Article

Late Quaternary Vegetation in the Southwestern Columbia Basin, Washington

January 1985
Quaternary Research 23(1):109-122

January 1985
23(1):109-122

Authors:

Montana State University

A 33,000-yr pollen record from Carp Lake provides information on the vegetation history of the forest/steppe border in the southwestern Columbia Basin. The site is located in the Pinus ponderosa Zone but through much of late Quaternary time the area was probably treeless. Pollen assemblages in sediments dating from 33,000 to 23,500 yr B.P. suggest a period of temperate climate and steppe coinciding with the end of the Olympia Interglaciation. The Fraser Glaciation (ca. 25,000–10,000 yr B.P.) was a period of periglacial steppe or tundra vegetation and conditions too dry and cold to support forests at low altitudes. Aridity is also inferred from the low level of the lake between 21,000 and 8500 yr B.P., and especially after about 13,500 yr B.P. About 10,000 yr B.P. Chenopodiineae and other temperate taxa spread locally, providing palynological evidence for a shift from cold, dry to warm, dry conditions. Pine woodland developed at the site with the onset of humid conditions at 8500 yr B.P.; further cooling is suggested at 4000 yr B.P., when Pseudotsuga and Abies were established locally.

Holocene vegetation history and fire regimes of Pseudotsuga menziesii forests in the Gulf Islands National Park Reserve, southwestern British Columbia, Canada

Article

May 2013

Pollen analysis of a 9.03-m-long lake sediment core from Pender Island on the south coast of British Columbia was used to reconstruct the island's vegetation history over the last 10,000 years. The early Holocene was characterized by open mixed woodlands with abundant Pseudotsuga menziesii and a diverse understory including Salix and Rosaceae shrubs and Pteridium aquilinum ferns. The establishment of Quercus garryana savanna-woodland with P. menziesii and Acer macrophyllum followed deposition of the Mazama tephra until ~ 5500 cal yr BP, when these communities gave way to modern mixed P. menziesii forest. Charcoal analyses of the uppermost sediments revealed low charcoal accumulation over the last 1300 years with a mean fire return interval (mFRI) of 88 years. Fires were more frequent (mFRI = 50 yr) during the Medieval Climate Anomaly (MCA) with warm, dry conditions facilitating a higher fire frequency than during the Little Ice Age, when fires were infrequent. Given the projected warming for the next 50–100 years, land managers considering the reintroduction of fire to the Gulf Islands National Park Reserve may want to consider using the mFRI of the MCA as a baseline reference in prescribed burning strategies.

Reconstruction of the late Pleistocene grassland of the Columbia Basin, Washington, USA, based on phytolith records in loess

Article

Jan 2002
PALAEOGEOGR PALAEOCL

Silica phytoliths preserved in three loess sections in southeastern Washington State revealed a 100 000-year history of the Columbia Basin grassland. Changes in the proportion of different morphotypes indicate large shifts in vegetation composition during the last 100 ka. A low-elevation section (677 m asl) near the center of the basin provided a record of alternating xeric Festuca–Poa and mesic Festuca–Koeleria grassland. The middle-slope section (1095 m asl) supported Picea–Abies or Pinus ponderosa forest or non-analog parkland at different times. Some trees were present at or near the site even during the Last Glacial Maximum. The highest site (1220 m asl) supported Stipa-, Festuca- and Poa-dominated grassland with some Artemisia shrub during most of the late Pleistocene, but supports a coniferous forest today. Variations in vegetation can be explained as a response to changes in large-scale climatic controls. Grasslands and shrub steppe were apparently more widespread and forests more restricted than today during the marine isotope stages 2 and 4, probably as a result of cooler and drier conditions. The three new records are well correlated with previously published paleo-reconstructions based on phytolith, cicada burrow and stable isotope data from a nearby KP-1 loess section, Carp Lake pollen record, and global ice volume variations.

Loess–paleosol carbonate clumped isotope record of late Pleistocene–Holocene climate change in the Palouse region, Washington State, USA

Article

Jul 2018

The Channeled Scabland–Palouse region of the Pacific Northwest (PNW) of the United States preserves geomorphic and pedosedimentary records that inform understanding of late Pleistocene–Holocene paleoclimate change in a region proximal to the last glacial period Cordilleran Ice Sheet. We present a clumped (Δ 47 ) and conventional (δ ¹⁸ O, δ ¹³ C) isotopic study of Palouse loess–paleosol carbonates in combination with carbonate radiocarbon ( ¹⁴ C) dating to provide new measures of regional late–last glacial (~31–20 cal ka BP) and Holocene soil conditions. Average clumped isotope temperatures (T(Δ 47 )) for last glacial Palouse loess–paleosol carbonates (9±4°C) are significantly lower than those for Holocene-aged carbonates (T(Δ 47 )=18±2°C) in study sections. Calculated soil water δ ¹⁸ O VSMOW values (−16±2‰) for last glacial carbonates are also offset relative to those for Holocene-aged samples (−11±1‰), whereas calculated soil CO 2 δ ¹³ C VPDB values are similar for the Holocene (−16.9±0.2‰) and late–last glacial (−16.7±1.1‰) periods. Together, these paleoclimate metrics indicate late–last glacial conditions of pedogenic carbonate formation in the C 3 grassland soils of the Palouse were measurably colder (9±5°C) than during the Holocene and potentially reflect a more arid last glacial paleoclimate across the Palouse, findings in agreement with previous proxy studies and climate model simulations for the region.

Post-glacial migration, limitations to poleward range expansion, and growth responses to future climates of plants in the Garry oak ecosystem

Article

Full-text available

Nov 2009

Travis D. Marsico

A key goal in ecology is to understand the factors limiting species’ distributions. Important range-limiting factors are often difficult to generalize, however, because organisms have many different life-history traits, evolutionary histories, and diverse interactions with other species. Climate is often implicated as the most important range-limiting factor in modern species distributions. Yet many species are not or not yet exhibiting range changes associated with anthropogenic climate change. A potentially important non-climatic range-limiting factor is dispersal limitation. Recently, some researchers have concluded that dispersal limitation is likely as strong a range limiting factor as climate. One way to tackle the limits to generalization is to investigate range limiting factors and patterns of range shift for well-chosen taxa in a comparative fashion to glean general principles. My research uses a comparative approach to investigate patterns of post-glacial colonization, factors involved in geographic range limitation, and species responses to future climates using genetic techniques, a field experiment, and a chamber experiment, respectively. All studies were conducted on species associated with the Garry oak ecosystem in the Pacific Northwest of North America and focused on four plant taxa: Quercus garryana var. garryana, the flagship species of the Garry oak ecosystem, and three Lomatium species, L. dissectum var. dissectum, L. nudicaule, and L. utriculatum. An overall conclusion from this dissertation is that related, co-occurring species provide an appropriate comparison for determining species- and trait-based generalization. Lomatium chloroplast genetic data suggest that abundance is important in determining the ability of long-distance seed dispersal. The field experiment shows that dispersal limitation is currently important in determining range boundaries for species no matter their regional abundance. The field experiment also shows that closely related species may differ in their competitive abilities and responses to competitors/facilitators. My genetic survey on Q. garryana provides evidence that generalizations about range changes in oaks as a taxonomic group seem to be relatively universal, no matter the historical landscape conditions. The chamber experiment provides evidence that some responses to global change will be unpredictable, making certain generalizations difficult. Given these findings, humans may consider accelerating species migration through purposeful translocation outside species’ ranges to overcome dispersal barriers.

PHYLOGEOGRAPHY OF DOUGLAS-FIR: TESTING HYPOTHESES FROM THE FOSSIL RECORD

Thesis

Full-text available

Jun 2010

Paul F. Gugger

Late Quaternary Vegetation History of Northern North America Based on Pollen, Macrofossil, and Faunal Remains

Article

Jan 2005

Arthur S. Dyke

Biome maps spanning the interval from the last glacial maximum to modern times are presented. The biome distributions at 18 ka BP were probably as nearly in equilibrium with climate as are the modern distributions, but deglacial biomes were probably in disequilibrium. Ice sheet configuration was a strong control of climate until 7 ka BP. Regional climate trends Gan be inferred from changing biome distributions, but during periods of disequilibrium, biome distributions under-represent summer warming. Because of summer cooling by 2-4 °C during the Holocene, largely in the last 3-5 ka, middle and certain early Holocene biome distributions and species compositions are reasonable analogues of future equilibrium displacements due to equivalent warming, at least in areas that were long-since deglaciated. Past biome migration rates in response to rapid regional warming during deglaciation were mainly in the range of 100-200 m per year. If these rates pertain in the future, biomes may shift 10-20 km in most regions over the next century. A major impediment to using former Holocene conditions as a guide to future conditions is that warmer Holocene summers were accompanied by colder winters, whereas warmer future summers will be accompanied by warmer winters.

Reconstruction and climatic interpretation of a late Pleistocene peat deposit in northwestern Oregon

Article

Full-text available

Jan 2002

Summary 1 Climatic models predict that postglacial conditions in the Pacific Northwest of North America (between 11'000 and 10'000 years BP) were about 2-3 °C cooler than at present. These models were tested by examining plant macrofossils and insect remains in a late Pleistocene peat deposit in northwestern Oregon. 2 Stratigraphy in trenches (540 cm depth) revealed peat from 225 to 420 cm soil depth. The peat structure suggests that an open water body formed at the site some 13'000 years BP and terrestrialized into a Sphagnum bog. Seeds of the bog bean, Menyanthes trifoliata, were found in the peat between 240 and 420 cm depth. The age of this layer was 14 C-dated to approximately 10'000-11'000 years BP. 3 Temperatures at present-day sites of M. trifoliata in Oregon (at elevations from 854 to 1768 m a.s.l.) indicate that the species grows at sites with a yearly mean temperature range of 4.4-7.9 °C, in contrast to 11.1 °C at the study site (49 m a.s.l.), where the species does no longer occur. This suggests that temperatures at the study site in the late Pleistocene were at least 3-4 °C cooler than at present. 4 The possible association of these temperature changes to the universal Young Dryas cooling and post-Young Dryas warming event is discussed. 5 The discovery of three small flakes, a core, and fractured deer-size large mammal bones in the peat suggests the presence of Paleoamericans in the surroundings. Sharp breakage edges on many seeds of M. trifoliata might indicate that these seeds were used by humans, possibly because the latter knew about the medicinal properties of M. trifoliata.

