DON J. EASTERBROOK Department of Geology, Western State College, Bellingfiam, Washington 98225

Pleistocene Chronology of the Puget

Lowland and San Juan Islands, Washington

ABSTRACT The Puget Lowland and San Juan Islands, lying tion of Russia, the Paudorf Interval of and in the Puget Trough between the the Farmdalian of the midwestern . and the Olympic Mountains, were in the path of Esperance Sand, deposited by meltwater streams ice sheets which flowed southward in front of advancing ice during the Fraser Glacia- from . tion and subsequently overridden during the Floodplain, silt, sand, and peat of the Whidbey Vashon Stade, was radiocarbon dated at 18,000 + Formation were deposited prior to 40,000 years 400 years. During deglaciation, the ago, during an interglaciation believed to be thinned until it floated in marine water and poorly equivalent to the Puyallup and Sangamon Inter- sorted, fossiliferous glaciomarine drift was de- glaciations. Possession Drift, which overlies sedi- posited in the Everson Interstade. Shell-bearing ments of the Whidbey Formation, is radiocarbon sediment at altitudes up to 400 feet above present sea level and unfossiliferous glaciomarine drift up dated at 34,000 j^OOO years B'P' in "S Upper to 600 feet indicate that relative sea level at that part and is limited by a radiocarbon age of > 39,900 time was 500 to 700 feet higher. Eighteen radio- in its lower part. The Possession is correlated with carbon dates from marine shells in Everson glacio- late phases of the Zyriansk Glaciation in Russia marine drift vary from 10,370 ± 300 to 13,010 ± and the early Wiirm in Europe. 170 years. The Everson Interstade ended with Peat lying on Possession Drift yielded radio- lowering of relative sea level to approximately its present position and the disappearance of floating carbon dates between 27,200 + ^ and 22,700 ± ice. The following Sumas Stade ended shortly 550, representing the Olympia Interglaciation before 9,920 + 760 years ago. which is correlated with the Karginsk Interglacia-

INTRODUCTION A large part of the region is directly under- lain by Pleistocene unconsolidated deposits. The Puget Lowland and San Juan Islands This paper deals with radioisotope chronology lie in the Puget Trough between the Cascade and correlation of Pleistocene deposits between Range on the east and the Olympic Mountains Seattle and the Canadian boundary. and Vancouver Island on the west (Fig. 1). Lying directly in the path of Pleistocene ice The Lowland is an elongate structural trough, lobes which extended southward from British modified by Pleistocene deposition and erosion, Columbia, the Puget Lowland and the San lying mainly between sea level and 500 feet. Juan Islands were glaciated several times. Ex- Marine water enters the region through the cellent sea cliff exposures along the many miles Strait of Juan de Fuca and extends about 100 of shoreline provide abundant evidence of the miles southward in Puget Sound and Hood Pleistocene stratigraphy of the region, and Canal. The San Juan Islands are part of a radiocarbon dating of peat, wood, and marine structural arch which transects the structural shells in many of the deposits allows firm estab- depression of the Puget Lowland and brings lishment of absolute chro- to the surface Paleozoic and Mesozoic sedimen- nology. tary rocks and pre-Devonian crystalline rocks. Study of glacial deposits in the Puget Low- Much of the larger islands and parts of the land and San Juan Islands was supported by other islands are composed of these rocks, research grants from the National Science thinly mantled with glacial sediments. Thicker Foundation as part of an investigation of glacial and more extensive Pleistocene deposits are problems in northwest Washington. The field found at low elevations on many of the islands. seasons of 1960-62 were spent in the lowland

Geological Society of America Bulletin, v. 80, p. 2273-2286, 2 figs., 2 pis., November 1969 2273 2274 D. J. EASTERBROOK—PLEISTOCENE CHRONOLOGY, WASHINGTON

Maximum extent of in Fraser Lowland during Sumas Stade

Maximum extent of Cordil- leran glacier in Washington during Vashon Stade

Boundary of physiographic subdivision

Figure 1. Index map of the Puget Lowland and San Juan Islands. Region discussed in this paper is outlined with a heavy black line.

