Postglacial precipitation δ18O history has been reconstructed for two regions of Canada. Long-term shifts in the oxygen-isotope composition of annual precipitation (δ18Op) in southern Ontario appear to have occurred with a consistent isotope–temperature relation throughout the past 11,500 14C yr. The modern isotope–temperature relation in central Canada near present boreal treeline evidently became established between 5000 and 4000 years ago, although the relation during the last glacial maximum and deglaciation may also have been similar to present. In the early Holocene, however, unusually high δ18Op apparently persisted, in spite of low temperature locally, probably associated with high zonal index. A rudimentary sensitivity analysis suggests that a small reduction in distillation of moisture in Pacific air masses traversing the western Cordillera, perhaps accompanied by a higher summer:winter precipitation ratio, could have been responsible for the observed effect. Equivalent isotope–temperature “anomalies” apparently occurred elsewhere in western North America in response to changing early-Holocene atmospheric circulation patterns, suggesting that a time-slice map of δ18Op for North America during this period might provide a useful target for testing and validation of atmospheric general circulation model simulations using isotopic water tracers.

High-resolution paleomonsoon proxy records from peat and eolian sand–paleosol sequences at the desert–loess transition zone in China denote a rapid oscillation from cold–dry conditions (11,200–10,600 14C yr B.P.) to cool–humid conditions (10,600–10,200 14C yr B.P.), followed by a return to cold–dry climate (10,200–10,000 14C yr B.P.). Variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern Asia during the Younger Dryas interval. Late-glacial climate in the Chinese desert–loess belt that lies downwind from Europe was strongly influenced by cold air from high latitudes and from the North Atlantic via the westerlies. The inferred precipitation variations were likely caused by variations in the strength of the Siberian high, which influenced the pressure gradient between land and ocean and therefore influenced the position of the East Asian monsoon front.

Stable isotopes, geochemical, lithological, and micropaleontological results from cores from the far northwest (FNW) Pacific and the Okhotsk and Bering seas are used to reconstruct the regional environment for the last glaciation, the deglacial transition, and the Holocene. δ18O records of planktonic foraminifera of the region show two “light” shifts during deglacial time, provoked by the freshening of the surface water and climate warming. These north Pacific terminal events (T1ANP and T1BNP) with ages of 12,500 and 9300 yr B.P., respectively, occur almost simultaneously with two episodes of accelerated glacier melting around the North Atlantic. Along with the isotopic shifts, the CaCO3 content in regional sediments increased abruptly (1A and 1B carbonate peaks), probably due to changes of productivity and pore water chemistry of surface sediments. Organic matter and opal concentration increased during the transition (between T1ANP and T1BNP events) in the sediments of the FNW Pacific and the southern part of the Bering Sea and opal content increased in the Holocene in the Bering and Okhotsk Seas. δ13C records of cores from the Okhotsk and Bering seas and the FNW Pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation. During deglaciation, accumulation of the coarse terrigenous component decreased in sediments of the Bering Sea and the FNW Pacific before the T1ANP event, probably as a result of rising sea level and opening of the Bering Strait.

A new and significant site of organic silty sand has been found beneath the Valders till at Valders Quarry in northeastern Wisconsin. This is now the earliest known late-glacial site associated with red till ice advances in the western Great Lakes area. Leaves of terrestrial plants washed into a small depression provide a date of 12,965 ± 200 yr B.P. (WIS-2293), which is significantly older than the Two Creeks Forest Bed (ca. 11,800 yr B.P.). Percentage and concentration pollen diagrams suggest that the site was open and distant from a closed Picea forest. No wood or Picea needles have been found. This date is statistically indistinguishable from 12,550 ± 233 yr B.P., the mean of three dates for the end of inorganic varve sedimentation at Devils Lake, 160 km southwest at the terminus of the Green Bay Lobe. Assuming that the Green Bay lobe vacated its outermost moraine in the interval from 13,000 to 12,500 yr B.P., only a short time was available for retreat of the ice margin over 350 km, drainage of red sediment from Lake Superior into the Lake Michigan basin, readvance of over 250 km, retreat of at least 80 km, and advance to this site. The time for these events appears to have been too short to resolve by current radiocarbon technique. This extremely rapid collapse of the Green Bay lobe has a calibrated age of about 15,000 cal yr B.P., about that of the dramatic warming seen in the Greenland ice cores.

Climatic reconstruction of glacial to interglacial episodes from oxygen isotopes in sediment cores from the Nordic seas is complicated by strong local meltwater contributions to the oxygen isotope changes. Combination of benthic and planktic foraminiferal isotope data with foraminiferal abundances and ice-rafted debris (IRD) allows separation of local and global effects and subdivision of the marine oxygen isotope events 6.2–5.4, which include the last interglaciation, into: (1) a meltwater phase after glacial stage 6, recorded by large amounts of IRD and low foraminiferal abundance, indicating surface water warming; (2) an IRD-free period with high deposition rates of subpolar foraminifera and other CaCO3 pelagic components, recognized here as the “full” interglaciation; and (3) a phase with the recurrence of IRD and the demise of subpolar species. Comparison of ice-core records and marine data implies that the global climate during the last full interglaciation and that during the postdeglacial Holocene were similar. The records show no significantly different variations in the proxy data. In contrast, the oxygen isotopes of planktic foraminifera and ice cores indicate significant differences during each of the deglacial transitions (Terminations I and II) that preceded these two interglaciations. These suggest that during Termination II the climatic evolution in the Nordic seas was less affected by abrupt changes in ocean–atmosphere circulation than during the last glacial to interglacial transition.