Origin, development, and dynamics of coastal temperate conifer rainforests of southern Vancouver Island, Canada

Article

Full-text available

Feb 2011
CAN J FOREST RES

Pollen and charcoal from East Sooke Fen, Pixie Lake, and Whyac Lake were used to reconstruct the post glacial vegetation, climate, and fire-disturbance history across a precipitation gradient on southern Vancouver Island, British Columbia. An open Pinus woodland covered the landscape in the early late-glacial interval. Fires were absent under a cool and dry climate. Closed mixed conifer forests of Pinus, Picea, Abies, Tsuga heterophylla (Raf.) Sarg., and Tsuga mertensiana (Bong.) Carrière replaced the Pinus biogeochron in the late late-glacial interval. Fires became more common even though climate was cool and moist. Open Pseudotsuga menziesii (Mirb.) Franco forests expanded westward during the warm dry early Holocene, though closed Picea and Tsuga heterophylla forests grew in the wettest part of the area at Whyac Lake. Modern precipitation gradients likely originated at this time. Fires occurred in forested ecosystems, although East Sooke Fen at the driest end of the gradient experienced less fire. The middle and late Holocene was characterized by increasing precipitation and decreasing temperature, respectively. Quercus garryana Dougl. stands spread westward during the mid-Holocene. Extant closed Tsuga heterophylla and Cupressaceae (Thuja plicata Donn. ex D. Don) forests arose in the wetter part of the gradient, whereas Pseudotsuga forests occupied drier eastern areas. During this interval, fires were rare in wet western regions but apparently more common in dry eastern regions.

Glacial populations and postglacial migration of Douglas-fir based on fossil pollen and macrofossil evidence

Article

Aug 2010
QUATERNARY SCI REV

To understand how temperate forests might respond to future episodes of global warming, it is important to study the effects of large-scale climate change brought about by rapid postglacial warming. Compilations of fossil evidence have provided the best evidence of past plant range shifts, especially in eastern North America and Europe, and provide a context for interpreting new molecular datasets from modern forests. In western North America, however, such reviews have lagged even for common, widespread taxa. Here, we synthesize fossil evidence for Douglas-fir (Pseudotsuga menziesii) from nearly 550 fossil pollen, sedimentary macrofossil, and packrat midden macrofossil sites to develop hypotheses about the species’ late Quaternary history that can be tested with molecular phylogeographic studies. For both the coastal and interior varieties, we identified alternative hypotheses on the number of glacial populations and postglacial migration patterns that can be characterized as single-population versus multiple-population hypotheses. Coastal Douglas-fir may have been subdivided into two populations at the Last Glacial Maximum (LGM) and colonized British Columbia from populations in Washington and Oregon. Interior Douglas-fir could have been subdivided along major topographic barriers into at least three LGM populations and colonized British Columbia and Alberta from populations in northwest Wyoming and/or northeast Utah. For both varieties, we calculated migration rates lower than previous studies, which could have been as high as 100–220 m/yr if Douglas-fir reached its modern distribution 9000 cal yr BP, or as low as 50 m/yr if it reached its modern range at present. The elevational range of populations in California and the southern Rockies shifted upslope by 700–1000 m. If there were multiple LGM populations, these elevational shifts suggest that those populations did not contribute to the colonization of Canada. Our findings emphasize the possibility of low-density northern LGM populations and that populations within species react individualistically in response to large-scale climate change.

The impact and significance of tephra deposition on a Holocene forest environment in the North Cascades, Washington, USA

Article

Jan 2016

High-resolution palaeoecological analyses (stratigraphy, tephra geochemistry, radiocarbon dating, pollen and ordination) were used to reconstruct a Holocene vegetation history of a watershed in the Pacific Northwest of America to evaluate the effects and duration of tephra deposition on a forest environment and the significance of these effects compared to long-term trends. Three tephra deposits were detected and evaluated: MLF-T158 and MLC-T324 from the climactic eruption of Mount Mazama, MLC-T480 from a Late Pleistocene eruption of Mount Mazama and MLC-T485 from a Glacier Peak eruption. Records were examined from both the centre and fringe of the basin to elucidate regional and local effects. The significance of tephra impacts independent of underlying long-term trends was confirmed using partial redundancy analysis. Tephra deposition from the climactic eruption of Mount Mazama approximately 7600 cal. years BP caused a significant local impact, reflected in the fringe location by changes to open habitat vegetation (Cyperaceae and Poaceae) and changes in aquatic macrophytes (Myriophyllum spicatum, Potamogeton, Equisetum and the alga Pediastrum). There was no significant impact of the climactic Mazama tephra or other tephras detected on the pollen record of the central core. Changes in this core are potentially climate driven. Overall, significant tephra fall was demonstrated through high resolution analyses indicating a local effect on the terrestrial and aquatic environment, but there was no significant impact on the regional forest dependent of underlying environmental changes.

The impact and significance of tephra deposition on a Holocene forest environment in the North Cascades, Washington, USA

Article

Full-text available

Mar 2016

Climate and terrestrial ecosystem change in the U.S. Rocky Mountains and Upper Columbia Basin: Historical and future perspectives for natural resource management.

Technical Report

Full-text available

Jan 2010

"Pinedale Deglaciation and Subsequent Holocene Environmental Changes and Geomorphic Responses in the Central Lemhi Mountains, Idaho, U.S.A

Article

Full-text available

Jan 1986

David R. Butler

In several glaciated valleys along the eastern front of the Lemhi Mountains, subalpine meadows are located along the central axes of the valleys, in positions immediately upvalley of arcuate Pinedale readvance moraines. The meadows are comprised of varying thicknesses of finegrained sediments which were impounded by the damning action of the moraines. These sediments, and pollen contained therein, record complex environmental fluctuations which accompanied déglaciation and postglacial recovery. The thickness of sediments in each meadow is a function of the proficiency of the arcuate moraines as dams. The presence of Glacier Peak B ash in one meadow illustrates that, at minimum, the lower one-third of that valley was deglaciated prior to approximately 11,250 yr BP. Over one meter of glacial-runoff sediments underlies the ash ; sedimentation rates in the meadow suggest that déglaciation in the lower portions of the valley may have been complete before 11,500 yr BP. Sedimentation rates slowed dramatically after 10,000 yr BP. A cold, early HoIocene climatic episode may have occurred around 7500 yr BP. Massive protalus landforms were deposited during the Indian Basin Advance. Later Neoglacial landforms were areally restricted to the most shaded, climatically-favorable locations.

Needle flavonoid variation in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) populations

Article

Feb 2011
CAN J BOT

The variability of six Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) populations was studied with the help of needle flavonoids. Of the two proanthocyanidins and six flavonols detected and measured by high performance liquid chromatography, myricetin and prodelphinidin allowed partial separation of the sampled coastal Douglas-fir populations into three geographical groups. Even though conspicuous differences were found between the northernmost and southernmost provenances, flavonoid markers were insufficient to identify the origin of a coastal Douglas-fir population without ambiguity. In accordance with other genetic markers, it would be inappropriate to recognize races within the sampled area of coastal Douglas-fir. From a biogenetical point of view, the synthesis of prodelphinidin appears to be governed by a gene present in two codominant allelic forms. The alleles are differently expressed from one population to another in such a way that there is a latitudinal cline of prodelphinidin throughout the sampled coastal Douglas-fir populations. The gradual decrease of prodelphinidin from south to north tends to support the idea that coastal Douglas-fir has migrated in this same direction from ice-free refugia of the Wisconsin glaciation period. To confirm the latitudinal cline and the mode of inheritance of prodelphinidin in coastal Douglas-fir, additional populations should be analyzed and segregation data from known pedigrees should be obtained respectively.Key words: Pseudotsuga menziesii var. menziesii, Pinaceae, flavonoids, geographical variation.

Younger Dryas environments and human adaptations on the West Coast of the United States and Baja California

Article

Full-text available

Oct 2011
QUATERN INT

On the Pacific Coast of the United States and Baja California, the Younger Dryas was one component of dynamic Late Pleistocene and Holocene environmental changes. Changing climate, sea level rise, and shifting shorelines created ecological challenges for ancient coastal peoples and daunting challenges for archaeologists searching for early coastal sites. This paper reviews the evidence for ecological change in this ‘West Coast’ region, including shoreline changes that may have submerged or destroyed archaeological sites from this time period. Examining the regional record of human occupation dating to the Younger Dryas, well-dated coastal sites are limited to California’s Northern Channel Islands and Isla Cedros off Baja California. A small number of fluted points found in coastal areas may also date to the Younger Dryas, but their context and chronology is not well defined. Review of the implications of these two data sets considers whether the early but discontinuous Younger Dryas archaeological record from the West Coast might result from a migration of maritime peoples from Northeast Asia into the Americas.

Patterns of seed dispersal and pollen flow in Quercus garryana (Fagaceae) following post-glacial climatic changes

Article

May 2009
J BIOGEOGR

Aim We examined the genetic structure of Quercus garryana to infer post‐glacial patterns of seed dispersal and pollen flow to test the hypotheses that (1) peripheral populations are genetically distinct from core populations and from one another; (2) genetic diversity declines towards the poleward edge of the species’ range; and (3) genetic diversity in the chloroplast genome, a direct measure of seed dispersal patterns, declines more sharply with increasing latitude than diversity in the nuclear genome. We address our findings in the context of known historical oak distribution from pollen core data derived from previously published research. Location Oak–savanna ecosystems from southern Oregon, USA (core populations/non‐glaciated range) northward to Vancouver Island, British Columbia, Canada (peripheral populations/glaciated range). Methods We genotyped 378 trees from 22 sites with five chloroplast and seven nuclear microsatellite loci. For both sets of markers, we estimated genetic diversity and differentiation using an analysis of molecular variance and generated Mantel correlograms to detect genetic and geographical distance correlations. For the nuclear markers, we also used a Bayesian approach to infer population substructure. Results There was a large degree of population differentiation revealed by six chloroplast haplotypes, with little (≤ 3) or no haplotype diversity within sites. Peripheral island locations shared the same, maternally inherited chloroplast haplotype, whereas locations in mainland Washington had greater haplotype diversity. In contrast, genetic diversity of the nuclear markers was high at all locations sampled. Populations clustered into two groups and were significantly positively correlated over large spatial scales (≤ 200 km), although allele richness decreased significantly with latitude. Population substructure was observed between core and peripheral populations because rare alleles were absent in peripheral localities and common allele frequencies differed. Main conclusions The observed pattern of chloroplast haplotype loss at the northern periphery suggests restricted seed dispersal events from mainland sites to peripheral islands. This pattern was unexpected, however, as refugial oak populations remained near the current post‐glacial range even during the Last Glacial Maximum. Using nuclear markers, we found high within‐population diversity and population differentiation only over large spatial scales, suggesting that pollen flow is relatively high among populations.

