bluuebunny/crossref_metadata_2025 huggingface dataset:
Late Quaternary Vegetational Change in the Kotzebue Sound Area, Northwestern Alaska
Authors: Anderson Patricia M.
Published: December 2004

Two sediment cores from Kaiyak and Squirrel lakes in northwestern Alaska yielded pollen records that date to ca. 39,000 and 27,000 yr B.P., respectively. Between 39,000 and 14,000 yr B.P., the vegetation around these lakes was dominated by Gramineae and Cyperaceae with someSalixand possiblyBetula nana/glandulosaforming a local, shrub component of the vegetation.Betulapollen percentages increased about 14,000 yr B.P., indicating the presence of a birchdominated shrub tundra.Alnuspollen appeared at both sites between 9000 and 8000 yr B.P., andPiceapollen (mostlyP. mariana) arrived at Squirrel Lake about 5000 yr B.P. The current foresttundra mosaic around Squirrel Lake was established at this time, whereas shrub tundra existed near Kaiyak Lake throughout the Holocene. When compared to other pollen records from north-western North America, these cores (1) represent a meadow component of lowland. Beringian tundra between 39,000 and 14,000 yr B.P., (2) demonstrate an early Holocene arrival ofAlnusin northwestern Alaska that predates most otherAlnushorizons in northern Alaska or northwestern Canada, and (3) show an east-to-west migration ofPiceaacross northern Alaska from 9000 to 5000 yr B.P.
Age Profiles in Elephant and Mammoth Bone Assemblages
Authors: Haynes Gary
Published: December 2004

Age profiles of modern African elephant (Loxodonta africana) populations are significantly affected by drought conditions that cause local die-offs. Subadult animals die in proportions that may be nearly twice what is recorded in live populations. Such biasing of death sample age profiles might also have occurred during late Pleistocene die-offs of Mammuthus. This comparative study of modern and fossil proboscidean age structures supports a tentative interpretation that late Pleistocene extinction of Mammuthus (at least in the southwestern United States) resulted from severe drought conditions, at which Clovis hunters were witnesses, but not necessarily frequent participants.
Late Wisconsin Ice-Surface Profile Calculated from Esker Paths and Types, Katahdin Esker System, Maine
Authors: Shreve Ronald L.
Published: December 2004

Values of the gradient of the former ice surface can be inferred at points along a flow line from deviations of esker paths or transitions in esker type and numerically integrated to give the profile. A profile calculated in this way shows that during formation of the Katahdin esker system about 12,700 yr ago the ice thickness at distances of 10, 20, 50, 100, and 140 km from the terminus, which is about two thirds of the distance to the ice divide, was approximately 200, 300, 600, 750, and 900 m. The terminal reach was computed by assuming an unknown uniform basal drag and matching the profile to its known elevation at the terminus and known gradient 10 km upglacier. Correction for isostatic rebound based on the elevations of contemporaneous deltas and of the marine limit proved unnecessary, because the tilt due to the difference in uplift at the two ends of the profile is only 0.1 m km−1. With other plausible assumptions as to sea levels in the past, elevations of the marine limit, or exact location of the terminus the profile could be as much as roughly 100 m higher. It hits Mount Katahdin about 500 m below its summit, which is at 1600 m, in agreement with the geological evidence farther west. The steepening of the upper part of the profile suggests that the mountain dammed and diverted the ice. Basal drag computed from the profile varies from about 20 kPa (0.2 bar) near the terminus to 30 kPa (0.3 bar) at 100 km to 70 kPa (0.7 bar) at 140 km. The relatively low values away from the influence of Mount Katahdin agree with independent evidence from deep-sea cores of substantial late Wisconsin ice-sheet thinning without comparable areal reduction. The method has potential for application over wide areas that were occupied by the Laurentide and Scandinavian ice sheets.
Pollen Representation, Source Area, and Basin Size: Toward a Unified Theory of Pollen Analysis
Authors: Prentice I.Colin
Published: December 2004

The concepts of pollen source area and of production and dispersal biases in pollen representation are quantified by means of a simple theoretical model. Source areas and relative pollen representation are shown to depend on basin size according to functions that describe the amount of pollen remaining airborne at increasing distances from single pollen sources. The form of these functions is determined by physical processes. Standard formulas for elevated sources do not apply, but the integrated form of Sutton's equation for particle dispersal from aground-levelsource gives useful approximations applicable to pollen transport over a forest canopy. Simulations using this equation yielded source areas that increased realistically with basin size, showed substantial differences between source areas for pollen grains with different deposition velocities, and predicted that lighter pollen grains should become better represented with increasing basin size. All of these predictions are qualitatively consistent with present knowledge of the characteristics of pollen assemblages in different depositional environments. The model further allows parameters that can be estimated by statistical calibration methods to be predicted from underlying physical quantities. This extension suggests procedures for testing the theory with quantitative data on surface pollen and forest composition. Preliminary results showed reasonable agreement between estimated and predicted values of dispersal indices for the most abundant taxa in pollen spectra from the northern midwestern United States.
Quantitative Interpretation of Fossil Pollen Spectra: Dissimilarity Coefficients and the Method of Modern Analogs
Authors: Overpeck J. T. , Webb T. , Prentice I. C.
Published: December 2004

Dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples. How eight coefficients responded to differences among modern pollen samples from eastern North America was tested. These coefficients represent three different classes: (1) unweighted coefficients that are most strongly influenced by large-valued pollen types, (2) equal-weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types, and (3) signal-to-noise coefficients that are intermediate in their weighting of pollen types. The studies with modern pollen allowed definition of critical values for each coefficient, which, when not exceeded, indicate that two pollen samples originate from the same vegetation region. Dissimilarity coefficients were used to compare modern and fossil pollen samples, and modern samples so similar to fossil samples were found that most of three late Quaternary pollen diagrams could be “reconstructed” by substituting modern samples for fossil samples. When the coefficients indicated that the fossil spectra had no modern analogs, then the reconstructed diagrams did not match all aspects of the originals. No modern analogs existed for samples from before 9300 yr B.P. at Kirchner Marsh, Minnesota, and from before 11,000 yr B.P. at Wintergreen Lake, Michigan, but modern analogs existed for almost all Holocene samples from these two sites and Brandreth Bog, New York.
Reliability of a Fjord Glacier's Fluctuations for Paleoclimatic Reconstructions
Authors: Mann Daniel H.
Published: December 2004

Historical observations of fjord glaciers in southern Alaska suggest that their fluctuations may be asynchronous with one another and with climate. Possible causes for anomalous fjord glacier response to climatic changes involve the instabilities inherent in a calving terminus, the interaction of fjord geometry with the extent of the calving terminus, and the intersection of low-lying snow line by a thickening glacier. The Lituya glacier system in southeast Alaska is analyzed with reference to these phenomena to test the reliability of its Holocene glacial deposits as paleoclimatic records. This fjord glacier is shown to have been probably free of major, nonclimatic responses during the Holocene except for an insensitive period of up to 1000 yr that followed calving retreats. The insensitive period has no functional effect on how the relatively coarse geologic record is interpreted in terms of paleoclimate. However, it makes impossible any inference of climatic trends from this glacier's behavior in historical times. Fjord glacier deposits can be dependable records of paleoclimate but each glacier requires careful scrutiny. Anomalous glacier responses to climate are most likely to occur in fjords of complex geometry, in regions of relatively low snow line, and where glaciers terminate at fjord mouths bordering the open sea.
Glacial Sequence Near McCall, Idaho: Weathering Rinds, Soil Development, Morphology, and Other Relative-Age Criteria
Authors: Colman Steven M. , Pierce Kenneth L.
Published: December 2004

The sequence of glacial deposits near McCall, Idaho, previously assigned to the Pinedale and Bull Lake glaciations, contains deposits of four different ages. These ages are defined by multiple relative-age criteria, including weathering rinds, soil development, surface-rock weathering, morainal morphology, and loess stratigraphy. The thickness of weathering rinds on basaltic clasts is statistically representative and reproducible and can be used to estimate numerical ages. Following in order of decreasing relation to age are soil development, surface-rock weathering, and moraine morphology. The glacial deposits near McCall appear to correspond to times of high worldwide ice volume indicated by the marine oxygen-isotope record. Pilgrim Cove and McCall deposits, both assigned to the Pinedale glaciation, are late Wisconsin in age, perhaps 14,000 and 20,000 years, respectively. They represent a rare case in which deposits of Pinedale age can be separated by relative-age data. Timber Ridge deposits, assigned to the Bull Lake glaciation, have subdued, but well-preserved morainal morphology; relative-age data indicate that they are pre-Wisconsin in age, probably about 140,000–150,000 years old, although we cannot exclude an older age. Williams Creek deposits are clearly distinct from, and intermediate in age between, McCall and Timber Ridge deposits. Weathering rinds and the inferred ages of the other deposits suggest an early Wisconsin age for Williams Creek deposits.
Lake Devlin and Pinedale Glacial History, front Range, Colorado
Authors: Madole Richard F.
Published: December 2004

Glacial Lake Devlin was an ice-margin lake that formed during Pinedale time when the North Boulder Creek valley glacier blocked the mouth of a tributary near the downvalley limit of glaciation. The lake was about 2 km long and as much as 60 m deep, and was fed by meltwater from small valley glaciers. It accumulated sediment, apparently without interruption, for about 10,000 yr. The inception of Lake Devlin between 23,500 and 21,000 yr B.P. provides a limiting date for the maximum expansion of Pinedale ice, because the lake could not form until the North Boulder Creek glacier had advanced to within 2 km of its downvalley limit. The maximum lowering of timberline, which occurred about 19,000 yr B.P., is assumed to coincide with the Pinedale glacial maximum. Apparent timberline elevations determined from Picea/Pinus pollen ratios suggest that ice-front positions during the time between 23,000 and 19,000 yr B.P. may have been only slightly less extensive than at the Pinedale maximum. Lake Devlin drained catastrophically about 13,000 yr B.P., which was after ice had receded from the outlet area. Pinedale glaciation in the Front Range began about or after 30,000 yr B.P. and final deglaciation occurred between 15,000 and 12,000 yr B.P.
Dissolved Gas Paleotemperatures and 18O Variations Derived from Groundwater Near Uitenhage, South Africa
Authors: Heaton T. H. E. , Talma A. S. , Vogel J. C.
Published: December 2004

