Analysis of in situ-produced 10Be and 26Al demonstrate that some Australian inselbergs (granitic domes) are among the most stable geomorphic surfaces in the world, eroding at rates as low as 0.6 m/myr. Twenty isotopic analyses of ten samples suggest that the bare bedrock tops of these isolated granitic domes have been exposed to cosmic radiation for at least 0.5 myr and are eroding at a mean model rate less than 0.7 ± 0.1 m/myr (n = 6). Isotopic analyses of samples collected from the top of Mt. Wudinna, Little Wudinna, and Yarwondutta Rock are most consistent with continuous exposure during erosion. On the other hand, samples collected from the flanks of some domes and the tops of other domes have isotopic abundances suggestive of complex exposure histories including burial and reexposure. These unique isotopic data provide the first quantitative information for evaluating longstanding, but previously untested, hypotheses regarding the antiquity and development of these enigmatic landforms and indicate that some Eyre Peninsula inselbergs are probably relict features of pre-Pleistocene landscapes.

The rock magnetic properties of the Chinese loess and paleosols constitute a unique and sensitive record of East Asian paleoclimate through the Quaternary Period. Systematic variations in the concentration and grain size of the magnetic minerals in these sediments have produced systematic variations in the magnetic susceptibility signal, which can be easily and rapidly measured at many sites across the Loess Plateau. Variations in many other rock magnetic properties can be used to identify the key shifts in ferrimagnetic grain size, but magnetic susceptibility alone is sufficiently sensitive to record stadial and interstadial climate stages, as well as glaciations and interglaciations. Past changes in rainfall and monsoon activity for this region are reconstructed from the susceptibility variations. The susceptibility record is calibrated using the modern relationship between rainfall and pedogenic susceptibility on the Loess Plateau. Our rainfall reconstructions identify enhanced summer monsoonal activity in the Chinese Loess Plateau region in the early Holocene and the last interglaciation. In the presently semiarid western area of the plateau, annual precipitation in interglacial times was up to 80% higher than at present; in the more humid southern and eastern areas, values were up to 20% higher than today's levels. During the last glaciation, precipitation decreased across the entire plateau, typically by ∼25%. The relationship between pedogenic susceptibility, climate, and weathering age was examined over the Northern Hemisphere temperate zone and the observed positive correlation between rainfall and susceptibility indicates that climate, rather than soil age, is the predominant factor that controls pedogenic susceptibility enhancement in loess soils.

A 46-m core of lake sediments, obtained from the center of the explosion crater of Praclaux (Haute-Loire, Velay, France), was studied on the basis of 368 pollen spectra. Five temperate forest episodes alternating with phases indicative of glacial climates are recorded. Two of these episodes show vegetation successions representative of full interglaciations; the oldest is contemporaneous with the Holsteinian interglaciation. A thick trachytic tephra permits correlation to be established with the pollen sequence from Lac du Bouchet. This comparison indicates the presence of two complete interglaciations between the Holsteinian and the Eemian that are the equivalents of marine isotope stages 7 and 9. The Holsteinian therefore corresponds to isotope stage 11.