Faunal burrows as indicators of paleo-vegetation in eastern Washington, USA

Article

May 2001
PALAEOGEOGR PALAEOCL

The Palouse loess deposits in the Pacific Northwestern United States contain buried paleosols with distinctive biological fabrics. The Washtucna Soil, formed 40,000–15,000 yr ago during the last full glacial, contains up to 90% by volume distinctive cylindrical pedotubules that are 1–2 cm in diameter formed by burrowing fauna. The overlying post-glacial loess and modern surface soils that support perennial grasslands lack these cylindrical burrows. We investigated the paleoecological significance of the burrows. Observations of several types of burrowing fauna under native vegetation indicated that nymphs of cicadas (Homoptera: Cicadidae) are responsible for cylindrical, back-filled burrows that match those in the Washtucna Soil. We measured the abundance of active cicada burrows in soils in four native vegetation zones (Soil sites), establishing that cicada burrows comprise 19% of the rooting zone volume in sagebrush steppe, but just 1–3% of the rooting zone volume in bunchgrass steppe, meadow steppe and coniferous forest. This suggests strongly that abundant cicada burrows in paleosols are a proxy for the geographic extent of plant communities that contained sagebrush. To assay the activity of cicada nymphs through time, we measured burrowed volume by depth from the soil surface down through the Washtucna Soil (i.e. from the present to ca. 40,000 yr bp) at five stratigraphic research sites (Paleosol sites). Cicada-burrowed volume is generally less than 5% in the rooting zone of the surface soils and throughout Holocene loess, but is up to 94% in the rooting zone of the Washtucna Soil at Paleosol sites that currently support bunchgrass steppe outside the present-day sagebrush steppe zone. Cicada host preferences in vegetation zones today suggest that sagebrush was the dominant shrub as the Washtucna Soil formed. From this reconstruction, combined with information from studies of pollen and plant opal, we infer that periglacial steppe plant communities dominated by sagebrush spread, from 40,000 to 15,000 yr bp, into areas of the Columbia Plateau that support bunchgrass steppe, meadow steppe, and even some coniferous forest today. Trace fossils of soil fauna in paleosols are indicators of fluctuations in biological activity in response to climatic changes of the Quaternary Period in Palouse loess deposits.

West Coast vegetation shifts as a response to climate change over the past 130,000 years: geographic patterns and process from pollen data

Article

Oct 2021

We compiled pollen sequences from lake and offshore cores at least 6,000 years old (6 ka) for the Mediterranean and Marine ecoregions of the US West Coast. Principal Component Analysis highlighted vegetation differences in core-tops, the Holocene Thermal Maximum (6 ka) and Last Glacial Maximum (LGM, 19 ka). Core-top and HTM ordination produced clusters that reflected geographic clusters in the Sierra Nevada, and the Pacific Northwest coast. Little change in these clusters between 6-0 ka suggested that vegetation communities in coastal and alpine settings persisted, despite warmer global temperatures. PCA outliers reflect distinct pollen assemblages that often were isolated sites or bordered the Great Basin. During the LGM, greater shrub and herb presence in the Marine ecoregion interior indicated enhanced aridity, while conifer presence in coastal and Southern California indicated moist conditions. Qualitatively, tree taxa from the Last Interglacial (~130–120 ka) showed how vegetation shifted over 6–10 kyr from alder, to oak, then redwood, a successional pattern that began again at the Late Glacial (~15 ka). In future West Coast pollen studies, sampling and chronologic control at centennial resolution will enable further study of more time periods and rates of vegetation change in response to climate.

A multiproxy database of western North American Holocene paleoclimate records

Article

Full-text available

Apr 2021

Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 184 terrestrial and marine sites, including 381 individual proxy records. The records span at least 4000 of the last 12 000 years (median duration of 10 725 years) and have been screened for resolution, chronologic control, and climate sensitivity. Records were included that reflect temperature, hydroclimate, or circulation features. The database is shared in the machine readable Linked Paleo Data (LiPD) format and includes geochronologic data for generating site-level time-uncertain ensembles. This publicly accessible and curated collection of proxy paleoclimate records will have wide research applications, including, for example, investigations of the primary features of ocean–atmospheric circulation along the eastern margin of the North Pacific and the latitudinal response of climate to orbital changes. The database is available for download at https://doi.org/10.6084/m9.figshare.12863843.v1 (Routson and McKay, 2020).

A multiproxy database of western North American Holocene paleoclimate records

Preprint

Full-text available

Sep 2020

Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 209 terrestrial and marine sites, including 382 individual proxy records. The records span at least 4000 of the last 12 000 years (median duration = 10 603 years), and have been screened for resolution, chronologic control, and climate sensitivity. Records were included that reflect temperature, hydroclimate, or circulation features. The database is shared in the machine readable Linked Paleo Data (LiPD) format and includes geochronologic data for generating site-level time-uncertain ensembles. This publicly accessible and curated collection of proxy paleoclimate records will have wide research applications, including, for example, investigations of the primary features of ocean-atmospheric circulation along the eastern margin of the North Pacific and the latitudinal response of climate to orbital changes. The database is available for download at: https://doi.org/10.6084/m9.figshare.12863843.v1 (Routson and McKay, 2020).

A global database of Holocene paleotemperature records

Article

Full-text available

Apr 2020

A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format. === Open access article: https://rdcu.be/b3y6w ===

Is the Last Glacial Maximum a reverse analog for future hydroclimate changes in the Americas?

Article

Full-text available

Apr 2019
CLIM DYNAM

Future hydroclimate change is expected to generally follow a wet-get-wetter, dry-get-drier (WWDD) pattern, yet key uncertainties remain regionally and over land. It has been previously hypothesized that lake levels of the Last Glacial Maximum (LGM) could map a reverse analog to future hydroclimate changes due to reduction of CO2 levels at this time. Potential complications to this approach include, however, the confounding effects of factors such as the Laurentide Ice Sheet and lake evaporation changes. Using the ensemble output of six coupled climate models, lake energy and water balance models, an atmospheric moisture budget analysis, and additional CO2 sensitivity experiments, we assess the effectiveness of the LGM as a reverse analog for future hydroclimate changes for a transect from the drylands of North America to southern South America. The model ensemble successfully simulates the general pattern of lower tropical lake levels and higher extratropical lake levels at LGM, matching 82% of the lake proxy records. The greatest model-data mismatch occurs in tropical and extratropical South America, potentially as a result of underestimated changes in temperature and surface evaporation. Thermodynamic processes of the mean circulation best explain the direction of lake changes observed in the proxy record, particularly in the tropics and Pacific coasts of the extratropics, and produce a WWDD pattern. CO2 forcing alone cannot account for LGM lake level changes, however, as the enhanced cooling from the Laurentide ice sheet appears necessary to generate LGM dry anomalies in the tropics and to deepen anomalies in the extratropics. LGM performance as a reverse analog is regionally dependent as anti-correlation between LGM and future P − E is not uniformly observed across the study domain.

A luminescence chronology for loess deposition in Washington State and Oregon, USA

Article

Jan 1999

The loess of the Columbia Plateau in the northwest United States provides a valuable palaeoenvironmental record which spans a large part of the Quaternary. Luminescence dating has been carried out on three sites from the Walla Walla region, and ages obtained combine with those from previous studies to show substantial loess accumulation during the periods 60-45 ka, and 15 ka onwards, with little record of loess deposition during the period 35-18 ka. The amount of sedimentation at a site is related to the proximity to the source areas of the loess, especially towards the end of these periods. Luminescence ages obtained are in agreement with the available independent age control from well characterised tephra units interbedded within the loess.

North America

Chapter

Jan 1988

Since the beginning of the Pliocene, approximately 5 My ago, operative modes of the global climate system have changed repeatedly, with high-amplitude glacial-nonglacial fluctuations inferred from proxy climate data in the last approximately 2.4 My (Shackleton et aL, 1984). The nature of continental environments during these climatic changes is comparatively unknown. With rare exceptions, such as the 3.5 My vegetational history from Colombia, South America (Hooghiemstra, 1984), or the 3.2 My pluvial history of Searles Lake, California (Smith, 1984), most Pliocene and Pleistocene continental records are fragmentary and brief. North American vegetation history between 5 My and 20 ky B.P. is limited in space and time, and often lacks precise chronostratigraphic control. The late Cenozoic time scale used throughout this chapter (Table 1) is adapted from Berggren et al (1985), Martinson et at. (1987), and Richmond and Fullerton (1986). Although pollen records from the United States and Canada provide the most extensive and continuous documentation of past vegetation, few extend beyond 50 ky ago. Following a survey of Pliocene vegetation of the United States and Canada, this chapter will focus on the history of Quaternary vegetation in two regions with continuous, chrono-stratigraphically-controlled pollen data from the last 130 ky — the prairie-forest boundary of north central United States and the Pacific Coastal Forest of western United States (Heusser, C. J., 1977, 1982, 1985; Heusser and Shackleton, 1979; King, 1973; King and Saunders, 1986).

Late Quaternary Environments in Ruby Valley, Nevada

Article

Jan 1992

Robert Thompson

Palynological data from sediment cores from the Ruby Marshes provide a record of environmental and climatic changes over the last 40,000 yr. The modern marsh waters are fresh, but no deeper than ∼3 m. A shallow saline lake occupied this basin during the middle Wisconsin, followed by fresh and perhaps deep waters by 18,000 to 15,000 yr B.P. No sediments were recovered for the period between 15,000 and 11,000 yr B.P., possibly due to lake desiccation. By 10,800 yr B.P. a fresh-water lake was again present, and deeper-than-modern conditions lasted until 6800 yr B.P. The middle Holocene was characterized by very shallow water, and perhaps complete desiccation. The marsh system deepened after 4700 yr B.P., and fresh-water conditions persisted until modern times. Vegetation changes in Ruby Valley were more gradual than those seen in the paleolimno-logical record. Sagebrush steppe was more widespread than at present through the late Pleistocene and early Holocene, giving way somewhat to expanded shadscale vegetation between 8500 and 6800 yr B.P. Shadscale steppe contracted by 4000 yr B.P., but had greater than modern coverage until 1000 to 500 yr ago. Pinyon-juniper woodland was established in the southern Ruby Mountains by 4700 yr B.P.

Geographic distribution and biogeography of representative species of xeric grassland-adapted Nearctic Lygaeidae in western North America (Insecta: Heteroptera)

Article

Jan 1993

G.G.E. Scudder

This paper outlines the known distribution of eight xeric grassland-adapted species of Lygaeidae, and examines these distributions with respect to the glacial history of North America during the Pleistocene, and past and present distribution of grassland vegetation. Four of these species (Neosuris castanea, Sisamnes claviger, Ligyrocoris latimarginatus, and Melanopleurus perplexus) probably survived the Pleistocene in refugia south of the Late Wisconsinan ice sheet. Differences in climatic requirements may explain the variations in geographic distribution exhibited by these four insects and a methodology for testing this is discussed. The four other species (Crophius ramosus, Kolenetrus plenus, Slaterobius insignis, and Emblethis vicarius) may have occurred in the north prior to 1.2 mya and survived the Late Pleistocene in both the northern Beringian refugium and in southern refugia. Molecular systematics, especially use of DNA restriction site or sequence data, might provide the evidence needed to test historical biogeographic postulates based on the extant distribution of these species.

Late Quaternary Biogeography of the Pygmy Rabbit (Brachylagus idahoensis) in Eastern Washington

Article

Feb 1991

R. Lee Lyman

The historic distribution of pygmy rabbits (Brachylagus idahoensis) is discontinuous between the Great Basin and eastern Washington. Available data indicate disjunction may have occurred during the latest Pleistocene and earliest Holocene. Extralimital records indicate that the range of the pygmy rabbit decreased in eastern Washington during the last 3,000 years as the extent of sagebrush (Artemisia tridentata)-dominated steppe diminished. Relative abundances of pygmy rabbits and pocket gophers (Thomomys talpoides) in eastern Washington also appear to reflect responses to changes in the distribution and abundance of sagebrush.