Under the near-ideal hydrologic conditions provided by the Uitenhage artesian aquifer, reliable estimates of paleotemperatures were obtained by measurement of the dissolved N2 and Ar in groundwater, confidently dated in the range 28,000 yr B.P. to the present using 14C. The mean annual air temperature in this area during the last glaciation is calculated to have been, on average, 1/2°C lower than during the Holocene. The change in the 18O/16O ratio of the groundwater, corrected for changes in ocean water, amounted to 0.4‰ per °C.
Geochelone in Illinois and the Illinoian-Sangamonian Vegetation of the Type Region
Authors: King James E. , Saunders Jeffrey J.
Published: December 2004

An investigation of Illinoian- and Sangamonian-age deposits in the type region for both Pleistocene stages in central Illinois has yielded a palynological record spanning the Illinoian-year during at least the portion of the Sangamonian represented. Sangamonian boundary associated with an interglacial fauna containing Geochelone crassiscutata. The pollen indicates a shift from high Picea and Pinus to deciduous trees, followed by grass and herbaceous taxa, and finally, a return of deciduous trees. This sequence appears to correlate with marine isotopic stages 6 through 5d. Faunal remains are abundant throughout but megafauna are present only in the interglacial section where Geochelone occurs. The presence of Geochelone suggests above-freezing temperatures in central Ilinois throughout the
Modern Pollen Rain and Vegetational History of the Malaspina Glacier District, Alaska
Authors: Peteet Dorothy M.
Published: December 2004

Seventy surface pollen samples from coastal forest, coastal meadow, muskeg, tree line, and alpine tundra communities form a basis for interpreting fossil pollen assemblages in the Malaspina Glacier district, Alaska. Poflen and macrofossil analyses of three radiocarbon-dated fossil sections from Icy Cape indicate that vegetational changes resulting from plant succession can be distinguished from those of migrational and climatic origin. Vegetation of the early Holocene xerothermic interval (10,000–7600 yr B.P.) was dominated by Alnus communities. Wetter conditions ensued, enabling generative muskeg surfaces to develop and first Picea sitchensis, then Tsuga heterophylla to expand from areas southeastward. Climatic cooling in more recent millennia (3500 yr B.P. to the present) is indicated by the appearance and persistent growth of Tsuga mertensiana and Selaginella selaginoides along this portion of the Gulf of Alaska coastline.
Dung of Mammuthus in the Arid Southwest, North America
Authors: Mead Jim I. , Agenbroad Larry D. , Davis Owen K. , Martin Paul S.
Published: December 2004

The discovery of a unique organic deposit in a dry cave on the Colorado Plateau, southern Utah, permits the first comparison of the physical characteristics and the diet of the dung of the extinct mammoths from the arid Southwest, North America, with that of mammoths from Siberia and northern China, the only other known locations of such remains. The deposit buried beneath sand and rockfall is composed primarily of mammoth dung, estimated at over 300 m3. Radiocarbon dates on dung boluses indicate that the mammoths frequented the cave between approximately 14,700 and 11,000 yr B.P. (the range of ages at 2σ). The desiccated boluses, measuring approximately 230 × 170 × 85 mm, are nearly identical in size to dung from extant elephants. The largest contents in the dung are stalks measuring 60 × 4.5 mm. Grasses and sedges dominated the diet, although woody species were commonly eaten.
“Big Game” Extinction Caused by Late Pleistocene Climatic Change: Irish Elk (Megaloceros Giganteus) in Ireland
Authors: Barnosky Anthony D.
Published: December 2004

Megaloceros giganteus, the largest Eurasian deer, inhabited Ireland from ca. 12,000 yr B.P. to the time of its extinction ca. 10,600 yr B.P. The archaeologic record documents that people arrived on the island no earlier than 9000 yr B.P., so they could not have caused the extinction in Ireland. Close stratigraphic association of the geologically youngest elk fossils with sediments indicating the onset of the Nahanagan Stadial (approximately = Younger Dryas) implicates climatic change as the exterminator. Palynologic data support the idea that extinction probably resulted when forage quantity and quality along with length of the spring green-up decreased during the Nahanagan Stadial. For M. giganteus, this meant that the energy intake required to sustain large bodies, grow enormous antlers, and build fat reserves for winter was increasingly difficult to maintain, until deaths, primarily by winterkill, outnumbered births.
Late Holocene Tectonic Movements at Akhziv, Mediterranean Coastline of Northern Israel
Authors: Lewy Z. , Neev D. , Prausnitz M. W.
Published: December 2004

The recent discovery of a post-Roman-aged marine calcarenite terrace, at an altitude of 7 to 8 m at the ancient harbor of Akhziv, supports the hypothesis of oscillatory tectonic movements along the coastline of Israel during the late Holocene. The marine to estuarine origin of this terrace is indicated by the presence within it of a biocoenosic, sea-marginal to estuarine, assemblage of well-preserved molluscs consisting of taxa tolerating brackish-water, together with a few fresh-water specimens. The transgressive marine sediments onlap and overlie a 2700-yr-old middle Iron Age (Phoenician) tomb, which was built on a dark clay layer, containing a middle Bronze HB (3750 yr B.P.) settlement. In post-Roman times the coastal zone at this site, both east and west of the present coastline, was first subjected to tectonic subsidence of a few meters, and was then tectonically uplifted to its present altitude.
Last Interglacial Sea Levels and Coastal Caves in the Cape Province, South Africa
Authors: Hendey Q. B. , Volman T. P.
Published: December 2004

