126 SOUTHERN CALIFORNIA GEOLOGY 



Although the data are still somewhat indefinite, it 

 may be stated that a portion of a generalized north- 

 south cross-section of the Los Angeles Region conveys 

 the suggestion that there has been a succession of fault 

 and folding movements between the mountains and 

 the sea in Pleistocene time, at least until the Domin- 

 guez Range is crossed. Beginning at the north with 

 the block between San Gabriel and Sierra Madre fault, 

 one encounters a succession of newer and lower ranges 

 as he goes southward each of which has a steeper slope 

 and a fault scarp on the seaward side. It also seems 

 evident that with the initiation of a new range to the 

 seaward the older blocks to the interiorward in this 

 succession collectively received an additional upward 

 impulse. There are complications in this cross-sec- 

 tion as the results of the cutting out of older trends 

 and folds by newer movements, which render this 

 deduction still somewhat indefinite and tentative. 



Movement is also often renewed in later geologic 

 epochs along structural lines which were made in pre- 

 vious ones. Examples of this on a broad scale are fre- 

 quent. One is the apparent fact that all of the faults 

 and folds of the Transverse Belt correspond in posi- 

 tion and trend to the site of a persistent, ancient sea- 

 way, or geosyncline, of Paleozic times (called the "Son- 

 oric Depression" by Dr. Charles Schuchert). 

 THE BELTED GROUPS OF FAULTS 



Studies and analyses of the structure patterns shows 

 several wide zones of parellel faults, which extend 

 across continental expanses in great, belt-like assem- 

 blages, any one of which may be several hundreds of 

 miles in length and many miles in width. Furthermore 

 it will be evident that some of these belted groups of 



