Vertical movements of the earth's surface related to postglacial rebound, the eustatic rise in sea level and the elastic deformation of the globe due to melting of late glacial ice sheets are calculated for simplified models of the earth. The movements of the ground are large and require a reevaluation of what is meant by eustatic sea level change. This is defined here as an ocean-wide average change in mean sea level and its measurement requires widely distributed observations weighted according to the areas of oceans they represent. Evidence of a postglacial (6000-0 years BP) relative rise in sea level comes largely from regions affected by ground subsidence related to adjacent upward postglacial rebound movements in deglaciated areas: evidence for a relative fall of sea level comes from coastlines well removed from areas of rebound and which have been affected by a rise of the continental areas through compensation for the eustatic load. It is concluded: (1) no substantial eustatic change of sea level in the past 6,000 years is required to explain postglacial sea levels: (2) in late glacial time the eustatic curve is probably more like the sea level curve of Texas and Mexico than that of the Atlantic seaboard of the United States: (3) that the information of past sea levels, when sufficiently widespread, can provide an important method of studying the deep mechanical structure of the earth.

A decision appears imminent to define the lower boundary of the Holocene formally in terms of the European sequence, as comprising all or part of the interval between the end of the Bølling Interstade and the end of the Younger Dryas Stade (ca. 12,100–10,350 14C years BP). However, a lower boundary in this position can define the base of a European provincial stage only (the Flandrian). The interval contains no boundary suitable for global use, because temperature trends in many parts of the north polar and north temperate regions, including Europe, were then distorted by vast masses of melting ice inherited from Full-Glacial times. The last unquestionably worldwide major climatic event before the Hypsithermal Interval was the sharp cooling that has been inferred from glacier advances culminating about 14,500–14,000 14C years BP, and consequently the horizon at the transition from cooling to warming at the end of this episode should be defined as the base of the Holocene.

The lower Omo basin, southern Ethiopia, preserves formations of sedimentary and pyroclastic rocks which span a substantial range of later Cenozoic time. These formations are often extraordinarily rich in vertebrate fossils and have also afforded a series of molluscan assemblages from contexts radiometrically dated by K/Ar or 14C. The late Cenozoic molluscan fauna has been previously ill-known in this part of Africa and these assemblages provide a broad faunal zonation for the northern sector of the Eastern Rift valley. The five principal assemblages are here treated as faunal groupings, rather than as formal faunal zones. Three groupings are recognized for the Pliocene/Pleistocene time range, one grouping for the later Pleistocene and one grouping for the subrecent and present.

The distribution of planktonic foraminifera has been studied in 28 piston cores of Late Pleistocene age from the western Gulf of Mexico. Detailed correlation between the cores has been made possible by a high degree of similarity of frequency changes within several species; by coiling direction changes within Globorotalia truncatulinoides; by a datum level representing the near extinction of Globorotalia menardii flexuosa, and Globorotaloides hexagona at the end of the last interglacial; by three distinct volcanic ash horizons, and by calcium carbonate dissolution effects at distinct intervals. Almost all species demonstrate distinct frequency oscillations that are correlatable between cores. A high proportion of these are clearly related to paleoclimatic oscillations and reflect rapidly changing water-mass conditions within the Gulf of Mexico during the latest Pleistocene. No interval appears to have been represented by stable environmental conditions. Causes of frequency changes within several other species are not clearly related to inferred paleoenvironmental changes. High similarity of faunas exists at all times between the northwest and southwest Gulf of Mexico, reflecting similarity of water-mass conditions over a wide latitudinal range. High sedimentation rates, which average between 10 cm/1000 years and 30 cm/1000 years, have enabled a detailed paleoclimatic curve to be established for the last 200,000 years. Three interglacials and two glacials are recognized. Distinct foraminiferal assemblages have enabled definition of 18 zones most of which are related to paleoclimatic changes. Most intense coolings occurred at the end of the penultimate glaciation (zone W) and during the middle of the Wisconsin glaciation (zone Y).

The Gulf of Mexico curve is somewhat similar to those of other regions based on O18/O16 ratios, except that, despite close control, no intense cooling is apparent near the end of the last glaciation. The most sensitive warm water indicators are the G. menardii complex and Pulleniatina obliquiloculata; the most sensitive cooler water forms are Globorotalia inflata, and Globigerina falconensis. Several species have intermediate temperature tolerances. Much climatic information is lost when only the G. menardii complex is utilized in climatic studies, because these forms are essentially absent during glacial episodes. The most distinct faunal change associated with the Holocene warming does not coincide with the Z-Y boundary defined by the first consistent occurrence of G. menardii but occurs slightly earlier during the latest Wisconsin. The X zone, based on the consistent occurrence of the G. menardii group is of shorter duration in Gulf of Mexico cores than in cores from the central Caribbean Sea and the equatorial Atlantic Ocean.

Three major volcanic ash horizons coincide with climatic coolings; almost immediately preceding the last interglacial (135,000 years B.P.); towards the end of the last interglacial (end of zone X; 90–95,000 years B.P.), and in the earliest part of the last glaciation (75,000 years B.P.). A drastic reduction of G. menardii flexuosa and G. hexagona coincides with the middle ash horizon.

Canonical correlation analysis provides a means of reconstructing quantitative time series of past climatic variables during the last 15,000 years from fossil pollen spectra collected at three sites in the northern Midwest. This multivariate statistical technique was applied to a spatial array of modern pollen and climatic data in order to derive a set of mathematical transfer functions. These transform the fossil pollen spectra directly into quantitative estimates of past climatic values. The basic sequence of climatic events that is reconstructed is in general agreement with previous studies of postglacial climates in the Midwest, but quantitative estimates for certain of the variables, e.g., temperature and precipitation, are given for the first time.

Fossil pollen from three cores collected from lakes in Wisconsin and Minnesota allow a preliminary reconstruction of past east-west and north-south gradients of the climatic variables. Because changes in the circulation patterns in midlatitudes are the principal mechanism causing fluctuations in temperature and precipitation, past records of the atmospheric circulation are reconstructed along with records of temperature and rainfall. The time series derived show that the most pronounced climatic change indicated in Wisconsin and Minnesota occurred at the end of the Pleistocene (the beginning of the Holocene). This change is particularly evident in the climatic variables related to temperature, which rose ca. 3.3°C. A decrease in snowfall also occurred.

During the Holocene, the most marked change appears in the results from Kirchner Marsh, where the amount of dry western air began to increase and the precipitation to decrease about 9500 B.P. A reversal of these changes occurred about 5000 B.P. In contrast, relatively little change occurred among the reconstructed values from Wisconsin; a marked east-west precipitation gradient, therefore, developed in this region of the Midwest from 9500 to 5000 B.P.