 170 years, GSC-2193, Lowdon et al., 1977, p. 14; 12 800 ± 175 years, l(GSC)-248, Trautman and Walton, 1962, p. 36; 12 750 ± 170 years, GSC-418, Dyck et al., 1966, p. 113).

?

LEGEND

- EXISTING ICE FIELDS mill 10.000 YEARS B.P.

H))jH] 12 .500 YEARS B.P. 0 50 100 ._ I C=:J 15.000 YEARS B.P. KILOMETRES

Figure 4. Decay of the Cordilleran Ice Sheet in southern British Columbia and northern Washington during the terminal phase of the Fraser Glaciation. Approximate glacier margins at 15 000, 12 500, and 10 000 years 8. P. are shown. These positions have been determined from available radiocarbon dates and physiography and should be considered first approximations, subject to revision as additional data become available. The 15 000 year old margin is. in part. from Crandell ( 1965b) and Richmond et al. ( 1965) and is speculative off the west. north, and south coasts of Vancouver Island. Alpine glaciers in the Olympic and Cascade mountains outside the 15 000 year old boundary of the Cordilleran lee Sheet and unglaciated areas within the confines of the ice sheet are not shown.

14 Everson Interstade The above dates from the Fraser Canyon are a t the centre of a controversy concerning both t he source of the In coastal northwestern Wa shington and southwestern Sumas piedmont gJaciers and the timing of t he Sumas Stade British Columbia the interval of glacier recession between (Mathewes et a l., J 972). The following is a discussion and the Fraser Glaciation maximum and the Sumas advance is attempted resolution of this controversy. termed the Everson lnterstade (Armstrong et al., 1965; Armstrong, 1981 ). In practice, this interval is defined as The F raser Canyon during each major glaciation was an beginning when marine wate rs invaded the area, and as impor tant outlet for ice flowing into the Fraser Lowland ending in the eastern half of the F raser Lowland with the from the Coast Mountains and southern Interior Plateau. It advance of Sumas g lacie rs, and e lsewhere with the seems Jikely that the Sumas piedmont glacie r in the Fraser withd rawal of the sea from lowland areas and the Lowland was fed in part by ice flowing down this canyon. disappearance of f loating ice. Accordingly, the Everson Yet the three dates from the Fraser Canyon cited above Interstade began about 13 000 years ago and ended in the bracket the date for t he Sumas maximum in the Fraser eastern Fraser Low land about 11 300 ± I 00 years ago Lowland (1 1 300 ± 100 years, GSC-2523, Lowdon and (GSC-2523, Lowden and Blake, 1978, p. 7-8), the latter date Blake, 1978, p. 7-8), suggesting, at first glance, t hat the being the approximate time of the Sumas advance. The Sumas piedmont glacie r did not flow through the canyon. If Everson Interstade ended in the western Fraser Lowland and the error terms of the radiocarbon dates at two standard on eastern Vancouver Is land between about 10 000 and deviat ions from the mean are taken int o account, however, it J 1 300 years ago, when lowland areas became emergent is possible t hat the Sumas maximum in t he lowland was (Mathews et al., 1970; see also section entitled "Late Glacial attained up to about 300 years before sedimentation began in and Postglacial Sea Levels"). the higher lake, and up to about 800 years before sedi­ mentation commenced in the lower lake in the F raser During the Everson Interstade, a variety of sediments, Canyon*. The dates also a llow for t he possibility that there including glaciomarine diamicton, marine silt and clay, was up to 250 m of ice in Fraser Canyon at 11 430 ± 150 subaqueous outwash, and de ! taic sand and gravel, was years B.P. a nd up to 150o m f ice at 11 140 ± 260 years B.P. deposited on submerged coastal lowlands in the Georgia Neverthe less, if t he Fraser Canyon was an important supplier Depression (e.g., Armstrong and Brown, 1954; Fyles, J 963; of Sumas ice, the Sumas piedmont glacier must have receded Armstrong, 198 1). These sediments exhibit complex facies extremely rapidly, on the order of 50 to 100 km in no more changes due to spatia l differences in sediment supply during than 300 years, even if residual ice persisted at low deposition and to differences in the rate and nature of g lacier elevations in the canyon until about l J 000 years ago. recess ion within the area. These complexities preclude subdivision of Everson lnterstade deposits, which collectively An a lternative explanation is t hat the piedmont g lacier are referred to both as the Fort Langley Formation and was not nourished by F raser Canyon ice. Alternativ e sources Capilano Sediments (Armstrong and Brown, 1953; Fyles, 1963; inc lude valleys ente ring the Fraser Lowland from the Armstrong, 1976, 1977a, b, 198 1). Cascade Mountains and one or two major valleys entering the eastern F raser Lowland from the Coast Mountains. However, at least the former are precluded because their lower reaches Sumas Stade were deglaciated while the adjacent Fraser Lowland was The Everson Interstade ended in the eastern Fraser buried by ice. In one such valley, for example, deltaic Lowland wi th a readvance of glaciers. Armstrong et al. sediments were deposited in a lake dammed by ice in the (1965) a ttributed this readvance to a climatic e pisode which Fraser Lowland about I J 800 ± 100 years ago (GSC- 2966). they called the Sumas Stade. Sumas Drift overlies the Fort The lower part of this valle y remained ice free at the c limax Langley Formation over an area of about 650 km 2 in t he of the Sumas Stade and thus did not supply ice to the Sumas eastern Fraser Lowland (Armstrong e t a l., 1965, p. 329). piedmont g lacier in the F raser Lowland. Another argument Because the drift is not overla in by mar ine sediments, much against such alternative sources of Sumas ice is t hat it is of the Fraser Lowland had emerged by isostatic rebound prior unlike ly that the Fraser Canyon was ice free at a t ime when to t he end of the Sumas Stade. nearby valleys supported large active glaciers. The climax of the Sumas Stade was about In conclusion, with evidence presently available, it 11 300 ± JOO years ago (GSC- 2523, Lowdon and Blake, 1978, appears that the Sumas piedmont g lacier receded rapidly out p. 7-8). This date was obtained on wood embedded in Sumas of the Fraser Lowland immediately aft er it reached its till. Radiocarbon dates on wood and shells from the under ­ c limax position. By 11 000 years ago, the lowland probably lying Fort Langley Formation substantiate this age was completely free of glacier ice. assignment. Several investigators have identified sediments and Several radiocarbon dates bear on the timing of retreat landforms of probable Sumas age outside the Fraser Lowland, of Sumas glaciers. A date of 9920 ± 760 years (l-2280, although, in most cases, the lack of radiocarbon dates Easterbrook, 1969, p. 2285) was obtained on peat at the base prec ludes their definite assignment to the Sumas Stade. of a bog developed on Sumas outwash in Washington State Mathews et al. ( 1970, p. 696) stated that a large submarine JU St south of the International Boundary. Sumas ice had moraine in Howe Sound north of Vancouver marks a maximum withdrawn fro m its maximum position, and the outwash stand of Sumas ice. Halstead (1968, p. 1413) proposed that surface became inactive before this date. Three radiocarbon ice-contact sediments in Cowic han River valley were dates from postglacial sediment s beneath two lakes in the deposited during a glacier stillstand resulting from climatic lower F raser Canyon suggest earlier recession of Sumas ice. cooling of the Sumas Stade. Crandell ( i 965b, p. 347) Dates of 11 430 ± J 50 and I J 000 ± J 70 years 0 -6057 and correlated the climatic episode responsible for the I-5346, Mathewes et al., 1972, p. 1057) were obtained on rejuvenation of small glaciers in the Cascade Mountains of basal organic sediments in two cores from one lake at an Washington at t he end of the F raser Glaciation wi t h the elevation of approximately 320 m. A third date of Sumas Stade. Finally, Porter (1976, p. 73) dated t he Hyak 11 140 ± 260 years 0-6058, Mathewes e t al., 1972, p. 1057) adva nce in the North Cascade Range as no more than several was obta ined on organic sediments in another lake at an centuries older than 11 050 ± 50 years (UW-321), and, on this elevation of about 205 m, less than 160 m a bove the bedrock basis, t e ntatively correlated it wit h the Sumas Stade. f loor of the Fraser Canyon. Together, the dates indicate that the Canyon conta ined little or no ice after 11 000 years ago.

* Error ter ms for Teledyne Isotopes' dates, inc luding 1-6057, I-6058, and 1-5346, are le; the error term for GSC-2523 is 20. In some areas readvances at the end of the Fraser Vancouver Island Ranges Glaciation do not correlate with the Sumas, thus raising some On southern Vancouver Island deglaciation proceeded doubt concerning the climatic significance of the latter. mainly by downwasting. Most upland areas were free of ice Alley and Cha twin (1979) presented evidence for resurgence down to an elevation of 400 m before 13 000 years ago (Alley of ice in Juan de Fuca Strait and in upland areas of southern and Chatwin, 1979, p. 1652). As mentioned previously, a Vancouver Island prior to the Sumas advance in the Fraser minor resurgence of glaciers occurred in this area before Lowland. In contrast, Armstrong (l 966b) found evidence for deglaciation was complete. Following this readvance, down­ a local readvance in the Coast Mountains near Terrace wasting continued, and glacier-dammed lakes formed in most between JO 420 ± l60 and JO 790 ± 180 years B.P. (GSC-535 major valleys. With melting of residual ice, these lakes and GSC-523, Lowdon et al., 1967, p. 174), well after the drained and the postglacial drainage pattern quickly became Sumas advance in southwestern British Columbia. Finally, established. Sutherland Brown (1968, p. 34) proposed that final disengage­ ment and recession of mainland and insular ic e on the Queen Charlotte Islands was followed by a readvance on the Queen Charlotte Islands lowlands of northeastern Graham Island near the end of the An extensive outwash plain was constructed adjacent to Fraser G Jaciation*. This readvance occurred before a fairly stable ice front on northeastern Graham Island during 13 700 ± 100 years B.P. (GSC-3222), which is a minimum a glacial advance or stillstand thought to be of late Fraser deglaciation date for Graham Island, and thus is substantially age (Sutherland Brown, 1968, p. 34; however, see older than the Sumas Stade. Fladmark, 1975, p. 125-126, for a different interpretation of It is apparent that glacier stillstands and minor the age of this feature). Following construction of this readvances occurred at many different times during the sandur, glaciers on the Queen Charlotte Islands downwasted recessional phase of the Fraser Glaciation and likely were and receded. Lowland areas were ice free before controlled more by local conditions than by global or regional 13 700 ± 100 years B.P. (GSC-3222), which is the age of climatic change. The Sumas advance, for example, may have mosses underlying a peat bed and postglacial marine been caused by a change in glacier regimen due to isostatic sediments on northeastern Graham Island. uplift of lowland areas. As the sea regressed from the Fraser Lowland, glaciers which formerly calved into the sea became Northern and Central Mainland Coast grounded on land. This si tua ti on would favour a re advance similar to the Sumas which would not be climatically control­ Minimum dates for deglaciation of the mainland coast led. If the Sumas advance indeed occurred without climatic east of the Queen Charlotte Islands are 12 700 ± 120 years cooling, the terms "Sumas Stade" and "Everson lnterstade" (GSC-2290; Lowdon and Blake, 1979, p. 25) at Prince Rupert would have to be abandoned as geologic-climate units. and 12 210 ± 330 years (GSC-1651, Lowdon and Blake, 1973, p. 27) near Bella Bella. Deglaciation occurred later, however, at the heads of fiords extending into the Coast Paleoclimate Mountains. For example, the major mountain valley between Climatic conditions in the Georgia Depression and Terrace and Kitimat became ice free between about 10 500 adjacent regions during the recessional phase of the Fraser and 11 000 years ago (Armstrong, l 966b). The northward Glaciation have been reconstructed from palynological data retreat of the tongue of ice in this valley was interrupted by Heusser (1973a, b, 1974, l 977), Mathewes (1973a, b), several times by stillstands or minor readvances which Hansen and Easterbrook (1974), and Mathewes and probably had little or no regional climatic significance. Rouse (197 5). Some amelioration of climate must have During these stillstands, large volumes of gravel and sand occurred from about 15 000 years ago onward to promote the were deposited as ice-contact and proglacial deltas in an arm rapid retreat of glaciers and to encourage the revegeta ti on of of the sea extending inland from the present fiord head at freshly exposed terrain. Heusser ( l 977, p. 300-301) proposed Kitimat. Also, thick marine and glaciomarine muds were that mean July temperatures on Olympic Peninsula during the deposited under lower energy conditions on the floor of this recessional phase of the Fraser Glaciation were about 2 to submerged valley (Duff ell and Souther, 1964, p. 8-1 O; 5°C lower than present. According to Heusser, minor Armstrong, I 966a, b; Clague and H icock, 1976). Al though the climatic amelioration during the Everson lnterstade, when pattern of deglaciation in the Terrace-Kitimat area was mean July temperatures reached to within 2°C of the similar to that in the Fraser Lowland, the timing of events present, was followed by cooling during the Sumas Stade. differed in the two areas, and there is no evidence at About 10 500 years ago, closed temperate forest communities Terrace-Kitimat for a climatic episode equivalent to or even became established in low land areas, subordinating or comparable with the Sumas Stade. replacing pioneer species and those adapted to cooler, more moist conditions (Mathewes, l 973a, p. 2099). Interior System Style and Pattern of Deglaciation Other Areas in the Western System The style of deglaciation in areas of moderate relief in Studies of deglaciation in areas of the Western System the Interior System has been summarized by Fulton (1963, outside the Georgia Depression include those of: (I) the 1967, 1971). He proposed that deglaciation at the close of southern Vancouver Island Ranges (Alley, 1974; the Pleistocene occurred largely by down wasting, Chatwin, 1974; Alley and Chatwin, 1979); (2) the Queen accompanied by stagnation and complex frontal retreat from Charlotte Islands (Sutherland Brown and Nasmith, 1962; the southern and probably northern sectors of the Interior Sutherland Brown, 1968; Nasmith, 1970; Alley and System. Fut ton (1967, p. 28) further suggested that Thomson, l 978); (3) the Bella Bella - Bella Cool a region of deglaciation proceeded through four stages: (I) active-ice the central British Columbia coast (Retherford, 1972; phase - regional flow continued but diminished as the ice Andrews and Retherford, I 978); and (4) the Terrace-Kitimat­ thinned; (2) transitional upland phase - highest uplands Prince Rupert region of the Coast Mountains (Duffell and appeared through the ice sheet, but regional flow continued Souther, 1964; Armstrong, I 966a, b; Clague and Hicock, 1976; in major valleys; (3) stagnant-ice phase - ice was confined to Clague, l 977b). valleys but was st ill thick enough to flow; and (4) dead-ice phase - valley tongues thinned to the point where plasticity was Jost. This model, which is based on deglacial deposits