A pollen and sediment record of a core 4.2-m-long from Laguna Baja (7°42′ S, 77°32′ W, 3575 m) in the Cordillera Oriental of northern Peru suggests several episodes of major vegetational and climatic change over the past 13,000 yr. The oldest pollen assemblage consists of a mixture of paramo elements (tropical alpine vegetation), including high percentages of Poaceae (40%) that decline upward, moist montane forest (Compositae and Polylepis), and wet montane forest (e.g., Hedyosmum and Podocarpaceae). Organic carbon content range from <2% to 8%. About 11,600 yr B.P. this mixed pollen assemblage was replaced by Poaceae (>60%), with high percentages of Jamesonia, a fern characteristic of paramo and decreasing values of Plantago tubulosa and the wet montane forest elements Hedyosmum and Podocarpaceae. Charcoal percentages are at a maximum during this period, magnetic susceptibility and sand percentages are high, and percentages of organic matter are low. Several explanations for these changes are possible, including a reduction in temperature and moisture, more frequent periods of aridity with increased fires, or natural succession. The Holocene record begins with pronounced increases in organic carbon and pollen of wet montane forest, primarily Hedyosmum , Podacarpaceae, and Urticales. High values of Podocarpaceae pollen (>35%) and a decline in charcoal suggest temperature and moisture levels above modern-day values. Wet montane forest pollen remain high and charcoal values are low from about 10,000 to 6000 yr B.P., suggesting that warm and moist conditions prevailed for about 4000 yr. Subsequently Podocarpaceae and Urticales decline, and for a brief time Alnus is prominent in the pollen record. Following the Alnus maximum at about 5000 yr B.P., Poaceae, Ambrosia and Chenopodiaceae/Amaranthaceae become frequent. Increased paramo and disturbance indicator pollen suggest increased anthropogenic activities in this region from the middle Holocene to the present.

The dynamics of a cliff-top dune system located at the foot of the Mackenzie Mountains was reconstructed by radiocarbon dating and tree ring analysis of forest paleosols in eolian sediments. The first evidence of eolian activity dates to ca. 3000 yr B.P. when the breaching of a bedrock sill initiated the erosion of glaciofluvial deposits that resulted in the exposure of a 75-m-high cliff of erodible sediment. Sandy sediment eroded from the cliff By katabatic winds from the Mackenzie Mountains buried a mature forest growing on alluvial sediments. Despite a minor eolian event between 750 and 860 cal yr A.D., dune development began ca. 1100 cal yr A.D. and has been marked by two major sedimentation periods between ca. 1100 cal yr A.D. and 1460 A.D. and from 1865 to present. Detailed analysis of tree morbidity and mortality indicates that the dune progressed at an average rate of 78 cm/yr for the last century. Dune dynamics are directly related to slope activity that controls the episodic nature of sediment availability and to the katabatic wind regime. Comparison of the dune dynamics and paleoclimatic data suggest a possible influence of warm climate on eolian activity.

Modern pollen samples from 15 lakes along a north-south transect on western Somerset Island, NWT, Canada, show a decrease in pollen concentrations from the high arctic to the mid-arctic zone, but there are few differences in the pollen percentages between these sites. Long-distance transport accounts for up to 50% of the pollen in these lake sediments. Cores from two lakes show few changes in the percentages of important pollen types, except for an initial period, before 6000 yr B.P., of increased Salix. The pollen concentration of lake RS36 from the mid-arctic is twice that of lake RS29 from the high arctic, and at both sites the concentrations decreased during the past 6000 yr B.P. This suggests a climatic deterioration during the past 6000 yr which has caused a decrease in the abundance of plants on the landscape.

Basal sediments of Lake Torfadalsvatn, northern Iceland, record changes in terrestrial and limnic environments in the period 11,300-9000 14C yr B.P. These changes were probably forced by climate and connected with displacements of the marine polar front and sea-ice margin. Pollen, spores, green algae (Pediastrum), saturation isothermal remanent magnetization, and carbon content of the basal sediments provide the first detailed biostratigraphic record of the last glacial-interglacial transition in Iceland. During the first pioneer phase, beginning at ca. 11,300 14C yr B.P., grasses and fell-field herbs became established, and lake productivity was very low. At ca. 10,900 14C yr B.P., climatic and soil conditions became favorable for shrubs and dwarf shrubs. This change, together with increased limnic productivity, clearly indicates long seasons without ice-cover in the sea immediately north of Iceland. A return to a colder climate (Younger Dryas), probably in connection with a southward displacement of the marine polar front, occurred by 10,600 14C yr B.P. Shrub and dwarf-shrub vegetation disappeared, and limnic productivity diminished. A second pioneer vegetation phase, dominated by Oxyria/Rumex and grasses, was initiated by a change to longer seasons without sea ice at ca. 9900 14C yr B.P. This warming is also evident as a contemporaneous increase in lake productivity. After ca. 9400 14C yr B.P. the reestablishment of dwarf-shrub heaths and very high limnic productivity indicate further warming.

