Calvin J. Heusser

Quaternary palynology of the Pacific slope of Washington

Abstract Quaternary deposits on the Pacific slope of Washington range in age from the earliest known interglaciation, the Alderton, through the Holocene. Pollen stratigraphy of these deposits is represented by 12 major pollen zones and is ostensibly continuous through Zone 8 over more than 47,000 radiocarbon yr. Before this, the stratigraphy is discontinuous and the chronology less certain. Environments over the time span of the deposits are reconstructed by the comparison of fossil and modern pollen assemblages and the use of relevant meteorological data. The Alderton Interglaciation is characterized by forests of Douglas fir (Pseudotsuga menziesii), alder (Alnus), and fir (Abies). During the next younger interglaciation, the Puyallup, forests were mostly of pine, apparently lodgepole (Pinus contorta), except midway in the interval when fir, western hemlock (Tsuga heterophylla), and Douglas fir temporarily replaced much of the pine. Vegetation outside the limits of Salmon Springs ice (>47,00034,000 yr BP) varied chiefly between park tundra and forests of western hemlock, spruce (Picea), and pine. The Salmon Springs nonglacial interval at the type locality records early park tundra followed by forests of pine and of fir. During the Olympia Interglaciation (34,00028,000 yr BP), pine invaded the Puget Lowland, whereas western hemlock and spruce became manifest on the Olympic Peninsula. Park tundra was widespread during the Fraser Glaciation (28,00010,000 yr BP) with pine becoming more important from about 15,000 to 10,000 yr BP. Holocene vegetation consisted first of open communities of Douglas fir and alder; later, closed forests succeeded, formed principally of western hemlock on the Olympic Peninsula and of western hemlock and Douglas fir in the Puget Lowland. Over the length of the reconstructed environmental record, climate shifted between cool and humid or relatively warm, semihumid forest types and cold, relatively dry tundra or park tundra types. During times of glaciation, average July temperatures are estimated to have been at least 7°C lower than today. Only during the Alderton Interglaciation and during the Holocene were temperatures higher for protracted periods that at present.

Environmental sequence following the Fraser advance of the Juan de Fuca lobe, Washington

Abstract Stratigraphic palynology and radiocarbon chronology of two bogs and a lake on the northwestern Olympic Peninsula serve to record the environmental sequence postdating the Fraser maximum of the Juan de Fuca lobe. Wastage of the lobe in the terminal area began before 14,460 ± 200 BP. Differential downwasting followed, and the last remnants of dead ice probably disappeared some time before 9,380 ± 180 BP. Ablation moraine became sufficiently thick in the course of wastage for a vegetation cover to become established. Arboreal remains of this cover, found buried in till, date between 12,020 ± 210 and 13,380 ± 250 BP. Communities of Pinus contorta first succeeded on deglaciated surfaces during the Vashon Stade. Environmental conditions were comparable to those prevailing in the modern subalpine forest, and average July temperature stood near 12°C. Later, during the Everson Interstade (11,000–13,000 BP.), Alnus and Picea multiplied as temperature increased posibly to as much as 14°. During the Sumas Stade (10,000–11,000 BP.), temperature was again ca. 12°, the cooler climate halting wastage and the spread of Alnus and enabling communities of Picea, Tsuga heterophylla, and T. mertensiana to temporarily achieve stability. Postglacial environments through the Hypsithermal (ca. 3,000 BP) were dominated principally by Alnus. Alnus, succeeded in turn by Picea, invaded the landscape, following the recession of alpine glaciers and the rise in elevation of the snowline. For a time, as suggested by a peak of Pseudotsuga, temperature may have reached close to 17° and annual precipitation less than 760 mm. Arboreal communities were relatively open while light-requiring Pteridium remained conspicuous in the record. After 3000 BP during Neoglaciation, climate became sufficiently cool and moist to favor the development of extensive, closed communities of Tsuga, Picea, Thuja, and other hygrophilous species.

Palynology and phytogeographical significance of a late-Pleistocene refugium near Kalaloch, Washington

A sea cliff facing the open ocean 3 km north of Kalaloch, Washington, and exposing 32 m of interbedded peat, clay, sand, and gravel contains a unique continuous record of late-Pleistocene vegetation and environments on the western side of the Olympic Peninsula. The record obtains from the palynology of plant communities in the unglaciated refugium. Fourteen radiocarbon dates from peat beds in the sea cliff reveal that the record spans the time from 16,700 B. P. to greater than 47,000 B. P. The earliest organic deposits are estimated to date from 70,000 B. P. Pollen assemblages from 222 sample levels in a measured section, divided into 16 zones, are correlated, in the main, with the sequence of Salmon springs, Olympia, and Fraser geologic-climatic units in the Puget Lowland. Correlation derives from the fluctuations of a July average temperature curve reconstructed from the modern vegetation and climatic equivalents of the pollen assemblages. The sequence of stadial and interstadial environments depicted at Kalaloch is found to be more complex than is indicated by the Puget Lowland succession.

