The sequence of glaciation in the midwestern United States has been defined mainly by till stratigraphy. Correlation of tills over long distances, however, is complicated by spatial variation of sediment characteristics. In east-central Minnesota three till units were previously defined. Two were considered to be lithologically identical and were correlated with the late Wisconsin advance of the Rainy lobe, whereas a third till was assigned to the contemporaneous advance of the Superior lobe. This interpretation was inconsistent with subsequent glaciological reconstructions of the Rainy and Superior lobes. In an effort to define the parent lobe of the deposits in central Minnesota, the tills were sampled, analyzed, and compared by graphical and multivariate techniques. Graphical comparisons of sedimentological parameters were inadequate to distinguish important differences among the groups. However, principal component analysis of the analytical data indicates that the original interpretation is untenable and that one of the tills formerly assigned to the Rainlylobe should now be attributed to the Superior lobe. Problems encountered with correlation of tills exposed at the surface illustrate the complexity and problems associated with subsurface stratigraphic correlation.

Evidence from the Boston Harbor drumlins indicates that two superposed tills were deposited during glacier advances which were separated by a long nonglacial interval. At Long and Peddocks Islands, argillans and truncated clay-filled fractures, along with discontinuities in clay-mineral composition, define the till contacts. Physical indicators separating the tills are not apparent at other exposures, where till boundaries were defined solely by discontinuities in clay-mineral composition. The weathering profile in the upper part of the lower till indicates extensive weathering under a climate similar to that of today, and probably similar to that of the Sangamon Interglaciation. The depth of the weathering profile, the sequence of clay-mineral alteration products, and the presence of pedogenic features in the upper part of the lower till are comparable to Sangamonian weathering profiles in the midwestern United States, implying that the lower till is Illinoian or older.

A brief increase in wind intensity between ca. 11,100 and 10,700 yr B.P. is recorded by a sharp increase in sediment grain size at eolian sections along the Nenana River in central Alaska. This occurred at the same time as the Younger Dryas climatic reversal in northern Europe and an increase in the vigor of atmospheric circulation recorded by Greenland ice cores. Climatic fluctuations in high latitude areas during Younger Dryas time may reflect variations in the CO2 content of the atmosphere.

Quaternary lithostratigraphic units in coastal dunes have been dated at three locations in northern Australia, Cobourg Peninsula, Shelburne Bay, and Cape Flattery, by both radiocarbon dating of shell and organic carbon and thermoluminescence (TL) sediment dating. Both coarse fraction and fine fraction TL methods were used. Seventeen TL dates were measured. None of the TL dates contradict the ages given by radiocarbon. Where multiple TL dates were taken from a unit, they overlap within 2 standard deviation giving added confidence in the results. A phase of dune emplacement during the late Holocene (ca. 2700-1800 yr B.P.) was identified in two of the dune-fields, an early Holocene phase of dune emplacement (ca. 8600-7500 yr B.P.) in two of the dune-fields, and a late Pleistocene episode (ca. 24,000–17,000 yr B.P.) in both the Cape York dunefields. Three older units gave dates of about 29,000, 81,000, and 171,000 yr B.P., but these must be treated with caution.

Analysis of stable carbon isotope ratios (13C/12C) of organic matter in land snail shells is used to infer middle Holocene rainfall amounts in the Negev Desert by reconstructing the distribution of C4 plants in the family Chenopodiaceae. The organics are derived from the diet of the snails, which consists of plant material, and are enriched in 13C where C4 plants are present. A survey of modern plant communities indicates that in areas receiving ≥300 mm mean annual rainfall, nearly all plant communities consist of C3 species only (no C4 chenopodes), whereas in areas under ≤230 mm rainfall, most plant communities contain one or more C4 chenopode species. In between is a transition zone consisting of a mosaic of both pure C3 and mixed C3 + C4 plant communities. Isotopic results for fossil land snails indicate a consistent geographic pattern throughout the middle Holocene, from ca. 6500 to 3000 yr B.P., with the transition zone located ca. 20 km south of its present position. This implies a near doubling of rainfall within this region as compared to present.

The late Quaternary vegetation of the semiarid coast of central Chile is inferred from the palynological analysis of profiles from Quereo (31°55′S) and Quintero (32°47′S). Prior to 11,400 yr B.P., wet conditions are suggested by the abundance of pollen indicators of swamp and aquatic taxa, such as Cyperaceae and Myriophyllum, and by the presence of traces of arboreal pollen. Since ca. 10,000 yr B.P., a trend toward increasingly drier conditions is implied by the almost complete absence of arboreal and aquatic taxa, and a general decrease in the diversity of the semiarid shrubland indicators. From 3000 yr B.P. onward, the pollen records show the reappearance of swamp and aquatic taxa, presumably associated with wetter conditions, which led to recolonization by forest taxa at 1720 yr B.P. in Quintero. The drier climate detected along the semiarid coast of central Chile during most of the Holocene extended inland to the Andean foot-hills, within the present mediterranean-type climate zone of Chile, and also affected the distribution of the winter-deciduous Nothofagus forests and the northern boundary of the temperate rain forests.