between the Canadian border and Bellingham, DOUBLE BLUFF DRIFT the seasons of 1963-65 on Whidbey and Camano Islands, and parts of the summers of The oldest glacial deposits recognized in the 1964-66 in the San Juan Islands. The 1966-67 Puget Lowland between Seattle and British field seasons were spent studying deglaciation Columbia belong to the Double Bluff Drift near the Canadian boundary and alpine glacia- (Easterbrook and others, 1967; Easterbrook, tion in the Cascade Range adjacent to the 1968), which consists of , glaciomarine drift, lowland. Unless otherwise indicated, radio- gravel and sand. The Double Bluff Drift is carbon dates were made by Isotopes Inc. of exposed in several bluffs near sea level on from samples collected by the Whidbey and Camano Islands and on the writer. northwest corner of the Olympic Peninsula at For a discussion of previous investigations of Point Wilson. Pleistocene geology in the Puget Lowland, the There is little or no weathering of pebbles reader is referred to Armstrong and others in the drift, and no soils or weathering profiles (1965), Easterbrook and others (1967), and have been found at the top of the unit. In view Easterbrook (1968). Table 1 shows the se- of the lack of weathering, Easterbrook and quence of climatic events now recognized and others (1967), concluded that the drift on a suggested correlation with radiocarbon-dated Whidbey Island was not of great antiquity, sediments in the northern and central Puget but they were uncertain as to whether it Lowland and San Juan Islands. correlated with the Stuck Drift or one of the WHIDBEY FORMATION 2275 two units belonging to the Salmon Springs estimated. The upper surface of the Whidbey Drift of the southern Puget Lowland (Crandell Formation is typically somewhat irregular, and others, 1958). It now seems unlikely that varying from about 35 feet above sea level to the Double Bluff Drift correlates with the below sea level. In some places, beds are trun- Salmon Springs Drift, but a definite correlation cated by the overlying units, but how much with the Stuck Drift remains to be demon- of the Whidbey has thus been cut out by strated. erosion is difficult to estimate. Farther south, No deposits of the Double Bluff or older the Whidbey is, in places, as much as 250 feet glacial intervals have been recognized in the thick, suggesting that a significant portion of San Juan Islands, although the ice of each the Whidbey in the San Juan Islands has been glacial episode recognized farther south must removed by erosion. have passed over the islands. What may be the At its type locality and at many other sea oldest glacial drift in the islands is a strongly cliff exposures, the Whidbey Formation lies indurated till which occurs on the south shore upon Double Bluff Drift and is overlain by of Cypress Island and on Allan and Burrows Esperance sand. In a few places, however, Islands (Fig. 2). Possession Drift lies between the Whidbey and Esperance. WHIDBEY FORMATION The sediments of the Whidbey Formation The Whidbey Formation is named from suggest a floodplain environment (Hansen and deposits at Double Bluff on Whidbey Island, Mackin, 1949; Easterbrook and others, 1967). where it is represented by sand, silt, clay, and The silt and sand was deposited on extensive peat totaling several hundred feet in thickness flood plains and deltas. Peat beds interbedded (Easterbrook and others, 1967). Outcrops of with fine-grained sediment represent organic the Whidbey are widespread on Whidbey and material deposited in swampy areas on the Camano Islands and on the northwest corner flood plains. of the Olympic Peninsula near Point Wilson. The best exposures of the Whidbey Forma- Age and Correlation tion in the San Juans occur in sea cliffs along Twelve radiocarbon age determinations have the west shore of Guemes Island (Fig. 2) where been obtained from samples of peat and wood about 35 feet of interbedded silt, sand, and in the Whidbey Formation, but all were beyond peat is exposed above sea level (PL 1, fig. 1). the limits of conventional C14 dating. The ages The base of the Whidbey is not exposed above are listed in Table 2 and the sample localities sea level so the true thickness there cannot be are shown on Figure 2. Although correlation of the Whidbey with See Plate Section for all plates. stratigraphic units in the southern part of the TABLE 1. PLEISTOCENE SEQUENCE IN THE NORTHERN AND CENTRAL PUGET LOWLAND AND SAN JUAN ISLANDS, WASHINGTON

GEOLOGIC CLIMATE UNITS STRATIGRAPHIC UNITS C14 AGE* Sumas Stade Sumas Drift -10,000 -11,000 Everson Interstade Everson Glaciomanne Drift FRASER GLACIATION -13,030 Vashon till Vashon Stade Esperance Sand -18,000 -23,000 OLYMPIA INTERGLACIATION Quadra Sediments -27,000 -35,000 SALMON SPRINGS GLACIATION Possession Drift -40,000 PUYALLUP INTERGLACIATION Whidbey Formation ? STUCK (?) GLACIATION Double Bluff Drift * Because most of the units are time-transgressive the ages shown are approximate. 2276 D. J. EASTERBROOK—PLEISTOCENE CHRONOLOGY, WASHINGTON

