Piston cores from the South Orkney Plateau penetrated overcompacted diamictons in water depths of up to 250 m. Detailed textural and petrological analyses of these diamictons indicate that they are basal tills. Seismic records from the plateau show a widespread surface of glacial erosion and provide additional evidence of an ice cap grounded to a depth of 250 m. Piston cores from the slope of the plateau penetrated diatomaceous muds resting directly on poorly sorted muds with very little to no biogenic material. The ice-rafted debris in these glacial-marine sediments is composed almost exclusively of material derived from the South Orkney Islands. This implies deposition beneath an ice shelf as opposed to iceberg rafting. In contrast, diatomaceous muds contain relatively abundant exotic iceberg-rafted material and reflect a glacial-maritime setting similar to that of today. The sharp contact separating diatomaceous surface sediments from basal tills and sub-ice shelf deposits indicates that the ice cap and ice shelf retreated from the plateau rapidly. Radiocarbon dates for diatomaceous muds from a glacial trough on the plateau indicate that the ice cap and ice shelf retreated from the plateau prior to 6000 to 7000 years ago. The homogeneity of surficial diatomaceous sediments suggests that sea ice conditions over the plateau have not changed radically since that time.

The most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to between about 3500 and 3800 yr. The set originated at Hayes volcano in the Tordrillo Mountains 150 km northwest of Anchorage; seven or possibly eight closely succeeding deposits, low-silica dacite in composition, compose two main lobes that extend northeast for 400 km and south for at least 250 km from the vent. We estimate the total tephra volume to be 10 km3; multiple layers imply four to six larger and two or three smaller eruptions. The deposits are a nearly isochronous marker horizon that should be useful in future archeologic, geologic, and palynologic studies in the region.

The Stansbury shoreline, one of the conspicuous late Pleistocene shorelines of Lake Bonneville, consists of tufa-cemented gravel and barrier beaches within a vertical zone of about 45 m, the lower limit of which is 70 m above the modern average level of Great Salt Lake. Stratigraphic evidence at a number of localities, including new evidence from Crater Island on the west side of the Great Salt Lake Desert, shows that the Stansbury shoreline formed during the transgressive phase of late Pleistocene Lake bonneville (sometime between about 22,000 and 20,000 yr B.P.). Tufa-cemented gravel and barrier beaches were deposited in the Stansbury shorezone during one or more fluctuations in water level with a maximum total amplitude of 45 m. We refer to the fluctuations as the Stansbury oscillation. The Stansbury oscillation cannot have been caused by basin-hypsometric factors, such as stabilization of lake level at an external overflow threshold or by expansion into an interior subbasin, or by changes in drainage basin size. Therefore, changes in climate must have caused the lake level to reverse its general rise, to drop about 45 m in altitude (reducing its surface area by about 18%, 5000 km2), and later to resume its rise. If the sizes of Great Basin lakes are controlled by the mean position of storm tracks and the jetstream, which as recently postulated may be controlled by the size of the continental ice sheets, the Stansbury oscillation may have been caused by a shift in the jetstream during a major interstade of the Laurentide ice sheet.

Inasmuch as soils are open systems and rarely, if ever, achieve equilibrium with their environments, it is philosophically sound to view all soils as expressing varying levels of polygenesis as that term has been redefined. Soil genesis and resultant morphology may then be viewed in a comprehensive framework of soil evolution that consists of two linked pathways, one developmental and the other regressive, that reflect interactions of both exogenous and endogenous vectors (vectors are factors, processes, and conditions of pedogenesis). Following this philosophy, a model of pedogenesis is framed in an evolutional paradigm that emphasizes the integrated effects of dynamic and passive pedogenic vectors in directing pathways and in controlling rates of soil genesis through time. The dynamic vectors include energy and mass fluxes, frequencies of soil wetting and drying, water table dynamics, organisms, feedback processes, and pedoturbation. The passive vectors include parent materials, soil chemical environment, stability of geomorphic surfaces, and various evolved soil properties and conditions (accessions). Both sets of vectors vary spatially, and the dynamic vectors, more so than passive vectors, fluctuate through time. The model is expressed as S=f(D,P,dD/dt,dD/dt) where S is the state of the soil or degree of profile evolution, D is the set of dynamic vectors, P is the set of passive vectors, and dD/dt and dP/dt denote change through time t. The model helps explain the apparent minimal development and regressed character of some old soils and the rapid and strong development of some young ones.

A paleoclimatic reconstruction for the past 35,000 years for northern Oman is based on an unusual approach using travertines and fracture calcites associated with hyperalkaline springs. High-pH groundwaters (pH up to 11.9) discharge from the mantle sequence of the Oman Ophiolite as the product of modern, low-temperature serpentinization. Under arid climatic conditions, hyperalkaline discharge occurs at the surface. Uptake of atmospheric CO2 precipitates characteristic laminated travertines, accompanied by strong kinetic depletion of 13C and 18O. Pluvial climates supporting a shallow bicarbonate-groundwater flow system and vegetation are recorded by fracture calcites with equilibrium stable isotope contents and calcite-replaced roots and stems. All such carbonates have modern initial 14C contents, allowing radiocarbon dating and paleoclimatic reconstruction for the late Pleistocene and Holocene. Our reconstruction shows a dominantly wet late Pleistocene up to 19,000 yr B.P., when a phase of climatic deterioration began, leading to a period of hyperaridity which dominated from ca. 16,300 to 13,000 yr B.P. The early Holocene pluvial occurred from 12,500 to ca. 6500 yr B.P. and was followed by renewed climatic deterioration and the current phase of hyperaridity. Comparison of this paleoclimatic reconstruction with that for lacustrine deposits from the A'Rub al Khali of central Saudi Arabia and the summer insolation-driven monsoon record of east Africa and the Arabian Sea is remarkably good.