Geologic, Geoarchaeologic, and Historical Investigation of the Discovery Site of Ancient Remains in Columbia Park, Kennewick, Washington

Article

Chromosome races in Sarcobatus (Sarcobataceae, Caryophyllales)

Article

Full-text available

Oct 1999

Sarcobatus Nees., a genus of North American halophytic shrubs, consists of 2 species: S. vermiculatus (Hook.) Torr. (n = 18, 36), which is widespread in western North America, and S. baileyi Cov. (n = 54), endemic to Nevada. Within S. vermiculatus, populations of n = 36 are widely distributed, whereas populations of n = 18 are found only in the Sonoran Desert, northern California, and northwestern Great Plains, locations at the periphery of the species range. Although the chromosome number of n = 18 is apparently tetraploid, failure to form an n = 27 race intermediate to those of n = 18 and n = 36 suggests that n = 18 S. vermiculatus is of significant age and that it behaves chromosomally as a diploid. Sarcobatus has a long fossil pollen record and endured Pleistocene climatic extremes with little range displacement.

A transient flux model for convective infiltration: Forward and inverse solutions for chloride mass balance studies

Article

Sep 1997

Forward and inverse solutions are provided for analysis of inert tracer profiles resulting from one-dimensional convective transport under fluxes which vary with time and space separately. The approach is developed as an extension of conventional chloride mass balance techniques used to analyze vertical unsaturated aqueous phase transport over large timescales in arid environments. This generalized chloride mass balance (GCMB) approach allows incorporation of transient fluxes and boundary values of precipitation and chloride mass deposition and allows analysis of a tracer profile which does not remain constant with depth below the extraction zone, in terms of a purely convective water transport model. The conventional quasi-steady state chloride mass balance (CMB) can be derived from the transient GCMB model developed here. By specifying a link between precipitation and recharge, closed-form forward and inverse solutions relating soil water chloride concentrations to transient boundary fluxes are obtained. This link is necessary for quantitative analysis of variable chloride profiles arising from climatic change. The GCMB can use transient chloride mass deposition rates, transient precipitation, and transient evapotranspiration rates. If two of these quantities are known or if the time frame is constrained such that a quantity can be treated as constant, then the inverse model can be used to determine the third. When mixing processes are limited, the GCMB can provide an alternative approach for estimating paleoprecipitation for performance-assessment modeling. The GCMB model is demonstrated with the following applications: (1) determination of time-varying precipitation from a field chloride profile and (2) evaluation of transient changes in water extraction by evapotranspiration and transient recharge associated with a change in land use.

Timing and processes of deglaciation along the southern margin of the Cordilleran ice sheet

Chapter

Full-text available

Jan 1987

Derek B. Booth

The northwestern U.S. during deglaciation; vegetation history and paleoclimatic implication

Chapter

Jan 1987

Geochemical Estimates of Paleorecharge in the Pasco Basin: Evaluation of the Chloride Mass Balance Technique

Article

Apr 1996

The Pasco Basin in southeastern Washington State provides a unique hydrogeologic setting for evaluating the chloride mass balance technique for estimating recharge. This basin was affected by late Pleistocene catastrophic floods when glacial dams in western Montana and northern Idaho were breached. It is estimated that multiple Missoula floods occurred between -13,000 and 15,000 years B.P. and reached a high water elevation of -350 m. These floods removed accumulated chloride from the sediment profile, effectively resetting the chloride mass balance clock at the beginning of the Holocene. The rate of chloride accumulation qCl in the sediments was determined by two methods and compared. The first method measured q Cl by dividing the calculated natural fallout of 36 Cl by a measured ratio of 36 Cl/Cl in the pore water, while the second method used the total mass of chloride in the profile divided by the length of time that atmospheric chloride had accumulated since the last flood. Although the two methods are based on different approaches, they showed close agreement. In laboratory studies the sediment to water ratio for chloride extraction was sensitive to the grain size of the sediments; low extraction ratios in silt loam sediments led to significant underestimation of pore water chloride concentration. Br/Cl ratios were useful for distinguishing nonatmospheric (e.g., rock) sources of chloride. Field studies showed little spatial variability in estimated recharge at a given site within the basin but showed significant topographic control on recharge rates in this semiarid environment. An extension of the conventional chloride mass balance model was used to evaluate chloride profiles under transient, time-varying annual precipitation conditions. This model was inverted to determine the paleorecharge history for a given soil chloride profile, and the parameters of the root extraction model required to estimate paleoprecipitation

Vegetation and climate change in northwest America during the past 125 kyr

Article

Jul 1997
NATURE

Vegetation records spanning the past 21kyr in western North America display spatial patterns of change that reflect the influence of variations in the large-scale controls of climate. Among these controls are millennial-scale variations in the seasonal cycle of insolation and the size of the ice sheet, which affect regional climates directly through changes in temperature and net radiation, and indirectly by shifting atmospheric circulation. Longer vegetation records provide an opportunity to examine the regional response to different combinations of these large-scale controls, and whether non-climatic controls are important. But most of the longer North American records are of insufficient quality to allow a robust test, and the long European records are in regions where the vegetation response to climate is often difficult to separate from the response to ecological and anthropogenic controls. Here we present a 125-kyr record of vegetation and climate change for the forest/steppe border of the eastern Cascade Range, northwest America. Pollen data disclose alternations of forest and steppe that are consistent with variations in summer insolation and global ice-volume, and vegetational transitions correlate well with the marine isotope-stage boundaries. The close relationship between vegetation and climate beyond the Last Glacial Maximum provides evidence that climate variations are the primary cause of regional vegetation change on millennial timescales, and that non-climatic controls are secondary.

Biogenic sedimentation beneath the California Current System for the past 30 kyr and its paleoceanographic significance

Article

Apr 1997

A north-south transect of 17 cores was constructed along the eastern boundary of the California Current system from 33° to 42°N to investigate the changes in biogenic sedimentation over the past 30 kyr. Percentages and mass accumulation rates of CaCO3, Corg, and biogenic opal were assembled at 500 to 1000 years/sample to provide relatively high resolution. Time-space maps reveal a complex pattern of changes that do not follow a simple glacial-interglacial two-mode model. Biogenic sedimentation shows responses that are sometimes time-transgressive and sometimes coeval, and most of the responses show more consistency within a limited geographic area than any temporal consistency. Reconstructed conditions during late oxygen isotope stage 3 were more like early Holocene conditions than any other time during the last 30 kyr. Coastal upwelling and productivity during oxygen isotope stage 3 were relatively strong along the central California margin but were weak along the northern California margin. Precipitation increased during the last glacial interval in the central California region, and the waters of the southern California margin had relatively low productivity. Productivity on the southern Oregon margin was relatively low at the beginning of the last glacial interval, but by about 20 ka, productivity in this area significantly increased. This change suggests that the center of the divergence of the West Wind Drift shifted south at this time. The end of the last glacial interval was characterized by increased productivity in the southern California margin and increased upwelling along the central California margin but upwelling remained weak along the northern California margin. A sudden (

Li, P. and Adams, W. T.. Ring-wide patterns of allozyme variation in Douglas-fir (Pseudotsuga menziesii). Can J Forest Res, 19: 149-161

Article

Feb 2011
CAN J FOREST RES

Seeds from 104 geographical locations throughout the range of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were analyzed at 20 enzyme loci to determine patterns of genetic variation and to make phylogenetic inferences. On average, the populations were polymorphic at 37% of the loci (range 5.0–65.0). Mean expected heterozygosity was 0.137 (range 0.021–0.239). Of the total genie diversity (HT = 0.182) observed, 24% was due to differentiation among populations. One Mexican population was genetically distinct from the rest of the species, which suggests the possibility of additional Pseudotsuga species in Mexico. The rest of the populations clustered into two groups corresponding to the recognized coastal and interior varieties. In addition, the interior variety separated into northern and southern subgroups near 44° latitude. Transition zones between the varieties were found to be narrower and more abrupt than has been suggested previously. Populations within the coastal variety and the northern interior subgroup averaged higher expected heterozygosity than the southern interior subgroup, but in the southern interior subgroup, populations were much more highly differentiated. Allozyme variation followed a latitudinal cline in the interior variety, but only weak geographical patterning was observed in the coastal variety. In general, genetic diversity decreased towards the periphery of the species range. Range-wide patterns of allozyme variation were similar to those in terpene studies, with the major exception that the Sierra Nevada seed sources in this study were closely aligned with the coastal variety rather than with the interior variety. Range-wide patterns of genetic variation in Douglas-fir largely reflect the evolutionary history of the species as revealed by paleobotanical studies.

Paleoclimatic implications of middle Wisconsinan pollen and a paleosol from the Purcell Trench, south central British Columbia

Article

Feb 2011

A paleosol and organic-rich horizons occur in Bessette Sediments near Meadow Creek, south central British Columbia. The paleosol is at least 42 000 years old and formed on a paleoslope adjacent to some precursor to Meadow Creek. On higher parts of the paleoslope, the soil developed under locally dry conditions and influxes of eolian material; a regosol formed near the base of the paleoslope marginal to a floodplain. Pollen assemblages from the organic-rich horizons are grouped into two assemblage zones. MC 1, approximately 42 000 years old, is dominated by arboreal pollen, mainly Picea. MC 2 (approximately 34 000 years old) is dominated by Picea in conjunction with significant amounts of Tsuga heterophylla. Paleoclimatic implications of the assemblages are that temperatures 42 000 years ago were approximately 3 °C cooler than present but by 34 000 years ago had ameliorated and were similar to or slightly cooler than present.

History of aridland vegetation and climate: a global perspective

Article

Jan 2008
BIOL REV

GURDIP SINGH

1. The origin and history of aridlands and their vegetational cover is closely related to geological history, especially in relation to plate tectonics, mountain building, land-and sea-level changes and ice ages, and the arrival of modern humans and their subsequent development. 2. A close relationship exists between world temperatures and precipitation. Therefore, the development of present-day zonal, aridland vegetation and climate cannot be divorced from the history of the latest ice age. 3. The combined geological and palaeobotanical evidence demonstrate that whilst the origin of modern openland and aridland vegetation went back to the time of the origin of angiosperms during the Cretaceous, its subsequent expansion went hand in hand with the lowering of world temperatures during the Palaeogene and Neogene, when a series of angiospermous families having dominantly herbaceous and openland taxa, as members, appeared successively in the stratigraphic record. 4. The successive lowering of world temperatures had the overall effect of reducing precipitation levels all over the globe. Consequently, high rainfall areas, bearing closed forests, became progressively smaller and smaller and the decreased rainfall promoted the evolution and expansion of low biomass, openland and aridland vegetation. 5. The break-up of regional closed forests had started from the middle Miocene but the main expansion of zonal, aridland vegetation, in low and middle latitudes, appears to have taken place, together with the expansion of tundra vegetation, at high latitudes, from the late Pliocene. Glaciations of a magnitude of at least two-thirds that of the late Pleistocene glacial maxima started to occur about that time, 25 Ma ago. 6. The alternations between cold, glacial and warm, interglacial periods, during the late Neogene, especially with increased amplitude during the last 0.4 Ma, allowed less and less time for forest vegetation to expand and stabilize during the warm intervals, with the result that openland and aridland vegetation was able to expand to unprecedented levels. 7. Further, as man increased fire frequencies during the late Pleistocene, the relatively fire-sensitive and mesophytic taxa were selectively eliminated and more and more forests were opened to invasion by openland taxa in low and middle latitudes. Later on, with the clearance of forests for agriculture, the overall effect on vegetation was to create open landscapes which favoured the expansion of openland taxa at low, middle and high latitudes, during an interglacial, that is, the Holocene, a feature that is unprecedented in the entire earlier geological record.

