Areas of southeastern Alaska and the Queen Charlotte Islands of the northwestern Pacific coast of North America were considered to be ice free during the late Wisconsinan glaciation and glacial refugia existed. However, a glacier extended from mainland North America to the shelfbreak in Dixon Entrance separating Alaska and the Queen Charlotte Islands. Glacial retreat to the east began sometime after 15,000 to 16,00014C yr B.P. and ice had completely left Dixon Entrance by 13,500 to 13,00014C yr B.P. A rapid sea-level regression occurred soon after deglaciation began, due to isostatic rebound, with relative sea level falling to approximately 150 m below present in central Dixon Entrance, decreasing the size of the inlet by about 30 percent by 12,40014C yr B.P. The late Quaternary glacial and postglacial stratigraphic sequence is more than 100 m thick overlying older Pleistocene sediments and Tertiary bedrock. A late Wisconsinan diamicton is overlain by glaciomarine muds formed between approximately 14,400 and 13,00014C yr B.P. Contemporaneous with the deposition of the glaciomarine muds an extensive outwash deposit formed off the northern coast of the Queen Charlotte Islands to a present depth of 150 m. During the sea-level lowstand and subsequent transgression, a reworked sand unit was deposited over much of the seafloor to depths greater than 450 m. The unit is exposed at the seafloor over much of the region, suggesting that seabed hydrodynamic energy levels were high after 13,00014C yr B.P. and remain so today.

Geomorphic features inherited from the mid-Holocene glacio-hydro-isostatic sea-level highstand that affected the central Pacific region influence the susceptibility of atoll islets to potentially enhanced wave erosion associated with rise in sea level from global warming. Shoreline morphology on multiple islets of Funafuti atoll in central Tuvalu reflects a relative mid-Holocene sea-level highstand 2.2–2.4 m above modern sea level. Typical islets are composed of unconsolidated post-mid-Holocene sediment resting disconformably on cemented coral rubble formed beneath now-emergent mid-Holocene reef flats. Exposed remnants of the lithified islet foundations serve as resistant buttresses protecting the flanks of atoll islets from wave attack. Islets lacking cemented mid-Holocene deposits as part of their internal structure are migratory sand cays with unstable shorelines. Any future sea-level rise ≥0.75 m, bringing high tide above the elevation of mid-Holocene low tide, might trigger enhanced wave erosion of stable atoll islets by overtopping the indurated mid-Holocene reef platforms. As analogous threshold relations are inferred for other central Pacific atolls, the risk of future inundation of island nations cannot be evaluated solely in terms of expected sea-level rise with respect to gross islet elevations.

A late-glacial to early Holocene record of pollen, plant macrofossils, and charcoal has been obtained from two cores from Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed on the overall warming trend from 14,200 to 750014C yr B.P. This site had cold, moist conditions from ca. 14,200 to 12,70014C yr B.P., with warming at 12,730, 11,280, and 10,05014C yr B.P. A decrease in deciduous broad-leaved tree taxa andPinus strobus(haploxylon) pollen, simultaneous with a reexpansion ofAbies,denotes a brief, cold reversal from 12,260 to 12,20014C yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 750014C yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland and northwestern Europe. Warming at 11,28014C yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.

δ18O values of sulfate minerals from a 186-m core (past 200,000 years) in Death Valley varied from +9 to +23‰ (V-SMOW). Sulfates that accumulated in the past ephemeral saline lake, salt pans, and mud flats have relatively low δ18O values similar to those of present-day local inflows. Sulfates that accumulated during two perennial lake intervals, however, have higher δ18O values, reflecting changes in temperature, lake water levels, and/or sulfur redox reactions. Over the same time interval, the δ18O record for sulfate had excursions that bear similarities to those found for carbonate in the Death Valley core, marine carbonate (SPECMAP), and polar ice in the Summit ice core, Greenland. The δ18O record differed considerably from the records reported for carbonate at Owens Lake and Devils Hole, which probably relates to different water sources. Death Valley, Owens Lake, and Devils Hole are responding to the same climatic changes but manifesting them differently. In Death Valley sediments, the isotopic composition of sulfate may have potential as an indicator of paleoenvironmental changes.