* Flad mark (e.g., I 97 5, p. I 25-126), however, argued that this "readvance" did not occur during the recessional phase of the Fraser of the Fraser Glaciation, but rather represents the Fraser climax. and landforms in south-central British Columbia, has been in central and sou th-cen tral British Columbia, these lakes are used with minor modifications to describe deglaciation of of considerable importance because they provide evidence parts of the sou th western Interior System \Ryder, l 976) and that valley glaciers in the Rocky and Columbia mountains in the central Interior Plateau (Heginbottom, l 972; southeastern British Columbia receded prior to the trunk Tipper , 197la, b; Howes, 1977). glacier in the adjacent Rocky Mountain Trench. Ice in the Rocky Mountain Trench blocked the drainage in the tributary On a regional scale, ice receded trom hilly uplands valleys and thus impounded the lakes. The glacier dams while stagnant, c limatirally dead ice remained in the major repeatedl y failed, producing floods which swept south down valleys and basins. In the southern Interior System, for the trench into .'v\ontana. example, the southern Columbia Mountains appeared above the surface of the ice sheet before the lower Okanagan There were lakes in the northern Rocky Mountain Highland to the west; the Okanagan Highland was deglaciated Trench during the recessional phases of both the Early and while an ice tongue remained in adjacent Okanagan Valley; Late Portage Mountain advances*. The older (Early Portage and the hilly Thompson Plateau became free of ice while the Mountain) lake was overriden by ice during the Late Portage lower Fraser Plateau to the north remained covered Mountain advance. The younger \Late Portage Mountain) (Fu! ton, J 97 I, p. 16). Likewise, as the ice sheet thinned over Jake perhaps was continuous for a short time with Lake Peace the central Interior Plateau, it "lost its mobility over wide on the Interior Plains (Rutter, 1976, 1977; Mathews, 1978); areas, broke up into blorks lying in small valleys, stagnat ed, however, as the former expanded during the westward retreat and decayed" (Tipper, 1971 b, p. 7 50). As stagnation and of Cordilleran ice, the level of the latter dropped due to the decay replaced active flow over more and more of the eastward retreat of the Laurentide Ice Sheet. Lacustrine rentral [nterior Plateau, the anive ice sheet probably conditions apparently persisted in the Rocky Mountain Trench degenerated to a piedmont apron skirting the Coast and atter Lake Peace disappeared from the Interior Plains of Car iboo mountains. British Columbia, perhaps because of blockage of Peace River valley at the eastern front of the Rocky ln summary, at the close of the Fraser Glaciation, the Mountains by morainal or colluvial deposits (Rutter, 1977, Cordi lleran Ice Sheet in the Interior System thinned and p. 2 l) or because of regional differential isostatic uplift. The receded in a complex and irregular manner. In areas of low final drainage of ldkes in the trench and the establishrnent of and modera te relief frontal retreat was accompanied by the postglacial drainage system of Peace River may not have stagnation, with uplands appearing through the ice cover and occurred until after 9280 :!: 200 years t'>.P. (GSC-1497, dividing the ice sheet into a series of valley tongues which Rutter, 1976, p. 431). retreated in response to local conditions. Active ice eventually became restricted to the major mountain systems, locally as piedmont complexes, but in most areas as valley Chronology of Deglaciation glaciers. These glaciers continued to recede, such that by The chronology of deglaciation of parts of the Interior early postglacial time, ice cover in British Columbia was System is known with some assurance. At its southern about the same as, or less extensive than it is today. margin in north-central and northeastern Washington, the During deglac1ation, as during the Fraser advance, Cordi lleran Ice Sheet began to retreat before 13 000 years there were, at least locally, glacier stillstands and ago, the time when floodwaters of glacial Lake Misoula last readvances. Tipper tl 97 la, b) proposed a late Fraser poured across the Channeled Scabland and through the canyon resurgenre of ice in the Coast and Cariboo mountains, during of the Columbia River \Mullineaux et al., 1978). The which glaciers reoccupied part of the central Interior Plateau Okanagan lobe on the Columbia Plateau in Washington had but did not JOin to form a single ire sheet. Late Pleistocene retreated at least 80 km from its maximum stand by the time readvances also have been proposed for the southern Rocky Glacier Peak tephra layer G was deposited approximately \l\ountain Trench ("late stade" of Clague, 1973, l 97 5c), the 12 750 :!: 350 years ago (W-1664, Ives et al., 1967, p. 517; northern Rocky Mountain Trench ("Late Portage Mountain" Porter, 1978, p. 38-39 ). However, the absence of layer G advance of Rutter, 1976, 1977), and the A tlin area of north­ from a substantial area of northern Washington within the western British Columbia ("Atlin III, IV, V" and "Gladys Ill" of projected zone of tephra fallout indicates that the margin of Tallman, 1975). Because these events, in general, are not the ice sheet in most areas was south of the International adequately dated, their relationships to one another and to Boundary about 12 7 50 years ago. the Surnas advance are not known. Harrison \l 976a) suggested that the southern Rocky Mountain Trenrh near the International Boundary was Glacial Lakes deglac1ated before about 12 200 years ago. The basis for this suggest ion is two radiocarbon dates of 11 900 :!: l 00 and In many parts of the Interior System deglac1ation was 12 200 :!: 160 years (GSC-2142 and GSC-2275, Lowdon and accompanied by the formation of glacial lakes in which large Blake, 1976, p. 9) on postglacial sediments in Elk River quantities of silt and clay were deposited. The most valley, which is tributary to the Rocky Mountain Trench. extensive lakes formed on the central Interior Plateau Harrison thought that the dated sediments were deposited (A rmstrong and Tipper, 1948; Tipper, l97Ja) and in valleys of after the final drainage of glacial Lake Elk, which had been south-central British Columbia (Mathews, l 944; dammed by Rocky .'v\ountain Trench ice. Thus, in order for Nasmith, 1962; Fulton, 1965, 1969). Those on the central the lake to drain, the southernmost trench would have to Interior Plateau were dammed behind ice receding south out have been ice free. of the Fraser Basin. L akes in south-rentral British Columbia, on the other hand, were ponded behind stagnant and dead ice Although there is no reason to question the above and drift left as the active ice front receded north towards evidence for initial deglaciation of some lowland areas in the Fraser Plateau. The evolution of the glarial lakes in interior British Columbia prior to 12 000 years t'>.P., the south-central British Columbia has been documented in oldest reliable postglacial radiocarbon age obtained to date in considerable detail by studying shorelines, outlet channels, the Interior System north of the International Boundary is lacustrine deposits, and ice-marginal features (e.g., see 11 000 :!: 180 years (GSC-';109, Lowdon and Blake, 1970, Mathews, 1944; Fulton, l 969). p. 71). Bog-bottom dates in the Interior System, in general, become younger towards the west \Fulton, 1971, p. 17), Glacial lakes also formed in tributary valleys to the perhaps reflecting later deglaciation of the Coast Mountains. southern Rocky Mountain Trench during deglaciat10n (Clague, 1973, 1975a). Although small in comparison to those

* Both advances have been assigned to the time period of the rraser Glaciation (Rutter, l 976, 1977). 17 By 9500 to 10 000 years ago, the plateaus and valleys of glacial Lake Peace were recognized by Mathews. During the interior were completely deglaciated, and ice was each successive stage, lake levels were tied to lower outlets restricted to the major mountain ranges. ~og-bottom controlled by the Laurentide Ice Sheet which was down­ sediments immediately outside the terminus of present-day wasting and retreating to the east. Tiedemann Glacier in the southern Coast Mountains dated From a study of strandlines and associated glacial 9510 ± 160 years (GSC-939, Lowdon et al., 1971, p. 300), features, Mathews related the evolution of Lake Peace to indicating that the mountains in that area were as free of ice recession of Cordilleran and Laurentide glaciers. During the then as they are now. A date of 9315 ± 540 years (GX-2695, earliest stage of Lake Peace, the Cordilleran glacier in Peace Reeburgh and Young, 1976, p. 12) from the Atlin area is a River valley terminated at the Rocky Mountain front west of minimum for deglac1ation of the northern Interior System Hudson Hope and built an end moraine consisting of del taic near the front of the Coast Mountains. deposits into the lake. During a later stage, when the Rutter et al. (I 972) and Rutter (1976, 1977) concluded Laurentide glacier dam was east of the British that there still was ice in part of the northern Rocky Columbia - Alberta boundary, the Cordilleran glacier Mountain Trench after 9280 ± 200 years B.P. (GSC-1497, probably terminated in Peace River valley about 40 km west Rutter, I 976, p. 431). This date was obtained from a bighorn of the Rocky Mountian front (Mathews, 1978, p. l6). After sheep skull in what were interpreted to be ice-contact Lake Peace drained, there was a minor late glacial readvance gravels. If the stratigraphic interpretation is correct and the in the Rocky Mountains; however, glaciers did not extend radiocarbon date valid, ice lingered in this area after it had beyond the mountain front. disappeared from other interior localities. Nevertheless, it A few radiocarbon dates help fix the termination of seems improbable that glaciers occupied areas far distant glaciation in the Peace River region. A date of >I I 600 years from their sources in the Cassiar, Omineca, and northern 0-2244AJ, determined on the collagen fraction of a mammoth Rocky mountains at a time when glaciers in the Coast and tusk recovered from the end moraine near Hudson Hope, was southern Rocky mountains were not much larger than they interpreted by Mathews (1978, p. i 7) to be a minimum for are at present. It thus is concluded that the chronology of retreat of Cordilleran ice westward into the deglaciation in the northern Rocky Mountain Trench proposed Rocky Mountains*. A corrected date of 9960 ± 170 years by Rutter may require revision. (GSC-1548, Lowdon and Blake, 1973, p. 28), previously incorrectly reported as 16 300 ± 180 years lReimchen and Eastern System Rutter, 1972, p. 177 ), and another of l 0 400 ::t 170 years (GSC-1654, Low don and Blake, 1973, p. 28) were obtained Al though considerable work has been done on deglac1al near Dawson Creek on shells from silts deposited either in a sediments and landforms in the Rocky Mountains of Alberta late stage of Lake Peace or in local ponds which postdate the (e.g., Jennings, 195 I; Horberg, l 954; McPherson, I 963, l 970; lake. Other dates from bog and Jake bottoms, proglacial Nelson, J 963; Rutter, I 966a, b, c, J 969, l 972; Stene, I 966; lac us tr ine sediments, and younger fossi Ii f erous si Its in the Wagner, l966; Roed, 1968, 1975; Boydell, 1970, 1972, 1978; Swan Hills area about 240 km southeast of Fort St. John Walker, L97l, 1973; Alley, 1972, 1973; Harris and indicate that much of north-central Alberta was deglaciated Boydell, 1972; Shaw, 1972; Stalker, 1973; Alley and before about 11 500 years ago, with some areas ice free Harris, 1974; Waters, 1975; Harrison, l 976b; Harris and perhaps as early as 13 500 years B.P. (St-Onge, 1972, p. 8). Waters, 1977; Jackson, 1977, 1980; Stalker and Harrison, 1977), relatively little is known of deglacial events in that portion of the Rocky Mountains in British Columbia. Summary Geomorphic and Quaternary stratigraphic studies, however, Deglac1ation in British Columbia proceeded by have been conducted in Peace River valley (Rutter, I 976, downwasting accompanied by stagnation and frontal retreat. 1977), Yoho National Park and vicinity (Bement, 1972; Topography controlled the pattern of deglaciation in each Fox, 1974), and Elk River valley (Harrison, l 976a). region, and hilly uplands became ice free prior to major Harrison's work in Elk River valley is of particular valleys and basins. As downwasting progressed, terminal importance in terms of the timing of deglac1ation in zones of the ice sheet became divided into a series of valley the southern Rocky Mountains. Radiocarbon dates tongues which retreated in response to local conditions. of 11 900 ± JOO and 12 200 ± 160 years (GSC-2142 and Retreat occurred first along the southern, eastern, and GSC-227 5, Lowdon and Blake, L976, p. 9) from postglacial western margins of the Cordilleran Ice Sheet in British sediments in this valley near the centre of the southern Columbia about 13 000 years ago. Although there were Rocky Mountains indicate deglaciation before about short-lived stillstands and minor readvances, deglaciation 12 000 years ago. The site from which these radiocarbon progressed rapidly, for by about 9 500 years ago glaciers were dates were obtained is less than 50 km downstream from little more extensive than they are today. existing glaciers of some of the highest peaks in the southern Rockies. If these dates are valid, late Pleistocene glaciers in Deglaciation was accompanied by marine inundation of this region must have retreated back to within a few tens of coastal lowlands, by the growth and decay of ice- and drift­ kilometres of the Continental Divide prior to about dammed lakes, by widespread aggradation in valleys, and by 12 000 years ago. The location of the samples, however, does the establishment of the present drainage network. not rule out a later, limited alpine readvance in Elk River valley upstream of the sample site, and, in fact, such a late POSTGLACIAL glacial event has been recognized in valleys elsewhere in the Rocky Mountains (e.g., the Eisenhower Junction advance in Postglacial includes the time since the disappearance of Bow River valley, Alberta; Rutter, 1969, 1972). ice of the Fraser Glaciation. The deposits of this interval formed in response to processes that, in general, remain active in British Columbia today, although erosion and Interior Plains sedimentation in most areas presently are occurring at much A series of glacier-dammed lakes (Lake Peace) were slower rates than during late glacial and early postglacial impounded by decaying Laurentide ice in the Peace River time. region of the Interior Plains physiographic province (Taylor, 1960; Mathews, 1963; 1978, 1980). Four stages of

* This tusk recently has been redated at 25 800 ± 320 years (GSC-2859), indicating either that the end moraine is older than previously thought, that the sample was contaminated, or that the tusk was recycled from Olympia-age sediments (Lowdon and Blake, 1979, p. 28). Patterns of Sedimentation and Erosion Colluvial sediments, including talus, slopewash, and landslide material, are found throughout British Columbia but n uring and immediately following deglaciation, and are most common in areas of moderate and high relief. A befor e veget a tion became firml y established , rapid wide variety of landsl ide types occurs in t he province, of aggradat1on occurred 1n r iver valleys and on lowlands. In whic h many have been described and discussed. Among these coastal areas thick marine and glac1omarine sediments were are various rockfalls and rock t opples (e.g., Pi teau, 1977; deposited on isost atically depressed lowlands vaca ted by \i\a thews, 1979 ); rockslides and rockfall avalanches retreating glaciers and cover ed by the sea. Throughout the (e.g., Mathews and McTaggart, 1969, 1978; Ei sbacher, 197 l ; province, freshly deglaciat ed drit t was eroded from uplands Moore, 1976; Moki evsky-Zubok, 1977; Alley and Young, 1978; and valley wall s and was transported to lower elevat ions to Moore and Mathews, 1978); "sackung" (sags) and gravitational be deposited in fans and deltas and on floodplains (Church and spreading features (e.g., Piteau et al., 1978; Psutka, 1978; Ryder , 1972). I t is probable that t he bulk of postglarial P>rown and Psutka, 1980); debris f lows (e.g., Ryder, 1970, deposits, except in lake basins and at the mout hs of major l 97 l a, b; O'Loughlin, 1972, 1973; A lley and Thomson, 1978; r ivers, were laid down w ithin a f ew hundred year s following C lague, l 978b; Jac kson, 1979; Nas1n i th and Mercer, 1979); deglaciation. Deltaic prograda tion of the F raser, Skeena, and earthflows (e.g., Stanton, 1898; VanDine, 1974 , 1980; other lar ge river s occurred t hroughout post g lacia l t ime and Sk ern1er, 1976; C lague, I 978b; L uternauer and Swan, 1978; continues today on a large scale (e.g., Johnston, 192 1; Swan, 1978; Swcin and L uternauer, 1978); and earth and rock \l\athews and Shepard, 1962; Luternauer and lvlurray, 1973). slumps. As slopes stabilized and vegetation berame established, Eisbacher ( I 979) has shown that t he landslide char­ sed iment supply to streams and r ivers decreased. Together acteristirs of each major physiographic region of British w ith a fall in base level due to g lac10- isostatic: upl ilt and Columbia are unique, due to differ ences in topography, resultant changes in land-sea positions, t his led t o entrench­ c limat e, and, possibly, seismicity. L andsl ides in t he Coast rnent and t erracing of lat e glacial and older deposits. and Insular mountains are mainly roc: kfalls, rockslides, debr is This pat tern of aggr adation in late glacial and early flows, and earthflows; those on the Inter ior Plateau are postglaci;.il time, followed by degradation, occurred in most chiefly slumps, debr is flows, and earthllows; deep-seated regions of the province. For example, the F raser and slope sagging and gravitational spreading are dominant in the T hornpson rivers in sou t h-centr al and sou thwest ern British mountain ranges of the Interior System; landslides in the C olumbia locally are incised up to 300 m below late glacial, Rocky Mountains '-Ire m ainly rockfall avalanches and debris l ac: ustrine, and outwash surfaces (Ryder , J97 l a, p. 1254-1255; f lows; finally, n1os t land slides in the Inter ior Plains are see also A nderton, 1970 , p. 69 - 70). Lik ewise, Peace Ri ver softrock slumps and earthflows. and its tributaries on the Interior Plains flow in deep Volumetrically small, but st ra tigraphically importan t postglaci al va lleys (Beach and Spi vak, 1943; beds of tephra occur in many parts of British Columbia. 1\1\athews, l 961, 1978). Tephra is preser ved only where erosion was not ocur ring Eolian sedimentation, like f luvial aggrada tion, occurred during a volcanic eruption. Where tephra was deposi ted on a 1r1ainly during late glacial and early post glac ial time flat surfare far frorn the vent and was not subsequen tly (Ful ton, l 975a, p. 38 ). During deglac1ation, dust was blown reworked (for example, in large bogs), it forms a uniform from un vegeta ted surfaces and deposited in protected areas layer a few mi llimetres to sever a l centimetres in thickness. as Joess. At t he sa me time, wherever t here was an abundant Where deposited on irregular surfaces and then reworked (for sour ce of sand, dunes were construc t ed by wind. As bare example, on fans), the tephra is discontinuous and may be surfaces bec:a me stabil ized by vegetation, there was a several tens of centiflletres thick in local lenses. T ephra marked r educti on in loess deposition and dune form a tion. On units of several postglacial volcanic eruptions have been some modern f loodplains, however, wind still sweeps dust recognized in British Columbia, and these are discussed from unvegetated f lats cmd blows sand into small active individually in the section "Postglacial Lava F lows and dunes. Tephras".

