900 



EMILIANI AND FLINT 



Table IV 

 Trend of Cenozoic Temperature Derived from Fossils 



[chap. 34 



fluctuation has yet been found. The beginning of the Pleistocene, therefore, 

 seems to mark the beginning of new things in the climatic history of the Cenozoic 

 Era. However, not only does the continental record give an inadequate indica- 

 tion of the number and amplitude of the Pleistocene fluctuations, it gives no 

 adequate concept of the duration of the several fluctuations, nor of the Pleisto- 

 cene time as a whole. For a better concept we must turn to the sediments 

 beneath the sea floor. 



E. Chronology 



Calibration of Pleistocene temperature changes by means of radio-isotopic 

 dates is a highly important aspect of Pleistocene stratigraphy. Thus far the only 

 radio -isotope that has yielded abundant results is i^C. Because of its short half 

 life, however, i^Q seems incapable of dating events more ancient than those of 

 the Weichsel glacial age of western European terminology. The greatest finite 

 i^C date published up to 1960 is about 64,000 years, as mentioned earlier. 

 Pertaining to a Dutch locality, it is believed to represent a short, relatively 

 warm interval following the first cold episode of the Weichsel glacial age 

 (Andersen, de Vries and Zagwijn, 1960). Finite dates between 45,000 and 50,000 

 years on North American materials have been published. These include part of 

 an interstadial in southern Ontario (de Vries and Dreimanis, 1960) and part of a 

 pluvial in southwestern California (Flint and Gale, 1958). As stated earlier, 

 radiocarbon dates of less than 30,000 years are numerous, and calibrate fairly 

 well climatic fluctuation embraced within the classical Wisconsin glacial of 

 North American terminology. 



Radioactive nuchdes of the ~^^J, 235U and 232i'h families have been used to 

 date deep-sea sediments back to about 200,000 years ago. This topic will be 

 discussed in a later section. 



Preliminary potassium-argon dates of materials significant for Pleistocene 

 chronology have been published (Evernden et al., 1957; Evernden, 1959; 

 Savage et al., 1960; Gentner and Zahringer, 1960; see also von Koenigswald, 

 1960). Because of the comparatively young age of Pleistocene materials, 



