FACTORS CONTROLLING C0 2 IN OCEANS AND ATMOSPHERE 43 



TABLE 4 



SEDIMENTATION RATE IN CARIBBEAN SEA 



carbonate accumulation rates. The best way to do this would be to make 

 radiocarbon measurements in great detail through the late glacial and the post- 

 glacial periods. A very rapid warming from full glacial to full interglacial 

 conditions occurred close to 11,000 years ago, but there really is not enough 

 data to reach any conclusions. Where data exist, the accumulation rate is about 

 twice as high for calcium carbonate in the late glacial as in the postglacial time. 

 The number of locations is so small that I am not sure we can safely generalize. 

 This is certainly something that should be done in more detail if we want to 

 understand oceanic paleochemistry. I have chosen to take the oxygen-isotope 

 curves for various deep-sea cores. Stratigraphic horizons and climatic horizons 

 that can be recognized in these cores have been dated well in at least one core so 

 that the age of these horizons is reasonably well fixed (Table 4). One such 

 horizon is dated 11 thousand years ago, one 75 thousand years ago, and another 

 is 127 thousand years. By taking the length of the intervals between these time 

 horizons and dividing by the elapsed time, we can get rates of deposition. Then 

 these rates can be broken down according to what the core is made of. When we 

 do it for a core from the Caribbean Sea, we find that the average calcium 

 carbonate accumulation rates during the warm part of the last interglacial period 

 (127,000 to 75,000 years ago) and the cold part of the last glacial period 

 (75,000 to 11,000 years ago) are roughly equal; the same is true for the 

 noncarbonate material that, in this case, is largely dust probably blown off the 

 continent or carried into the ocean by rivers. In this area the only difference 

 noted in components is that the calcium carbonate deposited during the cold 

 periods consists much more of plant calcium carbonate and less of animal 

 calcium carbonate than in the warm periods. There is an ecologic change in that 

 the plant population, the coccoliths, became a more important component and 

 the animal population, the forams, a less important component in cold times. It 

 is clear, then, that, if we want to do this study properly, we have to break this 

 down into individual ecologic elements and look at absolute rates of each. 



