NEW GEOLOGIC TIME TABLE 605 



Permic cycle in America, and all the Coal Measures, including the Guada- 

 lupian, belong to one period. The determined chronology of these de- 

 posits, however, must be based upon European paleogeography of these 

 formations. It must therefore be understood that the dividing line on 

 the chart between the Pennsylvanic and the Permic is hypothetical, being- 

 based on a supposedly correct interpretation of the European standards 

 and of geologists. 



The highly emergent condition of North America at the close of the 

 Paleozoic continued into the Mesozoic, and endured for a long time. The 

 earliest and best marine records of the Triassic and Jurassic occur solely 

 along the Pacific, but late in the latter period much of eastern Mexico 

 sank beneath the Gulf. For these reasons, it appears that the chronology 

 is here again dependent on that of southern Europe. In a broad way,, 

 however, it is seen that the two curves on the chart record decided inun- 

 dations toward the close of the Triassic and Jurassic. Elsewhere in 

 America there are no marine deposits, and the interval between the Per- 

 mic and the Comanchic has long been well labeled the Jura-Trias. 



The Cretaceous is seen to contain two diastrophic cycles — the Co- 

 manchic and the Cretacic periods. Both are recognized by Chamberlin 

 and Salisbury in their "Geology." 



Tertiary or Neozoic time also divides into two diastrophic cycles agree- 

 ing with the recently proposed terms Eogenic and Neogenic (see De Lap- 

 parent's Traite). 



At the top of the chart has been placed the new classification, the divid- 

 ing lines being so drawn that these eras and periods may be easily com- 

 pared with the older scheme shown at the base of the chart. In conclu- 

 sion, the results here presented, contrasted with the previous classifica- 

 tion, are as follows : 