Sediment Types and Their Distribution Late Glac ial and Postglacial Sea Level s Post glacial sediments ar e w idel y distributed in Br itish Changes in land -sea positions in British Colurn b ia and Columbia. Fluvial sed iments underlie floodplains, terraces, adjacent regions during late Quaternar y time have resulted deltas, and son1e fans, and generally occur in association with from a combination of eustatic, glacio-isostatic, and present- day rivers and streams. Likewise, eolian deposits, diastrophic adjust ments (East erbrook, 1962, 1963; including Joess and dune sand, ar e 111ost ex t ensive in and Mathews et al., 1970; Miller, 1973; Clague, 19 7 5b; adjacent to major river valleys, but t hin loess veneers much Fladmark, 1975; Andrews and Retherford, 1978; of the Interior Plateau. Thorson, 1979, 1980). Recause these rhanges may occur Pos t glacial marine sediment s occur in 111ost offshore independently or se m i-independentl y of one another , it is areas of Br i tish Columbia but are thirkest adjac:ent t o the generally difficult t o assess the contribution of each to past deltasl of ar ge river s. v\arine sediments also were deposited sea level stC1nds. It is possible, however, to date for mer on coastal lowlands and at t he heads of some f iords during shorelines and sediments deposited dur ing transgressions and late g lacial and ear ly postglac ial t ime. regressions, and thus determ ine the net effert on sea level of eustatic, isostatic, and diastrophic adjustments through time. Organic deposits orc:ur in shallow rlosed depressions, at t he sha llow margins of lakes, and on gen tly sloping, poorly drained surfaces. Most deep basins occupied by organir Vancouver Island and the Mainland deposits previously ron t ained lakes; in these, peaty surface Early Postglacial Sea Levels sediments rommonl y overlie marl , which, in t urn, overlies lacustr1ne silt and clay. In contr ast, bogs in m eltwater Most areas near the periphery of the Cordilleran Ice channels, in abandoned f loo<1p lain channels, and on subaerial Sheet were covered by the sea dur ing and immediately deltas generally overlie f luvial sand and silt, whereas bogs on following deglacia tion (Fig. 5J; this was due to isostatic coastal lowlands bC'low the late g lacial and early postglacial depression of the crust by glacier ice. Along the mainland marine limi t commonly overlie marine slit and c lay. Organic coast, where the ice sheet approached its greatest thickness, deposits o f bogs situated on floodplains and a t t he toes of glacio-isostatic depression more than compensated for lower alluvial fans generally contain interbeds of mi neral detritus.

19 eustatic water levels, and here postglacial marine limits are Maximum marine limits were attained on the mainland highest. Southwest and west of these areas, marine limits coast and on much of Vancouver Island immediately following decrease in elevation due to the reduced importance of ice retreat. Because deglaciation was a diachronous event, glacio-isostasy relative to eustacy. Thus, whereas the marine however, the limits were not reached at the same time in limit is 200 m or higher at Vancouver (Armstrong, 1981) and these areas. For example, near Vancouver the marine limit in the Terrace-Kitimat area, and is at least 150 m near was attained before 12 900 ± 170 years ago (GSC-21 93, Bella Coola (Andrews and Retherford, 1978, p. 345-346), it Lowdon et al., 1977, p. 14), whereas in the Terrace-Kitimat decreases to about 90 to l 00 m near Alberni (Fy !es, 1963, area, where deglaciation occurred later, the marine limit was p. 91) and 75 m at Victoria (Mathews et al., 1970, p. 693), reached about 10 790 ± 180 years ago (GSC-523, and is less than 50 m on the west coast of Vancouver Lowd on et al., 1967, p. 174 ). Island (Valentine, 1971, p. 9; D.E. Howes, personal communication, 1979).

LEGEND

AREA OF MAXIMUM MARINE OVF.RLAP EXTENT OF MARINE OVERLAP - UNKNOWN 150 ELEVATION OF MARINE LIMIT IN METRES

BRITISH

COLUMBIA

0 50 100

KI LOME TR ES

Figure 5. Maximum late Quaternary marine overlap in British Columbia. Extent of overlap inland from the heads of most mainland fiords is unknown. 20 Emergence of the isostatically depressed coastal Middle Postglacial Sea Levels lowlands of Vancouver Island and mainland British Columbia During middle postglac1al time, many mainland and was rapid. Present sea level was attained perhaps as early as eastern Vancouver Island coastal sites were more emergent 11 700 ± 170 years B.P. at Victoria (l-3675, Buckley and than at present (Mathews et al., 1970, p. 696-697; Andrews Willis, 1970, p. 101-102), between 10 000 and ll 000 years and Retherford, l 978, p. 348). Terrestrial sediments dated ago on eastern Vancouver Island and in the Fraser Lowland 7300 ± 120, 7600 ± 100, 8290 ± 140, and 8360 ± 170 years (Mathews et al., 1970, p. 694), and between 8000 and old (S-99, McCall um and Wittenberg, 1962, p. 73-74; GSC-2, 9000 years ago near Bella Coola (Andrews and Dyck and Fyles, 1962, p. 15; GSC-229 and GSC-225, Retherford, 1978, p. 341). Dyck et al., 1965, p. 35) occur up to 11 m below mean sea Emergence may not have proceeded in a uniform level in the Fraser Lowland. Sea level was several metres fashion. Mathews et al. (1970, p. 695-696) proposed that, in lower than present at Comox on eastern Vancouver Island the Fraser Lowland and on eastern Vancouver Island, between 6820 ± 200 and 8680 ± 140 years B.P. 0-1227, emergence was interrupted by a strong, but short-lived Mathews et al., 1970, p. 696; GSC-265, Dyck et al., 1966, resubmergence about 11 500 to 12 000 years ago. The main p.113-114), but was at about its present position by evidence for this resubmergence is the presence in the 5680 ± 130 years B.P. (GSC-424, \Ila thews et al., 1970, Georgia Depression and Puget Lowland of radiocarbon-dated p. 696). At Victoria the sea was lower than at present from fossiliferous marine sediments overlying post-Vashon before 9250 ± 140 to after 5470 ± 115 years B.P. U-3676 "terrestrial" deposits (Mathews et al., 1970, p. 695). Many and l-367 3, Buckley and Will is, 1970, p. l 0 l ). deposits formerly thought to be terrestrial are now known to be marine or deltaic, thus weakening the argument for a Late Postglacial Sea Levels second post-Vashon marine transgression (e.g., Croll, 1980). During the past 5000 years, sea levels have not Nevertheless, an organic horizon containing what appear to fluctuated significantly on the inner coast but apparently be in situ stumps occurs between two late Pleistocene were up to a few metres below present level during much of 11;laciomarine units in northern Puget Lowland 80 km this interval. Hebda (1977) studied the paJeoecology of Burns southeast of Vancouver. Assuming the stumps indeed arc in Bog, which is situated near present sea level on the Frase r situ and both glaciomarine units are post-Vashon in age*, this River delta, and concluded that the sea was no higher than at stratigraphic sequence provides good evidence for two trans­ present during the past 5000 years. A tree stump exposed on gressions and an intervening regression at the close of the a beach north of Victoria and protruding through a peat bed Pleistocene. 1.5 m below high tide has been dated at 2040 ± 130 years A quite different early postglacial sea level history has (GSC-252, Mathews et al., 1970, p. 697). Another peat bed, been reconstructed for southeastern Vancouver Island 4350 ± 100 years old (GX-0781, Kellerhals and Murray, 1969, (Mathews et al., 1970). Here, there is no evidence for the p. 8J) occurs 1.8 m below high tide on the Fraser River delta. second marine transgression postulated for nearby Puget Finally, numerous coastal archeological sites occupied during Lowland. At Victoria, following deglaciation about middle and late postglacial time are now partially or 13 000 years ago, isostatic uplift caused a rapid relative fall completely submerged, indicating former lower sea levels in sea level from the marine limit at about 75 m. The sea (e.g., Mitchell 1971, p. 67). For example, a site on Galiano attained its present level about 11 700 ± 170 years ago Island now partially inundated at high tide, contains material (1-367 5, Buckley and Willis, 1970, p. l 0 l-102) and probably 730 ± 130 to 3160 ± 130 years old (GSC-436 and GSC-437, was no higher than at present during the remainder of Lowdon et al., 1969, p. 34-35). Jn the Bella Bella -- Bella postglacial time. An interval of relative sea level stability Coola area, middens located below high tide and presently from about 11700 ± 170 to 9250 ± 140yearsB.P. 0-3675 being eroded by waves range in age from 50 ± 80 to and I-3676, Buckley and Willis, 1970, p. 101-102) may reflect 3400 ± 100 years old (GaK-3717 and GaK-2715, Andrews and a balance between the eustatically rising sea and the Retherford, 1978, p. 347). Finally, in the vicinity of Prince isostatically rebounding land. What is possibly a coeval Rupert several archeological sites presently are waterlogged slowing or halt in emergence also has been proposed for the and partly eroded by the sea. These sites were occupied by Juneau area of southeastern Alaska (Miller, 1973, p. Cl 7). man nearly continuously for the past 5000 years, indicating that sea levels were similar to or lower than that at present There presently is no satisfactory explanation for the at Prince Rupert throughout this period. second post-Vashon transgression proposed for parts of the Georgia Depression and Puget Lowland. It is unlikely that Whereas late postglacial sea levels were lower than this transgression was caused by localized tectonic move­ that at present along most or all of the inner coast, they ments because of the regularity in the slope of the marine were higher along many parts of the west coast of Vancouver limit throughout the region and the absence of subsequent Island. for example, on the north side of Nootka Sound comparable tectonism. Isostatic depression due to a build-up littoral sediments deposited when the sea was at least 4 m of ice during the Sumas Stade likewise seems unlikely in view above present high tide have yielded radiocarbon dates of the small volumetric changes in ice loads during Sumas ranging from 3590 ± 190 to 4230 ± 90 years (GSC-1767 and time and the apparent nonsynchroneity of the Sumas advance GaK-2183, Lowdon et al., 1974, p. 7; Dewhirst, 1978, p. 8-9). and the second post-Vashon transgression. Finally, the A series of younger radiocarbon dates from a sire about magnitude of the transgression (JOO to 150 m in the Fraser 20 km to the southeast are associated with former sea levels Lowland according to Mathews et al., 1970, p. 700) cannot be up to a few metres higher than present (Hebda and accounted for solely by a rapid eustatic rise in sea level. The Rouse, 1979; D.E. Howes, personal communication, 1980). apparent inexplicability of the postulated crustal movements casts some doubt on their validity. This problem cannot be Contemporary Sea Level Fluctuations resolved without additional field studies, but it is probable Tide-gauge records and geodetic measurements indicate that the second post-Vashon marine transgression, if indeed that the sea is rising relative to the land on the mainland real, is much smaller than previously thought. Limited coast (Mathews et al., l970, p. 697-699; de Jong and resubmergence perhaps was caused by a rapid eustatic sea Siebenhuener, l 972; Riddihough, 1979, p. 358-359). De Jong level rise acting in concert with as yet poorly understood, and Siebenhuener (1972, p. 4) concluded from tide-gauge complex isostatic adjustments in the crust and mantle. records for the period 1943 to 1968 at Vancouver, Point Atkinson, and Prince Rupert that this rise is 2 to 3 mm/a. Part of this may be due to a worldwide eustatic rise in sea level, but most is caused by crustal subsidence.

* A sample from one of the stumps at this site recently has been radiocarbon-dated at II 455 ± 125 years (Beta-1324; D.P. Dethier, personal communication, 1980). 21 Comparison of computed elevations of bench marks in Late Postglacial Sea Levels the Fraser Lowland, which were surveyed between 1914 and Sea levels continued to fall on the Queen C harlotte 1924 and resurveyed between 1958 and 1967, indicates Islands during late postglacial time. On northeastern Gr aham downward movement of almost all stations, with an increase Island, for example, the sea was per haps 9 m higher t han at in the rate of displacement southward across the present 5460 :t 70 years ago (GSC-2963), bu t had fallen to International Boundary (Mathews et al., 1970, p. 699). below 6 m be tween 3280 ± 210 and 4150 ± 90 years ago Maximum subsidence rates are about 1.5 mm/a. Apparently, (GaK-5439, Se vers, 1975, p. 15; S-936, Rutherford et al., this sinking is not related to loading of the crust by deltaic 1979, p. 75), and to about 2 m by 940 ± 60 years ago sediments of Fri!ser River because maximum subsidence is (GSC-2815, Harper, 1980, p. 15). These dates support not centred over the Fraser River delta; rather, the sinking is Fladmark's (1975, p. 158) contention that the highest (> JO m) likely due to tectonic movements (Riddihough, 1979). of the shoreline complexes recognized by Whatever its cause, historical subsidence in this area appears Sutherland Brown ( 1968, p. 35-36) dates from 4000 to to be substantially greater than the Jong-term average 9 500 years ago, whereas the middle complex (3 to 8 m ) is inferred from submergence of terrestrial features 4000 to about 2000 to 3000 years old. The lowest shoreline fea ture 8000 years old. recognized by Su therland Brown is a wave-cut bench at present high t ide which has not been directly dated. Queen Charlotte Islands Early Postglacial Sea Levels Summary On the Queen Charlotte Islands, far from the centre of Sea levels on the mainland and Vancouver Island coasts the Cordilleran Jee Sheet, postglacial marine submergence were high during and shortly after deglaciation. G lacio­ occurred to at least 15 to 18 m elevation (Sutherland isostatic upl if t resulted in rapid emergence, with the sea Brown, 1968, p. 34-35; A lley and Thomson, 1978, p. 18-19).* reaching i ts present level r elative to the land 1000 to The postglacial transgression on these islands not only was 4000 years after deg lac ia ti on, depend ing on the locali ty. The much less ex tensive than the transgression in coastal areas of sea continued to fall relative to the land and was up to 12 m eastern Vancouver Island and mainland British Columbia, bu t or more below present when emergenc e culminated about it also occurred later (Clague, !975b, p. 18). In fact, 6000 to 9000 years ago. During most of the remainder of Sutherland Brown (1968, p. 34-35), N asmith (1970, p. 7), and postglacial t ime, sea levels have been lower than at present. Fladmark (197 5, p. 154- 157) all argued that sea levels on the A late postglacia1 marine transgr ession has resul ted in Queen Charlotte Islands during late glacial and early erosion of many coastal middens and inundation of low-lying postglacial time were lower than at present, the main terrestrial vegetation. evidence being what they interpreted to be drowned, outwash-filled channels graded to below present sea level and In contrast to the above pattern of sea level variations, submerged wave-cut scarps. Support for relatively low sea which is characteristic of inner coas tal areas, sea levels on levels on the Queen Charlotte Islands during late glacial t ime the Queen Charlotte Islands were relatively low during early is provided by a terrestrial peat dating 12 400 ± JOO years postglacial t ime and were higher than at present during old (GSC-3112) at its base and extending to below mean sea middle and late postglacial time. level on northeastern Graham Island. On the basis of this The differences between the sea level histor ies of the date, it seems probable that sea levels in the vicinity of the inner and outer coasts during middle and late postglacial time Queen Charlotte Islands were lower than t hat at present at a probably ar e due to diastrophism. Coastal areas of British time when maximum marine limits, localJy 200 m or m ore, Columbia are si tuated near the junction of major crustal were achieved on the mainland coast to the east. If this is plates. Al though the tectonics in this regi on are complex correct, the gradient of vertical displacements caused by (see Riddihough, 1979, for a recent review and sum mary), glacio-isostatic depression of the c rust must have been very present plate inter ac tions involve both strike- slip steep between the Coast Mountains and the Queen Charlotte displacement along major transform faults and compression Islands during and shortly after the Fraser Glaciation. and crustal thickening in the vicinity of subduction zones. As I mplicit in this is the possibility that ice cover on the Queen a result, seismicity is high in most coastal areas and Charlotte Islands during the F raser Glaciation was not differential tec tonic movements are to be expec ted. extensive. Although the pa ttern of sea level fluctuations in British Columbia cannot be related in de tail to t he tectonic Middle Postglac ial Sea Levels framework of the region, it does appear t hat most of t he The transgression from the low sea stand of late glac ial outer coast is being uplifted, while the inner coast is time on the Queen Charlotte Islands began before 9000 years subsiding. ago, which is the approximate age of shells of marine molluscs living when sea level was at least several metres Paleoclimate higher than that at present (e.g., 9040 ± 80 years, GSC-2867; 8850 ± 90 years, GSC- 2534, Alley and Thomson, 1978, p. 18). The char acter of fossil pollen spectra, t he posi tion and This conclusion is supported by a radiocarbon date of age of post-P leistocene moraines, and inferred posi t ions of 9510 ± 280 years 0 - 1621, Swanston, 1969, p. 31) on molluscan former treelines all provide ev idence of postglacial climatic shells in beach deposits at about JO m elevation on Prince of fluc tuations in Br itish Columbia. Wales Island, southeastern A laska. Dated archeological and geological materials associated Early and Middle Postglacial Climates with raised beaches on the Queen Charlotte Islands indicate Southern British Columbia that the sea had fallen from the marine limit by 5460 :t 70 years ago (GSC-2963), but likely remained fairly The earl iest major work on postglacial c lima tes in high until about 4500 years ago (e.g., 4290 :t 130 years, southern British Columbia and adjacent areas in the United GSC-1554, Lowdon et al., 1972, p. 21 ; 4445 ± 90 years, States is t hat of Hansen (1937, 1938, 1939a, b, c 1940a, b, I- 9169, Alley and Thomson, 1978, p. 19). 19 4Ja, b, 1943, 1944, 19 47a, b, 1948, 1950, 1955, 1967). Hansen postulated the existence of a postglac ial interval of maximum warmth and dryness (i.e., the "Al tithermal" of Antevs, 1948, p. 176), which was preceded and followed by