Calibration of the radiocarbon timescale of paleoecological records is essential if they are to be explained correctly in terms of their governing ecological or climatological controls. The differences between calendar ages and radiocarbon ages that arise from variations in 14C production through time can distort the chronologies of individual records and the interpretations based on them. Misleading impressions of synchrony or diachrony of events among multiple records can result, and estimates of the apparent duration of episodes and rates of sedimentation and local population changes can be biased. Displays of the temporal patterns of migration or extinction may also be affected. Spurious correlations may arise between records with radiocarbon-controlled chronologies and time series of potential controls that are expressed on a calendar time scale. Support for particular explanations of features in a paleoecological record may vary depending on whether radiocarbon ages are calibrated or not. This situation is illustrated using the eastern Beringian Populus subzone as an example. When the radiocarbon ages that control the timing of the Populus subzone are calibrated, the contemporaneous decrease in ice volume and increase in summer insolation are implicated as the ultimate controls of the occurrence of the subzone.

New pollen records from White Lake in the Southern High Plains and from Friesenhahn Cave on the southeastern Edwards Plateau of Texas indicate that the glacial-age vegetation of the southern Great Plains was a grassland. The High Plains was a treeless Artemisia grassland and the Edwards Plateau, at the south edge of the Great Plains, was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats. The glacial-age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog. The dominance of prairie vegetation during the last glacial maximum is compatible with late Pleistocene mammalian faunas and late-glacial grassland pollen records from the region. Earlier interpretations of a pine-spruce forest on the High Plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration, resulting in differential preservation of conifer pollen grains. Accordingly, the "Tahoka Pluvial" and other "climatic episodes" defined by High Plains pollen records are abandoned.

Paleoclimatic interpretation of proxy data is complicated sometimes by the appearance of heterogeneous patterns of climatic responses across networks of sites. Modern climate analogues for the western United States, similar to those patterns of atmospheric circulation of 18,000 and 9000 yr B.P., were examined in order to explain such patterns of spatial heterogeneity. Modern analogues were defined by comparing modern atmospheric circulation patterns with those simulated by general circulation models. Maps of temperature and precipitation anomalies of the modern analogues reveal patterns of spatial heterogeneity, which resemble the patterns of effective moisture compiled from paleoclimatic data. January 1957 was found to be a reasonable 18,000 yr B.P. analogue, and it features isolated areas of increased wetness in the northern Great Basin and increased dryness in the Northwest interior. Analogues for 9000 yr B.P. from a composite of 11 Augusts display patterns of spatial heterogeneity of effective moisture over most of the mountainous areas. The analogues suggest that spatial heterogeneity of climate is the rule rather than the exception over much of the western United States, with the climatic anomalies at any particular time representing the outcome of the mediation of large-scale atmospheric circulation controls by smaller scale topographic features.

Woodrat middens from the northern Bonneville Basin allow a reconstruction of vegetation changes from 14,000 to 9000 yr ago. Cold montane steppe, dominated by sagebrush, covered much of the western Bonneville Basin prior to 13,000 yr ago. From 13,000-10,800 yr ago, the region was vegetated by limber pine woodlands in lower montane settings and a mosaic of limber pine and sagebrush steppe along basin flour margins. These low-elevation limber pine woodlands began to retreat upslope after about 11,000 yr ago due to increasingly drier climatic conditions, and were replaced by relatively more xeric desert scrub dominated by sagebrush and shadscale. The growth of limber pine at low elevations suggests that summer temperatures were as much as 6°C lower than at present. This evidence is in apparent conflict with the currently accepted post-Provo Lake Bonneville chronology, especially the magnitude of the postulated near-dessication of Lake Bonneville from ca. 13,000-12,200 yr ago.

