152 C. SCHUCHERT THE KORTH AMERICAN GEOSYXCLIXES 



Page 



Development of the Cordilleran geosyncline 184 



General development 184 



Early Cordilleran geosyncline 185 



Rise of the Ancestral Rocky Mountains geanticline 186 



Late Cordilleran geosyncline 187 



Rise of the Cordilleran Intermontane geanticline 187 



Pacific sequent geosyncline 188 



Rocky Mountain sequent geosyncline 189 



Sonoran embayment 192 



Development of the Franklinian geosyncline 192 



Nature of mediterraneans compared with geosynclines 194 



General discussion 194 



Monogeosynclines 195 



Poly geosynclines 196 



Mesogeosynclines, or mediterraneans 197 



Oceans 199 



Continental foundering 200 



Rifts and graben 200 



Foundering of borderlands 201 



Foundering of continents 201 



Summation and conclusions 202 



IXTRODUCTIOX 



It was in 1903 that the writer printed his first paleogeographic map, 

 and seven years later that the Geological Society of America did him the 

 great honor of publishing fifty-two such maps of North America. Since 

 then, as stratigraphers have brought to light new data, today from Alaska 

 and tomorrow, perhaps, from Mexico, these maps have been altered to 

 record the new finds, and their number has increased mitil they now 

 represent one hundred and fifteen formations, beginning with the earliest 

 Cambrian. It is, therefore, a pleasure for the writer to bring before the 

 same Society that fourteen years ago listened to the initial presentation 

 of these Xorth American maps the broader conclusions that have crystal- 

 lized out of their study during the intervening years. 



The synthesis of my studies may be expressed in the words of another 

 presidential address, namely, that of Le Conte, given in 1897.^ Xearly 

 all of the processes of nature visible to us, he said, derive their forces 

 from the sun. Currents of air and water in their eternally recurring 

 cycles are a circulation driven l)y the sun. Plants derive their forces 

 directly, and those of animals indirectly through plants, from it. To this 



- Joseph Le Conte : Earth-crust movements and their causes. This Bulletin, vol. 8, 

 PI). 113-114. 



