J. E. ARMSTRONG Geological Survey of Canada, Vancouver, B. C. DWIGHT R
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J. E. ARMSTRONG Geological Survey of Canada, Vancouver, B. C. DWIGHT R. CRANDELL U. S. Geological Survey, Denver, Colo. DONALD f. EASTERBROOK Western Washington State College, Bellingham, Wash. }. B. NOBLE Washington State Division of Water Resources, Olympia, Wash. Late Pleistocene Stratigraphy and Chronology in Southwestern British Columbia and Northwestern Washington Abstract: Six geologic-climate units are proposed B.P. but did not reach the southern end until after for the late Pleistocene sequence in southwestern 15,000 years B.P. The Vashon Stade of the Eraser British Columbia and northwestern Washington. Glaciation began with this advance of Cordilleran They include two major units, the Olympia Inter- ice into the lowlands. It ended with the beginning glacmtion and the Eraser Glaciation, and four sub- of marine and glaciomarine conditions there, which divisions of the latter—the Evans Creek, Vashon, commenced in the southern Puget Lowland about and Sumas Stades, and the Everson Interstade. The 13,500 years B.P. and in the Strait of Georgia about Olympia Interglaciation is a nonglacial episode that 13,000 years B.P. The episode represented by the started at least 36,000 years B.P. and continued marine conditions is called the Everson Interstade until the advance of Cordilleran glacier ice during and lasted about 2000 years, during which the sea the Eraser Glaciation. During the Evans Creek contained much floating ice. The Interstade ended Stade, alpine glaciers formed in the mountains of when the land rose with respect to the sea level western Washington and British Columbia while forcing withdrawal of the sea and the disappearance nonglacial sediments were still being deposited in of floating ice in most of northwestern Washington the southern Puget Lowland. Further growth of and southwestern British Columbia; in the eastern glaciers in British Columbia resulted in the forma- part of the Eraser Lowland this event coincided tion of the Cordilleran ice sheet. This ice entered with the advance of a valley glacier during the the northern end of the area after 25,000 years Sumas Stade. CONTENTS Introduction and acknowledgments 321 northwestern Washington showing extent Previous work 323 of glaciation 322 Olympia Interglaciation 324 2. Late Pleistocene geologic-climate subdivisions Fraser Glaciation 326 and stratigraphic units in southwestern General statement 326 British Columbia and northwestern Wash- Evans Creek Stade 326 ington 324 Vashon Stade 327 Everson Interstade 327 Sumas Stade 329 Table References cited 329 1. Composite stratigraphic section of deposits in- cluded in Everson Interstade in eastern Figure half of Fraser Lowland, British Columbia 328 1. Map of southwestern British Columbia and new geologic-climate units for the late Pleisto- INTRODUCTION AND cene in northwestern Washington and south- ACKNOWLEDGMENTS western British Columbia (Fig. 1). A new Stratigraphic studies between 1950 and 1963, formal name is proposed for the last major supplemented by more than 130 radiocarbon glaciation during which glaciers occupied the dates, have shown a need for defining several mountains and lowlands of this area. In the past Geological Society of America Bulletin, v. 76, p. 321-330, 2 figs., March 1965 321 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/76/3/321/3427673/i0016-7606-76-3-321.pdf by guest on 01 October 2021 322 ARMSTRONG AND OTHERS—LATE PLEISTOCENE STRATIGRAPHY Maximum extent of Cordil- lera glacier in Washington during Vasnon Stade, Figure 1. Map of southwestern British Columbia and northwestern Washington showing extent of elaciation many writers have used the name Vashon below Vashon Drift in the southern Puget Glaciation to refer to this event. We now Lowland and southwestern British Columbia. propose to restrict the use of the name Vashon The Pleistocene sedimentation of this region to a stade. Two other stades and one interstade is one of alternate glacial and nonglacial deposi- within the last major glaciation are also named. tion. During each major glacial episode a Finally, a formal name is introduced for a non- Cordilleran glacier, originating in the moun- glacial interval represented by deposits directly tains of British Columbia, largely on the main- Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/76/3/321/3427673/i0016-7606-76-3-321.pdf by guest on 01 October 2021 INTRODUCTION AND ACKNOWLEDGMENTS 323 land but partly on Vancouver Island, advanced the Washington State Division of Water Re- southward and southwestward into the Strait sources; Edmund Livingston and }. C. Fower- of Georgia, the Fraser Lowland, and the Puget aker of the British Columbia Water Investiga- Lowland. At its maximum the last Cordilleran tions B ranch; and S. C. Porter of the University ice sheet covered the Strait of Georgia and the of Washington. mountains of Vancouver Island. Southward the ice formed the Puget lobe which extended from PREVIOUS WORK the vicinity of Port Townsend to a point 15 The first recorded subdivision of the Pleisto- miles