Puget Lowland is not at present clearly de- Seattle. On the basis of the nature of the sedi- fined, some tentative conclusions may be ments, their thickness, and their distribution, reached. The nature and distribution of Whid- it is apparent that the Whidbey represents a bey sediments indicate that they once formed significant interval during which glacial ice part of an extensive floodplain that covered was absent from the lowland. Pollen analyses the major part of the Puget Lowland north of from peat in the Whidbey suggest no appre-

, • s^**,^,.-^ ^ \"*?r - la gKri ^asfest^ v* ,. San Juan Ufettf ~ "*> «^:JM ^E^ S^F Ite

•^.M^im^^:'.':^"'... ^,%^LU-j [¥A. ---,.- . !fc? -H^Ulte^-.-- •-!'-

Figure 2. Map showing location of C14-dated samples in the Puget Lowland and San Juan Islands, Washington. POSSESSION DRIFT 2277 ciable difference from the climate of the present Outcrops of the drift are discontinuous and (Easterbrook and others, 1967). relatively rare; there are less than ten localities Of the two most probable correlations sug- where it has been positively identified. On gested by Easterbrook and others (1967), Whidbey Island and on the Olympic Peninsula namely correlation with the Puyallup Inter- near Point Wilson, it lies on the Whidbey glaciation or with a nonglacial episode within Formation and is overlain in most places by the Salmon Springs Glaciation, the former is Esperance sand or Vashon till, or both. Posses- believed by the author to be the most likely. sion Drift has been identified in the San Juan The reasons for this belief are (1) the extensive Islands only at Yellow Bluff on Guemes Island floodplains of the Whidbey Formation should where gravel deposits overlying the Whidbey have had counterparts farther south in the Formation are tentatively correlated with the lowland, (2) the Puyallup Formation includes Possession. floodplain sediments very similar to the Whid- bey, (3) the Whidbey appears to represent a Age and Correlation major episode, perhaps equivalent The Possession Drift has been tentatively to the Sangamon, and the Puyallup has been correlated with the Salmon Springs Glaciation similarly interpreted, (4) both are beyond the of the southern Puget Lowland; however, range of conventional radiocarbon dating, and Salmon Springs Drift at its type locality con- (5) both occupy similar stratigraphic positions sists of two glacial units separated by peat and with respect to younger and older units. No volcanic ash, whereas the Possession Drift is single line of evidence outlined above clearly composed of a single glacial deposit. Radio- demonstrates correlation of the Whidbey with carbon dates from the peat between the two the Puyallup, but taking the evidence in total drift units near Salmon Springs are listed with the absence of any negative evidence, below (Easterbrook and others, 1967): this correlation is considered very probable. >38,000 years B.P. The possibility that the Whidbey corre- >51,000 years B.P. (after pretreatment) sponds to a thin non-glacial deposit between >49,000 years B.P. (alkali extract) two drifts of the Salmon Springs Glaciation 50,100 + 400 years B.P. (enriched) east of Tacoma is thought to be less likely The last three dates listed were from J. C. because only at one locality are non-glacial Vogel in Groningen who indicated that the sediments known to lie between the two units. 50,000 + 400 date should be considered tenta- Pollen from peat at that locality suggests a tive. cool moist climate which might represent either Wood from Possession Drift at east Useless a relatively minor glacial recession between Bay was radiocarbon dated as older than deposition of the two or only a portion of 40,000 years. The drift from which the wood a longer non-glacial phase. Pollen analysis of was obtained lies upon peat-bearing sand of the the nonglacial unit between the two Salmon Whidbey Formation, and there is some possi- Springs drifts could not prove that it does not bility that the wood in the drift was reworked correlate with part of the Whidbey because from peat in the Whidbey. However, there similar cool moist climatic conditions might was no peat associated with the wood found be expected shortly after the glaciation that in the drift. preceded the Whidbey and just prior to the At Strawberry Point on Whidbey Island glaciation which followed the Whidbey. Al- (Fig. 2) several peat units overlie and are though the pollen results are not conclusive, interbedded with Possession Drift (PI. 2). That there is no evidence of any substantial inter- the drift there is Possession is indicated by its glacial interval within the Salmon Springs stratigraphic position between the Whidbey Drift. Formation, which is exposed at low tide, and POSSESSION DRIFT the overlying Esperance Sand and Vashon till. Possession Drift is named from deposits of Within the drift unit are till and two peat units till at Possession Point on Whidbey Island 4 to 8 inches thick interbedded with outwash (Easterbrook and others, 1967). At its type gravel. locality and at most other outcrops, Possession The peats represent local swamps, later Drift consists of compact till, but, in a few covered by outwash deposits. The upper peat places, it is a pebbly clay containing scattered in the gravel was radiocarbon dated as 34,900 marine shells and shell fragments. The till ears B P and the lower reaches a maximum thickness of 80 to 100 feet Y - - near the middle of Whidbey Island. peat > 39,900 years B.P. (PL 2, fig. 1). The TABLE 2. SUMMARY OF RADIOCARBON DATES

