CLIMATOLOGY OF THE LATE PALEOZOIC 241 



churia on the north to southeastern Africa on the south. Though the total 

 rainfall seems to have been heavy, probably over 50 inches, the climate was 

 seemingly marked by short seasons of dryness, but not of winter frost in any 

 region that has yet furnished fossil plants. The prevalence of great swamps in 

 all areas where littoral deposits are known, and in all continental fresh-water 

 basins, combats the idea of aridity. Though the Monongahela formation con- 

 tains some red beds in most countries, and though it may have covered short 

 intervals of dryness greater than at other times, it is improbable that desert 

 conditions prevailed in these regions at any time during the period. The existence 

 of well-defined climatic provinces at this time may well be doubted. 



"Permian Coal Measures. 



"The rapid changes in the flora of the Permian indicate corresponding climatic 

 changes, and these in turn suggest the differentiation of climatic zones, which at 

 an early stage are reflected in the conspicuous development of at least two great 

 climatic provinces. In northwestern Europe and eastern America, where coals 

 are not rare in the Permian, the climatic changes were less marked than in western 

 America, and particularly in southern Asia and the southern hemisphere, where 

 for a time, presumably in the early Permian, glacial conditions are known to 

 have occurred on a scale far greater than that of Pleistocene glaciation in the 

 northern hemisphere. Consequent to the climatic developments in the broad 

 regions of refrigeration in southern South America, South Africa, India, and 

 Australia, there was developed a peculiar flora, consisting of a limited number of 

 types, which is known as the Gangamopteris (so-called Glossopteris) flora. Al- 

 though it is practically certain that the extermination of the old mild-climate 

 cosmopolitan plant life from the Gangamopteris floral province was due to climatic 

 rigor, it is not, however, certain that the Gangamopteris flora itself lived under 

 conditions of actual climatic severity, though probably some of its types were 

 able to endure marked seasonal changes.^ Hence it does not necessarily follow 

 that the coal beds deposited in the Gangamopteris province during its occupation 

 by this flora were formed in a mean low temperature, though the prevailing climate 

 may have been colder than that in the north at the same time and may have 

 been marked by colder winters. The maintenance of the distinctions between 

 the Gangamopteris and the cosmopolitan floral provinces during the lower Permian 

 was perhaps due to topographic, marine, or other conditions causing isolation." 



In connection with this discussion of the climatic conditions of late 

 Paleozoic by David White, it is of interest to quote some remarks from an 

 earlier paper by the same author: 



"The Stephanian or Ouralian (including the GschelHan) of Europe dates 

 from the Hercynian uplift. Prior to this movement the sea had reached its 

 maximum extension in the coal fields of the northern hemisphere. The Hercynian 

 thrust caused its practical expulsion from the old synclines of western Europe 

 and the creation, especially to the southward, of new basins, mostly of fresh or 

 brackish water, to which were transferred the scenes of coal-formation. In 



^ See White, David, The Upper Paleozoic Floras, Their Succession and Range, Jour. Geol., 

 vol. 17, p. 320, 1909. 



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