The dating of the 6 to 8-m shoreline in southern Africa as early Pleistocene prompted a reassessment of evidence from archaeological cave sites on the south coast of the Cape Province which had suggested that this shoreline is of last interglacial age. The successions in the caves at Klasies River Mouth and Die Kelders have been misinterpreted. In fact, they confirm a pre-last interglacial age for this feature. These sites, together with Herolds Bay Cave, indicate that in southern Africa the only last interglacial shoreline above present sea level is at about 4 m, and that it dates from isotope substage 5e.
Varve Studies at Hector Lake, Alberta, Canada, and the Relationship Between Glacial Activity and Sedimentation
Authors: Leonard Eric M.
Published: December 2004

Glacial lake sedimentary records from Hector Lake in Banff National Park, Alberta, are examined with the aim of clarifying the relationship between glacial activity and outwash sedimentation. Rhythmic couplets in lake bottom sediments provide a method for accurate documentation and dating of recent sedimentation chronology, as analysis of 137Cs content indicates that the couplets are of annual periodicity (i.e., varves). A comparison of sedimentation rate records with recent regional glacial history indicates that high sedimentation rates of one to a few decades duration occur either during and immediately following periods of moraine deposition (ie, maximum ice stands) or during periods of rapid ice recession. Comparison of sedimentary records with somewhat longer term glacial and vegetation records indicates that sedimentation rate variations of several centuries duration closely parallel changes in upvalley ice extent. Over this time scale, high sedimentation rates occur during periods of relatively increased ice extent, low rates during periods of reduced ice extent. Within this general pattern, however, sedimentation rates may remain very high for nearly a century following maximum ice stands, due to the exposure of unstable glaciogenic deposits to fluvial reworking during ice recession.
Reconstruction of Annual Temperature (1590–1979) for Longmire, Washington, Derived from Tree Rings
Authors: Graumlich Lisa J. , Brubaker Linda B.
Published: December 2004

Annual growth records from trees at timberline in the Cascade Range of Washington are correlated with variations in temperature and snow depth and used to reconstruct climatic variation in the past. Response surfaces indicate that growth of mountain hemlock (Tsuga mertensiana) and subalpine larch (Larix lyallii) is positively correlated with summer (July to September) temperature and negatively correlated with spring (March) snow depth when snow depth is at or below average. During years of above average snow depth, temperature has little effect on mountain hemlock but has a negative effect on growth in subalpine larch. These interactions make it difficult to reconstruct these climatic variables separately using standard methods. Mean annual temperature values, which combine information on both summer temperature and spring snow depth, were estimated from a regression model that reconstructs past temperature at Longmire, Washington, as a function of larch and hemlock tree-ring chronologies. The reconstruction of mean annual temperature shows temperatures between 1590 and 1900 to be approximately 1°C lower than those of the 20th century. Only during a short period from 1650 to 1690 did temperatures approach 20th-century values.
Middle Holocene Dry Period in the Northern Midwestern United States: Lake Levels and Pollen Stratigraphy
Authors: Winkler M. G. , Swain A. M. , Kutzbach J. E.
Published: December 2004

Four cores from Lake Mendota in the Yahara River valley of south-central Wisconsin provide pollen, charcoal, and sediment-year. Derived estimates of stratigraphic evidence of a middle Holocene dry period in the northern Midwest. The lake level was lower between about 6500 and 3500 yr B.P. indicating that runoff from the upper Yahara River basin may have ceased during the drier seasons of the precipitation between 6500 and 3500 yr B.P. indicate a decrease of about 10% (down to about 700 mm) from the present precipitation value of 800 mm. A warming between 6500 and 3500 yr B.P. is also interpreted based on a change of vegetation from rich mesophytic forest before 6500 yr B.P. toQuercussavanna, with increased charcoal abundances after that time. After 3500 yr B.P., a closedQuercusforest and decreased charcoal suggest a cooler and wetter climate. The qualitative paleoecological interpretations, quantitative precipitation reconstructions based on pollen from the region (including the Lake Mendota data), and estimates of hydrologic budget based on lake-level changes, all show indications of a dry and warm middle Holocene. Evidence from a large regional array of sites also supports these interpretations.
Global Ice-Sheet System Interlocked by Sea Level
Authors: Denton George H. , Hughes Terence J. , Karlén Wibjörn
Published: December 2004