Historical Changes in Ponderosa Pine Forests Since Euro‐American Settlement

Article

Jun 2008
Ecosys Health

David J. Rapport

Most ecosystems require periodic disturbances to maintain their integrity, and human modification of natural disturbance regimes (e.g. fire frequency) often leads to deleterious changes. Ponderosa pine (Pinus ponderosa P. & C. Lawson) forests in the western United States are selected as examples. They were maintained in an open, park-like condition because of frequent low-intensity disturbances: fires and/or pest outbreaks. Fires enhanced grass cover, helped to reduce the buildup of organic matter, eliminated weak trees, and controlled pests. Euro-American settlement changed this balance by allowing heavy livestock grazing, which caused damage to the grass cover and contributed to soil erosion and depletion of the nutrient pool. Later, the policy of fire suppression promoted the establishment of a greater density of ponderosa pine and understory thickets at the expense of the grasses and caused excessive accumulation of coarse organic matter. Productivity of the forest subsequently declined and the thickets stagnated. Today, even unlogged ponderosa pine forests exhibit profound signs of stress: slow production and growth, decreased rate of nutrient cycling, simplified vertical and horizontal structure, and increased extent of disease. Some ecosystem services, such as the provision of soil and water quality, high biodiversity, and aesthetic value, are impaired.

Paleoseismicity, Ecological Change, and Prehistoric Exploitation of Anadromous Fishes in the Salmon River Basin, Western Idaho, USA

Article

Full-text available

Jul 2007

Loren G. Davis

By the middle Holocene, Native American groups developed semi-sedentary villages in the Columbia River basin of the Pacific Northwest. The economic basis for these villages is thought to have been predicated on the acquisition of bulk food resources, such as salmon and camas, for delayed consumption during the winter. In Idaho's lower Salmon River canyon, semi-sedentary pit house villages are absent until after 2000 14 C yr BP. Floodplain geochronol-ogy shows channel incision and terrace formation occurred at ca. 2000 14 C yr BP, caused by fluvial response to neotectonic displacement along a normal fault. The delayed appearance of pit house sites and other markers of the Winter Village Pattern in the canyon is argued to be directly related to neotectonically-induced changes in fluvial conditions after 2000 14 C yr BP, which significantly improved aquatic habitats for anadromous fishes and led to the development of a predictable, productive salmon fishery.

Climate change and impacts in southern British Columbia-a palaeoenvironmental perspective

Article

Full-text available

Sep 1996

Biomes of western North America at 18,000, 6000 and 0 C-14 yr BP reconstructed from pollen and packrat midden data

Article

May 2000
J BIOGEOGR

A new compilation of pollen and packrat midden data from western North America provides a refined reconstruction of the composition and distribution of biomes in western North America for today and for 6000 and 18,000 radiocarbon years before present ( ¹⁴ C yr bp ). Modern biomes in western North America are adequately portrayed by pollen assemblages from lakes and bogs. Forest biomes in western North America share many taxa in their pollen spectra and it can be difficult to discriminate among these biomes. Plant macrofossils from packrat middens provide reliable identification of modern biomes from arid and semiarid regions, and this may also be true in similar environments in other parts of the world. However, a weighting factor for trees and shrubs must be used to reliably reconstruct modern biomes from plant macrofossils. A new biome, open conifer woodland, which includes eurythermic conifers and steppe plants, was defined to categorize much of the current and past vegetation of the semiarid interior of western North America. At 6000 ¹⁴ C yr bp , the forest biomes of the coastal Pacific North‐west and the desert biomes of the South‐west were in near‐modern positions. Biomes in the interior Pacific North‐west differed from those of today in that taiga prevailed in modern cool/cold mixed forests. Steppe was present in areas occupied today by open conifer woodland in the northern Great Basin, while in the central and southern Rocky Mountains forests grew where steppe grows today. During the mid‐Holocene, cool conifer forests were expanded in the Rocky Mountains (relative to today) but contracted in the Sierra Nevada. These differences from the forests of today imply different climatic histories in these two regions between 6000 ¹⁴ C yr bp and today. At 18,000 ¹⁴ C yr bp , deserts were absent from the South‐west and the coverage of open conifer woodland was greatly expanded relative to today. Steppe and tundra were present in much of the region now covered by forests in the Pacific North‐west.

Late-glacial vegetation and environment on the eastern slope foothills of the Rocky Mountains, Alberta, Canada

Article

Jan 1996

Carole A. Mandryk

Stratigraphic pollen analysis done on sediment cores from two sites in the upper North Saskatchewan drainage basin of the eastern slopes foothills of the Rocky Mountains in west central Alberta, Canada combined with sedimentological data provide a local vegetational and environmental history. Radiocarbon AMS dates provide a chronology back to 17960 BP. Reconstruction and interpretation of the local pollen zones includes reevaluation of steppe and grassland as analogs for full- and late-glacial vegetation. Regional vegetation from c. 17960 to 16 100 BP is interpreted as an extremely cold semi-arid Artemisia steppe, the vegetation c. 16 100 to 11 900 BP as an Artemisia-Betula shrubland, and the vegetation c. 11 900–10 200 BP as a Picea woodland, in an environment characterized by consistently arid and windy conditions. This reconstruction emphasizes the significance of aridity, as opposed to simply low temperatures, as the critical factor in determining the late Quaternary vegetation of Alberta.

Late Pleistocene mammalian extinctions in North America: Taxonomy, chronology, and explanations

Article

Full-text available

Sep 1991

Donald Grayson

Toward the end of the Pleistocene, North America lost some 35 genera of mammals. It has long been assumed that all or virtually all of the extinctions occurred between 12,000 and 10,000 years ago, but detailed analyses of the radiocarbon chronology provide little support for this assumption, which seems to have been widely accepted because of the kinds of explanations felt most likely to account for the extinctions in the first place. Approaches that attribute the losses to human predation depend almost entirely on the assumed synchroneity between the extinctions and the onset of large mammal hunting by North American peoples. The fact that only two of the extinct genera have been found in a convincing kill context presents an overwhelming problem for this approach. Climatic models, on the other hand, are becoming increasingly precise and account for a wide variety of apparently synchronous biogeographic events. While a role for human activities in the extinction of some taxa is fully possible, there can be little doubt that the underlying cause of the extinctions lies in massive climatic change.

Global climatic changes since the last glacial maximum: Evidence from paleolimnology and paleoclimate modeling

Article

Mar 1996

H. E. Wright

Recognition that Earth/Sun orbital changes are the basic cause for Quaternary climatic variations provides a context for explaining global environmental changes, many of which are preserved in the stratigraphic and geomorphic record of lakes. Paleoclimatic numerical models suggest the mechanisms. In subtropical latitudes such as North Africa the enhanced summer insolation culminating about 10 000 years ago resulted in the increased monsoonal rains that explain the widespread expansion of lakes in now-desert basins. But in the American Southwest lake expansion dates to 18 000–15 000 years ago, when storm tracks were displaced to the south by the ice sheets—themselves a product of earlier orbital changes. The dynamics in the resopnse of different components of the natural system to climatic change are recorded in the stratigraphy of lake sediments, not only by their pollen content as a manifestation of the regional vegetation but also by their microfossils and chemical composition as reflections of lake development.

Population growth, climatic cooling, and the development of collector strategies on the Southern Plateau, Western North America

Article

Jan 1995

James C. Chatters

A change in human adaptations on the Southern Plateau during the fourth millennium B.P offers the opportunity to investigate the process by which immediate-consumption strategies are replaced by delayed consumption strategies among hunter-gatherers. Assemblage structure and settlement pattern are used to infer the nature of resource acquisition strategies between 2000 and 6000 radiocarbon years B.P., and the results are compared with a proxy record of population and a detailed reconstruction of terrestrial and riverine paleoenvironments. Results show that a strategy of mobile and later occasionally sedentary foraging with little use of storage technology persisted until as late as 3500 B.P and was abruptly and without detectable gradation replaced by a strictly scheduled, semisedentary, logistically organized, storage-dependent collector strategy. The change took place at a time of depressed population and 400 years after a period of climatic cooling had begun, thus eliminating both demographic pressure and environmental determinism as explanations. The evidence could be explained by prolonged selective pressure of an increasingly seasonal environment acting on successively attempted behavioral variants, but the widespread rise of collector-like strategies throughout the west at about the same time leaves open the question of exogenous development and highlights the importance of climatic change.

Postglacial Vegetation and Climate in the Northwestern Great Plains of Montana

Article

Jan 1989

Cathy Whitlock

Two pollen records from the northern Great Plains of Montana portray vegetational and climatic changes during the last 12,200 yr in a region where few other data are available. A 6.4-m core from Guardipee Lake, east of the Rocky Mountains in the area formerly covered by the Two Medicine glacial lobe, contains the Glacier Peak G and Mt. St. Helens Jy volcanic ashes. Pollen percentage data are dominated by Pinus, Poaceae, Artemisia, and Chenopodiaceae/Amaranthaceae. High nonarboreal percentages and small amounts of Juniperus, Alnus, Salix, and Populus pollen in sediments deposited between ca. 12,200 and ca. 9300 yr B.P. suggest a temperate grassland with shrubs growing locally in mesic settings. After ca. 9300 yr B.P. an increase in Chenopodiaceae/Amaranthaceae pollen and a concomitant decline in Artemisia indicate the development of more xerophytic grassland and the beginning of the altithermal period. The lake probably was intermittently dry thoughout the Holocene. A high sedimentation rate and the presence of cereal taxa characterize the last ca. 100 yr of Euroamerican settlement. Lost Lake at the northern margin of the Highwood Mountains yielded a 16.94-m core with no volcanic ashes that spans the last 9400 yr. High amounts of Chenopodiaceae/Amaranthaceae, Artemisia, and Poaceae pollen, from ca. 9400 to ca. 6000 yr B.P., suggest the presence of xeric grassland and a climate drier than at present. After ca. 6000 yr B.P. Chenopodiaceae/Amaranthaceae values declined and Artemisia, Poaceae, Pinus, Picea, Salix, Alnus, and Betula increased. The inferred spread of shrubs in wet habitats at this time and the expansion of forest in nearby mountain ranges indicate the end of the altithermal period and the onset of cooler/moister conditions.