Age Sample (Yrs. B.P.) No. Sample Name Mat'l Locality Whidbey Formation >35,000 -1194 Polnell Pt., Whidbey Is. Wood in Peat 48°17' N, 122°32' W >35,400 -1385 Pt. Roberts Wood in Peat 48°59^' N, 123°01K' W >35,000 -1445 Swantown, Whidbey Is. Wood in Peat 48017^'N, 122°43H'N >33,200 -1446 Penn Cove, Whidbey Is. Peat 48°14' N, 122°43' W >42,000 -722 North of West Beach Wood 48°15^'N, 122°45' W >35,700 -1528 Elger Bay, Whidbey Is. Peat 48°7^' N, 122°27J^' W >42,000 -723 Crescent Beach, Orcas Is. Wood 48°40K' N, 122°53' W > 40,000 -974 Guemes Is. Wood in Peat 48°32^' N, 122°39' W >40,000 -975 Everett Gorge Peat 47°58'N, 122°13' W >39,900 -2283 Freeland, Whidbey Is. Wood in Peat 48°05' N, 122°37' W >40,000* W-1516 Indian Pt., Whidbey Is. Peat 47°55' N, 122°29' W >40,000* W-1523 Double Bluff, Whidbey Is. Peat 47°58'N, 122°32'W Possession Drift >40,000 1-1203 Useless Bay, Whidbey Is. Wood 47°58' N, 122°27' W >39,900 1-2284 Strawberry Pt., Whidbey Is. Peat 48°18' N, 122°30' W 3 00 33

TABLE 3. PLEISTOCENE CORRELATIONS

PUGET LOWLAND RUSSIA MIDCONTINENTAL EUROPEAN and () U.S. ALPS SAN JUAN ISLANDS (Kind, 1965) (Frye, Willman, (Mayr and (This paper) Black (1965) Heuberger, 1968) 9,000- Daun Cold Valderan Gschnitz ^ Sumas Stade Steinach Moderately O Everson Interstade Two Creekan Allerod Interval 12,000- warm *< 13,000- ^ Vashon SARTAN Cold 14,000- Woodfordian MAIN (Late) ^ Stade 15,000- rt 16,000- ina GLACIATION < WURM « fc 18,000-

20,000-

22,000- OLYMPIA KARGINSK 24,000 - INTERGLACIA- FARMDALIAN TION INTERGLACIATION 26,000- STAG E 28,000- p

30,000- ALTONIAN PAUDORF DRIFT OF 32,000 - POSSESSION WISCONSINA N INTERVAL AGE 34,000- (SALMON SPRINGS) ZYRIANSK EARLY 36,000- WURM GLACIATION 38,000-