Quaternary Vegetation, Climate, and Glaciation of the Hoh River Valley, Washington

The Hoh River valley, on the west side of the Olympic Peninsula, is about 90 km long and is one of the major valleys originating in the interior Olympic Mountains. It was glaciated to its present-day mouth during what is believed to have been the Stuck Glaciation, radiocarbon dated at more than 47,000 yr ago, and later by less extensive ice tongues of Salmon Springs, Evans Creek, and younger ages. Alpine glaciers of Neoglacial age are active today on the slopes of Mount Olympus (2,428 m). Modern vegetation in the valley is predominantly of the rain forest type, divisible into Pacific coastal and subalpine communities. Coastal forest is established at elevations below 500 to 600 m, subalpine forest continues to the tree limit near 1,700 m, and alpine tundra occurs only on the heights in the interior. A winter-wet, cool, temperate climate prevails in the rain forest. Annual precipitation is greater than 3,000 mm, and the average July temperature lies between 12° and 15°C. In the alpine zone, temperatures are a few degrees lower, and precipitation reaches an estimated 5,000 mm or more. Unglaciated ground along the coast adjacent to the Hoh valley was a refugium for Quaternary plant communities of tundra and park tundra during times of glaciation. Vegetation during the Puyallup Interglaciation resembled modern coastal forest and was presumably extensive; later, during Salmon Springs and Fraser Glaciations, tundra spread over the lowland, except during the nonglacial interval between the early and late Salmon Springs Glaciations. At this time and during the Olympia Interglaciation, subalpine forest was in evidence. The pollen stratigraphy and radiocarbon chronology of three bog sections from the lower Hoh valley show tundra at low elevations from 18,800 ± 800 yr B.P. until about 10,000 yr B.P. Holocene vegetation is portrayed by three pollen assemblages: Pinus-Alnus-Picea-Pseudotsuga-Pteridium (10,000 to 8,000 yr B.P.), Picea-Tsuga-Alnus-Pseudotsuga-Pteridium (8,000 to 3,000 yr B.P.), and Tsuga-Thuja-Abies (3,000 to 0 yr B.P.). The sequence implies a climatic trend from a cool and relatively humid climate in the beginning, to increasing warmth, then maximum warmth and lower humidity, and finally to a cooler and quite humid climate at the close. The sequence also reflects the gradual replacement of open, successional forest communities by a late Holocene-age closed rain forest. Pollen influx is low, generally less than 1,500 grains cm −2 yr −1 , except around 8,000 yr. B.P., when values exceeded 5,000 cm −2 yr −1 . Traces of tephra from the eruption of Mount Mazama, found in one bog section, mark an extreme Pacific continental limit for this ejectamenta. Refugia on the Olympic Peninsula contained the stock from which major migrations of plants northwestward along the north Pacific coast took place toward the close of Fraser Glaciation and during Holocene time.

Holocene vegetation history of the Prince William Sound region, south-central Alaska

Abstract Vegetation history during the Holocene is interpreted from the pollen and sedimentary records of nine sections of peat deposits located in sedge tundra at sites in the northern and northwestern parts of the Prince William Sound region. Basal radiocarbon ages of the deposits are between 10,015 and 580 yr B.P. Modern surface pollen data from these and 25 additional sites, ranging from lowlands to an altitude of 675 m in the alpine tundra, were used to aid in the interpretation of the fossil records. Both frequency and influx pollen diagrams of the oldest section disclose a sequence of communities beginning with sedge tundra, containing thickets of willow and alder, followed by alder, which became predominant at about 8300 yr B.P. Later, alder declined, and an inferred growth of sedge tundra and the establishment of colonies of mountain hemlock and Sitka spruce with some western hemlock occurred about 2680 yr B.P. Finally, regrowth of sedge tundra accompanied by the development of forest communites took place over the past 2000 yr. The influence of glacier advances on the vegetation in the fjords occurred during Neoglacial episodes dated at 3200–2500 yr B.P. and during recent centuries. Regional Holocene tectonic activity was also an influential factor, especially at the time of the 1964 earthquake.

