Analyses of Quaternary landscape evolution tend to focus on events associated with culminations of glacial and interglacial ages, but for most of Quaternary time, environments were intermediate in character. Average Quaternary glacial conditions, based on assessment of the marine isotope record, approximated those near the stage 2/stage 1 transition and during substages 5b and 5d; isotope stages 3 and 4 and substages 5a-d lie within one standard deviation of the mean value. Under average glacial conditions, ice sheets lying over northern North America and Europe were much more contracted than their full-glacial counterparts, and the distribution of mountain glaciers reflected a snowline depression of some 500 m. Geomorphic processes operating under average Quaternary conditions contributed importantly to landscape evolution. Examples of landscapes that may represent such average conditions include cirques and fluvial deposits of the Pacific Northwest, the fjords and strandflat of western Norway, and atolls of the tropical oceans. By examining the geologic record from the perspective of average conditions, rather than those of climatic extremes, added insight can be gained regarding the evolution of Quaternary landscapes.

Variation in the size of lakes in the Lahontan basin is topographically constrained. River diversion also has played a major role in regulating lake size in Lahontan subbasins. The proper gage of lake response to change in the hydrologic balance is neither lake depth (level) nor lake volume but instead lake-surface area. Normalization of surface area is necessary when comparing surface areas of lakes in basins having different topographies. To a first approximation, normalization can be accomplished by dividing the paleosurface area of a lake by its mean-historical, reconstructed surface area.

Numerical and calibrated age determinations of the late Quaternary alluvial fan deposits of the Soda Mountains piedmont in the Mojave Desert provide an opportunity to study the utility of the multiparameter relative-age (RA) method for distinguishing and mapping geomorphic surfaces on a desert piedmont. Most RA parameters could not discriminate between deposits of Holocene age, although pavements have formed over locally significant parts of surfaces as young as middle Holocene. Several parameters, including lithologic composition, particle size, soil development, and varnish cover, permit distinguishing between Holocene surfaces and late Pleistocene surfaces. Statistically significant differences in initial particle size and lithology of the deposits, inferred to be the result of complex interaction among hillslope, alluvial fan, and eolian processes and climatic change, create conditions unfavorable for use of most RA techniques. In contrast, soil-profile development and varnish cover data are successful in discrimination among deposits of Holocene and Pleistocene age. This is attributed to the development of pedogenic features and varnish that are strongly dependent on dust influx and to the relatively minor dependence of these features on differences in the depositional character of the fan.

The rates of CaCO3 formation in desert soils of the American Southwest are highly variable and potentially useful in estimating the age of soil profiles. The objective of this study was to examine the correlation between the long-term rate of CaCO3 formation (LTR) and modern mean annual precipitation (MAP) and temperature (MAT). LTR is not significantly related to temperature but is linearly related to MAP [LTR = 0.0150(MAP − 37), r 2 = 0.924]. The slope of the regression is significantly different from 0.0 and is equivalent to a calcium concentration of 6.0 mg liter−1 in rainfall. However, the intercept term, which suggests a lower limit of precipitation for CaCO3 formation of 37 mm, is not significantly different from 0.0. The LTR-MAP relationship may be useful in estimating the age of soil profiles by the CaCO3 method in the desert Southwest.

Eight marine transgressions have been recognized from more than 30 deep drill holes (ca. 300 m deep) through Quaternary sequences in the Yangtze River delta region. These are, in ascending order, the Rugao and Zhoupe transgressions (early Pleistocene); the Shanghai, Jiading, and Wangdian transgressions in the middle Pleistocene; the Jiangyin and Gehu transgressions in the late Pleistocene; and the Zhenjiang transgression in the Holocene. The transgressions correspond to warm periods and regressions to cold periods. The younger transgressions were not only of shorter duartion, but also of larger magnitude. The findings verify that there were five moderately warm periods during the early to middle Pleistocene and two very warm periods during the late Pleistocene in the Yangtze River delta region.

White-tailed deer (Odocoileus virginianus) from central Illinois varied in size during the Holocene. The record, which extends back to 8450 yr B.P., indicates small deer through the mid-Holocene until 3650 yr B.P., after which size increases. Although influences of winter climate, seasonality, anthropogenic effects, and other ecological factors should not be discounted, an intriguing possible cause of the deer size shifts is insolation-driven summer climate and its influence on food resources. In the Holocene, small deer size is correlated with high summer insolation and with low winter insolation. Climatic models indicate that in spite of changes in insolation, Holocene winters did not vary greatly through time, especially in contrast to summers, which were dynamic. Physiological constraints peculiar to O. virginianus make critical the quality of summer forage for determining final adult size. Summer temperature averaged 2°C warmer than present during the middle Holocene, which increased evaporation and probably reduced the period of availability of high-quality forage low in fiber and high in protein. Consequently, less fuel for growth was consumed by mid-Holocene deer and only small body size was achieved. Other possible causes (e.g., Bergmann's rule, seasonality) of clinal variation are considered with reference to central Illinois deer, but at present the most parsimonious explanation appears to be the summer insolation hypothesis.

Pollen and phytogeographic evidence provides a vegetational history of the Sahel for the period 0–18,000 yr B.P. The zonal vegetation fluctuated latitudinally and its most extreme positions occurred at 18,000 and 8500 yr B.P. The first involved a southward shift of the Sahelian wooded grassland to 10°N under the arid conditions of the last glacial maximum. The second change shows a rapid northward migration of humid vegetation: Guinean elements reach 16°N and Sahelo-Sudanian elements extend to the southern margin of the modern Sahara (21°N) when the Atlantic monsoon flux increased. In the middle Holocene the extensive spread of Sudanian elements into the modern Sahelian zone suggests the appearance of a markedly dry season. The modern Sahelian semiarid conditions appeared abruptly at 2000 yr B.P.

Recent work on the middle Paleolithic at Bir Tarfawi, in the hyperarid Eastern Sahara (<1 mm of rain per annum), has yielded a rich faunal assemblage, including several thousand remains of fish, amphibians, reptiles, birds, and small mammals. They are derived from the sediments of two consecutive lakes dated by several techniques to about 135,000 yr B.P. Fifty-nine taxa have been identified and indicate that at times during the Last Interglaciation the area received at least 500 mm of rainfall as a result of the northward shift of the monsoon belt, and that, on several occasions, there may have been water connections between Bir Tarfawi and unidentified but permanent bodies of water elsewhere.