66 SOUTHERN CALIFORNIA GEOLOGY 



end of the former ice sheets of the Glacial epochs (geo- 

 logically the Quaternary Period, or "Age of Man") and 

 crosses the northern part of the United States as an 

 irregular line well shown in most of our geographies. 



THE TRANSCONTINENTAL LINE OF CROSS 

 STRUCTURES 



Most geologists have been content to consider that 

 California is divided, as stated, into the Pacific and 

 desert sides by highland barriers, and that all the 

 lineaments of its surfece have been considered to have 

 the north-south parallelism. But this supposed sym- 

 metry is not persistent, for it is abruptly broken across 

 by the occurrences of highlands, valleys, and master 

 faults which trend in an east-west direction. These 

 highlands and valleys constitute the Great Transverse 

 Structural Belt, recently defined by the writer.^ 



This line approximately follows our southern 

 boundary. It comprises a series of physiographic and 

 structural features, not necessarily continuous, al- 

 though related, which consist of master fault l ines , 

 elongated mountain folds, plateau scarps, synclinal val- 

 leys and marine cliffs, which succeed one another across 

 the continent in an east-west direction (a little 

 south of east) from the westernmost of our Channel 

 Islands to the east end of the Virgin Islands of the 

 West Indies. More especially it extends from the west 

 tip of the Channel Islands of California into Arizona 

 at the Colorado River. 



Beyond the Colorado River its lineaments continue 

 eastward across Arizona, New Mexico, and part of 

 Texas as master fault hnes near the south ends of 



'In a paper read before the Cordilleran Section of the Geological Society 

 of America, Los Angeles, 1926. 