south of Olympia (Fig. 1) and terminated cene in southwestern British Columbia was laterally against the Olympic Mountains and made by Dawson (1887). He noted two tills the Cascade Range. In these mountains alpine separated by stratified sands and silts, but he glaciers were formed during an early stade of did not apply stratigraphic names to the de- the last major glaciation. These alpine glaciers posits. The earliest published subdivision of reached their maximum stands before the the Pleistocene of western Washington was advance of the Puget lobe and were in retreat presented by Willis (1898), who also recognized when the lobe reached the southern Puget two glaciations, Admiralty (older) and Vashon, Lowland. During a late stade of the last major separated by a nonglacial interval which he glaciation, after the Cordilleran glacier had re- named Puyallup. This sequence was subse- treated into the Coast Mountains of British quently adopted with only minor modifica- Columbia, a valley glacier advanced at least 40 tions by most other workers in western Wash- miles into the Fraser Lowland. ington and southwestern British Columbia All the radiocarbon dates referred to in this (Bretz, 1913; Clapp, 1913; 1914; 1917; Bur- paper except where noted are published in wash, 1918; Johnston, 1923; Hansen and Radiocarbon—volumes 1, 3, 4, 5, and 6. Mackin, 1949; Sceva, 1957). In the preparation of this paper the authors A more complex sequence of geologic- made the following contributions: Armstrong climate units was subsequently established in acted as over-all co-ordinator, and he is re- the region. Mackin (Hansen and Mackin, 1949; sponsible for the British Columbia portions of Mackin and others, 1950) recognized three the geology, and for the definition of the glaciations separated by nonglacial intervals. Fraser Glaciation and Sumas Stade; Crandell Crandell and others (1958) established a is responsible for the definition of the Vashon sequence of four glaciations separated by non- and Evans Creek Stades and, along with Noble, glacial intervals, as follows: for the geology of the southern Puget Lowland Vashon Glaciation and definition of Olympia Interglaciation; Unnamed nonglacial interval Easterbrook is responsible for the definition of Salmon Springs Glaciation the Everson Interstade and for the geology of Puyallup Interglaciation the Fraser Lowland and northern Puget Low- Stuck Glaciation land in Washington. In addition to the authors' Alderton Interglaciation investigations recent field work by others has Orting Glaciation. contributed to the information contained Crandell and others found that deposits on herein, namely: J. G. Fyles and E. C. Halstead which Willis based his Admiralty Glaciation of the Geological Survey of Canada; D. R. are of different age from place to place, thus the Mullineaux, H. H. Waldron, and K. L. Walters name was not used in their sequence. of the U. S. Geological Survey; Dee Molenaar Likewise, detailed studies in the Fraser of Washington State Division of Water Re- Lowland of British Columbia by Armstrong sources; and W. L. Brown, consulting hydro- (Armstrong and Brown, 1953; 1954; Arm- geologist, Vancouver. All these workers have strong, 1956a; 1956b; 1957; 1960a; 1960b; read the paper and are in general agreement unpub. inf.) and on Vancouver Island (Fyles with the names and usages proposed; however, 1960a; 1960b; 1963; Halstead, 1963) led to the authors assume full responsibility for the the discovery of a far more complex succession definitions of the proposed geologic-climate of climatic events than had been formerly units. The following workers have also read the recognized (Fig. 2). Armstrong established the paper and concur with the above: S. F. Learning following stratigraphic sequence in the Fraser of the Geological Survey of Canada; H. W. Lowland : Anderson, A. A. Garrett, and J. E. Luzier of Sumas Drift the U. S. Geological Survey; R. H. Russell of Capilano sediments Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/76/3/321/3427673/i0016-7606-76-3-321.pdf by guest on 01 October 2021 324 ARMSTRONG AND OTHERS—LATE PLEISTOCENE STRATIGRAPHY Surrey Drift Quadra sediments Quadra sediments Dash wood Drift Semiamu Drift Mapleguard sediments. Nonglacial sediments The present paper is concerned with the last At least two older unnamed drifts sepa- major glaciation, which has heretofore been rated by nonglacial sediments occur in referred to as Vashon, and with the nonglacial the lower part of the sequence. interval preceding the Vashon. FRASER LOWLAND SOUTHERN ABSOLUTE EAST COASTAL LOWLANDS PUGET GEOLOGIC-CLIMATE TIME BRITISH WASHINGTON UNITS THOUSANDS COLUMBIA VANCOUVER LOWLAND ISLAND Grand ell (1963) of YEARS Armstrong (1956 et sw Easterbrook(1963: Molenaar&Garling B.R and unpublished ms.) Fyles (1963) (1963 1— ""- .. 10 — ^\ Drifl ^-> Or if! "-> STADE-.^1" ^- ' ^"' 11 — srtimen'ts What com Bellmgham EVERSON deposits Ca |(ano d'ifl 12 — INTER STADE Newton sediments Demmg Z stony clay O 13 — Clover dale Kulshan sediments glacioma.ine h- ~~~~~~~~~— u 14 — — - ———. <c VASHON Vashon Drift ^^__ o STADE j Surrey Drift Vashon Drift Vashon Drift / 15 — --^" / / 17 ~ 0.