CHAP. 34] 



THE PLEISTOCENE RECORD 



911 



quartz particles than the underlying Tertiary sediments (Rex and Goldberg, 

 1958). The low temperature of the Pacific bottom water late in Pliocene time 

 suggests that Antarctica was already fully glaciated, with ice extending to the 

 Antarctic shore. 



Oxygen-isotopic analysis of pelagic Foraminifera from equatorial and sub- 

 tropical xltlantic cores of Middle Oligocene and Lower-Middle Miocene age 

 showed that the ocean-surface temperatures remained rather uniform during the 

 time intervals represented by these cores (perhaps 100,000 years for the Middle 

 Ohgocene section and perhaps up to 300,000 years for the Lower-Middle 

 Miocene sections). Only random fluctuations, mostly within 2°C, are apparent 

 (Emiliani, 1956). 



Only one core, which probably represents the whole Pleistocene Epoch and 

 penetrates well into the Pliocene, has been analyzed so far by the oxygen- 

 isotopic method. This core, no. 58 of the Swedish Deep-Sea Expedition of 



100' 



200 



300 



400 500 



DEPTH BELOW TOP (CM) 



600 



700 



800 



900 



1000 



Fig. 4. Plio-Pleistocene temperature decrease of surface water of the eastern equatorial 

 Pacific as shown by oxygen-isotopic analysis of Pulleniatina obliqv iloculata (curve a) 

 and Oloborotalia menardii tumida (curve b) from core 58 of the Swedish Deep-Sea 

 Expedition, 1947-1948. (From Emiliani, 1955.) 



1947-1948, raised in the eastern equatorial Pacific, shows an appreciable 

 temperature decrease (about 3°C) from the bottom up to the middle portion of 

 the core, followed by small temperature oscillations in the uj)per half (Fig. 4). 

 These oscillations, however, do not offer a clear picture of climatic changes 

 during the Pleistocene because of the relatively small value of the secular tem- 

 perature change in the equatorial Pacific, because of the deeper habitats of the 

 foraminiferal species available for isotopic analysis, and because of the local 

 pattern of vertical circulation of the surface water (Emiliani, 1955). 



The Pleistocene temperature record is far clearer in cores from the Atlantic 

 and adjacent seas than in Pacific core 58, but unfortunately it is as yet far 

 shorter stratigraphically. In fact, the stratigraphically longest core so far 

 analyzed (Emiliani, 1955) is Lamont core A172-6 from the Venezuelan Basin of 

 the Caribbean, extending back in time an estimated 300,000 years. 



Micro^Daleontological work on this and many other cores from the equatorial, 

 tropical and temperate Atlantic, the Caribbean, the Gulf of Mexico and the 

 Mediterranean (Bramlette and Bradley, 1940; Cushman, 1941; Cushman and 

 Henbest, 1940; Ericson, 1953; Ericson et al., 1955; Ericson and WolHn, 1956; 