>40,000- i SEDIMENTS OF ^ WHIDBEY AGE r J) (PUYALLUP) 2282 D. J. EASTERBROOK—PLEISTOCENE CHRONOLOGY, WASHINGTON is uncertain. Perhaps the most likely possibility water. Theories for the origin of these troughs is reworking of the glacier's own advance out- have centered around (1) glacial erosion, (2) wash. deposition of sediments between lobes of ice Vashon till lies unconformably on a wide occupying preglacial stream valleys and subse- variety of older units ranging in age from quent withdrawal of the ice (Willis, 1898), and Esperance Sand to pre-Devonian bedrock. Al- (3) pre-Vashon fluvial erosion into an older though in places the contact with the Esperance fill after regional uplift (Bretz, 1913). Crandell Sand appears to be conformable, in many sea and others (1965) presented evidence that the cliffs the till cuts across the sand. trough between Seattle and the Kitsap Pen- insula truncates Esperance Sand and deposits Ice Thickness of the Olympia Interglaciation in such a The summit of Mt. Constitution (2409 ft) on way as to indicate that the erosion was ac- Orcas Island was topped by Vashon ice, but complished by the Vashon glacier. Evidence since there are no higher elevations in the from the San Juan Islands, Whidbey Island, islands, the best evidence for ice thickness Camano Island, Kitsap Peninsula, and the comes from the altitude of Canadian erratics in mainland of the northern and central Puget the Cascade Range just to the east. Granitic Lowland point to a similar conclusion. erratics of Canadian origin are found at alti- As ice originating in British Columbia flowed tudes up to 5300 feet and local erratics as high southward across the International Boundary, as 5700 feet occur near Mt. Baker. Although meltwater streams spread Esperance outwash all of these erratics may not be Vashon, the sand and gravel southward in front of the evidence available strongly suggests that the glacier. That the Vashon glacier over-rode its altitude of the surface of Vashon ice at this own outwash is shown by Vashon till resting latitude was about 5500 to 6000 feet. on top of Esperance Sand, but the extent of the former is difficult to establish Direction of Movement since the original constructional surface has The numerous grooves and striations which been greatly modified by glacial erosion in occur on bedrock outcrops in the San Juan most places. Islands provide abundant evidence for local The irregular lower contact of the Esperance directions of ice flow. McLellan (1927) found indicates that the pre-Vashon topography con- that sisted of hills of older Pleistocene deposits The direction followed by the upper portions of the which were first surrounded by outwash and, glacial ice in this region was not controlled by the under- in many cases, completely buried. The thick- lying topography. The courses of the deepest glacial ness of Esperance sand and gravel varies from erosion were partly determined by the presence of fault zero to more than 250 feet, partly because of or fracture zones or by previously existing valleys or the irregularity of the lower surface and partly channels. Near sea-level the glacial striations usually because of subsequent glacial erosion. Deposits follow parallel to the courses of the present water chan- of Esperance Sand are widespread in the Puget nels, while at higher elevations the striations trend nearly Lowland, but this in itself does not necessarily north and south, (p. 138-39). prove that all of the deposits belong to a con- There is a good deal of diversity in the direc- temporaneous and once continuous outwash tion of striations and grooves on bedrock in the plain. The same distribution might be observed San Juans. Striations on rock at the summit of if the Vashon glacier transgressively overrode Mt. Constitution trend approximately north- its own outwash soon after the outwash was south but, at lower elevations on Orcas, stria- deposited. In fact, the outwash in the northern tions are oriented about N. 20 W. to N. 40 W. part of the lowland probably was overridden Although McLellan thought that there was no and buried with till before any outwash was indication of a westerly trend of flow toward deposited in the southern part of the lowland. the Strait of Juan de Fuca, at the southern tip Nor does widespread occurrence of Esperance of San Juan Island deep glacial grooves that Sand disprove the concept that the upper parts trend between N. 23 E. and N. 30 E. are of the troughs are "molds" of former ice interpreted to represent the beginning of a tongues against which Esperance Sand was westerly component of flow toward the strait. deposited. However, of critical importance is the absence of slump structures and various ice Origin of Troughs in the Puget Lowland contact features in the Esperance deposits ex- Much of the Puget Lowland is characterized posed in sea cliffs at the margin of the troughs by a series of elongate troughs filled with sea which should be present if the sediments had DEPOSITS OF THE FRASER GLACIATION 2283 been banked against ice occupying the position time. The glaciomarine deposits vary in thick- of the present troughs. It thus appears that ness from a foot to about 25 feet. although transgressive, the outwash plain in The highest altitudes of positively identified, front of the advancing glacier was at least fossiliferous Everson glaciomarine drift found moderately continuous in an east-west direction by the writer in the San Juan Islands were about roughly parallel to the ice front. In many sea 125 feet above sea level. A deposit near the cliff exposures, Vashon till cuts down across southeast tip of Orcas at 250 feet contains some Esperance outwash and older Pleistocene sedi- shell fragments and is thought to be glacio- ments, and disappears below sea level. The marine drift. Other fossil localities are less than conclusion drawn from the above evidence is 50 feet above sea level and although there are that Vashon ice deeply eroded its own advance many outcrops of Everson glaciomarine drift outwash and scoured the troughs prior to which do not contain fossils, their altitudes are deposition of Vashon till. This interpretation similar to those of the fossiliferous deposits. implies that the Vashon glacier eroded deeply Bretz (1913) noted several higher shell localities in its most vigorous phase and deposited till on Orcas Island, the highest being in a well dug in a later phase. in shell-bearing clay at an altitude of 290 feet and in a ditch through a marsh where many Correlations clam shells in clay and peat were found at an altitude of 270 feet. These occurrences could The Vashon Stade was correlated with the not be relocated, but since Everson glacio- Tazewell maximum of the Glaciation marine deposits are found at elevations of 400 by Crandell and others (1958), with the "classi- feet and higher on the mainland 10 to 15 miles cal" Wisconsin by Armstrong and others (1965), to the east of the San Juan Islands, (Easter- and with the Woodfordian substage of the brook, 1963) the altitudes of the Orcas localities Wisconsin by Easterbrook (1966). The Vashon are well within the probable relative sea levels may now also be correlated with the early part 14 during the Everson Interstade. of the Sartan Glaciation in Russia where C Marine fossils are abundant in the glacio- dates ranging from 12,940 ± 400 to 21,700 + marine drift at a number of localities, occurring 1700 match well with the age of the Vashon in greatest numbers at localities on San Juan, (Kind, 1965). In Western Europe the Vashon Orcas, Sucia, Whidbey and Hope Islands (Fig. corresponds to the late (Main) Wiirm and late 2). The fossils found in the San Juan Islands arc Weichselian pleniglacial. listed in Table 4. The most abundant forms are various species of Chlamys, Hiatella (Saxicava), Everson Glaciomarine Drift Macoma, and Saxidomus. Checklists of marine The Everson Interstade began with the in- fauna in the northern Puget Lowland are vasion of the lowlands by the sea during the given in Easterbrook (1963). retreat of the Vashon glacier and ended with The distribution and altitude of Everson the withdrawal of the sea from most of the glaciomarine drift and the absence of subaerial area and the disappearance of floating ice. The recessional outwash in most places indicate that interval is represented by glaciomarine drift, a following the maximum stand of ice during the poorly sorted, till-like deposit of pebbly silt Vashon Stade, downwasting during recession and clay (PI. 1, fig. 2) which was deposited in resulted in sufficient thinning to allow the ice marine water when relative sea level was higher to float in the relatively higher sea level which than at present and melting of floating berg existed in the San Juan Islands and adjacent and shelf ice released debris on the sea floor. mainland about 12,500 years ago. During the Shells of molluscs living on the sea floor at the Everson Interstade, floating shelf and berg ice time were buried in the sediment, so many of deposited glaciomarine drift over those portions the deposits are fossiliferous. The lithology of of the islands and lowland presently less than pebbles and cobbles in the drift indicate that about 400 feet above sea level. Deposition of the material was derived largely from Canadian Everson glaciomarine drift ended with drop of sources. relative sea level to approximately that of the Glaciomarine drift mantles the topography present and disappearance of floating ice about at lower elevations in the San Juan Islands and 10,000 to 11,000 years ago. adjacent lowlands but is discontinuous, largely Age and Correlation. Eighteen radiocarbon as a result of removal by erosion. On many of dates of marine shells and wood in Everson the islands it is absent at higher elevations glaciomarine drift have been obtained by the because the area was above sea level at that author during the present study (Table 2). 2284 D. J. EASTERBROOK—PLEISTOCENE CHRONOLOGY, WASHINGTON