Mordern alluvial pollen varies with geomorphic setting and depositional facies in sediments of the Yellow, Hutuo, and Luan rivers and in Baiyangdian and Hengshuihu lakes. Most of the arboreal pollen is derived from the mountains, whereas most of the nonarboreal pollen is derived from the plain itself. Alluvium dominated by Pinus pollen and Selaginella spores was deposited during a flood. Hydrodynamic sorting of alluvial pollen exists in the sediments of floodplain, central bar, natural levees, and point bar. In reconstructing the ancient vegetation and past climate based on pollen in alluvium, it is important to consider sedimentary facies and geomorphologic setting.

The mid-Holocene eastern hemlock [Tsuga canadensis L. (Carr.)] decline has been recently attributed to the activity of insect defoliators. N. Bihiry and L. Filion, Quaternary Research 45,312–320 (1996). In this study, soil hydromorphic conditions were investigated for the period 6800–3200 yr B.P. using micromorphological data from a peat section from a swale in a paludified dunefield in southern Québec. After a short period of plant colonization in shallow pools between 6800 and 6400 yr B.P., mesic conditions predominated in the interdune before the decline (6400–4900 yr B.P.), as evidenced by strong bioturbation and abundance of excrements from the soil fauna. During the decline, a shift from mesic to wet conditions occurred (4900–4100 yr B.P.), although xeric to mesic conditions persisted on dune ridges until at least 4200 yr B.P. Wetness culminated when beaver occupied the site (4100–3750 yr B.P.). Hemlock needles with chewing damage typical of hemlock looper (Lambdina fiscellaria) feeding were identified at levels dated 4900, 4600, and 4200 yr B.P., respectively, implying that the hemlock decline was associated with at least three defoliation events. The ca. 400-yr interval between these events likely represents the time required for this late-sucessional tree species to recover.

An exceptionally rich paleontological site containing thousands of mammalian fossils and well-dated with 18 radiocarbon samples provides evidence of late-Holocene ecological response to climatic change in northern Yellowstone National Park, Wyoming. The mammalian fauna, composed of 10,597 identified specimens, shows surprising affinity to the local habitat with little evidence of long-distance transport of faunal elements, thus revealing the faithfulness of a fossil site to the community from which it is derived. The mammals illustrate ecological sensitivity to a series of mesic to xeric climatic excursions in the sagebrush-grassland ecotone during the past 3200 yr. From 3200 cal yr B.P. to a maximum of 1100 cal yr B.P., the species composition of mammals indicates wetter conditions than today. Beginning about 1200 cal yr B.P., the fauna becomes more representative of xeric conditions with maxima in xeric-indicator taxa and minima in mesic-indicator taxa, concordant with the Medieval Warm Period (circa 1000 to 650 yr B.P.). Cooler, wetter conditions which prevailed for most of the Little Ice Age (700 to 100 yr B.P.) in general correspond to a return to a more mesic mammalian fauna. A warm period within the Little Ice Age is documented by a xeric fauna. These data show that mammalian ecological sensitivity to climatic change over this intermediate time scale holds promise for predictions about the impacts of future global warming.

Mutual Climatic Range (MCR) analysis was applied to 20 fossil beetle assemblages from 11 sites dating from 14,500 to 400 yr B.P. The fossil sites represent a transect of the Rocky Mountain region from northern Montana to central Colorado. The analyses yielded estimates of mean July and mean January temperatures. The oldest assemblage (14,500 yr B.P.) yielded mean July values of 10–11°C colder than present and mean January values 26–30°C colder than present. Postglacial summer warming was rapid, as indicated by an assemblage dating 13,200 yr B.P., with mean July values only 3–4°C cooler than modern. By 10,000 yr B.P., several assemblages indicate warmer-than-modern mean summer and winter values. By 9000 yr B.P., MCR reconstructions indicate that both summer and winter temperatures were already declining from an early Holocene peak. Mean July values remained above modern levels and mean January values remained below modern levels until 3000 yr B.P. A series of small-scale oscillations followed.

The Kärlich–Seeufer archaeological site in Germany's central Rhineland was excavated between 1980 and 1992. The site provides evidence for hominid activity during a Middle Pleistocene interglaciation known up to now only from the Kärlich clay pit and therefore defined as the Kärlich Interglaciation, which is considered to be post-Cromer IV and pre-Holstein (sensu stricto) in age. The site is characterized by Acheulean artifacts, a fauna dominated by Elephas (Palaeoloxodon) antiquus, and a unique and outstanding preservation of wooden and other palaeobotanical remains. Assuming all finds are associated, the site previously was interpreted as an elephant hunting camp with a wooden structure, together with wood and bone implements preserved in situ. Recent analysis of the same features has shown that the site can also be interpreted as a reworked archaeological sample. Hominid occupation occurred in the vicinity of a small lake with prevailing meso-oligotrophic conditions. Expanding boreal forests and fen vegetation characterized the landscape.

New sea-level and δ18O curves for the past 34,000 yr, based on uranium–thorium chronology, are proposed for the southwestern part of the Indian Ocean. The archives include cores drilled from onshore coral reefs and submersed samples from foreslope corals of Mayotte in the Comoro Islands. The Mayotte sea-level curve shows a lowstand of 145 ± 5 m below the present level during the last glacial maximum dated at 18,400 yr. This lowstand is supported by the maximum18O enrichment in the coral colonies. The residual signal (Δδ18O), controlled by sea-surface temperature changes, indicates that surface waters 18,400 yr ago were approximately 5°C cooler than present. The deglacial sea-level rise is clearly recorded, with a mean rate of about 1.7 cm yr−1between 18,400 and 10,000 yr ago. The deglaciation phase is characterized by a strong18O depletion marked by two pulses related to meltwater discharges into the North Atlantic Ocean but also characterized by responses specific to the tropical Indian Ocean.