Glacial Times

1985b). One of the most interesting observations is the existence of a world wide aragonite preservation spike which is expressed as a pteropod-rich layer at the end of the last glacial period, about 14,000 y BP. This event appears to have been followed by a drastic rise in the compensation level in the North Pacific Ocean and other areas about 12,500 y BP. The precise reasons for these observations are still a matter of debate. 

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The main deposits of freshwater diatomite were laid down in large lakes. Many of these deposits in the western United States formed during glacial times, when the local climate was wetter. Several tens of square kilometers in Nevada west of Tonopah are covered with diatomite as are other large areas in the Great Basin. 

Broecker, W. S. (1982). Ocean chemistry during glacial time. Geochim. Cosmochim. Acta 46,1689-1706. 

It is hard to see how the observed differences in atmospheric CO2 between late glacial and post-glacial times, let alone the likely variations over a few hundred years, could occur without the existence of some kind of feedback process between the ocean and the atmosphere. One such process could be changes in the level or character of biological productivity in the upper ocean waters. 

Broecker W. S., Ocean Chemistry during glacial time. Geochemica et Cosmochemica Acta , 46, 1689 (1982a). 

This last figure is far short of what Higuchi s model estimate calls for ( 2 Gt per annum). Nevertheless, if sustained it would be fully capable of yielding the 500 Gt of storage during post-glacial time. Moreover, withdrawals from other reservoirs must have been considerable. To... 

For all these studies, there is a necessity to establish the reservoir age for the glacial surface ocean. Several authors (Bard et al., 1994 Sikes et al., 2000 Waelbroeck et al., 2001 Siani et al., 2001) have attempted to do this and find puzzling older reservoir ages for glacial times. Clearly, more effort must go into such reconstructions. 

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