TABLE 4. CHECKLIST OF FOSSILS IN EVERSON GLACIOMARINE DRIFT, SAN JUAN ISLANDS AND VICINITY, WASHINGTON

Locality Numbers 1211 1212 1213 1214 1215 1216 1218 1219 1224 1226 Nuculana fossa (Baird) X Nuculana sf. X Hiatella (Saxicava) arctica (Linne) X X X X X Saxidomus nutalli far. giganteus (Deshayes) X X X Cardium ciliatum (Fabricius) X X X X X Cardium corbis (Martyri) X X Cardium sp. X X X X X Chlamys hcricius (Gould) X X X X C. Hindsii (Carpenter) X X X X C. Jordani (Arnold) X Protothaca staminea (Conrad) sf. X X X X Macoma sp. X X X X XX X Serpula vermicularis (Linne) X X X X X Balanus tintinnabulum californicus (Pilsbry) X X X XX X Mytilus sp. X X X X Mya X X X X Spisula sp. X Acmaea sp. X

The dates of the samples range from 10,370 ± Sumas Stade (Armstrong and others, 1965). In 300 (1-1035) to 13,010 + 170 (UW-32). the Fraser Lowland of B ritish Columbia, Sumas The Everson Interstade has been correlated till rests directly upon Everson glaciomarine with the Two Creeks interval of the Great drift, and an outwash terrace slopes southward Lakes region in the U.S. (Easterbrook, 1966). across the international boundary from a ridge In western Europe it correlates with the of ice-contact deposits. The terrace is inter- Allerpd Interval and in Russia with a moder- rupted by the modern floodplain of the Nook- ately warm, late phase of the Sartan Glaciation sack River but continues south of the river for (Table 3) from which radiocarbon dates of several more miles before terminating against 11,450 and 11,700 years have been obtained hills of Everson glaciomarine drift. (Kind, 1965). The principal significance of the outwash sediments is that they were deposited sub- Sumas Drift aerially at about their present altitude after the Sumas Drift consists of till, outwash, and marine submergence of the Everson Interstade ice-contact sediments deposited during the and thus demonstrate that the post-Everson TABLE 5. FOSSIL LOCALITIES IN EVERSON GLACIOMARINE DRIFT, SAN JUAN ISLANDS AND VICINITY, WASHINGTON