Ring widths from five Picea glauca stands at the alpine treeline in northwestern Canada are used to investigate climate-growth responses and to develop a long reconstruction of summer temperatures. Response function and linear regression analyses indicate that the radial growth response of these trees to climate varies with age and site. At most sites, the period of significant positive response to growing season temperatures declines with tree age. Age-dependent and standard (age independent) models are then used to develop two reconstructions of June-July temperatures for northwestern Canada extending back to A.D. 1638. Calibration statistics were similar for both models, but the standard model performed poorly during verification. The reconstruction produced using age-dependent modeling suggests June-July temperatures were cooler than present throughout most of the past 350 years, with the exception of the late 18th century. Particularly cool periods occurred at ∼1700 and in the mid-19th century. In constast, the standard model suggests that temperatures were similar to or warmer than present during the last 350 years. The age-dependent reconstruction compares favorably with other proxy climate records from northern North America. Age-dependent dendroclimatic modeling can provide a sensitive record of recent climatic change that allows the inclusion of previously rejected sites into dendroclimatic analyses.

Previously undescribed plant and animal fossils from the Whidbey Formation represent two environments. An upper sand unit contains predominantly terrestrial molluscs (4 taxa), insects, and a vole (cf. Phenacomys), whereas a lower clay unit contains ostracodes (9 taxa), freshwater molluscs (6 taxa), insects (9 taxa), freshwater plant seeds (6 taxa), and fish (cf. Gasterosteus : stickleback). These taxa are compatible with interglacial climatic conditions on a coastal plain environment. The inferred freshwater and terrestrial environments of the Whidbey Formation imply local tectonic subsidence of the regional since the last interglaciation.

Oxygen and hydrogen isotopes were measured in wood cellulose and cellulose-nitrate from trees that grew in different hydrologic settings in southwestern Ontario, Canada. An isotope model that accounts for isotopic fractionations associated with photosynthesis in plants was applied to the stable isotope data to infer past meteoric water isotopic composition and seasonal air moisture variations. The model-inferred climate data was rationalized in terms of the trees' hydrologic environment and weather characteristics of the Great Lakes region. The result is an account of summer and winter conditions in southwestern Ontario for 275 years (1610 to 1885) prior to instrumental climate records. Conditions between 1610 and 1750 are inferred to have been cooler and drier than present. This was followed by a warm-moist climate interval between 1750 and 1885 during which there was an increase in winter precipitation. Cool-dry conditions were recorded instrumentally in this region at the end of the nineteenth century.

Tree-ring chronologies from living and sub-fossil Pinus flexilis James (limber pine) trees extend back more than 500 yr on the western edge of the Great Plains in Alberta. Living trees were found to be as old as 526 yr. Tree-ring growth in Pinus flexilis is most sensitive to annual precipitation over the annualization period August to July. The longevity of the trees coupled with their sensitivity to variations in annual precipitation make them an important resource for constructing annually resolved multicentury records of paleohydrology on the northwestern Great Plains. A 487-yr reconstruction of annual precipitation in southwestern Alberta was produced from the tree-ring series. This is the longest dendroclimatological reconstruction of precipitation available from the northern plains. The reconstruction has some similarity to reconstructions from the western Great Plains of the United States. However, there are also many divergences in the timing of droughts. Some of this divergence may reflect the importance of orographic uplift in producing precipitation along the eastern flanks of the Rocky Mountains. Our reconstruction shows that the frequency of droughts in Alberta during the period of instrumental records, about the last 100 yr, has not been appreciably different from conditions of the preceding four centuries. In addition, the most severe drought of this century, which led to widespread farm abandonment between 1918 and 1922, was not the most severe drought in the past 487 yr.