Late Quaternary environmental change in the Lake O'Hara region, Yoho National Park, British Columbia

Article

Dec 1989
PALAEOGEOGR PALAEOCL

Palaeoenvironmental reconstructions for the upper Cataract Brook Valley are derived from radiocarbon and tephra dated cores recovered from subalpine Lake O'Hara and alpine Opabin Lake located near the Continental Divide in the central Canadian Rocky Mountains. Late Quaternary vegetational and climatic changes are based on pollen and macrofossil data and are supplemented by preliminary diatom data.The postglacial colonizing vegetation prior to ca. 10,100 yr B.P. at Lake O'Hara and before ca. 8530 yr B.P. at Opabin Lake was a shrub herb community dominated by Artemisia, Gramineae and Alnus. Pioneering forests at both sites were composed of Pinus cf. albicaulis/flexilis and Abies with lesser abundances of Picea and Pinus cf. contorta. Timberline remained above the elevation of Opabin Lake, at least 90 m above modern timberline elevation, during the period ca. 8500 yr B.P. to ca. 3000 yr B.P. in response to warmer climatic conditions associated with restricted glacial activity. Forest compositions resembling the modern subalpine Picea-Abies forest had developed by the end of this period. The period ca. 3000 yr B.P. to present was marked by deteriorating climatic conditions associated with renewed glacial activity in the Opabin Cirque and declining timberlines to below the elevation of Opabin Lake. Glacigenic sediments in the Opabin record from the post-Bridge River (ca. 2350 yr B.P.) interval are associated with reduced diatom production and a change in dominant diatom taxa to those characteristic of turbid water conditions and unstable catchment areas.

Coastal rainforest connections disclosed through a Late Quaternary vegetation, climate, and fire history investigation from the Mountain Hemlock Zone on southern Vancouver Island, British Colombia, Canada

Article

Mar 2003
REV PALAEOBOT PALYNO

The post-glacial vegetation and fire history of high-elevation regions on southern Vancouver Island is described using palynological and charcoal records from Porphyry and Walker lakes. A zone consisting mainly of Artemisia, Poaceae, and ferns occurs in the basal clay at Porphyry Lake and may represent a non-arboreal ecosystem in a late-Wisconsin glacial refugium. At both sites, a fire-free Pinus contorta zone occurs before ca 14 160 calendar years before present (cal BP). Climate at this time is interpreted as being cool to cold and dry. Mixed conifer forests of Picea, Abies, Tsuga mertensiana and Pinus contorta replaced the Pinus contorta woodlands after ca 14 160 cal BP. Fires are recorded for the first time. Climate is interpreted as cool and moist. Forests of Abies, Picea, Tsuga heterophylla, Pseudotsuga menziesii, and Alnus developed and expanded during the early-Holocene from ca 11 400–9910 to 7700–7300 cal BP as climate warmed and dried. Charcoal increased during this interval, indicating only slightly more fire activity and reflecting continued moist conditions at high elevations. In the mid-Holocene from ca 7700–7300 to 5200–4900 cal BP, Tsuga heterophylla pollen values increased as forests became dominated by Tsuga heterophylla, Picea, and Abies with Alnus in response to increased moisture. The increase in charcoal influx at this time may reflect an increase in slope wash and erosion resulting from a wetter climate rather than an increase in fire incidence. Starting at ca 5200–4900 cal BP, a further increase in Tsuga heterophylla combined with an increase in Tsuga mertensiana and Cupressaceae pollen suggest that the late-Holocene was characterised by increasing moisture and decreasing temperatures. Late-Holocene forests consisted predominately of Tsuga heterophylla, Tsuga mertensiana, Cupressaceae, and Pinus contorta. A slight reduction in charcoal influx at ca 4600 cal BP implies fewer fires. A recent increase in charcoal at Walker Lake at 1700 cal BP may reflect anthropogenic burning. The timing of events and response of taxa on southern Vancouver Island are comparable to other coastal sites in northwestern North America, suggesting that past ecosystems were widespread and contemporaneous. Palaeoecosystem changes detected in one region of the Pacific Northwest likely reflect a widepsread response to climate throughout the ∼2500 km long zone, a zone that today is home to half of the world’s remaining coastal temperate rainforest.

Smith Canyon dune field, Washington, U.S.A: Relation to glacial outburst floods, the Mazama eruption, and Holocene paleoclimate

Article

Apr 2001

Sedimentary deposits from the Smith Canyon dune field, south-central Columbia Basin, Washington, U.S.A. document climatically-influenced Late Pleistocene and Holocene aeolian and fluvial deposition in a region impacted by glacial outburst floods and tephra falls. The depositional history is summarized by five environmentally distinctive and climatically sensitive sedimentary units (temporal limits estimated): Unit 1 (c. 15·5–8 ka), pedogenically altered glacial outburst flood and minor aeolian silt and clay; Unit 2 (c. 8–6·9 ka), fluvial and minor aeolian sand; Unit 3 (c. 6·9–6·8 ka), flood-induced fluvial sand with gravel-sized tephra clasts; Unit 4 (c. 6·8–3·9 ka), aeolian dune sand; Unit 5 (c. 3·9 ka to present), pedogenically altered, stabilized dune sand. Estimated age ranges are based on stratigraphic position, tephrochronology, and correlation with temporally constrained strata from elsewhere in the region.

Quaternary temperatures and precipitation for the north-west coast of North America

Article

Full-text available

Aug 1980

Palynologists utilize present-day pollen rain to interpret the climatic setting of pollen records from Quaternary deposits. Analogues are sought which relate the present with the past. Because climatic conditions at mid-latitudes during the Quaternary were diverse, often ranging from a tundra type at one extreme to a closed forest type at the other, a modern data set should cover the extremes of vegetation and climate expected during this time. For interpreting climatic parameters from Quaternary pollen in land and marine cores, we calculated a pair of regression equations relating modern pollen rain from the Pacific coastal forest and tundra to mean July temperature and mean annual precipitation at a series of sites from the Aleutian Islands to northern California. We describe here how application of these equations to Quaternary pollen profiles from western Washington enabled us to quantify temperature and precipitation over the past ~80,000 yr.

Holocene glaciation in the mountain ranges of the western United States.

Article

Jan 1984

Where absolute dating control is available, there is usually depositional evidence for glacial activity during the early Holocene and multiple advances during the Neoglacial. A comparison of relative-dating data between chronosequences with absolute dating and those without absolute dating allows for an extension of age control into areas where radiocarbon dates are not available. In at least one area, the Front Range of Colorado, a middle-altithermal glacial advance has been documented, and we are cautioned against assuming a synchroneity of Holocene glacial activity. -from Authors

Pumice and other pyroclastic deposits in Mount Rainier National Park, Washington

Article

Jan 1974

D.R. Mullineaux

Paleoecology in the Pacific Northwest I. Late Quaternary vegetation and climate

Article

Jan 1981

Vegetation of eastern Siberia during the Anthropogene Period

Article

Jan 1967

Palynological investigations in western Iran

Article

Jan 1977

The Cordilleran ice sheet in Washington, Idaho, and Montana.

Article

Jan 1983

During the Fraser (Late Wisconsin) Glaciation, the Cordilleran ice sheet advanced southward from source areas in British Columbia and terminated in the United States between the Pacific Ocean and the Continental Divide. The ice sheet extended farthest along major south-trending valleys and lowlands that traverse the international boundary; it formed several composite lobes segregated by highlands and mountain ranges. Each lobe dammed sizable lakes that drained generally southward or westward along ice margins and across divides. Field evidence warrants considerable revision of the ice margin in northern Idaho and northeastern Washington. -from Authors

Mid-Wisconsinan climates of the Pacific Northwest

Article

Jan 1978

John J. Clague

Calibration of absolute pollen influx

Chapter

Jan 1973

Modern pollen spectra from the Columbia Basin, Washington

Article

Jan 1974
NORTHWEST SCI

Stratigraphy and Palynology of Late Quaternary Sediments in the Puget Lowland, Washington

Article

Apr 1974

Paleoclimatic fluctuations from 50,000 yr BP to the present are recorded in pollen assemblages from buried Pleistocene peat and in postglacial bogs in the Puget Lowland of Washington. Two peat beds in Possession Drift, radiocarbon-dated at 47,600 + 3.300/- 1,800 and 34,900 + 3,000/- 2,000 yr B.P., contain high percentages of pine with minor spruce, fir, and western red cedar. Significant representation of total NAP suggests an open landscape dominated by herbs, with intermittent patches of lodgepole pine, characteristic of a cool climate and unstable physiographic conditions. The nonglacial interval immediately preceding the last glacial advance was originally defined as the Olympia Interglaciation, but new radiocarbon and palynological evidence now suggest that it should be considered to be a nonglacial interval of less than interglacial rank. Olympia peat beds yielded radiocarbon dates of 22,700 ± 550, 22,700 ± 600, 24,800 ± 600, 26,850 ± 1,700, 27,200 ± 1,000, and 27,600 ± 1,000 yr B.P. Pine maintains a dominant role throughout the units, although spruce, mountain hemlock, and total NAP increase in the younger units, suggesting a trend toward a cooler climate. Pollen from sediments of the Everson Interstade of the Fraser Glaciation is dominated by lodgepole pine, suggesting that the environment was characterized by extreme edaphic disturbance and severe climatic conditions. Postglacial bogs show a lower pine-Douglas fir zone and an upper western red cedar-western hemlock zone, separated by an ash younger than 7,140 ± 600 yr B.P. The Hypsithermal is marked by high pollen values for Douglas fir about 7,000 yr ago, followed by increased western red cedar and western hemlock, implying a moister, cooler climate.

Late Quaternary Pollen Record from Big Meadow, Pend Oreille County, Washington

Article

Aug 1978

The pollen record at Big Meadow in northeastern Washington contains at least 5 pollen zones spanning ca. the last 12,500 yr. Initial vegetation after Pinedale deglaciation was nonarboreal. Estimates of the pollen influx and the dominance of Artemisia and Gramineae plus comparatively little pine pollen suggest a tundra—like landscape from the time of deglaciation until ca. 9,700 BP. Zone II probably lies disconformably atop this earliest zone and reveals a community dominated first by grasses plus diploxylon pines and later by diploxylon pines without prominent grasses (Zone III) between 9,700 and 3,300 BP. zone IV demarcates a short reversal of climatic conditions in which Picea and Abies are relatively prominent. Tsuga heterophylla, the present day climatic climax dominant of the area, rapidly emerged in the pollen record at ca. 2,400 BP. See full-text article at JSTOR

Pollen Sequence from the Columbia Basin, Washington: Reappraisal of Postglacial Vegetation

Article

Apr 1976

During the early postglacial time of eastern Washington (10,000 to 18,000 years B.P.) treeless vegetation dominated by Artemisia may have occupied extensive areas of stony patterned ground, while conifers (haploxylon pine with Abies and Picea) were restricted to nearby loess hills. Decrease in Artemisia, Abies and Picea, suggesting a warming trend, began over 9000 14C years ago and coincided with a marked increase in diploxylon pine.