We estimated minimum mean July temperatures in northwestern and central Europe during the Younger Dryas (10,950–10,15014C yr B.P.) from distributions of climate indicator plant species, which were reconstructed from 140 pollen and plant macrofossil diagrams. Paleobotanical records, mainly from the central and eastern part of the study area, show that the coldest conditions occurred early in the Younger Dryas (before ∼10,55014C yr B.P.). For this phase, mean July temperatures at sea level of around 10°C are suggested for the northern part of the British Isles and for ice-free Scandinavia. We estimated a mean July temperature of 12°C for central England, The Netherlands, and northern Germany. The 13°C mean July isotherm—largely based on the modern distribution ofTypha latifolia—was most probably located in southern England, Belgium, central Germany, and Poland. The reappearance of thermophilous elements in the records after ∼10,55014C yr B.P. suggests a summer warming, at least temporarily, of 1° to 2°C in the study area. The reconstructed temperatures are comparable with temperature estimates based on beetle data. However, they appear rather high when compared with estimates based on glaciological evidence.

Walpole Island is part of a large freshwater delta located at the St. Clair River mouth in southwestern Ontario. Quaternary deposits on the island consist of Lake Nipissing to Lake St. Clair stage deltaic sediments underlain by a thick sequence of Late Wisconsin glaciolacustrine rhythmites and massive clayey till. These sediments overlie a thin freshwater aquifer resting on Paleozoic bedrock. Porewater δ18O, δD, and δ13CDICprofiles of cores taken from northern and central Walpole Island show that older (>10,000 yr B.P.), deeper glaciogenic porewaters have mixed with, and have been displaced by, younger modern surficial water. In contrast, isotopic profiles from a core taken from southern Walpole Island indicate that modern St. Clair River waters have penetrated the entire 20-m core via fractures, effectively displacing all glaciogenic porewater. Fracturing and faulting are clearly visible throughout the southern core, and their presence may be attributed to its location on the trend of the Electric Fault. These features are interpreted as the product of renewed Holocene fault movement. Porewater Na+, K+, Ca2+, and Mg2+concentration gradients are consistent with the presence of upwardly diffusing deep brine, for which the Electric Fault may serve as a conduit.

The reliability of paleovegetation records inferred from soil phytolith assemblages and SOM (soil organic matter) carbon isotope analysis was examined in light of previous pollen and charcoal reconstructions. The sampled latosol is located in south-central Brazil (Salitre), at a boundary between forest and cerrado. The derived mean age of phytoliths and SOM at each level is the result of a balance between continuous translocation and selective dissolution. It increases with depth in a regular, quantifiable fashion that allows paleoenvironmental interpretation. Phytoliths and SOM tracers first record a savanna phase, associated with the last Holocene long dry period occurring between ca. 5500 and 4500 yr B.P. Two periods of tree community development followed, between ca. 4000 and 3000 and after ca. 970 yr. B.P., leading to the present cerrado/forest association. The dry spell interrupted this trend about 970 ± 60 yr B.P. The second development of woody elements was contemporaneous with an increase in anthropogenic fires. Therefore, climate was more important than fires and human activities in constraining the growth of vegetation during the last nine centuries at Salitre. More generally, despite pedogenic processes, soil phytoliths and δ13C values of the SOM may be accurate tracers of vegetation changes.

Diring Yuriakh, an archaeological site on the highest terrace of the Lena River in subarctic eastern Siberia, provides evidence for the oldest and northern-most Early Paleolithic occupation in Asia. Stratigraphic and sedimentological studies at the site show that artifacts occur on a single eolian deflation surface that is underlain by fluvial sediments with inset cryogenic sand wedges and overlain by eolian deposits. Thermoluminescence ages on the fine-grained extracts from the eolian sediments and sand wedges that bound the artifact level indicate that the occupation occurred >260,000 yr B.P. and may possibly date between 270,000 and 370,000 yr B.P. This study documents that the artifacts from Diring Yuriakh are an order of magnitude older than artifacts from any previously reported site from Siberia. The antiquity and subarctic location of Diring Yuriakh indicates that people developed a subsistence strategy capable of surviving rigorous conditions in Siberia by ≥260,000 yr B.P.