Greinar (Vísindafélag Íslendinga) - 01.01.1977, Síða 109

107
(79, p. 408). But if deep ocean water in the Eocene and Oligo-
cene was much warmer, as indeed it was, the C02 equilibrium
in the air-ocean system was different. The bottom tempera-
ture in the mid-Pacific in the Oligocene (33 My), Miocene (22
My), and end of Pliocene (2 My) was found in (81) to have
been 10.4°, 7.0°, 2.2°C, respectively, whereas the present tem-
perature in the same places is 1.5°C. This great change in the
deep sea temperature is easily understood on the basis of the
mechanism of deep water formation, as it is explained in any
textbook of oceanography (for rapid orientation, see Icelandic
smnmary (82)).
To illustrate the importance of deep ocean temperatures
and the mechanism of deep water formation, the following
may be pointed out.
If today the cold deep ocean water was heated up by 10°C,
the saturation content of C02 would be lowered by about 1/3.
Of the 127X1012 tons of C02 in all forms in the present ocean
(as compared with 2.3X1012 tons in the atmosphere), such a
considerable part would have to move higher, if nothing else
happened, that it was manyfold (10-20 fold) the present
quantity in the atmosphere. If all this w'ent straight into the
air, it would necessarily soon cause higher concentration of
C02 in the uppermost layers of the sea, even if the surface
temperature was raised by 10°C. In other words, the con-
centration of C02 in shallow waters would be raised much
above the present one. Under such (nonequilibrium) condi-
tions, calcium carbonate could easily be dissolved in shallow
seas and “red” clay be formed; small positive fluctuations in
the C02-concentration in individual areas could occasionally
make conditions for organisms depending on CaCO:; unbearable,
and thus lead to the alternation of chalk and silicious deposits,
such as is typical in the Danish Cretaceous.
Red clay particles would be only a very small and mostly
unidentifiable admixture to the shallow sea sediments — as they
must also be today. The chance of pure red clay layers will at
all times have been greatest in deep sea, far from land. But if
the action of groundwater on such siliceous deposits of shallow