Denton and Hughes (1983,Quaternary Research20, 125–144) postulated that sea level linked a global ice-sheet system with both terrestrial and grounded marine components during late Quaternary ice ages. Summer temperature changes near Northern Hemisphere melting margins initiated sea-level fluctuations that controlled marine components in both polar hemispheres. It was further proposed that variations of this ice-sheet system amplified and transmitted Milankovitch summer half-year insolation changes between 45 and 75°N into global climatic changes. New tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the Antarctic Ice Sheet, thus fitting the concept of a globally interlocked ice-sheet system. But recent atmospheric modeling results (Manabe and Broccoli, 1985,Journal of Geophysical Research90, 2167–2190) suggest that factors other than areal changes of the grounded Antarctic Ice Sheet strongly influenced Southern Hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres. Atmospheric carbon dioxide linked to high-latitude oceans is the most likely candidate (Shackleton and Pisias, 1985, Atmospheric carbon dioxide, orbital forcing, and climate.In“The Carbon Cycle and Atmospheric CO2: Natural Variations Archean to Present” (E. T. Sundquest and W. S. Broecker, Eds.), pp. 303–318. Geophysical Monograph 32, American Geophysical Union, Washington, D.C.), but another potential influence was high-frequency climatic oscillations (2500 yr). It is postulated that variations in atmospheric carbon dioxide acted through an Antarctic ice shelf linked to the grounded ice sheet to produce and terminate Southern Hemisphere ice-age climate. It is further postulated that Milankovitch summer insolation combined with a warm high-frequency oscillation caused marked recession of Northern Hemisphere ice-sheet melting margins and the North Atlantic polar front about 14,00014C yr B.P. This permitted renewed formation of North Atlantic Deep Water, which could well have controlled atmospheric carbon dioxide (W. S. Broecker, D. M. Peteet, and D. Rind, 1985,Nature(London) 315, 21–26). Combined melting and consequent sea-level rise from the three warming factors initiated irreversible collapse of the interlocked global ice-sheet system, which was at its largest but most vulnerable configuration.
Pedogenic Zonation in the Well-Drained Soils of the Arctic Regions
Authors: Ugolini Fiorenzo C.
Published: December 2004

Pedogenic zonation in the soils of the polar regions is a result of gradients in environmental factors and attendant chemical processes. Along a latitudinal transect, it is best manifested at well-drained sites and by soils developed on predominantly silicate rocks. Selected sites in arctic Alaska, in the Canadian arctic, Greenland, and Svalbard adequately fulfill these prerequisites. The processes of podzolization, decarbonization-carbonization, pervection, and salinization as models of arctic pedogenesis demonstrate that processes occurring in the temperate region also operate in the Far North. Brunification, melanization, and oxidation are recognized for the first time as current geochemical and pedogenic mechanisms of the Arctic region. Traditional genetic soil names have been retained because they represent a closer relationship to pedogenic processes than the more modern nomenclature. The identification, the chemical behavior, the strength, abundance, and mobility of the proton donors and conjugate bases are keys to the genesis of soils and the distinction of contrasting soil processes. This new approach to the understanding of arctic pedogenesis can be better fulfilled by collecting, analyzing, and interpreting soil solution obtained in situ.
Altitudinal and Latitudinal Migration of Cryptomeria japonica for the Past 20,000 Years in Japan
Authors: Tsukada Matsuo
Published: December 2004

Biostatistical analysis of modern pollen assemblages in 152 Japanese surface samples shows that Cryptomeria japonica can normally grow in areas with a mean January temperature of approximately −7° to 7°C, a mean August temperature of 19° to 27°C, and an effective precipitation (total precipitation during the growing season) of over 1000 mm. The full-glacial distribution of the species on both the Sea of Japan and the Pacific coasts (35–36°N lat) indicates that in these areas the maximum possible reduction of temperature was 8.7–10.2°C in January and 6.0–7.3°C in August, and that the effective precipitation was low, being 1000–1350 mm, or 40–55% below the modern level, provided that the species has not changed its physiological characteristics. Populations of C. japonica expanded northward and upslope from their full-glacial areas of distribution immediately after late-glacial climatic amelioration. This expansion appears to have been regulated mainly by the availability of effective precipitation which became high in northeastern Honshu about 4000 yr ago. After about 2500 yr B.P., C. japonica was planted extensively by humans in moist, temperate climatic regions (excluding Hokkaido), and now has its widest distribution since at least the last full-glacial interval.
Contrasting Climatic Histories for the Snake River Plain, Idaho, Resulting from Multiple Thermal Maxima
Authors: Davis Owen K. , Sheppard John C. , Robertson Susan
Published: December 2004

Ten sites near the Snake River Plain have consistent differences in their climatic histories. Sites at low elevation reflect the “early Holocene xerothermic” of the Pacific Northwest, whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later, ca. 6000 yr ago. This elevational contrast in climatic histories is duplicated at three sites from the central Snake River Plain. For sites in such close proximity, the different chronologies cannot be explained by changes in atmospheric circulation during the late Quaternary. Rather, the differences are best explained by the autecology of the plants involved and the changing seasonal climate. The seasonal climatic sequence predicted by multiple thermal maxima explains the high- and low-elevation chronologies. During the early Holocene, maximum insolation and intensified summer drought in July forced low-elevation vegetation upward. However, moisture was not a limiting factor at high elevation, where vegetation moved upward in response to increased length of growing season coincident with maximum September insolation 6000 yr ago.
Holocene Fires in the Northern Amazon Basin
Authors: Saldarriaga Juan G. , West Darrell C.
Published: December 2004

The ubiquitous occurrence of charcoal in the forest soils of the Upper Rio Negro region of Colombia and Venezuela indicates the presence of frequent and widespread fires in the Amazon Basin, possibly associated with extremely dry periods or human disturbances. Charcoal ranged from 3.12 to 24.76 mg/cm3 in the upper 50 cm of soil and was more abundant in Oxisols and Ultisols than in other soil types. Charcoal dates range from 6260 yr B.P. to the present. Several dates coincide with dry phases recorded during the Holocene. Ceramic shards were found at several sites, and thermoluminescence analysis indicates that their ages range from 3750 to 460 yr B.P. The age of charcoal and shards confirms that this region has been subjected to fire and human disturbances during the past 6000 yr.
Paleoclimatic Inferences from an Isotopic Investigation of Groundwater in the Central San Juan Basin, New Mexico
Authors: Phillips Fred M. , Peeters Leslie A. , Tansey Michael K. , Davis Stanley N.
Published: December 2004

