184 C. SCHUCHERT THE XORTH AMERICAN GEOSYXCLIXES 



Tlie whole relation of subsequent sedimentation was changed by the 

 orogeny of late Penns3^lYanian times and by another movement in eastern 

 Colorado and Xew Mexico. This latter area of mountain-making is de- 

 scribed by Lee in one of the papers of this S}Tnposium, under the name 

 of "Ancestral Southern Eocky Mountains/' To the east of the latter lay 

 the Permian shallow-water seas of Texas, Oklahoma, and Kansas, laying 

 down great sheets of elastics derived from the west, along ^vith the most 

 extensive deposits in Xorth America of sodium chloride and gypsum. 

 On the other hand, the Arbuckle and Massern mountains remained as 

 land athwart the late Pennsylvanian and Permian seas, but the AYichitas 

 were tinally completely submerged by Permian sediments. In Nebraska, 

 Kansas, and Texas, however, the Pennsylvanian seas continued unbroken 

 into Permian time. 



From the previous statements we see that the Ouachita emba}TQent 

 and its positive borderland, Llanoria, are as striking a geologic element 

 in the evolution of the Xorth American continent as are the Appalachian 

 geosyncline and its borderland, Appalachia. The only marked difference 

 is the lesser areal extent and the less complete marine record of the south- 

 ern elements. On the other hand, the positive crustal movements in both 

 areas appear to be harmonious and of the same orogenic realm. 



Develop^^iext of the Cordilleuax Geosyxcltxe 



(.See Maps, Figures 4 to IT) 

 GENERAL DEVELOPMEXT 



The longest and widest, and by far the oldest and longest-continuing 

 seaway is the one long known as the Cordilleran geosyncline. During 

 the Paleozoic it extended from the Arctic Ocean southward through what 

 is now the mountainous region of western Xorth America into north- 

 Avestern Mexico, a distance of 3,000 miles. In Canada the width of this 

 seaway is usually several hundred miles, while in the United States it is 

 many hundreds of miles wide and at times attains a breadth of more 

 than 1,000 miles. The eastern shores of this vast geosyncline and its 

 marine extensions are the Canadian shield and its southern prolongation, 

 Siouia, while its oceanward borderland is Cascadia, to the west of which 

 is the Pacific Ocean. 



^yith the close of the Devonian the Cordilleran seas begin to restrict 

 and their eastern shores in the far north begin to move westward. This 

 change is further accentuated in the late Pennsjdvanian and Triassic, so 

 that by the end of Jurassic time there had arisen, almost out of the very 

 center and along the entire length of this geosyncline, the very extensive 