* N.F. Alley (personal communication, 1979) has identified a possible strand.li ne at about 30 m elevation on northwestern Graham Island; however, the age of this feature is unknown, and it has not been proven to be of marine origin. cooler wetter periods. The strongest evidence for a Additional evidence for a postglacial xerothermic postglacial xerothermic interval comes from the dry interval is provided by dead wood occurring above present Columbia Plateau in eastern Washington where Hansen found treeline in the mountains of southern British Columbia that pollen of xerophytes consistently reaches maximum (e.g., Lowdon and Blake, 1968, p. 226). The wood has been values around the 6600 year old Mazama tephra layer in found on the surface and beneath snow, ice, and glacial several bogs. deposits, indicating a past climate warmer than the present (Ma thews, 1951, p. 366). Radiocarbon dates on this wood Hansen (1955) placed the xerothermic interval in south­ from three widely separated sites include 5260 ± 200, central British Columbia between 3500 and 7 500 years ago, 5300 ± 70, 5470 ± 140, 5950 ± 140, 6170 ± 150, and with a "thermal maximum" around 6600 years ago. The 7640 ± 80 years (Y-140bis, Stuiver et al., 1960, p. 58; climatic interpretation there, however, relied heavily on an GSC-2027, Low don and Blake, 197 5, p. 20; GSC-197, inferred abundance of Pinus ponderosa, an important floristic Dyck et al., 1966, p. 109; GSC-760, Lowdon and Blake, 1968, element of the semi-arid zone in western North America. p. 226; GSC-1477, Lowdon and Blake, 1973, p. 26; GSC-1993, Mack ( 1971) has shown that the size-range method which Lowdon and Blake, 1975, p. 20). In addition, a date of Hansen used to distinguish Pinus ponderosa from Pinus 9120 ± 540 years (GSC-1390, Lowdon et al., 1971, p. 295-296) contorta is unreliable. Because the latter species is tolerant was obtained on charcoal above present treeline in the of a wide range of climatic conditions and occurs in a variety Cascade Mountains in southern British Columbia (see also of environments, Hansen's paleoclimatic reconstruction for van Ryswyk, 1969, 1971; van Ryswyk and Okazaki, 1979). south-central British Columbia might be disputed. Recent These dates suggest that there was an interval during palynological and geomorphic work in the Okanagan Valley of postglacial time when the climate was warmer than it is southern British Columbia, however, has confirmed the today and that in parts of southern British Columbia this existence of a warm dry interval from about 8400 years ago interval terminated after 5200 years B.P. to about 6600 years ago, after which there was a shift to cooler, more moist conditions (Alley, l 976c). Likewise, recent palynological investigations in eastern Washington and Atlin Region northern Idaho indicate dry and warm conditions during much Paleoclimatic information for early and middle of middle postglacial time, al though the proposed time postglacial time in northern British Columbia is presently boundaries of this xerothermic interval differ at the various available only for the Atlin region. Dated palynological studied sites (Mack et al., 1976, l 978a, b, c, 1979). profiles of kettle-hole bogs in this area have been described In the Fraser Canyon area in southwestern British by Anderson (1970) and Miller and Anderson (1974a, b). They Columbia, cool moist conditions which prevailed during postulated a postglacial thermal maximum between about deg lac iation were followed about 10 400 years ago by a dry 2500 and 8000 years ago. During this interval, mean July warm climate (Mathewes, l 973a, b; Mathewes and temperatures are thought to have been up to l °C higher Rouse, 1975). Dry warm conditions persisted in that area than at present, and precipitation was at today's level until about 6600 years ago, when there was a return to a or somewhat higher (e.g., Miller and Anderson, l 974a, p. 46, cooler wetter climate. The timing of the xerothermic 48-50). Glaciers in the nearby Boundary Ranges of the Coast interval there is similar to that in the Puget Lowland (Hansen Mountains were in retreat, except near the end of the and Easterbrook, 1974, p. 600-60 l ). interval. Palynological work in the Georgia Depression has not The thermal maximum in the A tlin region was preceded yet provided evidence of a xerothermic interval during by a cooler drier period during which Atlin Valley and other postglacial time. Mathewes (197 3a, b) studied postglacial valleys draining the Boundary Ranges were becoming lake sediments in the Fraser Low land near Haney and deglaciated. Deglaciation proceeded in an irregular fashion, concluded that a humid coastal climate has prevailed in that with stillstands and readvances occurring during cooler parts area since about 10 500 years ago. Likewise, Hansen (1950) of this period. Mean July temperatures were more than 2°C found no evidence of a pronounced warm dry interval on the below present ca. 10 500 to 11 000 years ago, about 2°C lowlands of southeastern Vancouver Island. Rather, he below present ca. 10 000 to 10 500 years ago, about 3°C attributed changes in pollen assemblages there to normal below present ca. 9000 to 10 000 years ago, and 0 to 2°C forest succession in response to a general amelioration of below present ca. 8000 to 9000 years ago (Miller and climate and soil maturation. Anderson, l 974a, p. 46, 50-52). Shrub tundra grew in areas now covered by spruce forest during the coldest parts of this The lack of evidence for a postglacial xerothermic period (i.e., 9000 to 10 000 and 10 500 to 11 000 years ago). interval in southwestern British Columbia may reflect a lower degree of climatic change in coastal areas as compared Miller and Anderson (l 974a, b) also proposed that the to the interior. Furthermore, any effects of a warming and climatic fluctuations in the A tlin region were out-of-phase drying climatic trend likely would be masked in coastal areas with those on the opposite side of the Coast Mountains in where precipitation is not a limiting factor on plant growth. southeastern Alaska (Heusser, 1952a, b, 1954, 1960, 1965, In contrast, in semiarid areas of the southern Interior Plateau 1967; Heusser et al., 1954). In general, when cool moist where precipitation is limiting, a minor reduction in conditions prevailed in the Alaskan coastal zone, cool and precipitation or an increase in temperature would lead to slightly drier climatic conditions characterized the marked vegetation changes. northwestern British Columbia interior. Warm, relatively dry coastal climates were contemporaneous with warm wet In the wet temperate Puget Lowland and on Olympic interior climates. Peninsula the xerothermic interval also was less strongly expressed than in dry interior regions (Hansen, l 947b). Both Atlin area paleoclimates differed not only from those Hansen(l947a) and Heusser(l960, 1964, 1973b, 1974, 1977, of southeastern Alaska, but also from those of southern 1978), however, still postulated the existence in these areas British Columbia. For example, during the warmest part of of a period of increased warmth, preceded and followed by postglacial time at A tlin, precipitation equalled or exceeded cooler and wetter conditions. Hansen and Easterbrook ( 1974, present values, whereas at the same time in south-central p. 599-600) described pollen assemblages in a bog in the British Columbia, precipi ta ti on was lower than at present. Puget Lowland and concluded from them that a climate Such differences perhaps are to be expected, in that somewhat warmer and drier than the present characterized temperature and precipi ta ti on responses to global climatic that area from before 9920 ± 760 years B.P., 0-2280, changes probably have differed from one region to another. Easterbrook, 1969, p. 2285) to about 7000 years ago.

23 This may be particularly true for northwestern North advance. Alley (I 976b) postulated a glac ial advance (Dunn America where there are complex interactions of continental Peak advance) between 4000 to 5000 years ago in t he and maritime air masses, and strong topographic: controls on mountains of so uth-cent ral Bri tish Columbia. Subsequent climate. For example, Miller and Anderson (l974b, work at Dunn Peak by Duford ( 1976) and [)ufor d and p. 218-220) attributed t he opposing c limatic characteristic:s Osborn ( 1978), however, has shown that this ad vance is of Atlin and coastal southeastern A laska to shifts of the substantially older than originally thought, being ei ther lat e Arctic Front and related storm tracks across the Boundary Pleistocene or early Holocene in age. The evidence for t his Ranges and to concomitant vertical changes in freezing is the occurrence o f both 6600 year old Mazama ash and level s during Quat ernary time. charcoal dated 7360 ± 250 years old (G X-4039, Duford and Osborn, 1978, p. 87) on the morai ne deposited during the Dunn Peak advance. Early Holocene Glacial Advances in the Cordillera A well documented period of glacier expansion occurred A lthough early postglacial climates in many parts of throughout the Cordillera of western ~ ort h America 2300 British Columbia at times were as warm as or warmer t han to 3 I 00 radiocarbon years ago (e.g., Goldthwait, I 963; the present, there probably were short-lived cold intervals Crandell and M i lier, I 964; Porter, 1964; Crandell, I 965a; during which alpine glaciers advanced. Duford (1976) and Haselton, 1965, 1967; Borns and Goldthwait, 1966; Denton Duford and O sborn ( 1978) documented a c irque glaciation and Stuiver, 1966; Porter and Denton, 1967; Curry, 1968, older than 7400 years i n the Shuswap Highl and, south-central 1969; Rampton, 1970; Denton and Karlen, 1973 , 1977). Bri t ish Columbia. Luckman and Osborn (1979) presented Tiedemann Glacier in the southern Coast Mountains reached evidence for an early Holocene or late Pleistocene advance in its maximum pos tglacial position 2940 ± I 10 years ago the central Canadian Rocky Mountains. Both advances were and began to re treat 2250 ± 130 years ago (GSC- 938 and of limited extent (less than 2 km beyond present ice margins) GSC-948, Lowd on et al., l 97 I , p. 300; Fulton, I 97 l , p. 24 ). and, in general, were sm aller than those of the last several Alley (1 976b) recognized a glac ial advance (Battle Mountain centuries. Early postglac i al or la te Pleistocene glacial advance) within the time interval 24 00 to 3300 years ago in events also have been proposed for the l ~ ni t ed States Rocky the mountains of south-central Bri t ish Columbia. Mountains (e.g., Renedic t, I 968a, b, l 97 3; Graf, 197 I); t he Brooks Range, Alaska (e.g., Porter, 1964, 1966); and the Supporting evidence for cooling and glacier expansion Wallowa Mountains, Oregon (Kiver, 1974). during this inter val is provided by the pos tglacial pollen record of Kelowna Bog in the semiarid Okanagan Valley. E xtensive early Holocene glac ial advances in the Pollen assemblages from this bog indicate alt ernating moist Canadian Rorky Mountains have been postulated by several and dry conditions on the valley floor. Alley (1 976c) workers (e.g., Stalk er, 1969; Reeves and Dormaar, 1972; attributed these changes in moisture regime to variations in Fox, 1974; Reeves, 197 5; Rutter, 1976, 1977; H<:lrr is and runoff from ad jacen t uplands, which in t urn were caused by Howell, 1977); however, these g lacial events are not fluc:tuations in temperature and precipitation. Intervals of adequately dated and likely are of la te Pleistocene, rather increased moisture were thought to be contemporaneous with than Holocene age (for a detailed discussion, see L uckman periods when glaciers in alpine areas were in advanced and Osborn, 1979, p. 7 J-73). For example, Rutter (1977, positions. A lley (1976c, p. 114 1) thus suggested that a moist p. 19-21) proposed that the Deserters Canyon advance, during phase between about 2000 and 3200 years ago in Okanagan which glac iers expanded from the Omineca and Cassiar Valley correlates with an interval of glacier expansion mountains into the northern Rocky Mountain Trench, recognized el sewhere in the Cordillera. occurred between 7470 ± 140 and 9280 ± 200 years ago (GSC-1069, Lowdon etal., 1971, p. 298; GSC-1497, A short- lived advance occurred locally in western North Rutter, 1976, p. 431 ). Cnfortunatel y, neither lim iting date is America 1050 to 1250 years ago (Rampton, 1970; Denton and directl y assoria ted with Deserters Canyon deposits; thus a Karlen, 1973). A lthough t his event has not been documented H olocene age for the advance has not been proved (Luckman in British Columbia, Alley (I 976c, p. I I 4 I) proposed that t he and Osborn, I 979, p. 73). present moist phase at Kelowna Bog began about I 500 years ago. Late Postglacial Climates In many parts of British C olumbia alpine glaciers r eached their postglacial maxirna during t he last several Southern British Columbia centuries (e.g., M unday, 1936; Ma thews, 195 I), destroying or A lthough the timing of the xerothermic inter val in burying evidence of earlier , less extensive advances. This southern Bri tish Columbia is uncert ain, i t is c lear that the interval of glacier expansi on has been referred to as the climate of late postglacial time, in general, was colder and "Litt le Ice Age" and is recognized in mountain r anges wetter than that of middle and much of early postglacial throughout t he world (for summary and references, see time. Post-A ltithermal cooling caused alpine glaciers to Por ter and Denton, 1967; Denton and Karlen, 1973). Within advance from retract ed positions. Su ch advances occurred in this and earlier postglacial cold intervals, there undoubtedly the Cordillera of western '.'·forth America about 4000 to 5000, were minor glacier fluc tuations. For example, Little Ice Age 2300 to 3100, and 1050 to 1250 radiocarbon years ago, and advances in the European A lps culminated about A .D. 1500 to w ithin the last sever al centuries (Denton and Karlen, 1973). 1640, 1710, 17 80, 1850 , 1890, and 19 16 (Denton and Kar len, 1973 , p. 155 ). The ol dest interval of post-A I ti thermal glacier expansion i s not well documented and probabl y involved relatively minor growth o f glac iers. South Cascade Glacier Atlin Region in Washington, however, is known to have ad vanced 4700 to Al though air temper a tu res in British Columbia, in 4900 radiorarbon years ago (Miller, 1967, I 969; Denton and general, were lower in late postglacial time than during Karlen, 1973, p. 162). Glacier growt h after 5200 years B.P. middle postglacial time, precipi tation responded to global in British Columbia is indicated by a tree stump dated tempera tu re changes in a complex fashion. Thus, whereas 5260 ± 200 year s (Y - I 40bis, Stuiver et al., 1960, p. 58) and cooling in sou thern British Columbia and in coastal rooted on a nunatak well above present treeline on .\fount southeastern A laska apparently was accompanied by Garibaldi in the southern Coast Mountains. The tree was part inc reased precipita tion, cool intervals in the Atlin region of a forest destroyed during a glac ier advance. The date on were mar ked by reduced precipita tion (Anderson, I 970; M iller the stump, however, is only a maximum limi ting da te for this and A nderson, I 974a, b). A t A t lin there was a cool dry period

