Greinar (Vísindafélag Íslendinga) - 01.01.1977, Síða 110

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sea origin, were taken into account, original red clay layers
might turn out to be more common than now held.
It very much depends on the mechanism of formation of the
deep sea water, whether very high concentrations of C02
occur in the atmosphere and in shallow, relatively closed seas
or not. (The Danish Cretaceous in question is thought to have
been deposited in a relatively closed sea). If the mechanism
stops for a few centuries, much of the C02 of the deep sea will
come up, even without change of temperature of the deep sea.
If it stops for millennia, the increase in temperature by ter-
restrial heat flow, will add to this effect. Finally, if the mechan-
ism works, by a 10°C warmer deep sea than at present, a new
C02 equilibrium is established, under which the deep sea con-
centration of C02 is slightly less than now, whereas the con-
centration is raised considerably in the air and in shallow
water.
In the warm shallow seas of Lower Tertiary and older times,
the dissolution of CaC03 would be a much faster process than
in the present icy cold depths of the deep sea, and red clay
layers might rather easily have been formed. The real main
reason for the scarcity of red clay layers in epicontinental
marine deposits would then be, that the red clay particles
were mixed with the rapidly deposited main material.
We have looked up a number of modern textbooks on geo-
logy, without finding a critical remark on the red clay. Only
Gignoux did not miss the point. For even before the measure-
ment of fossil deep sea temperatures this admirable thinker
in geology (30, p. 8—9) thought it worthwhile to make this
remark: “radiolarites . . . which we find in the Carboniferous
and in the Jurassic of the Alps, have been compared to the
radiolarian oozes of the present abyss. Such a comparison,
perhaps true for certain rocks, is certainly not true of all”.
We conclude that the “chalk with Brarudosphaera” is in
reality a shallow sea deposit, and that the cherts of the Eocene
horizons A and A” are, on the basis of (80) a shallow sea for-
mation — until the opposite could be proved.
That the continents have not been deep sea floors is evident