THE PERMIAN PERIOD 183 



Physical History 



During the Period. — Combining the above descriptions of 

 rock distribution and characters with an examination of the 

 paleogeographic map, the physical history of North America 

 during the Permian may be readily comprehended. True marine 

 conditions are definitely known to have prevailed during the whole 

 period only in southern Alaska, northern California, Utah, and 

 possibly southern New Mexico. The visible Permian strata in 

 most of the other western states are of such character as to indicate 

 deposition in great salt lakes or more or less cut off basins or arms 

 of the sea. Conditions of aridity must have prevailed. Inter- 

 bedded with these deposits, however, in some areas are marine 

 strata, thus proving at least occasional incursions of the sea. In 

 Kansas the character of the rocks shows the prevalence of marine 

 waters during much of the earlier Permian. The best evidence 

 seems to indicate that these interior basins had their connections 

 with the sea across the Great Basin region (as indicated by true 

 marine strata in the Wasatch Mountains) on one side, and through 

 southern New Mexico and northern Mexico on the other, with an 

 island between as shown on the map (Fig. 111). 



The rocks of the northern Appalachian district clearly prove 

 a continuation of the Coal Measures conditions, that is great 

 fresh-water lagoons or basins, with occasional sea incursions. 



The Nova Scotia and New Brunswick Permian rocks are also 

 chiefly of continental origin, suggesting conditions of deposition 

 similar to those in the western states, except that salt and gypsum 

 are practically absent. 



Close of the Permian (Appalachian Revolution) — The 

 Paleozoic era was brought to a close by one of the most profound 

 physical disturbances in the history of North America. It has 

 been called the Appalachian Revolution because at that time the 

 Appalachian Mountain Range was born out of the sea by upheaval 

 and folding of the strata. Perhaps it would be better to say that 

 the revolution reached its climax at about the close of the Paleozoic 

 because the evidence is clear that the upward movement began at 

 least as early as the close of the Mississippian and slowly increased 

 to the close of the era. Since Permian strata are involved in 

 the folding along the western side of the Appalachians, we know 