Groundwater from the Ojo Alamo and Nacimiento aquifers in the central San Juan Basin. New Mexico, has yielded 14C ages ranging from modern to 35,000 yr B.P. The Pleistocene-age samples are characterized by a stable isotope content about 25‰ lighter in D and 3‰ lighter in 18O than modern precipitation and groundwater. We attribute this difference to a colder mean annual temperature and perhaps increased winter precipitation. Consideration of various factors controlling the stable isotope composition of the groundwater allows estimation of a 5° to 7°C temperature decrease during the late Wisconsin, accompanied by increased effective precipitation. A similar estimate of the temperature change is obtained from noble-gas paleothermometry. These data support a model of moderately cooler late Pleistocene climate in the American Southwest characterized by summers with less precipitation than today, but wetter winters.
A Late Holocene Marine Terrace on the Kidnappers Coast, North Island, New Zealand: Some Implications for Shore Platform Development Processes and Uplift Mechanism
Authors: Hull Alan G.
Published: December 2004

A marine terrace up to 6 m above present mean sea level is preserved along 15 km of the Kidnappers coast, Hawke's Bay, North Island, New Zealand. Radiocarbon dates for 10 shell samples collected from intertidal marine deposits overlying an uplifted shore platform have a total age range of 590 yr (from 2280 ± 50 to 2750 ± 70 yr B.P.). Sample age decreases landward suggesting a small relative sea-level rise, probably as a result of tectonic subsidence prior to uplift. Rates of contemporary shore platform formation preclude the preservation of a marine terrace subjected to constant, aseismic uplift. Preservation of a subhorizontal uplifted shore platform mantled by intertidal marine deposits with in situ fauna is best explained by abrupt coseismic uplift 2300 yr B.P. and preceded by tectonic subsidence. The presence of a single marine terrace does not permit the calculation of past earthquake magnitude or recurrence, but the NNE tilt of the 2300-yr-old marine terrace indicates continued growth of the north-trending late Pleistocene Kidnappers Anticline.
Holocene Development of Parabolic Dunes in the Central St. Lawrence Lowland, Québec
Authors: Filion Louise
Published: December 2004

Stabilized parabolic dunes in the central St. Lawrence Lowland are oriented NE-SW, in the postulated direction of dune-building winds coming from anticyclonic air circulation induced by the retreating Laurentide Ice Sheet about 10,000 yr ago. The eolian chronology reconstructed from several sections in mixed dune-peatland environments indicates that postglacial plant colonization, characterized by a fortuitous assemblage of arctic-subarctic and boreal elements, preceded dune formation during Champlain Sea regression around 10,000 yr B.P. Confined peatlands and small forests were buried by eolian sands between 10,000 and 7500 yr B.P. under dry and temperate conditions. This eolian episode lasted about 250014C yr and ended when cyclonic air circulation similar to the present humid climatic regime was established following the breakup and disappearance of the Laurentide Ice Sheet over Hudson Bay and peripheral areas. Dune stabilization, through paludification of well-drained eolian sands about 7500 yr B.P., suggests a major shift in climate toward wetter conditions that have been characteristic during most of the Holocene in eastern North America. Minor eolian erosion induced by wildfire was recorded during late Holocene time (about 1250 yr B.P.). Anthropogenic perturbation (logging and agriculture practice) was also responsible for recent very local eolian activity.
Morphological and Chemical Characteristics of Soil Catenas on Pinedale and Bull Lake Moraine Slopes in the Salmon River Mountains, Idaho
Authors: Berry Margaret E.
Published: December 2004

Morphological and chemical properties of soils developed on moraines of granitic composition, and forested with lodgepole pine, in Bear Valley, Idaho, change significantly with age and slope position. Soil development on Pinedale and Bull Lake moraine slopes of similar curvature and steepness was assessed at the summits, shoulders, backslopes, and footslopes of both catenas, and at the toeslope of the Bull Lake catena. Many soil properties show trends in development with both age and slope position. These properties include clay content, clay film development, color, plagioclase weathering, and dithionite-citrate-extractable iron (Fed). The degree of development of all these properties is greater on the Bull Lake catena relative to that on the Pinedale catena. This trend reflects increased soil development with age. On both catenas, development of soil properties is commonly highest at the footslope or toeslope sites and minimum at the backslope site. Downslope changes are attributed to both colluviation and pedogenic processes, including sorting of sediments during downslope transport, greater accumulation of eolian materials transported to downslope sites by surface processes, and greater in situ weathering of mineral grains at the footslope and toeslope sites.
Postglacial Vegetation History of the Mackenzie River Basin
Authors: MacDonald Glen M.
Published: December 2004