24 from about 750 to 2500 year s ago, during whir h glaciers w ith continued research, additiona l glacial events will be expanded in the nearby Boundary Ranges (Mi lier and recognized and the Holocene glacial chr onology of the Anderson, 1974a, p. 48 ). Within t he last 750 years, province will be refi ned . This will lead to a better precipitation and temperatures in t he A tlin region have understanding of the nature and m agni tude of t he c limatic increased to values comparable to those prevailing prior to changes responsible for observed glacier fluctuations. It 2500 years ago. shou ld be remembered, however, that alpine gl aciers may respond differently to world- wide changes in climate because of the variable e ffec ts of topography, geographic location, Summary and glac ier regimen. Thus, glacier expansion or r ecessi on in During postglacial time there were al ternating intervals one area may be out-of-phase wi th that in another area. It is of glacier expansion and contraction superi mposed on broader for this reason that the concept of world- wide synchronei ty climatic trends. The climate of Flritish Columbia was cool of glacial events, which has been proposed by se veral and wet during and immediately following deglaciation at the scientists (e.g., Porter and Dent on, 1967, p. 200; Curry, 1969, close of the Pleistocene Epoch. At this time there probably p. 41; K ind, 1972, p. 59-61), is probably an oversimpli f ication. were localized resurgences of remnant Pleistocene glaci ers. Tha t this is i ndeed the case is suggested by t he f act tha t the These resurgences, however, were not everywher e Holocene glac ial chronology for the southern Rocky contemporaneous and probably were caused as much by local Mountains is strikingly dissimilar to t hat for mountain fac tors as by global cooling. system s f arther west, excep t for t he period fo the last f ew hundred year s (Benedict, 1973, p. 596-597). In southern British Columbia arboreal vegetation became established shortly after deg laciation (e.g., Hansen, l 955; Mathewes and Rouse, 197 5), indicating a Postglacial Lava Flows and Tephras rapid transition to a nonglac ia l cl imate without an 1\tl ost postg lacial volcanic activity i n Brit ish Columbia intervening stage of t undra veget ation . T his is supported by has been concentrated in three linear volcanic bel t s (F ig. 6) the occurrence of a skull of Bison cf. occidentalis in a that appear to be related t o crustal p lat e boundaries glacial-lake delta in south-central British Columbia (Souther, 1976, p. 260-26 l ). From sou th to nor th, t hese are (Fu! ton, l 97 l, p. 19). H owever, shrub tundra did becom e the Garibaldi volcanic belt, t he Anahim volcanic bel t, and the established in presently forested valleys in the Atlin area Stikine volcanic belt. during deglaciation (e.g., Anderson, 1970, p. 286-292; Miller and Anderson, l 974a, p. 50-52). The Garibaldi volcanic be l t includes approximately 32 Quat ernary eruptive centres of whi ch three, Within a few thousand years after deglaciation, t he Mount Garibaldi, Mount Cayley, and Meager Mount ains, are cli mate in most areas was as warm as, or warmer than t he major daci t ic domes. Mount Garibaldi was last active about present. Generally warm and locally dry conditions persisted 10 000 years ago. The youngest activity in the belt occurred until about 6600 years ago in south-central British Columbia, about 2000 years ago from a vent near Meager Mount ai n. after whirh the climate gradually became cooler and wetter. In the southern Coast Mountains and perhaps in other The Anahim volcanic belt includes about 37 Qua ternary mountain ranges, treeline and, therefore, temperatures were volcanic centres, all of which have produced alkali olivine higher than at present until after 5200 years ago. In basalt m agmas. Many of t he sm all pyroclastic cones and thin northwest ern British Columbia, air temperatures remained blocky int ra-valley flows associated w i th t hese centres are slightly higher than at present until about 2500 years ago, and postglacial in age. there was no reduction in precipitation during the postglacial The Stikine volcanic bel t inc ludes more than interval of maximum warmth as there apparently was in 50 postglarial eruptive centres plus at least as many of late south- centra l British Columbia. Miorene to late Pleistoc ene age. The lar gest volcanic centre These observations suggest that postglac ial c limatir in the Stikine belt i s the Edziza Peak - Spectr um R ange changes did not occur everywhere in Bri t ish Columbia at t he complex whirh was last active about 1350 year s ago same time. Some caution is required here, however, because (Souther, 1976, p. 261) and has had a long, nearly continuous most late Quaternary paleoclimatic inferences, including record of activity spanning most of post-Miocene t ime. Most many of those mentioned above, are based on the assumption eruptive centres in the bel t, however, have been t he locus of that f loras are sensitive to temperature and precipitati on a single pulse of activity dur ing which one or mor e small changes. Floras in some areas of British Columbia probably pyroclastic cones were built and a small volume o f alkali were relativel y insensitive to the relatively small c lim at ic olivine basal t extruded to form thin b locky f lows. The changes of postglac ial time. For example, fossi l pollen youngest eruption of this type i ssued f rom f i ssu r es in the assemblages from several bogs and lakes in the lowlands of Coast Mountains near t he south end of t he Stikine belt less southwestern British Columbia provide no indication of t he than 150 years ago (E.\'LT. Grove, personal communication, 3 c limatic changes which produced treeline shif ts and glacier 1978).A The i yansh flow (0.45 k m ), in the same region, has fluctuations in nearby mountains. Microfossil assemblages been dated at 250 ± 130 year s (GSC-1124, Lowdon e t al., from the coastal lowlands thus may be of limited value in 1971, p. 300- 30 l; Suther land Brown, 1969). It issued f rom a r econstructing postglacial c limates. Variations in pollen cinder cone which was bu ilt inside an older cone about spectra through time in such ar eas may be due more t o local 625 ± 70 year s old (S-1046 , Wuorinen, 1978, p. 1037). soil f actors, rather than t o c limatic f actors Several volcanoes i n western N ort h America have (e.g., Hebda, 1977). erupted explosively in postglacial time to produce w idespread The xerothermic interval in British Columbia was tephra deposits in British Columbia (Fig. 6). Two of these followed by a generally cooler moister period punctuated by volcanoes are loca ted in Br itish Columbia, one in the Meager sharp c limatic fluctuations. T wo well documented intervals Mountain ar ea and the other in the Edziza Peak - Spectrum of post-Altithermal glacier expansion occurred in Brit ish Range complex. Volcanoes in the Cascade Mountains of Columbia, one between 2300 and 3100 radiocarbon years ago Washingt on and Oregon are the source of many tephra units and the other within t he last several centur ies. Jn most areas in the province, inc luding some of the most useful from a glaciers wer e more extensive during t he latter interval. Jn stratigr aphic point of view. For example, tephras derived additi on, there is some evidence for a third gl ac ial even t from .\t\oun t St. Helens in Washington and Mount Mazama between 4000 and 5000 radiocarbon years ago, al though it has (Crater Lake) in Oregon are widespread in southern Briti sh not yet been adequately docu111 ented. It is probable that, Columbia and serve as excellent marker beds. In addition,

25 ('

0 ('· «'.... LEGEND 1- • o QUATERNARY VOLCANO ST. HELE NS T TEPHRA \~:.\ °s~~~ERNARY VOLCAN IC _,_,_BR I DGE RIVER TEPHRA (OLDER LAYER ) GLACIER PEAK G TEPHRA _, _ ,_ ED ZIZA TEPHRA ...... EDGEC UMBE (?) HPHRA ~ W HI TE RIVER TEP HRA 0 100 100 300 -'00 ... .l-··· -- MAZAMA TE PH RA + ST. HELENS P (?) AND Lm;;i _____.. I '· - -- ST. HELENS Yn TEPHRA BR I OGE RIVER ( YOUNGER 1Ul0ME11H S LAYER ) TEPHRAS _ , _ ST. HELENS Wn TEPHRA X ST. HELENS W (?) TE PH RA

Figure 6. Late glacial and postglacial tephras in and near British Columbia. A. Distribution of Quaternary volcanic centres in western Canada and eastern Alaska and minimum inf erred extent of tephras derived from these centres. B. Inferred d ist r ibution of tephras in and adjacent to southern British Columbia which were erupted from Cascade volcanoes in Washington and Oregon. T ephra distributions from Bostock (1952), Nasmith et al. (1967). Westgate et al. (1970), Fu lton (1971), Okazaki et al. (1972), Sneddon (1974), Mullineaux et al. (1975), Souther (1976), Smith et al. (1977a), Westgate (1977), Porter (1978), and Mathewes and Westgate (1980).

G lac ier Peak in Washington erupted repeatedly in la te g lacial the source (Porter, 1978). Of these, t wo (layers Band G) are and early postglacial time, and tephra of one of t hese widespread outside of Washington, but only layer G has been eruptions has been found in western Canada, al though not yet identified in Canada. in British Columbia. Finally, volcanoes in eastern Alaska Layer G occurs in a band east of the source in eastern have erupted in late Quaternary t ime to produce air-fall Washington, northern Idaho, Montana, and southern Canada tephras which may be present in northernmost British (Fig. 6). It has been found at one si te in southeastern Alberta Columbia . Among these are Mount Edgecumbe in coastal (W estgate, 1968, p. 75; Westgate e t a l., 1970, p. 16), a nd southeastern A laska and a vent in the St. Elias Mountains known occurrences li e as near as about 32 km south of the near the Alaska- Yukon boundary from which the White River British Colu mbia - Washington boundary (Powers and tephra was derived. Wilcox, 1964, p. 1335). Molluscan shells associated wi th Tephras suc h as those cited above are differentiated layer G at Diversion Lake in Montana have a radiocarbon age largely on the basis of their mineralogical and chemical of 12 750 ± 350 years (W- 1644, Ives et al., 1967, p. 5 17 ). At attributes, which are determined by detailed laboratory this time, glaciers still covered much of southern British studies. Fie ld characteristics, such as colour, degree of Columbia (Prest, 1969; Porter, 1978, p. 38 -39), t hus weathering, grain size, thickness, and stratigraphic position, precluding preservation of the tephra in most areas. are a lso he lpful, but generally do not permit the positive However, layer G may yet be found in favourable geologic identification of tephra units far from their source vents. situations in the southeastern corner of the province, where some areas perhaps were ice free prior to the eruption (see Glacier Peak Tephra section enti t ied "Chronology of Deglaciation" in "F raser Glaciation Recessional Phase, Interior System"). Glacier Peak erupted repeatedly bet ween about l l 250 and 12 7 50 years ago, spreading pumiceous tephra east and Edgecumbe(? ) Te phra southeast from the vent (Fryxell, 1965; Wi lcox, 1965; Westgate et a l., 1970; Lemke et a l., 1975; Smith et al., Tephra, possibly derived from the Mount Edgecumbe I 977b; Porte r, 1978; Westgate and Evans, 1978). As many as area in the Boundary Ranges, occurs in southeastern Alaska nine tephra units have been identified within about 25 km of (Fig. 6) and has been provisionally dated at between 9000 and

26 11 000 years (Heusser, 1960, p. 184; McKenzie, 1970). This of 3350 ± 250 and 3510 ± 230 years (W-2549 and W-1752, tephra has not yet been reported in British Columbia, Mullineaux et al., 1975, p. 332). Limiting dates from British although its known distribution in Alaska indicates that it is Columbia, including one above the ash layer of likely present in the northwestern corner of the province. 3460 ± 140 years (GSC-1461, Lowdon and Blake, 1976, p. 9) and five below the ash ranging from 3220 ± 70 to 3640 ± 70 years (GSC-1946, Westgate, 1977, p. 2598; Mazama T ephra GSC-1868, Lowdon and Blake, 1978, p. 7), are in agreement Mazama tephra, the most widespread of the postglacial with dates cited above and suggest that layer Yn is 3300 to pyroclastic deposits, is found in Canada from Victoria to 3500 radiocarbon years old. Saskatchewan (Fig. 6; Westgate et al., 1970). The source of the tephra is a volcano at the present site of Crater Lake in Set P southwestern Oregon. Tephra of set P has been identified tentatively at one A date of 6640 ± 250 years (W-858, Rubin and locality in Canada, the Otter Creek Bog in southern British Alexander, 1960, p. 161) on charcoal buried in pumice at Columbia (Westgate, 1977). There, a thin tephra that has Crater Lake has been accepted as the age of Mazama tephra. chemical and mineralogical affinities with set P tephra is Charcoal collected from the tephra in Columbia River valley bracketed by radiocarbon dates of 2070 ± 80 and yielded a date of 6560 ± 115 years 0-3809, Fulton, 1971, 3220 ± 70 years (GSC-1939 and GSC-1946, Westgate, 1977, p. 21 ), which is in good agreement with the date from the p. 2594-2595). Set P tephra in Washington ranges in age from source area. 2580 ± 250 to 2930 ± 250 years B.P. (W-2539 and W-2829, Al though only a single Mazama tephra unit has been Mullineaux et al., 197 5, p. 331 ). found in British Columbia, multiple layers of Mazama ash have been reported in other areas (e.g., Borchardt et al., Set W 1971, 1973; Davis, 1977; Mack et al., 1979). For example, two layers of Mazama ash occur in a bog in northeastern Set W consists of at least six layers, the coarsest and Washington only 5 km south of the International Boundary thickest of which (layer Wn) extends northeast from the (Mack et al., 1979, p. 22 l ). The uppermost ash in this bog is volcano in a narrow band towards British Columbia (Fig. 6; bracketed by radiocarbon dates of 6810 ± 190 and Smith et al., 1977a). Smith et al. (1977a, p. 209) documented 6870 ± l l 0 years (TX-2882 and TX-288 l ), and the lower the presence of layer Wn at two localities in southern British is associated with a date of 6930 ± 110 years (TX-2883, Columbia within 30 km of the International Boundary. Mack et al., 1979, p. 217-218). The eruptions which produced Fulton (1971, p. 19) noted a thin, widely dispersed ash farther these two tephra units probably occurred within a few north in south-central British Columbia and correlated it with hundred years of each other. St. Helens W tephra. Charcoal from the basal bed of set W near Mount St. Helens Tephra St. Helens has been dated at 1150 ± 200 years (W-2993, Mullineaux et al., 1975, p. 334). Layer Wn, which overlies Mount St. Helens has been an intermittent but prolific this basal bed, has been dendrochronologically dated at about source of tephra for more than 35 000 years (Mullineaux 450 years old (Crandell, 1971, p. 12). A piece of wood 5 cm and Crandell, 1962; Crandell and Mullineaux, 1973; below St. Helens W tephra near Kootenay Lake has yielded a Crandell et al., 1975; Mullineaux et al., 1975). Individual radiocarbon age of 1220 ± 130 years (GSC-832, Lowdon and tephra layers have been grouped in eight discrete sets, of Blake, 1970, p. 70). which six (J, Y, P, B, W, and T) are postglacial in age (Mullineaux et al., 1975). Sets Y and W and possibly set P have been identified in Canada and are discussed separately Bridge River Tephra below. Set B is of local extent around the vent and likely is Explosive eruption of dacitic pumice from a vent near not present in British Columbia. Set J, comprising tephra Meager Mountain produced a thick welded ash-flow tuff in layers from slightly more than 8000 years old to slightly less upper Lillooet River valley and at least two layers of air-fall than 12 000 years old (Mullineaux et al., 197 5, p. 331-332), is pumice over a large area of southern British Columbia thicker and more extensive than set B and may be present in (Stevenson, 1947; Wilcox, 1965; Nasmi th et al., 1967; British Columbia, although it has not yet been found there. Westgate and Dreimanis, 1967; Westgate et al., 1970; Likewise, set T, approximately 150 to 200 years old, has not Westgate, 1977; \l\athewes and Westgate, 1980). been identified in the province, although it includes one moderately extensive tephra layer which extends east­ Tephra of two eruptions has been identified to date. northeast from Mount St. Helens to near the International During the earlier main eruptive event, tephra was deposited Boundary (Fig. 6; Smith et al., 1968, 197 5; Okazaki et al., in a relatively narrow strip extending east from Meager 1972). Mountain into Alberta (Fig. 6; Nasmith et al., 1967; Westgate et al., 1970). A burnt wood sample from the centre of an 80-cm diameter tree stump enclosed by this tephra near Set Y the vent yielded a date of 2500 ± 50 years (GSC-2571, Set Y, the thickest and coarsest of the Lowdon and Blake, 1978, p. 10). The tree was about Mount St. Helens tephra units, includes more than a dozen 150 years old when it was engulfed by the tephra, thus the layers of pumice, two of which (Yn and Ye) have been found eruption probably occurred about 2350 ± 50 years ago. In the hundreds of kilometres from the source. Layer Ye does not same general area a date of 2480 ± 60 years (GSC-2587, occur in Canada, but layer Yn extends in a long narrow lobe Lowdon and Blake, 1978, p. 10) was obtained on charcoal north-northwest from Mount St. Helens across Washington within fluvially redeposited tephra. These dates are and southern British Columbia into west-central Alberta consistent with limiting dates on Bridge River tephra at other (Fig. 6; Westgate et al., 1970; Mullineaux et al., 197 5). sites in southern British Columbia, including maxima of Crandell et al. ( 1962, p. 067) assigned an approximate 2440 ± 140 and 2450 ± 130 years (GSC-529, Lowdon and Blake, 1968, p. 226-227; GSC-1532, Lowdon and Blake, 1976, age of 3200 years to layer Yn on the basis of two limiting radiocarbon dates of about 3000 and 3500 years. '.\!ear p. 10-11) and a minimum of 2240 ± 130 years (GSC-1520, \l\ount St. Helens, layer Yn is bracketed by radiocarbon dates Lowdon and Blake, 1976, p. 10-1 l).