East Beringia during Late Wisconsin time: a review of the biotic evidence

Chapter

Dec 1982

J. V. Matthews Jr

The nature of the late Pleistocene environment of Beringia is a topic of current debate. Some have concluded that it was a large arctic-steppe biome which supported an ungulate fauna as diverse as that of certain temperate grasslands. Others argue that the late Wisconsin vegetation of much of East Beringia was similar to present arctic and alpine fell field. They claim that the evidence for either large numbers or diversity of ungulates during late Wisconsin time is deficient or nonexistent. Although comparisons with the fauna of the African plains are inappropriate, several lines of evidence do show that the number of large-mammal species existing together in East Beringia during the late Pleistocene was several times larger than that of the existing tundra fauna. Prominent were Mammuthus primigenius, Bison priscus, Equus, several types of musk ox, and Rangifer. In spite of the apparent low pollen production in late Pleistocene plant communities, sufficient forage must have existed to support this unique ungulate community. Herb-dominated pollen spectra representing the height of the late Wisconsin have attributes, such as high percentages of Artemisia and dominance of grass over sedge, that set them apart from the majority of lowland tundra surface samples; consequently, these herb-zone fossil spectra are thought to indicate an environment different from that of present tundra. Macrofossils of plants and insects add dimension to this picture. They show that late Pleistocene treeless environments contained species and probably whole communities not found in East Beringia today. Many of the plant and insect fossils imply prevalence of steppe-like conditions. When all evidence pertaining to Beringian environments is collated, the most probable reconstruction is of a treeless region composed of a mosaic of communities, among which were large tracts that can only be termed steppe-like. It is probable that both alpine fell field and some of the rare steppe sites in present day Alaska-Yukon harbor species which formerly occupied these steppe areas. The late Wisconsin has been viewed as the last time when presently disjunct steppe species in the U.S.S.R. and East Beringia had continuous ranges. But if the land bridge itself acted to promote increased continentality in Beringia, then the exchange of steppe taxa may have occurred during the mid-Wisconsin or even earlier. Certainly, it is becoming clearer that the land bridge acted as a filter for certain steppe organisms during late Wisconsin time.

Holocene Volcanism in the Coterminous United States and the Role of Silicic Volcanic Ash Layers in Correlation of Latest-Pleistocene and Holocene Deposits

Chapter

Jan 1983

Holocene volcanism in the conterminous US is restricted to the W states. Volcanism in the Cascade Range tectonic province is probably a result of crustal-plate convergence and subduction of the oceanic Juan de Fuca plate beneath the North American continent; volcanism in the other 3 provinces (the periphery of the Basin and Range province, the periphery of the Rio Grande rift, and the Salton Trough) is probably a consequence of crustal spreading. The spatial distribution of Holocene volcanism roughly coincides with that of heat flow and hydrothermal activity; all 3 of these phenomena reflect the outward transfer of heat from within the Earth. Major silicic volcanism during Holocene time has taken place in two major areas; the Cascade Range of the Pacific NW and the Mono and Inyo Craters of E-central California. Explosive eruptions of silicic tephra layers that provide age calibration for various geologic studies are summarised here. Suggestions for further work and its importance are made.-after Authors

Postglacial forest succession, climate and chronology in the Pacific North West

Article

Jan 1947
Trans Am Phil Soc

H. P. Hansen

Early Holocene glacier advance in the North Cascade Range, Washington

Article

Sep 1981
GEOLOGY

James E. Beget

Moraines and glacial drift of the White Chuck advance were deposited in early Holocene time in cirques near Glacier Peak, Washington. These sediments overlie Glacier Peak tephra, including layers G, N, F, C, M, T, and B, which were erupted between about 12,500 and 11,250 yr B.P. White Chuck drift is overlain by Mazama tephra layer O, deposited about 6,700 yr B.P. Charcoal collected from till deposited during the White Chuck advance is about 8,300 to 8,400 radiocarbon years old, indicating that the glacial advance that deposited the till occurred about this time and that a previously unrecognized period of cooling and/or increased precipitation of sufficient intensity to produce glacial advances comparable to or greater than those of the recent Little Ice Age occurred in early Holocene time in the North Cascade Range. Other pre-Altithermal moraines from the Cascades, the Rocky Mountains, Laurentide Canada, and Baffin Island may have been produced during this cool period.

Late Pleistocene Stratigraphy and Chronology in Southwestern British Columbia and Northwestern Washington

Article

Jan 1965

Six geologic-climate units are proposed for the late Pleistocene sequence in southwestern British Columbia and northwestern Washington. They include two major units, the Olympia Interglaciation and the Fraser Glaciation, and four subdivisions of the latter - the Evans Creek, Vashon, and Sumas Stades, and the Everson Interstade. The Olympia Interglaciation is a nonglacial episode that started at least 36,000 years B.P. and continued until the advance of Cordilleran glacier ice during the Fraser Glaciation. During the Evans Creek Stade, alpine glaciers formed in the mountains of western Washington and British Columbia while nonglacial sediments were still being deposited in the southern Puget Lowland. Further growth of glaciers in British Columbia resulted in the formation of the Cordilleran ice sheet. This ice entered the northern end of the area after 25,000 years B.P. but did not reach the southern end until after 15,000 years B.P. The Vashon Stade of the Fraser Glaciation began with this advance of Cordilleran ice into the lowlands. It ended with the beginning of marine and glaciomarine conditions there, which commenced in the southern Puget Lowland about 13,500 years B.P. and in the Strait of Georgia about 13,000 years B.P. The episode represented by the marine conditions is called the Everson Interstade and lasted about 2000 years, during which the sea contained much floating ice. The Interstade ended when the land rose with respect to the sea level forcing withdrawal of the sea and the disappearance of floating ice in most of northwestern Washington and southwestern British Columbia; in the eastern part of the Fraser Lowland this event coincided with the advance of a valley glacier during the Sumas Stade.

Evidence of Multiple Late-Wisconsin Floods from Glacial Lake Missoula in Badger Coulee, Washington

Article

Jul 1982

Russell C. Bunker

Catastrophic floods from glacial Lake Missoula entered the Pasco Basin in south-central Washington and backflooded its marginal valleys. Badger Coulee, one such valley, contains beds of fine-grained slackwater sediment deposited by these floods. The slackwater sediment contains two ash layers of the Mount St. Helens set S tephra, about 13,000 yr old. The ash was deposited on a ground surface developed atop slackwater sediment deposited during preash flooding. Evidence of the former ground surface includes the reworked ash, inferred trace fossils, stream and debris-flow deposits, slopewash and/or eolian sediment, and colluvium at the ash horizon. These features and the ash were buried by slackwater sediment deposited during postash flooding. Nonflood, subaerial deposits are not present atop other beds. Instead, beds commonly are reversely graded across “contacts,” suggesting that multiple beds were continuously deposited. The exposed beds thus record at least two late-Wisconsin floods, one preash, the other postash. The pre- and postash floods may be correlative with earlier-reported floods thought to have occurred 17,500-14,000 and 14,000–13,000 yr B.P., respectively.

Two major Wisconsin lithostratigraphic units in southwest British Columbia

Article

Jul 1977
CAN J EARTH SCI

Two lithostratigraphic units, Quadra Sand and the Cowichan Head Formation, are overlain by Vashon till and associated glacial sediments and underlain by Dashwood and Semiahmoo drift deposits in coastal southwest British Columbia. Each unit is formally described and stratotypes are presented. Quadra Sand consists of cross-stratified, well-sorted sand, minor gravel, and silt deposited as outwash in front of glaciers advancing into the Georgia Depression at the beginning of the Fraser Glaciation. It is diachronous, deposition having commenced earlier than 29,000 years BP at the north end of the Georgia Depression but not until after 15,000 years BP at the south end of the Puget Lowland. The Cowichan Head Formation, deposited during the Olympia nonglacial interval, underlies Quadra Sand and consists of parallel-bedded silt, sand, and gravel, in part plant-bearing. The unit is divisible into a lower marine member and an upper fluvial and estuarine member.

Late Wisconsin Mountain Glaciation in the Western United States

Article

Jan 1983

Evidence of repeated fluctuations of alpine glaciers during the late Quaternary is found in numerous high-mountain regions of the western United States, Alaska, and Hawaii. Today, about 500 km2 of glacier cover exists in the western United States and about 73 0002 exists in Alaska; during the maximum of the last glaciation, these regions contained about 100 000 km2 and 630 000 km2 of glacier ice, representing a twentyfold and sixfold increase, respectively. In Hawaii, a small ice cap (70 km2) formed at the summit of Mauna Kea volcano. A chronology of glacier fluctuations is slowly developing for these different glaciated regions. During the maximum ice advances of the last glaciation, equilibrium-line altitudes of glaciers were some 850 to 900 m lower than they are at present in the Cascade Range and about 1000 m lower in the Rocky Mountains but probably were depressed no more than about half that amount in the Brooks Range of Arctic Alaska. -from Authors

Late Quaternary Vegetation History at Waits Lake, Colville River Valley, Washington

Article

Dec 1978
Bot Gaz

A 10.6-m section of mostly calcareous sediments at Waits Lake, Washington, reveals a multizoned history of vegetation change since recession of Pinedale (P-2) glacial ice from the Colville River Valley. The oldest unit with high percentages of Artemisia, Gramineae, and Shepherdia canadensis-type pollen characterizes vegetation in which trees were not major components and the climate was cooler and moister than today. Pollen Zone II (ca. 10,000-6,700 yr before present [BP]) records a warmer period in which diploxylon pine was prominent. Concomitant with the Mazama ash fall (6,700 yr BP), Artemisia became particularly prominent (Pollen Zone II); but by about 5,000 yr BP, diploxylon pine was conspicuous. This comparatively short-term vegetation change probably indicates the advance of drought-tolerant Artemisia-dominated steppe northward in the Colville River Valley. The modern climax vegetation in the vicinity of Waits Lake (Pseudotsuga-dominated forest) appears to have emerged around 2,300 yr BP, although more detailed documentation of this event is hampered by the low pollen production of Pseudotsuga menziesii. The 14C dates from these calcareous sediments were corrected through use of the Mazama and Glacier Peak ash layers as time-stratigraphic marker horizons.

About Forty Last-Glacial Lake Missoula Jökulhlaups through Southern Washington

Article

Nov 1980

Richard B. Waitt

The rhythmic Touchet Beds in the Walla Walla and lower Yakima valleys resulted from many separate backfloodings by hydraulically ponded glacial Lake Missoula water. At least once this episodic lake briefly contained half the 2130km3 of water that catastrophically drained the largest glacial Lake Missoula. The lack of weathering or soil within the Touchet Beds suggests that all rhythmites are late Wisconsin. Bottom sediment of glacial Lake Missoula in Montana consists of rhythmites each interpreted as the record of a gradually deepening lake. 40 superposed rhythmites record about 40 late-Wisconsin fillings and emptyings of glacial Lake Missoula. -from Author

Periglacial Wedges and the Late Pleistocene Environment of Wyoming's Intermontane Basins

Article

Mar 1981

Brainerd Mears

Nonsorted polygons in the uppermost 2 to 3 m beneath Pleistocene surfaces indicate permafrost at 1340 m and higher elevations in the intermontane and piedmont plains of Wyoming during the Wisconsin, and perhaps earlier, glacial maxima. The polygons, as much as 10 m in diameter, are delineated by wedges that vary in depths, range from narrow to moderately flared forms, and deform host materials. The wedges have silty fine-to-medium sand matrices (largely eolian) with pebbles or clasts from hosts of gravel or bedrock. Some wedges may reflect seasonal cracking in a periglacial active zone, but most are either permafrost sand-wedge relics or, less commonly, ice-wedge casts. Alternative explanations are rejected largely because similar features are apparently lacking in the lower and warmer plains from eastern Colorado southward. The wedges suggest an arid, windy, periglacial environment whose mean-annual temperatures are conservatively estimated as some 10° to 13°C colder than those at present. Although late Wisconsin-early Holocene floral and faunal evidence indicates lowered montane biotic zones, the eolian and periglacial features indicate a lack of extensive forest cover on the basin floors. In conjunction with vertebrate-fossil associations of grazing and tundra animals, the wedges may provide a parallel line of evidence for a former periglacial steppe, or “steppe-tundra”, in the Wyoming basins.

