204 C. SCHUCHEET THE XORTII AMERICAN GEOSYNCLINES 



it divided into two northwesterly-southeasterly trending lands, a northern 

 mass, the Charlotte borderland, which endured, though greatly reduced 

 in area, into early Cenozoic time, and a southern one, the Californian 

 borderland, which suffered marked orogeny throughout Mesozoic and 

 Cenozoic times. At present, much of Cascadia is faulted into the great 

 depths of the Pacific. 



AYe have now recounted the most positive and the least positive areas 

 of the North American continent, and next we must bring together a 

 brief statement as to the various geanticlines (see map, figure 2). The 

 oldest of these is the New Brunswick geanticline, dividing Acadia into- 

 two geosynclinals. This periodically rising axis had its origin at the 

 close of the Proterozoic, and late in Devonian time it became so positive 

 and so beset with active volcanoes as to blot out the seas on either side 

 of it. Even though the earliest Carboniferous seas partially reentered 

 between these mountains and formed the Northumherland embay ment, 

 yet this orogenic province continued positive till the close of Pennsyl- 

 vanian time. 



The next geanticline to appear arose out of the medial area of the 

 greater Mississippian sea and divided it into two basins after early 

 Silurian times. This was the well known Cincinnati geanticline. It 

 was at no time during the later Paleozoic a very positive axis of uplift. 



During the later Pennsylvanian, there was much orogeny throughout 

 the borderlands of eastern North America, and to a far more limited ex- 

 tent in Texas and Oklahoma. In keeping with this mountain-making, 

 the western area of neutral Siouia also began to rise vertically. This is- 

 the Ancestral Rocky Mountains geanticline, whose rising finally com- 

 pletely blotted out in the area of Siouia the later Paleozoic seas. The 

 geanticline was, however, reduced to sealevel before the Upper Jurassic, 

 since the seas of this time and those of the Cretaceous again completely 

 transgressed all of it. This old structure was reelevated by the Laramide 

 orogeny and by the epeirogeny of late Cenozoic times. 



The most interesting of all the positive areas is the well known Cor- 

 dilleran Intermontane geanticline (see maps, figures 2 and 16). This 

 made its appearance through warping late in the Triassic as a low arch 

 throughout the States of Arizona, Nevada, Utah, and Idaho, and then in 

 the earlier Jurassic the arching was continued northward into British 

 Columbia. It was completed by the Nevadan orogeny of late Jurassie 

 time, which established it during the Cretaceous throughout the extent 

 of North America. It was a geanticline of the first order, and was a. 

 vigorously rising mass during the Cretaceous. During its growth it 

 blotted out much of the Paleozoic Cordilleran seas, and along its eastero 



