918 EMILIANI AND FLINT [CHAP. 34 



the average 3°C in the equatorial and temperate Atlantic, and negligible in the 

 equatorial Pacific. 



Oxygen-isotopic analyses performed at close stratigraphic intervals on short 

 pilot cores from the Atlantic and the Caribbean generally failed to reveal 

 temperature oscillations related to the units of the last glaciation, with the 

 exception of a minor temperature reversal at 10-15 cm below the tops of the 

 cores possibly related to the Valders unit (Emiliani, 1955, figs. 7-10; Emiliani 

 and Mayeda, 1961). This failure is believed to result from sediment reworking 

 by bottom organisms, affecting a stratigraphic thickness of a few to several 

 centimeters. The implication is that temperature events spaced in time less 

 than a few thousand years from each other cannot be resolved by deep-sea sedi- 

 ments of normal Globigerina ooze facies. 



The transition between the last glacial age and the postglacial is strikingly 

 clear in the Arctic (Ericson and Wollin, 1959), in the Norwegian Sea (Holtedahl, 

 1959), and in the northern North Atlantic (Bramlette and Bradley, 1940), 

 where glacial-marine sediments deposited during the last glacial age and 

 containing some or much ice-rafted material pass into postglacial lutites with 

 abundant pelagic Foraminifera. It is also clear at lower latitudes. In the Gulf 

 of Mexico, for instance, a marked sedimentary change occurred 11,000 years ago 

 (Ewing et al., 1958), which implies reduction, by at least one third, in the capa- 

 city and competence of the Mississippi River (Emiliani, 1957). The abundance 

 of pelagic Foraminifera in the postglacial sections of cores from the Arctic 

 Ocean and the Norwegian Sea, mentioned above, apparently resulted from an 

 increase in productivity, following reduction or disappearance of sea-ice and/or 

 marked decrease of the terrigenous component. Broecker et al. (1960) have 

 marshalled evidence suggesting that most of the temperature increase marking 

 the transition between glacial and postglacial conditions occurred over a 

 period of only about 1500 years, close to 11,000 years ago. This sudden tem- 

 perature rise might have been caused by decrease of albedo following rapid 

 reduction or removal of sea-ice over the northern North Atlantic, Norwegian 

 Sea and other high-latitude areas (Emiliani and Geiss, 1959). 



The evidence offered by deep-sea sediments bears directly on the elaboration 

 of theories of glaciation. No theory of glaciation can be valid unless the facts 

 revealed by the study of deep-sea sediments are also taken into consideration 

 and explained. These facts have already made highly improbable some of the 

 glaciation theories proposed in the past. Thus, Simpson's theory (Simpson, 

 1934, 1940, 1957) that surface temperatures at low latitudes during glacial ages 

 were alternately lower and higher than during the intervening interglacials is 

 incompatible with the observed or inferred synchronism between glacial ages 

 and the temperature minima of the deep-sea cores from the Atlantic, the Carib- 

 bean and the Mediterranean. The groups of theories based on volcanism (cf. 

 Flint, 1957, pp. 504-505, and references therein) and on submarine tectonism 

 along the Greenland-Iceland-Scotland axis (Saks et al., 1955) are perhaps 

 incompatible with the apparent regularity of the temperature variations 

 suggested by the deep-sea cores. Theories based on variations of solar emission 