27 Tephra of a younger weaker eruption from the Meager CONCLUDING REMARKS Mountain area has been found in the Otter Creek Bog The chronology of late Qua ternary geologic and (Westgate, 1977). The eruption apparently spread pumice climatic events in British Columbia has been determined southeast from the vent along a different trajectory from the from radiocarbon dates on organic materials associated with earlier eruption. Peat directly above and below the tephra in sundry sedimentary, volcanic, and archeological de posits. the Otter Creek Bog dates 1860 ± 70 and 2070 ± 80 years Although at present there are hundreds of published old, respec tively (GSC-19 50 and GSC-1939, Westgate, 19 77, radiocarbon dates in British Columbia, most are concentrated p. 2594-2595). in a few areas, thus the chronology of late Qua ternary events for many parts of the province is poorly known. For example, Edziza Tephra there are few radiocarbon dates from northern British Late postglacial tephra surrounds a young vent on Columbia, and the late Quaternary history of most of this region is virtually unknown. Edziza Peak and likely extends eastward in a narrow belt across north-central British Columbia (Fig. 6; Souther, 1976). Even in those parts of the province where t he re is an This tephra has not been studied in detail, but it is a abundance of radiocarbon dates, there are differences of potentially useful stratigraphic marker horiwn in a part of opinion over the timing and climatic significance of some the province where no other tephras are known to occur. A events; in large part, this is due to differing interpretations single radiocarbon date of 1340 ± 130 years (GSC-566, concerning t he genesis, stratigraphic position, and palynology Lowdon et al., 1967, p. 174) from charred wood covered by of certain sedimentary deposits. Al though these differences cinders on Edziza Peak provides an age for the tephra. will not be resolved without detailed field investigations and, in most cases, additional radiocarbon dates, it is likely that the basic late Quaternary geologic-climatic framework White River T ephra outlined in this paper will remain unc hanged. Tephra erupted from a vent in the St. Elias Mountains covers a large area of southern Yukon Territory and east ern REFERENCES Alaska and a lso may occur in westernmost District of Alley, N.F. Mackenzie and northernmost British Columbia (Fig. 6; 1972: The Quaternary history of part of the Rocky Capps, 1916; Bostock, 1952; Berger, 1960; Stuiver et al., Mountains, Foothi ll s, Plains and western 1964; Lerbekmo and Campbell, 1969; Rampton, 1969; Porcupine Hills, southwestern Alberta; Hughes et al., 1972). The tephra consists of two layers, the unpublished Ph.D. t hesis, University of Calgary, older extending north from the source and the younger east. Alberta, 201 p. The younger layer, which is the only one likely to occur 1973: Glacial stratigraphy and the li m its of the Rocky in British Columbia, was deposited approximately 1200 years Mou ntain and Laurentide ice sheets in south­ ago. Dates on wood and charcoal beneath the tephra range western Alberta, Canada; Bulletin of Canadian from 1190 ± 130 to 1300 ± 130 years (GSC-956, Petroleum Geology, v. 2 1, no. 2, p. 153-1 77. Lowd on et al., 1970, p. 481; GSC-1000, Lowd on and Blake, l 970, p. 80). Radiocarbon dates of 1390 ± 70 and 1974: Terra in mapping and Quaternary geology, 1460 ± 70 years (Y-1364 and Y-1363, Stuiver et al., 1964, southern Vancouver island, British Columbia; in p. 260), obtained, respectively, from peat above and below Report of Activities, Part B; Geological Survey Of White River ash near Kaskawulsh Glacier, seem anomalous. Canada, Paper 74 -1 B, p. 209-2 11. The older \Vhi te River tephra layer is about 1500 to J 976a: Late Qua ternary stratigraphy and palaeo- 1800 years old. Dates on organic material immediately climatology, southern Vancouver Island and underlying this layer range from 1750 ± 130 to Strait of J ua n de Fuca, British Columbia, 1990 ± 130 years (GSC-1564, Lowd on and Blake, 1973, Canada rabstract]; in Abstracts; 25th p. 29-30; GSC-400, Lowd on and Blake, 1968, p. 229). Peat International Geological Congress (Sydney), v. 2, just above the tephra dated 1520 ± 100 years old (l-275, sec. 12, p. 487. Fernald, 1962, p. B30). 1976b: Post Pleis tocene g laciat ions in the int erior of British Columbia [abstract]; !.!:! Geomorphology of Summary the Canadian Cordi lier a and I ts Bearing on Mineral Deposits; Geological Association of Non-explosive volcanic activity has occurred at more Canada, Cordiliera n Section, Vancouver, p. 6-7. than JOO sites in British Columbia during Quaternary time. Thin intra-valley flows of alkali olivine basalt are the J 976c: The palynoiogy and palaeoclimatic significance of dominant products of this eruptive activity. The youngest a dated core of Holocene peat, Okanagan Valley, flow is less than 150 years old. southern British Columbia; Canadian Journal of Earth Sciences, v. 13, no. 8, p. 1131-1 I 44. Postglacial tephras deposited in British Columbia, and derived from eruptive centres both within and outside t he 19 79: Middle Wisconsin stratigraphy and c limatic recon­ province, include: Mazama, about 6600 years old; struction, southern Vancouver Island, British St. Helens Yn, 3300 to 3500 years old; St. Helens P (?), Columbia; Quaternary Research, v. 11, no. 2, somewhat older than 2100 years; St. Helens Wn, about p. 213-237. 450 years old; Bridge River (older layer), 2300 to 2400 years Alley, N.F. and Chatwin, S.C. old; Bridge River (younger layer), 1900 to 2000 years old; and 1979: Late P Jeistocene history and geomorphology, Edziza, 1350 years old. in addition, Glacier Peak layer G, southwestern Vancouver Island, British Columbia; approximately 12 750 years old, Edgecumbe (?) tephra, Canadian Journal of Eart h Sciences, v. 16, no. 9, provisionally dated between 9000 and 11 000 years old, and p. 1645-1657. White River tephra, about 1200 years old, may occur in British Columbia, although none has yet been found there. Alley, N.F. and Harris, S.A. 1974: Ple istocene glac ial lake sequences in the Foothills, southwestern Alberta, Canada; Canadian Journal of Earth Sciences, v. 11, no. 9, p. 1220-1235.

28 Alley, N.F. and Thomson, B. Armstrong, J.E. (cont.) 1978: Aspects of environmental geology, parts of 1975b: Quaternary geology, stratigraphic studies and Graham Island, Queen Charlotte Islands; British revaluation of terrain inventory maps, Fraser Columbia Ministry of the Environment, Resource Lowland, British Columbia (92G/I, 2, and parts of Analysis Branch, Bulletin no. 2, 65 p. 92 G/3, 6, 7, and H/4); in Report of Activities, Part A; Geological Survey of Canada, Alley, N.F. and Valentine, K.W.G. Paper 75-JA, p. 377-380. 1977: Palaeoenvironments of the Olympia Interglacial (mid-Wisconsin) in southeastern British Columbia, 1976: Post-Vashon Wisconsin glac ia ti on, Fraser Lowland Canada [abstract]; in Abstracts; International British Columbia, Canada; in Quaternary Union for Quaternary Research, 10th Congress Glaciations in the Northern- Hemisphere, (Birmingham, England), p. 12. ed. D.J. Easterbrook and V. Sibrava; IUGS- UNESCO International Geological Correlation Alley, N.F. and Young, G.K. Programme, Project 73-1-24, Report no. 3, l 978: Environmental significance of geomorphic p. 13-27. processes in the northern Skeena Mountains and southern Stikine Plateau; British Columbia 1977a: Quaternary stratigraphy of the Fraser Lowland; Ministry of the Environment, Resource Analysis Geological Association of Canada, Mineralogical Branch, Bulletin no. 3, 83 p. Association of Canada, Society of Economic Geologists, Canadian Geophysical Union, Joint Alley, N.F., Valentine, K.W.G., and Fulton, R.J. Annual Meetings (Vancouver), Field trip Paleoenvironments of the middle Wisconsin, Guidebook, Trip 10, 20 p. southcentral British Columbia; Canadian Journal of Earth Sciences. (in press). I 977b: Qua ternary geology of the Fraser Lowland (Field Trip no. 6); in Geological Excursions in the Pacific Anderson, r .E. Northwest, - ed. E.H. Brown and R.C. Ellis; 1967: Stratigraphy of late Pleistocene and Holocene Western Washington University, Department of sediments from the Strait of Juan de Fuca; Geology, Bellingham, Washington, p. 204-226. unpublished Ph.D. thesis, University of Washington, Seattle, 179 p. 1981: Post-Vashon Wisconsin glaciation, Fraser Lowland, British Columbia; Geological Survey of 1968: Seaward terminus of the Vashon continental Canada, Bulletin 322, 34 p. glacier in the Strait of Juan de Fuca; Marine Geology, v. 6, no. 6, p. 419-438. Armstrong, J.E. and Brown, W.L. 195 3: Ground-water resources of Surrey \ilunic:ipality, Anderson, J.H. British Columbia; Geological Survey of Canada, 1970: A geobotanical study in the A tlin region in Water Supply Paper no. 322, 48 p. northwestern British Columbia and south-central Yukon Territory; unpublished Ph.D. thesis, 1954: Late Wisconsin marine drift and associated sedi­ Michigan State University, East Lansing, 380 p. ments of the lower Fraser Valley, British Columbia, Canada; Geological Society of Anderton, L.J. America, Bulletin, v. 65, no. 4, p. 349-364. 1970: Qua ternary stratigraphy and geomorphology of the lower Thompson Valley, British Columbia; Armstrong, J.E. and Clague, J.J. unpublished M.A. thesis, University of British 1977: Two major Wisconsin lithostratigraphic units in Columbia, Vancouver, 100 p. southwest British Columbia; Canadian Journal of Earth Sciences, v. 14, no. 7, p. 1471-1480. Andrews, J.T. and Barry, R.G. 1978: Glacial inception and disintegration during the Armstrong, J.E. and Hicock, S.R. last glaciation; Annual Review of Earth and 1975: Quaternary landscapes: present and past - at Planetary Sciences, v. 6, p. 205-228. Mary Hill, Coquitlam, British Columbia (92G/2f); in Report of Ac ti vi ties, Part B; Geological Survey Andrews, J.T. and Retherford, R.M. Of Canada, Paper 75-IB, p. 99-103. 1978: A reconnaissance survey of late Qua ternary sea levels, Bella Bella/Bella Coola region, central 1976: Quaternary multiple valley development of the British Columbia coast; Canadian Journal of Earth lower Coquitlam Valley, Coquitlam, British Sciences, v. 15, no. 3, p. 341-350. Columbia (92G/7c); in Report of Activities, Antevs, E.V. Part B; Geological Survey of Canada, Paper 76-JB, p. 197-200. 1948: Climatic changes and pre-white man; University of Utah, Bulletin, v. 38, no. 20, p. 168-191. Armstrong, J.E. and Tipper, H.W. Armstrong, J.E. l 948: Glaciation in north central British Columbia; !966a: Glacial studies, Kitimat-Terrace area; in Report American Journal of Science, v. 246, no. 5, p. 283-310. of Activities, May to October, 1965; Geological Survey of Canada, Paper 66-1, p. 50. Armstrong, J.E., Crandell, n.R., Easterbrook, D.J., and Noble, J.B. l 966b: Glaciation along a major fiord valley in the Coast Mountains of British Columbia, Canada 1965: Late Pleistocene stratigraphy and chronology in [abstract]; 0_ Program, 1966 Annual Meetings; southwestern British Columbia and northwestern Washington; Geological Society of America, Geological Society of America, 79th Annual 'vleeting (San Franc:isco), p. 7. Bulletin, v. 76, no. 3, p. 321-330. Beach, H.H. and Spivak, J. 1975a: Fraser Lowland - Canada; in The Last Glaciation; 1943: The origin of Peace River canyon, British JUGS-UNESCO International Geological Correla- tion Programme, Project 73-1-24, Western Columbia; American Journal of Science, v. 241, no. 6, p. 366-376. Washington State College, Department of Geology, Bellingham, Washington, Guidebook for Field Conference, p. 74-97.

29 Bement, W.O. Bryan, A.L. 1972: The sedimentologic and paleogeographic history 1969: Early man in America and the late Ple istocene of the lower Kicking Horse River valley, south­ chronology of we stern Canada and Alaska; east British Columbia, during deglaciation; Current Anthropology, v. LO, no. 4, p. 339-365. unpublished M.Sc. thesis, University of Il linois, Buckley, J .D. and Willis, E.H. Chicago, 103 p. 1970: Isotopes' radiocarbon measurements VIII; Benedict, J.B., Jr. Radiocarbon, v. 12, no. 1, p. 87-129. l 968a: Neoglac ial history of the Colorado Front Range; Buddemeier, R.W. unpublished Ph.D. thesis, University of Wisconsin, 1969: A radiocarbon study of the varved marine Madison, 84 p. sediments of Saanich Inlet, British Columbia; l 968b: Recent glacial history of an alpine area in the un published Ph.D. thesis, LJniversi ty of Colorado Front Range, U.S.A. II. Dating the Washington, Seattle, 125 p. glacial deposits; Journal of Glaciology, v. 7, Capps, S.R. no. 49, p. 77-87. 191 6: An ancient volcanic eruption in the upper Yukon l 973: Chronology of cirque glaciation, Colorado F ront basin; in Shorter Contributions to Gene ra l Range; Quaternary Research, v. 3, no. 4, Geology;-191 5; United States Geological Survey, p. 584-599. Professional Paper 95, p. 59-64. Berger, A.R. Chatwin, S.C. 1960: On a recent volcanic ash deposit, Yukon 1974: Glacial moveme nts and surficial deposits on Territory; Geological Association of Canada, southwestern Vancouve r Island; unpubli shed B.Sc. Proceedings, v. 12, p. l l 7-l 18. thesis, University of British Columbia, Department of Geological Sciences, Vancouver, Borchardt, G.A., Harward, M.E., and Schmitt, R.A. 77 p. 1971: Correlation of volcanic ash deposits by activation analysis of glass separates; Qua t ernary Research, Church, M. and Ryder, J.M. v. 1, no. 2, p. 247-260. 1972: Paraglacial sediment a tion: a consider a t i on of fluv ial processes controll ed by glaciation; Borchardt, G.A., Norgren, J.A., and Harward, M.E. Geological Society of America, Bu lletin, v. 83, 1973: Correlation of ash layers in peat bogs of eastern no. 10, p. 3059-3072. Oregon; Geological Society of America, Bulletin, v. 84, no. 9, p. 3101-3108. Clague, J .J. 1973: Late Cenozoic geology of the southe rn Rocky Borns, H.W., Jr. and Goldthwait, R.P. Mountain Trench, British Columbia; unpubli shed 1966: Late-Pleistocene fluc tuations of Kaskawulsh Ph.D. thesis, Universi ty of Br itis h Columbia, Glacier, southwestern Yukon Territory, Canada; Vancouver, 274 p. American Journal of Science, v. 264, no. 8, p. 600-619. Reprinted (1969) in lcefield Ranges 1975a: Glacier-flow patterns and the origin of late Research Project Scientific Results, Volume 1, Wi sconsinan till in the southern Rocky Mountain ed. V.C. Bushnell and R.H. Ragle; American Trenc h, British Col umbia; Geological Socie t y of Geographical Society, New York, New York, America, Bulletin, v. 86, no. 6, p. 721 -731. Arctic Institute of North America, 'vlontreal, 197 5b: La te Qua ternary sea-level fluctuations, Pacific Quebec, p. 187-196. coast of Canada and adjacent areas; in Report of Bostock, H.S. Activities, Part C; Geological Su rvey-of Canada, 1952: Geology of northwest Shakwak Valley, Yukon Paper 75-lC, p. 17 -21. Territory; Geological Survey of Canada, 1975c: Late Quaternary sed iments and geomorphic Memoir 267, 54 p. history of the southe rn Rocky Mountain Trench, Boydell, A.N. Br itish Columbia; Canadian Journal of Earth 1970: Relationship of late-Wisconsin Rocky Mountain Sciences, v. 12, no. 4, p. 595-605. and Laurentide ice in the vicinity of Sundre, 1976a: Quadra Sand and its relation to the late Wisconsin Alberta; unpublished M.Sc . thesis, University of g laciation of southwest British Columbia; Calgary, Alberta, 130 p. Canadian Journal of Ear th Sc iences, v. 13, no. 6, 1972: Multiple glaciation in the foothills, Rocky p. 803-815. Mountain House area, Alberta; unpublished P h.D. l 976b: Quadra Sand and the timing of the late Wisconsin thesis, University of Calgary, Alberta, 128 p. glacial advance in southwest British Columbia; in 1978: Multiple glaciation in the Foothills, Rocky Qua ternary Gl aciations in the Northern Mountain House area, Alberta; Alberta Research Hem isphere, ed. D.J . Easterbrook and V. Sibrava; Council, Bulletin 36, 35 p. IUGS-UNESCO International Geological Correlation Programme , Project 73- 1-24, Report Bretz, J.H. no. 3, p. 315-326. 1920: The Juan de Fuca lobe of the Cordilleran Ice Sheet; Journal of Geology, v. 28, no. 4, l 977a: Quadra Sand: a study of the late Pleistocene p. 333-339. geology and geomorphir history of coastal southwest British Columbia; Geological Survey of Brown, R.L. and Psutka, J.F. Canada, Paper 77-17, 24 p. 1980: Structural and stratigraphic set ting of the Downie slide, Columbia River valley, British Columbia; l 977b: Surf icial geology, Ki ti mat, British Columbia; Canadian Journal of Earth Sciences, v. 17, no. 6, Geological Survey of Canada, Open File 470. p. 698-709.

