CHAP. 34] THE PLEISTOCElSrE RECORD 909 



seas, the weight percentage of the coarser carbonate fraction is in general 

 directly proportional to paleotemperatures (Emihani, 1955, 1958; Ericson and 

 Wolhn, 1956), while the weight percentage of the finer carbonate fraction 

 appears to be inversely proportional (Wangersky, 1958, 1959; Rosholt et ah, 

 1961). Accordingly, the total carbonate percentage may be variously related to 

 temperature, depending not only upon the amount of the non-carbonate 

 component (essentially clay), but also upon the relative amounts of the two 

 carbonate fractions because of their different temperature dependences (Ros- 

 holt et al., 1961). A direct relationship between total carbonate percentages and 

 paleotemperatures was observed in a short pilot core from the equatorial 

 Atlantic (Wiseman, 1954, 1959; Emiliani and Mayeda, 1961 ) and is also noticeable 

 in other Atlantic cores (compare Emiliani, 1955, with Olausson, 1960). Such a 

 relationship might be especiall}^ clear in deep-sea cores where post-depositional 

 solution has reduced the amount of the finer carbonate fraction (Wangersky, 

 1962). 



The direct relationship between weight percentages of the coarse carbonate 

 fraction and i^aleotemperatures should not be taken to indicate a greater 

 productivity of pelagic Foraminifera during warmer ages. In effect, chemical 

 and i^C analyses conducted at close stratigraphic intervals in an equatorial 

 Atlantic core showed that the sedimentation rates of the coarser carbonate 

 fraction, of the finer carbonate fraction and of the non-carbonate component 

 decreased markedly from the last glacial age to the postglacial, the decrease 

 having been greatest for the non-carbonate component, smallest for the coarser 

 carbonate fraction, and intermediate for the finer carbonate fraction (Broecker 

 et al., 1958). The different temperature dependence of the sedimentation rates 

 of the three components explains the observed relationships between their 

 weight percentages and paleotemperatures. 



A greater foraminiferal and coccolith productivity during glacial ages is 

 consistent with an overall greater biogenous activity in the oceans, brought 

 about by an increase in the vertical circulation in response to the greater 

 temperature gradient between equator and middle-high latitudes. The greater 

 rate of clay sedimentation in the Atlantic and adjacent basins during glacial 

 ages is explained not only by the faster oceanic circulation (which could carry 

 suspended material farther) but also by the fact that most of the glacial water 

 drained into the Atlantic and adjacent seas. In the equatorial and tropical 

 Pacific, on the other hand, the increase of suspended clay during glacial ages 

 was probably much smaller, explaining the apparent j)roductivity-controlled 

 inverse relationship between carbonate percentages and temperature in the 

 cores described by Arrhenius (1952). Generally, depending upon the relationship 

 among the changing rates of foraminiferal, coccolith, radiolarian, diatom and 

 clay sedimentation, the ratio of Foraminifera to the other components and the 

 ratio of carbonate to non-carbonate fraction can be either directly or inversely 

 proportional to temperature; they can remain constant if the above rates haj^pen 

 to change by the same amounts (cores of type II in Revelle et al., 1955, fig. 11) ; 

 or can vary independently of temperature (Wangersky, 1958). 