Locality Number Description W-1211 Davidson Head, San Juan Island, NEJ4NWM sec. 13, T. 13 N., R. 4 W., Roche Harbor quadrangle W-1212 Cattle Point, San Juan Island, east end of bay about 1 mile west of Mt. Finlayson, SE. tip of San Juan Island, Richardson quadrangle W-1213 Cattle Point, San Juan Island, adjacent to W-1212 W-1214 One mile west of Cattle Point, San Juan Island, SWJ4SEJ4 sec. 7, T. 34 N., R. 2 W. W-1215 Drainage ditch in field 2 miles SW. of East Sound, SWMSEJ4 sec. 22, T. 37 N., R. 2 W. W-1216 SW. end of West Beach, Northwest shore of Orcas Island, SEJ4NEJ4 sec. 20, T. 37 N., R. 2 W. W-1218 Reservoir at Four Winds Camp, NEJiNEJ^ sec. 18, T. 36 N., R. 2 W. W-1219 Road cut % mile north of Olga, SEJ4NEJ4 sec. 8, T. 36 N., R. 1 W. W-1224 West tip of Little Sucia Island, NEKSEJ4 sec. 27, T. 38 N., R. 2 W. W-1226 North shore of Hope Island REFERENCES CITED 2285 emergence took place in a short period of time Further evidence of the Sumas stade occurs in the late Pleistocene rather than over a long east of the lowland in Columbia Valley, an post-gkcial interval. abandoned outwash channel more than 10 A number of lakes and peat bogs occur in miles long and up to 2 miles wide, containing abandoned meltwater channels and kettles on a thick fill of outwash sand and gravel. About the outwash terrace. Several of the bogs were 3 miles north of the U.S.-Canadian boundary, cored with a Hiller corer and three radiocarbon the valley floor drops abruptly more than 400 dates were obtained from peat cores. A C14 date feet. The floor of Columbia Valley slopes south- of 9,920 + 760 (1-2280) from the base of the ward from this large depression and is charac- bog at Pang born Lake at a depth of 19 feet terized by abandoned channels and some below the surface provides an upper-age limit kettles. Clearly, the thick outwash deposits in for the end of deposition of the underlying out- the valley were banked against the margin of wash. A single ash layer, 1 to 2 inches thick, glacial ice and when the ice melted the outwash was found in the core at a depth of 13.8 feet. sediments and valley floor were left high above A radiocarbon date of 7,140 + 600 years was the mold left by the ice in the upper part of obtained from peat just beneath the ash layer the valley. As indicated by the difference in and, although petrographic analysis of the ash elevation between the top of the outwash train remains to be done, the nearness to the 6700 and the bottom of the formerly ice-filled year age generally accepted for Mazama ash valley, the ice must have been at least 500 to from Crater Lake, Oregon, suggests that the 600 feet thick. ash is probably Mazama. A Cu age of 9,300 ± Correlations, The Sumas Stade has been 250 (1-2281) from the base of a peat bog at correlated with the Valders of the midwestern Fazon Lake in an abandoned outwash channel U.S. and with the Late Pinedale of the Rocky several miles to the south provides an addi- Mountains (Easterbrook, 1966). In the Euro- tional limiting date for the cessation of outwash pean Alps the Sumas Stade corresponds to the deposition. The occurrence of ash at similar interval between the Aller0d and post-glacial depths in many other bogs in the vicinity period, characterized by the Steinach Gesch- which rest upon outwash suggests that the ages nitz, and Daun glacial advances. The late of these bogs are similar. phase of the Sartan Glaciation in Russia, Wood in Sumas till in British Columbia has radiocarbon-dated between about 9000 and been radiocarbon dated at 11,500 ± 1,100 and 11,500 years ago, (Kind, 1965), also appears to 11,000 + 900 years (Armstrong and others, be equivalent to the Sumas. In northern Europe 1965). With the C14 dates from the base of the the Fennoscandian and Ra , built bogs, the upper limit of the Sumas Stade may during the , are correlative. now be established at close to 10,000 years B.P.