Three radiocarbon-dated cores from small lakes provide pollen records of postglacial vegetation change in the central Mackenzie River basin. These data are combined with previously published records to reconstruct vegetation development from central Alberta to the Mackenzie delta. The paleoecological data demonstrate that a continuous corridor of herb-and-shrub-dominated vegetation extended between Beringia and the Great Plains of North America from deglaciaiton until about 10,000 yr B.P. The initial vegetation was replaced by spruce forests between 10,000 and 8500 yr B.P. Significant vegetation change continued until approximately 500 yr B.P. when the muskeg-dominated landscape typical of the present subarctic was established. The initial herb-and-shrub vegetation was likely a reprise of conditions which existed during earlier Pleistocene deglaciations. These conditions may have provided a favorable environment for animals adapted to nonforested vegetation and promoted migration southward from Beringia and northward from the Great Plains during the last deglaciation and earlier Pleistocene deglaciations. The sequence of postglacial vegetation change in the Mackenzie basin likely reflects a combination of climatic change, edaphic change, and plant migration patterns and interactions.
Ice-Sheet Dynamics and Glacial History of Southeasternmost Baffin Island and Outermost Hudson Strait
Authors: Miller Gifford H. , Hearty Paul J. , Stravers Jay A.
Published: December 2004

Southeasternmost Baffin Island is mantled by Hudson Strait drift; it contains abundant limestone erratics and 20 to 50% carbonate in the matrix. To the northwest, it is replaced by drift dominated by locally derived rock of the Canadian Shield. The sense and orientation of ice-erosional features demonstrate that Hudson Strait drift is associated with northeasterly ice flow that crossed the tip of Meta Incognita Peninsula; local drift, associated with ice flow S10°W along the Hudson Strait coast, was derived from a dispersal center on the peninsula. Erratic lithologies contained in the Hudson Strait drift indicate a Labradorean provenance. Large-scale bedrock molding and the distribution of cirques indicate NE-flowing ice has been dominant throughout the middle and late Quaternary. Radiocarbon dates of in situ shells confirm that deglaciation began more than 11,000 yr ago, with the Frobisher Bay coast becoming ice free by 9300 yr ago. Five dates from Hudson Strait suggest that the strait was deglaciated before 9000 yr BP. However, ice from the Labradorean Sector recrossed Hudson Strait during the Cockburn Substage, about 8500 yr ago, damming drainage from the west. Final retreat of Labradorean ice from Baffin Island was complete by 8000 yr ago, at which time the sea was able to penetrate Hudson Bay.
Uranium-Series Age Estimates and Paleoclimatic Significance of Pleistocene Tufas from the Lahontan Basin, California and Nevada
Authors: Lao Yong , Benson Larry
Published: December 2004

An extended chronology of Lahontan basin lake levels based on uranium-series age estimates correlates with the global ice-volume record. Lake highstands occur at or shortly after times of maximum ice-sheet size. Moderate size lakes occur when the global ice volume is about 80% of its maximum. The data indicate that lake levels rise and fall relative to the proximity of the mean position of the jetstream. When the continental ice sheet is above some threshold size or shape, it appears that the large-scale circulation and climatic conditions are right for producing lakes of moderate to large size within the Lahontan basin.
Stable Isotopes of Holocene Calcareous Tufa in Southern Poland as Paleoclimatic Indicators
Authors: Pazdur Anna , Pazdur Mieczyslaw F. , Starkel Leszek , Szulc Joachim
Published: December 2004

The isotopic composition of oxygen in freshwater calcareous tufa seems to be a sensitive indicator of past climatic changes. Results of measurements of δc18O and δc13C in tufa samples dated with the 14C method are used to reconstruct Holocene climatic changes in southern Poland. Values of δc18O obtained on tufa samples from four sites (Raclawka, Rzerzuŝnia, Trzebienice, Sieradowice) representing different hydrodynamic conditions of tufa sedimentation seem to form a selfconsistent series. These values, with some simplifying assumptions concerning the course of tufa sedimentation, were therefore used to estimate mean annual temperatures in the interval ca. 9500-2000 yr B.P. When the resulting curve of thermal changes in southern Poland is compared with changes of deposition and erosion of tuffaceous sediments and with results of other methods of reconstruction of paleoclimate in central Europe, a reasonable agreement among the different specific methods is seen.
Uranium-Series Ages of Corals and Coexisting Phosphate Deposits on Pelsaert Reef Complex, Houtman-Abrolhos Islands, Western Australia
Authors: Veeh H. Herbert , France Roy E.
Published: December 2004

An unusually well-defined association between guano-derived phosphate rock (apatite) and coral carbonates on Pelsaert Island has provided an opportunity to test uranium-series dating methods as applied to insular phosphorites. The phosphate deposit, which is bracketed by late Pleistocene and Holocene corals with 230Th/234U ages of 120,000 and 4700 yr B.P., respectively, has 230Th/234U ages ranging from 85,000 to 112,000 yr B.P. The mutually consistent results suggest that phosphate deposition commenced soon after the peak of the last interglaciation and has been largely controlled by sea-level fluctuations and probably other factors associated with late Quaternary climate in this area.
Megafaunal Butchering at Lubbock Lake, Texas: A Taphonomic Reanalysis
Authors: Kreutzer Lee Ann
Published: December 2004

Five seasons of excavation in Feature Area 2-1 of the Lubbock Lake Landmark, Texas, exposed a megafaunal bone accumulation in sands and gravels deposited by a late Pleistocene meandering stream. Many bone specimens exhibit evidence of alteration, supporting interpretation of the feature as an in situ, secondary meat-processing area; the gravels are interpreted as the point bar of a meandering stream. Faunal remains lying stratigraphically above the point bar have been considered to form a separate, noncultural feature produced by stream flooding. However, rose diagrams and analysis of adjusted residuals demonstrate that a statistically significant amount of bone in each feature is aligned along axes of preferred orientation. Further, the orientation patterns and statistical analyses of both features exhibit the same trends, suggesting that the same processes affected both. Although the evidence does not rule out a role of human behavior, it does demonstrate that stream currents significantly influenced feature structure.
Lithospheric Thickness, Antarctic Deglaciation History, and Ocean Basin Discretization Effects in a Global Model Of Postglacial Sea Level Change: a Summary of Some Sources of Nonuniqueness
Authors: Peltier W. R.
Published: December 2004