Pollen profiles from Southeastern Alaska

The science of pollen analysis on the North American continent has progressed rapidly since its beginning about 25 years ago. This paleo-ecological research technique had been used to unravel the history of postglacial vegetation and climate in Europe for some time before, although its present degree of refinement was developed by von Post in 1916. Fuller (1927) has discussed the early workers, and Cain (1939) has reviewed the later work done in the field. In retrospect, the work of Auer in 1927 marks the first pollen study on this continent in the peat of southeastern Canada. Voss, Sears, Potzger, and others followed in the East and Middle West, and Deevey (1943), of late, is applying the method in New England. The most integrated regional studies have been made by Hansen in the Pacific Northwest (1947b) and more recently in western Canada (1950a, 1952) and Alaska. Peat sections from the North Pacific coastal region of Alaska have not been analyzed for pollen, except for studies at scattered stations at Anchorage (Hansen, personal communication), Kodiak (Bowman 1934), and Adak in the Aleutian Islands (Judson 1946). In coastal British Columbia, the northernmost study has been on Vancouver Island (Hansen 1950b). Thus, the Southeastern Alaska region is situated 400 to 500 miles from the nearest area whose postglacial forest history has been interpreted from pollen profiles. This study, therefore, should serve to narrow the gap in our knowledge of the postglacial phytogeography and climate of the Coast Forest Formation. In addition to the record of postglacial forest succession and climate, it was hoped that the pollen analyses might show evidence of post-Wisconsin vulcanismn, change in sea level, and the advance and retreat of the glaciers in the Coast Range and in the Alexander Archipelago. During the summers of 1950 and 1951, peat sections were obtained from seventeen sites located at Ketchikan, Wrangell, Petersburg, Sitka, and Juneau in an PAGE

Postglacial vegetation on Umnak Island, Aleutian Islands, Alaska

Abstract Pollen analyses of a peat section, 9,945 ± 320 radiocarbon years of age from Umnak Island in the eastern Aleutians, point to a tripartite sequence of postglacial plant communities beginning with a sedge-grass tundra, followed by an interval of willow dominance (8,500 – 3,500 years ago), and ending with a grass-sedge tundra.

Pollen Profiles from Prince William Sound and Southeastern Kenai Peninsula, Alaska

Two earlier papers discussed the pollen and peat stratigraphy of southeastern Alaska muskegs and its relation to postglacial phytogeography, climate, glacier variation, land-sea level fluctuation, and vulcanism (Heusser 1952, 1954). In an effort to extend these studies to the northwest along the border of the Gulf of Alaska, five peat sections were taken from muskegs in coastal southern Alaska, on southeastern Kenai Peninsula, and on eastern Prince William Sound. The localities at which muskegs have been sampled are shown by number on the accompanying sketch map (Fig. 1). One of the objectives of this paper is to trace the postglacial dispersal of the trees of the Coast Forest Formation in this district. Furthermore, since the district is at present part of an ecotone or transition between tundra and the coast forest (Cooper 1942), another objective is to show the postglacial relation of these two formations. The study region is also of interest in that it represents the northern terminus for two members of the coast forest. Western hemlock (Tsuga heteroPhvllal), which comprises almost 75 per cent of this forest in the Alexander Archipelago (Taylor 1932), 500 to 800 rniles southeastward, and Alaska yellow cedar (Chamaecyparis nootkatensis) extend as far as western Prince Williamn Sound. Recent palynological investigations by Livingstone (1953), Hansen (1953), and the Alaska Terrain and Permafrost Section of the U. S. Geological Survey (William S. Benninghoff, personal communication) and those made earlier by Bowman (1934) and Knox (Judson 1946) are gradually unfolding the postglacial and earlier Pleistocene events in the Territory. Geologists, in addition, are making a concerted effort to map the Pleistocene glaciations and construct a chronology (Pewe, et al. 1953). It is the purpose of this paper to add to this evolving store of information and at the same time to augment our knowledge of the postglacial development of the Coast Forest Formation as we know it today. Field work connected with this study was supported by a Sigma Xi-Resa Grant-in-Aid and a grant from the Glacier Study Project of the American Geographical Society. Travel to the Territory was afforded by the Juneau Ice Field ResearclhL Project which is administered by the Nomenclature follows Hulten (1941-1950) ; in some cases plant names given in references cited in the text have been changed to follow Hulten.