REFERENCES CITED Armstrong, J. E., Crandell, D. R., Easterbrook, Easterbrook, D. J., 1963, Late Pleistocene glacial D. J., and Noble, J. B., 1965, Late Pleistocene events and relative sea level changes in the stratigraphy and chronology in southwestern Northern Puget Lowland, Washington: Geol. British Columbia and northwestern Wash- Soc. America Bull., v. 74, p. 1465-1484. ington: Geol. Soc. America Bull., v. 76, p. 1966, Glaciomarine environments and the 321-330. Fraser Glaciation in northwest Washington: Bretz, J H., 1913, Glaciation of the Puget Sound Guidebook for First Annual Field Conf., region: Washington Geol. Survey Bull., no. Pacific Coast Section Friends of the Pleisto- 8, 244 p. cene. Crandell, D. R., Mullineaux, D. R., and Waldron, 1968, Pleistocene stratigraphy of Island H. H., 1958, Pleistocene sequence in south- County, Washington: Washington Dept. eastern part of the Puget Sound Lowland, Water Resources, Water Supply Bull. 25, Washington: Am. Jour. Sci., v. 256, p. 384-397. p. 1-35. 1965, Age and origin of the Puget Sound Easterbrook, D. J., Crandell, D. R., and Leopold, trough in western Washington: U.S. Geol. E. B., 1967, Pre-Olympia Pleistocene stra- Survey Prof. Paper 525-B, p. B132-B136. tigraphy and chronology in the Central Puget Dreimanis, A., Terasmae, J., and McKenzie, Lowland, Washington: Geol. Soc. America G. D., 1966, The Port Talbot Interstade of Bull., v. 78, p. 13-20. the : Canadian Jour. Frye, J. C., Willman, H. B., and Black, R. F., Earth Sci., v. 3, p. 305-325. 1965, Outline of glacial geology of Illinois 2286 D. J. EASTERBROOK—PLEISTOCENE CHRONOLOGY, WASHINGTON

and Wisconsin: in The of the eastern Alps, in Glaciation of the Alps: Colo. United States, Princeton Univ. Press, New Univ. Press, Boulder, p. 143-166. Jersey, p. 43-61. McLellan, R. D., 1927, Geology of the San Juan Hansen, H. P., and Mackin, J. H., 1949, A pre- Islands: Washington Univ. Pub. in Geology, Wisconsin forest succession in the Puget v. 2, 185 p. Lowland, Washington: Am. Jour. Sci., v. Mullineaux, D. R., Waldron, H. H., and Rubin, 247, p. 833-855. Meyer, 1965, Stratigraphy and chronology of Kind, N. V., 1965, Absolute chronology of the late interglacial and early Vashon glacial time main stages of last glaciation and postglacial in the Seattle area, Washington: U.S. Geol. Survey Bull, no. 1194-0, p. 1-10. period in Siberia (according to radiocarbon Richmond, G. M., 1965, Glaciation of the Rocky data): (Abs.) VII International Congress, Mts.; in The Quaternary of the United States, International Assoc. for Quaternary Research. Princeton Univ. Press, New Jersey, p. 217-230. Mayr, F., and Heuberger,, 1968, Type areas of late Willis, B., 1898, Drift phenomena of Puget Sound: glacial and post-glacial deposits in Tyrol, Geol. Soc. America Bull., v. 9, p. 111-162.

MANUSCRIPT RECEIVED BY THE SOCIETY MARCH 4, 1968 REVISED MANUSCRIPT RECEIVED NOVEMBER 1, 1968 Figure 1. Pleistocene section exposed at Yellow Bluff on Guemes Island. Qw—Whidbey Fm.; Op(.-) Possession(?) gravel; Qe Esperaiice Sand; Qf Fraser Drift.

Figure 2. Fossiliferous glaciomarine drift of the Everson Interstade. White objects are marine shells. San Juan Island, Washington..

PLEISTOCENE DEPOSITS IN THE SAN JUAN ISLANDS, WASHINGTON

EASTERBROOK, PLATE 1 Geological Society of America Bulletin, v. 80, no. 11 Figure 1. Peat with Possession Drift at Strawberry Point, Washington. Radiocarbon ages of the peats are indicated on the photograph.

Figure 2. 27,200 year-old peat overlying Possession till and out - wash gravel shown in Figure 1.

POSSESSION DRIFT

EASTERBROOK, PLATE 2 Geological Society of America Bulletin, v. 80, no. 11