Two exposures of organic-rich interstadial sediments in central British Columbia provide information on middle Wisconsinan environments and climates near the center of the region subsequently covered by the late Wisconsinan Cordilleran Ice Sheet. Interstadial sediments at Bullion Pit overlie drift of early Wisconsinan or older age and underlie thick drift of late Wisconsinan age. Alluvium (or colluvium) and peat were deposited on the floor of the ancestral Quesnel River valley 46,000–40,000 14C yr ago when the vegetation consisted of spruce forest with dry openings and local fens and the climate was colder and perhaps drier than today. This is broadly consistent with paleoclimatic reconstructions for the same time interval for Babine Lake, 400 km to the northwest, and for Meadow Creek, 400 km to the southeast. Plant-rich pond sediments containing tephra layers and vertebrate remains are exposed between two drifts in a ravine at Mexican Hill, 30 km east of Quesnel. Although they may be contemporaneous with the Bullion Pit beds, the nonglacial sediments at Mexican Hill more likely were deposited sometime after the warmest part of the last interglaciation, but prior to 50,000 yr B.P. At that time, the vegetation at Mexican Hill probably was parkland. The present vegetation at Mexican Hill is boreal forest; thus, a drier and possibly cooler climate is indicated.

Two radiocarbon-dated cores from small lakes located approximately 25 km north of the mapped boundary between forest-tundra and tundra provide records of postglacial vegetation change at the treeline near Yellowknife, NWT, Canada. Basal radiocarbon dates of 6180 and 7470 yr B.P. were obtained from the cores. The fossil pollen evidence suggests that the initial vegetation was Betula tundra with a peatland component. Alnus became an important constituent of the pollen assemblages between 6900 and 5500 yr B.P. Both lakes record sharp increases in Picea cf. mariana pollen at approximately 5000 yr B.P., suggesting the establishment of forest-tundra. By 3500 yr B.P. Picea mariana forest-tundra had withdrawn. The proportion of organic to inorganic sediment in the cores was at a maximum between 5000 and 3500 yr B.P. Tundra has dominated the region since 3500 yr B.P. In northwestern Canada, the maximum northward advance of treeline occurred between 9000 and 5000 yr B.P. The asynchrony in treeline advance in central and northwestern Canada may reflect that glacial ice persisted in the interior NWT longer than previously believed. Alternatively, the asynchronous history of the treeline may be a result of the geometric properties of the long-wave westerly disturbance that is manifest in the median summer position of the arctic front and ultimately controls the geographic location of the treeline.

Torrential rainfalls in the Rokko Mountains have often triggered severe landslides and debris flows, but few such phenomena have occurred in the area just to the north of the mountains during the same rainfall events. The periodicity of 25–30 years in excess rainfall data (i.e., the annual summation of heavy rainfall of more than 100 mm/day during the past 100 years) around the mountains correlates with the increased frequency of landslides and debris flows. Analyses of tree-ring widths that span the past 50–240 years in samples taken from various areas in the mountains and the area just to the north indicate that most sequences have a dominant periodicity of about 25–30 years, the ring series in the mountain areas having a more conspicuous periodicity than those from the area just to the north. These results lead to the conclusion that excess rainfall may provide a first approximation of erosional force in areas affected by slope movement, and that tree-ring width may be used as a proxy for erosional force.

A series of 50 packrat midden assemblages from the Big Bend region of the Chihuahuan Desert, ranging in age from >36,000 yr B.P. to recent, yielded abundant, diverse arthropod faunas. The mesic nature of regional Wisconsin age climates is substantiated by the fauna from 30,000–12,000 yr B.P., especially during the middle Wisconsin (30,000–20,000 yr B.P.). Late Wisconsin faunas contained grassland species which are confined today to cooler, moister regions. Following 12,000 yr B.P., most of these temperate species were replaced either by desert species or by more cosmopolitan taxa, marking the climatic shift from late Wisconsin to postglacial time. Insects indicative of more severe aridity are first recorded at about 6000 yr B.P., but some temperate species persisted until about 2500 yr B.P. After this, only desert dwellers are recorded.