892 EMILIANI AND FLINT [CHAP. 34 



bodies of oiitwash sediment deposited beyond the glaciated regions by streams 

 of melt-water. A grand example is the Mississii)i)i River valley, within which 

 outwash sediments are traced downstream through hundreds of miles beyond 

 the limit reached by glacier ice. At a further remove, the terms glacial and inter- 

 glacial are applied to the much broader areas of loess (wind-blown silt) secon- 

 darily derived, in large part from bodies of outwash. Like the glacial drift, the 

 loess can be subdivided into stratigraphic units, separated by ancient soils and 

 more rarely by distinctive non-eolian sediments. 



Outwash sediments and loess, indirectly of glacial origin, are developed 

 mainly in the humid and subhumid regions of middle latitudes. In arid regions 

 of middle and low latitudes are found other kinds of evidence of climatic fluctua- 

 tion. Conspicuous among these are beaches and floor sediments of former Pleis- 

 tocene lakes, where under existing climates the sites have only shrunken, saline 

 lakes or are completely dry. In western United States, mainly in structural 

 basins, about 120 former lakes have been identified thus far, the largest having 

 an implied area of more than 50,000 km^ and a maximum depth of more than 

 300 m. Similar groups of former lakes are known in Asia, Africa, South America 

 and Australia. Such features constitute one of the chief bases for the concept of 

 pluvial and interpluvial chmates. According to this concej^t the lakes imply a 

 combination of greater precipitation and reduced evaporation, compared with 

 today's climate. As early as 1865 the inferred pluvial climates were thought to 

 be contemporaneous with the glacial climates of other regions. In some former 

 lakes two or more alternations of climate are recorded in the stratigraphy. At 

 certain localities a contemporaneous or near-contemporaneous relationship be- 

 tween lake beaches and glacial drift in adjacent mountain valleys has been 

 demonstrated. In cores from a former lake in California, the last high-water 

 phase has been shown by i^C dating to have been contemporary with the 

 last major glacial maximum in central United States (Flint and Gale, 1958). 

 Although similar data are greatly needed from other continents, it seems at 

 present reasonably likely that glacial and pluvial episodes were contem- 

 poraneous, 



B. Representative Sequences 



All stratigraphic columns of regional application are imperfect in that they 

 are broad generalizations from the known evidence. Some of the most interest- 

 ing, because best supported by detailed information, are discussed below. 



Probably the best-supjDorted continental sequence is that of the Netherlands- 

 eastern England region. In that region the column extends from the top of the 

 Pliocene into the upper part of the Pleistocene, with fewer interruptions than 

 in most other regions (Table I). The pre-Cromerian sequence is based in the 

 Netherlands on fossil pollen, which records distinct fluctuations of air tempera- 

 tures, and in part on terrestrial vertebrates. In eastern England the same part 

 of the sequence is based mainly on marine invertebrates, again with temperature 

 implications. In both areas the Cromerian and post-Cromerian sequence is 