30 Clague, J .J. (cont.) Curry, R.R. l 978a: Mid-Wisconsinan climates of the Pacific 1968: Quaternary climatic and glacial history of the Northwest; in Current Research, Part B; Sierra Nevada, California; unpublished Ph.D. Geological SUrvey of Canada, Paper 78-LR, thesis, University of California, Berkely, 238 p. p. 95-100. I 969: Holocene climatic and glacial history of the 1978b: Terrain hazards in the Skeena and Kitimat river central Sierra Nevada, California; in United basins, British Columbia; in Current Research, States Contributions to Quaternary Research, Part A; Geological Survey of Canada, ed. S.A. Schumm and W.C. Bradley; Geological Paper 78-lA, p. 183-188. Society of America, Special Paper 123, p. 1-47. 1980: Late Qua ternary geology and geochronology of Damon, P.E., Ferguson, C.W ., Long, A., and Wallick, E.J. British Columbia. Part I: Radiocarbon dates; 1974: Dendrochronologic calibration of the radiocarbon Geological Survey of Canada, Paper 80-13, 28 p. time scale; American Antiquity, v. 39, no. 2, p. 350-366. Clague, J.J. and Hicock, S.R. 1976: Sand and gravel resources of Ki timat, Terrace, Damon, P.E., Long,/\., and Wallick, E.J. and Prince Rupert, British Columbia; in Report of 1972: Dendrochronologic calibration of the carbon-14 Activities, Part A; Geological Survey-of Canada, time scale; in Proceedings of the Eighth Paper 76-lA, p. 273-276. lnterna tional Radiocarbon Dating Conference; Royal Society of New Zealand, Lower Hutt, Clague, J.J., Armstrong, J.E., and Mathews, W.H. New Zealand, v. I, p. A29-A43. 1980: Advance of the late Wisconsin Cordilleran Ice Sheet in southern British Columbia since Davis, J.O. 22,000 yr B.P.; Quaternary Research, v. 13, no. 3, 1977: Qua ternary tephrochronology of the Lake p. 322-326. Lahontan area, Nevada and California; unpublished Ph.D. thesis, University of Idaho, Crandell, D.R. Moscow, Idaho, 168 p. 1963: Surficial geology and geomorphology of the Lake Tapps quadrangle, Washington; United States Davis, N.F.G. and Mathews, W.H. Geological Survey, Professional Paper 388-A, 1944: Four phases of glaciation with illustrations from 84 p. southwestern British Columbia; Journal of Geology, v. 52, no. 6, p. 403-413. I 965a: Alpine glaciers at Mount Rainier, Washington, during late Pleistocene and Recent time Dawson, G.M. [abstract]; in Abstracts for 1964; Geological 1881: Additional observations on the superficial geology Society of America, Special Paper 82, p. 34-35. of British Columbia and adjacent regions; Quarterly Journal of the Geological Society of 1965b: The glacial history of western Washington and London, v. 37, p. 272-285. Oregon; in The Quaternary of the United States, ed. H.E. Wright, Jr. and D.G. Frey; Princeton Denton, G.H. and Karlen, W. University Press, Princeton, New Jersey, 1973: Holocene climatic variations - their pattern and p. 341-353. possible cause; Quaternary Research, v. 3, no. 2, p. 155-205. 197 I: Postglacial Jahars from Mount Rainier volcano, Washington; United States Geological Survey, 1977: Holocene glacial and tree-line variations in the Professional Paper 677, 75 p. White River valley and Skolai Pass, Alaska and Yukon Territory; Quaternary Crandell, D.R. and Miller, R.D. Research, v. 7, no. I, p. 63-11 I. 1964: Post-Hypsithermal glacier advances at Mount Rainier, Washington; 0_ Geological Survey Denton, G.H. and Stuiver, M. Research 1964, Chapter D; United States I 966: Neoglacial chronology, northeastern St. Elias Geological Survey, Professional Paper 501-D, Mountains, Canada; American Journal of Science, p. DI 10-Dl 14. v. 264, no. 8, p. 577-599. Reprinted (1969) in lcefield Ranges Research Project Scientifte Crandell, D.R. and Mullineaux, D.R. Results, Volume 1, ed. V.C. 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31 Dreimanis , A. and Raukas, A. Eisbac her, C.H. (cont.) 197 5: Did Middle Wi sconsin, Middle Weichselian, and 1979: r irs t-order regionaliza t i on of lands I ide .-har­ the ir equivale nts re present an interglacial , or an ac teris t iPacific Northwest; in Quaternary Columbia; Geological Society of Ame rica, Glacia tions in the Northern Hemisphere, ed. Bulletin , v. 79, no. 8, p. 1075- 1080. D.J. Easterbrook and V. Sibrava; JUG S-UN ESCO International Geological Corre lation Programme , 1969: Glacia l lake history, southern Interior P lateau, Projert 73- 1- 24 , Re port no. 3, p. 90-98. British Columbia; Geological Survey of Canada, Paper 69-37, 14 p. 1976b: Qua ternary geology o f the Pacific Nor thwest; in Qua ternary Stratigraphy of North America, 1971: Radiocarbon geochronology of southern British ed. W.C . Mahaney; Dowden, Hutchinson & Ross, Columbia; Geological Survey of Canada, Inc ., Stroudsburg, Pe nnsylvania, p. 44 1- 462. Paper 7 1-37, 28 p . Ei sbache r, C .H. 197 5a: Quaternar y geology and geomorphology, Nicola­ 197 1: Natura l slope fa ilure, northeaste rn Skeena Vernon area, British Columbia (82 L W 1/ 2 a nd Mounta ins; Canadian Geotechnical J ourna l, v. 8, 92I E I /2); Geologica 1 Su rvey of Canada, no. 3, p. 384 - 390 . Memoir 380, 50 p.

32 Fulton, R.J. (cont.) Hansen, H.P. 1975b: Quaternary stratigraphy south central British 1937: Postglacial forest succession and climate in the Columbia; in The Last Glaciation; JUGS-UNESCO Puget Sound region; unpublished Ph.D. thesis, International Geological Correlation Programme, University of Wa shington, Seattle, 43 p. Project 73-1-24, We stern Washington State 19 38 : Postglacial forest succession and climate in the College, Department of Geology, Bellingham, Puget Sound region; Ecology, v. 19, no. 4, \V ashing ton, Guidebook for F 1eld Conference, p. 528-542. p. 98-124. l939a: Paleoecology of a central Washington bog; 1976: Quaternary history south-central British Columbia Ecology, v. 20, no. 4, p. 563-568. and correlations with adjacent areas; in Qua ternary Glaciations in the Northern I 939b: Pollen analysis of a bog in northern Idaho; Hemisphere, ed. D.J. Easterbrook and V. Sibrava; American Journa l of Botany, v. 26, no. 4, IUGS-U".JESCO International Geological p. 225-228. Correlation Programme, Project 73-1-24, Report 1939c: Pollen analysis of a bog near Spokane, no. 3, p. 62-89. Washington; Torrey Botanical Club, P,ulletin, Fu! ton, R. J. and Halstead, E.C. v. 66, no. 4, p. 215-220. 1972: Quaternary geology of the southern Canadian 1940a: Paleoecology of a montane peat deposit at Cordillera; 24th International Geological Congress Bonaparte Lake, Washington; Northwest Science, (Montreal), Guidebook, Field Excursion A02, 49 p. v. 14, no. 3, p. 60-68. Fulton, R.J. and Smith, G.W. ! 940b: Paleoecology of two peat bogs in southwestern 1978: Late Pleistocene stratigraphy of so uth-central British Columbia; American Journal of Botany, British Columbia; Canadian Journal of Earth v. 27, no. 3, p. 144-149. Sciences, v. l 5, no. 6, p. 97 1-980. 1941 a: Further pollen studies of post Pleistocene bogs in Fulton, R.J ., Armstrong, J.E., and Fyles, J .G. the Puget Lowland of Washington; Torrey l 976: Stratigraphy and palynology of late Qua ternary Botanical Club, Bulletin, v. 68, no. 3, p. 133-148. sediments in the Puget Lowland, Washington: discussion; Geological Society of America, 1941 b: Paleoecology of a bog in the spruce-hemlock P,ulletin, v. 87, no. I, 153- l 55. climax of the Olympic Peninsula; American Midland Naturalist, v. 25, no. 2, p. 29 0-297. Fyles, J.G. 1956: Surficial geology of the Horne Lake and Parksville 1943: A pollen study of two bogs on Orcas Island, of the map-areas, Vancouver Island, British Columbia; San Juan Is lands, Washington; Torrey Botanical unpublished Ph.f). thesis, Ohio State University, Club, Bulletin, v. 70, no. 3, p. 236-243. 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Philosophical Society, Transactions, new ser ., 1980: Pleistocene climate determined from stable v. 37, pt. 1, p. 1-130. isotope and geochronologic studies of speleothem; l 947b: Climate versus fire and soil as factors in unpublished Ph.D. thesis, McMaster Un iversity, postglacial forest succession in the Puget Lowland Hamilton, 467 p. of Washington; American Journal of Science, Gascoyne, M., Schwarcz, H.P., and Ford, D.C. v. 24 5, no. 5, p. 265-286. l 980: A palaeotempera ture record for the mid­ 1948: Postglacial forests of the Glacier National Park Wisconsin in Vancouver Island; Nature, v. 285, region; Ecology, v. 29, no. 2, p. 146-152. no . 5765, p. 474-476. 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33 Harris, S.A. and Boydell, A.N. Heusser, C.J. (cont.) 1972: Glacial history of the Bow River and Red Deer 1967: Pleistocene and postglacial vegetation of Alaska River areas and the adjacent Foothills; in and the Yukon Territory; ~ Arctic Biology, Mountain Geomorphology: Geomorphological Proceedings of the Biology Colloquium, Processes in the Canadian Cordillera, ed. H.P. Hansen; Oregon State University Press, ed. H.O. Slaymaker and H.J. McPherson; Tantalus Corvallis, Oregon, p. 131-151. Research Limited, Vancouver, British Columbia, 1972: Palynology and phytogeographical significance of p. 47-53. a late-Pleistocene refugium near Kalaloch, Harris, S.A. and Howell, J. Washington; Qua ternary Research, v. 2, no. 2, 1977: Chateau Lake Louise moraines - evidence for a p. 189-201. new Holocene glacial event in southwest Alberta; l 973a: Age and environment of allochthonous peat clasts Bulletin of Canadian Petroleum Geology, v. 25, from the Bogachiel River valley, Washington; no. 3, p. 441-455. Geological Society of America, Bulletin, v. 84, Harris, S.A. and Waters, R.R. no. 3, p. 797-804. J 977: Late Quaternary history of southwest Alberta, a l 973b: Environmental sequence following the Fraser progress report; Bulletin of Canadian Petroleum advance of the Juan de Fuca Jobe, Washington; Geology, v. 25, no. l, p. 35-62. Quaternary Research, v. 3, no. 2, p. 284-306. Harrison, J.E. 1974: Quaternary vegetation, climate, and glaciation of I 976a: Dated organic material below Mazama(?) tephra: the Hoh River valley, Washington; Geological Elk Valley, British Columbia; in Report of Society of America, Bulletin, v. 85, no. 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Hicock, S.R J 977: The paleoecology of a raised bog and associated 1976: Quaternary geology: Coquitlam-Port Moody area, deltaic sediments of the Fraser River delta; British Columbia; unpublished M.Sc. thesis, unpublished Ph.D. thesis, University of British University of British Columbia, Vancouver, 114 p. Columbia, Vancouver 202 p. 1980: Pre-Fraser Pleistocene stratigraphy, geo- Hebda, R.J. and Rouse, G.E. chronology, and paleoecology of the Georgia 1979: Palynology of two Holocene cores from the Depression, British Columbia; unpublished Ph.D. Hesquiat Peninsula, Vancouver Island, British thesis, University of Western Ontario, London, Columbia; Syesis, v. 12, p. 121-130. 231 p. Heginbottom, J.A. Holland, S.S. 1972: Surficial geology of Taseko Lakes map-area (92-0) 1964: Landforms of British Columbia, a physiographic British Columbia; Geological Survey of Canada, outline; British Columbia Department of Mines Paper 72-14, 9 p. and Petroleum Resources, Bulletin no. 48, 138 p. 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34 Hughes, O.L., Rampton, V.N., and Rutter, N.W. Lerbekmo, J.F. and Campbell, F.A. 1972: Quaternary geology and geomorphology, southern 1969: Distribution, composition, and source of the White and central Yukon (northern Canada); 24th River ash, Yukon Territory; Canadian Journal of lnterna tional Geological Congress (Montreal), Earth Sciences, v. 6, no. 1, p. 109-116. Guidebook, Field Excursion All, 59 p. Lowdon, J.A. and Blake, W., Jr. Ives, P.C., Levin, B., Oman, C.L., and Rubin, M. 1968: Geological Survey of Canada radiocarbon 1967: U.S. Geological Survey radiocarbon dates IX; dates VII; Radiocarbon, v. JO, no. 2, p. 207-245. Radiocarbon, v. 9, p. 505-529. Reprinted ( 1968) as Geological Survey of Canada, Paper 68-2B, 39 p. Jackson, L.E., Jr. 1977: Quaternary stratigraphy and terrain inventory of 1970: Geological Survey of Canada radiocarbon the Alberta portion of the Kananaskis Lakes dates IX; Radiocarbon, v. 12, no. 1, p. 46-86. 1:250 000 sheet (82-J); unpublished Ph.D. thesis, Reprinted ( 1970) as Geological Survey of Canada, University of Calgary, Alberta, 478 p. Paper 70-2B, 41 p. 1979: A catastrophic glacial outburst flood (jokulhlaup) 1973: Geological Survey of Canada radiocarbon mechanism for debris flow generation at the dates XIII; Geological Survey of Canada, Spiral Tunnels, Kicking Horse River basin, British Paper 73-7, 61 p. Columbia; Canadian Geotechnical Journal, v. 16, 197 5: Geological Survey of Canada radiocarbon no. 4, p. 806-813. dates XV; Geological Survey of Canada, 1980: Glacial history and stratigraphy of the Alberta Paper 7 5-7, 32 p. portion of the Kananaskis Lakes map area; 1976: Geological Survey of Canada radiocarbon Canadian Journal of Earth Sciences, v. 17, no. 4, dates XVI; Geological Survey of Canada, p. 459-477. Paper 76-7, 21 p. Jennings, A.H. j 978: Geological Survey of Canada radiocarbon 1951: The glacial geomorphology of the Sunwapta Pass dates XVJIJ; Geological Survey of Canada, area, Jasper National Park, Alberta, Canada; Paper78-7, 20 p. unpublished M.Sc. thesis, University of Iowa, Iowa City. 1979: Geological Survey of Canada radiocarbon dates XIX; Geological Survey Johnston, W.A. of Canada, Paper 79-7, 57 p. 1921: Sedimentation of the Fraser River delta; Geological Survey of Canada, Memoir 125, 46 p. Lowdon, J.A., Fyles, J.G., and Blake, W., Jr. 1967: Geological Survey of Canada radiocarbon de Jong, S.H. and Siebenhuener, H.F.W. dates VI; Radiocarbon, v. 9, p. 156-197. 1972: Seasonal and secular variations of sea level on the Reprinted (196 7) as Geological Survey of Canada, Pacific coast of Canada; Canadian Surveyor, Paper 67-2B, 42 p. v. 26, no. 1, p. 4-19. Lowdon, J.A., Robertson, J.M., and Blake, W., Jr. Keddie, G.R. 1971: Geological Survey of Canada radiocarbon 1979: The late ice age of southern Vancouver Island; dates XI; Radiocarbon, v. 13, no. 2, p. 255-324. Midden (Archaeological Society of British Reprinted (I 97 I) as Geological Survey of Canada, Columbia), v. 11, no. 4, p. 16-22. Paper 71-7, 70 p. Kellerhals, P. and Murray, J.W. 1977: Geological Survey of Canada radiocarbon 1969: Tidal flats at Boundary Bay, Fraser River delta, dates XVII; Geological Survey of Canada, British Columbia; Bulletin of Canadian Petroleum Paper 77-7, 25 p. Geology, v. 17, no. I, p. 67-91. Reprinted (1976) in Holocene Tidal Sedimentation, ed. Lowdon, J.A., Wilmeth, R., and Blake, W., Jr. G. deV. Klein; Dowden, Hutchinson & Ross, Inc., 1969: Geological Survey of Canada radiocarbon Stroudsburg, Pennsylvania, p. 118-142. dates VIII; Radiocarbon, v. 11, no. l, p. 22-42. Kerr, F .A. Reprinted (1969) as Geological Survey of Canada, Paper 69-2B, 21 p. 1934: Glaciation in northern British Columbia; Royal Society of Canada, Transactions, ser. 3, v. 28, 1970: Geological Survey of Canada radiocarbon sec. 4, p. 17-31. dates X; Radiocarbon, v. 12, no. 2, p. 4 72-485. Kind, N.V. Reprinted (1970) as Geological Survey of Canada, Paper 70-2B (second report), 14 p. 1972: Late Quaternary climatic changes and glacial events in the old and new world - radiocarbon 1972: Geological Survey of Canada radiocarbon chronology; in Section 12, Quaternary Geology; dates XI.I; Geological Survey of Canada, 24th International Geological Congress Paper 72-7, 26 p. (Montreal), p. 55-61. 1974: Geological Survey of Canada radiocarbon Kiver, E.P. dates XIV; Geological Survey of Canada, 1974: Holocene glaciation in the Wallowa Mountains, Paper 74-7, 11 p. Oregon; in Quaternary Environments: Proceedings of a Symposium, ed. W.C. Mahaney; Luckman, B.H. and Osborn, G.D. York University, Geographical Monographs, no. 5, 1979: Holocene glacier fluctuations in the middle p. 169-195. Canadian Rocky Mountains; Quaternary Research, v. 11, no. 1, p. 52-77. Lemke, R.W ., Mudge, M.R., Wilcox, R.E., and Powers, H.A. Luternauer, J.L. and Murray, J.W. 1975: Geological setting of the Glacier Peak and 1973: Sedimentation on the western delta-front of the Mazama ash-bed markers in west-central Montana; United States Geological Survey, Fraser River, British Columbia; Canadian Journal Bulletin 1395-H, 31 p. of Earth Sciences, v. 10, no. 11, p. 1642-1663.