Annual (October through September) precipitation from 1100 A.D. to modern times is reconstructed for Morocco, using Cedrus atlantica (Endl.) Carrière tree-ring chronologies. Both multiple regression on principal components and the bootstrap method are use to calibrate tree-ring width with precipitation; precipitation variation is reconstructed for three climatically distinct areas: the humid, subhumid, and arid regions of Morocco. A series of successive wet and dry periods is identified for the past 1000 years; the maximum length of the 13 dry periods (during which precipitation was at least 1σ below normal) is 6 years. Twenty-one years are identified during which precipitation fell more than 2σ below normal. We are unable to identify significant correspondence in climatic variation in Morocco, Europe, and the Sahel during this time period.

Two distinct elevations of emerged notches can be recognized on the southeastern coast of Vanua Levu: the higher notch is +2.22 to +3.30 m above low-tide level and the lower +1.52 to +1.65 m above low-tide level. Many emerged Holocene corals encrust higher notch floors and benches or occur as microatolls and from these radiocarbon ages ranging from 6000 to 3400 yr B.P. were obtained. The higher notches are significantly higher than present high-tide level, even allowing for relative tectonic uplift. This is supported by elevations of emerged microatolls and their 14C ages. Thus, mean sea level of the mid-Holocene was higher than that at present.

The degree of analogy between fossil and contemporary pollen spectra in Europe has been investigated using the chord-distance dissimilarity measure. No-analog pollen spectra represent vegetation without a modern analog and hence, by inference, represent macroclimatic conditions different from any occurring in the region today. Such spectra have minimum chord distances that exceed a threshold value assessed using contemporary samples from the same and different vegetation u units. Contoured maps of minimum chord distance portray the changing patterns of analogous and no-analog pollen spectra, and hence vegetation units, since 13,000 yr B.P. No-analog vegetation units have been extensive in some regions for much of the Holocene, persisting as recently as 1000 years ago in many areas. The chord-distance measure has also been used to explore the patterns, extent, and rates of change in European pollen spectra since 13,000 yr B.P. Pollen spectra changed rapidly during late-glacial and early Holocene times and during the last millennium. Paleoclimatic changes have brought about the major changes in the Holocene paleovegetation of Europe. Human impact upon European vegetation has obscured neither the contemporary relationship between pollen spectra and vegetation nor the climatically determined long-term changes of vegetation across the continent since 13,000 yr B.P.

Mean long-term rates of peat accumulation are higher in boreal and temperate peat deposits than in subarctic regions of Canada, although peatlands are extensive in the subarctic. Climatic change probably accounts for the development of southern peatlands during the middle to late Holocene and for the late Holocene decline in growth of many subarctic peat deposits. In northwestern peat deposits, peat of wet Sphagnum lawns and treed wetlands tended to accumulate more rapidly than peat of Sphagnum hummocks and sedge fens. Long-term net rates of carbon accumulation in Canadian peatlands typically range from 10 to 35 g C/m2/yr.

Organic material exposed within a small swale fill in Pit 6 of the Wedron Silica Sand Co. near Wedron in LaSalle County, Illinois, includes well-preserved pollen, plant macrofossils, and insect remains. This material occurs in slackwater sediment in the lower part of the Peddicord Formation, which was deposited as existing valleys were dammed by fluvial aggradation during the initial late Wisconsinan advance of Laurentide ice into the Wedron area. Wood from the organic horizon has a radiocarbon age of 21,460 ± 470 yr B.P. (ISGS-1486). The pollen spectrum is dominated by Picea, Pinus, and Cyperaceae. Plant macrofossils comprise a mix of boreal-forest taxa, including Picea, Larix laricina, and the moss Campylium stellatum; subarctic species including Betula glandulosa, Empetrum nigrum, and Selaginella selaginoides; along with the predominantly arctic Vaccinium uliginosum var. alpinum, Dryas integrifolia, and Rhododendron lapponicum. The insect fauna contains the western montane ground beetle Opisthius richardsoni; several arctic-subarctic ground beetles including Diacheila polita, Helophorus sibiricus, and Pterostichus (Cryobius) caribou; and a diverse assemblage of insects that today inhabit the boreal forest. We interpret the biotic record to record a phase in the transition from closed boreal forest to open tundra as climatic conditions deteriorated in advance of continental glaciation.

Pollen analysis of a 14,000-yr-old sediment core from Sithylemenkat Lake provides the first Holocene vegetational history for the Kanuti Flats of north-central Alaska. Basal samples contain a curious and unusual combination of tundra and boreal taxa. Pollen assemblages dating from 13,500 to 9000 yr B.P. are more typical of southern Brooks Range sites and indicate the presence of Betula shrub tundra with increased Populus ca. 10,000 to 9000 yr B.P. Picea glauca appeared ca. 9000 yr B.P. and Alnus ca. 8000 yr B.P. P. glauca populations declined between 7800 and 5000 yr B.P. with a subsequent reforestation by P. mariana and P. glauca. This pattern is seen at other sites in northeastern Alaska and suggests that the Holocene history of boreal forest is more complex than thought previously.