The global model of postglacial relative sea level variations that has been developed over the past decade is employed to investigate the constraints that it may be invoked to place on the timing of the deglaciation of West Antarctica. The analyses presented here confirm the suggestion of P. Wu and W. R. Peltier (1983, Geophysical Journal of the Royal Astronomical Society 74 , 377–450) that the model of this event employed in J. A. Clark and C. S. Lingle (1979Quaternary Research 11 , 279–298) may be simply modified to rectify the misfits between theory and observation that are otherwise obtained at Southern Hemisphere sites. A large number of Southern Hemisphere relative sea level data are shown to require that the retreat of Antarctic ice substantially lagged the retreat of Northern Hemisphere ice if the deglaciation of Antarctica was abrupt. The time of onset of Antarctic deglaciation is thereby shown to coincide with the time of most rapid Northern Hemisphere deglaciation. Sensitivity tests are performed which demonstrate that this result is relatively insensitive to the discretization employed to represent the ocean basins; the only exception to this general rule obtains at some coastal sites at which a trade-off is revealed between the delay of West Antarctic melting and the thickness of the lithosphere required to reconcile the observed local variations of relative sea level. At such sites, which are all in the far field of the ice sheets, some attention must be paid to the accuracy of the local finite element representation of the oceans and to the details of the Antarctic deglaciation history.
A 15,000-year Isotopic Record from Lake Zürich of Deglaciation and Climatic Change in Switzerland
Authors: Lister Guy S.
Published: December 2004

Ostracod and pelecypod carbonate preserved since the latest Pleistocene in the bottom sediments of Lake Zürich was probably formed under constant temperature conditions. Temporal shifts in the oxygen-isotype ratios for those carbonates therefore correspond to shifts in the isotopic character of the net lake inflow. Alpine deglaciation, which released isotopically light meltwaters, commenced prior to ca. 15,000 yr B.P. and was essentially completed in northern Switzerland by 12,4000 ± 250 yr B.P., well before substantially increased atmospheric heat was available from either increased insolation or an increased atmospheric CO2 content. The early Holocene climate for the region was characterized by minor short-term fluctuations in mean annual air temperatures and an overall amelioration of up to 2°C. Contemporaneously precipitated authigenic and biogenic carbonates have recorded partitioning of carbon isotopes between surface and bottom waters during photosynthetic production and subsequent oxidation of organic matter in the lake. The degree of that partitioning provides an index of the relative production rates, which were low in the late Pleistocene meltwater lake but considerably enhanced during the Holocene.
Climate and Sea Level During Oxygen Isotope Stage 7b: On-Land Evidence from New Zealand
Authors: Pillans Brad , Holgate Geoff , McGlone Matt
Published: December 2004

Strata at Landguard Bluff, near Wanganui, New Zealand preserve a clear record of relative sea-level changes during oxygen-isotope stage 7. Two relative high sea-level stands (during stages 7a about 210,000 yr ago and 7c about 240,000 yr ago) are separated by a relative low sea level (stage 7b) that was at least 32 m lower than present. Pollen analysis of sediment deposited during stage 7b indicates climate at the time was up to 3°C cooler than present. The climate and sea-level evidence from Landguard Bluff are consistent with oxygen-isotopic evidence from deep-sea cores indicating a marked cooling during stage 7, which is closely associated with a summer radiation minimum centered at about 230,000 yr ago in the Northern Hemisphere.
Late Wisconsin History North of the Giants Range, Northern Minnesota, Inferred from Complex Stratigraphy
Authors: Björck Svante
Published: December 2004

In an area north of the Giants Range in northeastern Minnesota the late Wisconsin glacial and extraglacial lithostratigraphy shows that, apart from one occurrence of red clayey till, the deposits can be related to the deglaciation of the Rainy Lobe, the margin of which retreated northward, leaving debris-rich ice behind. By a combination of pollen stratigraphy, lithostratigraphy, and chronostratigraphy of lake sediments in this area, together with multivariate numerical analyses of the data set, a “hiatus” stratigraphy was set up. Combined with the glacial and extraglacial stratigraphy, it shows that the area of Glacial Lake Norwood was possibly later filled with sediments, between masses of stagnant ice, following a damming of drainge in the south by the St. Louis Sublobe. The area was drained through the Embarrass channel when the St. Louis Sublobe retreated. Then followed the drainage of Lake Koochiching through the Embarrass channel. At ca. 10,200 14C yr B.P. the area apparently became free of stagnant ice as normal lake sedimentation began in all lakes studied. A lake-level rise is indicated ca. 1000 yr later. Apart from a long-lasting phase of birch tundra parkland between ca. 12,000 (or 11,500?) and 10,600 14C yr B.P., the general pollen stratigraphy fits into the regional picture with a more or less undisturbed and gradual plant immigration from the time of the culmination of the St. Louis Sublobe.