Carbon and nitrogen stable isotope analysis of fossil bone collagen reveals that Pleistocene short-faced bears (Arctodus simus) of Beringia were highly carnivorous, while contemporaneous brown bears (Ursus arctos) had highly variable diets that included varying amounts of terrestrial vegetation, salmon, and small amounts of terrestrial meat. A reconsideration of the short-faced bear's highly derived morphology indicates that they foraged as scavengers of widely dispersed large mammal carcasses and were simultaneously designed both for highly efficient locomotion and for intimidating other large carnivores. This allowed Arctodus to forage economically over a large home range and seek out, procure, and defend carcasses from other large carnivores. The isotope data and this reconstruction of Arctodus' foraging behavior refute the hypothesis that competition from brown bears was a significant factor in the extinction of short-faced bears.

A sequence of seven superimposed paleosols developed on eolian calcarenites and alluvium was sampled on the island of Lanzarote in order to examine the possibility of dating land snail shells by the U-series method, using a TIMS technique allowing measurement of U and Th isotopes in very small samples. In the lower six units, the fossil shells yielded D-allo/L-isoleucine (A/I) ratios of about 0.5 and apparent AMS 14C ages ranging from 41,000 to 34,000 yr B.P., indicating that most paleosols formed during a relatively short mid-Würm humid episode. The upper unit (paleosol 7) yielded more variable A/I ratios (ranging from 0.6 to 0.2) and a younger 14C age ∼27,000 yr B.P. Most samples contained enough U to allow the calculation of U-series ages, after correction for the presence of a detrital component. In samples containing a few tens of ppb of U (paleosols 1, 2, 3, 6, and 7), the ages are strongly dependent upon the model used for the correction. In samples containing more than 300 ppb of U (paleosols 4 and 5), concordant ages of ∼31,000 ± 1000 yr were obtained regardless of the correction model used. U uptake in these shells occurred during one single early diagenetic phase, soon after burial, since shells of modern snails do not contain any significant amount of U. The arid conditions subsequent to the mid-Würm humid episode have likely ensured since then a fair closure of the radioactive system.

Paleoceanographic and onshore paleoclimatic changes during the last 59,000 yr are established from three deep-sea sediment cores off northeast New Zealand using an integrated log of sediment texture, CaCO3 content, palynology, and planktonic and benthic foraminiferal δ18O and δ13C data, together with dated silicic tephras. These records from the isotopic stage 4-3 boundary to the present record northern New Zealand vegetation history, changes in a subsidiary equatorward flow of Circumpolar Deep Water, and sea-surface temperatures (SSTs) for subtropical water (STW) between latitudes 36°42′ and 35°51′S. Relative to the Holocene, isotopically derived SSTs record average changes of +2°C, -2°C, and -2°C for the 59,000-43,000, 43,000-24,000, and 24,000-12,000 yr time slices, respectively. The apparent +2°C warming for the 59,000-43,000 yr period is interpreted to reflect changes in the dominant depth habitat of Globigerina bulloides in response to upwelling. A -2°C cooling of SSTs during isotope stage 2 is interpreted, in part, to reflect upwelling of cool subsurface water resulting from strong and persistent westerly airflow across New Zealand, with the concomitant enhanced surface-water production of CaCO3. Onshore, vegetation consistent with these changes are recorded, with full conifer-hardwood forest prior to 43,000 yr, followed by a change to vegetation implying cooler and drier conditions between 43,000 and 12,000 yr, and a subsequent return to full forest during the Holocene. The sequence of biopelagic and hemipelagic sedimentation observed within these cores reflect oscillation of sea level about a threshold eustatic level that controls the transport of terrigenous detritus offshore. Local variations and interplay of the regional oceanography and morphology and tectonism of the continental shelf will dictate that, relative to present sea level, this threshold eustatic sea level will vary in depth, and hence age, along a continental margin. Data from the New Zealand region reveal an extremely steep meridional thermal gradient across the southern and central New Zealand region during the last glaciation with minor cooling of STW to the north, apart from localized nearshore upwelling zones, but pronounced cooling of subantarctic water to the south of the subtropical convergence zone.