182 SOUTHERN CALIFORNIA GEOLOGY 



westerly extending ranges of the San Luis Obispo 

 region. The Puente, San Gabriel and Sierra Madre 

 Faults bend westerly into the flexures of the Ventura 

 Ranges and become involved in the complex, and as yet 

 uninterpreted, structures of that region. 



The southeast end of the belt, as in the instance of 

 the north end of the San Jacinto Rift, apparently 

 also leads southward and alines with the north- 

 west-southeast faults of the north end of the Peninsula 

 Highland, between the Elsinore and San Jacinto Faults, 

 so that the outline of the belt as a whole is that of a 

 double bend as is shown in the following chapter. 



The big bends in the belt where its trends change 

 from north 45° west to north 65° west, and then back 

 to north 45° west again, are great departures from the 

 normal northwesterly continental trends and were ap- 

 parently produced by stresses in Pleistocene time. 



Much more could be said concerning the San 

 Andreas-Puente Belt of northwest structures, and still 

 more may be ascertained concerning it. When fully 

 interpreted these features will throw great light on 

 the geological history of California. 



THE GREAT BUCKLE 



There are two related instances of curvature in the 

 trends noticeable in the physiography which are excep- 

 tions from the normal rectilinear plan and the struc- 

 ture pattern. The first of these is that of the bends 

 of the San Andreas-Puente Belt just described and the 

 second that of the Ventura Ranges, presently to be 

 described. The fact of the matter is, that the two 

 instances mentioned are related, and, together with the 

 east-west structures of the Transverse Belt, are each 

 expressions of parts of the structure of a great buckle 



