CHAPTER IX. 



CLIMATOLOGY OF THE LATE PALEOZOIC. 



The suggested causes of climatic change in geologic time which are now 

 considered as most probable are: the atmospheric theory (carbon-dioxide 

 content), the deformation theory, the sun-spot theory, and the solar-radiation 

 theory. The first of these is dismissed by Clements, in his Plant Succession,^ 

 with a brevity that seems hardly commensurate with the attention it has 

 received in other quarters. Whatever may have been the local cause of 

 climatic change in any limited locality, it is hardly to be supposed that the 

 change over such a large area as North America in the late Paleozoic was 

 not a part of a world-wide effect produced by some cosmic alteration in 

 which a change in the composition of the atmosphere may well have played 

 a large part. Certainly such a theory is far more applicable in its observ- 

 able data to a time so remote as the Permo-Carboniferous than any which 

 has to do with the intensity of solar radiation or the number of sun-spots. 

 Chamberlin has already shown the value of this theory and its applicability 

 to the great climatic cycle which culminated in the glaciation at the close 

 of the Paleozoic. 



Schuchert,^ in a brief critique of the atmospheric theory, states: 



"The glacial climates are irregular in their geological appearance, are variable 

 latitudinally, as is seen in the geographic distribution of the tillites between the 

 poles and the equatorial region, and finally, that they appear in geologic time as 

 if suddenly introduced. These difTerences do not seem to the writer to be condi- 

 tioned in the main by a greater or smaller amount of carbon dioxide in the 

 atmosphere, for if this gas is so strong a controlling factor, it would seem that at 

 least the glacial climates should not be of such quick development. On the other 

 hand, an enormous amount of carbon dioxide was consumed in the vast limestones 

 and coals of the Cretacic, with no glacial climate as a result;' though it must 

 be admitted that the great limestone and the vaster coal accumulations of the 

 Pennsylvanic were quickly followed by the Permic glaciation. Again, it may be 

 stated that the Pleistocene cold period was preceded in the Miocene and Pliocene 

 by far smaller areas of known accumulations of limestone and coal than during 

 either the Pennsylvanic or Cretacic, and yet a severe glacial climate followed." 



' Clements, F. E., Plant Succession, Carnegie Inst. Wash. Pub. No. 242, p. 320, 1916. 



2 Schuchert, Chas., in Elsworth Huntington, The Climatic Factor, Carnegie Inst. Wash. 

 Pub. No. 192, p. 289, 1914. 



' Professor Schuchert does not seem to take into consideration the fact that the formation 

 of normal calcium carbonate from the water-soluble acid calcium carbonate liberates an 

 amount of CO2 equal to that which it locks up. The reduction of CO2 in the air occurs 

 in times of land exposure and weathering rather than in times of limestone formation. 



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