Late Quaternary Mammalian Zoogeography of Eastern Washington

Article

Nov 1983

The late Quaternary mammalian zoogeographic history of eastern Washington as revealed by archaeological and paleontological research conforms to a set of past environmental conditions inferred from botanical data. During the relatively cool and moist late Pleistocene and early Holocene, Cervus cf. elaphus, Ovis canadensis, Vulpes vulpes, Martes americana, Alopex lagopus, and perhaps Rangifer sp., taxa with ecological preferences for mesic steppe habitats, were present in the now xeric Columbia Basin. As the climate became progressively warmer and drier during the late Pleistocene and early Holocene, Antilocapra americana, Onychomys leucogaster, Spermophilus townsendii, and Neotoma cinerea, taxa with ecological preferences for xeric steppe habitats, appear in the Columbia Basin. Bison sp. and Taxidea taxus may have been present in eastern Washington for the last 20,000 yr. Middle and late Holocene records for Oreamnos americanus, Spermophilus columbianus, S. townsendii, Lagurus curtatus, and Urocyon cinereoargenteus in central eastern Washington suggest fluctuations in the ranges of these taxa that conform to a middle Holocene period of less effective precipitation and a ca. 3500-yr-old period of more effective precipitation before essentially modern environmental conditions prevailed.

Quaternary Palynology of the Pacific Slope of Washington

Article

Nov 1977

Calvin J. Heusser

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.

A Record of Late Quaternary Vegetation from Davis Lake, Southern Puget Lowland, Washington

Article

Sep 1981

Cathy Whitlock

Pollen and macrofossil analyses of a core spanning 26,000 yr from Davis Lake reveal late Pleistocene and Holocene vegetational patterns in the Puget Lowland. The core ranges lithologically from a basal inorganic clay to a detritus gyttja to an upper fibrous peat and includes eight tephra units. The late Pleistocene pollen sequence records two intervals of tundra-parkland vegetation. The earlier of these has high percentages of Picea, Gramineae, and Artemisia pollen and represents the vegetation during the Evans Creek Stade (Fraser Glaciation) (ca. 25,000–17,000 yr B.P.). The later parkland interval is dominated by Picea, Tsuga mertensiana, and Gramineae. It corresponds to the maximum ice advance in the Puget Lowland during the Vashon Stade (Fraser Glaciation) (ca. 14,000 yr B.P.). An increase in Pinus ontorta pollen between the two tundra-parkland intervals suggests a temporary rise in treeline during an unnamed interstade. After 13,500 yr B.P., a mixed woodland of subalpine and lowland conifers grew at Davis Lake during a period of rapid climatic amelioration. In the early Holocene, the prolonged expansion of Pseudotsuga and Alnus woodland suggests dry, temperate conditions similar to those of present rainshadow sites in the Puget Lowland. More-mesic forests of Tsuga eterophylla, Thuja plicata, and Pseudotsuga, similar to present lowland vegetation, appeared in the late Holocene (ca. 5500 yr B.P.).

Reexamination of Postglacial Vegetation History in Northern Idaho: Hager Pond, Bonner Co.

Article

Sep 1978

Hager Pond, a mire in northern Idaho, reveals at least five pollen zones since sediments formed after the last recession of continental ice (>9500 yr BP). Zone I (>9500-8300 yr BP) consists mainly of diploxylon pine, plus low percentages of Abies, Artemisia, and Picea. SEM examination of conifer pollen at selected levels in the zone reveals that Pinus albicaulis, P. monticola, and P. contorta are present in unknown proportions. The zone resembles modern pollen spectra from the Abies lasiocarpa-P. albicaulis association found locally today only at high elevation. Presence of whitebark pine indicates a cooler, moister climate than at present, but one which was rapidly replaced in Zone II (8300-7600 yr BP) by warmer, drier conditions as inferred by prominence of grass with diploxylon pine. Zone III (7600-3000 yr BP) was probably dominated by Pseudotsuga menziesii, plus diploxylon pine and prominent Artemisia and denotes a change in vegetation but continuation of the warmer drier conditions. Beginning at approximately 3000 yr BP Picea engelmannii, Abies lasiocarpa, and/or A. grandis and diploxylon pine were dominants and the inferred climate became cooler and moister concomitant with Neoglaciation. The modern climatic climax (Zone V), with Tsuga heterophylla as dominant, has emerged in approximately the last 1500 yr.

Regional Significance of an Early Holocene Moraine in Enchantment Lakes Basin, North Cascade Range, Washington

Article

Mar 1982

The upper Enchantment Lakes basin in the North Cascade Range of Washington displays two moraine belts, each recording an episode of glacier advance after the end of the last glaciation. The inner belt, the Brynhild, 0.1 to 0.5 km beyond existing glaciers, postdates Mount St. Helens Wn tephra (∼450 yr old), which lies only beyond the moraines. The morainal surface is only slightly weathered, is almost barren of lichens, and is devoid of soil, evidence suggesting that the Brynhild moraines are no more than a century old. The outer moraine, the Brisingamen, 0.3 to 0.7 km beyond existing glaciers, is weathered and is covered with large lichens. On and behind the Brisingamen moraine the Mazama ash (6900 yr old) is present beneath the Mount St. Helens Yn and Wn tephras. Despite more than 7 millennia of weathering, the rock surface behind the Brisingamen moraine is measurably less weathered than the surface beyond, which was last glaciated during the Rat Creek advance about 13,000 yr ago. The age of the Brisingamen moraine therefore is probably early Holocene. The Brisingamen moraine evidently correlates with moraines near Glacier Peak, near Mount Rainier, in northeastern and central Oregon, in the southern Canadian Rockies, and in the northern U.S. Rocky Mountains. These regional effects suggest that a climatic episode of cooling or increased snowfall affected the entire region some time during the early Holocene.

Holocene Vegetation History of the Okanogan Valley, Washington

Article

Sep 1979

Haploxylon pine(s) and Artemisia dominated the initial vegetation in front of the receding Okanogan Lobe until ca. 10,000 yr B.P., as revealed by two pollen records in north-central Washington. After 10,000 yr B.P. the macroclimate became warmer throughout the Okanogan drainage as diploxylon pines and Artemisia increased. The Mount Mazama eruption at ca. 6700 yr B.P. is recorded as two stratigraphically separate and petrographically distinct tephra units at Bonaparte Meadows. While there are apparent short-term changes in the vegetation coincident with the ashfall(s), Artemisia continues to dominate the Okanogan Valley until ca. 5000 yr B.P. By 4700 yr B.P. the modern vegetation, dominated by Pseudotsuga menziesii, had become established around Bonaparte Meadows.

Pollen accumulation rates at Rogers Lake, Connecticut, during late- and postglacial time

Article

Jun 1967
REV PALAEOBOT PALYNO

Margaret Bryan Davis

Pollen accumulation rates have been estimated by dividing the pollen number per unit volume in 1 ml samples from a core from Rogers Lake, Connecticut, by the number of years represented by each sample. The latter variable was estimated from 24 radiocarbon-dated levels within the core. The result shows that total pollen deposition rose steepy from 1,000 /cm² / year, 14,000 years ago to 10,000/cm²/year in later Late Glacial time, reaching a maximum of 40,000/cm²/year, 9,000 years ago when the Pine Pollen Zone (B) was deposited. Subsequently the deposition rate fall to 20,000–25,000/cm²/year, remaining stable at this level for the last 8,000 years.

Tephrochronology of Late Wisconsin Deglaciation and Holocene Glacier Fluctuations Near Glacier Peak, North Cascade Range, Washington

Article

May 1984

James E. Beget

Tephra layers near Glacier Peak in the North Cascade Range provide limiting dates for four periods of alpine glacier advance. Field relations suggest that late Wisconsin alpine glaciers last advanced prior to the eruption of tephra layers from Glacier Peak about 11,250 yr B.P. Late Wisconsin deglaciation in the central North Cascades was complete prior to the Glacier Peak tephra eruptions. Glaciers again expanded in the early Holocene about 8400 – 8300 yr B.P. Soil formed in alpine meadows during an episode of mild climate in the middle Holocene prior to at least two intervals of glacier expansion: an older episode between 5100 and 3400 yr B.P., and a younger episode within the last 1000 yr.

Key to the quaternary pollen and spores of the Great Lakes Region.

Article

John H. McAndrews

Quaternary geology of the Channeled Scabland and adjacent areas

Article

Feb 1978

V. R. Baker

The quaternary history of the channeled scabland is characterized by discrete episodes of catastrophic flooding and prolonged periods of loess accumulation and soil formation. The loess sequence was correlated with Richmond's Rocky Mountain glacial chronology. At least five major catastrophic flood events occurred in the general vicinity of the channeled scabland. The earliest episode occurred prior to the extensive deposition of the Palouse formation. The last major episode of flooding occurred between about 18,000 and 13,000 years ago. It probably consisted of two outbursts from glacial Lake Missoula.

Pollen and Lignin Records of Late Quaternary Vegetation, Lake Washington

Article

Jan 1983

Analyses of lignin oxidation products and pollen for an 11-meter core from Lake Washington provide independent but similar reconstructions of the late Quaternary vegetation in the Puget Lowland. An exception is in sediments of the late Pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region. This dissimilarity appears to result from different major provenances: eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the Lake Washington drainage basin.

Vegetation of the Earth and Eco-logical Systems of the Geo-biosphere

Jan 1979

Univ

Univ. of Minnesota Press, Minneapolis. Walter. H. (1979). " Vegetation of the Earth and Eco-logical Systems of the Geo-biosphere. " Springer-Verlag. New York.

Reconnaissance geologic map and cross sections of the southern Washington Cascade Range

Jan 1980

Hammond

Faunal Remains from the Marmes Rockshelter and Related Archeological Sites in the Columbia Basin

Jan 1972

Gustafson

Geology and water resources of Klickitat County

Jan 1979

Brown

The Palynology of Williams Lake Fen, Spokane County, Washington

Jan 1979

Nickmann

Late Quaternary Vegetation in the Southwestern Columbia Basin, Washington

Abstract

No full-text available

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