35 Luternauer, J.L. and Swan, D. Mathews, W. H. (cont.) 1978: Kitimat submarine slump deposit(s): a preliminary 1955: Late Pleistocene divide of the Cordilleran Ice report; in Current Research, Part A; Geological Sheet [abstract); Geological Society of America, Survey oTCanada, Paper 78-IA, p. 327-332. Bulletin, v. 66, no. 12, pt. 2, p. 1657. Mack, R.N. 1963: Qua ternary stratigraphy and geomorphology of 1971: Pollen size variation in some western North the Fort St. John area, northeastern British American pines as related to fossil pollen identi­ Columbia; British Columbia Department of Mines fication; Northwest Science, v. 45, no. 4, and Petroleum Resources, Victoria, 22 p. p. 257-269. 1978: Qua ternary stratigraphy and geomorphology of Mack, R.N., Bryant, V.M., Jr., and Fryxell, R. Charlie Lake (94A) map-area, British Columbia; 1976: Pollen sequence from the Columbia Basin, Geological Survey of Canada, Paper 76-20, 25 p. 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Mack, R.N., Rutter, N.W., and Valastro, S. 1978: Hope rockslides, British Columbia, Canada; in I 978c: Late Quaternary pollen record from the Sanpoil Rockslides and Avalanches, 1, Natural River valley, Washington; Canadian Journal of Phenome na, ed. B. Voight; Elsevier Scientific Botany, v. 56, no . 14, p. 1642-1650. Publishing Company, New York, New York, 1979: Holocene vegetation history of the Okanogan p. 259-275. Valley, Washington; Quaternary Research, v. 12, Mathews, W.H. and Shepard, F .P. no. 2, p. 212-225. 1962: Sedimentation of Fraser River delta, British Mathewes, R. W. Columbia [includes Discussion by K. Terzaghi]; 197 3a: A palynological study of postglacial vegetation American Association of Petroleum Geologists, changes in the University Research Forest, south­ Bulletin, v. 46, no. 8, p. 1416-1443. western British Columbia; Canadian Journal of Reprinted (1976) in Modern Deltas; American Botany, v. 51, no. 11, p. 2085-2103. Association of Petroleum Geologists, Reprint Series, no. 18, p. 94-116. 197 3b: Paleoecology of postglacial sediments in the Fraser Lowland region of British Columbia; Mathews, W.H., Fyles, J.G., and Nasmith, H.W. unpublished Ph.D. thesis, University of British 1970: Postglacial crustal movements in southwestern Columbia, Vancouver, 77 p. British Columbia and adjacent Washington State; Canadian Journal of Earth Sciences, v. 7, no. 2, 1979: A paleoecological analysis of Quadra Sand at pt. 2, p. 690-702. Point Grey, British Columbia, based on indicator pollen; Canadian Journal of Earth Sciences, v. 16, McCallum, K.J. and Wittenberg, J. no. 4, p. 847-858. 1962: University of Saskatchewan radiocarbon dates Ill; Radiocarbon, v. 4, p. 71-80. Mathewes, R.W. and Rouse, G.E. 197 5: Palynology and paleoecology of postglacial sedi­ McKenzie, G.D. ments from the lower Fraser River canyon of I 970: Some properties and age of volcanic ash in British Columbia; Canadian Journal of Earth Glacier Bay National Monument; Arctic, v. 23, Sciences, v. 12, no. 5, p. 745-756. no. I, p. 46-49. Mathewes, R.W. and Westgate, J.A. McPherson, H.J. 1980: Bridge River tephra: revised distribution and 1963: The glacial geomorphology of the upper Red Deer significance for detecting old carbon errors of River valley, Alberta; unpublished M.Sc. thesis, limnic sediments in so uthern British Columbia; University of Calgary, Alberta, 41 p. Canadian Journal of Earth Sciences, v. 17, no. 11, 1970: Landforms and glacial history of the upper North p. 1454-1461. Saskatchewan Valley, Alberta, Canada; Canadian Mathewes, R.W., Borden, C.E., and Rouse, G.E. Geographer, v. 14, no. 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36 Miller, M.M. Nasmith, H. 1976: Qua ternary erosional and stratigraphic sequences I 962: Late glacial history and surficial deposits of the in the Alaska-Canada Boundary Range; in Okanagan Valley, British Columbia; British Quaternary Stratigraphy of North America, Columbia Department of Mines and Petroleum ed. W.C. Mahaney; Dowden, Hutchinson & Ross, Resources, Bulletin no. 46, 46 p. Inc., Stroudsburg, Pennsylvania, p. 463-492. I 970: Pleistocene geology of the Queen Charlotte Miller, M.M. and Anderson, J.H. Islands and southern British Columbia; in Early l 974a: Out-of-phase Holocene climatic trends in the Man and Environments in Northwest North maritime and continental sectors of the Alaska­ America, ed. R.A. Smith and J.W. Smith; Canada Boundary Range; in Qua ternary University of Calgary, Archaeological Environments: Proceedings of-a Symposium, Association, Calgary, Alberta, p. 5-9. ed. W.C. Mahaney; York University, Geographical Nasmith, H.W. and Mercer, A.G. Monographs, no. 5, p. 33-58. 1979: Design of dykes to protect against debris flows at 1974b: Alaskan Glacier Commemorative Project, Port Alice, British Columbia; Canadian Phase IV: Pleistocene-Holocene sequences in the Geotechnical Journal, v. 16, no. 4, p. 748-757. Alaska-Canada Boundary Range; in National Nasmith, H., Mathews, W.H., and Rouse, G.E. Geographic Society Research ReportS, Abstracts 1967: Bridge River ash and some other Recent ash beds and Reviews of Research and Exploration in British Columbia; C anadian Journal of Earth Authorized under Grants from the National Sciences, v. 4, no. 1, p. 163-170. Geographic Society during the Year 1967, ed. P.H. Oehser; National Geographic Society, Nelson, J.G. Washington, D.C., p. 197-223. 1963: The origin and geomorphological significance of the Morley Flats, Alberta; Bulletin of Canadian Miller, R.D. 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Peng, T .-H., Goddard, J .G ., and f'>roecker, W.S. 197 5: Widespread late glacial and postglacial tephra 1978: A direct comparison of 14 C and 230 Th ages at deposits from Mount St . .Helens volcano, Searles Lake, California; Quaternary Research, Washington; United States Geological Survey, v. 9, no. 3, p. 319-329. Journal of Research, v. 3, no. 3, p. 329-335. Pi teau, D.R. Mullineaux, D.R., Waldron, H.H., and Rubin, M. 1977: Regional slope-stability controls and engineering 1965: Stratigraphy and chronology of late interglacial geology of the Fraser Canyon, British Columbia; and early Vashon glacial time in the Seattle area, ~ Landslides, ed. D.R. Coates; Geological Society Washington; United States Geological Survey, of America, Reviews in Engineering Geology, v. 3, Bulletin 1194-0, I 0 p. p. 85-111. 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37 Porter, S.C. (cont.) R ichmond, G.M., Fryxell, R., Ne ff , G.E., and Weis, P.L. 1966: Pleistocene geology of Ana ktuvuk Pass, central 1965: The Cordilleran Ice Sheet of the nort he rn Rocky Brooks Range, Alaska; Arctic Institute of North Mountains, and related Quaternary history of the America, Technical Paper no. 18, JOO p. Columbia Plateau; in The Qua ternary of t he United States, ed. H.E. Wright, J r . and D.G. Frey; 1976: Pleistocene glaciation in the southern part of the Princeton Universit y P ress, Princeton, North Cascade Range, Washington; Geological New Jersey, p. 231- 242. Societ y of America, Bulletin, v. 87, no . 1, p. 6 1-75. Riddihough, R.P. 1979: Gravity and structure of an active margin - 1978: Glacier Peal< tephra in the North Cascade Range, British Columbia and Washington; Canadian Washington: stratigraphy, distribution, and Journal of Earth Sc ie nces, v. 16, no. 2, p. 350-363. relationship to late-glacial events; Quaternary Research, v. 10, no. 1, p. 30-41. 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38 Ryder, J.M. (cont.) Stalker, A. \!\acS. (cont.) 197 la: Some aspects of the morphometry of paraglacial l 97 3: Surficia l geology of t he Kananaskis Research alluvial fans in south-central British Columbia; Forest a nd Marmot Creek basin region of A lberta; Canadian Journal of Earth Sciences, v. 8, no. IO, Geological Survey of Canada, Paper 72-5 1, 25 p. p. 1252-1264 . Stalker, A. Macs. and Harrison, J .E. l 971 b: The stratigraphy and morphology of para-glaci;.il 1977: Qua ternary glaciation of the Watert on-Castle a lluvial fans in south- central British Columbia; R iv e r region of Alberta; Bulletin of Canadian Canadian Journal of Earth Sciences, v. 8, no. 2, Petroleum Geology, v. 25, no. 4, p. 882-906. p. 279-298. Stanton, R.B. 1976: Terrain inventory and Quaternary geology 1898: The great land-slides of the Canadian Pacific Ashcroft, British Columbia (92-1 NW); Geological Railway in British Columbia; Instit ut ion of Civil Survey of Canada, Paper 74-49, 17 p. 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39 Sutherland Brown, A. (cont.) VanDine, D.F. 1969: Aiyansh Java flow, British Columbia; Canadian 1974: Geotechnical and geological engi neering study of Journa l of Earth Sciences, v. 6, no. 6, Drynoch landslide, British Columbia; unpublished p. 1460-1468 . M.Sc. thesis, Queen's University, Ki ngston, Ontario, 122 p. Sutherland Brown, A. and Nasmith, H. 1962: The glaciation of t he Queen Charlotte Islands; 1980: Engineering geology and geotechnical study of C anadian Field Naturalist, v. 76, no. 4, Drynoch landslide, British Columbia; Geological p. 209-21 9. Su rvey of Canada, Paper 79-3 l, 34 p. Swan, D. van Ryswyk, A.L. 1978: Acoustic imaging of the seabed in northern 1969: Forest and alpine soils of south-central British Kitimat Arm, B.C.; unpublished B.Sc. thesis, Columbia; unpublished Ph.D. thesis, Washington Universi t y of Britis h Columbia, Department of State University, Pul lman, 178 p. Geophysics and Astronomy, Vancouver, 72 p. 197 1: Radiocarbon date for a c ryoturba ted alpine Swan, D. and Luternaue r, J .L. regosol in south central British Columbia; 1978: Mosaic of side scan sonar records, northern Canadian Journal of Soi l Science, v. 51, no . 3, Kitimat Arin, B.C.; Geological Survey of Canada, p. 5 13-515. Open file 579. van Ryswyk, A.L. and Okazaki, R. Swanston, D.N. 1979: Genesis and classification of modal suba lpine and 1969: A late-Pleistocene g lacial sequence from Prince alpine soil pedons of south-central P,r i t ish of Wales Isla nd, Alaska; Arctic, v. 22, no. l, Columbia, Canada; Arctic and A lpine Research, p. 25-33. v. J 1, no. 1, p. 53-67. Tallman, A.M . Wagner, W.P . 197 5: The glacial and periglacial geomorpho logy of the 1966: Correlation of Rocky .\i\ountain and Laurentide Fourth of July Creek valley, Atlin region, Cassiar glacia l chronologies in southwestern Alberta, District, northwestern British Columbia; Canada; unpublished Ph.D. thesis, University of unpublished Ph.D. thesis, Michigan State Michigan, Ann Arbor, 169 p. University, East Lansing, 178 p. Walker, M.J.C. Tauber, H. 1971 : Late-Wisconsin ice in t he 'v\orely F lats area of the 1970: The Scandinavian varve chronology and 1 'C Bow Valley a nd adjacent areas of the Kananaskis dating; in Radiocarbon Variations and Absolute Va ll ey, Alberta; unpublished 'vi.Sc. thesis, Chronology, ed. J. U. Olsson; Wiley lnterscience Un iversity of Calgary, Alberta, 11 4 p. Division, New York, New York, Almqvist a nd 1973: T he nature and origin of a series of elongated Wiksell, Stockholm, Sweden, p. 173-1 96 . ridges in the .\il orle y Flats area of the Bow Valley, Taylor, R.S. Al berta; Canadian Journal of Earth Scie nces, 1960: Some Pleistocene lakes of northern Alberta and v. JO, no. 8, p. 1340-1346. adjacent areas: revised; Alberta Society of Waters, R.R. Pe tro leum Geologists, Journal, v. 8, no. 6, 197 5: The glacia l geomorphology of the Pekisko C reek - p. 167-178, 185. Originally published (1958) !..!:. Happy Valley area, Alberta; unpublished M.Sc. Edmonton Geological Society Quarterly, v. 2, thesis, University of Calgary, Alberta. no. 4, p. 1-9. Westgate, J .A. Thorson, R.M. l 968: Surficial geology of the Foremost-Cypress Hi ll s 1979: Isostatic effects of t he last g laciation in the area, Alberta; Alberta Research Counc il, Puget Lowland, Washington; unpublished Ph.D. Bu lletin 22, 122 p. thesis, University of Washington, Seattle, 154 p. 1977: Identification and significance of late Holocene 1980: Ice-sheet glaciation of the Puget Lowland, tephra from Otter Creek, southern Brit ish Washington, during the Vashon Stade (l ate Columbia, and loca lities in west- centra l Alberta; Ple istocene); Quaternary Research, v. 13, no. 3, Canadian Journal of Earth Sciences, v. 14, no. 11, p. 303-321. p. 2593-2600. Tipper, H.W. Westgat e , J.A. and Dre imanis, A. 197 l a: Glacial geomorphology and P leistocene history of 1967: Volcanic ash layers of Recent age at Banff central British Columbia; Geologic a l Surve y of National Park, Alberta, Canada; Canadian Journal Canada, Bulletin 196, 89 p. of Earth Sciences, v. 4, no. 1, p. 155-162 . 197 lb: Multiple glacia tion in central British Colu mbia; Westgate, J .A. and Evans, M.E. Canadian Journal of Earth Sciences, v. 8, no. 7, 1978: Compositional variabili ty of Glacier Peak tephra p. 743-752. and its s tratigraphic significance; Canadian Trautman, M.A. and Walton, A. Journal of Earth Sciences, v. 15, no. 10, 1962: Isotopes, Inc . radiocarbon measurements II; p. 1554- 1567. R adiocarbon, v. 4, p. 35-4 2. Westgate, J .A. and Ful ton, R.J. Valentine, K.W .G . 197 5: Tephrostra t igraphy of Olympia Int erglacia l 197 1: Soils of the Tofino -Ucluelet lowland of British sediments in south-central British Columbia, Columbia; Canada Department of Agr iculture, Canada; Canadian Journal of Earth Scie nces, British Columbia Soil Survey, Report no. 11, 29 p. v. 12, no. 3, p. 489-502.

40 Westgate, J.A., Fritz, P., Matthews, J.V., Jr., Kalas, L., Wilson, J.T., Falconer, G., 'V\athews, W.H., and Delorme, L.D., Green, R., and Aario, R. Prest, V.K . (compilers) 1972: Geochronology and palaeoecology of mid- 1958: Glacial map of Canada; Geological Association of Wisconsin sediments in west-central Alberta, Canada, Toronto, Ontario. Canada [abstract); ~ Abstracts; Wuorinen, V. 24th International Geological Congress 1978: Age of Aiyansh volcano, British Columbia; (Montreal), p. 380. Canadian Journal of Earth Sciences, v. 15, no. 6, Westgate, J.A., Smith, D.G.W., and Tomlinson., M. p. 1037-1038. 1970: Late Qua ternary tephra layers in southwestern Yang, A.LC. . . Canada; in Early Man and Environments in 1971: Variations of natural radiocarbon during the last Northwest-North America, ed. R.A. Smith and l l millenia and geophysical mecha nisms for J.W. Smith; University of Calgary, Archaeological producing them; unpublished Ph.D. thesis, Association, Calgary, Alberta, p. 13-33. University of Washi r.gton, Seattle, 118 p. White, J.M., Mathewes, R.W., and :\ilathews, W.H. Yang, A.LC. and Fairhall, A.W. . . 1979: Radiocarbon dates from Boone Lake and their 1972: Variations of natural radiocarbon during t he last relation to the 'lee-free Corrido1·' in the Peace 11 m illenia and geophysical mechanisms for River District of Alberta, Canada; Canadian producing them; ~ Proceedings of the Eighth Journal of Earth Sciences, v. 16, no. 9, International Radiocarbon Dating Conference; p. 1870-1874. Royal Society of New Zealand, Lower Hutt, Wilcox, R.E. New Zealand, v. l, p. A44-A57. 1965: Volcanic-ash chronology; ~T h e Quaternary of the United States, ed. H.E. Wright, Jr. and D.G. Frey; Princeton University Press, Princeton, New Jersey, p. 807-816.

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